Document and Entity Information Document - shares	9 Months Ended
Document and Entity Information Document - shares	Sep. 30, 2018	Oct. 22, 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-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		223,096,632

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,228.9	$ 584.4
Marketable securities	306.2	889.7
Trade accounts receivable, net	910.2	726.5
Inventories	432.7	460.4
Prepaid expenses and other current assets	370.4	292.9
Total current assets	3,248.4	2,953.9
Property, plant and equipment, net	1,443.4	1,325.4
Intangible assets, net	3,713.6	3,954.4
Goodwill	5,037.4	5,037.4
Other assets	400.8	312.2
Total assets	13,843.6	13,583.3
Liabilities and Stockholders' Equity
Accounts payable	52.2	70.8
Accrued expenses	539.8	639.4
Revolving credit facility	250.0	0.0
Current portion of long-term debt	61.2	167.4
Current portion of contingent consideration	95.8	0.0
Other current liabilities	28.4	74.9
Total current liabilities	1,027.4	952.5
Long-term debt, less current portion	2,533.3	2,720.7
Contingent consideration	179.4	168.9
Facility lease obligation	361.2	342.9
Deferred tax liabilities	442.8	365.0
Other liabilities	129.8	140.2
Total liabilities	4,673.9	4,690.2
Commitments and contingencies (Note 18)
Stockholders' Equity:
Common stock, $0.0001 par value; 290.0 shares authorized; 235.8 and 234.3 shares issued at September 30, 2018 and December 31, 2017, respectively	0.0	0.0
Additional paid-in capital	8,481.8	8,290.3
Treasury stock, at cost, 12.7 and 12.0 shares at September 30, 2018 and December 31, 2017, respectively	(1,689.9)	(1,604.9)
Accumulated other comprehensive income (loss)	6.9	(34.4)
Retained earnings	2,370.9	2,242.1
Total stockholders' equity	9,169.7	8,893.1
Total liabilities and stockholders' equity	$ 13,843.6	$ 13,583.3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Millions	Sep. 30, 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	235.8	234.3
Treasury Stock, Shares	12.7	12.0

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net product sales	$ 1,026.5	$ 858.8	$ 3,001.6	$ 2,640.1
Other revenue	0.0	0.3	0.8	1.3
Total revenues	1,026.5	859.1	3,002.4	2,641.4
Cost of sales	90.6	157.0	277.5	309.6
Operating expenses:
Research and development	174.8	195.7	524.8	613.4
Selling, general and administrative	258.7	270.6	793.1	798.0
Acquired in-process research and development	0.0	0.0	803.7	0.0
Amortization of purchased intangible assets	80.0	80.0	240.1	240.1
Change in fair value of contingent consideration	53.5	3.7	110.9	31.8
Restructuring expenses	10.3	72.0	26.4	98.7
Impairment of assets	0.0	0.0	0.0	31.0
Total operating expenses	577.3	622.0	2,499.0	1,813.0
Operating income	358.6	80.1	225.9	518.8
Other income and expense:
Investment income	5.9	4.5	119.4	12.9
Interest expense	(24.6)	(25.0)	(73.7)	(73.3)
Other income (expense)	2.2	(1.4)	3.5	0.1
Income before income taxes	342.1	58.2	275.1	458.5
Income tax expense (benefit)	11.2	(19.8)	152.5	45.2
Net income	$ 330.9	$ 78.0	$ 122.6	$ 413.3
Earnings per common share
Basic	$ 1.48	$ 0.35	$ 0.55	$ 1.84
Diluted	$ 1.47	$ 0.35	$ 0.55	$ 1.83
Shares used in computing earnings per common share
Basic	222.9	223.3	222.5	224.1
Diluted	224.6	225.0	224.2	225.5

Condensed Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income	$ 330.9	$ 78.0	$ 122.6	$ 413.3
Other comprehensive income (loss), net of tax:
Foreign currency translation	(1.7)	2.0	(6.0)	8.8
Unrealized gains (losses) on debt securities	0.1	0.2	(0.3)	1.1
Unrealized gains on pension obligation	0.0	0.0	0.7	0.3
Unrealized gains (losses) on hedging activities, net of tax of $2.9, $(14.0), $13.4 and $(59.3), respectively	11.4	(25.3)	46.9	(107.6)
Other comprehensive income (loss), net of tax	9.8	(23.1)	41.3	(97.4)
Comprehensive income	$ 340.7	$ 54.9	$ 163.9	$ 315.9

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Unrealized losses on hedging activities - tax effect	$ 2.9	$ (14.0)	$ 13.4	$ (59.3)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 122.6	$ 413.3
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	306.9	311.6
Impairment of assets	13.5	112.6
Change in fair value of contingent consideration	110.9	31.8
Payment for Contingent Consideration Liability, Operating Activities	0.0	(18.0)
Share-based compensation expense	150.9	172.3
Non-cash expense for acquired IPR&D	86.6	0.0
Deferred taxes	79.1	(57.3)
Unrealized foreign currency loss (gain)	8.6	(5.7)
Unrealized (gain) loss on forward contracts	(9.9)	8.1
Unrealized gain on equity investments	(100.5)	0.0
Other	(3.0)	4.4
Changes in operating assets and liabilities
Accounts receivable	(197.4)	(34.6)
Inventories	26.7	(69.1)
Prepaid expenses and other assets	(85.1)	(94.5)
Accounts payable, accrued expenses and other liabilities	(167.3)	82.6
Net cash provided by operating activities	342.6	857.5
Cash flows from investing activities:
Purchases of available-for-sale debt securities	(771.4)	(1,580.0)
Proceeds from maturity or sale of available-for-sale debt securities	1,356.4	932.3
Purchases of mutual funds related to nonqualified deferred compensation plan	(9.0)	(8.1)
Proceeds from sale of mutual funds related to nonqualified deferred compensation plan	9.3	5.8
Purchases of property, plant and equipment	(170.6)	(268.8)
Other	3.6	0.1
Net cash provided by (used in) investing activities	418.3	(918.7)
Cash flows from financing activities:
Debt issuance costs	(7.6)	0.0
Proceeds from revolving credit facility	250.0	0.0
Payments on term loan	(293.8)	(131.3)
Repurchases of common stock	(85.0)	(298.5)
Net proceeds from issuance of common stock under share-based compensation arrangements	41.4	76.0
Payments of contingent consideration	0.0	(7.0)
Other	(10.5)	(10.4)
Net cash used in financing activities	(105.5)	(371.2)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(10.6)	16.5
Net change in cash and cash equivalents and restricted cash	644.8	(415.9)
Cash and cash equivalents and restricted cash at beginning of period	586.3	966.0
Cash and cash equivalents and restricted cash at end of period	1,231.1	550.1
Supplemental cash flow disclosures from investing and financing activities:
Capitalization of construction costs related to facility lease obligations	44.3	109.6
Accrued expenses for purchases of property, plant and equipment	$ 10.2	$ 32.6

Business	9 Months Ended
Business	Sep. 30, 2018
Business [Abstract]
Business	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 first and only approved complement inhibitor to treat patients with paroxysmal nocturnal hemoglobinuria (PNH), 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	9 Months Ended
Basis of Presentation and Principles Of Consolidation	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements. These accounting principles were applied on a basis consistent with those of the consolidated financial statements contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2017. In our opinion, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of our financial statements for interim periods in accordance with accounting principles generally accepted in the United States. The condensed consolidated balance sheet data as of December 31, 2017 was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States. These interim financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2017 included in our Annual Report on Form 10-K for the year ended December 31, 2017. The results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the full year or any other future periods. In the current year, the Company’s rounding presentation of reported amounts have changed. The current year rounding presentation has been applied to all prior year amounts presented and, in certain circumstances, this change may adjust previously reported balances. 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. The accompanying unaudited condensed consolidated financial statements include the accounts of Alexion Pharmaceuticals, Inc. and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Our significant accounting policies are described in Note 1 of the Notes to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2017. Updates to our accounting policies, including impacts from the adoption of new accounting standards, are discussed within Note 8, Marketable Securities, Note 9, Derivative Instruments and Hedging Activities, Note 10, Other Investments, and Note 14, Revenue Recognition. Reclassifications Certain items in the prior period’s condensed consolidated financial statements have been reclassified to conform to the current presentation. New Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued a new standard requiring that the rights and obligations arising from leases be recognized on the balance sheet by recording a right-of-use (ROU) asset and corresponding lease liability. The new standard also requires qualitative and quantitative disclosures to understand the amount, timing, and uncertainty of cash flows arising from leases, as well as significant management estimates utilized. The standard is effective for interim and annual periods beginning after December 15, 2018 and requires a modified retrospective adoption. In July 2018, the FASB issued an update with an optional transition method when adopting the new leases standard. Under this new transition method, an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption rather than recast the comparative periods presented in the year of adoption. We plan to elect this optional method. We have substantially completed the process of collecting and continue to analyze the Company’s lease contracts and during the third quarter 2018, we started implementing our leasing software, including data upload and test procedures. Our lease accounting software implementation efforts are ongoing. While our assessment of the standard remains open, the standard may have a material impact on the Company’s Condensed Consolidated Balance Sheets due to the requirement to recognize lease ROU assets and corresponding liabilities related to leases on the Company’s Condensed Consolidated Balance Sheets. 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 still 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 will apply 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 have elected to measure our current 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 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 our equity investments without readily determinable fair values for observable price changes and impairment on a quarterly basis. Refer to Note 10, 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 condensed 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 condensed 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 condensed 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. We recorded a net increase to opening equity of $6.0 as of January 1, 2018 due to the cumulative impact of adopting this new standard. The impact to net product sales for the three and nine months ended September 30, 2018 was an increase of $6.7 and $20.5, respectively, as a result of adopting the new standard. The resulting impact to net income for the three and nine months ended September 30, 2018 was an increase of $4.8 and $16.6, respectively. The impact of adopting the new standard for the three and nine months ended September 30, 2018 is due primarily to the earlier recognition of revenue associated with customer arrangements for which control of the product has transferred to the customer prior to the shipment clearing customs in the respective country. Under prior revenue guidance, these amounts would have been deferred until risk of loss had transferred to the customer following customs clearance. The new standard also resulted in a decrease of $32.2 in deferred revenue and an increase of $22.7 in retained earnings as of September 30, 2018. The adoption of the new revenue standard did not have a material impact on any other balances within the condensed consolidated financial statements as of and for the three and nine months ended September 30, 2018.

Acquisitions

9 Months Ended

Sep. 30, 2018

Asset Acquisitions [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, 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. As of September 30, 2018, Alexion had acquired 99.8% of the outstanding shares of Wilson Therapeutics.

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, an early Phase III asset in development for the treatment of Wilson Disease. 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 nine months ended September 30, 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, is a monoclonal antibody that inhibits 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. Under the terms of the agreement, Alexion will acquire Syntimmune for an upfront 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, which is subject to the satisfaction of customary closing conditions (including approval from relevant regulatory agencies), is expected to close in the fourth quarter of 2018. We intend to finance the acquisition through cash on hand and account for the transaction as an asset acquisition.

Intangible Assets and Goodwill

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets and Goodwill

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



		September 30, 2018							December 31, 2017
	Estimated Life (years)	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Licensing rights	5-8	$	31.0	$	(29.1	)	$	1.9	$	31.0	$	(28.5	)	$	2.5
Patents	7	10.5		(10.5		)	—		10.5		(10.5		)	—
Purchased technology	6-16	4,710.5		(999.0		)	3,711.5		4,710.5		(758.9		)	3,951.6
Other intangibles	5	0.4		(0.2		)	0.2		0.4		(0.1		)	0.3
Total		$	4,752.4	$	(1,038.8	)	$	3,713.6	$	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 for the three months ended September 30, 2018 and 2017 was $80.2 and $80.0, respectively. Amortization expense for the nine months ended September 30, 2018 and 2017 was $240.8 and $240.1, respectively. Assuming no changes in the gross cost basis of intangible assets, the total estimated amortization expense for finite-lived intangible assets is $80.2 for the three months ending December 31, 2018, and approximately $320.0 for each of the years ending December 31, 2019 through December 31, 2023.

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.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Debt	9 Months Ended
Debt	Sep. 30, 2018
Debt [Abstract]
Debt	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). 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 three months ended September 30, 2018 and 2017 was $1.3 and $2.3, respectively, and amortization of deferred financing costs for the nine months ended September 30, 2018 and 2017 was $6.7 and $7.0 respectively. Remaining unamortized deferred financing costs as of September 30, 2018 and December 31, 2017 were $22.1 and $21.0, respectively. As of September 30, 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 September 30, 2018, we had open letters of credit of $1.7 that offset our availability in the revolving facility. The fair value of our long term debt, which is measured using Level 2 inputs of the fair value hierarchy, approximates book value.

Earnings Per Common Share

9 Months Ended

Sep. 30, 2018

Earnings Per Common Share [Abstract]

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 during the applicable period. 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 the three and nine months ended September 30, 2018 and 2017:



	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
Net income used for basic and diluted calculation	$	330.9	$	78.0	$	122.6	$	413.3
Shares used in computing earnings per common share—basic	222.9		223.3		222.5		224.1
Weighted-average effect of dilutive securities:
Stock awards	1.7		1.7		1.7		1.4
Shares used in computing earnings per common share—diluted	224.6		225.0		224.2		225.5
Earnings per common share:
Basic	$	1.48	$	0.35	$	0.55	$	1.84
Diluted	$	1.47	$	0.35	$	0.55	$	1.83

We exclude from EPS the weighted-average number of securities whose effect is anti-dilutive. Excluded from the calculation of EPS for the three months ended September 30, 2018 and 2017 were 2.5 and 3.9 shares of common stock because their effect was anti-dilutive. Similarly, we excluded 2.9 and 4.1 shares of common stock from the calculation of EPS for the nine months ended September 30, 2018 and 2017 because their effect was anti-dilutive.

Marketable Securities

9 Months Ended

Sep. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Marketable securities

Marketable Securities

We invest our excess cash balances in marketable securities of highly rated financial institutions and investment-grade debt instruments. We classify these marketable securities as available-for-sale and, accordingly, record such securities at fair value. Unrealized gains and losses that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity in the accompanying balance sheets.

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale debt securities by type of security as of September 30, 2018 and December 31, 2017 were as follows:



	September 30, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Commercial paper	$	196.1	$	—	$	—	$	196.1
Corporate bonds	136.0		—		—		136.0
Other government-related obligations:
U.S.	9.7		—		—		9.7
Foreign	2.6		—		—		2.6
Bank certificates of deposit	43.4		—		—		43.4
Total available-for-sale debt securities	$	387.8	$	—	$	—	$	387.8



	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:
U.S.	—		—		—			—
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 September 30, 2018 and December 31, 2017 was $92.8 and $436.2, respectively. Investments that have been in a continuous unrealized loss position for more than 12 months were zero as of September 30, 2018 and $12.0 as of December 31, 2017. As of September 30, 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 condensed consolidated balance sheet were as follows:



	September 30, 2018		December 31, 2017
Cash and cash equivalents	$	100.5	$	42.7
Marketable securities	287.3		870.9
	$	387.8	$	913.6

The fair values of available-for-sale debt securities at September 30, 2018, by contractual maturity, are summarized as follows:



	September 30, 2018
Due in one year or less	$	372.7
Due after one year through three years	15.1
	$	387.8

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 September 30, 2018 and December 31, 2017, the fair value of these investments was $18.9 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 three and nine months ended September 30, 2018 and 2017.

Derivative Instruments and Hedging Activities

9 Months Ended

Sep. 30, 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 September 30, 2018, we had open revenue related foreign exchange forward contracts with notional amounts totaling $994.4 that qualified for hedge accounting. As of September 30, 2018, we had open expense related foreign exchange forward contracts with notional amounts totaling $22.0 that qualified for hedge accounting.

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 table summarizes our interest rate swap contracts as of September 30, 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	250.0	December 2018	December 2022	2.79%
Floating to Fixed	300.0	January 2019	December 2019	2.08%
Floating to Fixed	900.0	December 2019	December 2022	2.79% - 2.83%

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 condensed consolidated statements of operations when the underlying hedged transaction affects earnings.

The amount of gains and losses recognized in the condensed consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017 from foreign exchange and interest rate swap contracts that qualified as cash flow hedges were as follows:



	Three months ended					Three months ended
	September 30, 2018					September 30, 2017
	Net Product Sales		Interest Expense			Net Product Sales			Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	1,026.5	$	(24.6	)	$	858.8		$	(25.0	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	3.3	$	—		$	(1.3	)	$	—
Interest Rate Swap Contracts	$	—	$	4.0		$	—		$	(0.3	)



	Nine months ended						Nine months ended
	September 30, 2018						September 30, 2017
	Net Product Sales			Interest Expense			Net Product Sales		Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	3,001.6		$	(73.7	)	$	2,640.1	$	(73.3	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	(11.5	)	$	—		$	30.7	$	—
Interest Rate Swap Contracts	$	—		$	8.5		$	—	$	(1.6	)

The impact on accumulated other comprehensive income (AOCI) from foreign exchange and interest rate swap contracts that qualified as cash flow hedges, for the three and nine months ended September 30, 2018 and 2017 were as follows:



	Three months ended					Nine months ended
	September 30,					September 30,
	2018		2017			2018			2017
Foreign Exchange Forward Contracts:
Gain (loss) recognized in AOCI, net of tax	$	9.8	$	(27.6	)	$	26.3		$	(89.3	)
Gain (loss) reclassified from AOCI to net product sales, net of tax	$	2.5	$	(0.8	)	$	(8.9	)	$	19.8
Interest Rate Contracts:
Gain (loss) recognized in AOCI, net of tax	$	7.2	$	1.2		$	18.4		$	0.4
Gain (loss) reclassified from AOCI to interest expense, net of tax	$	3.1	$	(0.2	)	$	6.7		$	(1.0	)

Assuming no change in foreign exchange rates from market rates at September 30, 2018, $7.5 of gains recognized in AOCI will be reclassified to revenue over the next 12 months. The amount of gains recognized in AOCI that will be reclassified to interest expense over the next 12 months is $22.6. Amounts recognized in AOCI for expense related foreign exchange forward contracts was not material at September 30, 2018.

We enter into foreign exchange forward contracts, with durations up to seven 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 September 30, 2018, the notional amount of foreign exchange contracts where hedge accounting is not applied was $794.2.

We recognized a gain (loss) of $6.8 and $(2.5), in other income and expense, for the three months ended September 30, 2018 and 2017, respectively, associated with the foreign exchange contracts not designated as hedging instruments. We recognized a gain (loss) of $17.1 and $(11.7), for the nine months ended September 30, 2018 and 2017, 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 as of September 30, 2018 and December 31, 2017:



	September 30, 2018
	Derivative Assets			Derivative Liabilities
	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	$	10.0
Foreign exchange forward contracts	Other assets	0.7		Other liabilities	5.8
Interest rate contracts	Prepaid expenses and other current assets	22.6		Other current liabilities	—
Interest rate contracts	Other assets	14.1		Other liabilities	—
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	10.1		Other current liabilities	3.9
Total fair value of derivative instruments		$	64.4		$	19.7



	December 31, 2017
	Derivative Assets			Derivative Liabilities
	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 condensed 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 condensed consolidated balance sheets of offsetting our foreign exchange forward contracts and interest rate contracts subject to such provisions:



	September 30, 2018
									Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Condensed Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Condensed Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	64.4		$	—	$	64.4		$	(16.7	)	$	—	$	47.7
Derivative liabilities	(19.7		)	—		(19.7		)	16.7			—		(3.0		)



	December 31, 2017
									Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Condensed Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Condensed 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		)

Other Investments	9 Months Ended
Other Investments	Sep. 30, 2018
Investments, All Other Investments [Abstract]
Other Investments	Other Investments We invest in companies with securities that are not publicly traded and where fair value is not readily available. We have historically recorded these investments at cost, less impairments. As of January 1, 2018, we will continue to record these investments at cost, less impairments; however, we will 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. During 2014, we purchased $37.5 of preferred stock of the non-public entity Moderna Therapeutics, Inc. (Moderna). During the first quarter 2018, Moderna announced the completion of a new round of financing. We considered this transaction and the rights of the preferred shares issued in the new round, compared to the rights of the preferred equity that we hold, and concluded that Moderna's new round of financing represents an observable price change in an orderly transaction for a similar investment. We further concluded, based on the respective rights of the stock and consideration of potential liquidity events, that the value of our preferred stock is equivalent to the value of the newly issued preferred stock. As a result, we recognized an unrealized gain of $100.8 in investment income during the first quarter 2018 to adjust our investment in Moderna to fair value as of the date of the observable price change, based on the per share price in Moderna's new round of financing. The carrying value of this investment was $138.3 and $37.5 as of September 30, 2018 and December 31, 2017, respectively. The carrying value of this investment was not impaired as of September 30, 2018.

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity In February 2017, our Board of Directors authorized the future acquisition of shares with an aggregate value of up to $1,000.0 under our existing 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 our discretion. Under the program, for the three months ended September 30, 2017, we repurchased 0.5 shares at a cost of $59.6. During the nine months ended September 30, 2018 and 2017, we repurchased 0.7 and 2.6 shares of our common stock at a cost of $85.0 and $298.5, respectively. The Company did not repurchase any shares during the three months ended September 30, 2018. As of October 24, 2018, there is a total of $451.5 remaining for repurchases under the repurchase program.

Other Comprehensive Income and Accumulated Other Comprehensive Income

9 Months Ended

Sep. 30, 2018

Accumulated Other Comprehensive Income [Abstract]

Other Comprehensive Income and Accumulated Other Comprehensive Income

The following tables summarize the changes in AOCI, by component, for the nine months ended September 30, 2018 and 2017:



	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, 2017	$	(4.8	)	$	0.2		$	(13.9	)	$	(15.9	)	$	(34.4	)
Other comprehensive income (loss) before reclassifications	1.2			0.2			44.7			(6.0		)	40.1
Amounts reclassified from other comprehensive income	(0.5		)	(0.5		)	2.2			—			1.2
Net other comprehensive income (loss)	0.7			(0.3		)	46.9			(6.0		)	41.3
Balances, September 30, 2018	$	(4.1	)	$	(0.1	)	$	33.0		$	(21.9	)	$	6.9



	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, 2016	$	(6.7	)	$	(0.4	)	$	91.9		$	(24.3	)	$	60.5
Other comprehensive income (loss) before reclassifications	0.2			0.4			(88.9		)	8.8			(79.5		)
Amounts reclassified from other comprehensive income	0.1			0.8			(18.8		)	—			(17.9		)
Net other comprehensive income (loss)	0.3			1.2			(107.7		)	8.8			(97.4		)
Balances, September 30, 2017	$	(6.4	)	$	0.8		$	(15.8	)	$	(15.5	)	$	(36.9	)

The table below provides details regarding significant reclassifications from AOCI during the three and nine months ended September 30, 2018 and 2017:



Details about Accumulated Other Comprehensive Income Components	Amount Reclassified From Accumulated Other Comprehensive Income during the three months ended September 30,						Amount Reclassified From Accumulated Other Comprehensive Income during the nine months ended September 30,						Affected Line Item in the Condensed Consolidated Statements of Operations
	2018			2017			2018			2017
Unrealized Gains (Losses) from Hedging Activity
Foreign exchange forward contracts	$	3.3		$	(1.3	)	$	(11.5	)	$	30.7		Net product sales
Interest rate swap contracts	4.0			(0.3		)	8.5			(1.6		)	Interest expense
	7.3			(1.6		)	(3.0		)	29.1
	(1.7		)	0.6			0.8			(10.3		)	Income tax expense (benefit)
	$	5.6		$	(1.0	)	$	(2.2	)	$	18.8

Fair Value Measurement

9 Months Ended

Sep. 30, 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 September 30, 2018 and December 31, 2017, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value.



		Fair Value Measurement at September 30, 2018
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Money market funds	$	503.2	$	—	$	503.2	$	—
Cash equivalents	Commercial paper	$	96.1	$	—	$	96.1	$	—
Cash equivalents	Bank certificates of deposit	$	1.6	$	—	$	1.6	$	—
Cash equivalents	Other government-related obligations	$	2.8	$	—	$	2.8	$	—
Marketable securities	Mutual funds	$	18.9	$	18.9	$	—	$	—
Marketable securities	Commercial paper	$	100.0	$	—	$	100.0	$	—
Marketable securities	Corporate bonds	$	136.0	$	—	$	136.0	$	—
Marketable securities	Other government-related obligations	$	9.5	$	—	$	9.5	$	—
Marketable securities	Bank certificates of deposit	$	41.8	$	—	$	41.8	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	27.0	$	—	$	27.0	$	—
Other assets	Foreign exchange forward contracts	$	0.7	$	—	$	0.7	$	—
Other current liabilities	Foreign exchange forward contracts	$	13.9	$	—	$	13.9	$	—
Other liabilities	Foreign exchange forward contracts	$	5.8	$	—	$	5.8	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	22.6	$	—	$	22.6	$	—
Other assets	Interest rate contracts	$	14.1	$	—	$	14.1	$	—
Current portion of contingent consideration	Acquisition-related contingent consideration	$	95.8	$	—	$	—	$	95.8
Contingent consideration	Acquisition-related contingent consideration	$	179.4	$	—	$	—	$	179.4



		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 nine months ended September 30, 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.

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 September 30, 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 of 4.2% 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 September 30, 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 September 30, 2018, the fair value of acquisition-related contingent consideration was $275.2. The following table represents a roll-forward of our acquisition-related contingent consideration:



	Nine months ended
	September 30, 2018
Balance at December 31, 2017	$	168.9
Amounts derecognized upon sale of asset	(4.6		)
Changes in fair value	110.9
Balance at September 30, 2018	$	275.2

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 September 30, 2018, and therefore has not been included in the transaction price. For the three and nine months ended September 30, 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 amendment 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 amendment and the probability of achieving the various sales milestones, our contingent consideration liability increased by $48.7 in the quarter ended September 30, 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

Revenue Recognition

9 Months Ended

Sep. 30, 2018

Revenue from Contract with Customer [Abstract]

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 entity 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 accounting policy for revenue recognition for periods prior to January 1, 2018 is described in Note 1 of the Notes to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2017.

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 fulfilment 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.

We evaluate the creditworthiness of customers on a regular basis. In certain European countries, sales by us are subject to payment terms that are statutorily determined. This is primarily the case in countries where the payer is government-owned or government-funded, which we consider to be creditworthy. 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 September 30, 2018 and December 31, 2017, allowances on receivables were not material.

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 know.

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.

Disaggregation of Revenue

The Company disaggregates revenue from contracts with customers into product and geographical regions as summarized below.



	Three months ended September 30,				Nine months ended September 30,
	2018		2017		2018		2017
Soliris
United States	$	404.5	$	307.6	$	1,136.3	$	913.5
Europe	262.1		248.4		766.3		738.3
Asia Pacific	98.2		81.8		277.3		241.4
Rest of World	123.2		117.6		406.4		459.0
Total	$	888.0	$	755.4	$	2,586.3	$	2,352.2

Strensiq
United States	$	86.6	$	70.6	$	275.7	$	203.9
Europe	16.6		9.6		47.0		23.3
Asia Pacific	7.2		5.2		19.2		13.3
Rest of World	2.8		1.6		7.1		3.7
Total	$	113.2	$	87.0	$	349.0	$	244.2

Kanuma
United States	$	13.7	$	11.4	$	38.6	$	31.2
Europe	4.7		3.6		16.4		8.7
Asia Pacific	0.8		0.7		2.9		1.8
Rest of World	6.1		0.7		8.4		2.0
Total	$	25.3	$	16.4	$	66.3	$	43.7

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 condensed consolidated statements of operations.

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



	September 30, 2018		December 31, 2017
Receivables, which are included in "Trade accounts receivable, net"	$	910.2	$	726.5
Contract liabilities, which are included in "Other current liabilities"	$	3.2	$	15.9

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 adjusted deferred revenue balance, as of January 1, 2018, was $5.5. We recognized this amount in revenue in the first quarter of 2018.

Income Taxes

9 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Income Taxes

The following table provides a comparative summary of our income tax expense and effective income tax rate for the three and nine months ended September 30, 2018 and 2017:



	Three months ended						Nine months ended
	September 30,						September 30,
	2018			2017			2018			2017
Income tax expense	$	11.2		$	(19.8	)	$	152.5		$	45.2
Effective tax rate	3.3		%	(34.0		)%	55.4		%	9.9		%

The income tax expense for the three and nine months ended September 30, 2018 and 2017 is attributable to the U.S. federal, state and foreign income taxes on our profitable operations. The increase in the effective tax rate for the three months ended September 30, 2018 as compared to the same period in the prior year is primarily attributable to the benefit of settling a routine Internal Revenue Service (IRS) examination in the prior year, offset by U.S. tax reform measurement period adjustments of $(53.1). The increase in the effective tax rate for the nine months ended September 30, 2018 as compared to the same period in the prior year is primarily attributable to the acquisition of Wilson Therapeutics, offset by U.S. tax reform measurement period adjustments and the benefit of settling a routine IRS examination in the prior year. Absent successful clinical results and regulatory approval, there is no alternative future use of the WTX101 asset acquired. Accordingly, the value of the asset of $803.7 was expensed in acquired in-process research and development for the nine months ended September 30, 2018. No tax benefit has been recognized for this expense, which resulted in an increase to the effective tax rate of 41.3%. Also included in the nine months ended September 30, 2018 is a U.S. tax reform measurement period adjustment to deferred taxes of $(14.7). This deferred tax benefit decreased the effective tax rate for the nine months ended September 30, 2018 by approximately 1.4%.

In December 2017, the 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.

We incorporated the impact of the Tax Act in our results or calculated provisional amounts for the tax effects of the Tax Act for the year ended December 31, 2017. As of September 30, 2018 we have concluded our accounting for the Tax Act 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 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.

As of September 30, 2018, our initial accounting for the Tax Act is incomplete as follows:

(a)

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. However, additional analysis is required to determine the effect of modifications to federal deductions and income inclusions on these systems. No measurement period adjustment to our initial accounting was recorded for the three and nine months ended September 30, 2018.

(b)

We calculated a reasonable estimate of the impact of the GILTI minimum tax on deferred taxes in the period ended December 31, 2017, which resulted in an increase to U.S. Federal tax expense and the deferred tax liability of $236.9. Our initial accounting for the minimum tax is incomplete because there is uncertainty regarding the calculation of the temporary differences that will be subject to the minimum tax. Additional analysis regarding the computation of these temporary differences and the expected timing and manner of their realization is required to complete our accounting. During the three months ended September 30, 2018 the Company recorded a measurement period adjustment of $(57.8) to income tax (benefit) as a result of analyzing the deductible allowance in deferred taxes.

(c)

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 is provisional. Additional analysis of the direct and indirect effects of the Tax Act is required to complete our accounting for this item. We recorded a measurement period adjustment of $4.7 in U.S. state income tax expense and deferred taxes to this provisional estimate for the three months ended September 30, 2018.

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.

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.

We continue to maintain a valuation allowance against certain deferred tax assets where realization is not cert

Defined Benefit Plans	9 Months Ended
Defined Benefit Plans	Sep. 30, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	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. The total net periodic benefit cost for the three and nine months ended September 30, 2018 and 2017 was not material.

Facility Lease Obligations	9 Months Ended
Facility Lease Obligations	Sep. 30, 2018
Leases [Abstract]
Leases	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. For each of the three and nine months ended September 30, 2018 and 2017, we recognized $3.5 and $10.6, respectively, of interest expense associated with this arrangement. As of September 30, 2018 and December 31, 2017, our total facility lease obligation was $134.0 and $134.6, respectively, recorded within other current liabilities and facility lease obligation on our condensed consolidated balance sheets. 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 construction period are required to be capitalized, as a non-cash transaction, offset by a corresponding facility lease obligation in our consolidated balance sheets. The completion of the facility, including obtaining regulatory approval, is expected in 2019. As of September 30, 2018 and December 31, 2017, we recorded a construction-in-process asset of $203.4 and $180.6, respectively, and an offsetting facility lease obligation of $156.1 and $159.1, respectively, within other current liabilities and facility lease obligation on our condensed 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. During the nine months ended September 30, 2018, we incurred $53.7 of payments to Lonza under this agreement, of which $7.0 was applied against the outstanding facility lease obligation and $46.7 was recognized as a prepayment of inventory. See Note 18 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 that was constructed in Boston, Massachusetts. The term of the lease commenced upon the landlord's substantial completion of our premises 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 will 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 condensed consolidated balance sheets. Construction of the facility was completed and the building was placed into service in the second quarter 2018. As of September 30, 2018 and December 31, 2017, our total facility lease obligation was $82.3 and $59.6, respectively, within facility lease obligation on our condensed consolidated balance sheets.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	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. 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 $1,174.7. 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 Alexion Rhode Island Manufacturing Facility (ARIMF) prior to its sale and a payment with respect to sales of Soliris manufactured at Lonza facilities. In addition to Lonza, we have non-cancellable commitments of approximately $63.6 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. 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 Securities and Exchange Commission (SEC) requesting information related to our grant-making activities and compliance with the Foreign Corrupt Practices Act (FCPA) in various countries. In addition, in October 2015, we received a request from the Department of Justice (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. For information concerning the risks associated with the investigation, see our Risk Factor - "If we fail to comply with laws or regulations, we may be subject to investigations and civil or criminal penalties and our business could be adversely affected." 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. 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 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 or payments to any 501(c)(3) organization that provides financial assistance to Medicare patients. We understand that the U.S. Attorney’s Office and the DOJ are coordinating its inquiry with the Office of Inspector General (OIG) of the U.S. Department of Health and Human Services. Other companies have disclosed similar inquiries. We are cooperating with this inquiry. We are engaged in discussions with the DOJ about a potential resolution of this matter. There can be no assurance that any current or future discussions with the government to resolve these matters will be successful or that any potential settlement terms or amount will be agreed to or finalized. We are unable 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. A hearing is scheduled to take place in November 2018. 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 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, Labor and Welfare 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. Given the early stages of this matter, 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.

Restructuring and Related Expenses

9 Months Ended

Sep. 30, 2018

Restructuring and Related Activities [Abstract]

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 the type of activity and the locations recognized within the consolidated statements of operations:



	Three months ended September 30,								Three months ended September 30,
	2018								2017
	Employee Separation Costs		Asset-Related Charges		Other		Total		Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	—	$	—	$	—	$	—	$	83.0	$	—	$	83.0
Research and Development	—		—		—		—		—		1.0		—		1.0
Selling, General and Administrative	—		7.9		—		7.9		—		6.4		—		6.4
Restructuring Expense	2.8		—		7.5		10.3		66.2		—		5.8		72.0
Other (Income) Expense	—		—		—		—		—		—		2.3		2.3
	$	2.8	$	7.9	$	7.5	$	18.2	$	66.2	$	90.4	$	8.1	$	164.7



	Nine months ended September 30,										Nine months ended September 30,
	2018										2017
	Employee Separation Costs		Asset-Related Charges		Other			Total			Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	5.8	$	—		$	5.8		—		83.0		—		$	83.0
Research and Development	—		0.1		—			0.1			—		1.0		—		$	1.0
Selling, General and Administrative	—		18.0		—			18.0			—		6.4		—		$	6.4
Restructuring Expense	6.9		—		19.5			26.4			86.3		—		12.4		$	98.7
Other (Income) Expense	—		—		(0.1		)	(0.1		)	—		—		2.3		$	2.3
	$	6.9	$	23.9	$	19.4		$	50.2		$	86.3	$	90.4	$	14.7	$	191.4

The following table presents a reconciliation of the restructuring reserve recorded within accrued expenses on the Company's condensed consolidated balance sheet for the three and nine months ended September 30, 2018:



	Three months ended September 30,												Nine months ended September 30,
	2018												2018
	Employee Separation Costs			Asset Charges			Other Costs			Total			Employee Separation Costs			Asset Charges			Other Costs			Total
Liability, beginning of period	$	17.5		$	—		$	2.6		$	20.1		$	53.8		$	—		$	4.4		$	58.2
Restructuring and Related Expenses	1.1			7.9			7.0			16.0			5.9			23.9			19.7			49.5
Cash settlements	(9.8		)	—			(6.3		)	(16.1		)	(50.2		)	—			(20.0		)	(70.2		)
Adjustments to previous estimates	1.7			—			0.5			2.2			1.0			—			(0.3		)	0.7
Asset impairments	—			(7.9		)	—			(7.9		)	—			(23.9		)	—			(23.9		)
Liability, end of period	$	10.5		$	—		$	3.8		$	14.3		$	10.5		$	—		$	3.8		$	14.3

The restructuring reserve of $14.3 and $58.2 is recorded in accrued expenses on the Company's condensed consolidated balance sheet as of September 30, 2018 and December 31, 2017, respectively. We currently estimate incurring up to an additional $125.0 in restructuring and related expenses primarily related to contract termination and related charges. We expect approximately half of the remaining restructuring and related expenses will result in cash outlays and we expect to pay all accrued amounts related to this restructuring during the next fiscal year.

Subsequent Event	9 Months Ended
Subsequent Event	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In October 2018, we entered into a collaboration agreement with Dicerna Pharmaceuticals, Inc. (Dicerna) that provides us with exclusive worldwide licenses and development and commercial rights for two pre-clinical RNA interference (RNAi) subcutaneously delivered molecules for complement-mediated diseases, as well as an exclusive option for other pre-clinical 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 will make an upfront payment of $37.0 for the exclusive licenses and the equity investment. 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.

Acquisitions (Tables)

9 Months Ended

Sep. 30, 2018

Asset Acquisitions [Abstract]

Summary of Total Consideration

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

Inventories (Tables)

9 Months Ended

Sep. 30, 2018

Inventory, Net [Abstract]

Schedule of Inventory, Current

The components of inventory are as follows:



	September 30,		December 31,
	2018		2017
Raw materials	$	10.8	$	4.7
Work-in-process	107.8		148.6
Finished goods	314.1		307.1
	$	432.7	$	460.4

Intangible Assets and Goodwill (Tables)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets and Goodwill

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



		September 30, 2018							December 31, 2017
	Estimated Life (years)	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Licensing rights	5-8	$	31.0	$	(29.1	)	$	1.9	$	31.0	$	(28.5	)	$	2.5
Patents	7	10.5		(10.5		)	—		10.5		(10.5		)	—
Purchased technology	6-16	4,710.5		(999.0		)	3,711.5		4,710.5		(758.9		)	3,951.6
Other intangibles	5	0.4		(0.2		)	0.2		0.4		(0.1		)	0.3
Total		$	4,752.4	$	(1,038.8	)	$	3,713.6	$	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

Earnings Per Common Share (Tables)

9 Months Ended

Sep. 30, 2018

Earnings Per Common Share [Abstract]

Schedule Of Basic And Diluted Earnings Per Share

The following table summarizes the calculation of basic and diluted EPS for the three and nine months ended September 30, 2018 and 2017:



	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
Net income used for basic and diluted calculation	$	330.9	$	78.0	$	122.6	$	413.3
Shares used in computing earnings per common share—basic	222.9		223.3		222.5		224.1
Weighted-average effect of dilutive securities:
Stock awards	1.7		1.7		1.7		1.4
Shares used in computing earnings per common share—diluted	224.6		225.0		224.2		225.5
Earnings per common share:
Basic	$	1.48	$	0.35	$	0.55	$	1.84
Diluted	$	1.47	$	0.35	$	0.55	$	1.83

Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2018

Investments, Debt and Equity Securities [Abstract]

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

September 30, 2018 and December 31, 2017 were as follows:



	September 30, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Commercial paper	$	196.1	$	—	$	—	$	196.1
Corporate bonds	136.0		—		—		136.0
Other government-related obligations:
U.S.	9.7		—		—		9.7
Foreign	2.6		—		—		2.6
Bank certificates of deposit	43.4		—		—		43.4
Total available-for-sale debt securities	$	387.8	$	—	$	—	$	387.8



	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:
U.S.	—		—		—			—
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]

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



	September 30, 2018		December 31, 2017
Cash and cash equivalents	$	100.5	$	42.7
Marketable securities	287.3		870.9
	$	387.8	$	913.6

Investments Classified by Contractual Maturity Date [Table Text Block]

The fair values of available-for-sale debt securities at September 30, 2018, by contractual maturity, are summarized as follows:



	September 30, 2018
Due in one year or less	$	372.7
Due after one year through three years	15.1
	$	387.8

Derivative Instruments and Hedging Activities (Tables)

9 Months Ended

Sep. 30, 2018

Derivative Instruments and Hedging Activities [Abstract]

Schedule of Interest Rate Contracts

The following table summarizes our interest rate swap contracts as of September 30, 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	250.0	December 2018	December 2022	2.79%
Floating to Fixed	300.0	January 2019	December 2019	2.08%
Floating to Fixed	900.0	December 2019	December 2022	2.79% - 2.83%

Schedule of Other Comprehensive Income and Earnings from Foreign Exchange Contracts



	Three months ended					Three months ended
	September 30, 2018					September 30, 2017
	Net Product Sales		Interest Expense			Net Product Sales			Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	1,026.5	$	(24.6	)	$	858.8		$	(25.0	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	3.3	$	—		$	(1.3	)	$	—
Interest Rate Swap Contracts	$	—	$	4.0		$	—		$	(0.3	)



	Nine months ended						Nine months ended
	September 30, 2018						September 30, 2017
	Net Product Sales			Interest Expense			Net Product Sales		Interest Expense
Financial Statement Line Item in which the Effects of Cash Flow Hedges are Recorded	$	3,001.6		$	(73.7	)	$	2,640.1	$	(73.3	)
Impact of cash flow hedging relationships:
Foreign Exchange Forward Contracts	$	(11.5	)	$	—		$	30.7	$	—
Interest Rate Swap Contracts	$	—		$	8.5		$	—	$	(1.6	)



	Three months ended					Nine months ended
	September 30,					September 30,
	2018		2017			2018			2017
Foreign Exchange Forward Contracts:
Gain (loss) recognized in AOCI, net of tax	$	9.8	$	(27.6	)	$	26.3		$	(89.3	)
Gain (loss) reclassified from AOCI to net product sales, net of tax	$	2.5	$	(0.8	)	$	(8.9	)	$	19.8
Interest Rate Contracts:
Gain (loss) recognized in AOCI, net of tax	$	7.2	$	1.2		$	18.4		$	0.4
Gain (loss) reclassified from AOCI to interest expense, net of tax	$	3.1	$	(0.2	)	$	6.7		$	(1.0	)

Schedule of Fair Value of Outstanding Derivatives

The following tables summarize the fair value of outstanding derivatives as of September 30, 2018 and December 31, 2017:



	September 30, 2018
	Derivative Assets			Derivative Liabilities
	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	$	10.0
Foreign exchange forward contracts	Other assets	0.7		Other liabilities	5.8
Interest rate contracts	Prepaid expenses and other current assets	22.6		Other current liabilities	—
Interest rate contracts	Other assets	14.1		Other liabilities	—
Derivatives not designated as hedging instruments:
Foreign exchange forward contracts	Prepaid expenses and other current assets	10.1		Other current liabilities	3.9
Total fair value of derivative instruments		$	64.4		$	19.7



	December 31, 2017
	Derivative Assets			Derivative Liabilities
	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

The following tables summarize the potential effect on our condensed consolidated balance sheets of offsetting our foreign exchange forward contracts and interest rate contracts subject to such provisions:



	September 30, 2018
									Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Condensed Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Condensed Consolidated Balance Sheet			Derivative Financial Instruments			Cash Collateral Received (Pledged)		Net Amount
Derivative assets	$	64.4		$	—	$	64.4		$	(16.7	)	$	—	$	47.7
Derivative liabilities	(19.7		)	—		(19.7		)	16.7			—		(3.0		)



	December 31, 2017
									Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet
Description	Gross Amounts of Recognized Assets/Liabilities			Gross Amounts Offset in the Condensed Consolidated Balance Sheet		Net Amounts of Assets/Liabilities Presented in the Condensed 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		)

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)

9 Months Ended

Sep. 30, 2018

Accumulated Other Comprehensive Income [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following tables summarize the changes in AOCI, by component, for the nine months ended September 30, 2018 and 2017:



	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, 2017	$	(4.8	)	$	0.2		$	(13.9	)	$	(15.9	)	$	(34.4	)
Other comprehensive income (loss) before reclassifications	1.2			0.2			44.7			(6.0		)	40.1
Amounts reclassified from other comprehensive income	(0.5		)	(0.5		)	2.2			—			1.2
Net other comprehensive income (loss)	0.7			(0.3		)	46.9			(6.0		)	41.3
Balances, September 30, 2018	$	(4.1	)	$	(0.1	)	$	33.0		$	(21.9	)	$	6.9



	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, 2016	$	(6.7	)	$	(0.4	)	$	91.9		$	(24.3	)	$	60.5
Other comprehensive income (loss) before reclassifications	0.2			0.4			(88.9		)	8.8			(79.5		)
Amounts reclassified from other comprehensive income	0.1			0.8			(18.8		)	—			(17.9		)
Net other comprehensive income (loss)	0.3			1.2			(107.7		)	8.8			(97.4		)
Balances, September 30, 2017	$	(6.4	)	$	0.8		$	(15.8	)	$	(15.5	)	$	(36.9	)

Reclassification out of Accumulated Other Comprehensive Income

The table below provides details regarding significant reclassifications from AOCI during the three and nine months ended September 30, 2018 and 2017:



Details about Accumulated Other Comprehensive Income Components	Amount Reclassified From Accumulated Other Comprehensive Income during the three months ended September 30,						Amount Reclassified From Accumulated Other Comprehensive Income during the nine months ended September 30,						Affected Line Item in the Condensed Consolidated Statements of Operations
	2018			2017			2018			2017
Unrealized Gains (Losses) from Hedging Activity
Foreign exchange forward contracts	$	3.3		$	(1.3	)	$	(11.5	)	$	30.7		Net product sales
Interest rate swap contracts	4.0			(0.3		)	8.5			(1.6		)	Interest expense
	7.3			(1.6		)	(3.0		)	29.1
	(1.7		)	0.6			0.8			(10.3		)	Income tax expense (benefit)
	$	5.6		$	(1.0	)	$	(2.2	)	$	18.8

Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Schedule Of Assets And Liabilites Measured At Fair Value



		Fair Value Measurement at September 30, 2018
Balance Sheet Classification	Type of Instrument	Total		Level 1		Level 2		Level 3
Cash equivalents	Money market funds	$	503.2	$	—	$	503.2	$	—
Cash equivalents	Commercial paper	$	96.1	$	—	$	96.1	$	—
Cash equivalents	Bank certificates of deposit	$	1.6	$	—	$	1.6	$	—
Cash equivalents	Other government-related obligations	$	2.8	$	—	$	2.8	$	—
Marketable securities	Mutual funds	$	18.9	$	18.9	$	—	$	—
Marketable securities	Commercial paper	$	100.0	$	—	$	100.0	$	—
Marketable securities	Corporate bonds	$	136.0	$	—	$	136.0	$	—
Marketable securities	Other government-related obligations	$	9.5	$	—	$	9.5	$	—
Marketable securities	Bank certificates of deposit	$	41.8	$	—	$	41.8	$	—
Prepaid expenses and other current assets	Foreign exchange forward contracts	$	27.0	$	—	$	27.0	$	—
Other assets	Foreign exchange forward contracts	$	0.7	$	—	$	0.7	$	—
Other current liabilities	Foreign exchange forward contracts	$	13.9	$	—	$	13.9	$	—
Other liabilities	Foreign exchange forward contracts	$	5.8	$	—	$	5.8	$	—
Prepaid expenses and other current assets	Interest rate contracts	$	22.6	$	—	$	22.6	$	—
Other assets	Interest rate contracts	$	14.1	$	—	$	14.1	$	—
Current portion of contingent consideration	Acquisition-related contingent consideration	$	95.8	$	—	$	—	$	95.8
Contingent consideration	Acquisition-related contingent consideration	$	179.4	$	—	$	—	$	179.4



		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

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



	Nine months ended
	September 30, 2018
Balance at December 31, 2017	$	168.9
Amounts derecognized upon sale of asset	(4.6		)
Changes in fair value	110.9
Balance at September 30, 2018	$	275.2

Revenue Recognition (Tables)

9 Months Ended

Sep. 30, 2018

Revenue from Contract with Customer [Abstract]

Disaggregation of revenue from contracts with customer

The Company disaggregates revenue from contracts with customers into product and geographical regions as summarized below.



	Three months ended September 30,				Nine months ended September 30,
	2018		2017		2018		2017
Soliris
United States	$	404.5	$	307.6	$	1,136.3	$	913.5
Europe	262.1		248.4		766.3		738.3
Asia Pacific	98.2		81.8		277.3		241.4
Rest of World	123.2		117.6		406.4		459.0
Total	$	888.0	$	755.4	$	2,586.3	$	2,352.2

Strensiq
United States	$	86.6	$	70.6	$	275.7	$	203.9
Europe	16.6		9.6		47.0		23.3
Asia Pacific	7.2		5.2		19.2		13.3
Rest of World	2.8		1.6		7.1		3.7
Total	$	113.2	$	87.0	$	349.0	$	244.2

Kanuma
United States	$	13.7	$	11.4	$	38.6	$	31.2
Europe	4.7		3.6		16.4		8.7
Asia Pacific	0.8		0.7		2.9		1.8
Rest of World	6.1		0.7		8.4		2.0
Total	$	25.3	$	16.4	$	66.3	$	43.7

Summary of receivables and contract liabilities from contracts

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



	September 30, 2018		December 31, 2017
Receivables, which are included in "Trade accounts receivable, net"	$	910.2	$	726.5
Contract liabilities, which are included in "Other current liabilities"	$	3.2	$	15.9

Restructuring and Related Expenses (Tables)

9 Months Ended

Sep. 30, 2018

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs



	Three months ended September 30,								Three months ended September 30,
	2018								2017
	Employee Separation Costs		Asset-Related Charges		Other		Total		Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	—	$	—	$	—	$	—	$	83.0	$	—	$	83.0
Research and Development	—		—		—		—		—		1.0		—		1.0
Selling, General and Administrative	—		7.9		—		7.9		—		6.4		—		6.4
Restructuring Expense	2.8		—		7.5		10.3		66.2		—		5.8		72.0
Other (Income) Expense	—		—		—		—		—		—		2.3		2.3
	$	2.8	$	7.9	$	7.5	$	18.2	$	66.2	$	90.4	$	8.1	$	164.7



	Nine months ended September 30,										Nine months ended September 30,
	2018										2017
	Employee Separation Costs		Asset-Related Charges		Other			Total			Employee Separation Costs		Asset-Related Charges		Other		Total
Cost of Sales	$	—	$	5.8	$	—		$	5.8		—		83.0		—		$	83.0
Research and Development	—		0.1		—			0.1			—		1.0		—		$	1.0
Selling, General and Administrative	—		18.0		—			18.0			—		6.4		—		$	6.4
Restructuring Expense	6.9		—		19.5			26.4			86.3		—		12.4		$	98.7
Other (Income) Expense	—		—		(0.1		)	(0.1		)	—		—		2.3		$	2.3
	$	6.9	$	23.9	$	19.4		$	50.2		$	86.3	$	90.4	$	14.7	$	191.4



	Three months ended September 30,												Nine months ended September 30,
	2018												2018
	Employee Separation Costs			Asset Charges			Other Costs			Total			Employee Separation Costs			Asset Charges			Other Costs			Total
Liability, beginning of period	$	17.5		$	—		$	2.6		$	20.1		$	53.8		$	—		$	4.4		$	58.2
Restructuring and Related Expenses	1.1			7.9			7.0			16.0			5.9			23.9			19.7			49.5
Cash settlements	(9.8		)	—			(6.3		)	(16.1		)	(50.2		)	—			(20.0		)	(70.2		)
Adjustments to previous estimates	1.7			—			0.5			2.2			1.0			—			(0.3		)	0.7
Asset impairments	—			(7.9		)	—			(7.9		)	—			(23.9		)	—			(23.9		)
Liability, end of period	$	10.5		$	—		$	3.8		$	14.3		$	10.5		$	—		$	3.8		$	14.3

Basis of Presentation and Principles Of Consolidation Basis of Presentation and Principles Of Consolidation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 2,370.9		$ 2,370.9			$ 2,242.1
Revenue, Net	1,026.5	$ 859.1	3,002.4	$ 2,641.4
Net income	330.9	$ 78.0	122.6	$ 413.3
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	22.7		22.7		$ 6.0
Revenue, Net	6.7		20.5
Net income	4.8		16.6
Decrease in deferred revenue	$ 32.2		$ 32.2		$ 10.4

Acquisitions (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
Acquisitions (Narrative) (Details) $ in Millions	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	May 25, 2018 USD ($)	Apr. 30, 2018 kr / shares
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Acquired in-process research and development	$ 0.0	$ 0.0	$ 803.7	$ 0.0
Scenario, Forecast [Member] \| Syntimmune, Inc [Member]
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Payments to acquire businesses					$ 400.0
Additional payments to acquire businesses					800.0
Total acquisition value					$ 1,200.0
In Process Research and Development
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Cash offer price per share (in sec per share) \| kr / shares							kr 232
Potential development, regulatory and commercial milestones and royalties payment						$ 19.0
Wilson Therapeutics [Member] \| In Process Research and Development
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Percentage of shares acquired	99.80%		99.80%

Acquisitions (Summary of Total Consideration) (Details) - In Process Research and Development $ in Millions	May 25, 2018 USD ($)
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

Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Inventory [Line Items]
Raw materials	$ 10.8	$ 4.7
Work-in-process	107.8	148.6
Finished goods	314.1	307.1
Inventory, Net	$ 432.7	$ 460.4

Intangible Assets and Goodwill (Schedule of Intangible Assets and Goodwill) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Cost	$ 4,752.4	$ 4,752.4
Goodwill, Gross	5,040.3	5,040.3
Intangible Assets, Accumulated Amortization	(1,038.8)	(798.0)
Goodwill, Accumulated Amortization	(2.9)	(2.9)
Intangible assets	3,713.6	3,954.4
Goodwill	5,037.4	5,037.4
Licensing Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	31.0	31.0
Finite-Lived Intangible Assets, Accumulated Amortization	(29.1)	(28.5)
Licenses, patents and purchased technology	$ 1.9	2.5
Licensing Agreements [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	6 years
Licensing Agreements [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	8 years
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
Finite-Lived Intangible Assets, Gross	$ 10.5	10.5
Finite-Lived Intangible Assets, Accumulated Amortization	(10.5)	(10.5)
Licenses, patents and purchased technology	0.0	0.0
Purchased Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	4,710.5	4,710.5
Finite-Lived Intangible Assets, Accumulated Amortization	(999.0)	(758.9)
Licenses, patents and purchased technology	$ 3,711.5	3,951.6
Purchased Technology [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	6 years
Purchased Technology [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	16 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Finite-Lived Intangible Assets, Gross	$ 0.4	0.4
Finite-Lived Intangible Assets, Accumulated Amortization	(0.2)	(0.1)
Licenses, patents and purchased technology	$ 0.2	$ 0.3

Intangible Assets and Goodwill (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of Intangible Assets	$ 80.2	$ 80.0		$ 240.8	$ 240.1
2018 (remainder)	80.2			80.2
2019	320.0			320.0
2020	320.0			320.0
2021	320.0			320.0
2022	320.0			320.0
2023	320.0			320.0
Impairment of assets	$ 0.0	$ 0.0	$ 31.0	$ 0.0	$ 31.0

Debt (Details) $ in Millions		3 Months Ended		9 Months Ended
Debt (Details) $ in Millions	Jun. 07, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Payments of financing costs				$ 53.1
Amortization of deferred financing costs		$ 1.3	$ 2.3	6.7	$ 7.0
Remaining unamortized deferred financing costs		22.1		22.1		$ 21.0
Proceeds from lines of credit				250.0	$ 0.0
Credit Agreement [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Letters of credit, amount outstanding		1.7		1.7
Credit Agreement [Member] \| Line of Credit [Member] \| Minimum [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.25%
Credit Agreement [Member] \| Line of Credit [Member] \| Minimum [Member] \| Eurodollar [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.25%
Credit Agreement [Member] \| Line of Credit [Member] \| Maximum [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.00%
Credit Agreement [Member] \| Line of Credit [Member] \| Maximum [Member] \| Eurodollar [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000.0
Ratio of total net debt to EBITDA	3.50
EBITDA to cash interest expense ratio	3.50
Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Outstanding debt		250.0		250.0
Proceeds from lines of credit				250.0
Credit Agreement [Member] \| Senior Secured Term Loan [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 2,612.5
Debt Instrument, quarterly payment as a percent of total borrowings	5.00%
Outstanding debt		$ 2,612.5		$ 2,612.5

Earnings Per Common Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Common Share [Abstract]
Net income used for basic and diluted calculation	$ 330.9	$ 78.0	$ 122.6	$ 413.3
Shares used in computing earnings per common share—basic	222.9	223.3	222.5	224.1
Stock awards	1.7	1.7	1.7	1.4
Shares used in computing earnings per common share-diluted	224.6	225.0	224.2	225.5
Earnings (loss) Per Share, Basic	$ 1.48	$ 0.35	$ 0.55	$ 1.84
Earnings (loss) Per Share, Diluted	$ 1.47	$ 0.35	$ 0.55	$ 1.83

Earnings Per Common Share (Narrative) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2.5	3.9	2.9	4.1

Marketable Securities (Summary of Securities Held) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 387.8	$ 913.6
Available-for-sale Securities, Debt Securities	387.8
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	387.8	913.3
Gross Unrealized Holding Gains	0.0	0.7
Gross Unrealized Holding Losses	0.0	(0.4)
Fair Value	387.8	913.6
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	196.1	16.0
Gross Unrealized Holding Gains	0.0	0.0
Gross Unrealized Holding Losses	0.0	0.0
Fair Value	196.1	16.0
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	136.0	432.2
Gross Unrealized Holding Gains	0.0	0.5
Gross Unrealized Holding Losses	0.0	(0.2)
Fair Value	136.0	432.5
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9.7	0.0
Gross Unrealized Holding Gains	0.0	0.0
Gross Unrealized Holding Losses	0.0	0.0
Fair Value	9.7	0.0
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2.6	426.3
Gross Unrealized Holding Gains	0.0	0.2
Gross Unrealized Holding Losses	0.0	(0.2)
Fair Value	2.6	426.3
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	43.4	11.8
Gross Unrealized Holding Gains	0.0	0.0
Gross Unrealized Holding Losses	0.0	0.0
Fair Value	$ 43.4	11.8
Repurchase Agreements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis		27.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		0.0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		0.0
Available-for-sale Securities, Debt Securities		$ 27.0

Marketable Securities (Available-for-sale Investments by Classification in Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 387.8	$ 913.6
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	100.5	42.7
Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 287.3	$ 870.9

Marketable Securities (Available-for-sale Debt Securities by Contractual Maturity) (Details) $ in Millions	Sep. 30, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 372.7
Due after one year through three years	15.1
Estimated Fair Value	$ 387.8

Marketable Securities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 92.8	$ 436.2
Trading securities. fair value	18.9	18.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0.0	$ 12.0

Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign Exchange Forward Contracts Term			60 months
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign Exchange Forward Contracts Term			7 months
Gain (loss) reclassified from AOCI to net product sales, net of tax	$ 6.8	$ (2.5)	$ 17.1	$ (11.7)
Foreign Exchange Forward [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative instruments	994.4		994.4
Foreign Exchange Forward [Member] \| Designated as Hedging Instrument [Member] \| Revenue
Derivative [Line Items]
Estimated gains (losses) to be reclassified from other comprehenisve income in next 12 months			7.5
Foreign Exchange Forward [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative instruments	794.2		794.2
Foreign Exchange Forward, Open Expense [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative instruments	22.0		22.0
Interest Rate Swap One [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative instruments	$ 2,031.3		$ 2,031.3
Interest Rate Swap One [Member] \| Designated as Hedging Instrument [Member] \| Minimum [Member]
Derivative [Line Items]
Fixed interest borrowing spreads	0.98%		0.98%
Interest Rate Swap One [Member] \| Designated as Hedging Instrument [Member] \| Maximum [Member]
Derivative [Line Items]
Fixed interest borrowing spreads	1.62%		1.62%
Interest Rate Swap Two [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative instruments	$ 250.0		$ 250.0
Fixed interest borrowing spreads	2.79%		2.79%
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivative [Line Items]
Estimated gains (losses) to be reclassified from other comprehenisve income in next 12 months			$ 22.6

Derivative Instruments and Hedging Activities (Schedule of Interest Rate Contracts) (Details) - Designated as Hedging Instrument [Member] $ in Millions	Sep. 30, 2018 USD ($)
Interest Rate Swap One [Member]
Derivative [Line Items]
Derivative, notional amount	$ 2,031.3
Interest Rate Swap Three [Member]
Derivative [Line Items]
Derivative, notional amount	$ 300.0
Derivative, fixed interest rate	2.08%
Interest Rate Swap Four [Member]
Derivative [Line Items]
Derivative, notional amount	$ 900.0
Minimum [Member] \| Interest Rate Swap One [Member]
Derivative [Line Items]
Derivative, fixed interest rate	0.98%
Minimum [Member] \| Interest Rate Swap Four [Member]
Derivative [Line Items]
Derivative, fixed interest rate	2.79%
Maximum [Member] \| Interest Rate Swap One [Member]
Derivative [Line Items]
Derivative, fixed interest rate	1.62%
Maximum [Member] \| Interest Rate Swap Four [Member]
Derivative [Line Items]
Derivative, fixed interest rate	2.83%

Derivative Instruments and Hedging Activities (Schedule Of Other Comprehensive Income And Earnings From Foreign Exchange Contracts) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Net product sales	$ 1,026.5	$ 858.8	$ 3,001.6	$ 2,640.1
Interest expense	(24.6)	(25.0)	(73.7)	(73.3)
Foreign Exchange Forward [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in AOCI, net of tax	9.8	(27.6)	26.3	(89.3)
Foreign Exchange Forward [Member] \| Sales \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from AOCI to net product sales, net of tax	2.5	(0.8)	(8.9)	19.8
Interest Rate Contract [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in AOCI, net of tax	7.2	1.2	18.4	0.4
Interest Rate Contract [Member] \| Interest Expense \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from AOCI to net product sales, net of tax	3.1	(0.2)	6.7	(1.0)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] \| Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net product sales	3.3	(1.3)	(11.5)	30.7
Interest expense	0.0	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 Instruments, Gain (Loss) [Line Items]
Net product sales	0.0	0.0	0.0	0.0
Interest expense	$ 4.0	$ (0.3)	$ 8.5	$ (1.6)

Derivative Instruments and Hedging Activities (Schedule Of Fair Value Of Outstanding Derivatives) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Interest Rate Contract [Member] \| Other Current Liabilities \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	$ 0.0	$ 0.0
Interest Rate Contract [Member] \| Other Assets \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value		12.5
Interest Rate Contract [Member] \| Other Liabilities \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	0.0	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
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	64.4	48.8
Liability Derivatives, Fair Value	19.7	74.5
Foreign Exchange Forward [Member] \| Other Current Liabilities \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	10.0	34.8
Foreign Exchange Forward [Member] \| Other Assets \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	0.7	4.1
Foreign Exchange Forward [Member] \| Other Liabilities \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	5.8	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] \| Other Current Liabilities \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	3.9	13.7
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	10.1	10.0
Interest Rate Contract [Member] \| Other Assets
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	14.1	12.5
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	22.6	9.3
Interest Rate Contract [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other Assets
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	14.1	12.5
Interest Rate Contract [Member] \| Fair Value, Inputs, Level 2 [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	$ 22.6	$ 9.3

Derivative Instruments and Hedging Activities (Offsetting Assets and Liabilities) (Details) - Foreign Exchange Forward [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Asset, Fair Value, Amount Offset Against Collateral [Abstract]
Gross Amounts of Recognized Assets	$ 64.4	$ 48.8
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0.0	0.0
Amounts of Assets Presented in the Condensed Consolidated Balance Sheet	64.4	48.8
Derivative Financial Instruments	(16.7)	(26.3)
Cash Collateral Received	0.0	0.0
Net Amount	47.7	22.5
Derivative Liability, Fair Value, Amount Offset Against Collateral [Abstract]
Gross Amounts of Recognized Liabilities	(19.7)	(74.5)
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0.0	0.0
Amounts of Liabilities Presented in the Condensed Consolidated Balance Sheet	(19.7)	(74.5)
Derivative Financial Instruments	16.7	26.3
Cash Collateral Pledged	0.0	0.0
Net Amount	$ (3.0)	$ (48.2)

Other Investments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
Other Investments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2014	Dec. 31, 2017
Investment [Line Items]
Unrealized Gain (Loss) on Investments		$ 100.5	$ 0.0
Moderna LLC [Member]
Investment [Line Items]
Payments to Acquire Other Investments				$ 37.5
Unrealized Gain (Loss) on Investments	$ 100.8
Equity Method Investments		$ 138.3			$ 37.5

Stockholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Oct. 24, 2018	Feb. 28, 2017
Class of Stock [Line Items]
Treasury Stock, Shares, Acquired	0.5	0.7	2.6
Treasury Stock, Value, Acquired, Cost Method	$ 59.6	$ 85.0	$ 298.5
Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 1,000.0
Subsequent Event \| Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 451.5

Other Comprehensive Income and Accumulated Other Comprehensive Income (Changes in AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			$ (34.4)	$ 60.5
Other comprehensive income (loss) before reclassifications			40.1	(79.5)
Amounts reclassified from other comprehensive income			1.2	(17.9)
Other comprehensive income (loss), net of tax	$ 9.8	$ (23.1)	41.3	(97.4)
Ending Balance	6.9	(36.9)	6.9	(36.9)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(4.8)	(6.7)
Other comprehensive income (loss) before reclassifications			1.2	0.2
Amounts reclassified from other comprehensive income			(0.5)	0.1
Other comprehensive income (loss), net of tax			0.7	0.3
Ending Balance	(4.1)	(6.4)	(4.1)	(6.4)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			0.2	(0.4)
Other comprehensive income (loss) before reclassifications			0.2	0.4
Amounts reclassified from other comprehensive income			(0.5)	0.8
Other comprehensive income (loss), net of tax			(0.3)	1.2
Ending Balance	(0.1)	0.8	(0.1)	0.8
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(13.9)	91.9
Other comprehensive income (loss) before reclassifications			44.7	(88.9)
Amounts reclassified from other comprehensive income			2.2	(18.8)
Other comprehensive income (loss), net of tax			46.9	(107.7)
Ending Balance	33.0	(15.8)	33.0	(15.8)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(15.9)	(24.3)
Other comprehensive income (loss) before reclassifications			(6.0)	8.8
Amounts reclassified from other comprehensive income			0.0	0.0
Other comprehensive income (loss), net of tax			(6.0)	8.8
Ending Balance	$ (21.9)	$ (15.5)	$ (21.9)	$ (15.5)

Other Comprehensive Income and Accumulated Other Comprehensive Income (Significant Reclassifications from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net product sales	$ 1,026.5	$ 858.8	$ 3,001.6	$ 2,640.1
Other income (expense)			(8.6)	5.7
Investment income	5.9	4.5	119.4	12.9
Income before income taxes	342.1	58.2	275.1	458.5
Income tax provision	(11.2)	19.8	(152.5)	(45.2)
Net income	330.9	78.0	122.6	413.3
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net product sales	3.3	(1.3)	(11.5)	30.7
Other income (expense)	4.0	(0.3)	8.5	(1.6)
Income before income taxes	7.3	(1.6)	(3.0)	29.1
Income tax provision	(1.7)	0.6	0.8	(10.3)
Net income	$ 5.6	$ (1.0)	$ (2.2)	$ 18.8

Fair Value Measurement (Schedule Of Acquisition-Related Contingent Consideration) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	$ 0.0		$ 0.0
Business Combination, Contingent Consideration, Arrangements, Range of Outcomes, Value, High	702.0		702.0
Acquisition-Related Contingent Consideration [Roll Forward]
Amounts derecognized upon sale of asset	(53.5)	$ (3.7)	(110.9)	$ (31.8)
Acquisition Related Contingent Consideration [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Business Combination, Contingent Consideration, Liability	275.2		275.2
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)
Change in fair value			110.9
Balance at end of period	$ 275.2		$ 275.2
Acquisition Related Contingent Consideration [Member] \| Minimum [Member] \| Level 3 [Member]
Fair Value Inputs, Liabilities, Quantitative Information [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 Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Weighted Average Cost of Capital			21.00%

Fair Value Measurement (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in contingent consideration liability	$ 53.5	$ 3.7	$ 110.9	$ 31.8
ALXN1101 Program [Member] \| Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in contingent consideration liability	4.6
Enobia Pharma Corp. [Member] \| Discontinued Operations, Disposed of by Means Other than Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in contingent consideration liability	$ 48.7

Revenue Recognition (Disaggregation of Revenue by Product and Geographical Region) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Soliris
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	$ 888.0	$ 755.4	$ 2,586.3	$ 2,352.2
Strensiq Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	113.2	87.0	349.0	244.2
Kanuma Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	25.3	16.4	66.3	43.7
United States \| Soliris
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	404.5	307.6	1,136.3	913.5
United States \| Strensiq Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	86.6	70.6	275.7	203.9
United States \| Kanuma Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	13.7	11.4	38.6	31.2
Europe \| Soliris
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	262.1	248.4	766.3	738.3
Europe \| Strensiq Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	16.6	9.6	47.0	23.3
Europe \| Kanuma Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	4.7	3.6	16.4	8.7
Asia Pacific \| Soliris
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	98.2	81.8	277.3	241.4
Asia Pacific \| Strensiq Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	7.2	5.2	19.2	13.3
Asia Pacific \| Kanuma Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	0.8	0.7	2.9	1.8
Rest of World \| Soliris
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	123.2	117.6	406.4	459.0
Rest of World \| Strensiq Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	2.8	1.6	7.1	3.7
Rest of World \| Kanuma Product Line
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Net Product Sales	$ 6.1	$ 0.7	$ 8.4	$ 2.0

Revenue Recognition (Summary of Receivables and Contract Liabilities from Contracts) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Receivables, which are included in Trade accounts receivable, net	$ 910.2	$ 726.5
Contract liabilities, which are included in Other current liabilities	$ 3.2	$ 15.9

Revenue Recognition (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 2,370.9		$ 2,242.1
Deferred revenue from contracts		$ 5.5
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Decrease in deferred revenue	32.2	10.4
Retained earnings	$ 22.7	$ 6.0

Income Taxes (Schedule of Income Tax Provision and Effective Tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 11.2	$ (19.8)	$ 152.5	$ 45.2
Effective tax rate	3.30%	(34.00%)	55.40%	9.90%

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2018	May 25, 2018
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit, Foreign		$ 533.4
Tax Cuts And Jobs Act Of 2017, Transition Tax For Accumulated Foreign Earnings, Provisional Liability, Tax Credits		28.0
Tax Cut And Jobs Act 2017, Incomplete Accounting, Global Intangible Low-Taxed Income Minimum Tax, Provisional Income Tax Expense (Benefit), Deferred Tax Expense	$ (57.8)	236.9
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit, State And Local		$ 4.7
Decreased in effective tax rate, asset acquisition		41.30%
Effective Income Tax Rate Reconciliation,Tax Cuts And Jobs Act Of 2017, Amount	$ (53.1)	$ (14.7)
Effective Income Tax Rate Reconciliation,Tax Cuts And Jobs Act Of 2017, Percent		0.014
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)		$ 177.9
In Process Research and Development
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, Finite-Lived Intangibles			$ 803.7
State and Local Jurisdiction [Member]
Schedule Of Asset Acquisition, By Acquisition [Line Items]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit)		(2.9)
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense, Increase (Decrease) In Taxes Payable		2.2
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit), Deferred Tax Expense		$ 0.7

Facility Lease Obligations (Details) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
Facility Lease Obligations (Details) $ in Millions	Nov. 30, 2012	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 ft²
Operating Leased Assets [Line Items]
Facility Lease Obligation, Noncurrent		$ 361.2	$ 361.2	$ 342.9
CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Interest Expense, Lessee, Assets under Capital Lease		3.5	10.6
Facility Lease Obligation, Noncurrent		134.0	134.0	134.6
MASSACHUSETTS
Operating Leased Assets [Line Items]
Facility Lease Obligation, Noncurrent		82.3	82.3	59.6
Area of Real Estate Property \| ft²					150,000
Minimum [Member] \| CONNECTICUT \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Lessee, Operating Lease, Renewal Term	10 years
Minimum [Member] \| MASSACHUSETTS
Operating Leased Assets [Line Items]
Lessee, Operating Lease, Renewal Term	10 years
Lonza Group AG
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases			53.7
Lonza Group AG \| Construction in Progress [Member]
Operating Leased Assets [Line Items]
Construction-in-process asset		203.4	203.4	180.6
Lonza Group AG \| Facility Lease Obligation [Member]
Operating Leased Assets [Line Items]
Facility Lease Obligation, Noncurrent		$ 156.1	$ 156.1	$ 159.1
Facility Lease Obligation, Payment Period			10 years
Inventories [Member] \| Lonza Group AG
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases			$ 46.7
Facility Lease Obligation [Member] \| Lonza Group AG
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases			$ 7.0

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Commitments [Line Items]
Distribution fees related to importation expenses	$ 577.3	$ 622.0	$ 2,499.0	$ 1,813.0
Lonza Group AG
Other Commitments [Line Items]
Remaining total commitments	1,174.7		1,174.7
Other Third Party Manufacturers
Other Commitments [Line Items]
Remaining total commitments	$ 63.6		$ 63.6

Restructuring and Related Expenses (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jun. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Number of Positions Eliminated, Period Percent					20.00%
Restructuring expenses	$ 18.2	$ 164.7	$ 50.2	$ 191.4
Restructuring Reserve	14.3		14.3		$ 58.2	$ 20.1
Employee Separation Costs
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	2.8	$ 66.2	6.9	$ 86.3
Restructuring Reserve	$ 10.5		$ 10.5		$ 53.8	$ 17.5

Restructuring and Related Expenses (Schedule of Restructuring and related Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 18.2	$ 164.7	$ 50.2	$ 191.4
Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	83.0	5.8	83.0
Research and Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	1.0	0.1	1.0
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	7.9	6.4	18.0	6.4
Restructuring Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	10.3	72.0	26.4	98.7
Other Income [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	2.3	(0.1)	2.3
Employee Separation Costs
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	2.8	66.2	6.9	86.3
Employee Separation Costs \| Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Employee Separation Costs \| Research and Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Employee Separation Costs \| Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Employee Separation Costs \| Restructuring Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	2.8	66.2	6.9	86.3
Employee Separation Costs \| Other Income [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Asset-Related Charges
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	7.9	90.4	23.9	90.4
Asset-Related Charges \| Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	83.0	5.8	83.0
Asset-Related Charges \| Research and Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	1.0	0.1	1.0
Asset-Related Charges \| Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	7.9	6.4	18.0	6.4
Asset-Related Charges \| Restructuring Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Asset-Related Charges \| Other Income [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Other
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	7.5	8.1	19.4	14.7
Other \| Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Other \| Research and Development Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Other \| Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.0	0.0	0.0
Other \| Restructuring Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	7.5	5.8	19.5	12.4
Other \| Other Income [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0.0	$ 2.3	$ (0.1)	$ 2.3

(Restructuring Reserve Roll Forward) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 20.1	$ 58.2
Restructuring expenses	16.0	49.5
Cash settlements	(16.1)	(70.2)
Adjustments to previous estimates	2.2	0.7
Asset impairments	(7.9)	(23.9)
Ending Balance	14.3	14.3
Employee Separation Costs
Restructuring Reserve [Roll Forward]
Beginning Balance	17.5	53.8
Restructuring expenses	1.1	5.9
Cash settlements	(9.8)	(50.2)
Adjustments to previous estimates	1.7	1.0
Asset impairments	0.0	0.0
Ending Balance	10.5	10.5
Asset-Related Charges
Restructuring Reserve [Roll Forward]
Beginning Balance	0.0	0.0
Restructuring expenses	7.9	23.9
Cash settlements	0.0	0.0
Adjustments to previous estimates	0.0	0.0
Asset impairments	(7.9)	(23.9)
Ending Balance	0.0	0.0
Other
Restructuring Reserve [Roll Forward]
Beginning Balance	2.6	4.4
Restructuring expenses	7.0	19.7
Cash settlements	(6.3)	(20.0)
Adjustments to previous estimates	0.5	(0.3)
Asset impairments	0.0	0.0
Ending Balance	$ 3.8	$ 3.8

Subsequent Event (Details) - Collaboration Agreement with Dicerna Pharmaceuticals, Inc - Subsequent Event	1 Months Ended
	Oct. 31, 2018 USD ($)
Subsequent Event [Line Items]
Payments for exclusive licenses and equity investments	$ 37,000,000
Additional investment fees (up to)	$ 625,000,000.0

Fair Value Measurement (Schedule Of Assets And Liabilites Measured At Fair Value) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities
Foreign Exchange Forward [Member] \| Other Current Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	13.9	$ 48.5
Foreign Exchange Forward [Member] \| Other Current Liabilities \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0.0	0.0
Foreign Exchange Forward [Member] \| Other Current Liabilities \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	13.9	48.5
Foreign Exchange Forward [Member] \| Other Current Liabilities \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0.0	0.0
Foreign Exchange Forward [Member] \| Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	5.8	26.0
Foreign Exchange Forward [Member] \| Other Liabilities \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0.0	0.0
Foreign Exchange Forward [Member] \| Other Liabilities \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	5.8	26.0
Foreign Exchange Forward [Member] \| Other Liabilities \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0.0	0.0
Acquisition Related Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	275.2
Acquisition Related Contingent Consideration [Member] \| ContingentConsiderationCurrent [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	95.8
Acquisition Related Contingent Consideration [Member] \| ContingentConsiderationCurrent [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	0.0
Acquisition Related Contingent Consideration [Member] \| ContingentConsiderationCurrent [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	0.0
Acquisition Related Contingent Consideration [Member] \| ContingentConsiderationCurrent [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	95.8
Acquisition Related Contingent Consideration [Member] \| Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	179.4	168.9
Acquisition Related Contingent Consideration [Member] \| Contingent Consideration [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	0.0	0.0
Acquisition Related Contingent Consideration [Member] \| Contingent Consideration [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	0.0	0.0
Acquisition Related Contingent Consideration [Member] \| Contingent Consideration [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability	179.4	168.9
Interest Rate Contract [Member] \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	14.1	12.5
Interest Rate Contract [Member] \| Other Assets \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	0.0	0.0
Interest Rate Contract [Member] \| Other Assets \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	14.1	12.5
Interest Rate Contract [Member] \| Other Assets \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	0.0	0.0
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	22.6	9.3
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	0.0	0.0
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	22.6	9.3
Interest Rate Contract [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	0.0	0.0
Money Market Funds [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	503.2
Money Market Funds [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0
Money Market Funds [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	503.2
Money Market Funds [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0
Mutual Funds [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	18.9	18.5
Mutual Funds [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	18.9	18.5
Mutual Funds [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Mutual Funds [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Commercial Paper [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	96.1	9.5
Commercial Paper [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Commercial Paper [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	96.1	9.5
Commercial Paper [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Commercial Paper [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	100.0	6.5
Commercial Paper [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Commercial Paper [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	100.0	6.5
Commercial Paper [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Corporate Bond Securities [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1.2
Corporate Bond Securities [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Corporate Bond Securities [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1.2
Corporate Bond Securities [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Corporate Bond Securities [Member] \| Repurchase Agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27.0
Corporate Bond Securities [Member] \| Repurchase Agreements [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Corporate Bond Securities [Member] \| Repurchase Agreements [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27.0
Corporate Bond Securities [Member] \| Repurchase Agreements [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Corporate Bond Securities [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	136.0	431.3
Corporate Bond Securities [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Corporate Bond Securities [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	136.0	431.3
Corporate Bond Securities [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Municipal Bonds [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		5.0
Municipal Bonds [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Municipal Bonds [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		5.0
Municipal Bonds [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0.0
Other Government Obligations [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2.8
Other Government Obligations [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0
Other Government Obligations [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2.8
Other Government Obligations [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0
Other Government Obligations [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	9.5	421.3
Other Government Obligations [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Other Government Obligations [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	9.5	421.3
Other Government Obligations [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0	0.0
Certificates of Deposit [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	1.6
Certificates of Deposit [Member] \| Cash Equivalents [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0
Certificates of Deposit [Member] \| Cash Equivalents [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	1.6
Certificates of Deposit [Member] \| Cash Equivalents [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0.0
Certificates of Deposit [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	41.8
Marketable securities		11.8
Certificates of Deposit [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0
Marketable securities		0.0
Certificates of Deposit [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	41.8
Marketable securities		11.8
Certificates of Deposit [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0
Marketable securities		0.0
Foreign Exchange Forward [Member] \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0.7	4.1
Foreign Exchange Forward [Member] \| Other Assets \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0.0	0.0
Foreign Exchange Forward [Member] \| Other Assets \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0.7	4.1
Foreign Exchange Forward [Member] \| Other Assets \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0.0	0.0
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	27.0	22.9
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0.0	0.0
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	27.0	22.9
Foreign Exchange Forward [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	$ 0.0	0.0
Equity Securities [Member] \| Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0.3
Equity Securities [Member] \| Marketable Securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0.3
Equity Securities [Member] \| Marketable Securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0.0
Equity Securities [Member] \| Marketable Securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		$ 0.0