Document and Entity Information Document - USD ($)	12 Months Ended
Document and Entity Information Document - USD ($)	Dec. 31, 2018	Jan. 31, 2019	Jun. 29, 2018
Entity Information [Line Items]
Entity Registrant Name	ALEXION PHARMACEUTICALS, INC.
Entity Central Index Key	0000899866
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		223,469,381
Entity Well-known Seasoned Issuer	Yes
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 26,514,235,288

Consolidated Balance Sheets Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and cash equivalents	$ 1,365.5	$ 584.4
Marketable securities	198.3	889.7
Trade accounts receivable, net	922.3	726.5
Inventories	472.5	460.4
Prepaid expenses and other current assets	426.4	292.9
Total current assets	3,385.0	2,953.9
Property, plant and equipment, net	1,471.5	1,325.4
Intangible assets, net	3,641.3	3,954.4
Goodwill	5,037.4	5,037.4
Other assets	396.7	312.2
Total assets	13,931.9	13,583.3
Liabilities and Equity [Abstract]
Accounts Payable and Accrued Liabilities, Current	698.2	710.2
Revolving credit facility	250.0	0.0
Current portion of long-term debt	93.8	167.4
Current portion of contingent consideration	97.6	0.0
Other current liabilities	34.4	74.9
Total current liabilities	1,174.0	952.5
Long-term debt, less current portion	2,501.7	2,720.7
Contingent consideration	183.2	168.9
Facility lease obligations	361.0	342.9
Deferred tax liabilities	391.1	365.0
Other liabilities	155.6	140.2
Total liabilities	4,766.6	4,690.2
Stockholders' Equity Attributable to Parent [Abstract]
Commitments and contingencies (Note 11)
Common stock, $.0001 par value; 290.0 shares authorized; 236.2 and 234.3 shares issued at 2018 and 2017, respectively	0.0	0.0
Additional paid-in capital	8,539.1	8,290.3
Treasury stock, at cost, 12.7 and 12.0 shares at 2018 and 2017, respectively	(1,689.9)	(1,604.9)
Accumulated other comprehensive loss	(9.7)	(34.4)
Retained earnings	2,325.8	2,242.1
Total stockholders' equity	9,165.3	8,893.1
Total liabilities and stockholders' equity	$ 13,931.9	$ 13,583.3

Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	290.0	290.0
Common stock, shares issued	236.2	234.3
Treasury Stock, Shares	12.7	12.0

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total revenues	$ 4,131.2	$ 3,551.1	$ 3,084.1
Cost of sales:
Cost of sales	374.3	454.2	258.3
Operating expenses:
Research and development	730.4	878.4	757.2
Selling, general and administrative	1,111.8	1,094.4	953.0
Acquired in-process research and development	1,183.0	0.0	0.0
Amortization of purchased intangible assets	320.1	320.1	322.2
Change in fair value of contingent consideration	116.5	41.0	35.7
Acquisition-related costs	0.0	0.0	2.3
Restructuring expenses	25.5	104.6	3.0
Impairment of intangible assets	0.0	31.0	85.0
Total operating expenses	3,487.3	2,469.5	2,158.4
Operating income	269.6	627.4	667.4
Other income and expense:
Investment income	65.3	18.5	10.9
Interest expense	(98.2)	(98.4)	(96.9)
Other income and (expense)	5.5	0.3	(5.2)
Income before income taxes	242.2	547.8	576.2
Income tax expense	164.6	104.5	176.8
Net income	$ 77.6	$ 443.3	$ 399.4
Earnings per common share
Basic (in dollars per share)	$ 0.35	$ 1.98	$ 1.78
Diluted (in dollars per share)	$ 0.35	$ 1.97	$ 1.76
Shares used in computing earnings per common share
Basic (in shares)	222.7	223.9	224.3
Diluted (in shares)	224.5	225.4	226.3
Net product sales
Total revenues	$ 4,130.1	$ 3,549.5	$ 3,081.7
Other revenue
Total revenues	$ 1.1	$ 1.6	$ 2.4

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 77.6	$ 443.3	$ 399.4
Foreign currency translation	(0.5)	8.4	(4.3)
Unrealized (losses) gains on debt securities	(0.5)	0.6	0.4
Unrealized gains on pension obligation	2.2	1.9	2.9
Unrealized gains (losses) on hedging activities, net of tax of $7.3, $(59.0) and $(0.2), respectively	23.5	(105.8)	(0.8)
Other comprehensive income (loss), net of tax	24.7	(94.9)	(1.8)
Comprehensive income	$ 102.3	$ 348.4	$ 397.6

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Statement of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balances, common shares at Dec. 31, 2015		230.5
Balances, treasury shares at Dec. 31, 2015				4.9
Balances, value at Dec. 31, 2015	$ 8,258.6	$ 0.0	$ 7,726.6	$ (710.7)	$ 62.3	$ 1,180.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares				3.1
Repurchase of common stock value	(430.6)			$ (430.6)
Issuance of common stock from exercise of options, shares		0.6
Issuance of common stock from exercise of options, value	37.1		37.1
Issuance of restricted common stock, shares		0.8
Share-based compensation expense, value	193.3		193.3
Net income	399.4					399.4
Other comprehensive income (loss)	(1.8)				(1.8)
Balances, common shares at Dec. 31, 2016		231.9
Balances, treasury shares at Dec. 31, 2016				8.0
Balances, value at Dec. 31, 2016	8,693.8	$ 0.0	7,957.0	$ (1,141.3)	60.5	1,817.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new guidance, value	237.8					237.8
Repurchase of common stock, shares		0.0		4.0
Repurchase of common stock value	(463.6)			$ (463.6)
Issuance of common stock from exercise of options, shares		1.3
Issuance of common stock from exercise of options, value	85.9		85.9
Issuance of restricted common stock, shares		1.1
Share-based compensation expense, value	247.4		247.4
Net income	443.3					443.3
Other comprehensive income (loss)	$ (94.9)				(94.9)
Balances, common shares at Dec. 31, 2017		234.3
Balances, treasury shares at Dec. 31, 2017	12.0			12.0
Balances, value at Dec. 31, 2017	$ 8,893.1	$ 0.0	8,290.3	$ (1,604.9)	(34.4)	2,242.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new guidance, value	(18.8)					(18.8)
Repurchase of common stock, shares				0.7
Repurchase of common stock value	$ (85.0)			$ (85.0)
Issuance of common stock from exercise of options, shares	0.5	0.6
Issuance of common stock from exercise of options, value	$ 47.6		47.6
Issuance of restricted common stock, shares		1.3
Stock Issued During Period, Value, Restricted Stock Award, Gross	(0.3)		(0.3)
Share-based compensation expense, value	201.5		201.5
Net income	77.6					77.6
Other comprehensive income (loss)	$ 24.7				24.7
Balances, common shares at Dec. 31, 2018		236.2
Balances, treasury shares at Dec. 31, 2018	12.7			12.7
Balances, value at Dec. 31, 2018	$ 9,165.3	$ 0.0	$ 8,539.1	$ (1,689.9)	$ (9.7)	2,325.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new guidance, value	$ 6.1					$ 6.1

Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
Statement of Cash Flows - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 77.6	$ 443.3	$ 399.4
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	405.3	496.7	396.4
Impairment of assets	13.5	118.8	85.0
Change in fair value of contingent consideration	116.5	41.0	35.7
Payments of contingent consideration	0.0	(18.0)	0.0
Share-based compensation expense	203.0	243.1	192.3
Non-cash expense for acquired IPR&D	64.6	0.0	0.0
Deferred taxes	32.9	(45.9)	104.3
Other income and (expense)	4.8	(9.4)	6.9
Unrealized (gain) loss on forward contracts	(15.8)	11.1	(3.6)
Unrealized gain on equity investments	(40.2)	0.0	0.0
Other	(2.0)	5.4	6.5
Changes in operating assets and liabilities, excluding the effect of acquisitions:
Accounts receivable	(208.8)	(55.2)	(122.1)
Inventories	(14.7)	(88.2)	(83.8)
Prepaid expenses and other assets	(155.6)	(137.2)	(97.5)
Accounts payable, accrued expenses and other liabilities	(55.1)	110.1	166.8
Net cash provided by operating activities	426.0	1,115.6	1,086.3
Cash flows from investing activities:
Purchases of available-for-sale debt securities	(782.7)	(1,648.8)	(667.1)
Proceeds from maturity or sale of available-for-sale debt securities	1,473.5	1,089.9	717.8
Purchases of mutual funds related to nonqualified deferred compensation plan	(12.1)	(9.9)	(8.5)
Proceeds from sale of mutual funds related to nonqualified deferred compensation plan	12.3	7.7	4.0
Purchases of property, plant and equipment	(213.0)	(357.3)	(332.7)
Payments to Acquire Other Investments	(10.3)	0.0	0.0
Other	2.8	0.1	(1.1)
Net cash provided by (used in) investing activities	470.5	(918.3)	(287.6)
Cash flows from financing activities:
Proceeds from revolving credit facility	250.0	0.0	0.0
Payments on term loan	(293.8)	(175.0)	(375.0)
Repurchase of common stock	(85.0)	(463.6)	(430.6)
Net proceeds from issuance of stock under share-based compensation arrangements	47.3	85.9	37.1
Payments of contingent consideration	0.0	(7.0)	(60.0)
Repayment of development-related grants	0.0	(26.0)	0.0
Other	(20.9)	(10.9)	(7.7)
Net cash used in financing activities	(102.4)	(596.6)	(836.2)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(11.2)	17.7	(6.6)
Net change in cash and cash equivalents and restricted cash	782.9	(381.6)	(44.1)
Cash and cash equivalents and restricted cash at beginning of period	584.4	966.0	1,010.1
Cash and cash equivalents and restricted cash	1,367.3	584.4	966.0
Supplemental disclosures
Cash paid for interest (net of amounts capitalized)	90.9	95.3	79.6
Cash paid for income taxes	163.9	162.1	37.7
Supplemental cash flow disclosures from investing and financing activities:
Capitalization of construction costs related to facility lease obligations	44.8	121.8	103.1
Accrued expenses for purchases of property, plant and equipment and intangible assets	$ 21.4	$ 34.7	$ 23.5

Business Overview and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Business Overview and Summary of Significant Accounting Policies [Abstract]

Business Overview and Summary of Significant Accounting Policies

Business

Alexion Pharmaceuticals, Inc. (Alexion, the Company, we, our or us) is a global biopharmaceutical company focused on serving patients and families affected by rare diseases through the innovation, development and commercialization of life-changing therapies.

We are the global leader in complement inhibition and have developed and commercialize the only two approved complement inhibitors to treat patients with paroxysmal nocturnal hemoglobinuria (PNH), as well as the first and only approved complement inhibitor to treat atypical hemolytic uremic syndrome (aHUS) and anti-acetylcholine receptor (AchR) antibody-positive generalized myasthenia gravis (gMG). In addition, Alexion has two highly innovative enzyme replacement therapies for patients with life-threatening and ultra-rare metabolic disorders, hypophosphatasia (HPP) and lysosomal acid lipase deficiency (LAL-D).

As the leader in complement biology for over 20 years, Alexion focuses its research efforts on novel molecules and targets in the complement cascade, and its development efforts on the core therapeutic areas of hematology, nephrology, neurology, and metabolic disorders. We were incorporated in 1992 under the laws of the State of Delaware.

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Alexion and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. For each of our business combinations, all of the assets acquired and liabilities assumed were recorded at their respective fair values as of the date of acquisition, and their results of operations are included in the consolidated financial statements from the date of acquisition.

Dividend Policy

We have never paid a cash dividend on shares of our stock. We currently intend to retain our earnings to finance future operations and do not anticipate paying any cash dividends on our stock in the foreseeable future.

Critical Accounting Estimates

The preparation of our consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the U.S., requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosure of contingent assets and liabilities in our financial statements. We believe the most complex judgments result primarily from the need to make estimates about the effects of matters that are inherently uncertain and are significant to our consolidated financial statements. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. We evaluate our estimates, judgments and assumptions on an ongoing basis. Actual results may differ from these estimates under different assumptions or conditions.

The most significant areas involving estimates, judgments and assumptions used in the preparation of our consolidated financial statements are as follows:


•	Revenue recognition;


•	Contingent liabilities;


•	Inventories;


•	Share-based compensation;


•	Valuation of goodwill, acquired intangible assets and in-process research and development (IPR&D);


•	Valuation of contingent consideration; and


•	Income taxes.

Foreign Currency Translation

The financial statements of our subsidiaries with functional currencies other than the U.S. dollar are translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates for operating results. Translation gains and losses are included in accumulated other comprehensive income (loss), net of tax, in stockholders’ equity. Foreign currency transaction gains and losses are included in the results of operations in other income and expense.

Cash and Cash Equivalents

Cash and cash equivalents are stated at cost plus accrued interest, which approximates fair value, and include short-term highly liquid investments with original maturities of three months or less. As of December 31, 2018 and 2017, cash equivalents were comprised of money market funds, reverse repurchase agreements, and other debt securities with maturities less than 90 days from the date of purchase.

Fair Value of Financial Instruments

The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, accounts receivable, other assets, accounts payable, accrued expenses and other liabilities approximate fair value due to their short-term maturities. Our marketable securities are valued based upon pricing of securities with similar investment characteristics and holdings. Our mutual fund investments and equity securities are valued based on quoted market prices in active markets with no valuation adjustment. Investments in equity securities of publicly traded companies which are subject to holding period restrictions are carried at fair value using an option pricing valuation model and observable market inputs such as the historical volatility of similar companies and risk-free interest rates. Our derivative financial instruments are measured at fair value using observable market inputs such as forward rates, interest rates, our own credit risk and our counterparties’ credit risks. Our debt obligations are carried at historical cost, which approximates fair value. Our contingent consideration liabilities related to our acquisitions are valued based on various estimates, including probability of success, estimated revenues, discount rates and amount of time until the conditions of the milestone payments are met.

Marketable Securities

We invest our excess cash balances in marketable securities of highly rated financial institutions and investment-grade debt instruments. We seek to diversify our investments and limit the amount of investment concentrations for individual institutions, maturities and investment types. We classify marketable debt securities as available-for-sale and, accordingly, record such securities at fair value. We classify these securities as current assets as these investments are intended to be available to the Company for use in funding current operations.

Unrealized gains and losses on our marketable debt securities that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If any adjustment to fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our consolidated statement of operations. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive income (loss).

We sponsor a nonqualified deferred compensation plan which allows certain highly-compensated employees to elect to defer income to future periods. Participants in the plan earn a return on their deferrals based on several investments options, which mirror returns on underlying mutual fund investments. We choose to invest in the underlying mutual fund investments to offset the liability associated with our nonqualified deferred compensation plan. These mutual fund investments are valued at net asset value per share and are carried at fair value with gains and losses included in investment income. The changes in the underlying liability to the employee are recorded in operating expenses.

Accounts Receivable

Our standard credit terms vary based on the country of sale and range from 30 to 120 days and all arrangements are payable within one year of the transfer of the product. Our consolidated average days’ sales outstanding ranges from 60 to 70 days. We evaluate the creditworthiness of customers on a regular basis. The length of time from sale to receipt of payment in certain countries exceeds our credit terms. In countries in which collections from customers extend beyond normal payment terms, we seek to collect interest. We record interest on customer receivables as interest income when collected. Subsequent adjustments for further declines in credit rating are recorded as bad debt expense as a component of selling, general and administrative expense. We also use judgments as to our ability to collect outstanding receivables and provide allowances for the portion of receivables if and when collection becomes doubtful, and we also assess on an ongoing basis whether collectibility is probable at the time of sale. As of December 31, 2018 and 2017, allowances on receivables were not material.

Concentration of Credit Risk

Financial instruments that potentially expose the Company to concentrations of credit risk are limited to cash equivalents, marketable securities, accounts receivable and our foreign exchange derivative contracts. We invest our cash reserves in money market funds or high-quality marketable debt securities in accordance with our investment policy. The stated objectives of our investment policy is to preserve capital, provide liquidity consistent with forecasted cash flow requirements, maintain appropriate diversification and generate returns relative to these investment objectives and prevailing market conditions.

At December 31, 2018, three customers accounted for 48.7% of the accounts receivable balance, with these individual customers ranging from 14.0% to 19.1% of the accounts receivable balance. At December 31, 2017, four customers accounted for 57.7% of the accounts receivable balance, with these individual customers ranging from 10.2% to 18.9% of the accounts receivable balance.

For the year ended December 31, 2018, four customers accounted for 50.3% of our product sales, with these individual customers ranging from 10.0% to 16.4% of our product sales. For the year ended December 31, 2017, three customers accounted for 37% of our product sales, with these individual customers ranging from 10.8% to 15.0% of our product sales. For the year ended December 31, 2016, three customers accounted for 36.7% of our product sales, with these individual customers ranging from 10.0% to 16.0% of our product sales. No other customers accounted for more than 10.0% of accounts receivable or net product sales.

We continue to monitor economic conditions, including volatility associated with international economies and the associated impacts on the financial markets and our business. Substantially all of our accounts receivable are due from wholesale distributors, public hospitals and other government entities. We monitor the financial performance of our customers so that we can appropriately respond to changes in their credit worthiness. We can operate in certain jurisdictions where weakness in economic conditions can result in extended collection periods. To date, we have not experienced any significant losses with respect to collection of our accounts receivable.

Inventories

Inventories are stated at the lower of cost or net realizable value. Cost is determined in a manner that approximates average costs.

The components of inventory are as follows:



	December 31,
	2018		2017
Raw materials	$	31.4	$	4.7
Work-in-process	90.4		148.6
Finished goods	350.7		307.1
	$	472.5	$	460.4

Capitalization of Inventory Costs

We capitalize inventory produced for commercial sale, which may include costs incurred for certain products awaiting regulatory approval. We capitalize inventory produced in preparation of product launches sufficient to support estimated initial market demand. Capitalization of such inventory begins when we have (i) obtained positive results in clinical trials that we believe are necessary to support regulatory approval, (ii) concluded that uncertainties regarding regulatory approval have been sufficiently reduced, and (iii) determined that the inventory has probable future economic benefit. In evaluating whether these conditions have been met, we consider clinical trial results for the underlying product candidate, results from meetings with regulatory authorities, and the compilation of the regulatory application. If we are aware of any material risks or contingencies outside of the standard regulatory review and approval process, or if there are any specific negative issues identified relating to the safety, efficacy, manufacturing, marketing or labeling of the product that would have a significant negative impact on its future economic benefits, the related inventory would not be capitalized. We had no inventory capitalized for products awaiting regulatory approval as of December 31, 2018 and 2017.

Products that have been approved by the U.S. Food and Drug Administration (FDA) or other regulatory authorities are also used in clinical programs to assess the safety and efficacy of the products for usage in diseases that have not been approved by the FDA or other regulatory authorities. The form of the products utilized for both commercial and clinical programs is identical and, as a result, the inventory has an “alternative future use” as defined in authoritative guidance. Raw materials and purchased drug product associated with clinical development programs are included in inventory and charged to research and development expense when the product enters the research and development process and no longer can be used for commercial purposes and, therefore, does not have an “alternative future use”.

For products which are under development and have not yet been approved by regulatory authorities, purchased drug product is charged to research and development expense upon delivery. Delivery occurs when the inventory passes quality inspection and ownership transfers to us. Nonrefundable advance payments for research and development activities, including production of purchased drug product, are deferred and capitalized until the goods are delivered. We also recognize expense for raw materials purchased for developmental purposes when the raw materials pass quality inspection and we have an obligation to pay for the materials.

Inventory Write-Offs

We analyze our inventory levels to identify inventory that may expire prior to sale, inventory that has a cost basis in excess of its estimated realizable value, or inventory in excess of expected sales requirements. Although the manufacturing of our product is subject to strict quality control, certain batches or units of product may no longer meet quality specifications or may expire, which requires adjustments to our inventory values. We also apply judgment related to the results of quality tests that we perform throughout the production process, as well as our understanding of regulatory guidelines, to determine if it is probable that inventory will be saleable. These quality tests are performed throughout the pre-and post-production process, and we continually gather additional information regarding product quality for periods after the manufacture date. Our products currently have a maximum estimated life ranging from 36 to 48 months and, based on our sales forecasts, we expect to realize the carrying value of our inventory. In the future, reduced demand, quality issues or excess supply beyond those anticipated by management may result in a material adjustment to inventory levels, which would be recorded as an increase to cost of sales.

The determination of whether or not inventory costs will be realizable requires estimates by our management. A critical input in this determination is future expected inventory requirements based on internal sales forecasts. We then compare these requirements to the expiry dates of inventory on hand. For inventories that are capitalized in preparation of product launch, we also consider the expected approval date in assessing realizability. To the extent that inventory is expected to expire prior to being sold, we will write down the value of inventory.

Derivative Instruments

We record the fair value of derivative instruments as either assets or liabilities on the balance sheet. The accounting for gains and losses resulting from changes in fair value is dependent on the use of the derivative and whether it is designated and qualifies for hedge accounting.

All qualifying hedging activities are documented at the inception of the hedge and must meet the definition of highly effective in offsetting changes to future cash. On a quarterly basis, we perform an assessment to confirm that outstanding hedges remain highly effective and continue to qualify for hedge accounting. We record the fair value of the qualifying hedges in other current assets, other assets, other current liabilities and other liabilities. All unrealized gains and losses on derivatives that are designated and qualify for hedge accounting are reported in other comprehensive income (loss) and recognized when the underlying hedged transaction affects earnings. When the forecasted transaction occurs, this amount is reclassified into the consolidated statement of operations and presented in the same financial statement line item as the hedged item.

Derivative instruments for which hedge accounting is not applied are recorded at fair value in other current assets and other current liabilities. Unrealized gains and losses resulting from changes in the fair value of these derivatives are reported in other income and expense.

Property, Plant and Equipment

Property, plant and equipment are stated at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. We estimate economic lives as follows:


•	Building and improvements—fifteen to thirty five years


•	Machinery and laboratory equipment—five to fifteen years


•	Computer hardware and software—three to seven years


•	Furniture and office equipment— five to ten years

Leasehold improvements and assets under capital lease arrangements are amortized over the lesser of the asset’s estimated useful life or the term of the respective lease. Maintenance costs are expensed as incurred.

Construction-in-progress reflects amounts incurred for property, plant, or equipment construction or improvements that have not been placed in service.

Assets Held for Sale

We classify assets as held for sale when the following criteria are met: i) management, having the authority to approve the action, commits to a plan to sell the asset, ii) the asset is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of similar assets, iii) an active program to locate a buyer and other actions required to complete the plan to sell the asset have been initiated, iv) the sale of the asset is probable, and transfer of the asset is expected to qualify for recognition as a completed sale, within one year, v) the asset is being actively marketed for sale at a price that is reasonable in relation to its current fair value, and vi) actions required to complete the plan indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn. Assets that are classified as held for sale are recorded at the lower of their carrying value or their fair value less the costs to sell.

In the third quarter 2017, we announced our intention to close the Alexion Rhode Island Manufacturing Facility (ARIMF). In the fourth quarter 2017, we met the criteria for assets held for sale and reclassified the ARIMF assets from property, plant and equipment to assets held for sale recorded within prepaid expenses and other current assets. We subsequently sold ARIMF during the third quarter of 2018.

Manufacturing Facilities

We capitalize costs incurred for the construction of facilities which support commercial manufacturing. We also capitalize costs related to validation activities which are directly attributable to preparing the facility for its intended use, including engineering runs and inventory production necessary to obtain approval of the facility from government regulators for the production of a commercially approved drug. When the facility is substantially complete and ready for its intended use and regulatory approval for commercial production has been received, we will place the asset in service.

The production of inventory for preparing the facility for its intended use requires two types of production: engineering runs which are used for testing purposes only and do not result in saleable inventory, and validation runs which are used for validating equipment and may result in saleable inventory. The costs associated with inventory produced during engineering runs and normal production losses during validation runs are capitalized to fixed assets and depreciated over the asset’s useful life. Saleable inventory produced during the validation process is initially treated as a fixed asset; however, upon regulatory approval, this inventory is reclassified to inventory and expensed in cost of goods sold as product is sold, or in research and development expenses as product is utilized in R&D activities. Abnormal production costs incurred during the validation process are expensed as incurred.

Acquisitions

Business combinations are accounted for using the acquisition method of accounting. Under the acquisition method of accounting, the tangible and intangible assets acquired and the liabilities assumed are recorded as of the acquisition date at their respective fair values. We evaluate a business as an integrated set of activities and assets that is capable of being conducted and managed for the purpose of providing a return in the form of dividends, lower costs or other economic benefits and consists of inputs and substantive processes applied to those inputs that have the ability to contribute to the creation of outputs. If substantially all of the fair value of gross assets acquired is concentrated in a single asset or group of similar identifiable assets, the assets do not represent a business. In an acquisition of a business, the excess of the fair value of the consideration transferred over the fair value of the net assets acquired is recorded as goodwill.

Acquisitions of assets or group of assets that do not meet the definition of a business are accounted for as asset acquisitions using the cost accumulation method, whereby the cost of the acquisition, including certain transaction costs, is allocated to the assets acquired on the basis of relative fair values. No goodwill is recognized in an asset acquisition. Intangible assets that are acquired in an asset acquisition for use in research and development activities which have an alternative future use are capitalized as in-process research and development (IPR&D). Acquired IPR&D which has no alternative future use is recognized as research and development expense at acquisition. Contingent milestone payments associated with asset acquisitions are recognized when probable and estimable. These amounts are expensed to research and development if there is no alternative future use associated with the asset, or capitalized as an intangible asset if alternative future use of the asset exists.

Our consolidated financial statements include the results of operations of an acquired business after the completion of the acquisition.

Intangible Assets

Our intangible assets generally consist of licensing rights, patents, purchased technology, acquired IPR&D and other intangibles. Intangible assets with definite lives are amortized based on their pattern of economic benefit over their estimated useful lives and reviewed periodically for impairment.

Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment. Impairment testing is performed at least annually or when a triggering event occurs that could indicate a potential impairment. If and when development is complete, which generally occurs when regulatory approval to market a product is obtained, the associated assets are deemed finite-lived and are amortized over a period that best reflects the economic benefits provided by these assets.

Goodwill

Goodwill represents the excess of purchase price over fair value of net assets acquired in a business combination and is not amortized. Goodwill is subject to impairment testing at least annually or when a triggering event occurs that could indicate a potential impairment. We are organized and operate as a single reporting unit and therefore the goodwill impairment test is performed using our overall market value, as determined by our traded share price, compared to our book value of net assets.

Impairment of Long-Lived Assets

Our long-lived assets are primarily comprised of intangible assets and property, plant and equipment. We evaluate our finite-lived intangible assets and property, plant and equipment, for impairment whenever events or changes in circumstances indicate the carrying value of an asset or group of assets is not recoverable. If these circumstances exist, recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets.

In addition, indefinite-lived intangible assets, comprised of IPR&D, are reviewed for impairment annually and whenever events or changes in circumstances indicate that it is more likely than not that the asset is impaired by comparing the fair value to the carrying value of the asset. In the second quarter 2017, we recognized an impairment charge of $31.0 related to our SBC-103 acquired in-process research and development asset due to clinical results.

Other Investments

From time to time, we make strategic investments in equity securities of certain biotechnology companies. Our strategic investment portfolio may include equity securities in publicly traded companies, as well as investments in companies with securities that are not publicly traded and where fair value is not readily available. These investments are included in other assets in our consolidated balance sheets.

We have historically recorded our investments in securities that are not publicly traded at cost, less impairments. As of January 1, 2018, we continue to record these investments at cost, less impairments; however, we also adjust the investment for any changes resulting from an observable price change in an orderly transaction for identical or similar investments of the same issuer. We assess relevant transactions that occur on or before the balance sheet date to identify observable price changes, and we regularly monitor these investments to evaluate whether there is an indication that the investment is impaired, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions.

Our investments in equity securities in publicly traded companies which are unrestricted are regularly measured and carried at fair value and classified as Level 1 equity securities within the fair value hierarchy. Investments in publicly traded companies which are subject to holding period restrictions are carried at fair value using an option pricing valuation model and classified as Level 2 equity securities within the fair value hierarchy. The most significant assumptions within the option pricing valuation model are the term of the restrictions and the stock price volatility, which is based upon the historical volatility of similar companies. We also use a constant maturity risk-free interest rate to match the remaining term of the restrictions on such investments.

Contingent Consideration

We record contingent consideration resulting from a business combination at fair value on the acquisition date. On a quarterly basis, we revalue these obligations and record increases or decreases in their fair value as an adjustment to operating earnings. Changes to contingent consideration obligations can result from adjustments to discount rates, accretion of the liability due to the passage of time, changes in our estimates of the likelihood or timing of achieving development or commercial milestones, changes in the probability of certain clinical events or changes in the assumed probability associated with regulatory approval.

Contingent Liabilities

We are currently involved in various claims and legal proceedings. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, we accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals are based on our best estimates based on available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims (and our offers of settlement), we may reassess the potential liability related to these matters and may revise these estimates (and these revisions may be material).

Treasury Stock

Treasury stock is accounted for using the cost method, with the purchase price of the common stock recorded separately as a deduction from stockholders’ equity.

Revenue Recognition

In May 2014, the FASB issued a comprehensive new standard which amends revenue recognition principles. We adopted the new standard on January 1, 2018 by applying the modified retrospective method to all contracts that were not completed as of that date. Under the new guidance, revenue is recognized when a customer obtains control of promised goods or services, in an amount that reflects the consideration expected to be received in exchange for those goods or services. Revenue is recognized through a five-step process: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) a performance obligation is satisfied. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, the Company assesses the goods or services promised within each contract, and determines those that are performance obligations. Revenue is recognized for the applicable performance element when each distinct performance obligation is satisfied.

While results for reporting periods beginning after January 1, 2018 are presented under the new guidance, prior period amounts are not adjusted and continue to be reported under the accounting standards in effect for the prior period. The adoption of the new standard did not significantly change our accounting policies.

Nature of Products

Our principal source of revenue is product sales. Our contracts with customers generally contain a single performance obligation and we recognize revenue from product sales when we have satisfied our performance obligation by transferring control of the product to our customers. Control of the product generally transfers to the customer upon delivery. In certain countries, we sell to distributors on a consignment basis and record revenue when control of the product transfers to the customer upon sale to the end user.

Our customers are primarily comprised of distributors, pharmacies, hospitals, hospital buying groups, and other healthcare providers. In some cases, we may also sell to governments and government agencies. In addition to sales in countries where our products are commercially available, we have also recorded revenue on sales for patients receiving treatment through named-patient programs. The relevant authorities or institutions in those countries have agreed to reimburse for product sold on a named-patient basis where our products have not received final approval for commercial sale.

Revenue is recognized at the amount to which we expect to be entitled in exchange for the sale of our products. This amount includes both fixed and variable consideration and excludes amounts that are collected from customers and remitted to governmental authorities, such as value-added taxes in foreign jurisdictions. Shipping and handling costs associated with outbound freight after control of a product has transferred to our customers are accounted for as a fulfillment cost and are included in operating expenses. The cost for any shipping and handling activities (including customs clearance activities) associated with transactions for which revenue has been recognized are accrued if not completed before the respective period end.

The timing between the recognition of revenue for product sales and the receipt of payment is not significant. Our standard credit terms, which vary based on the country of sale, range from 30 to 120 days and all arrangements are payable within one year of the transfer of the product. We do not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between the transfer of the promised good to the customer and receipt of payment will be one year or less.

Variable Consideration

We pay distribution fees to our distributors and offer rebates and/or discounts, or enter into volume-based reimbursement arrangements with certain customers. We reduce the transaction price on our sales for these amounts. For variable amounts, we estimate the amount of consideration to which we expect to be entitled based on all available historic, current and forecast information. We primarily use the expected value method to estimate variable payments and, in limited circumstances, will apply the most likely method based on the type of variable consideration and what method better predicts the amount of consideration we expect to be entitled to. Consideration that is received from a customer that we expect will need to be refunded in the future is recorded as a refund liability to the customer within accrued expenses. Actual amounts of consideration ultimately received or refunded may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect net product sales and earnings in the period such variances become known.

Variability in the transaction price for our products pursuant to our contracts with customers primarily arises from the following:

Discounts and Rebates: We offer discounts and rebates to certain distributors and customers under our arrangements. In many cases, these amounts are fixed at the time of sale and the transaction price is reduced accordingly. We also provide for rebates under certain governmental programs, including Medicaid in the U.S. and other programs outside the U.S., which are payable based on actual claim data. We estimate these rebates based on an analysis of historical claim patterns and estimates of customer mix to determine which sales will be subject to rebates and the amount of such rebates. We update our estimates and assumptions each period and record any necessary adjustments, which may have an impact on revenue in the period in which the adjustment is made. Generally, the length of time between product sale and the processing and reporting of the rebates is three to six months.

Volume-Based Arrangements: We have entered into volume-based arrangements with governments in certain countries and other customers in which reimbursement is limited to a contractual amount. Under this type of arrangement, amounts billed in excess of the contractual limitation are repaid to the customer as a rebate. We estimate incremental discounts resulting from these contractual limitations, based on forecasted sales during the limitation period, and we apply the discount percentage to product shipments as a reduction of revenue. Our calculations related to these arrangements require estimation of sales during the limitation period, and adjustments in these estimates may have a material impact in the period in which these estimates change.

Distribution & Other Fees: We pay distribution and other fees to certain customers in connection with the sales of our products. We record distribution and other fees paid to our customers as a reduction of revenue, unless the payment is for a distinct good or service from the customer and we can reasonably estimate the fair value of the goods or services received. If both conditions are met, we record the consideration paid to the customer as an operating expense. These costs are typically known at the time of sale, resulting in minimal adjustments subsequent to the period of sale.

Product Returns: Our contracts with customers generally provide for returns only if the product is damaged or defective upon delivery. We assess our sales transactions and arrangements with customers and monitor inventory within our sales channels to determine whether a provision for returns is warranted and a resulting adjustment to the transaction price is necessary. This assessment is based on historical experience and assumptions as of the date of sale and changes in these estimates could have an impact in the period in which the change occurs. Because of factors such as the price of our products, the limited number of patients, the short period from product sale to patient infusion and limited contractual return rights, our customers often carry limited inventory.

The amount of variable consideration included in the transaction price is constrained by the amount that is probable will not result in a significant reversal of revenue. We consider our experience with similar transactions and expectations regarding the contract in estimating the amount of variable consideration to which we expect to be entitled, and determining whether the estimated variable consideration should be constrained. We do not have any material constraints on the variable consideration included within the transaction price of our current revenue arrangements.

See Note 19 “Segment Information” for a summary of revenue from contracts with customers by product and geographical region.

Contract Balances and Receivables

Contract liabilities relate to consideration received and/or billed for goods that have not been delivered to the customer and for which the performance obligation has not yet been completed. These amounts are included within other current liabilities in the consolidated statements of operations.

The following table provides information about receivables and contract liabilities from our contracts with customers.



	December 31, 2018		December 31, 2017
Receivables, which are included in "Trade accounts receivable, net"	$	922.3	$	726.5
Contract liabilities, which are included in "Other current liabilities"	$	3.4	$	15.9

Research and Development Expenses

Research and development expenses are comprised of costs incurred in performing research and development activities including payroll and benefits, preclinical, clinical trial and related clinical manufacturing costs, manufacturing development and scale-up costs, product development and regulatory costs, contract services and other outside contractor costs, research license fees, depreciation and amortization of lab facilities, and lab supplies. These costs are expensed as incurred. We accrue costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the contract research organizations, clinical study sites, laboratories, consultants, or other clinical trial vendors that perform the activities.

Share-Based Compensation

We have two share-based compensation plans pursuant to which awards are currently being made: (i) the 2017 Incentive Plan (2017 Plan) and (ii) the 2015 Employee Stock Purchase Plan (ESPP). The 2017 Plan replaced the Amended & Restated 2004 Incentive Plan (2004 Plan), effective May 10, 2017. Under the 2017 Plan, restricted stock, restricted stock units, stock options and other stock-related awards may be granted to our directors, officers, employees and consultants or advisors of the Company or any subsidiary. Under the ESPP, eligible employees can purchase shares of common stock at a discount semi-annually through payroll deductions. To date, share-based compensation issued under the plans consists of incentive and non-qualified stock options, restricted stock and restricted stock units, including restricted stock units with market and non-market performance conditions, and shares issued under our ESPP.

Compensation expense for our share-based awards is recognized based on the estimated fair value of the awards on the grant date. Compensation expense reflects an estimate of the number of awards expected to vest and is primarily recognized on a straight-line basis over the requisite service period of the individual grants, which typically equals the vesting period. Compensation expense for awards with performance conditions is recognized using the graded-vesting method.

Our estimates of employee stock option values rely on estimates of factors we input into the Black-Scholes model. The key factors involve an estimate of future uncertain events. Significant assumptions include the use of historical volatility to determine the expected stock price volatility. We also estimate expected term until exercise and the reduction in the expense from expected forfeitures. We currently use historical exercise and cancellation patterns as our best estimate of future estimated life.

For our non-market performance-based awards, we estimate the anticipated achievement of the performance targets, including forecasting the achievement of future financial targets. These estimates are revised periodically based on the probability of achieving the performance targets and adjustments are made throughout the performance period as necessary. We use payout simulation models to estimate the grant date fair value of awards with market-based performance conditions. The payout simulation models assume volatility of our common stock and the common stock of a comparator group of companies, as well as correlations of returns of the price of our common stock and the common stock prices of the comparator group.

The purchase price of common stock under our ESPP is equal to 85.0% of the lower of (i) the market value per share of the common stock on the first business day of an offering period or (ii) the market value per share of the common stock on the purchase date. The fair value of the discounted purchases made under our ESPP is calculated using the Black-Scholes model. The fair value of the look-back provision plus the 15.0% discount is recognized as compensation expense over the 6 month purchase period.

Restructuring and restructuring related expenses

We record liabilities associated with one-time employee termination benefits and exit or disposal activities in the period in which the liability is incurred. One-time employee benefits are incurred when communicated to employees and where detailed action plans have been approved. Costs for one-time termination benefits in which the employee is required to render service until termination in order to receive benefits are recognized ratably over the service period. For existing benefit arrangements, employee termination costs are accrued when the exit or disposal cost are probable and estimable.

Restructuring related expenses include accelerated depreciation costs and impairment charges associated with assets impacted by a restructuring exit activity. Accelerated depreciation costs represent the difference between the depreciation expense recognized over the revised useful life of the asset, based upon the anticipated date an impacted site closure and the depreciation expense as determined using the useful life prior to the restructuring activities.

Earnings Per Common Share

Basic earnings per common share (EPS) is computed by dividing net income by the weighted-average number of shares of common stock outstanding. For purposes of calculating diluted EPS, the denominator reflects the potential dilution that could occur if stock options, unvested restricted stock units or other contracts to issue common stock were exercised or converted into common stock, using the treasury stock method.

The following table summarizes the calculation of basic and diluted EPS for years ended December 31, 2018, 2017 and 2016:



	Year Ended December 31,
	2018		2017		2016
Net income used for basic and diluted calculation	$	77.6	$	443.3	$	399.4
Shares used in computing earnings per common share—basic	222.7		223.9		224.3
Weighted-average effect of dilutive securities:
Stock awards	1.8		1.5		2.0
Shares used in computing earnings per common share—diluted	224.5		225.4		226.3
Earnings per common share:
Basic	$	0.35	$	1.98	$	1.78
Diluted	$	0.35	$	1.97	$	1.76

We exclude from EPS the weighted-average number of securities whose effect is anti-dilutive. Excluded from the calculation of EPS for the years ended December 31, 2018, 2017 and 2016 were 2.8, 4.0, and 4.2 shares of common stock, respectively, because their effect is anti-dilutive.

Income Taxes

We utilize the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement carrying amounts and tax basis of assets and liabilities using enacted tax rates in effect for years in which the temporary differences are expected to reverse. We periodically evaluate the likelihood of the realization of deferred tax assets and reduce the carrying amount of these deferred tax assets by a valuation allowance when it is more likely than not that deferred tax assets will not be realized.

We recognize the benefit of an uncertain tax position that has been taken or we expect to take on income tax returns if such tax position is more likely than not to be sustained. The tax benefit recognized in the financial statements for a particular tax position is based on the largest benefit that is more likely than not to be realized. The amount of unrecognized tax benefits is adjusted, as appropriate, for changes in facts and circumstances, such as significant amendments to existing tax law, new regulations or interpretations by the taxing authorities, or new information obtained during a tax examination or resolution of an examination. We also accrued for potential interest and penalties related to unrecognized tax benefits as a component of tax expense.

In December 2017, the Tax Cuts and Jobs Act (Tax Act) was enacted into law. The Tax Act decreased the U.S. federal corporate tax rate to 21.0%, imposed a minimum tax on foreign earnings related to intangible assets (GILTI), a one-time transition tax on previously unremitted foreign earnings, and modified the taxation of other income and expense items. With regard to the GILTI minimum tax, foreign earnings are reduced by the profit attributable to tangible assets and a deductible allowance of up to 50.0%, subject to annual limitations. We have elected to account for the impact of the minimum tax in deferred taxes.

Comprehensive Income

Comprehensive income is comprised of net income and other comprehensive income (loss). Other comprehensive income (loss) includes changes in equity that are excluded from net income, such as changes in pension liabilities, unrealized gains and losses on marketable debt securities, unrealized gains and losses on hedge contracts and foreign currency translation adjustments. Certain of these changes in equity are reflected net of tax.

Reclassifications

Certain items in the prior year’s consolidated financial statements have been reclassified to conform to the current presentation.

New Accounting Pronouncements

In February 2016, the FASB issued a new standard that requires lessees to recognize leases on-balance sheet and disclose key information about leasing arrangements. The new standard establishes a right-of-use (ROU) model that requires a lessee to recognize a ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. The standard is effective on January 1, 2019, with early adoption permitted. We adopted the new standard on January 1, 2019 and use the effective date as our date of initial application. In July 2018, the FASB issued an update that provided an additional transition option that allows companies to continue applying the guidance under the lease standard in effect at that time in the comparative periods presented in the consolidated financial statements. Companies that elect this option would record a cumulative-effect adjustment to the opening balance of retained earnings on the date of adoption. We elected this optional transition method. We also elected the “package of practical expedients”, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. We continue to evaluate other practical expedients available under the standard.

We have substantially completed our assessment of the standard as well as implementation of our leasing software, including data upload and test procedures. We continue to finalize our calculations, including our discount rate assumptions, related to the new standard. We are also continuing to establish new processes and internal controls that may be required to comply with the new lease accounting and disclosure requirements set by the new standard. We expect the impact of the standard adoption to decrease our assets, liabilities and retained earnings within our consolidated balance sheet. These decreases will result from the derecognition of our existing assets and financing obligations related to our build to suit leases offset by the recognition of new ROU assets and liabilities as a result of the leasing standard.

In June 2016, the FASB issued a new standard intended to improve reporting requirements specific to loans, receivables and other financial instruments. The new standard requires that credit losses be reported based on expected losses compared to the current incurred loss model. The new standard also requires enhanced disclosure of credit risk associated with respective assets. The standard is effective for interim and annual periods beginning after December 15, 2019 with early adoption permitted. We are currently assessing the impact of this standard on our financial condition and results of operations.

In February 2018, the FASB issued a new standard that would permit entities to make a one time reclassification from accumulated other comprehensive income (AOCI) to retained earnings for the stranded tax effects resulting from the newly enacted corporate tax rates under the Tax Cuts and Jobs Act (the Tax Act), that was effective for the year ended December 31, 2017. The amount of the reclassification is calculated on the basis of the difference between the historical tax rate and newly enacted tax rate. The standard is effective for interim and annual periods beginning after December 15, 2018 with early adoption permitted. We are currently assessing the impact of this standard on our financial condition.

In August 2018, the FASB issued a new standard on a customer's accounting for implementation, set-up, and other upfront costs incurred in a cloud computing arrangement (CCA). Under the new guidance, customers will assess if a CCA includes a software license and if a CCA does include a software license, implementation and set-up costs will be accounted for consistent with existing internal-use software implementation guidance. Implementation costs associated with a CCA that does not include a software license would be expensed to operating expenses. The standard also provides classification guidance on these implementation costs as well as additional quantitative and qualitative disclosures. The standard is effective for public business entities for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim periods. Entities can choose to adopt the new guidance prospectively or retrospectively. We are currently assessing the impact this standard will have on our statement of financial condition and results of operations.

Recently Adopted Accounting Pronouncements

In May 2014, the FASB issued a comprehensive new standard which amends revenue recognition principles and provides a single set of criteria for revenue recognition among all industries. The new standard provides a five-step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We adopted the new standard on January 1, 2018.

In January 2017, the FASB issued a new standard that clarifies the definition of a business and determines when an integrated set of assets and activities is not a business. This framework requires that if substantially all of the fair value of gross assets acquired or disposed of is concentrated in a single asset or group of similar identifiable assets, the assets would not represent a business. We adopted the new standard on January 1, 2018 and applied the new guidance prospectively to transactions occurring after adoption. We anticipate that the adoption of this new standard will likely result in more transactions, to the extent that such transactions are undertaken by the Company, being accounted for as asset acquisitions.

In January 2016, the FASB issued a new standard that changes accounting for equity investments, financial liabilities under the fair value option, and presentation and disclosure requirements for financial instruments. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. Equity investments with readily determinable fair values will be measured at fair value with changes in fair value recognized in net income. Companies have the option to either measure equity investments without readily determinable fair values at fair value, or at cost adjusted for changes in observable prices minus impairment. We adopted the new standard on January 1, 2018, and elected to measure our existing equity investments without readily determinable fair values at cost adjusted for changes in observable prices minus impairment. In connection with the adoption of the new standard, we reclassified an immaterial amount of unrealized gains on equity securities from accumulated other comprehensive income to retained earnings. The guidance related to equity investments without readily determinable fair values was applied prospectively to equity investments that existed as of the date of adoption. We will assess equity investments without readily determinable fair values for observable price changes and impairment on a quarterly basis. Refer to Note 7, Other Investments, for further details.

In March 2017, the FASB issued a new standard that improves the presentation of net periodic pension cost and net periodic post retirement benefit cost by requiring the bifurcation of net benefit cost. Under the new standard, the service cost component of net benefit cost will be presented with other employee costs in operating expenses, while other components will be reported separately in other income and expense. We adopted the new standard on January 1, 2018. The adoption of this standard did not have a material impact on our consolidated statements of operations.

In November 2016, the FASB issued a new standard that clarifies how entities should present restricted cash in the statement of cash flows. Under the new standard, changes in total cash, inclusive of restricted cash, should be reflected in the statement of cash flows. As a result, transfers between cash and restricted cash will no longer be reflected as activity within the statement of cash flows. We adopted the new standard on January 1, 2018. The adoption of this standard did not have a material impact on our consolidated statements of cash flows.

In August 2017, the FASB issued a new standard intended to improve and simplify certain aspects of the accounting for hedges. The new standard is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency as to the scope and results of hedging programs. It also amends the presentation and disclosure requirements and changes how companies assess effectiveness. The standard is effective for interim and annual periods beginning after December 15, 2018 with early adoption permitted. We early adopted the new standard in the second quarter 2018 using the modified retrospective method. The adoption of this standard did not have a material impact on our consolidated financial statements.

Impacts of the New Revenue Standard

We adopted the new revenue standard by applying the modified retrospective method to all contracts that were not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under the new standard, while prior period amounts are not adjusted and continue to be reported under the accounting standards in effect for the prior period. Upon adoption of the new revenue recognition standard, on January 1, 2018, we reduced our deferred revenue balance by $10.4, with an offsetting increase of $6.0 in retained earnings due to the cumulative impact of adopting this new standard.

The impact to net product sales and net income for the year ended December 31, 2018 was an increase of $5.3 and $4.8, respectively, as a result of adopting the new standard. The new standard also resulted in a decrease of $17.9 in deferred revenue and an increase of $10.8 in retained earnings as of December 31, 2018. The adoption of the new revenue standard did not have a material impact on any other balances within the consolidated financial statements as of and for the year ended December 31, 2018.

Acquisitions

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Acquisitions

Wilson Therapeutics AB

On May 25, 2018, we completed the acquisition of Wilson Therapeutics AB (publ), a biopharmaceutical company based in Stockholm, Sweden (Wilson Therapeutics) that develops a novel therapy for patients with rare copper-mediated disorders, pursuant to a recommended public cash offer of SEK 232 for each share of stock of Wilson Therapeutics. As a result of the acquisition, we added WTX101 (ALXN1840), a highly innovative drug candidate that is currently in the early stages of Phase III clinical trials for the treatment of patients with Wilson disease, to our clinical pipeline.

The acquisition of Wilson Therapeutics is accounted for as an asset acquisition, as substantially all of the fair value of the gross assets acquired is concentrated in a single asset, WTX101.

The following table summarizes the total consideration for the acquisition and the value of assets acquired and liabilities assumed:



Consideration
Cash paid for acquisition of Wilson Therapeutics outstanding shares	$	749.3
Transaction costs	15.1
Total consideration	$	764.4

Assets Acquired and Liabilities Assumed
Cash	$	45.1
In-process research & development	803.7
Employee related liabilities	(71.4		)
Other assets and liabilities	(13.0		)
Total net assets acquired	$	764.4

The acquired in-process research and development asset relates to WTX101. Due to the stage of development of this asset, significant risk remains and it is not yet probable that there is future economic benefit from this asset. Absent successful clinical results and regulatory approval for the asset, there is no alternative future use associated with WTX101. Accordingly, the value of this asset of $803.7 was expensed during the year ended December 31, 2018.

Employee related liabilities include the value of outstanding employee equity incentive awards that were accelerated in connection with the Wilson Therapeutics acquisition that have been settled in cash. Also included in this amount are employer tax obligations associated with the employee equity incentive awards.

In connection with rights to WTX101 that were previously acquired by Wilson Therapeutics from third parties, we could be required to pay up to approximately $19.0 if certain development, regulatory and commercial milestones are met over time, as well as royalties on commercial sales.

Syntimmune, Inc.

In September 2018, we entered into a definitive agreement to acquire Syntimmune, Inc. (Syntimmune), a clinical-stage biotechnology company developing an antibody therapy targeting the neonatal Fc receptor (FcRn). Syntimmune’s lead candidate, SYNT001 (ALXN1830), is a monoclonal antibody that is designed to inhibit the interaction of FcRn with Immunoglobulin G (IgG) and IgG immune complexes, and is being studied in Phase 1b/2a trials for the treatment of IgG-mediated autoimmune diseases. The acquisition of Syntimmune closed in November 2018. Under the terms of the agreement, Alexion acquired Syntimmune for an upfront cash payment of $400.0, with the potential for additional milestone-dependent payments of up to $800.0, for a total value of up to $1,200.0.

The acquisition of Syntimmune is accounted for as an asset acquisition, as substantially all of the fair value of the gross assets acquired is concentrated in a single in-process research and development asset, SYNT001.

The following table summarizes the total consideration for the acquisition and the value of the assets acquired and liabilities assumed:



Consideration
Upfront payment for acquisition of Syntimmune outstanding shares	$	400.0
Cash acquired	4.2
Working capital adjustment	6.4
Transaction costs	0.9
Total consideration	$	411.5

Assets Acquired and Liabilities Assumed
Cash	$	4.2
In-process research & development	379.3
Deferred tax assets	25.1
Other assets and liabilities	2.9
Total net assets acquired	$	411.5

The acquired in-process research and development asset relates to SYNT001. Due to the stage of development of this asset, significant risk remains and it is not yet probable that there is future economic benefit from this asset. Absent successful clinical results and regulatory approval for the asset, there is no alternative future use associated with SYNT001. Accordingly, the value of this asset of $379.3 was expensed during the year ended December 31, 2018.

Property, Plant and Equipment, Net

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment, Net [Abstract]

Property, Plant and Equipment, Net

A summary of property, plant and equipment is as follows:



	December 31, 2018			December 31, 2017
Land	$	9.6		$	9.6
Buildings and improvements	520.1			427.9
Machinery and laboratory equipment	161.7			159.2
Computer hardware and software	144.8			141.5
Furniture and office equipment	27.5			23.8
Construction-in-progress	827.1			723.7
	1,690.8			1,485.7
Less: Accumulated depreciation and amortization	(219.3		)	(160.3		)
	$	1,471.5		$	1,325.4

Included in construction-in-progress at December 31, 2017 was $64.1 of costs associated with the construction of our leased facility in Boston, Massachusetts. Construction of this facility was completed and the building was placed into service in the second quarter 2018. Additionally, there were costs of $203.9 and $180.6 as of December 31, 2018 and 2017, respectively, included within construction-in-process associated with the construction of a new Lonza manufacturing facility. Although we do not legally own these premises, we are deemed to be the owner of the buildings during the construction period based on applicable accounting guidance for build-to-suit leases, see Note 10, “Facility Lease Obligations” for additional information.

Depreciation and amortization of property, plant and equipment was approximately $77.9, $95.8 and $64.0 recorded within operating expenses on our consolidated statement of operations for the years ended December 31, 2018, 2017 and 2016, respectively. Included within this amount for the years ended December 31, 2018 and 2017 were charges related to the 2017 restructuring activities. See Note 18, “Restructuring and Related Expenses” for additional information.

At December 31, 2018 and 2017, computer software costs included in property, plant and equipment were $50.3 and $58.2, respectively. Depreciation and amortization expense for capitalized computer software costs was $17.4, $16.0 and $12.4 for the years ended December 31, 2018, 2017 and 2016, respectively.

In January 2019, we adopted a new lease accounting standard. See Note 1 “Business Overview & Summary of Significant Accounting Policies” for an overview of the impact this standard will have on our property, plant and equipment balances in 2019.

Intangible Assets and Goodwill

12 Months Ended

Dec. 31, 2018

Finite-Lived Intangible Assets [Line Items]

Intangible Assets and Goodwill

The following table summarizes the carrying amount of our intangible assets and goodwill, net of accumulated amortization:



		December 31, 2018							December 31, 2017
	Estimated Life (years)	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Licensing Rights	5-8	$	39.0	$	(29.3	)	$	9.7	$	31.0	$	(28.5	)	$	2.5
Patents	7	10.5		(10.5		)	—		10.5		(10.5		)	—
Purchased technology	6-16	4,710.5		(1,079.1		)	3,631.4		4,710.5		(758.9		)	3,951.6
Other Intangibles	5	0.4		(0.2		)	0.2		0.4		(0.1		)	0.3
Total		$	4,760.4	$	(1,119.1	)	$	3,641.3	$	4,752.4	$	(798.0	)	$	3,954.4
Goodwill	Indefinite	$	5,040.3	$	(2.9	)	$	5,037.4	$	5,040.3	$	(2.9	)	$	5,037.4

Amortization expense was $321.1, $320.2 and $322.2 for the years ended December 31, 2018, 2017 and 2016, respectively. Assuming no changes in the gross cost basis of intangible assets, the total estimated amortization expense for finite-lived intangible assets is approximately $322.0 for each of the years ending December 31, 2019 through December 31, 2023.

Marketable Securities

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale debt securities by type of security at December 31, 2018 and December 31, 2017 were as follows:



	December 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Commercial paper	$	52.1	$	—	$	—		$	52.1
Corporate bonds	122.9		—		(0.1		)	122.8
Other government related obligations:
U.S.	17.5		—		—			17.5
Bank certificates of deposit	33.2		—		—			33.2
Total available-for-sale debt securities	$	225.7	$	—	$	(0.1	)	$	225.6



	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Commercial paper	$	16.0	$	—	$	—		$	16.0
Repurchase agreements	27.0		—		—			27.0
Corporate bonds	432.2		0.5		(0.2		)	432.5
Other government related obligations:
Foreign	426.3		0.2		(0.2		)	426.3
Bank certificates of deposit	11.8		—		—			11.8
Total available-for-sale debt securities	$	913.3	$	0.7	$	(0.4	)	$	913.6

The aggregate fair value of available-for-sale debt securities in an unrealized loss position as of December 31, 2018 and December 31, 2017 was $128.7 and $436.2, respectively. Investments that have been in a continuous unrealized loss position for more than twelve months was $12.0 as of December 31, 2017. We did not have any investments in a continuous unrealized loss position for more than twelve months as of December 31, 2018. As of December 31, 2018 we believe that the cost basis of our available-for-sale debt securities is recoverable.

The fair values of available-for-sale debt securities by classification in the consolidated balance sheet were as follows:



	December 31, 2018		December 31, 2017
Cash and cash equivalents	$	43.8	$	42.7
Marketable securities	181.8		870.9
	$	225.6	$	913.6

The fair values of available-for-sale debt securities as of December 31, 2018, by contractual maturity, are summarized as follows:



	December 31, 2018
Due in one year or less	$	211.5
Due after one year through three years	14.1
Due after three years through five years	—
	$	225.6

We sponsor a nonqualified deferred compensation plan which allows certain highly-compensated employees to elect to defer income to future periods. Participants in the plan earn a return on their deferrals based on several investment options, which mirror returns on underlying mutual fund investments. We choose to invest in the underlying mutual fund investments to offset the liability associated with our nonqualified deferred compensation plan. These mutual fund investments are valued at net asset value per share and are carried at fair value with gains and losses included in investment income. The changes in the underlying liability to the employee are recorded in operating expenses. As of December 31, 2018 and December 31, 2017, the fair value of these investments was $16.5 and $18.5, respectively.

We utilize the specific identification method in computing realized gains and losses. Realized gains and losses on our marketable securities were not material for the years ended December 31, 2018, 2017 and 2016.

Derivative Instruments and Hedging Activities

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities [Abstract]

Derivative Instruments and Hedging Activities

We operate internationally and, in the normal course of business, are exposed to fluctuations in foreign currency exchange rates. The exposures result from portions of our revenues, as well as the related receivables, and expenses that are denominated in currencies other than the U.S. dollar, primarily the Euro and Japanese Yen. We are also exposed to fluctuations in interest rates on outstanding borrowings under our revolving credit facility and term loan facility. We manage these exposures within specified guidelines through the use of derivatives. All of our derivative instruments are utilized for risk management purposes, and we do not use derivatives for speculative trading purposes.

We enter into foreign exchange forward contracts, with durations of up to 60 months, to hedge exposures resulting from portions of our forecasted revenues, including intercompany revenues, and certain forecasted expenses that are denominated in currencies other than the U.S. dollar. The purpose of these hedges is to reduce the volatility of exchange rate fluctuations on our operating results. These hedges are designated as cash flow hedges upon contract inception. As of December 31, 2018, we had open revenue related foreign exchange forward contracts with notional amounts totaling $991.1 that qualified for hedge accounting with current contract maturities through December 2020. As of December 31, 2018, we had open expense related foreign exchange forward contracts with notional amounts totaling $20.3 that qualified for hedge accounting with contract maturities through September 2022.

To achieve a desired mix of floating and fixed interest rates on our term loan, we enter into interest rate swap agreements that qualify for and are designated as cash flow hedges. These contracts convert the floating interest rate on a portion of our debt to a fixed rate, plus a borrowing spread.

The following tables summarize the total interest rate swap contracts executed as of December 31, 2018:



Type of Interest Rate Swap	Notional Amount	Effective Date	Termination Date	Fixed Interest Rate or Rate Range
Floating to Fixed	2,031.3	December 2016 - January 2018	December 2018 - December 2019	0.98% - 1.62%
Floating to Fixed	450.0	December 2018	December 2022	2.60% - 2.79%
Floating to Fixed	300.0	January 2019	December 2019	2.08%
Floating to Fixed	1,100.0	December 2019	December 2022	2.70% - 2.83%

In January 2019, we entered into an additional interest rate swap agreement with a notional amount of $200.0 that is effective from December 31, 2019 through December 31, 2022 and converts the floating rate on a portion of our term loan to a fixed rate of 2.37%, plus a borrowing spread.

During the second quarter 2018, we adopted the new standard for accounting for hedges that is designed to simplify the application of hedge accounting and increase transparency as to the scope and results of hedging programs. The updated guidance no longer requires the separate measurement and reporting of hedge ineffectiveness. Following adoption, all unrealized gains and losses on derivatives that are designated and qualify for hedge accounting are reported in other comprehensive income (loss) and recognized in our consolidated statements of operations when the underlying hedged transaction affects earnings.

The amount of gains and losses recognized in the consolidated statements of operations for the years ended December 31, 2018, 2017, and 2016 from foreign exchange and interest rate swap contracts that qualified as cash flow hedges were as follows:



	Year ended December 31,
	2018						2017					2016
	Net Product Sales			Interest Expense			Net Product Sales		Interest Expense			Net Product Sales		Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	4,130.1		$	(98.2	)	$	3,549.5	$	(98.4	)	$	3,081.7	$	(96.9	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	(1.8	)	$	—		$	28.9	$	—		$	73.0	$	—
Interest Rate Swap Contracts	$	—		$	13.6		$	—	$	(1.8	)	$	—	$	(0.2	)

The impact on accumulated other comprehensive income (AOCI) and earnings from foreign exchange and interest rate swap contracts that qualified as cash flow hedges, for the years ended December 31, 2018, 2017, and 2016 were as follows:



	Year Ended December 31,
	2018			2017			2016
Foreign Exchange Contracts:
Gain (loss) recognized in AOCI, net of tax	$	37.7		$	(96.1	)	$	40.2
Gain (loss) reclassified from AOCI to net product sales (effective portion), net of tax	$	(1.4	)	$	18.7		$	47.3
Interest Rate Contracts:
Gain (loss) recognized in AOCI, net of tax	$	(4.8	)	$	7.9		$	6.2
Gain (loss) reclassified from AOCI to interest expense, net of tax	$	10.8		$	(1.1	)	$	(0.1	)

Assuming no change in foreign exchange rates from market rates at December 31, 2018, $9.8 of gains recognized in AOCI will be reclassified to revenue over the next 12 months. Assuming no change in LIBOR-based interest rates from market rates at December 31, 2018, $19.3 of gains recognized in AOCI will be reclassified to interest expense over the next 12 months. Amounts recognized in AOCI for expense related foreign exchange forward contracts was immaterial as of December 31, 2018.

We enter into foreign exchange forward contracts, with durations up to 6 months, designed to limit the balance sheet exposure of monetary assets and liabilities. We enter into these hedges to reduce the impact of fluctuating exchange rates on our operating results. Hedge accounting is not applied to these derivative instruments as gains and losses on these hedge transactions are designed to offset gains and losses on underlying balance sheet exposures. As of December 31, 2018, the notional amount of foreign exchange contracts where hedge accounting is not applied was $1,511.6.

We recognized a gain (loss) of $23.0, $(14.7) and $(5.2), in other income and expense for the years ended December 31, 2018, 2017 and 2016, respectively, associated with the foreign exchange contracts not designated as hedging instruments. These amounts were partially offset by gains or losses on monetary assets and liabilities.

The following tables summarize the fair value of outstanding derivatives at December 31, 2018 and 2017:



	December 31, 2018
	Asset Derivatives			Liability Derivatives
	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Derivatives designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	$	16.9	Other current liabilities	$	7.3
Foreign exchange forward contracts	Other assets	0.3		Other liabilities	3.1
Interest rate contracts	Prepaid expenses and other current assets	20.1		Other current liabilities	0.8
Interest rate contracts	Other assets	—		Other liabilities	17.3
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	23.6		Other current liabilities	11.5
Total fair value of derivative instruments		$	60.9		$	40.0



	December 31, 2017
	Asset Derivatives			Liability Derivatives
	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Derivatives designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	$	12.9	Other current liabilities	$	34.8
Foreign exchange forward contracts	Other assets	4.1		Other liabilities	26.0
Interest rate contracts	Prepaid expenses and other current assets	9.3		Other current liabilities	—
Interest rate contracts	Other assets	12.5		Other liabilities	—
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	10.0		Other current liabilities	13.7
Total fair value of derivative instruments		$	48.8		$	74.5

Although we do not offset derivative assets and liabilities within our consolidated balance sheets, our International Swap and Derivatives Association agreements provide for net settlement of transactions that are due to or from the same counterparty upon early termination of the agreement due to an event of default or other termination event. The following tables summarize the potential effect on our consolidated balance sheets of offsetting our foreign exchange forward contracts and interest rate contracts subject to such provisions:



December 31, 2018
									Gross Amounts Not Offset in the Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	60.9		$	—	$	60.9		$	(30.2	)	$	—	$	30.7
Derivative liabilities	$	(40.0	)	$	—	$	(40.0	)	$	30.2		$	—	$	(9.8	)



December 31, 2017
									Gross Amounts Not Offset in the Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	48.8		$	—	$	48.8		$	(26.3	)	$	—	$	22.5
Derivative liabilities	$	(74.5	)	$	—	$	(74.5	)	$	26.3		$	—	$	(48.2	)

Debt

12 Months Ended

Dec. 31, 2018

Debt [Abstract]

Debt

On June 7, 2018, we entered into an Amended and Restated Credit Agreement (the Credit Agreement), with Bank of America, N.A. as Administrative Agent. The Credit Agreement amends and restates our credit agreement dated as of June 22, 2015 (the Prior Credit Agreement).

The Credit Agreement provides for a $1,000.0 revolving credit facility and a $2,612.5 term loan facility. The revolving credit facility and the term loan facility mature on June 7, 2023. Beginning with the quarter ending June 30, 2019, we are required to make amortization payments of 5.00% of the aggregate principal amount of the term loan facility annually, payable in equal quarterly installments.

Loans under the Credit Agreement bear interest, at our option, at either a base rate or a Eurodollar rate, in each case plus an applicable margin. Under the Credit Agreement, the applicable margins on base rate loans range from 0.25% to 1.00% and the applicable margins on Eurodollar loans range from 1.25%to 2.00%, in each case based on our consolidated net leverage ratio (as calculated in accordance with the Credit Agreement). At December 31, 2018, the interest rate on our outstanding loans under the Credit Agreement was 3.90%. Our obligations under the Credit Agreement are guaranteed by certain of Alexion Pharmaceuticals, Inc.'s foreign and domestic subsidiaries and secured by liens on certain of our subsidiaries’ equity interests, subject to certain exceptions. Under the terms of the Credit Agreement, we must maintain a ratio of total net debt to EBITDA of 3.50 to 1.00 (subject to certain limited adjustments) and EBITDA to cash interest expense ratio of at least 3.50 to 1.00, in each case as calculated in accordance with the Credit Agreement.

The Credit Agreement contains certain representations and warranties, affirmative and negative covenants and events of default. The negative covenants in the Credit Agreement restrict Alexion’s and its subsidiaries’ ability, subject to certain baskets and exceptions, to (among other things) incur liens or indebtedness, make investments, enter into mergers and other fundamental changes, make dispositions or pay dividends. The restriction on dividend payments includes an exception that permits us to pay dividends and make other restricted payments regardless of dollar amount so long as, after giving pro forma effect thereto, we have a consolidated net leverage ratio, as defined in the Credit Agreement, within predefined ranges, subject to certain increases following designated material acquisitions.

In connection with entering into the Credit Agreement and the Prior Credit Agreement, we paid an aggregate of$53.1 in financing costs. Financing costs are amortized as interest expense over the life of the debt. Amortization expense associated with deferred financing costs for the years ended December 31, 2018, 2017, and 2016 was $8.0, $9.2, and $10.3, respectively. Remaining unamortized deferred financing costs as of December 31, 2018 and December 31, 2017 were $20.8 and $21.0, respectively.

As of December 31, 2018, we had $2,612.5 outstanding on the term loan and $250.0 of borrowings outstanding under the revolving credit facility. The $250.0 of proceeds on the revolving credit facility was used to refinance amounts outstanding under the Prior Credit Agreement. As of December 31, 2018, we had open letters of credit of $1.7 that offset our availability in the revolving facility. In January 2019 we paid the outstanding revolving credit facility of $250.0 in full.

The fair value of our long term debt, which is measured using Level 2 inputs of the fair value hierarchy, approximates book value.

The contractual maturities of our long-term debt obligations, including our revolving credit facility, due subsequent to December 31, 2018 are as follows:



Year
2019	$	348.0
2020	130.6
2021	130.6
2022	130.6
2023	2,122.7

Facility Lease Obligations

12 Months Ended

Dec. 31, 2018

Leases [Abstract]

Facility Lease Obligation

Facility Lease Obligations

New Haven Facility Lease Obligation

In November 2012, we entered into a lease agreement for office and laboratory space to be constructed in New Haven, Connecticut. The term of the lease commenced in 2015 and will expire in 2030, with a renewal option of ten years. Although we do not legally own the premises, we are deemed to be the owner of the building due to the substantial improvements directly funded by us during the construction period based on applicable accounting guidance for build-to-suit leases. Accordingly, the landlord’s costs of constructing the facility during the construction period are required to be capitalized, as a non-cash transaction, offset by a corresponding facility lease obligation in our consolidated balance sheets.

Construction of the facility was completed and the building was placed into service in the first quarter 2016. The imputed interest rate on this facility lease obligation as of December 31, 2018 was approximately 11%. Associated with this arrangement, we recognized interest expense of $13.3, $14.2, and $14.0 for the years ended December 31, 2018, 2017, and 2016, respectively. As of December 31, 2018 and 2017, our total facility lease obligation was $133.5 and $134.6, respectively, recorded within other current liabilities and facility lease obligation in our consolidated balance sheets.

In the fourth quarter of 2018 we amended the New Haven lease agreement significantly reducing our leased square footage in the building beginning in 2019 through the expiration of the lease. This amendment does not impact our previous conclusions that we are deemed the owner of the building for accounting purposes. In conjunction with this lease modification, during the fourth quarter of 2018 we made a payment of $53.0 to a third party as an incentive to lease the released square footage. This was capitalized within other assets in our consolidated balance sheets as of December 31, 2018.

Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	9.4
2020	8.8
2021	9.0
2022	9.2
2023	9.2
Thereafter	63.9

Lonza Facility Lease Obligation

During the third quarter 2015, we entered into a new agreement with Lonza Group AG and its affiliates (Lonza) whereby Lonza will construct a new manufacturing facility dedicated to Alexion at one of its existing facilities. The agreement requires us to make certain payments during the construction of the new manufacturing facility and annual payments for ten years thereafter. As a result of our contractual right to full capacity of the new manufacturing facility, a portion of the payments under the agreement are considered to be lease payments and a portion as payment for the supply of inventory. Although we will not legally own the premises, we are deemed to be the owner of the manufacturing facility during the construction period based on applicable accounting guidance for build-to-suit leases due to our involvement during the construction period. Accordingly, the landlord’s costs of constructing the facility during the construction period are required to be capitalized, as a non-cash transaction, offset by a corresponding facility lease obligation in our consolidated balance sheets. We expect the completion of the facility, including obtaining regulatory approval, to be in 2019. As of December 31, 2018 and 2017, we recorded a construction-in-process asset of $203.9 and $180.6, respectively, and an offsetting facility lease obligation of $155.1 and $159.1, respectively, within other current liabilities and facility lease obligation on our consolidated balance sheets.

Payments to Lonza under the agreement are allocated to the purchases of inventory and the repayment of the facility lease obligation on a relative fair value basis. In 2018, we incurred $73.8 of payments to Lonza under this agreement, of which $9.6 was applied against the outstanding facility lease obligation and $64.2 was recognized as a prepayment of inventory. See Note 11 “Commitments and Contingencies” for minimum fixed payments due under Lonza agreements.

Boston Facility Lease Obligation

In September 2017, we entered into a lease agreement for approximately 150,000 square feet of office space to be constructed in Boston, Massachusetts. Construction of the facility was completed and the building was placed into service in the second quarter 2018. The term of the lease commenced upon the landlord's substantial completion of the facility in the second quarter of 2018 and will expire on the thirteenth anniversary of commencement, with an option to renew for up to an additional ten years. Although we do not legally own the premises, due to our involvement during the construction period, we are deemed to be the owner of the portion of the building that we will lease based on applicable accounting guidance for build-to-suit leases. Accordingly, the landlord's costs of constructing the facility during the construction period were capitalized, as a non-cash transaction, offset by a corresponding facility lease obligation in our consolidated balance sheets.

Interest expense recognized during 2018 was not material. As of December 31, 2018 and December 31, 2017, our total facility lease obligation was $83.6 and $59.6, respectively, recorded within facility lease obligation in our consolidated balance sheets.

Aggregate future minimum non-cancellable commitments under the Boston facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	4.3
2020	6.6
2021	6.7
2022	6.8
2023	7.0
Thereafter	56.7

In January 2019, we adopted a new lease accounting standard. See Note 1 “Business Overview & Summary of Significant Accounting Policies” for an overview of the impact this standard is expected to have on our facility lease obligation balances in 2019.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Commitments

License Agreements

We have entered into a number of license agreements in order to advance and obtain technologies and services related to our business. License agreements generally require us to pay an initial fee and certain agreements call for future payments upon the attainment of agreed upon development and/or commercial milestones. These agreements may also require minimum royalty payments based on sales of products developed from the applicable technologies, if any.

In October 2018, we entered into a collaboration agreement with Dicerna that provides us with exclusive worldwide licenses and development and commercial rights for two preclinical RNA interference (RNAi) subcutaneously delivered molecules for complement-mediated diseases, as well as an exclusive option for other preclinical RNAi molecules for two additional targets within the complement pathway. In addition to the collaboration agreement, we made an equity investment in Dicerna. Under the terms of the agreements, we made an upfront payment of $37.0 for the exclusive licenses and the equity investment. The market value of the equity investment was $10.3 as of the date of acquisition, which we recorded in other assets in our consolidated balance sheets. Due to the early stage of the assets we are licensing, we recorded the upfront license payment of $26.7 as research and development expense during the fourth quarter 2018. In addition, as of December 31, 2018, we could also be required to pay up to approximately $625.0 for option exercise fees and amounts due upon the achievement of specified research, development, regulatory and commercial milestones, as well as royalties on commercial sales.

In December 2017, we entered into a collaboration and license agreement with Halozyme Therapeutics, Inc. that allows us to use drug-delivery technology in the development of subcutaneous formulations for our portfolio of products for up to four targets. Due to the early stage of the assets we are licensing, we recorded expense for the upfront payment of $40.0 during the fourth quarter 2017. In addition, as of December 31, 2018, we could be required to pay an additional $160.0 for each target developed, subject to achievement of specified development, regulatory and sales-based milestones, as well as royalties on commercial sales.

In addition, as of December 31, 2018, we have entered into other license agreements under which we may be required to pay up to an additional $137.2 if certain development, regulatory and commercial milestones are met.

Manufacturing Agreements

We have various manufacturing development and license agreements to support our clinical and commercial product needs.

We rely on Lonza, a third party manufacturer, to produce a portion of commercial and clinical quantities of our commercial products and product candidates. We have various manufacturing and license agreements with Lonza, with remaining total non-cancellable future commitments of approximately $1,084.6. If we terminate certain supply agreements with Lonza without cause, we will be required to pay for product scheduled for manufacture under our arrangement. Under an existing arrangement with Lonza, we also pay Lonza a royalty on sales of SOLIRIS that was manufactured at the ARIMF facility prior to its sale and a payment with respect to sales of SOLIRIS manufactured at Lonza facilities.

In addition to Lonza, as of December 31, 2018, we have non-cancellable commitments of approximately $104.1 through 2020 with other third party manufacturers.

Contingent Liabilities

We are currently involved in various claims, lawsuits and legal proceedings. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, we accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals are based on our best estimates based on information available at the time of the assessment. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims (and offers of settlement), we may reassess the potential liability related to these matters and may revise these estimates, which could result in a material adverse adjustment to our operating results. Costs associated with our involvement in legal proceedings are expensed as incurred. The outcome of any such proceedings, regardless of the merits, is inherently uncertain. If we were unable to prevail in any such proceedings, our consolidated financial position, results of operations, and future cash flows may be materially impacted.

We have received, and may in the future receive, notices from third parties claiming that their patents may be infringed by the development, manufacture or sale of our products. Under the guidance of ASC 450, Contingencies, we record a royalty accrual based on our best estimate of the fair value percent of net sales of our products that we could be required to pay the owners of patents for technology used in the manufacture and sale of our products. A costly license, or inability to obtain a necessary license, could have a material adverse effect on our financial results.

In May 2015, we received a subpoena in connection with an investigation by the Enforcement Division of the SEC requesting information related to our grant-making activities and compliance with the FCPA in various countries. In addition, in October 2015, we received a request from the DOJ for the voluntary production of documents and other information pertaining to Alexion’s compliance with FCPA. The SEC and DOJ also seek information related to Alexion’s recalls of specific lots of SOLIRIS and related securities disclosures. Alexion is cooperating with these investigations.

The investigations have focused on operations in various countries, including Brazil, Colombia, Japan, Russia and Turkey, and Alexion's compliance with the FCPA and other applicable laws.

At this time, Alexion is unable to predict the duration, scope or outcome of these investigations. While it is possible that a loss related to these matters may be incurred, given the ongoing nature of these investigations, management cannot reasonably estimate the potential magnitude of any such loss or range of loss, or the cost of the ongoing investigation. Any determination that our operations or activities are not or were not in compliance with existing laws or regulations could result in the imposition of fines, civil and criminal penalties, equitable remedies, including disgorgement, injunctive relief, and/or other sanctions against us, and remediation of any such findings could have an adverse effect on our business operations.

Alexion is committed to strengthening its compliance program and is currently implementing a comprehensive company-wide transformation plan to enhance and remediate its business processes, structures, controls, training, talent and systems across Alexion’s global operations.

As previously reported, on December 29, 2016, a shareholder filed a putative class action against the Company and certain former employees in the U.S. District Court for the District of Connecticut, alleging that defendants made misrepresentations and omissions about SOLIRIS. On April 12, 2017, the court appointed a lead plaintiff. On July 14, 2017, the lead plaintiff filed an amended putative class action complaint against the Company and seven current or former employees. The complaint alleges that defendants made misrepresentations and omissions about SOLIRIS, including alleged misrepresentations regarding sales practices, management changes, and related investigations, between January 30, 2014 and May 26, 2017, and that the Company's stock price dropped upon the purported disclosure of the misrepresentations. The plaintiffs seek to recover unspecified monetary relief, unspecified equitable and injunctive relief, interest, and attorneys’ fees and costs. Defendants moved to dismiss the amended complaint on September 12, 2017. Plaintiffs filed an opposition to defendants’ motion to dismiss on November 13, 2017, and defendants’ filed a reply brief in further support of their motion on December 28, 2017. Defendants’ motion to dismiss is now fully briefed and pending before the court. Given the early stages of this litigation, an estimate of the possible loss or range of loss cannot be made at this time.

In December 2016, we received a subpoena from the U.S. Attorney's Office for the District of Massachusetts requesting documents relating generally to our support of Patient Services, Inc. (PSI) and National Organization for Rare Disorders (NORD), 501(c)(3) organizations that provide financial assistance to Medicare patients taking drugs sold by Alexion; Alexion’s provision of free drug to Medicare patients; and Alexion compliance policies and training materials concerning the anti-kickback statute and information on donations to PSI and NORD from 2010 through 2016. Other companies have disclosed similar inquiries. We are cooperating with this inquiry. We have been engaged in discussions with the DOJ about a potential resolution of this matter and, in December 2018, we reached an agreement in principle to resolve this matter by entering into a civil settlement agreement with the DOJ and the Office of Inspector General (OIG) of the U.S. Department of Health and Human Services. As part of the proposed resolution, Alexion will pay approximately $13.0 to the DOJ and OIG. While we have reached an agreement in principle, there can be no assurance that the steps necessary to conclusively resolve this matter will be successful or that the settlement terms will be finalized. We are unable to determine when a potential final settlement may be reached. Further, if we are unable to reach a final agreement based on the agreement in principle, we will not be able to predict when these matters will be resolved or what further action, if any, the government will take in connection with them.

In May 2017, Brazilian authorities seized records and data from our Sao Paulo, Brazil offices as part of an investigation being conducted into Alexion’s Brazilian operations. We are cooperating with this inquiry.

In June 2017, we received a demand to inspect certain of our books and records pursuant to Section 220 of the General Corporation Law of the State of Delaware on behalf of a purported stockholder. Among other things, the demand sought to determine whether to institute a derivative lawsuit against certain of the Company’s directors and officers in relation to the investigation by our Audit and Finance Committee announced in November 2016 and the investigations instituted by the SEC, DOJ, U.S. Attorney’s Office for the District of Massachusetts, and Brazilian law enforcement officials that are described above. We have responded to the demand. Given the early stages of this matter, an estimate of the possible loss or range of loss cannot be made at this time.

On September 27, 2017, a hearing panel of the Canadian Patented Medicine Prices Review Board (PMPRB) issued a decision in a previously pending administrative pricing matter that we had excessively priced SOLIRIS in a manner inconsistent with the Canadian pricing rules and guidelines. In its decision, the PMPRB ordered Alexion to decrease the price of SOLIRIS to an upper limit based upon pricing in certain other countries, and to forfeit excess revenues for the period between 2009 and 2017. The amount of excess revenues was not determined to be a material amount. In October 2017, Alexion filed an application for judicial review of the PMPRB’s decision in the Federal Court of Canada. The hearing of that application for judicial review took place on November 15 and 16, 2018 but a decision on this matter has not yet been delivered by the Court. At this time, we cannot predict the outcome of these judicial review proceedings or any appeals that may follow and cannot reasonably estimate the amount of any additional forfeitures that will be required to be made or the potential impact to future SOLIRIS revenues in Canada relating to any potential future price reduction.

In October 2018, the Japanese Ministry of Health, Labour and Welfare (MHLW) conducted an administrative inspection of Alexion’s Japanese operations. The MHLW inquiry has been primarily focused on our communication efforts regarding the proper use of SOLIRIS in Japan for aHUS, among other matters. We have cooperated, and will continue to cooperate, with this inquiry. An estimate of the possible loss or range of loss, or what further action, if any, the MHLW will take in connection with this matter, cannot be made at this time.

Chugai Pharmaceutical Co., Ltd. has filed two lawsuits against Alexion. The first was filed in November 2018 in the United States District Court for the District of Delaware against Alexion Pharmaceuticals, Inc. alleging that ULTOMIRIS infringes one U.S. patent held by Chugai Pharmaceutical Co., Ltd. The second lawsuit was filed in December 2018 in the Tokyo District Court against Alexion Pharma GK (a wholly-owned subsidiary of Alexion) in Japan and alleges that ULTOMIRIS infringes two Japanese patents held by Chugai Pharmaceutical Co., Ltd. Chugai’s complaints seek unspecified damages and certain injunctive relief. Alexion has filed an answer to the U.S. complaint that denies infringement. In addition, Alexion has raised defenses and has brought several counterclaims against Chugai Pharmaceutical Co., Ltd. that request a finding of non-infringement and patent invalidity. Alexion Pharma GK responded to Chugai at the Tokyo District Court and raised defenses against Chugai Pharmaceutical Co., Ltd. that request a finding of non-infringement and patent invalidity. Given the early stages of these litigations, an estimate of the possible loss or range of loss cannot be made at this time.

Operating Leases

As of December 31, 2018, we have operating leases for office and laboratory space in U.S. and foreign locations to support our operations as a global organization.

Aggregate lease expense was $24.4, $27.2 and $29.3 for the years ended December 31, 2018, 2017 and 2016, respectively. Lease expense is being recorded on a straight-line basis over the applicable lease terms.

Aggregate future minimum annual rental payments, for the next five years and thereafter under non-cancellable operating leases (including facilities and equipment) as of December 31, 2018 are:



Year
2019	$	14.1
2020	9.3
2021	5.6
2022	3.9
2023	3.5
Thereafter	11.6

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

The income tax expense is based on income before income taxes as follows:



	Year Ended December 31,
	2018			2017			2016
U.S.	$	(451.4	)	$	(43.9	)	$	(164.6	)
Non-U.S.	693.6			591.7			740.8
	$	242.2		$	547.8		$	576.2

During the fourth quarter of 2013, in connection with the centralization of our global supply chain and technical operations in Ireland, our U.S. parent company became a direct partner in a captive foreign partnership. The partnership income, which is derived in foreign jurisdictions, is classified as “non-U.S. income” for purposes of financial reporting. Substantially all non-U.S. income relates to income from our captive foreign partnership.

The components of the income tax expense are as follows:



	Year Ended December 31,
	2018			2017			2016
Domestic
Current	$	57.0		$	42.9		$	3.4
Deferred	49.5			7.2			107.6
	106.5			50.1			111.0
Foreign
Current	74.7			107.5			69.1
Deferred	(16.6		)	(53.1		)	(3.3		)
	58.1			54.4			65.8
Total
Current	131.7			150.4			72.5
Deferred	32.9			(45.9		)	104.3
	$	164.6		$	104.5		$	176.8

We continue to pay cash taxes in U.S. Federal, various U.S. state, and foreign jurisdictions where we have utilized all of our tax attributes or have met the applicable limitation for attribute utilization.

Effective Tax Rate

The provision (benefit) for income taxes differs from the U.S. federal statutory tax rate. The reconciliation of the statutory U.S. federal income tax rate to our effective income tax rate is as follows:



	Year Ended December 31,
	2018		2017		2016
U.S. federal statutory tax rate	21.0	%	35.0	%	35.0	%
Benefit of foreign earnings	(71.2	)%	60.1	%	(7.2	)%
Tax credits	(17.0	)%	(10.7	)%	(6.0	)%
Tax reserves	12.1	%	(14.0	)%	2.7	%
Re-measurement of deferred taxes as a result of the Tax Act	—	%	(53.4	)%	—	%
Acquired in-process research & development	102.6	%	—	%	—	%
U.S. state taxes	14.2	%	1.5	%	4.1	%
Other permanent differences	6.3	%	0.6	%	2.1	%

Effective Income Tax Rate	68.0	%	19.1	%	30.7	%

In our reconciliation of our statutory U.S. federal income tax rate to our effective tax rate above, we have included a Benefit of foreign earnings amount which encapsulates the various tax impacts that result from our foreign derived income. As a result of U.S. Tax Reform, a substantial portion of our foreign earnings are subject to the GILTI minimum tax at an effective rate which is lower than the U.S. statutory tax rate of 21.0%. While we are also subject to tax in foreign jurisdictions locally, substantially all of these taxes are creditable against U.S. taxes imposed on foreign earnings. As a result, the effective tax rate on our foreign earnings is lower than the U.S. statutory rate.

In the year ended December 31, 2018, the Benefit of foreign earnings includes foreign local tax expense of $58.1, substantially all of which is offset by the benefit from U.S. foreign tax credits of $54.2, resulting in a net increase to the effective tax rate of 1.6%. We incurred U.S. tax expense on our foreign earnings of $206.1, which includes GILTI minimum tax. The U.S. tax on our foreign earnings reflects a benefit of $108.7 or 44.8%, primarily related to the Section 250(a) deduction, compared to the U.S. statutory rate. Also included in this component is a benefit of $67.7 from adjustments to 2018 provisional accounting for the Tax Act, which resulted in a decrease to our effective tax rate of approximately 28.0%.

In the year ended December 31, 2017, the Benefit of foreign earnings includes foreign local tax expense of $54.4 partially offset by the benefit from U.S. foreign tax credits of $33.2, resulting in a net increase to the effective tax rate of 3.9%. We incurred transition tax imposed by the Tax Act of $177.9 and US deferred taxes related to the GILTI provisions of the Tax Act of $165.4. These Tax Act-related adjustments resulted in an increase to our effective tax rate of approximately 62.7%. Additional U.S. tax imposed on our foreign earnings of $171.7 reflects a benefit of $35.4 or 6.5% compared to the U.S. statutory rate.

In the year ended December 31, 2016 the Benefit of foreign earnings includes foreign local tax expense of $42.8, more than offset by the benefit from U.S. foreign tax credits of $48.3, resulting in a net decrease to the effective tax rate of 0.9%. Additional U.S. tax imposed on our foreign earnings of $103.9 reflects a benefit of $155.4 or 27.0% compared to the U.S. statutory rate. Also included in this component is the impact to deferred tax attributable to distributions from our captive foreign partnership of $119.3, which increased the effective tax rate by 20.7%.

The effective tax rate reconciliation includes the tax impact of acquisitions of IPR&D assets. Absent successful clinical results and regulatory approval, there is no alternative use for certain acquired IPR&D assets. An increase to the effective tax rate results when the value of such assets are expensed, and no tax benefit is recognized. In the year ended December 31, 2018, this component of the effective tax rate includes an increase to tax expense of $248.4 related to the acquired IPR&D costs for the acquisitions of Wilson Therapeutics and Syntimmune, which increased our effective tax rate by 69.7% and 32.9%, respectively.

In the year ended December 31, 2018, Other permanent differences includes tax expense of $21.1 or 8.7% related to nondeductible compensation and tax benefit of $10.9 or 4.5% related to Foreign-Derived Intangible Income.

In 2017, we concluded the IRS examination of our 2013 and 2014 tax years. Conclusion of the IRS examination resulted in a decrease to the tax reserves component of the 2017 effective tax rate of approximately 3.6%.

The Tax Act

In December 2017, the Tax Cuts and Jobs Act (Tax Act) was enacted into law. The Tax Act decreased the US federal corporate tax rate to 21.0%, imposed a minimum tax on foreign earnings related to intangible assets (GILTI), a one-time transition tax on previously unremitted foreign earnings, and modified the taxation of other income and expense items. With regard to the GILTI minimum tax, foreign earnings are reduced by the profit attributable to tangible assets and a deductible allowance of up to 50.0%, subject to annual limitations. We have elected to account for the impact of the minimum tax in deferred taxes.

At December 31, 2017, the Tax Act resulted in an increase to tax expense and the effective tax rate of $45.8 and 8.4%, respectively:


(a)	Income tax expense increased $177.9 or 32.5% related to the transition tax on unremitted earnings imposed by the Tax Act. This increase includes foreign income subject to US tax of $195.6, partially offset by a related benefit of foreign tax credits of $17.7.


(b)	The decrease to the U.S. federal tax rate resulted in a decrease to deferred tax expense of $292.4 or 53.4%. This decrease includes the $121.3 or 22.2% benefit of re-measuring domestic deferred taxes and an additional decrease attributable to re-measuring deferred taxes on foreign earnings of $171.1 or 31.2%.


(c)	Other permanent differences includes a decrease to tax expense of $5.1 or 0.9% related to the re-measurement of income taxes payable as a result of changes in U.S. federal tax rates under the Tax Act.


(d)	The enactment of the GILTI minimum tax increased US deferred taxes on foreign earnings $165.4 or 30.2%. This increase includes deferred tax expense related to the GILTI minimum tax of $236.9. This deferred expense is partially offset by a related decrease to deferred expense for the release of reserves for uncertain tax positions of $71.5.

We calculated provisional amounts for the tax effects of the Tax Act that could be reasonably estimated, but not completed, in our results for the year ended December 31, 2017. As of the fourth quarter 2018 we had completed our analysis of all provisional estimates, and concluded as follows:

(a)

We calculated a reasonable estimate of the one-time transition tax on previously unremitted earnings, which resulted in an increase to U.S. Federal tax expense of $177.9 and an increase to taxes payable, net of tax credits, of $28.0 in the period ended December 31, 2017. Our initial accounting for the transition tax was not complete as of December 31, 2017 because there was uncertainty regarding the calculation of the amounts subject to the tax. We completed our analysis of the transition tax and related interpretive guidance during the third quarter 2018. No significant measurement period adjustment to our initial accounting was required.

(b)

We calculated a reasonable estimate of the impact of the GILTI minimum tax on deferred taxes, which resulted in an increase to U.S. Federal tax expense and the deferred tax liability of $236.9 in the period ended December 31, 2017. Our initial accounting for the minimum tax was incomplete because there was uncertainty regarding the calculation of the temporary differences subject to the minimum tax. We completed our analyses of these temporary differences and the expected timing and manner of their reversal during the fourth quarter 2018. We recorded measurement period adjustments during 2018 which resulted in a decrease to U.S. federal tax expense of $67.7.

(c)

We calculated a reasonable estimate of the Tax Act’s limits on deductions for employee remuneration, including remuneration in kind, which resulted in an insignificant impact to tax expense, taxes payable, and deferred taxes in the period ended December 31, 2017. Our initial accounting for these limits was incomplete because there was uncertainty regarding the value of the deduction-limited remuneration. We completed our analysis of the relevant employee remuneration arrangements during the third quarter 2018. No measurement period adjustment to our initial accounting was required.

(d)

We calculated a reasonable estimate of the impact of the Tax Act to U.S. state income taxes, which resulted in an increase to tax expense, taxes payable, and deferred taxes of $2.9, $2.2, and $0.7, respectively, in the period ended December 31, 2017. We interpreted the effect of the Tax Act's changes to federal law on each U.S. state's system of taxation as of the date of enactment. We completed additional analysis of the effect of modifications to federal deductions and income inclusions on U.S. state tax systems in the fourth quarter 2018. No measurement period adjustment to our initial accounting was required.

(e)

We calculated the deferred tax liability related to our foreign captive partnership in the period ended December 31, 2017 consistent with our calculation in periods prior to enactment of the Tax Act. As a result, the deferred tax liability we recorded as of December 31, 2017 of $533.4 related to our foreign captive partnership was provisional. We completed additional analysis of the direct and indirect effects of the Tax Act during the fourth quarter 2018. We recorded measurement period adjustments during 2018 which resulted in an increase to U.S. state income tax expense and deferred taxes of $11.1.

Deferred Taxes

Provisions have been made for deferred taxes based on the differences between the basis of the assets and liabilities for financial statement purposes and the basis of the assets and liabilities for tax purposes using currently enacted tax rates and regulations that will be in effect when the differences are expected to be recovered or settled. The components of the deferred tax assets and liabilities are as follows:



	December 31,			December 31,
	2018			2017
Deferred tax assets:
Net operating losses	$	41.8		$	4.9
Income tax credits	371.6			442.5
Stock compensation	47.6			66.6
Accruals and allowances	105.8			97.7
Unrealized losses	—			6.6
Research and development expenses	5.2			7.2
Accrued royalties	89.1			74.2
	661.1			699.7
Valuation allowance	(19.6		)	(3.4		)
Total deferred tax assets	641.5			696.3
Deferred tax liabilities:
Depreciable assets	(88.7		)	(75.2		)
Unrealized gains	(6.6		)	—
Investment in foreign partnership	(566.6		)	(607.9		)
Intangible assets	(268.8		)	(285.6		)
Total deferred tax liabilities	(930.7		)	(968.7		)
Net deferred tax (liability) asset	$	(289.2	)	$	(272.4	)

At December 31, 2018, we have tax effected federal and state net operating loss carryforwards of $20.0 and $11.6, respectively. Our net operating losses expire between 2022 and 2038. We also have federal and state income tax credit carryforwards of $370.6 and $8.4, respectively. These income tax credits expire between 2025 and 2038.

The increase in our net operating losses is due to the acquisition of Syntimmune and the recognition of historical net operating loss carryforwards which are subject to annual utilization limitations in accordance with Section 382 of the Internal Revenue Code. The decrease in income tax credits is attributable to the utilization of Orphan Drug credits. The decrease in our investment in foreign partnership deferred tax liability is due to adjustments we recorded in 2018 to our provisional accounting for the Tax Act and the reversal of other component temporary differences. We continue to maintain a valuation allowance against certain deferred tax assets where realization is not certain.

Included in our investment in foreign partnership above is $(24.1) associated with GILTI minimum tax. Our accounting for the GILTI minimum tax on our captive foreign partnership as a result of the Tax Act was provisional at December 31, 2017. We completed our accounting for the Tax Act in the fourth quarter 2018.

Unrecognized Tax Benefits

We follow authoritative guidance regarding accounting for uncertainty in income taxes, which prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The interpretation also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosures, and transition.

The beginning and ending amounts of unrecognized tax benefits reconciles as follows:



	2018			2017			2016
Beginning of period balance	$	60.9		$	138.9		$	113.9
Increases for tax positions taken during a prior period	9.1			5.6			3.4
Decreases for tax positions taken during a prior period	(5.8		)	(85.8		)	(1.1		)
Increases for tax positions taken during the current period	28.8			19.3			22.8
Decreases for tax positions related to settlements	—			(15.8		)	—
Decreases for tax positions related to lapse of statute	(0.3		)	(1.3		)	(0.1		)
	$	92.7		$	60.9		$	138.9

The total amount of accrued interest and penalties was not significant as of December 31, 2018. The total amount of tax benefit recorded during 2018, 2017, and 2016 which related to unrecognized tax benefits was $35.4, $27.1, and $21.5, respectively. All of our unrecognized tax benefits, if recognized, would have a favorable impact on the effective tax rate.

It is reasonably possible that a portion of our unrecognized tax benefits could reverse within the next twelve months. Reversal of these amounts is contingent upon the completion of field audits by the taxing authorities in several jurisdictions, whether a tax adjustment is proposed, the nature and amount of any adjustment, and the administrative path to resolving the proposed adjustment. We cannot reasonably estimate the range of the potential change.

Tax Audits

We file federal and state income tax returns in the U.S. and in numerous foreign jurisdictions. The U.S. and foreign jurisdictions have statutes of limitations ranging from 3 to 6 years. However, the limitation period could be extended due to our tax attribute carryforward position in a number of our jurisdictions. The tax authorities generally have the ability to review income tax returns for periods where the limitation period has previously expired and can subsequently adjust tax attribute values.

In 2017, the IRS commenced an examination of our U.S. income tax returns for 2015. We anticipate this audit will conclude within the next twelve months. We have not been notified of any significant adjustments proposed by the IRS.

Undistributed Earnings

We have recorded tax on the undistributed earnings of our controlled foreign corporation (CFC) subsidiaries. To the extent CFC earnings may not be repatriated to the U.S. as a dividend distribution due to limitations imposed by law, we have not recorded the related potential withholding, foreign local, and U.S. state income taxes.

Share-based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-based Compensation

2017 Incentive Plan

The 2017 Plan was approved by our stockholders in May 2017 and replaced the 2004 Plan effective May 10, 2017. The 2017 Plan is a broad based plan that provides for the grant of equity awards including restricted stock and restricted stock units (collectively referred to as Restricted Stock), incentive and non-qualified stock options, and other stock-related awards to our directors, officers, key employees and consultants, for up to a maximum of 18.2 shares in addition to awards outstanding under the 2004 Incentive Plan on or after March 14, 2017 that are subsequently canceled, cash settled, expired, forfeited, or otherwise terminated without the delivery of such shares, subject to the limitations in the 2017 Plan. Stock options granted under the 2017 Plan have a maximum contractual term of ten years from the date of grant, have an exercise price not less than the fair value of the stock on the grant date and generally vest over four years. Restricted Stock awards also generally vest over four years, with performance-based restricted stock units having a three-year vesting period.

Stock Options

A summary of the status of our stock options at December 31, 2018, and changes during the year then ended is presented in the table and narrative below:



	Number of shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2017	5.3		$	124.71
Granted	—		—
Exercised	(0.5	)	82.70
Forfeited and canceled	(1.2	)	156.20
Outstanding at December 31, 2018	3.6		$	119.68	4.74	$	44.5
Vested and unvested expected to vest at December 31, 2018	3.6		$	119.63	4.73	$	44.5
Exercisable at December 31, 2018	3.2		$	117.73	4.38	$	44.5

Total intrinsic value of stock options exercised during the years ended December 31, 2018, 2017 and 2016 was $27.5, $88.9 and $41.7, respectively. We primarily utilize newly issued shares to satisfy the exercise of stock options. The total fair value of options vested during the years ended December 31, 2018, 2017 and 2016 was $27.2, $61.5 and $58.1, respectively.

We did not grant any stock options during the year ended December 31, 2018. For the years ended December 31, 2017 and 2016, the fair value of options at the date of grant was estimated using the Black-Scholes model with the following ranges of weighted average assumptions:



	December 31,	December 31,
	2017	2016
Expected life in years	4.07 - 4.29	3.82 - 6.29
Interest rate	1.64% - 1.92%	0.87% - 1.66%
Volatility	38.78% - 39.01%	33.45% - 37.61%
Dividend yield	—	—

The expected stock price volatility rates are based on historical volatilities of our common stock. The risk-free interest rates are based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option. The average expected life represents the weighted average period of time that options granted are expected to be outstanding. We have evaluated three distinct employee groups in determining the expected life assumptions, and we estimate the expected life of stock options based on historical experience of exercises, cancellations and forfeitures of our stock options.

The weighted average fair value at the date of grant for options granted during the years ended December 31, 2017 and 2016 was $42.59 and $41.46 per option, respectively.

Restricted Stock

A summary of the status of our nonvested Restricted Stock at December 31, 2018 and changes during the year then ended is as follows:



	Number of Shares		Weighted Average Grant Date Fair Value
Nonvested Restricted Stock at December 31, 2017	3.6		$	130.75
Shares granted	2.1		119.27
Shares forfeited	(0.7	)	126.78
Shares vested	(1.3	)	135.17
Nonvested Restricted Stock at December 31, 2018	3.7		$	123.25

The fair value of Restricted Stock at the date of grant is based on the fair market value of the shares of common stock underlying the awards on the date of grant. The weighted average fair value at the date of grant for Restricted Stock awards granted during the years ended December 31, 2018, 2017 and 2016, including restricted stock units with performance conditions, was $119.27, $125.39 and $133.35 per share, respectively. The total fair value of Restricted Stock vested during the years ended December 31, 2018, 2017 and 2016 was $181.7, $157.0 and $124.4, respectively.

Included in the table above is 0.3 shares granted to senior management with market-based performance conditions which provide the recipient the right to receive restricted stock at the end of a three year performance period, based on pre-established market-based performance goals. We used payout simulation models to estimate the grant date fair value of these awards at $123.25. Expense recognized for awards with market-based performance conditions was $14.9 for the year ended December 31, 2018 and immaterial for the years ended December 31, 2017 and 2016.

Employee Stock Purchase Plan

During 2015, the Company adopted the ESPP under which employees can purchase shares of our common stock based on a percentage of their compensation subject to certain limits. The purchase price per share is equal to the lower of 85.0% of the fair market value of our common stock on the offering date or the purchase date with a six month look-back feature. Under the ESPP, up to 1.0 shares of common stock may be issued to eligible employees who elect to participate in the purchase plan. Shares issued and compensation expense recognized under the ESPP for the years ended December 31, 2018, 2017 and 2016 were not material.

Share-Based Compensation Expense

The following table summarizes the share-based compensation expense in the consolidated statements of operations:



	Year Ended December 31,
	2018			2017			2016
Cost of sales	$	16.0		$	11.1		$	11.1
Research and development	57.5			76.4			57.6
Selling, general and administrative	129.5			155.6			123.6
Total share-based compensation expense	203.0			243.1			192.3
Income tax effect	(46.5		)	(89.3		)	(70.3		)
Total share-based compensation expense, net of tax	$	156.5		$	153.8		$	122.0

Share-based compensation expense capitalized to inventory during the years ended December 31, 2018, 2017 and 2016 was $14.5, $15.4, and $12.1, respectively.

As of December 31, 2018, there was $312.7 of total unrecognized share-based compensation expense related to non-vested share-based compensation arrangements granted under our share-based compensation plans. The expense is expected to be recognized over a weighted-average period of 1.70 years.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2018
Common and Preferred Stock [Abstract]
Stockholders' Equity	Stockholders’ Equity Share Repurchases In November 2012, our Board of Directors authorized a share repurchase program. The repurchase program does not have an expiration date, and we are not obligated to acquire a particular number of shares. The repurchase program may be discontinued at any time at the Company’s discretion. In February 2017, our Board of Directors increased the amount that we are authorized to expend on future repurchases to $1,000 under the repurchase program, which superseded all prior repurchase programs. The repurchase program does not have an expiration date. The repurchase program may be discontinued at any time at our discretion. Under the program, we repurchased 0.7 and 4.0 shares of our common stock at a cost of $85.0 and $463.6 during the years ended December 31, 2018 and 2017, respectively. As of February 6, 2019, there is a total of $451.5 remaining for repurchases under the repurchase program.

Other Comprehensive Income and Accumulated Other Comprehensive Income (Notes)

12 Months Ended

Dec. 31, 2018

Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract]

Other Comprehensive Income and Accumulated Other Comprehensive Income

The following table summarizes the changes in AOCI, by component, for the years ended December 31, 2018, 2017 and 2016:



	Defined Benefit Pension Plans			Unrealized Gains (Losses) from Debt Securities			Unrealized Gains (Losses) from Hedging Activities			Foreign Currency Translation Adjustment			Total Accumulated Other Comprehensive Income (Loss)
Balances, December 31, 2015	$	(9.6	)	$	(0.8	)	$	92.7		$	(20.0	)	$	62.3
Other comprehensive income before reclassifications	2.6			0.2			46.4			(4.3		)	44.9
Amounts reclassified from other comprehensive income	0.3			0.2			(47.2		)	—			(46.7		)
Net other comprehensive income (loss)	2.9			0.4			(0.8		)	(4.3		)	(1.8		)
Balances, December 31, 2016	$	(6.7	)	$	(0.4	)	$	91.9		$	(24.3	)	$	60.5
Other comprehensive income before reclassifications	0.5			(0.2		)	(88.2		)	8.4			(79.5		)
Amounts reclassified from other comprehensive income	1.4			0.8			(17.6		)	—			(15.4		)
Net other comprehensive income (loss)	1.9			0.6			(105.8		)	8.4			(94.9		)
Balances, December 31, 2017	$	(4.8	)	$	0.2		$	(13.9	)	$	(15.9	)	$	(34.4	)
Other comprehensive income before reclassifications	1.5			0.1			32.9			(0.5		)	34.0
Amounts reclassified from other comprehensive income	0.7			(0.6		)	(9.4		)	—			(9.3		)
Net other comprehensive income (loss)	2.2			(0.5		)	23.5			(0.5		)	24.7
Balances, December 31, 2018	$	(2.6	)	$	(0.3	)	$	9.6		$	(16.4	)	$	(9.7	)

The table below provides details regarding significant reclassifications from AOCI during the years ended December 31, 2018, 2017 and 2016:



Details about Accumulated Other Comprehensive Income Components	Amount Reclassified From Accumulated Other Comprehensive Income during the year ended December 31,									Affected Line Item in the Consolidated Statements of Operations
	2018			2017			2016
Unrealized Gains (Losses) on Hedging Activity
Effective portion of foreign exchange contracts	$	(1.8	)	$	28.9		$	73.0		Net product sales
Effective portion of interest rate swap contracts	13.6			(1.8		)	(0.2		)	Interest expense
	11.8			27.1			72.8
	(2.4		)	(9.5		)	(25.6		)	Income tax expense
	$	9.4		$	17.6		$	47.2
Defined Benefit Pension Items
Amortization of prior service costs and actuarial losses	$	(0.3	)	$	(0.4	)	$	(0.5	)	^(a)
Curtailment	(0.6		)	(1.8		)	—			^(a)
	(0.9		)	(2.2		)	(0.5		)
	0.2			0.8			0.2			Income tax expense
	$	(0.7	)	$	(1.4	)	$	(0.3	)

(a) This AOCI component is included in the computation of net periodic pension benefit cost (see Note 17, Employee Benefit Plans, for additional details).

Fair Value Measurement

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurement

Authoritative guidance establishes a valuation hierarchy for disclosure of the inputs to the valuation used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value.

The following tables present information about our assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2018 and 2017, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value.



		Fair Value Measurement at December 31, 2018
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Money market funds	$	569.4	$	—	$	569.4	$	—
Cash equivalents	Commercial paper	$	35.4	$	—	$	35.4	$	—
Cash equivalents	Corporate bonds	$	0.2	$	—	$	0.2	$	—
Cash equivalents	Other government-related obligations	$	8.2	$	—	$	8.2	$	—
Marketable securities	Mutual funds	$	16.5	$	16.5	$	—	$	—
Marketable securities	Commercial paper	$	16.7	$	—	$	16.7	$	—
Marketable securities	Corporate bonds	$	122.6	$	—	$	122.6	$	—
Marketable securities	Other government-related obligations	$	9.3	$	—	$	9.3	$	—
Marketable securities	Bank certificates of deposit	$	33.2	$	—	$	33.2	$	—
Other assets	Equity securities	$	90.8	$	8.9	$	81.9	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	40.5	$	—	$	40.5	$	—
Other assets	Foreign exchange forward contracts	$	0.3	$	—	$	0.3	$	—
Other current liabilities	Foreign exchange forward contracts	$	18.8	$	—	$	18.8	$	—
Other liabilities	Foreign exchange forward contracts	$	3.1	$	—	$	3.1	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	20.1	$	—	$	20.1	$	—
Other current liabilities	Interest rate contracts	$	0.8	$	—	$	0.8	$	—
Other liabilities	Interest rate contracts	$	17.3	$	—	$	17.3	$	—
Current portion of contingent consideration	Acquisition-related contingent consideration	$	97.6	$	—	$	—	$	97.6
Contingent consideration	Acquisition-related contingent consideration	$	183.2	$	—	$	—	$	183.2



		Fair Value Measurement at December 31, 2017
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Commercial paper	$	9.5	$	—	$	9.5	$	—
Cash equivalents	Reverse repurchase agreements	$	27.0	$	—	$	27.0	$	—
Cash equivalents	Corporate bonds	$	1.2	$	—	$	1.2	$	—
Cash equivalents	Other government-related obligations	$	5.0	$	—	$	5.0	$	—
Marketable securities	Mutual funds	$	18.5	$	18.5	$	—	$	—
Marketable securities	Commercial paper	$	6.5	$	—	$	6.5	$	—
Marketable securities	Corporate bonds	$	431.3	$	—	$	431.3	$	—
Marketable securities	Other government-related obligations	$	421.3	$	—	$	421.3	$	—
Marketable securities	Bank certificates of deposit	$	11.8	$	—	$	11.8	$	—
Marketable securities	Equity securities	$	0.3	$	0.3	$	—	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	22.9	$	—	$	22.9	$	—
Other assets	Foreign exchange forward contracts	$	4.1	$	—	$	4.1	$	—
Other current liabilities	Foreign exchange forward contracts	$	48.5	$	—	$	48.5	$	—
Other liabilities	Foreign exchange forward contracts	$	26.0	$	—	$	26.0	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	9.3	$	—	$	9.3	$	—
Other assets	Interest rate contracts	$	12.5	$	—	$	12.5	$	—
Contingent consideration	Acquisition-related contingent consideration	$	168.9	$	—	$	—	$	168.9

There were no securities transferred between Level 1, 2 and 3 during the year ended December 31, 2018.

Valuation Techniques

We classify mutual fund investments and equity securities, which are valued based on quoted market prices in active markets with no valuation adjustment, as Level 1 assets within the fair value hierarchy.

Cash equivalents and marketable securities classified as Level 2 within the valuation hierarchy consist of commercial paper, reverse repurchase agreements, U.S. and foreign government-related debt, corporate debt securities and certificates of deposit. We estimate the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for similar securities, issuer credit spreads, benchmark yields, and other observable inputs. We validate the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.

Other investments in equity securities of publicly traded companies which are subject to holding period restrictions are carried at fair value using an option pricing valuation model and classified as Level 2 equity securities within the fair value hierarchy. The most significant assumptions within the option pricing valuation model are the term of the restrictions and the stock price volatility, which is based upon the historical volatility of similar companies. We also use a constant maturity risk-free interest rate to match the remaining term of the restrictions on such investments.

Our derivative assets and liabilities include foreign exchange and interest rate derivatives that are measured at fair value using observable market inputs such as forward rates, interest rates, our own credit risk as well as an evaluation of our counterparties’ credit risks. Based on these inputs, the derivative assets and liabilities are classified within Level 2 of the valuation hierarchy.

Contingent consideration liabilities related to acquisitions are classified as Level 3 within the valuation hierarchy and are valued based on various estimates, including probability of success, discount rates and amount of time until the conditions of the milestone payments are met.

As of December 31, 2018, there has not been any impact to the fair value of our derivative liabilities due to our own credit risk. Similarly, there has not been any significant adverse impact to our derivative assets based on our evaluation of our counterparties’ credit risks.

Contingent Consideration

In connection with prior business combinations, we may be required to pay future consideration that is contingent upon the achievement of specified development, regulatory approvals or sales-based milestone events. We determine the fair value of these obligations using various estimates that are not observable in the market and represent a Level 3 measurement within the fair value hierarchy. The resulting probability-weighted cash flows were discounted using a cost of debt ranging from 4.2% to 5.1% for developmental milestones and a weighted average cost of capital ranging from 9.0% to 21.0% for sales-based milestones.

Each reporting period, we adjust the contingent consideration to fair value with changes in fair value recognized in operating earnings. Changes in fair values reflect new information about the probability and timing of meeting the conditions of the milestone payments. In the absence of new information, changes in fair value will only reflect the interest component of contingent consideration related to the passage of time.

As of December 31, 2018, estimated future contingent milestone payments related to prior business combinations range from zero if no milestone events are achieved, to a maximum of $702.0 if all development, regulatory and sales-based milestones are reached. As of December 31, 2018, the fair value of acquisition-related contingent consideration was $280.8. The following table represents a roll-forward of our acquisition-related contingent consideration:



	2018
Balance at beginning of period	$	168.9
Amounts derecognized upon sale of asset	(4.6		)
Changes in fair value	116.5
Balance at end of period	$	280.8

In September 2018, we sold all our assets, rights and obligations related to the ALXN1101 program to a third party and, as a result, in the quarter ended September 30, 2018, derecognized $4.6 of contingent consideration due under our prior purchase agreement with Orphatec Pharmaceuticals GmbH, dated February 8, 2011. The definitive agreement related to our sale of ALXN1101 provides for contingent consideration payments to Alexion upon the achievement of various regulatory and commercial milestones and other events, as well as royalties on commercial sales. The amount of contingent consideration related to these contingent payments is deemed to be fully constrained as of December 31, 2018, and therefore has not been included in the transaction price. During the third quarter 2018, we recognized an immaterial gain on the sale of ALXN1101 within operating income.

In September 2018, we amended the terms of certain contingent milestone payments due under our prior merger agreement with Enobia Pharma Corp., dated December 28, 2011. The agreement removed our obligations with respect to a regulatory milestone and redistributed the contingent payment associated with this milestone to various sales milestones. As a result of this agreement and the probability of achieving the various sales milestones, our contingent consideration liability increased by $48.7 in the third quarter 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Employee Benefit Plans

12 Months Ended

Dec. 31, 2018

Retirement Benefits [Abstract]

Employee Benefit Plans

Deferred Compensation Plan

We have a nonqualified deferred compensation plan which allows certain highly-compensated employees to make voluntary deferrals of up to 80% of their base salary and incentive bonuses. The plan is designed to work in conjunction with the 401(k) plan and provides for a total combined employer match of up to 6% of an employee’s eligible earnings, up to the IRS annual 401(k) contribution limitations. Deferred compensation amounts under this plan as of December 31, 2018 and 2017 were $16.5 and $18.5, respectively, and are included in other liabilities within the consolidated balance sheets. Employer matching contributions under the plan for the years ended December 31, 2018, 2017 and 2016 were not material.

Defined Contribution Plan

We have one qualified 401(k) plan covering all eligible employees. Under the plan, employees may contribute up to the statutory allowable amount for any calendar year. We make matching contributions equal to $1.00 for each dollar contributed up to the first 6% of an individual’s base salary and incentive cash bonus up to the annual IRS maximum. For the years ended December 31, 2018, 2017 and 2016, we recorded matching contributions of approximately $14.1, $15.9, and $16.7 respectively.

Defined Benefit Plans

We maintain defined benefit plans for employees in certain countries outside the U.S., including retirement benefit plans required by applicable local law. The plans are valued by independent actuaries using the projected unit credit method. The liabilities correspond to the projected benefit obligations of which the discounted net present value is calculated based on years of employment, expected salary increases, and pension adjustments.

In 2018 and 2017 we recorded the impacts of a curtailment related to our Swiss plan as a result of a reduction of employees due to restructuring events as discussed in Note 18, “Restructuring and Related Expenses”.

The following table sets forth the funded status and the amounts recognized for defined benefit plans, including the impacts of the curtailments:



	December 31,
	2018			2017
Change in benefit obligation:
Projected benefit obligation, beginning of year	$	43.4		$	48.4
Service cost	6.3			7.8
Curtailment	(3.8		)	(9.6		)
Other	(6.5		)	(3.2		)
Projected benefit obligation, end of year	$	39.4		$	43.4
Accumulated benefit obligation, end of year	$	36.1		$	39.4



	December 31,
	2018			2017
Change in plan assets:
Fair value of plan assets, beginning of year	$	24.2		$	28.2
Employer contributions	3.0			4.3
Plan participants' contributions	1.3			1.5
Curtailment	(2.4		)	(6.6		)
Other	(4.3		)	(3.2		)
Fair value of plan assets, end of year	$	21.8		$	24.2
Funded status at end of year	$	(17.6	)	$	(19.2	)

The Company measures the fair value of plan assets based on the prices that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. All plan asset investments are classified as Level 2 within the fair value hierarchy and are valued utilizing observable prices for similar instruments and quoted prices for identical or similar instruments in markets that are not active. Plan assets are managed by an independent investment fiduciary and are primarily invested in debt and equity securities and real estate funds in order to maximize the overall return from investment income considering asset allocation limits as determined by pension law.

At December 31, 2018, we have recorded a liability of $17.6 in other noncurrent liabilities and an additional minimum liability of $2.6, net of tax, to accumulated other comprehensive income.

The following table provides the weighted average assumptions used to calculate net periodic benefit cost and the actuarial present value of projected benefit obligations:



	December 31,
	2018		2017
Weighted average assumptions - Net Periodic Benefit Cost:
Discount rate	0.8	%	0.7	%
Long term rate of return on assets	2.5	%	3.0	%
Rate of compensation increase	1.3	%	1.4	%
Weighted average assumptions - Projected Benefit Obligation:
Discount Rate	0.8	%	0.8	%
Rate of compensation increase	1.3	%	1.3	%

The discount rates used to determine the net periodic benefit cost and projected benefit obligation represent the yield on high quality AA-rated corporate bonds for periods that match the duration of the benefit obligations.

The expected long-term rate of return on plan assets represents a weighted average of expected returns per asset category. The rate of return considers historical and estimated future risk free rates of return as well as risk premiums for the relevant investment categories.

The components of net periodic benefit cost are as follows:



	Year Ended December 31,
	2018			2017			2016
Service cost	$	6.3		$	7.8		$	8.2
Employee contributions	(1.3		)	(1.5		)	(1.6		)
Amortization of prior service costs	(0.3		)	(0.4		)	—
Curtailment	(0.8		)	(1.1		)	—
Amortization and deferral of actuarial gain	0.5			0.8			0.9
Other	(0.3		)	(0.6		)	(0.8		)
Total net periodic benefit cost	$	4.1		$	5.0		$	6.7

During 2018, service costs were recorded to operating expenses while all other components of the net periodic benefit was recorded to other income and expense within our consolidated statement of operations.

Other changes in plan assets and benefit obligations recognized in AOCI are as follows:



Amount included in AOCI - December 31, 2016	$	(6.7	)
Prior service cost	(0.4		)
Amortization of net gain	0.8
Curtailment	1.9
Taxes	(0.6		)
Other	0.2
Amount included in AOCI - December 31, 2017	$	(4.8	)
Prior service cost	(0.3		)
Amortization of net gain	0.6
Curtailment	0.6
Taxes	(0.7		)
Other	2.0
Amount included in AOCI - December 31, 2018	$	(2.6	)

We estimate that we will pay employer contributions of approximately $2.4 in 2019. The expected future benefits to be paid in respect of the pension plans as of December 31, 2018 were as follows:



Year
2019	$	1.9
2020	1.7
2021	1.7
2022	1.9
2023	1.6
2024 to 2028	9.1

Restructuring and Related Expenses

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring

Restructuring and Related Expenses

In the first quarter of 2017, we initiated a company-wide restructuring designed to help position the Company for sustainable, long-term growth that we believe will further allow us to fulfill our mission of serving patients and families with rare diseases. The initial restructuring activities primarily focused on a reduction of the Company's global workforce. In September 2017, we committed to an operational plan to re-align the global organization with its refocused corporate strategy. The re-alignment focuses investments in priority growth areas to maximize leadership in complement and grow the rare disease business. The re-alignment also included the relocation of the Company's headquarters to Boston, Massachusetts which was completed in the second quarter of 2018. Our New Haven, Connecticut site continues to support employees working in the research and process development laboratories, the clinical supply and quality teams, nurse case management and a number of important enterprise business services. The plan also reduced the Company's global workforce by approximately 20.0%. The restructuring is designed to result in cost savings by focusing the development portfolio, simplifying business structures and processes across the Company's global operations, and closing of multiple Alexion sites, including ARIMF and certain regional and country-based offices.

The following table summarizes the total expenses recorded related to the restructuring activities by type of activity and the locations recognized within the consolidated statements of operations:



	December 31, 2018										December 31, 2017								December 31, 2016
	Employee Separation Costs		Asset-Related Charges		Other			Total			Employee Separation Costs		Asset-Related Charges		Other		Total		Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	5.8	$	—		$	5.8		$	—	$	152.1	$	—	$	152.1	$	—	$	—	$	—	$	—
Research and Development	—		0.1		—			0.1			—		16.3		—		16.3		—		—		—		—
Selling , General and Administrative	—		19.4		—			19.4			—		10.9		—		10.9		—		—		—		—
Restructuring Expense	4.6		—		20.9			25.5			87.3		—		17.3		104.6		3.0		—				3.0
Other expense	—		—		(0.1		)	(0.1		)	—		—		2.6		2.6		—		—		—		—
	$	4.6	$	25.3	$	20.8		$	50.7		$	87.3	$	179.3	$	19.9	$	286.5	$	3.0	$	—	$	—	$	3.0

Employee separation costs are associated with headcount reductions, as well as corporate employees not relocating to the Company's headquarters in 2018.

Asset-related charges consist of accelerated depreciation costs and asset impairment charges. Accelerated depreciation costs primarily relates to site closures, including ARIMF (which was sold to a third-party in 2018). Accelerated depreciation costs represent the difference between the depreciation expense recognized over the revised useful life of the asset, based upon the anticipated date the site closure and the depreciation expense as determined using the useful life prior to the restructuring activities. Asset impairment charges primarily related to manufacturing assets that will no longer be utilized due to the 2017 restructuring activities.

Other costs consist of contract termination expenses, relocation costs, and other costs incurred as a direct result of an exit plan.

The following table presents a reconciliation of the restructuring reserve recorded within accounts payable and accrued expenses on the Company's consolidated balance sheets for the years ended December 31, 2018 and 2017:



	December 31, 2018												December 31, 2017
	Employee Separation Costs			Asset-Related Charges			Other			Total			Employee Separation Costs			Asset-Related Charges			Other			Total
Liability, beginning of year	$	53.8		$	—		$	4.4		$	58.2		$	0.5		$	—		$	0.1		$	0.6
Charges	5.8			25.3			21.1			52.2			88.2			179.3			19.9			287.4
Settlements	(54.2		)	—			(25.2		)	(79.4		)	(34.0		)	—			(15.6		)	(49.6		)
Adjustments to previous estimates	(1.2		)	—			(0.3		)	(1.5		)	(0.9		)	—			—			(0.9		)
Non Cash Activity	—			(25.3		)	—			(25.3		)	—			(179.3		)	—			(179.3		)
Liability, end of year	$	4.2		$	—		$	—		$	4.2		$	53.8		$	—		$	4.4		$	58.2

The restructuring reserve of $4.2 and $58.2 is recorded in accounts payable and accrued expenses on the Company's consolidated balance sheet as of December 31, 2018 and 2017, respectively.

As a result of the relocation of our corporate headquarters to Boston, Massachusetts, we were required to repay a forgivable loan and grant that were provided by the State of Connecticut Department of Economic Community Development in 2015 in connection with the construction of our current headquarters in New Haven, Connecticut. The loan and grant totaled $26.0 and were recognized, upon receipt, as a reduction in the cost of our New Haven facility-related fixed assets. As a result, the $26.0 repayment obligation was recorded in the third quarter 2017 with an offsetting increase in the carrying value of the related assets. We repaid this amount in the fourth quarter 2017.

In the first quarter 2019, we have undertaken corporate restructuring activities to re-align our global organization with our re-focused strategy, reduce costs, and realize operational efficiencies. We expect to incur estimated expenses up to $25.0 associated with this recent restructuring by the end of 2019.

Segment Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segment Information

We operate in a single segment, focusing on serving patients affected by rare diseases through the innovation, development and commercialization of life-changing therapies. Consistent with our operational structure, our chief operating decision maker manages and allocates resources at a global, consolidated level. Therefore, results of our operations are reported on a consolidated basis for purposes of segment reporting, consistent with our management reporting. Disclosures about net product sales and long-lived assets by geographic area are presented below.

Net Product Sales

Net product sales by product and geographic region are as follows:



	Year Ended December 31,						% Change
	2018		2017		2016		2018 compared to 2017		2017 compared to 2016
SOLIRIS
United States	$	1,588.4	$	1,235.0	$	1,058.5	28.6	%	16.7	%
Europe	1,036.7		985.2		939.7		5.2	%	4.8	%
Asia Pacific	382.0		328.1		303.8		16.4	%	8.0	%
Rest of World	555.9		595.8		541.2		(6.7	)%	10.1	%
	$	3,563.0	$	3,144.1	$	2,843.2	13.3	%	10.6	%

STRENSIQ
United States	$	374.3	$	280.1	$	177.5	33.6	%	57.8	%
Europe	61.7		35.6		15.3		73.3	%	132.7	%
Asia Pacific	27.9		18.6		13.0		50.0	%	43.1	%
Rest of World	11.2		5.5		3.6		103.6	%	52.8	%
	$	475.1	$	339.8	$	209.4	39.8	%	62.3	%

KANUMA
United States	$	51.3	$	42.4	$	20.4	21.0	%	107.8	%
Europe	21.6		14.6		6.3		47.9	%	131.7	%
Asia Pacific	3.7		2.7		1.3		37.0	%	107.7	%
Rest of World	15.4		5.9		1.1		**		**
	$	92.0	$	65.6	$	29.1	40.2	%	125.4	%
Total Net Product Sales	4,130.1		$	3,549.5	$	3,081.7	16.4	%	15.2	%

** Percentages not meaningful

Long-Lived Assets

Long-lived assets consist of property, plant and equipment.



	December 31,
	2018		2017
United States	$	468.3	$	455.9
Europe	1,001.1		864.6
Other	2.1		4.9
	$	1,471.5	$	1,325.4

Quarterly Financial Information (unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information (unaudited)

The following condensed quarterly financial information is for the years ended December 31, 2018 and 2017:



	March 31			June 30				September 30			December 31
2018:
Revenues	$	930.9		$	1,045.0			$	1,026.5		$	1,128.8
Cost of sales	91.6			95.3				90.6			96.8
Operating expenses	571.9			1,349.8			(1)	577.3			988.3			(1)
Operating income	267.4			(400.1		)		358.6			43.7
Net income	$	249.1		$	(457.4	)		$	330.9		$	(45.0	)
Earnings per common share
Basic	$	1.12		$	(2.05	)		$	1.48		$	(0.20	)
Diluted	$	1.11		$	(2.05	)		$	1.47		$	(0.20	)

	March 31			June 30				September 30			December 31
2017:
Revenues	$	869.6		$	912.7			$	859.1		$	909.7
Cost of sales	69.0			83.6				157.0		(2)	144.6			(2)
Operating expenses	588.6		(3)	602.4			(4)	622.0		(3)	656.5
Operating income	212.0			226.7				80.1			108.6
Net income	$	170.1		$	165.2			$	78.0		$	30.0		(5)
Earnings per common share
Basic	$	0.76		$	0.74			$	0.35		$	0.13
Diluted	$	0.75		$	0.73			$	0.35		$	0.13

(1) Included within operating expenses for the second and fourth quarter of 2018 we recognized $803.7 and $379.3, respectively, of acquired in-process research and development expense related to our Wilson and Syntimmune acquisitions, respectively. See Note 2 “Acquisitions” for additional information.

(2) Included within cost of sales for the third and fourth quarters 2017 are $83.0 and $69.1, respectively, of restructuring related expenses associated with the planned closure of the ARIMF facility.

(3) Included within operating expenses for the first and third quarters 2017 are $23.8 and $79.4, respectively of restructuring and related expenses.

(4) Included within operating expenses for the second quarter 2017 is an impairment charge of $31.0, associated with an early stage clinical indefinite-lived intangible asset.

(5) We recognized a tax (benefit) expense of $(56.5) and $45.8 in 2018 and 2017, respectively, as a result of the Tax Cuts and Jobs Act. In 2017, we recorded certain impacts of the Tax Act on a provisional basis. As of December 22, 2018, our accounting for the impact of the Tax Act was complete. See Note 12, “Income Taxes” for additional information.

Business Overview and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Business Overview and Summary of Significant Accounting Policies [Abstract]

Business

Basis of Presentation and Principles of Consolidation

Dividend Policy

Critical Accounting Estimates

The most significant areas involving estimates, judgments and assumptions used in the preparation of our consolidated financial statements are as follows:


•	Revenue recognition;


•	Contingent liabilities;


•	Inventories;


•	Share-based compensation;


•	Valuation of goodwill, acquired intangible assets and in-process research and development (IPR&D);


•	Valuation of contingent consideration; and


•	Income taxes.

Foreign Currency Translation

Cash and Cash Equivalents

Fair Value of Financial Instruments

Marketable Securities

Accounts Receivable

Concentration of Credit Risk

Inventories

Capitalization of Inventory Costs

Inventory Write-Offs

Inventories are stated at the lower of cost or net realizable value. Cost is determined in a manner that approximates average costs.

Derivative Instruments

Property, Plant and Equipment

Property, plant and equipment are stated at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. We estimate economic lives as follows:


•	Building and improvements—fifteen to thirty five years


•	Machinery and laboratory equipment—five to fifteen years


•	Computer hardware and software—three to seven years


•	Furniture and office equipment— five to ten years

Construction-in-progress reflects amounts incurred for property, plant, or equipment construction or improvements that have not been placed in service.

Assets Held for Sale

Manufacturing Facilities

Acquisitions

Our consolidated financial statements include the results of operations of an acquired business after the completion of the acquisition.

Intangible Assets

Goodwill

Impairment of Long-Lived Assets

Contingent Consideration

Contingent liabilities

Treasury Stock

Treasury stock is accounted for using the cost method, with the purchase price of the common stock recorded separately as a deduction from stockholders’ equity.

Revenue from Contract with Customer [Policy Text Block]

Revenue Recognition

Nature of Products

Variable Consideration

Variability in the transaction price for our products pursuant to our contracts with customers primarily arises from the following:

See Note 19 “Segment Information” for a summary of revenue from contracts with customers by product and geographical region.

Contract Balances and Receivables

Research and Development Expenses

Share-Based Compensation

Restructuring and Restructuring Related Expenses

Earnings Per Common Share

Certain items in the prior year’s consolidated financial statements have been reclassified to conform to the current presentation.

New Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Impacts of the New Revenue Standard

Business Overview and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Business Overview and Summary of Significant Accounting Policies [Abstract]

Schedule of Inventories

The components of inventory are as follows:



	December 31,
	2018		2017
Raw materials	$	31.4	$	4.7
Work-in-process	90.4		148.6
Finished goods	350.7		307.1
	$	472.5	$	460.4

Schedule of the Calculation of Basic and Diluted EPS

The following table summarizes the calculation of basic and diluted EPS for years ended December 31, 2018, 2017 and 2016:



	Year Ended December 31,
	2018		2017		2016
Net income used for basic and diluted calculation	$	77.6	$	443.3	$	399.4
Shares used in computing earnings per common share—basic	222.7		223.9		224.3
Weighted-average effect of dilutive securities:
Stock awards	1.8		1.5		2.0
Shares used in computing earnings per common share—diluted	224.5		225.4		226.3
Earnings per common share:
Basic	$	0.35	$	1.98	$	1.78
Diluted	$	0.35	$	1.97	$	1.76

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]



	December 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Commercial paper	$	52.1	$	—	$	—		$	52.1
Corporate bonds	122.9		—		(0.1		)	122.8
Other government related obligations:
U.S.	17.5		—		—			17.5
Bank certificates of deposit	33.2		—		—			33.2
Total available-for-sale debt securities	$	225.7	$	—	$	(0.1	)	$	225.6



	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Commercial paper	$	16.0	$	—	$	—		$	16.0
Repurchase agreements	27.0		—		—			27.0
Corporate bonds	432.2		0.5		(0.2		)	432.5
Other government related obligations:
Foreign	426.3		0.2		(0.2		)	426.3
Bank certificates of deposit	11.8		—		—			11.8
Total available-for-sale debt securities	$	913.3	$	0.7	$	(0.4	)	$	913.6

Available-for-sale Securities by Balance Sheet Location Classification [Table Text Block]



	December 31, 2018		December 31, 2017
Cash and cash equivalents	$	43.8	$	42.7
Marketable securities	181.8		870.9
	$	225.6	$	913.6

Investments Classified by Contractual Maturity Date [Table Text Block]

The fair values of available-for-sale debt securities as of December 31, 2018, by contractual maturity, are summarized as follows:



	December 31, 2018
Due in one year or less	$	211.5
Due after one year through three years	14.1
Due after three years through five years	—
	$	225.6

Derivative Instruments and Hedging Activities (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities [Abstract]

Schedule of Other Comprehensive Income and Earnings from Foreign Exchange Contracts



	Year ended December 31,
	2018						2017					2016
	Net Product Sales			Interest Expense			Net Product Sales		Interest Expense			Net Product Sales		Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	4,130.1		$	(98.2	)	$	3,549.5	$	(98.4	)	$	3,081.7	$	(96.9	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	(1.8	)	$	—		$	28.9	$	—		$	73.0	$	—
Interest Rate Swap Contracts	$	—		$	13.6		$	—	$	(1.8	)	$	—	$	(0.2	)



	Year Ended December 31,
	2018			2017			2016
Foreign Exchange Contracts:
Gain (loss) recognized in AOCI, net of tax	$	37.7		$	(96.1	)	$	40.2
Gain (loss) reclassified from AOCI to net product sales (effective portion), net of tax	$	(1.4	)	$	18.7		$	47.3
Interest Rate Contracts:
Gain (loss) recognized in AOCI, net of tax	$	(4.8	)	$	7.9		$	6.2
Gain (loss) reclassified from AOCI to interest expense, net of tax	$	10.8		$	(1.1	)	$	(0.1	)

Schedule of Fair Value of Outstanding Derivatives

The following tables summarize the fair value of outstanding derivatives at December 31, 2018 and 2017:



	December 31, 2018
	Asset Derivatives			Liability Derivatives
	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Derivatives designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	$	16.9	Other current liabilities	$	7.3
Foreign exchange forward contracts	Other assets	0.3		Other liabilities	3.1
Interest rate contracts	Prepaid expenses and other current assets	20.1		Other current liabilities	0.8
Interest rate contracts	Other assets	—		Other liabilities	17.3
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	23.6		Other current liabilities	11.5
Total fair value of derivative instruments		$	60.9		$	40.0



	December 31, 2017
	Asset Derivatives			Liability Derivatives
	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Derivatives designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	$	12.9	Other current liabilities	$	34.8
Foreign exchange forward contracts	Other assets	4.1		Other liabilities	26.0
Interest rate contracts	Prepaid expenses and other current assets	9.3		Other current liabilities	—
Interest rate contracts	Other assets	12.5		Other liabilities	—
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	10.0		Other current liabilities	13.7
Total fair value of derivative instruments		$	48.8		$	74.5

Offsetting Assets and Liabilities [Table Text Block]



December 31, 2018
									Gross Amounts Not Offset in the Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	60.9		$	—	$	60.9		$	(30.2	)	$	—	$	30.7
Derivative liabilities	$	(40.0	)	$	—	$	(40.0	)	$	30.2		$	—	$	(9.8	)



December 31, 2017
									Gross Amounts Not Offset in the Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	48.8		$	—	$	48.8		$	(26.3	)	$	—	$	22.5
Derivative liabilities	$	(74.5	)	$	—	$	(74.5	)	$	26.3		$	—	$	(48.2	)

Facility Lease Obligations (Tables)

12 Months Ended

Dec. 31, 2018

Operating Leased Assets [Line Items]

Schedule of Aggregate Future Minimum Annual Rental Payments

Aggregate future minimum non-cancellable commitments under the Boston facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	4.3
2020	6.6
2021	6.7
2022	6.8
2023	7.0
Thereafter	56.7

Construction in Progress [Member]

Operating Leased Assets [Line Items]

Schedule of Aggregate Future Minimum Annual Rental Payments

Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	9.4
2020	8.8
2021	9.0
2022	9.2
2023	9.2
Thereafter	63.9

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies [Line Items]

Schedule of Aggregate Future Minimum Annual Rental Payments

Aggregate future minimum non-cancellable commitments under the Boston facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	4.3
2020	6.6
2021	6.7
2022	6.8
2023	7.0
Thereafter	56.7

Property, Plant and Equipment, Other Types [Member]

Commitments and Contingencies [Line Items]

Schedule of Aggregate Future Minimum Annual Rental Payments

Aggregate future minimum annual rental payments, for the next five years and thereafter under non-cancellable operating leases (including facilities and equipment) as of December 31, 2018 are:



Year
2019	$	14.1
2020	9.3
2021	5.6
2022	3.9
2023	3.5
Thereafter	11.6

Construction in Progress [Member]

Commitments and Contingencies [Line Items]

Schedule of Aggregate Future Minimum Annual Rental Payments

Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2018 are as follows:



Year
2019	$	9.4
2020	8.8
2021	9.0
2022	9.2
2023	9.2
Thereafter	63.9

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Income Tax Provision (Benefit) on Income Before Income Taxes

The income tax expense is based on income before income taxes as follows:



	Year Ended December 31,
	2018			2017			2016
U.S.	$	(451.4	)	$	(43.9	)	$	(164.6	)
Non-U.S.	693.6			591.7			740.8
	$	242.2		$	547.8		$	576.2

Schedule of Components of Income Tax Provision (Benefit)

The components of the income tax expense are as follows:



	Year Ended December 31,
	2018			2017			2016
Domestic
Current	$	57.0		$	42.9		$	3.4
Deferred	49.5			7.2			107.6
	106.5			50.1			111.0
Foreign
Current	74.7			107.5			69.1
Deferred	(16.6		)	(53.1		)	(3.3		)
	58.1			54.4			65.8
Total
Current	131.7			150.4			72.5
Deferred	32.9			(45.9		)	104.3
	$	164.6		$	104.5		$	176.8

Reconciliation of the Statutory U.S. Federal Income Tax Rate to Effective Income Tax Rate

The reconciliation of the statutory U.S. federal income tax rate to our effective income tax rate is as follows:



	Year Ended December 31,
	2018		2017		2016
U.S. federal statutory tax rate	21.0	%	35.0	%	35.0	%
Benefit of foreign earnings	(71.2	)%	60.1	%	(7.2	)%
Tax credits	(17.0	)%	(10.7	)%	(6.0	)%
Tax reserves	12.1	%	(14.0	)%	2.7	%
Re-measurement of deferred taxes as a result of the Tax Act	—	%	(53.4	)%	—	%
Acquired in-process research & development	102.6	%	—	%	—	%
U.S. state taxes	14.2	%	1.5	%	4.1	%
Other permanent differences	6.3	%	0.6	%	2.1	%

Effective Income Tax Rate	68.0	%	19.1	%	30.7	%

Schedule of Components of Deferred Tax Assets and Liabilities

The components of the deferred tax assets and liabilities are as follows:



	December 31,			December 31,
	2018			2017
Deferred tax assets:
Net operating losses	$	41.8		$	4.9
Income tax credits	371.6			442.5
Stock compensation	47.6			66.6
Accruals and allowances	105.8			97.7
Unrealized losses	—			6.6
Research and development expenses	5.2			7.2
Accrued royalties	89.1			74.2
	661.1			699.7
Valuation allowance	(19.6		)	(3.4		)
Total deferred tax assets	641.5			696.3
Deferred tax liabilities:
Depreciable assets	(88.7		)	(75.2		)
Unrealized gains	(6.6		)	—
Investment in foreign partnership	(566.6		)	(607.9		)
Intangible assets	(268.8		)	(285.6		)
Total deferred tax liabilities	(930.7		)	(968.7		)
Net deferred tax (liability) asset	$	(289.2	)	$	(272.4	)

Reconciliation of Unrecognized Tax Benefits

The beginning and ending amounts of unrecognized tax benefits reconciles as follows:



	2018			2017			2016
Beginning of period balance	$	60.9		$	138.9		$	113.9
Increases for tax positions taken during a prior period	9.1			5.6			3.4
Decreases for tax positions taken during a prior period	(5.8		)	(85.8		)	(1.1		)
Increases for tax positions taken during the current period	28.8			19.3			22.8
Decreases for tax positions related to settlements	—			(15.8		)	—
Decreases for tax positions related to lapse of statute	(0.3		)	(1.3		)	(0.1		)
	$	92.7		$	60.9		$	138.9

Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-Based Compensation

The following table summarizes the share-based compensation expense in the consolidated statements of operations:



	Year Ended December 31,
	2018			2017			2016
Cost of sales	$	16.0		$	11.1		$	11.1
Research and development	57.5			76.4			57.6
Selling, general and administrative	129.5			155.6			123.6
Total share-based compensation expense	203.0			243.1			192.3
Income tax effect	(46.5		)	(89.3		)	(70.3		)
Total share-based compensation expense, net of tax	$	156.5		$	153.8		$	122.0

Schedule of Share-based Compensation, Stock Options, Activity

A summary of the status of our stock options at December 31, 2018, and changes during the year then ended is presented in the table and narrative below:



	Number of shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2017	5.3		$	124.71
Granted	—		—
Exercised	(0.5	)	82.70
Forfeited and canceled	(1.2	)	156.20
Outstanding at December 31, 2018	3.6		$	119.68	4.74	$	44.5
Vested and unvested expected to vest at December 31, 2018	3.6		$	119.63	4.73	$	44.5
Exercisable at December 31, 2018	3.2		$	117.73	4.38	$	44.5

Schedule of Share-based Compensation Valuation Assumptions

the fair value of options at the date of grant was estimated using the Black-Scholes model with the following ranges of weighted average assumptions:



	December 31,	December 31,
	2017	2016
Expected life in years	4.07 - 4.29	3.82 - 6.29
Interest rate	1.64% - 1.92%	0.87% - 1.66%
Volatility	38.78% - 39.01%	33.45% - 37.61%
Dividend yield	—	—

Schedule of Share-based Compensation, Restricted Stock Activity

A summary of the status of our nonvested Restricted Stock at December 31, 2018 and changes during the year then ended is as follows:



	Number of Shares		Weighted Average Grant Date Fair Value
Nonvested Restricted Stock at December 31, 2017	3.6		$	130.75
Shares granted	2.1		119.27
Shares forfeited	(0.7	)	126.78
Shares vested	(1.3	)	135.17
Nonvested Restricted Stock at December 31, 2018	3.7		$	123.25

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2018

Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The following table summarizes the changes in AOCI, by component, for the years ended December 31, 2018, 2017 and 2016:



	Defined Benefit Pension Plans			Unrealized Gains (Losses) from Debt Securities			Unrealized Gains (Losses) from Hedging Activities			Foreign Currency Translation Adjustment			Total Accumulated Other Comprehensive Income (Loss)
Balances, December 31, 2015	$	(9.6	)	$	(0.8	)	$	92.7		$	(20.0	)	$	62.3
Other comprehensive income before reclassifications	2.6			0.2			46.4			(4.3		)	44.9
Amounts reclassified from other comprehensive income	0.3			0.2			(47.2		)	—			(46.7		)
Net other comprehensive income (loss)	2.9			0.4			(0.8		)	(4.3		)	(1.8		)
Balances, December 31, 2016	$	(6.7	)	$	(0.4	)	$	91.9		$	(24.3	)	$	60.5
Other comprehensive income before reclassifications	0.5			(0.2		)	(88.2		)	8.4			(79.5		)
Amounts reclassified from other comprehensive income	1.4			0.8			(17.6		)	—			(15.4		)
Net other comprehensive income (loss)	1.9			0.6			(105.8		)	8.4			(94.9		)
Balances, December 31, 2017	$	(4.8	)	$	0.2		$	(13.9	)	$	(15.9	)	$	(34.4	)
Other comprehensive income before reclassifications	1.5			0.1			32.9			(0.5		)	34.0
Amounts reclassified from other comprehensive income	0.7			(0.6		)	(9.4		)	—			(9.3		)
Net other comprehensive income (loss)	2.2			(0.5		)	23.5			(0.5		)	24.7
Balances, December 31, 2018	$	(2.6	)	$	(0.3	)	$	9.6		$	(16.4	)	$	(9.7	)

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The table below provides details regarding significant reclassifications from AOCI during the years ended December 31, 2018, 2017 and 2016:



Details about Accumulated Other Comprehensive Income Components	Amount Reclassified From Accumulated Other Comprehensive Income during the year ended December 31,									Affected Line Item in the Consolidated Statements of Operations
	2018			2017			2016
Unrealized Gains (Losses) on Hedging Activity
Effective portion of foreign exchange contracts	$	(1.8	)	$	28.9		$	73.0		Net product sales
Effective portion of interest rate swap contracts	13.6			(1.8		)	(0.2		)	Interest expense
	11.8			27.1			72.8
	(2.4		)	(9.5		)	(25.6		)	Income tax expense
	$	9.4		$	17.6		$	47.2
Defined Benefit Pension Items
Amortization of prior service costs and actuarial losses	$	(0.3	)	$	(0.4	)	$	(0.5	)	^(a)
Curtailment	(0.6		)	(1.8		)	—			^(a)
	(0.9		)	(2.2		)	(0.5		)
	0.2			0.8			0.2			Income tax expense
	$	(0.7	)	$	(1.4	)	$	(0.3	)

(a) This AOCI component is included in the computation of net periodic pension benefit cost (see Note 17, Employee Benefit Plans, for additional details).

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule Of Assets And Liabilites Measured At Fair Value

December 31, 2018 and 2017, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value.



		Fair Value Measurement at December 31, 2018
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Money market funds	$	569.4	$	—	$	569.4	$	—
Cash equivalents	Commercial paper	$	35.4	$	—	$	35.4	$	—
Cash equivalents	Corporate bonds	$	0.2	$	—	$	0.2	$	—
Cash equivalents	Other government-related obligations	$	8.2	$	—	$	8.2	$	—
Marketable securities	Mutual funds	$	16.5	$	16.5	$	—	$	—
Marketable securities	Commercial paper	$	16.7	$	—	$	16.7	$	—
Marketable securities	Corporate bonds	$	122.6	$	—	$	122.6	$	—
Marketable securities	Other government-related obligations	$	9.3	$	—	$	9.3	$	—
Marketable securities	Bank certificates of deposit	$	33.2	$	—	$	33.2	$	—
Other assets	Equity securities	$	90.8	$	8.9	$	81.9	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	40.5	$	—	$	40.5	$	—
Other assets	Foreign exchange forward contracts	$	0.3	$	—	$	0.3	$	—
Other current liabilities	Foreign exchange forward contracts	$	18.8	$	—	$	18.8	$	—
Other liabilities	Foreign exchange forward contracts	$	3.1	$	—	$	3.1	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	20.1	$	—	$	20.1	$	—
Other current liabilities	Interest rate contracts	$	0.8	$	—	$	0.8	$	—
Other liabilities	Interest rate contracts	$	17.3	$	—	$	17.3	$	—
Current portion of contingent consideration	Acquisition-related contingent consideration	$	97.6	$	—	$	—	$	97.6
Contingent consideration	Acquisition-related contingent consideration	$	183.2	$	—	$	—	$	183.2



		Fair Value Measurement at December 31, 2017
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Commercial paper	$	9.5	$	—	$	9.5	$	—
Cash equivalents	Reverse repurchase agreements	$	27.0	$	—	$	27.0	$	—
Cash equivalents	Corporate bonds	$	1.2	$	—	$	1.2	$	—
Cash equivalents	Other government-related obligations	$	5.0	$	—	$	5.0	$	—
Marketable securities	Mutual funds	$	18.5	$	18.5	$	—	$	—
Marketable securities	Commercial paper	$	6.5	$	—	$	6.5	$	—
Marketable securities	Corporate bonds	$	431.3	$	—	$	431.3	$	—
Marketable securities	Other government-related obligations	$	421.3	$	—	$	421.3	$	—
Marketable securities	Bank certificates of deposit	$	11.8	$	—	$	11.8	$	—
Marketable securities	Equity securities	$	0.3	$	0.3	$	—	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	22.9	$	—	$	22.9	$	—
Other assets	Foreign exchange forward contracts	$	4.1	$	—	$	4.1	$	—
Other current liabilities	Foreign exchange forward contracts	$	48.5	$	—	$	48.5	$	—
Other liabilities	Foreign exchange forward contracts	$	26.0	$	—	$	26.0	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	9.3	$	—	$	9.3	$	—
Other assets	Interest rate contracts	$	12.5	$	—	$	12.5	$	—
Contingent consideration	Acquisition-related contingent consideration	$	168.9	$	—	$	—	$	168.9

Schedule Of Acquisition-Related Contingent Consideration

The following table represents a roll-forward of our acquisition-related contingent consideration:



	2018
Balance at beginning of period	$	168.9
Amounts derecognized upon sale of asset	(4.6		)
Changes in fair value	116.5
Balance at end of period	$	280.8

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

Retirement Benefits [Abstract]

Schedule of Change in Benefit Obligation

The following table sets forth the funded status and the amounts recognized for defined benefit plans, including the impacts of the curtailments:



	December 31,
	2018			2017
Change in benefit obligation:
Projected benefit obligation, beginning of year	$	43.4		$	48.4
Service cost	6.3			7.8
Curtailment	(3.8		)	(9.6		)
Other	(6.5		)	(3.2		)
Projected benefit obligation, end of year	$	39.4		$	43.4
Accumulated benefit obligation, end of year	$	36.1		$	39.4

Schedule of Change in Plan Assets



	December 31,
	2018			2017
Change in plan assets:
Fair value of plan assets, beginning of year	$	24.2		$	28.2
Employer contributions	3.0			4.3
Plan participants' contributions	1.3			1.5
Curtailment	(2.4		)	(6.6		)
Other	(4.3		)	(3.2		)
Fair value of plan assets, end of year	$	21.8		$	24.2
Funded status at end of year	$	(17.6	)	$	(19.2	)

Schedule of Weighted Average Assumptions Used to Calculate Net Periodic Benefit Cost and the Actuarial Present Value of Projected Benefit Obligations

The following table provides the weighted average assumptions used to calculate net periodic benefit cost and the actuarial present value of projected benefit obligations:



	December 31,
	2018		2017
Weighted average assumptions - Net Periodic Benefit Cost:
Discount rate	0.8	%	0.7	%
Long term rate of return on assets	2.5	%	3.0	%
Rate of compensation increase	1.3	%	1.4	%
Weighted average assumptions - Projected Benefit Obligation:
Discount Rate	0.8	%	0.8	%
Rate of compensation increase	1.3	%	1.3	%

Schedule of Components of Net Periodic Benefit Costs

The components of net periodic benefit cost are as follows:



	Year Ended December 31,
	2018			2017			2016
Service cost	$	6.3		$	7.8		$	8.2
Employee contributions	(1.3		)	(1.5		)	(1.6		)
Amortization of prior service costs	(0.3		)	(0.4		)	—
Curtailment	(0.8		)	(1.1		)	—
Amortization and deferral of actuarial gain	0.5			0.8			0.9
Other	(0.3		)	(0.6		)	(0.8		)
Total net periodic benefit cost	$	4.1		$	5.0		$	6.7

Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income

Other changes in plan assets and benefit obligations recognized in AOCI are as follows:



Amount included in AOCI - December 31, 2016	$	(6.7	)
Prior service cost	(0.4		)
Amortization of net gain	0.8
Curtailment	1.9
Taxes	(0.6		)
Other	0.2
Amount included in AOCI - December 31, 2017	$	(4.8	)
Prior service cost	(0.3		)
Amortization of net gain	0.6
Curtailment	0.6
Taxes	(0.7		)
Other	2.0
Amount included in AOCI - December 31, 2018	$	(2.6	)

Schedule of Estimated Future Benefit Payments

The expected future benefits to be paid in respect of the pension plans as of December 31, 2018 were as follows:



Year
2019	$	1.9
2020	1.7
2021	1.7
2022	1.9
2023	1.6
2024 to 2028	9.1

Restructuring (Tables)

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs [Table Text Block]

The following table summarizes the total expenses recorded related to the restructuring activities by type of activity and the locations recognized within the consolidated statements of operations:



	December 31, 2018										December 31, 2017								December 31, 2016
	Employee Separation Costs		Asset-Related Charges		Other			Total			Employee Separation Costs		Asset-Related Charges		Other		Total		Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	5.8	$	—		$	5.8		$	—	$	152.1	$	—	$	152.1	$	—	$	—	$	—	$	—
Research and Development	—		0.1		—			0.1			—		16.3		—		16.3		—		—		—		—
Selling , General and Administrative	—		19.4		—			19.4			—		10.9		—		10.9		—		—		—		—
Restructuring Expense	4.6		—		20.9			25.5			87.3		—		17.3		104.6		3.0		—				3.0
Other expense	—		—		(0.1		)	(0.1		)	—		—		2.6		2.6		—		—		—		—
	$	4.6	$	25.3	$	20.8		$	50.7		$	87.3	$	179.3	$	19.9	$	286.5	$	3.0	$	—	$	—	$	3.0

Employee separation costs are associated with headcount reductions, as well as corporate employees not relocating to the Company's headquarters in 2018.

Other costs consist of contract termination expenses, relocation costs, and other costs incurred as a direct result of an exit plan.



	December 31, 2018												December 31, 2017
	Employee Separation Costs			Asset-Related Charges			Other			Total			Employee Separation Costs			Asset-Related Charges			Other			Total
Liability, beginning of year	$	53.8		$	—		$	4.4		$	58.2		$	0.5		$	—		$	0.1		$	0.6
Charges	5.8			25.3			21.1			52.2			88.2			179.3			19.9			287.4
Settlements	(54.2		)	—			(25.2		)	(79.4		)	(34.0		)	—			(15.6		)	(49.6		)
Adjustments to previous estimates	(1.2		)	—			(0.3		)	(1.5		)	(0.9		)	—			—			(0.9		)
Non Cash Activity	—			(25.3		)	—			(25.3		)	—			(179.3		)	—			(179.3		)
Liability, end of year	$	4.2		$	—		$	—		$	4.2		$	53.8		$	—		$	4.4		$	58.2

The restructuring reserve of $4.2 and $58.2 is recorded in accounts payable and accrued expenses on the Company's consolidated balance sheet as of December 31, 2018 and 2017, respectively.

Segment Information (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Schedule of Revenues and Tangible Long-Lived Assets by Significant Geographic Region

Long-lived assets consist of property, plant and equipment.



	December 31,
	2018		2017
United States	$	468.3	$	455.9
Europe	1,001.1		864.6
Other	2.1		4.9
	$	1,471.5	$	1,325.4

Net product sales by product and geographic region are as follows:



	Year Ended December 31,						% Change
	2018		2017		2016		2018 compared to 2017		2017 compared to 2016
SOLIRIS
United States	$	1,588.4	$	1,235.0	$	1,058.5	28.6	%	16.7	%
Europe	1,036.7		985.2		939.7		5.2	%	4.8	%
Asia Pacific	382.0		328.1		303.8		16.4	%	8.0	%
Rest of World	555.9		595.8		541.2		(6.7	)%	10.1	%
	$	3,563.0	$	3,144.1	$	2,843.2	13.3	%	10.6	%

STRENSIQ
United States	$	374.3	$	280.1	$	177.5	33.6	%	57.8	%
Europe	61.7		35.6		15.3		73.3	%	132.7	%
Asia Pacific	27.9		18.6		13.0		50.0	%	43.1	%
Rest of World	11.2		5.5		3.6		103.6	%	52.8	%
	$	475.1	$	339.8	$	209.4	39.8	%	62.3	%

KANUMA
United States	$	51.3	$	42.4	$	20.4	21.0	%	107.8	%
Europe	21.6		14.6		6.3		47.9	%	131.7	%
Asia Pacific	3.7		2.7		1.3		37.0	%	107.7	%
Rest of World	15.4		5.9		1.1		**		**
	$	92.0	$	65.6	$	29.1	40.2	%	125.4	%
Total Net Product Sales	4,130.1		$	3,549.5	$	3,081.7	16.4	%	15.2	%

Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Schedule of Condensed Quarterly Financial Information

The following condensed quarterly financial information is for the years ended December 31, 2018 and 2017:



	March 31			June 30				September 30			December 31
2018:
Revenues	$	930.9		$	1,045.0			$	1,026.5		$	1,128.8
Cost of sales	91.6			95.3				90.6			96.8
Operating expenses	571.9			1,349.8			(1)	577.3			988.3			(1)
Operating income	267.4			(400.1		)		358.6			43.7
Net income	$	249.1		$	(457.4	)		$	330.9		$	(45.0	)
Earnings per common share
Basic	$	1.12		$	(2.05	)		$	1.48		$	(0.20	)
Diluted	$	1.11		$	(2.05	)		$	1.47		$	(0.20	)

	March 31			June 30				September 30			December 31
2017:
Revenues	$	869.6		$	912.7			$	859.1		$	909.7
Cost of sales	69.0			83.6				157.0		(2)	144.6			(2)
Operating expenses	588.6		(3)	602.4			(4)	622.0		(3)	656.5
Operating income	212.0			226.7				80.1			108.6
Net income	$	170.1		$	165.2			$	78.0		$	30.0		(5)
Earnings per common share
Basic	$	0.76		$	0.74			$	0.35		$	0.13
Diluted	$	0.75		$	0.73			$	0.35		$	0.13

(3) Included within operating expenses for the first and third quarters 2017 are $23.8 and $79.4, respectively of restructuring and related expenses.

(4) Included within operating expenses for the second quarter 2017 is an impairment charge of $31.0, associated with an early stage clinical indefinite-lived intangible asset.

Business Overview and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Retained Earnings (Accumulated Deficit)	$ 2,325.8				$ 2,242.1				$ 2,325.8	$ 2,242.1
Debt Issuance Costs, Net	20.8				21.0				20.8	21.0
Inventory, Net	472.5				460.4				472.5	460.4
Impairment of intangible assets									0.0	31.0	$ 85.0
Payments to Acquire Investments									$ 10.3	0.0	0.0
Purchase per share of fair market value of common stock (percent) (lower of)									85.00%
ESPP, discount (percent)									15.00%
Adoption of new guidance, value	6.1				(18.8)				$ 6.1	(18.8)	237.8
Total revenues	1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	909.7	$ 859.1	$ 912.7	$ 869.6	4,131.2	3,551.1	3,084.1
Net income	(45.0)	$ 330.9	$ (457.4)	$ 249.1	30.0	$ 78.0	$ 165.2	$ 170.1	$ 77.6	$ 443.3	$ 399.4
Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Accounts Receivable, Standard Credit Term									30 days
Accounts Receivable, Consolidated Average Term of Sales Outstanding									60 days
Inventory estimated life (in months)									36 months
Minimum [Member] \| Building and improvements
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									15 years
Minimum [Member] \| Machinery and laboratory equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									5 years
Minimum [Member] \| Computer hardware and software
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									3 years
Minimum [Member] \| Furniture and office equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									5 years
Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Accounts Receivable, Standard Credit Term									120 days
Accounts Receivable, Consolidated Average Term of Sales Outstanding									70 days
Inventory estimated life (in months)									48 months
Maximum [Member] \| Building and improvements
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									35 years
Maximum [Member] \| Machinery and laboratory equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									15 years
Maximum [Member] \| Computer hardware and software
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									7 years
Maximum [Member] \| Furniture and office equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives									10 years
Customer Concentration Risk [Member] \| Four Largest Customers [Member] [Member] \| Accounts Receivable [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									48.70%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Accounts Receivable [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales										57.70%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Accounts Receivable [Member] \| Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									14.00%	10.20%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Accounts Receivable [Member] \| Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									19.10%	18.90%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Sales Revenue, Product Line [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									50.30%	37.00%	36.70%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Sales Revenue, Product Line [Member] \| Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									10.00%	10.80%	10.00%
Customer Concentration Risk [Member] \| Three Largest Customers [Member] \| Sales Revenue, Product Line [Member] \| Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Percentage change in product sales									16.40%	15.00%	16.00%
Retained Earnings [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Adoption of new guidance, value	6.1				$ (18.8)				$ 6.1	$ (18.8)	$ 237.8
Net income									77.6	$ 443.3	$ 399.4
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Deferred Revenue												$ 10.4
Retained Earnings (Accumulated Deficit)	10.8								10.8
Contract with Customer, Asset, Net	$ 17.9								17.9
Total revenues									5.3
Net income									$ 4.8

Business Overview and Summary of Significant Accounting Policies (Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Business Overview and Summary of Significant Accounting Policies [Abstract]
Inventory, Raw Materials	$ 31.4	$ 4.7
Inventory, Work in Process	90.4	148.6
Inventory, Finished Goods	350.7	307.1
Inventory, Net	$ 472.5	$ 460.4

Business Overview and Summary of Significant Accounting Policies (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Overview and Summary of Significant Accounting Policies [Abstract]
Net income used for basic calculation	$ (45.0)	$ 330.9	$ (457.4)	$ 249.1	$ 30.0	$ 78.0	$ 165.2	$ 170.1	$ 77.6	$ 443.3	$ 399.4
Shares used in computing earnings per common share—basic									222.7	223.9	224.3
Weighted-average effect of dilutive securities:
Stock awards									1.8	1.5	2.0
Shares used in computing earnings per common share—diluted									224.5	225.4	226.3
Earnings per common share
Basic (in dollars per share)	$ (0.20)	$ 1.48	$ (2.05)	$ 1.12	$ 0.13	$ 0.35	$ 0.74	$ 0.76	$ 0.35	$ 1.98	$ 1.78
Diluted (in dollars per share)	$ (0.20)	$ 1.47	$ (2.05)	$ 1.11	$ 0.13	$ 0.35	$ 0.73	$ 0.75	$ 0.35	$ 1.97	$ 1.76
Antidilutive securities excluded from computation of EPS									2.8	4.0	4.2

Business Overview and Summary of Significant Accounting Policies Business Overview (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Accounts Receivable, Net, Current	$ 922.3	$ 726.5
Contract with Customer, Liability, Current	$ 3.4	$ 15.9

Acquisitions (Narrative) (Details) $ in Millions		1 Months Ended
Acquisitions (Narrative) (Details) $ in Millions	May 25, 2018 USD ($)	Nov. 30, 2018 USD ($)	Apr. 30, 2018 kr / shares
Syntimmune, Inc [Member]
Business Acquisition [Line Items]
Upfront payment for acquisition of Syntimmune outstanding shares		$ 400.0
Asset Acquisition, Contingent Consideration, Milestone Payments		800.0
Asset Acquisition, Potential Consideration Transfered, Including Contingent Consideration Milestone Payments		1,200.0
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, In-Process Research And Development		$ 379.3
In Process Research and Development [Member]
Business Acquisition [Line Items]
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Finite-Lived Intangibles	$ 803.7
Asset Acquisition, Share Price \| kr / shares			kr 232
Asset Acquisition, Potential Payments For Development, Regulatory, Commercial Milestones And Royalties On Sales	19.0
Upfront payment for acquisition of Syntimmune outstanding shares	$ 749.3

Acquisitions (Summary of Total Consideration) (Details) - In Process Research and Development [Member] $ in Millions	May 25, 2018 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Cash paid for acquisition of Wilson Therapeutics outstanding shares	$ 749.3
Transaction costs	15.1
Total consideration	764.4
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Cash And Equivalents	45.1
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Finite-Lived Intangibles	803.7
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Labor And Related Liabilities	(71.4)
Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities, Other	$ (13.0)

Acquisitions Syntimmune (Details) - Syntimmune, Inc [Member] $ in Millions	1 Months Ended
	Nov. 30, 2018 USD ($)
Consideration
Upfront payment for acquisition of Syntimmune outstanding shares	$ 400.0
Asset Acquisition, Cash Acquired	4.2
Asset Acquisition, Working Capital Adjustment	6.4
Transaction costs	0.9
Total consideration	411.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Cash	4.2
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, In-Process Research And Development	379.3
Deferred tax assets	25.1
Other assets and liabilities	2.9
Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Assets	$ 411.5

Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land	$ 9.6	$ 9.6
Buildings and improvements	520.1	427.9
Machinery and laboratory equipment	161.7	159.2
Computer hardware and software	144.8	141.5
Furniture and office equipment	27.5	23.8
Construction-in-progress	827.1	723.7
Property, Plant and Equipment, Gross	1,690.8	1,485.7
Less: Accumulated depreciation and amortization	(219.3)	(160.3)
Property, Plant and Equipment, Net	1,471.5	1,325.4
Depreciation and amortization of property, plant and equipment	405.3	496.7	$ 396.4
Computer software costs	50.3	58.2
Computer software, depreciation and amortization expense	17.4	16.0	12.4
Property, Plant, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization of property, plant and equipment	77.9	95.8	$ 64.0
MASSACHUSETTS \| Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross		64.1
Lonza Group AG [Member] \| Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 203.9	$ 180.6

Intangible Assets and Goodwill (Schedule of Intangible Assets and Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 322.0
Intangible Assets, Cost	4,760.4	$ 4,752.4
Intangible Assets, Accumulated Amortization	1,119.1	798.0
Intangible assets, net	3,641.3	3,954.4
Goodwill, Cost	5,040.3	5,040.3
Goodwill, Accumulated Amortization	2.9	2.9
Goodwill	5,037.4	5,037.4
Licensing Agreements [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	39.0	31.0
Finite-lived Intangible Assets, Accumulated Amortization	(29.3)	(28.5)
Finite-lived Intangible Assets, Net	9.7	2.5
Patents [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	10.5	10.5
Finite-lived Intangible Assets, Accumulated Amortization	(10.5)	(10.5)
Finite-lived Intangible Assets, Net	$ 0.0	0.0
Intangible Assets, Estimated Life (months)	7 years
Purchased Technology [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	$ 4,710.5	4,710.5
Finite-lived Intangible Assets, Accumulated Amortization	(1,079.1)	(758.9)
Finite-lived Intangible Assets, Net	3,631.4	3,951.6
Other Intangibles [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	0.4	0.4
Finite-lived Intangible Assets, Accumulated Amortization	(0.2)	(0.1)
Finite-lived Intangible Assets, Net	$ 0.2	$ 0.3
Intangible Assets, Estimated Life (months)	5 years
Minimum [Member] \| Licensing Agreements [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	5 years
Minimum [Member] \| Purchased Technology [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	6 years
Maximum [Member] \| Licensing Agreements [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	8 years
Maximum [Member] \| Purchased Technology [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	16 years

Intangible Assets and Goodwill Narratives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangibles Disclosure [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Year Two	$ 322.0
Finite-Lived Intangible Assets, Amortization Expense, Year Three	322.0
Finite-Lived Intangible Assets, Amortization Expense, Year Four	322.0
Finite-Lived Intangible Assets, Amortization Expense, Year Five	322.0
Impairment of intangible assets	0.0	$ 31.0	$ 85.0
Amortization of Intangible Assets	321.1	320.2	$ 322.2
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	322.0
Purchased Technology [Member]
Goodwill and Intangibles Disclosure [Line Items]
Finite-Lived Intangible Assets, Net	$ 3,631.4	$ 3,951.6

Marketable Securities (Summary of Avaiable-for-sale Securities Held) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 225.7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1
Debt Securities, Available-for-sale	225.6
Available-for-sale securities, amortized cost		$ 913.3
Available-for-sale securities, gross unrealized holding gains		0.7
Available-for-sale debt securities, gross unrealized holding losses		(0.4)
Available-for-sale securities, fair value		913.6
Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	52.1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.0
Debt Securities, Available-for-sale	52.1
Available-for-sale securities, amortized cost		16.0
Available-for-sale securities, gross unrealized holding gains		0.0
Available-for-sale debt securities, gross unrealized holding losses		0.0
Available-for-sale securities, fair value		16.0
Repurchase Agreements [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost		27.0
Available-for-sale securities, fair value		27.0
Corporate Bond Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	122.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1
Debt Securities, Available-for-sale	122.8
Available-for-sale securities, amortized cost		432.2
Available-for-sale securities, gross unrealized holding gains		0.5
Available-for-sale debt securities, gross unrealized holding losses		(0.2)
Available-for-sale securities, fair value		432.5
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	17.5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.0
Debt Securities, Available-for-sale	17.5
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost		426.3
Available-for-sale securities, gross unrealized holding gains		0.2
Available-for-sale debt securities, gross unrealized holding losses		(0.2)
Available-for-sale securities, fair value		426.3
Certificates of Deposit [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	33.2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0.0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.0
Debt Securities, Available-for-sale	$ 33.2
Available-for-sale securities, amortized cost		11.8
Available-for-sale securities, gross unrealized holding gains		0.0
Available-for-sale debt securities, gross unrealized holding losses		0.0
Available-for-sale securities, fair value		$ 11.8

Marketable Securities (Available-for-sale Securities by Classification in Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale	$ 225.6
Available-for-sale securities, fair value		$ 913.6
Cash and Cash Equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale	43.8
Available-for-sale securities, fair value		42.7
Marketable Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale	$ 181.8
Available-for-sale securities, fair value		$ 870.9

Marketable Securities (Available-for-sale Debt Securities by Contractual Maturity) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	$ 211.5
Available-for-sale Securities, Debt Maturities, Year Two Through Three, Fair Value	14.1
Available-for-sale Securities, Debt Maturities, Year Four Through Five, Fair Value	0.0
Debt Securities, Available-for-sale	$ 225.6

Marketable Securities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Aggregate fair value of available-for-sale debt securities in an unrealized loss position	$ 128.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 436.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		12.0
Debt Securities, Trading, and Equity Securities, FV-NI	$ 16.5	$ 18.5

Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 31, 2019
Derivative [Line Items]
Estimated amount to be reclassified from other comprehenisve income in next year	$ 9.8
Gain in other income and expense	$ 23.0	$ (14.7)	$ (5.2)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign exchange forward contracts durations (months)	60 months
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign exchange forward contracts durations (months)	6 months
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Estimated amount to be reclassified from other comprehenisve income in next year	$ 19.3
Foreign Exchange Forward [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	991.1
Foreign Exchange Forward [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	1,511.6
Foreign Exchange Forward, Open Expense [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	20.3
Interest Rate Swap One [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	2,031.3
Interest Rate Swap Three [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 300.0
Derivative fixed interest rate	2.08%
Interest Rate Swap Four [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 1,100.0
Subsequent Event [Member] \| Interest Rate Swap Five [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts				$ 200.0
Derivative fixed interest rate				2.37%

Derivative Instruments and Hedging Activities (Schedule Of Other Comprehensive Income And Earnings From Foreign Exchange Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Foreign Exchange Contract [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in AOCI, net of tax	$ 37.7	$ (96.1)	$ 40.2
Foreign Exchange Contract [Member] \| Net product sales
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) reclassified from AOCI to net product sales (Effective portion), net of tax	(1.4)	18.7	47.3
Interest Rate Contract [Member] \| Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in AOCI, net of tax	(4.8)	7.9	6.2
Gain (loss) reclassified from AOCI to net product sales (Effective portion), net of tax	$ 10.8	$ (1.1)	$ (0.1)

Derivative Instruments and Hedging Activities (Schedule Of Fair Value Of Outstanding Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 60.9	$ 48.8
Liability Derivatives, Fair Value	40.0	74.5
Foreign Exchange Forward [Member] \| Other Current Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	7.3	34.8
Foreign Exchange Forward [Member] \| Other Current Liabilities [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	11.5	13.7
Foreign Exchange Forward [Member] \| Other Non Current Assets [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	0.3	4.1
Foreign Exchange Forward [Member] \| Other Non Current Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	3.1	26.0
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	16.9	12.9
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 23.6	10.0
Interest Rate Contract [Member] \| Other Current Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value		0.0
Interest Rate Contract [Member] \| Other Non Current Assets [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value		12.5
Interest Rate Contract [Member] \| Other Non Current Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value		0.0
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value		$ 9.3

Derivative Instruments and Hedging Activities (Schedule of Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Asset Derivatives, Fair Value	$ 60.9	$ 48.8
Derivative Asset, Fair Value, Gross Liability	0.0	0.0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	60.9	48.8
Derivative, Collateral, Obligation to Return Securities	(30.2)	(26.3)
Derivative, Collateral, Obligation to Return Cash	0.0	0.0
Derivative Asset, Fair Value, Amount Offset Against Collateral	30.7	22.5
Derivative Liability, Fair Value, Gross Liability	(40.0)	(74.5)
Derivative Liability, Fair Value, Gross Asset	0.0	0.0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	40.0	74.5
Derivative, Collateral, Right to Reclaim Securities	30.2	26.3
Derivative, Collateral, Right to Reclaim Cash	0.0	0.0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 9.8	$ 48.2

Derivative Instruments and Hedging Activities Schedule of Interest Rate Derivatives (Details) - Designated as Hedging Instrument [Member] $ in Millions	Dec. 31, 2018 USD ($)
Interest Rate Swap One [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 2,031.3
Interest Rate Swap One [Member] \| Minimum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	0.98%
Interest Rate Swap One [Member] \| Maximum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	1.62%
Interest Rate Swap Two [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 450.0
Interest Rate Swap Two [Member] \| Minimum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	2.60%
Interest Rate Swap Two [Member] \| Maximum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	2.79%
Interest Rate Swap Three [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 300.0
Derivative, Fixed Interest Rate	2.08%
Interest Rate Swap Four [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 1,100.0
Interest Rate Swap Four [Member] \| Minimum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	2.70%
Interest Rate Swap Four [Member] \| Maximum [Member]
Derivative [Line Items]
Derivative, Variable Interest Rate	2.83%

Derivative Instruments and Hedging Activities Schedule of Cash Flow Hedges in AOCI (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total revenues	$ 1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	$ 909.7	$ 859.1	$ 912.7	$ 869.6	$ 4,131.2	$ 3,551.1	$ 3,084.1
Interest Expense									98.2	98.4	96.9
Product [Member]
Derivative [Line Items]
Total revenues									4,130.1	3,549.5	3,081.7
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Foreign Exchange Forward [Member]
Derivative [Line Items]
Total revenues									(1.8)	28.9	73.0
Interest Expense									0.0	0.0	0.0
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Total revenues									0.0	0.0	0.0
Interest Expense									$ (13.6)	$ 1.8	$ 0.2

Derivative Instruments and Hedging Activities Schedule of Cash Flow Hedges in AOCI (Nine months) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Interest Expense	$ 98.2	$ 98.4	$ 96.9

Derivative Instruments and Hedging Activities Rev from Contract (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total revenues	$ 1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	$ 909.7	$ 859.1	$ 912.7	$ 869.6	$ 4,131.2	$ 3,551.1	$ 3,084.1
Interest expense									(98.2)	(98.4)	(96.9)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] \| Foreign Exchange Forward [Member]
Derivative [Line Items]
Total revenues									(1.8)	28.9	73.0
Interest expense									0.0	0.0	0.0
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Total revenues									0.0	0.0	0.0
Interest expense									$ 13.6	$ (1.8)	$ (0.2)

Other Investments (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
Other Investments (Details) - USD ($) $ in Millions	Oct. 31, 2018	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrealized Gain (Loss) on Investments				$ 40.2	$ 0.0	$ 0.0
Moderna LLC [Member]
Payments to Acquire Other Investments		$ 81.9		81.9	$ 37.5
Unrealized Gain (Loss) on Investments		(56.4)	$ 100.8
Dicerna [Member]
Payments to Acquire Equity Method Investments	$ 10.3
Unrealized Gain (Loss) on Investments		1.4
Equity Securities, FV-NI		$ 8.9		$ 8.9

Other Investments Moderna Investment (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrealized Gain (Loss) on Investments			$ 40.2	$ 0.0	$ 0.0
Moderna LLC [Member]
Unrealized Gain (Loss) on Investments	$ (56.4)	$ 100.8
Equity Method Investments	$ 81.9		$ 81.9	$ 37.5

Accounts Payable and Accrued Expenses (Schedule of Accrued Expenses) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities [Abstract]
Accounts Payable	$ 74.4	$ 70.8
Royalties	27.0	22.5
Payroll and employee benefits	170.4	149.9
Taxes payable	24.4	30.7
Rebates payable	122.8	99.1
Clinical	58.6	79.1
Manufacturing	72.0	41.1
Restructuring Reserve, Current	4.2	58.2
Other	144.4	158.8
Accounts Payable and Accrued Liabilities, Current	$ 698.2	$ 710.2

Debt (Details) $ in Millions		12 Months Ended
Debt (Details) $ in Millions	Jun. 22, 2015	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 07, 2018 USD ($)
Debt Instrument [Line Items]
Proceeds from revolving credit facility		$ 250.0	$ 0.0	$ 0.0
Amortization of Financing Costs		8.0	9.2	10.3
Debt Issuance Costs, Net		20.8	21.0
Repayments of Long-term Debt		293.8	175.0	$ 375.0
Current portion of long-term debt		$ 93.8	167.4
Credit Agreement [Member]
Debt Instrument [Line Items]
Payments of Financing Costs			$ 53.1
Senior Secured Term Loan [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate at Period End		3.90%
Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Letters of credit, amount outstanding		$ 1.7
Eurodollar [Member] \| Minimum [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	1.25%
Eurodollar [Member] \| Maximum [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	2.00%
Base Rate [Member] \| Minimum [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	0.25%
Base Rate [Member] \| Maximum [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	1.00%
Revolving Credit Facility [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 1,000.0
Debt Instrument, Covenant Compliance, Net Debt To EBITDA					3.50
Debt Instrument, Covenant Compliance, EBITDA To Cash Interest Expense, Minimum					3.50
Revolving Credit Facility [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Long-term debt		250.0
Proceeds from revolving credit facility		250.0
Senior Secured Term Loan [Member] \| Line of Credit [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount					$ 2,612.5
Debt Instrument, Quarterly Payment, Percentage of Total Borrowings					5.00%
Long-term debt		$ 2,612.5

Debt - Schedule of Maturities of Long-term Debt (Details) $ in Millions	Dec. 31, 2018 USD ($)
Debt Disclosure [Abstract]
2019	$ 348.0
2020	130.6
2021	130.6
2022	130.6
2023	$ 2,122.7

Facility Lease Obligations (Details) $ in Millions	3 Months Ended	12 Months Ended
Facility Lease Obligations (Details) $ in Millions	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)	Sep. 30, 2017
Operating Leased Assets [Line Items]
Facility lease obligation	$ 361.0	$ 361.0	$ 342.9
Property, Plant and Equipment, Gross	1,690.8	1,690.8	1,485.7
Payment To Third Party, Lease Incentive	53.0
Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		73.8
Lonza Group AG [Member] \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Property, Plant and Equipment, Gross	203.9	$ 203.9	180.6
Lonza Group AG [Member] \| Facility Lease Obligation [Member]
Operating Leased Assets [Line Items]
Facility Lease Obligation, Payment Period		10 years
Facility lease obligation	155.1	$ 155.1	159.1
CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Facility lease obligation, interest expense		13.3	14.2	$ 14.0
CONNECTICUT \| Facility Lease Obligation [Member]
Operating Leased Assets [Line Items]
Facility lease obligation	133.5	133.5	134.6
MASSACHUSETTS
Operating Leased Assets [Line Items]
Facility lease obligation	$ 83.6	83.6	$ 59.6
Area of office space (square feet) \| ft²			150,000
MASSACHUSETTS \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Property, Plant and Equipment, Gross			$ 64.1
Minimum [Member] \| MASSACHUSETTS
Operating Leased Assets [Line Items]
Operating leases, renewal term					10 years
Facility Lease Obligation [Member] \| Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		9.6
Inventories [Member] \| Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		$ 64.2
Facility Lease Obligation \| CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	11.00%	11.00%

Facility Lease Obligations - Aggregate Future Minimum Non-cancellable Commitments Under Facility Lease Obligation (Details) $ in Millions	Dec. 31, 2018 USD ($)
CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
2019	$ 9.4
2020	8.8
2021	9.0
2022	9.2
2023	9.2
Thereafter	63.9
MASSACHUSETTS
Operating Leased Assets [Line Items]
2019	4.3
2020	6.6
2021	6.7
2022	6.8
2023	7.0
Thereafter	$ 56.7

Commitments and Contingencies (Narrative) (Details) - USD ($)
$ in Millions

1 Months Ended

3 Months Ended

12 Months Ended

Oct. 31, 2018

Dec. 31, 2018

Sep. 30, 2018

^[1]

Jun. 30, 2018

^[2]

Mar. 31, 2018

^[1]

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Commitments and Contingencies [Line Items]

Research and Development Expense

$ 730.4

$ 878.4

$ 757.2

Other Commitment, potential payment

$ 104.1

104.1

Total operating expenses

988.3

$ 577.3

$ 1,349.8

$ 571.9

$ 656.5

^[3]

$ 622.0

$ 602.4

$ 588.6

3,487.3

2,469.5

2,158.4

Property, Plant and Equipment, Gross

1,690.8

1,485.7

1,690.8

1,485.7

Facility lease obligation

361.0

342.9

361.0

342.9

Lonza Agreement [Member]

Commitments and Contingencies [Line Items]

Remaining total commitments with Lonza

1,084.6

MASSACHUSETTS

Commitments and Contingencies [Line Items]

Facility lease obligation

83.6

59.6

83.6

59.6

MASSACHUSETTS | Minimum [Member]

Commitments and Contingencies [Line Items]

Operating leases, renewal term

10 years

Construction in Progress [Member] | MASSACHUSETTS

Commitments and Contingencies [Line Items]

Property, Plant and Equipment, Gross

$ 64.1

64.1

Property, Plant and Equipment, Other Types [Member]

Commitments and Contingencies [Line Items]

Lease expense

24.4

$ 27.2

$ 29.3

DOJ And OIG [Member]

Commitments and Contingencies [Line Items]

Loss Contingency Accrual

13.0

Halozyme Therapeutics, Inc [Member] | License Agreement 1 [Member]

Commitments and Contingencies [Line Items]

Research and development expense, upfront payment

40.0

Research and development arrangement, potential payment, maximum

160.0

Dicerna Pharmaceutical Collaboration Agreement [Member] | Dicerna [Member]

Commitments and Contingencies [Line Items]

Payments To Acquire Licenses And Equity Investment

$ 37.0

Research and Development Expense

$ 26.7

Collaboration Agreement, Potential Future Payments, Milestone Achievement

625.0

Collaboration and License Agreement [Member]

Commitments and Contingencies [Line Items]

Collaboration Agreement, Potential Future Payments, Milestone Achievement

$ 137.2

[1]	Included within operating expenses for the first and third quarters 2017 are $23.8 and $79.4, respectively of restructuring and related expenses.
[2]	We recognized a tax (benefit) expense of $(56.5) and $45.8 in 2018 and 2017, respectively, as a result of the Tax Cuts and Jobs Act. In 2017, we recorded certain impacts of the Tax Act on a provisional basis. As of December 22, 2018, our accounting for the impact of the Tax Act was complete. See Note 12, “Income Taxes” for additional information.
[3]	(5) We recognized a tax (benefit) expense of $(56.5) and $45.8 in 2018 and 2017, respectively, as a result of the Tax Cuts and Jobs Act. In 2017, we recorded certain impacts of the Tax Act on a provisional basis. As of December 22, 2018, our accounting for the impact of the Tax Act was complete. See Note 12, “Income Taxes” for additional information.

Commitments and Contingencies (Schedule of Aggregate Future Minimum Annual Rental Payments) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Property, Plant and Equipment, Other Types [Member]
Operating Leased Assets [Line Items]
2019	$ 14.1
2020	9.3
2021	5.6
2022	3.9
2023	3.5
Thereafter	11.6
CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
2019	9.4
2020	8.8
2021	9.0
2022	9.2
2023	9.2
Thereafter	$ 63.9

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Current Foreign Tax Expense (Benefit)	$ 74.7	$ 107.5	$ 69.1
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	$ 54.2	$ 33.2	$ 48.3
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Percent	1.60%	3.90%	0.90%
Foreign Earnings Repatriated	$ 206.1	$ 171.7	$ 103.9
Income tax expense	(164.6)	(104.5)	(176.8)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	$ 21.1
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent	8.70%
Effective Income Tax Rate Reconciliation, Foreign-Derived Intangible Income, Amount	$ 10.9
Effective Income Tax Rate Reconciliation, Foreign-Derived Intangible Income, Percent	4.50%
Repatriation of foreign earnings, amount	$ 108.7	$ 35.4	$ 155.4
Foreign income subject to U.S. taxation	44.80%	6.50%	27.00%
Effective Income Tax Rate Reconciliation, Repatriation Of Captive Foreign Partnership Earnings, Amount			$ 119.3
Change in unrecognized tax benefits	$ 35.4	$ 27.1	21.5
Statute of limitations, minimum (years)	3 years
Statute of limitations, maximum (years)	6 years
Decreases for tax positions taken during a prior period	$ (5.8)	(85.8)	(1.1)
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	0.0	15.8	$ 0.0
Effective income tax rate reconciliation, Tax Cuts and Jobs Act of 2017, amount	$ (56.5)	$ 45.8
Effective income tax rate reconciliation, Tax Cuts and Jobs Act of 2017, percent		0.084
Tax Cuts and Jobs Act of 2017, transition tax, Income expense		$ 177.9
Tax Cuts and Jobs Act of 2017, transition tax, estimated tax credits		$ 28.0
Tax Cuts and Jobs Act of 2017, Transition tax, Income expense, percent		32.50%
Tax Cuts and Jobs Act of 2017, transition tax, foreign income subject to domestic taxation		$ 195.6
Tax Cuts and Jobs Act of 2017, transition tax, foreign tax credit		17.7
Tax Cuts and Jobs Act of 2017, deferred tax asset, income tax expense, amount		$ 292.4
Other permanent differences	0.00%	53.40%	0.00%
Tax Cuts and Jobs Act of 2017, income tax expense, amount, foreign income subject to domestic taxation		$ 121.3
Tax Cuts and Jobs Act of 2017, income tax expense, amount, foreign income subject to domestic taxation, percent		(22.20%)
Tax Cuts and Jobs Act of 2017, income tax benefit, foreign tax credits	$ 67.7	$ 171.1
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Benefit, Foreign, Percent	28.00%
Tax Cuts and Jobs Act of 2017, income tax benefit, foreign tax credits, percent		(31.20%)
Tax Cuts and Jobs Act of 2017, deferred tax liability, income tax benefit		$ (5.1)
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit), Permanent Differences, Percentage	0.90%
Tax Cut and Jobs Act of 2017, global intangible low-taxed income minimum tax, income tax expense		$ 165.4
Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Change In Income Tax Rate, Percent		62.70%
Effective Income Tax Rate Reconciliation, Tax Cut And Jobs Act 2017, Global Intangible Low-Taxed Income Minimum Tax, Percent		30.20%
Tax Cut and Jobs Act of 2017, global intangible low-taxed income minimum tax, income tax expense, deferred tax expense	$ 67.7	$ 236.9
Tax Cuts and Jobs Act of 2017, estimated deferred tax liabilities, foreign	$ 11.1	533.4
Tax Cut and Jobs Act of 2017, global intangible low-taxed income minimum tax, income tax benefit, unrecognized tax benefit		$ 71.5
Decrease effective tax rate		3.60%
Increase in effective tax rate	68.00%	19.10%	30.70%
Increase In effective rate			20.70%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act of 2017, Transition Tax on Accumulated Foreign Earnings, Amount	$ (24.1)
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	20.0
Income tax credit carryforwards	370.6
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Current Foreign Tax Expense (Benefit)	58.1	$ 54.4	$ 42.8
Net operating loss carryforwards	11.6
Income tax credit carryforwards	8.4
Tax Cuts and Jobs Act of 2017, deferred tax asset, income tax expense, amount		2.9
Tax Cuts and Jobs Act of 2017, deferred tax liability, estimated increase in income tax payable		2.2
Tax Cuts and Jobs Act of 2017, deferred tax asset, estimated increase in deferred taxes		$ 0.7
In Process Research and Development [Member] \| Wilson Therapeutics And Syntimmune [Member]
Income Tax Contingency [Line Items]
Income tax expense	$ (248.4)
In Process Research and Development [Member] \| Wilson Therapeutics [Member]
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	69.70%
In Process Research and Development [Member] \| Syntimmune, Inc [Member]
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	32.90%

Income Taxes (Schedule of Income Tax Provision (Benefit) on Income Before Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S.	$ (451.4)	$ (43.9)	$ (164.6)
Non-U.S.	693.6	591.7	740.8
Income before income taxes	$ 242.2	$ 547.8	$ 576.2

Income Taxes (Schedule of Components of Income Tax Provision (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Domestic
Current	$ 57.0	$ 42.9	$ 3.4
Deferred	49.5	7.2	107.6
Total Domestic	106.5	50.1	111.0
Foreign
Current	74.7	107.5	69.1
Deferred	(16.6)	(53.1)	(3.3)
Total Foreign	58.1	54.4	65.8
Total
Current	131.7	150.4	72.5
Deferred	32.9	(45.9)	104.3
Income Tax Expense (Benefit)	$ 164.6	$ 104.5	$ 176.8

Income Taxes (Reconciliation of the Statutory U.S. Federal Income Tax Rate to Effective Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	21.00%	35.00%	35.00%
State and local income taxes	14.20%	1.50%	4.10%
Tax credits	(71.20%)	60.10%	(7.20%)
Tax reserves	(17.00%)	(10.70%)	(6.00%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent	12.10%	(14.00%)	2.70%
Foreign income subject to U.S. taxation	44.80%	6.50%	27.00%
Other permanent differences	(0.00%)	(53.40%)	(0.00%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Research and Development, Percent	102.60%	0.00%	0.00%
Other permanent differences	6.30%	0.60%	2.10%
Effective income tax rate	68.00%	19.10%	30.70%

Income Taxes (Schedule of Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 41.8	$ 4.9
Income tax credits	371.6	442.5
Stock compensation	47.6	66.6
Accruals and allowances	105.8	97.7
Unrealized losses	0.0	6.6
Research and development expenses	5.2	7.2
Accrued royalties	89.1	74.2
Gross deferred tax assets	661.1	699.7
Valuation allowance	(19.6)	(3.4)
Total deferred tax assets	641.5	696.3
Deferred tax liabilities:
Depreciable assets	(88.7)	(75.2)
Unrealized gains	(6.6)	0.0
Investment in foreign partnership	(566.6)	(607.9)
Intangible assets	(268.8)	(285.6)
Total deferred tax liabilities	(930.7)	(968.7)
Net deferred tax (liability) asset	$ (289.2)	$ (272.4)

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning of period balance	$ 60.9	$ 138.9	$ 113.9
Increases for tax positions taken during a prior period	9.1	5.6	3.4
Decreases for tax positions taken during a prior period	(5.8)	(85.8)	(1.1)
Increases for tax positions taken during the current period	28.8	19.3	22.8
Decreases for tax positions related to settlements	0.0	(15.8)	0.0
Decreases for tax positions related to lapse of statute	(0.3)	(1.3)	(0.1)
End of period balance	$ 92.7	$ 60.9	$ 138.9

Share-based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum contractual term under all plans (in years)	10
Total compensation cost not yet recognized on non-vested awards	$ 312.7
Period for rececognition for compensation cost not yet recognized of non-vested awards	1 year 8 months 12 days
Total intrinsic value of stock options exercised	$ 27.5	$ 88.9	$ 41.7
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value	$ 27.2	$ 61.5	$ 58.1
Weighted average fair value at the date of grant for options granted		$ 42.59	$ 41.46
Restricted Stock, Grants in Period	2,100,000
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value	$ 119.27
Allocated Share-based Compensation Expense	$ 203.0	$ 243.1	$ 192.3
Purchase per share of fair market value of common stock (percent) (lower of)	85.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	4 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	4 years
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value	$ 119.27	$ 125.39	$ 133.35
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value	$ 181.7	$ 157.0	$ 124.4
Market-Based Performance [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 14.9
Performance-based Restricted Stock Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	3 years
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares authorized	1,000,000.000
Inventory [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 14.5	$ 15.4	$ 12.1
2017 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares authorized	18,200,000

Share-based Compensation (Schedule of Components of Allocated Share-Based Compensation Expense and Capitalization of Share Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Period for rececognition for compensation cost not yet recognized of non-vested awards	1 year 8 months 12 days
Total share-based compensation expense	$ 203.0	$ 243.1	$ 192.3
Income tax effect	(46.5)	(89.3)	(70.3)
Total share-based compensation expense, net of tax	156.5	153.8	122.0
Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	16.0	11.1	11.1
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	57.5	76.4	57.6
Selling, General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 129.5	$ 155.6	$ 123.6

Share-based Compensation (Schedule of Status of Stock Option Plans) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period, Number of shares \| shares	5.3
Outstanding at beginning of period, Weighted Average Exercise Price \| $ / shares	$ 124.71
Granted, Number of shares \| shares	0.0
Granted, Weighted Average Exercise Price \| $ / shares	$ 0.00
Exercised, Number of shares \| shares	(0.5)
Exercised, Weighted Average Exercise Price \| $ / shares	$ 82.70
Forfeited and cancelled, Number of shares \| shares	(1.2)
Forfeited and cancelled, Weighted Average Exercise Price \| $ / shares	$ 156.20
Outstanding at end of period, Number of shares \| shares	3.6
Outstanding at end of period, Weighted Average Exercise Price \| $ / shares	$ 119.68
Outstanding at end of period, Weighted Average Remaining Contractual Term (in years)	4 years 7 months 59 days
Outstanding at end of period, Aggregate Intrinsic Value \| $	$ 44.5
Vested and unvested expected to vest at end of period, Number of shares \| shares	3.6
Vested and unvested expected to vest at end of period, Weighted Average Exercise Price \| $ / shares	$ 119.63
Vested and unvested expected to vest at end of period, Weighted Average Remaining Contractual Term (in years)	4 years 7 months 55 days
Vested and unvested expected to vest at end of period, Aggregate Intrinsic Value \| $	$ 44.5
Exercisable at end of period, Number of shares \| shares	3.2
Exercisable at end of period, Weighted Average Exercise Price \| $ / shares	$ 117.73
Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	4 years 3 months 48 days
Exercisable at end of period, Aggregate Intrinsic Value \| $	$ 44.5

Share-based Compensation (Schedule of Ranges of Weighted Average Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate, minimum	1.64%	0.87%
Interest rate, maximum	1.92%	1.66%
Volatility, minimum	38.78%	33.45%
Volatility, maximum	39.01%	37.61%
Dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years, minimum	4 years 25 days	3 years 9 months 26 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years, minimum	4 years 3 months 14 days	6 years 3 months 15 days

Share-based Compensation (Schedule of Status of Non-Vested Restricted Stock) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested restricted stock, beginning of period \| shares	3.6
Shares issued \| shares	2.1
Shares cancelled \| shares	(0.7)
Shares vesting \| shares	(1.3)
Nonvested restricted stock, end of period \| shares	3.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average grant date fair value \| $ / shares	$ 130.75
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	119.27
Cancelled, Weighted average grant date fair value \| $ / shares	126.78
Vested, Weighted average grant date fair value \| $ / shares	135.17
Weighted average grant date fair value \| $ / shares	$ 123.25

Stockholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 06, 2019	Feb. 13, 2017
Class of Stock [Line Items]
Repurchase of common stock	$ 85.0	$ 463.6	$ 430.6
Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 1,000.0
Repurchase of common stock, shares	0.7	4.0
Subsequent Event [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 451.5
Common Stock [Member]
Class of Stock [Line Items]
Repurchase of common stock, shares		0.0

Other Comprehensive Income and Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	$ (34.4)	$ 60.5	$ 62.3
Other Comprehensive Income before Reclassifications	34.0	(79.5)	44.9
Amounts reclassified from other comprehensive income	(9.3)	(15.4)	(46.7)
Other comprehensive income (loss), net of tax	24.7	(94.9)	(1.8)
Accumulated comprehensive income (loss), Ending balance	(9.7)	(34.4)	60.5
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(4.8)	(6.7)	(9.6)
Other Comprehensive Income before Reclassifications	1.5	0.5	2.6
Amounts reclassified from other comprehensive income	0.7	1.4	0.3
Other comprehensive income (loss), net of tax	2.2	1.9	2.9
Accumulated comprehensive income (loss), Ending balance	(2.6)	(4.8)	(6.7)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	0.2	(0.4)	(0.8)
Other Comprehensive Income before Reclassifications	0.1	(0.2)	0.2
Amounts reclassified from other comprehensive income	(0.6)	0.8	0.2
Other comprehensive income (loss), net of tax	(0.5)	0.6	0.4
Accumulated comprehensive income (loss), Ending balance	(0.3)	0.2	(0.4)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(13.9)	91.9	92.7
Other Comprehensive Income before Reclassifications	32.9	(88.2)	46.4
Amounts reclassified from other comprehensive income	(9.4)	(17.6)	(47.2)
Other comprehensive income (loss), net of tax	23.5	(105.8)	(0.8)
Accumulated comprehensive income (loss), Ending balance	9.6	(13.9)	91.9
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(15.9)	(24.3)	(20.0)
Other Comprehensive Income before Reclassifications	(0.5)	8.4	(4.3)
Amounts reclassified from other comprehensive income	0.0	0.0	0.0
Other comprehensive income (loss), net of tax	(0.5)	8.4	(4.3)
Accumulated comprehensive income (loss), Ending balance	$ (16.4)	$ (15.9)	$ (24.3)

Other Comprehensive Income and Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($)
$ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Total revenues

$ 1,128.8

$ 1,026.5

$ 1,045.0

$ 930.9

$ 909.7

$ 859.1

$ 912.7

$ 869.6

$ 4,131.2

$ 3,551.1

$ 3,084.1

Other income and (expense)

(4.8)

9.4

(6.9)

Interest expense

(98.2)

(98.4)

(96.9)

Income before income taxes

242.2

547.8

576.2

Income tax expense

(164.6)

(104.5)

(176.8)

Net income

$ (45.0)

$ 330.9

$ (457.4)

$ 249.1

$ 30.0

$ 78.0

$ 165.2

$ 170.1

77.6

443.3

399.4

Reclassification from accumulated other comprehensive income, net

9.3

15.4

46.7

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Reclassification from accumulated other comprehensive income, net

9.4

17.6

47.2

Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Defined Benefit Pension Items

^[1]

(0.3)

(0.4)

(0.5)

Accumulated Defined Benefit Plans Adjustment, Net Curtailment Attributable to Parent [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Defined Benefit Pension Items

^[1]

(0.6)

(1.8)

0.0

Accumulated Net Unrealized Investment Gain (Loss) [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Reclassification from accumulated other comprehensive income, net

0.6

(0.8)

(0.2)

Accumulated Defined Benefit Plans Adjustment [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Defined Benefit Pension Items

(0.9)

(2.2)

(0.5)

Income tax expense

(0.2)

(0.8)

(0.2)

Reclassification from accumulated other comprehensive income, net

(0.7)

(1.4)

(0.3)

Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Income before income taxes

11.8

27.1

72.8

Income tax expense

(2.4)

(9.5)

(25.6)

Net income

9.4

17.6

47.2

Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Interest expense

13.6

(1.8)

(0.2)

Net product sales

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Total revenues

4,130.1

3,549.5

3,081.7

Net product sales | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign Exchange Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Reclassification out of Accumulated Other Comprehensive Income [Line Items]

Total revenues

$ (1.8)

$ 28.9

$ 73.0

[1]	This AOCI component is included in the computation of net periodic pension benefit cost (see Note 17, Employee Benefit Plans, for additional details).

Fair Value Measurement (Schedule Of Acquisition-Related Contingent Consideration) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration arrangements, range of outcomes, value, low	$ 0.0	$ 0.0
Contingent consideration arrangements, range of outcomes, value, high	702.0	702.0
Contingent consideration	183.2	183.2	$ 168.9
Acquisition-Related Contingent Consideration [Roll Forward]
Amounts derecognized upon sale of asset		0.0	7.0	$ 60.0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		116.5	41.0	$ 35.7
Acquisition Related Contingent Consideration [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	280.8	280.8
Acquisition Related Contingent Consideration [Member] \| Level 3 [Member]
Acquisition-Related Contingent Consideration [Roll Forward]
Balance at beginning of period		168.9
Amounts derecognized upon sale of asset		(4.6)
Changes in fair value		116.5
Balance at end of period	280.8	$ 280.8	$ 168.9
Acquisition Related Contingent Consideration [Member] \| Minimum [Member] \| Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Inputs, Cost of Debt		4.20%
Fair Value Inputs, Weighted Average Cost of Capital		9.00%
Acquisition Related Contingent Consideration [Member] \| Maximum [Member] \| Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Inputs, Cost of Debt		5.10%
Fair Value Inputs, Weighted Average Cost of Capital		21.00%
ALXN1101 Program [Member] \| Discontinued Operations, Disposed of by Sale [Member]
Acquisition-Related Contingent Consideration [Roll Forward]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	4.6
Enobia Pharma Corp. [Member] \| Discontinued Operations, Disposed of by Means Other than Sale [Member]
Acquisition-Related Contingent Consideration [Roll Forward]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 48.7

Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
Employee Benefit Plans (Narrative) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Deferred Compensation Arrangement with Individual, Voluntary Deferrals, Percent of Employees' Gross Pay, Maximum	80.00%
Deferred Compensation Arrangement with Individual, Employer Matching Contribution, Percent of Match	6.00%
Amount of each dollar matching contributed up to first six percent of individual base salary and incentive cash bonus	$ 1.00
Percentage of contribution of individual's base salary and incentive cash bonus	6.00%
Defined benefit plan, contributions by employer	$ 14,100,000	$ 15,900,000	$ 16,700,000
Additional minimum liability recorded in other non-current liabiliites	17,600,000
Additional minimum liability charged against other comprehensive income	2,600,000
Estimated future employer contributions in next fiscal year	2,400,000
Other Liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation liability	$ 16,500,000	$ 18,500,000

Employee Benefit Plans (Schedule of Change in Benefit Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation, beginning of year	$ 43.4	$ 48.4
Service cost	6.3	7.8	$ 8.2
Curtailment	3.8	9.6
Other	(6.5)	(3.2)
Projected benefit obligation, end of year	39.4	43.4	$ 48.4
Accumulated benefit obligation, end of year	$ 36.1	$ 39.4

Employee Benefit Plans (Schedule of Change in Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 3.0	$ 4.3
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	1.3	1.5
Change in plan assets:
Fair value of plan assets, beginning of year	24.2	28.2
Fair value of plan assets, end of year	21.8	24.2
Funded status at end of year	(17.6)	(19.2)
Defined Benefit Plan, Curtailments, Plan Assets	(2.4)	(6.6)
Defined Benefit Plan, Fair Value of Plan Assets, Other Increase (Decrease)	$ (4.3)	$ (3.2)

Employee Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 21.8	$ 24.2	$ 28.2

Employee Benefit Plans (Schedule of Weighted Average Assumptions Used to Calculate Net Periodic Benefit Cost and the Actuarial Present Value of Projected Benefit Obligations) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Weighted average assumptions - Net Periodic Benefit Cost:
Discount rate	0.80%	0.70%
Long term rate of return on assets	2.50%	3.00%
Rate of compensation increase	1.30%	1.40%
Weighted average assumptions - Projected Benefit Obligation:
Discount Rate	0.80%	0.80%
Rate of compensation increase	1.30%	1.30%

Employee Benefit Plans (Schedule of Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 6.3	$ 7.8	$ 8.2
Employee contributions	(1.3)	(1.5)	(1.6)
Amortization of prior service costs	(0.3)	(0.4)	0.0
Curtailment	(0.8)	(1.1)	0.0
Amortization and deferral of actuarial gain	0.5	0.8	0.9
Other	(0.3)	(0.6)	(0.8)
Total net periodic benefit cost	$ 4.1	$ 5.0	$ 6.7

Employee Benefit Plans (Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Roll Forward]
Amount included in AOCI - Beginning of year	$ (4.8)	$ (6.7)
Prior service cost	(0.3)	(0.4)
Amortization of net gain (loss)	0.6	0.8
Curtailment	0.6	1.9
Taxes	(0.7)	(0.6)
Other	2.0	0.2
Amount included in AOCI - End of year	$ (2.6)	$ (4.8)

Employee Benefit Plans (Schedule of Estimated Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Retirement Benefits [Abstract]
2019	$ 1.9
2020	1.7
2021	1.7
2022	1.9
2023	1.6
2024 to 2028	$ 9.1

Restructuring and Related Expenses (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Current	$ 4.2				$ 58.2				$ 4.2	$ 58.2
Restructuring and Related Cost, Number of Positions Eliminated, Period Percent									20.00%
Restructuring expenses	79.4				23.8				$ 50.7	286.5	$ 3.0
Total revenues	1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	909.7	$ 859.1	$ 912.7	$ 869.6	4,131.2	3,551.1	3,084.1
Accrued Grant Income Refund, Current					$ 26.0					26.0
Restructuring and Related Cost, Expected Cost	$ 25.0								25.0
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses									$ 4.6	$ 87.3	3.0
Grant [Member]
Restructuring Cost and Reserve [Line Items]
Total revenues											$ 26.0

Restructuring and Related Expenses - Reconciliation of Restructuring Reserve (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Liability, beginning of period			$ 58.2	$ 0.6
Charges			52.2	287.4
Cash settlements			(79.4)	(49.6)
Adjustments to previous estimates			(1.5)	(0.9)
Non Cash Activity			(25.3)	(179.3)
Liability, end of period	$ 4.2	$ 58.2	4.2	58.2	$ 0.6
Restructuring Reserve, Current	4.2	58.2	4.2	58.2
Restructuring expenses	79.4	23.8	50.7	286.5	3.0
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period			53.8	0.5
Charges			5.8	88.2
Cash settlements			(54.2)	(34.0)
Adjustments to previous estimates			(1.2)	(0.9)
Non Cash Activity			0.0	0.0
Liability, end of period	4.2	53.8	4.2	53.8	0.5
Restructuring expenses			4.6	87.3	3.0
Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period			4.4	0.1
Charges			21.1	19.9
Cash settlements			(25.2)	(15.6)
Adjustments to previous estimates			(0.3)	0.0
Non Cash Activity			0.0	0.0
Liability, end of period	0.0	4.4	0.0	4.4	0.1
Restructuring expenses			20.8	19.9	0.0
Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period			0.0	0.0
Charges			25.3	179.3
Cash settlements			0.0	0.0
Adjustments to previous estimates			0.0	0.0
Non Cash Activity			(25.3)	(179.3)
Liability, end of period	0.0	0.0	0.0	0.0	0.0
Restructuring expenses	$ 69.1	$ 83.0	25.3	179.3	0.0
Cost of Sales [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			5.8	152.1	0.0
Cost of Sales [Member] \| Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Cost of Sales [Member] \| Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Cost of Sales [Member] \| Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			5.8	152.1	0.0
Research and Development Expense [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.1	16.3	0.0
Research and Development Expense [Member] \| Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Research and Development Expense [Member] \| Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Research and Development Expense [Member] \| Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.1	16.3	0.0
Selling, General and Administrative Expenses [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			19.4	10.9	0.0
Selling, General and Administrative Expenses [Member] \| Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Selling, General and Administrative Expenses [Member] \| Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Selling, General and Administrative Expenses [Member] \| Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			19.4	10.9	0.0
Restructuring Expense [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			25.5	104.6	3.0
Restructuring Expense [Member] \| Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			4.6	87.3	3.0
Restructuring Expense [Member] \| Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			20.9	17.3
Restructuring Expense [Member] \| Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Other Income [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			(0.1)	2.6	0.0
Other Income [Member] \| Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			0.0	0.0	0.0
Other Income [Member] \| Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			(0.1)	2.6	0.0
Other Income [Member] \| Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Restructuring expenses			$ 0.0	$ 0.0	$ 0.0

Segment Information - Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue from External Customer [Line Items]
Total revenues	$ 1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	$ 909.7	$ 859.1	$ 912.7	$ 869.6	$ 4,131.2	$ 3,551.1	$ 3,084.1
Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									16.40%	15.20%
Soliris
Revenue from External Customer [Line Items]
Total revenues									$ 3,563.0	$ 3,144.1	2,843.2
Soliris \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									13.30%	10.60%
Strensiq
Revenue from External Customer [Line Items]
Total revenues									$ 475.1	$ 339.8	209.4
Strensiq \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									39.80%	62.30%
Kanuma
Revenue from External Customer [Line Items]
Total revenues									$ 92.0	$ 65.6	29.1
Kanuma \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									40.20%	125.40%
Product [Member]
Revenue from External Customer [Line Items]
Total revenues									$ 4,130.1	$ 3,549.5	3,081.7
United States [Member] \| Soliris
Revenue from External Customer [Line Items]
Total revenues									$ 1,588.4	$ 1,235.0	1,058.5
United States [Member] \| Soliris \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									28.60%	16.70%
United States [Member] \| Strensiq
Revenue from External Customer [Line Items]
Total revenues									$ 374.3	$ 280.1	177.5
United States [Member] \| Strensiq \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									33.60%	57.80%
United States [Member] \| Kanuma
Revenue from External Customer [Line Items]
Total revenues									$ 51.3	$ 42.4	20.4
United States [Member] \| Kanuma \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									21.00%	107.80%
Europe [Member] \| Soliris
Revenue from External Customer [Line Items]
Total revenues									$ 1,036.7	$ 985.2	939.7
Europe [Member] \| Soliris \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									5.20%	4.80%
Europe [Member] \| Strensiq
Revenue from External Customer [Line Items]
Total revenues									$ 61.7	$ 35.6	15.3
Europe [Member] \| Strensiq \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									73.30%	132.70%
Europe [Member] \| Kanuma
Revenue from External Customer [Line Items]
Total revenues									$ 21.6	$ 14.6	6.3
Europe [Member] \| Kanuma \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									47.90%	131.70%
Asia Pacific [Member] \| Soliris
Revenue from External Customer [Line Items]
Total revenues									$ 382.0	$ 328.1	303.8
Asia Pacific [Member] \| Soliris \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									16.40%	8.00%
Asia Pacific [Member] \| Strensiq
Revenue from External Customer [Line Items]
Total revenues									$ 27.9	$ 18.6	13.0
Asia Pacific [Member] \| Strensiq \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									50.00%	43.10%
Asia Pacific [Member] \| Kanuma
Revenue from External Customer [Line Items]
Total revenues									$ 3.7	$ 2.7	1.3
Asia Pacific [Member] \| Kanuma \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									37.00%	107.70%
Non-US, Excluding Europe And Asia Pacific [Member] \| Soliris
Revenue from External Customer [Line Items]
Total revenues									$ 555.9	$ 595.8	541.2
Non-US, Excluding Europe And Asia Pacific [Member] \| Soliris \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									(6.70%)	10.10%
Non-US, Excluding Europe And Asia Pacific [Member] \| Strensiq
Revenue from External Customer [Line Items]
Total revenues									$ 11.2	$ 5.5	3.6
Non-US, Excluding Europe And Asia Pacific [Member] \| Strensiq \| Sales Revenue, Net [Member] \| Geographic Concentration Risk [Member]
Revenue from External Customer [Line Items]
Percentage change in product sales									103.60%	52.80%
Non-US, Excluding Europe And Asia Pacific [Member] \| Kanuma
Revenue from External Customer [Line Items]
Total revenues									$ 15.4	$ 5.9	$ 1.1

Quarterly Financial Information (unaudited) (Details) - USD ($)
$ / shares in Units, $ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Nov. 30, 2018

Quarterly Financial Information [Line Items]

Research and Development Asset Acquired Other than Through Business Combination, Written-off

$ 1,183.0

$ 0.0

Total revenues

$ 1,128.8

$ 1,026.5

$ 1,045.0

$ 930.9

$ 909.7

$ 859.1

$ 912.7

$ 869.6

4,131.2

3,551.1

3,084.1

Cost of sales

96.8

^[1]

90.6

^[1]

95.3

91.6

144.6

157.0

83.6

69.0

374.3

454.2

258.3

Effective income tax rate reconciliation, Tax Cuts and Jobs Act of 2017, amount

(56.5)

45.8

Total operating expenses

988.3

577.3

^[2]

1,349.8

^[3]

571.9

^[2]

656.5

^[4]

622.0

602.4

588.6

3,487.3

2,469.5

2,158.4

Operating income

43.7

358.6

(400.1)

267.4

108.6

80.1

226.7

212.0

269.6

627.4

667.4

Net income

$ (45.0)

$ 330.9

$ (457.4)

$ 249.1

$ 30.0

$ 78.0

$ 165.2

$ 170.1

$ 77.6

$ 443.3

$ 399.4

Earnings per common share

Basic (in dollars per share)

$ (0.20)

$ 1.48

$ (2.05)

$ 1.12

$ 0.13

$ 0.35

$ 0.74

$ 0.76

$ 0.35

$ 1.98

$ 1.78

Diluted (in dollars per share)

$ (0.20)

$ 1.47

$ (2.05)

$ 1.11

$ 0.13

$ 0.35

$ 0.73

$ 0.75

$ 0.35

$ 1.97

$ 1.76

Impairment of intangible assets

$ 0.0

$ 31.0

$ 85.0

Restructuring expenses

$ 79.4

$ 23.8

50.7

286.5

3.0

Facility Closing [Member]

Earnings per common share

Restructuring expenses

$ 69.1

$ 83.0

$ 25.3

$ 179.3

$ 0.0

Syntimmune, Inc [Member]

Quarterly Financial Information [Line Items]

Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, In-Process Research And Development

$ 379.3

[1]	Included within cost of sales for the third and fourth quarters 2017 are $83.0 and $69.1, respectively, of restructuring related expenses associated with the planned closure of the ARIMF facility.
[2]	Included within operating expenses for the first and third quarters 2017 are $23.8 and $79.4, respectively of restructuring and related expenses.
[3]	We recognized a tax (benefit) expense of $(56.5) and $45.8 in 2018 and 2017, respectively, as a result of the Tax Cuts and Jobs Act. In 2017, we recorded certain impacts of the Tax Act on a provisional basis. As of December 22, 2018, our accounting for the impact of the Tax Act was complete. See Note 12, “Income Taxes” for additional information.
[4]	(5) We recognized a tax (benefit) expense of $(56.5) and $45.8 in 2018 and 2017, respectively, as a result of the Tax Cuts and Jobs Act. In 2017, we recorded certain impacts of the Tax Act on a provisional basis. As of December 22, 2018, our accounting for the impact of the Tax Act was complete. See Note 12, “Income Taxes” for additional information.

Subsequent Events (Details) - Caelum Biosciences [Member] - Collaborative Arrangement [Member] - Subsequent Event [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2019	Mar. 31, 2019
Subsequent Event [Line Items]
Collaboration Agreement, Upfront Payment		$ 30.0
Collaboration Agreement, Potential Future Payments, Milestone Achievement	$ 30.0
Collaboration Agreement, Potential Future Payments, Acquisition Option Exercise	$ 500.0

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events In January 2019, we entered into a collaboration agreement with Caelum Biosciences (Caelum) to develop CAEL101 for light chain (AL) amyloidosis. Under the terms of the agreement, we acquired a minority equity interest in Caelum and an exclusive option to acquire the remaining equity in the company based on Phase 2 data, for pre-negotiated economics. We made an upfront payment of $30.0 and could be required to pay up to an additional $30.0 in contingent milestone-dependent option fees. The collaboration also provides for potential additional payments, in the event Alexion exercises the acquisition option, for up to $500.0, which includes an upfront option exercise payment and potential regulatory and commercial milestone payments.

Acquisitions Wilson Acquisition (Details) - In Process Research and Development [Member] $ in Millions	May 25, 2018 USD ($)	Apr. 30, 2018 kr / shares
Research and Development Assets Acquired Other than Through Business Combination [Line Items]
Asset Acquisition, Share Price \| kr / shares		kr 232
Asset Acquisition, Potential Payments For Development, Regulatory, Commercial Milestones And Royalties On Sales \| $	$ 19.0

Intangible Assets and Goodwill (Schedule of Changes in the Carrying Amount of Goodwill) (Details) $ in Millions	Dec. 31, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 5,037.4
Goodwill, ending balance	$ 5,037.4

Segment Information (Details) - USD ($) $ in Millions	12 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Effective income tax rate reconciliation, Tax Cuts and Jobs Act of 2017, amount	$ (56.5)	$ 45.8