Alexion Pharmaceuticals (ALXN) 10-K 16 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 13, 2017	Jun. 30, 2016
Entity Information [Line Items]
Entity Registrant Name	ALEXION PHARMACEUTICALS INC
Entity Central Index Key	899,866
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		224,613,750
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 25,314,108,813

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 966	$ 1,010
Marketable securities	327	375
Trade accounts receivable, net	650	533
Inventories	375	290
Prepaid expenses and other current assets	260	208
Total current assets	2,578	2,416
Property, plant and equipment, net	1,036	697
Intangible assets, net	4,303	4,708
Goodwill	5,037	5,048
Other assets	299	228
Total assets	13,253	13,097
Liabilities and Stockholders' Equity
Accounts payable	64	57
Accrued expenses	508	403
Deferred revenue	37	21
Current portion of long-term debt	167	166
Current portion of contingent consideration	24	56
Other current liabilities	23	6
Total current liabilities	823	709
Long-term debt, less current portion	2,888	3,254
Contingent consideration	129	121
Facility lease obligation	233	151
Deferred tax liabilities	396	529
Other liabilities	90	74
Total liabilities	4,559	4,838
Commitments and contingencies (Note 10)
Stockholders' Equity:
Common stock, $.0001 par value; 290 shares authorized; 232 and 230 shares issued at December 31, 2016 and 2015, respectively	0	0
Additional paid-in capital	7,957	7,727
Treasury stock, at cost, 8 and 5 shares at December 31, 2016 and 2015, respectively	(1,141)	(711)
Accumulated other comprehensive income	60	62
Retained earnings	1,818	1,181
Total stockholders' equity	8,694	8,259
Total liabilities and stockholders' equity	$ 13,253	$ 13,097

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Millions	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	290	290
Common stock, shares issued	232	230
Treasury Stock, Shares	8	5

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net product sales	$ 3,082	$ 2,603	$ 2,234
Other revenue	2	1	0
Total revenues	3,084	2,604	2,234
Cost of sales:
Cost of sales	258	233	174
Operating expenses:
Research and development	757	709	514
Selling, general and administrative	954	863	630
Amortization of purchased intangible assets	322	117	0
Change in fair value of contingent consideration	36	64	20
Acquisition-related costs	2	39	0
Restructuring expenses	3	42	15
Impairment of intangible assets	85	0	12
Total operating expenses	2,159	1,834	1,191
Operating income	667	537	869
Other income and expense:
Investment income	11	8	8
Interest expense	(97)	(48)	(3)
Foreign currency gain (loss)	(5)	1	(2)
Income before income taxes	576	498	872
Income tax expense	177	354	215
Net income	$ 399	$ 144	$ 657
Earnings per common share
Basic (in dollars per share)	$ 1.78	$ 0.68	$ 3.32
Diluted (in dollars per share)	$ 1.76	$ 0.67	$ 3.26
Shares used in computing earnings per common share
Basic (in shares)	224	213	198
Diluted (in shares)	227	216	202

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income (loss)	$ 399	$ 144	$ 657
Foreign currency translation	(4)	(6)	(6)
Unrealized losses on marketable securities	0	(1)	0
Unrealized gains (losses) on pension obligation	3	7	(5)
Unrealized (losses) gains on hedging activities, net of tax of $0, $6 and $45, respectively	(1)	6	91
Other comprehensive (loss) income, net of tax	(2)	6	80
Comprehensive income	$ 397	$ 150	$ 737

Consolidated Statement of Comp6

Consolidated Statement of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrealized gains (losses) on hedging activities - tax effect	$ 0	$ 6	$ 45

Statement of Shareholders' Equi

Statement of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balances, common shares at Dec. 31, 2013		198
Balances, treasury shares at Dec. 31, 2013				1
Balances, value at Dec. 31, 2013	$ 2,383	$ 0	$ 2,107	$ (80)	$ (24)	$ 380
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock, shares				2
Repurchase of common stock value	(303)			$ (303)
Issuance of common stock from exercise of options, shares		3
Issuance of common stock from exercise of options, value	114		114
Issuance of restricted common stock, shares		1
Excess tax benefit from stock options, value	251		251
Share-based compensation expense, value	121		121
Net income (loss)	657					657
Other comprehensive income (loss)	80				80
Balances, common shares at Dec. 31, 2014		202
Balances, treasury shares at Dec. 31, 2014				3
Balances, value at Dec. 31, 2014	3,303	$ 0	2,593	$ (383)	56	1,037
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, shares		26
Issuance of common stock, net of issuance costs of $4	4,914		4,914
Repurchase of common stock, shares		0		2
Repurchase of common stock value	(328)			$ (328)
Issuance of common stock from exercise of options, shares		1
Issuance of common stock from exercise of options, value	82		82
Issuance of restricted common stock, shares		1
Excess tax benefit from stock options, value	(90)		(90)
Share-based compensation expense, value	228		228
Net income (loss)	144					144
Other comprehensive income (loss)	$ 6				6
Balances, common shares at Dec. 31, 2015		230
Balances, treasury shares at Dec. 31, 2015	5			5
Balances, value at Dec. 31, 2015	$ 8,259	$ 0	7,727	$ (711)	62	1,181
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new share-based compensation guidance, value	238					238
Repurchase of common stock, shares				3
Repurchase of common stock value	$ (430)			$ (430)
Issuance of common stock from exercise of options, shares	1	1
Issuance of common stock from exercise of options, value	$ 37		37
Issuance of restricted common stock, shares		1
Excess tax benefit from stock options, value	0		0
Share-based compensation expense, value	193		193
Net income (loss)	399					399
Other comprehensive income (loss)	$ (2)				(2)
Balances, common shares at Dec. 31, 2016		232
Balances, treasury shares at Dec. 31, 2016	8			8
Balances, value at Dec. 31, 2016	$ 8,694	$ 0	$ 7,957	$ (1,141)	$ 60	$ 1,818

Statement of Cash Flows

Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ 399	$ 144	$ 657
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	396	167	47
Impairment of intangible assets	85	0	12
Change in fair value of contingent consideration	36	64	20
Share-based compensation expense	192	227	114
Deferred taxes	104	395	(154)
Change in excess tax benefit from stock options	0	90	(251)
Other	10	3	37
Changes in operating assets and liabilities, excluding the effect of acquisitions:
Accounts receivable	(122)	(116)	(28)
Inventories	(84)	(88)	(67)
Prepaid expenses and other assets	(97)	(57)	(18)
Accounts payable, accrued expenses and other liabilities	150	(116)	265
Deferred revenue	17	(38)	6
Net cash provided by operating activities	1,086	675	640
Cash flows from investing activities:
Purchases of available-for-sale securities	(667)	(520)	(664)
Proceeds from maturity or sale of available-for-sale securities	718	1,160	620
Purchases of trading securities	(8)	(15)	(3)
Proceeds from sale of trading securities	4	10	0
Purchases of property, plant and equipment	(333)	(286)	(137)
Purchases of other investments	0	0	(38)
Payments for acquisitions of businesses, net of cash acquired	0	(3,939)	0
Other	(1)	5	(1)
Net cash used in investing activities	(287)	(3,585)	(223)
Cash flows from financing activities:
Debt issuance costs	0	(45)	0
Proceeds from revolving credit facility	0	200	0
Payments on revolving credit facility	0	(200)	0
Proceeds from term loan	0	3,500	0
Payments on term loan	(375)	(101)	(55)
Equity issuance costs for shares issued in connection with acquisition of business	0	(4)	0
Change in excess tax benefit from stock options	0	(90)	251
Repurchase of common stock	(430)	(328)	(303)
Net proceeds from issuance of stock under share-based compensation arrangements	37	82	114
Payment of contingent consideration	(60)	(50)	0
Proceeds from development-related grants	0	26	0
Other	(8)	(5)	0
Net cash (used in) provided by financing activities	(836)	2,985	7
Effect of exchange rate changes on cash	(7)	(9)	(10)
Net change in cash and cash equivalents	(44)	66	414
Cash and cash equivalents at beginning of period	1,010	944	530
Cash and cash equivalents at end of period	966	1,010	944
Supplemental disclosures
Cash paid for interest (net of amounts capitalized)	80	41	2
Cash paid for income taxes	38	123	91
Supplemental cash flow disclosures from investing and financing activities:
Common stock issued in acquisition of business	0	4,918	0
Capitalization of construction costs related to facility lease obligations	103	41	75
Accrued expenses for purchases of property, plant and equipment	$ 23	$ 30	$ 17

Business Overview and Summary o

Business Overview and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Business Overview and Summary of Significant Accounting Policies [Abstract]
Business Overview and Summary of Significant Accounting Policies	Business Overview and Summary of Significant Accounting Policies Business Alexion Pharmaceuticals, Inc. (Alexion, the Company, we, our or us) is a biopharmaceutical company focused on serving patients with devastating and ultra-rare disorders through the innovation, development and commercialization of life-transforming therapeutic products. In our complement franchise, Soliris® is the first and only therapeutic approved for patients with either paroxysmal nocturnal hemoglobinuria (PNH), a life-threatening and ultra-rare genetic blood disorder, or atypical hemolytic uremic syndrome (aHUS), a life-threatening and ultra-rare genetic disease. PNH and aHUS are two disorders resulting from chronic uncontrolled activation of the complement component of the immune system. In our metabolic franchise, we commercialize Strensiq® for the treatment of patients with Hypophosphatasia (HPP) and Kanuma® for the treatment of patients with Lysosomal Acid Lipase Deficiency (LAL-D). HPP is an ultra-rare genetic disease characterized by defective bone mineralization that can lead to deformity of bones and other skeletal abnormalities. LAL-D is a serious, life threatening ultra-rare disease in which genetic mutations result in decreased activity of the Lysosomal Acid Lipase (LAL) enzyme leading to marked accumulation of lipids in vital organs, blood vessels and other tissues. We initiated sales of these products in the third quarter 2015. We are also evaluating additional potential indications for eculizumab in other severe and devastating diseases in which uncontrolled complement activation is the underlying mechanism, and we are progressing in various stages of development with additional product candidates as potential treatments for patients with devastating and ultra-rare disorders. In June 2015, we acquired all of the outstanding shares of common stock of Synageva BioPharma Corp. (Synageva), a publicly-held clinical-stage biotechnology company. The acquisition furthered our objective to develop and commercialize life-transforming therapies for patients with devastating and ultra-rare diseases. Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements include the accounts of Alexion and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. For each of our business combinations, all of the assets acquired and liabilities assumed were recorded at their respective fair values as of the date of acquisition, and their results of operations are included in the consolidated financial statements from the date of acquisition. Dividend Policy We have never paid a cash dividend on shares of our stock. We currently intend to retain our earnings to finance future operations and do not anticipate paying any cash dividends on our stock in the foreseeable future. Critical Accounting Estimates The preparation of our consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the U.S., requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosure of contingent assets and liabilities in our financial statements. We believe the most complex judgments result primarily from the need to make estimates about the effects of matters that are inherently uncertain and are significant to our consolidated financial statements. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. We evaluate our estimates, judgments and assumptions on an ongoing basis. Actual results may differ from these estimates under different assumptions or conditions. The most significant areas involving estimates, judgments and assumptions used in the preparation of our consolidated financial statements are as follows: • Revenue recognition; • Contingent liabilities; • Inventories; • Share-based compensation; • Valuation of goodwill, acquired intangible assets and in-process research and development (IPR&D); • Valuation of contingent consideration; and • Income taxes. Foreign Currency Translation The financial statements of our subsidiaries with functional currencies other than the U.S. dollar are translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates for operating results. Translation gains and losses are included in accumulated other comprehensive income (loss), net of tax, in stockholders’ equity. Foreign currency transaction gains and losses are included in the results of operations in other income and expense. Cash and Cash Equivalents Cash and cash equivalents are stated at cost plus accrued interest, which approximates fair value, and include short-term highly liquid investments with original maturities of three months or less. Fair Value of Financial Instruments The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, accounts receivable, other assets, accounts payable, accrued expenses and other liabilities approximate fair value due to their short-term maturities. Our marketable securities are valued based upon pricing of securities with similar investment characteristics and holdings. Our derivative financial instruments are measured at fair value using observable market inputs such as forward rates, interest rates, our own credit risk and our counterparties’ credit risks. Our debt obligations are carried at historical cost, which approximates fair value. Our contingent consideration liabilities related to our acquisitions are valued based on various estimates, including probability of success, estimated revenues, discount rates and amount of time until the conditions of the milestone payments are met. Marketable Securities We invest our excess cash balances in marketable securities of highly rated financial institutions and investment-grade debt instruments. We seek to diversify our investments and limit the amount of investment concentrations for individual institutions, maturities and investment types. We classify these marketable securities as available-for-sale and, accordingly, record such securities at fair value. We classify these marketable securities as current assets as these investments are intended to be available to the Company for use in funding current operations. Unrealized gains and losses that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If any adjustment to fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our consolidated statement of operations. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive income (loss). We sponsor a nonqualified deferred compensation plan which allows certain highly-compensated employees to elect to defer income to future periods. Participants in the plan earn a return on their deferrals based on several investments options, which mirror returns on underlying mutual fund investments. We choose to invest in the underlying mutual fund investments to offset the liability associated with our nonqualified deferred compensation plan. These securities are classified as trading securities and are carried at fair value with gains and losses included in investment income. The changes in the underlying liability to the employee are recorded in operating expenses. Accounts Receivable Our standard credit terms vary based on the country of sale and range from 30 to 120 days. Our consolidated average days’ sales outstanding ranges from 60 to 80 days. 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. For non-interest bearing receivables with an estimated payment beyond one year, we discount the accounts receivable to present value at the date of sale, with a corresponding adjustment to revenue. 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 reasonably assured at the time of sale. Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk are limited to cash equivalents, marketable securities, accounts receivable and our foreign exchange derivative contracts. We invest our cash reserves in money market funds or high-quality marketable securities in accordance with our investment policy. The stated objectives of our investment policy is to preserve capital, provide liquidity consistent with forecasted cash flow requirements, maintain appropriate diversification and generate returns relative to these investment objectives and prevailing market conditions. At December 31, 2016 , three customers accounted for 47% of the accounts receivable balance, with these individual customers ranging from 14% to 19% of the accounts receivable balance. At December 31, 2015 , three customers accounted for 51% of the accounts receivable balance, with these individual customers ranging from 14% to 22% of the accounts receivable balance. For the year ended December 31, 2016 , three customers accounted for 37% of our product sales, with these individual customers ranging from 10% to 16% of our product sales. For the year ended December 31, 2015 , three customers accounted for 38% of our product sales, with these individual customers ranging from 10% to 18% of our product sales. No other customers accounted for more than 10% of accounts receivable or net product sales. David Anderson, Alexion’s Executive Vice President and Chief Financial Officer since December 2016, has been a member of the Board of Directors of Cardinal Health, Inc. since April 2014. Cardinal Health, Inc. and its affiliates provide product distribution and other services to Alexion in the United States. As a result of our foreign operations, we are exposed to changes in the general economic conditions in the countries in which we conduct business. Substantially all of our accounts receivable due from these countries are due from or backed by sovereign or local governments, and the amount of non-sovereign accounts receivable is not material. We continue to monitor economic conditions, including volatility associated with international economies and the associated impacts on the financial markets and our business. Although collection of our accounts receivables due from certain countries may extend beyond our standard credit terms, we do not expect any such delays to have a material impact on our financial condition or results of operations. Inventories Inventories are stated at the lower of cost or estimated realizable value. We determine the cost of inventory on a standard cost basis, which approximates average costs. The components of inventory are as follows: December 31, 2016 2015 Raw materials $ 17 $ 18 Work-in-process 143 180 Finished goods 215 92 $ 375 $ 290 Capitalization of Inventory Costs We capitalize inventory produced for commercial sale, which may include costs incurred for certain products awaiting regulatory approval. We capitalize inventory produced in preparation of product launches sufficient to support estimated initial market demand. Capitalization of such inventory begins when we have (i) obtained positive results in clinical trials that we believe are necessary to support regulatory approval, (ii) concluded that uncertainties regarding regulatory approval have been sufficiently reduced, and (iii) determined that the inventory has probable future economic benefit. In evaluating whether these conditions have been met, we consider clinical trial results for the underlying product candidate, results from meetings with regulatory authorities, and the compilation of the regulatory application. If we are aware of any material risks or contingencies outside of the standard regulatory review and approval process, or if there are any specific negative issues identified relating to the safety, efficacy, manufacturing, marketing or labeling of the product that would have a significant negative impact on its future economic benefits, the related inventory would not be capitalized. We had no inventory capitalized for products awaiting regulatory approval as of December 31, 2016 and 2015 . Products that have been approved by the U.S. Food and Drug Administration (FDA) or other regulatory authorities are also used in clinical programs to assess the safety and efficacy of the products for usage in diseases that have not been approved by the FDA or other regulatory authorities. The form of the products utilized for both commercial and clinical programs is identical and, as a result, the inventory has an “alternative future use” as defined in authoritative guidance. Raw materials and purchased drug product associated with clinical development programs are included in inventory and charged to research and development expense when the product enters the research and development process and no longer can be used for commercial purposes and, therefore, does not have an “alternative future use”. For products which are under development and have not yet been approved by regulatory authorities, purchased drug product is charged to research and development expense upon delivery. Delivery occurs when the inventory passes quality inspection and ownership transfers to us. Nonrefundable advance payments for research and development activities, including production of purchased drug product, are deferred and capitalized until the goods are delivered. We also recognize expense for raw materials purchased for developmental purposes when the raw materials pass quality inspection and we have an obligation to pay for the materials. Inventory Write-Offs We analyze our inventory levels to identify inventory that may expire prior to sale, inventory that has a cost basis in excess of its estimated realizable value, or inventory in excess of expected sales requirements. Although the manufacturing of our product is subject to strict quality control, certain batches or units of product may no longer meet quality specifications or may expire, which requires adjustments to our inventory values. We also apply judgment related to the results of quality tests that we perform throughout the production process, as well as our understanding of regulatory guidelines, to determine if it is probable that inventory will be saleable. These quality tests are performed throughout the pre-and post-production process, and we continually gather additional information regarding product quality for periods after the manufacture date. Our products currently have a maximum estimated life ranging from 36 to 48 months and, based on our sales forecasts, we expect to realize the carrying value of our inventory. In the future, reduced demand, quality issues or excess supply beyond those anticipated by management may result in a material adjustment to inventory levels, which would be recorded as an increase to cost of sales. The determination of whether or not inventory costs will be realizable requires estimates by our management. A critical input in this determination is future expected inventory requirements based on internal sales forecasts. We then compare these requirements to the expiry dates of inventory on hand. For inventories that are capitalized in preparation of product launch, we also consider the expected approval date in assessing realizability. To the extent that inventory is expected to expire prior to being sold, we will write down the value of inventory. Derivative Instruments We record the fair value of derivative instruments as either assets or liabilities on the balance sheet. The accounting for gains and losses resulting from changes in fair value is dependent on the use of the derivative and whether it is designated and qualifies for hedge accounting. All qualifying hedging activities are documented at the inception of the hedge and must meet the definition of highly effective in offsetting changes to future cash. The effectiveness of the qualifying hedge contract is assessed quarterly. We record the fair value of the qualifying hedges in other current assets, other assets, other current liabilities and other liabilities. Gains or losses resulting from changes in the fair value of qualifying hedges are recorded in other comprehensive income (loss) until the forecasted transaction occurs. When the forecasted transaction occurs, this amount is reclassified into revenue or interest expense, based on the nature of the derivative instrument. Any non-qualifying portion of the gains or losses resulting from changes in fair value, if any, is reported in other income and expense. Property, Plant and Equipment Property, plant and equipment are stated at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. We estimate economic lives as follows: • Building and improvements—fifteen to thirty five years • Machinery and laboratory equipment—five to fifteen years • Computer hardware and software—three to seven years • Furniture and office equipment— five to ten years Leasehold improvements and assets under capital lease arrangements are amortized over the lesser of the asset’s estimated useful life or the term of the respective lease. Maintenance costs are expensed as incurred. Construction-in-progress reflects amounts incurred for property, plant, or equipment construction or improvements that have not been placed in service. Manufacturing Facilities We capitalize costs incurred for the construction of facilities which support commercial manufacturing. We also capitalize costs related to validation activities which are directly attributable to preparing the facility for its intended use, including engineering runs and inventory production necessary to obtain approval of the facility from government regulators for the production of a commercially approved drug. When the facility is substantially complete and ready for its intended use and regulatory approval for commercial production has been received, we will place the asset in service. The production of inventory for preparing the facility for its intended use requires two types of production: engineering runs which are used for testing purposes only and do not result in saleable inventory, and validation runs which are used for validating equipment and may result in saleable inventory. The costs associated with inventory produced during engineering runs and normal production losses during validation runs are capitalized to fixed assets and depreciated over the asset’s useful life. Saleable inventory produced during the validation process is initially treated as a fixed asset; however, upon regulatory approval, this inventory is reclassified to inventory and expensed in cost of goods sold as product is sold, or in research and development expenses as product is utilized in R&D activities. Abnormal production costs incurred during the validation process are expensed as incurred. Acquisitions Business combinations are accounted for using the acquisition method of accounting. Under the acquisition method of accounting, the tangible and intangible assets acquired and the liabilities assumed are recorded as of the acquisition date at their respective fair values. We evaluate a business as an integrated set of activities and assets that is capable of being managed for the purpose of providing a return in the form of dividends, lower costs or other economic benefits and consists of inputs and processes that provide or have the ability to provide outputs. In an acquisition of a business, the excess of the fair value of the consideration transferred over the fair value of the net assets acquired is recorded as goodwill. In an acquisition of net assets that does not constitute a business, no goodwill is recognized. Our consolidated financial statements include the results of operations of an acquired business after the completion of the acquisition. Intangible Assets Our intangible assets consist of licenses, patents, purchased technology and acquired in-process research and development (IPR&D). Intangible assets with definite lives are amortized based on their pattern of economic benefit over their estimated useful lives and reviewed periodically for impairment. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment. If and when development is complete, which generally occurs when regulatory approval to market a product is obtained, the associated assets are deemed finite-lived and are amortized over a period that best reflects the economic benefits provided by these assets. Goodwill Goodwill represents the excess of purchase price over fair value of net assets acquired in a business combination and is not amortized. Goodwill is subject to impairment testing at least annually or when a triggering event occurs that could indicate a potential impairment. We are organized and operate as a single reporting unit and therefore the goodwill impairment test is performed using our overall market value, as determined by our traded share price, compared to our book value of net assets. Impairment of Long-Lived Assets Our long-lived assets are primarily comprised of intangible assets and property, plant and equipment. We evaluate our finite-lived intangible assets and property, plant and equipment, for impairment whenever events or changes in circumstances indicate the carrying value of an asset or group of assets is not recoverable. If these circumstances exist, recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. In addition, indefinite-lived intangible assets, comprised of IPR&D, are reviewed for impairment annually and whenever events or changes in circumstances indicate that it is more likely than not that the asset is impaired by comparing the fair value to the carrying value of the asset. Contingent Consideration We record contingent consideration resulting from a business combination at its fair value on the acquisition date. On a quarterly basis, we revalue these obligations and record increases or decreases in their fair value as an adjustment to operating earnings. Changes to contingent consideration obligations can result from adjustments to discount rates, accretion of the liability due to the passage of time, changes in our estimates of the likelihood or timing of achieving development or commercial milestones, changes in the probability of certain clinical events or changes in the assumed probability associated with regulatory approval. Contingent Liabilities We are currently involved in various claims and legal proceedings. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, we accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals are based on our best estimates based on available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims, we may reassess the potential liability related to these matters and may revise these estimates. Treasury Stock Treasury stock is accounted for using the cost method, with the purchase price of the common stock recorded separately as a deduction from stockholders’ equity. Revenue Recognition Our principal source of revenue is product sales. We recognize revenue from product sales when persuasive evidence of an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collection from the customer is reasonably assured, and we have no further performance obligations. Depending on these criteria, revenue is usually recorded upon receipt of the product by the end customer, which is typically a hospital, physician’s office, private or government pharmacy or other healthcare facility. On a regular basis, we review revenue arrangements, such as distributor relationships, to determine whether changes in these criteria have an impact on revenue recognition. Amounts collected from customers and remitted to governmental authorities, such as value-added taxes (VAT) in foreign jurisdictions, are presented on a net basis in our consolidated statements of operations and do not impact net product sales. 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. 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 the lack of contractual return rights, our customers often carry limited inventory. We also monitor inventory within our sales channels to determine whether deferrals are appropriate based on factors such as inventory levels compared to demand, contractual terms, financial strength of distributors and our ability to estimate returns. In some cases, exact quantities of inventory in the channel are not precisely known, requiring us to estimate these amounts. If actual amounts of inventory differ from these estimates, these adjustments could have an impact in the period in which these estimates change. 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. We record estimated rebates payable under governmental programs, including Medicaid in the U.S. and other programs outside the U.S., as a reduction of revenue at the time of product sale. Our calculations related to these rebate accruals require 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. We have entered into volume-based arrangements with governments in certain countries 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 these governments as a rebate. We estimate incremental discounts resulting from these contractual limitations, based on estimated 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. We record distribution and other fees paid to our customers as a reduction of revenue, unless we receive an identifiable and separate benefit for the consideration and we can reasonably estimate the fair value of the benefit 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. We enter into foreign exchange forward contracts to hedge exposures resulting from portions of our forecasted revenues, including intercompany revenues, that are denominated in currencies other than the U.S. dollar. These hedges are designated as cash flow hedges upon inception. We record the effective portion of these cash flow hedges to revenue in the period in which the sale is made to an unrelated third party and the derivative contract is settled. Research and Development Expenses Research and development expenses are comprised of costs incurred in performing research and development activities including payroll and benefits, pre-clinical, clinical trial and related clinical manufacturing costs, manufacturing development and scale-up costs, product development and regulatory costs, contract services and other outside contractor costs, research license fees, depreciation and amortization of lab facilities, and lab supplies. These costs are expensed as incurred. We accrue costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the contract research organizations, clinical study sites, laboratories, consultants, or other clinical trial vendors that perform the activities. Share-Based Compensation We have two share-based compensation plans pursuant to which awards are currently being made: (i) the Amended and Restated 2004 Incentive Plan (2004 Plan) and (ii) the 2015 Employee Stock Purchase Plan (ESPP). Under the 2004 Plan, restricted stock, restricted stock units, stock options and other stock-related awards may be granted to our directors, officers, employees and consultants or advisors of the Company or any subsidiary. Under the ESPP, eligible employees can purchase shares of common stock at a discount semi-annually through payroll deductions. To date, share-based compensation issued under the plans consists of incentive and non-qualified stock options, restricted stock and restricted stock units, including restricted stock units with market and non-market performance conditions, and shares issued under our ESPP. Compensation expense for our share-based awards is recognized based on the estimated fair value of the awards on the grant date. Compensation expense reflects an estimate of the number of awards expected to vest and is primarily recognized on a straight-line basis over the requisite service period of the individual grants, which typically equals the vesting period. Compensation expense for awards with performance conditions is recognized using the graded-vesting method. Our estimates of employee stock option values rely on estimates of factors we input into the Black-Scholes model. The key factors involve an estimate of future uncertain events. Significant assumptions include the use of historical volatility to determine the expected stock price volatility. We also estimate expected term until exercise and the reduction in the expense from expected forfeitures. W

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisitions	Acquisitions On June 22, 2015, we completed the acquisition of Synageva, in a transaction accounted for under the acquisition method of accounting for business combinations. Under the acquisition method of accounting, the assets acquired and liabilities assumed from Synageva were recorded as of the acquisition date at their respective fair values. Synageva’s results of operations are included in the consolidated financial statements from the date of acquisition. The acquisition furthered our objective to develop and commercialize life-transforming therapies to an increasing number of patients with devastating and rare diseases. Synageva’s lead product candidate was Kanuma, an enzyme replacement therapy for patients suffering with LAL-D, a life-threatening, ultra-rare disease for which there were no approved treatments at the closing of the business combination. We acquired all of the outstanding shares of common stock of Synageva for $4,565 in cash and 26 shares of common stock. We financed the cash consideration with existing cash and proceeds from our new credit facility described further in Note 8. The aggregate consideration to acquire Synageva consisted of: Stock consideration $ 4,918 Cash consideration 4,565 Total purchase price $ 9,483 The following table summarizes the estimated fair values of assets acquired and liabilities assumed: Cash $ 626 Inventory 24 In-process research and development (IPR&D) 4,236 Deferred tax liabilities, net (160 ) Other assets and liabilities (26 ) Net assets acquired 4,700 Goodwill 4,783 Total purchase price $ 9,483 The fair value of the assets acquired and liabilities assumed were initially based upon preliminary calculations, and our estimates and assumptions were subject to change as we obtained additional information for our estimates during the measurement period (up to one year from the acquisition date). During the year ended December 31, 2016, we recorded fair value adjustments of $11 primarily due to tax related items. We acquired $24 of Kanuma inventory. The estimated fair value of work-in-process and finished goods inventory was determined utilizing the comparative sales method, based on the expected selling price of the inventory, adjusted for incremental costs to complete the manufacturing process and for direct selling efforts, as well as for a reasonable profit allowance. The estimated fair value of raw material inventory was valued at replacement cost, which is equal to the value a market participant would pay to acquire the inventory. Intangible assets associated with IPR&D projects primarily relate to Kanuma. The estimated fair value of IPR&D assets of $4,236 was determined using the multi-period excess earnings method, a variation of the income approach. The multi-period excess earnings method estimates the value of an intangible asset equal to the present value of the incremental after-tax cash flows attributable to that intangible asset. The fair value using the multi-period excess earnings method was dependent on an estimated weighted average cost of capital for Synageva of 10% , which represents a rate of return that a market participant would expect for these assets. The excess of purchase price over the fair value amounts of the assets acquired and liabilities assumed represents the goodwill amount resulting from the acquisition. The goodwill, which is not tax-deductible, has been recorded as a noncurrent asset and is not amortized, but is subject to an annual review for impairment. The goodwill represents future economic benefits arising from other assets acquired that could not be individually identified and separately recognized and expected synergies that are specific to our business and not available to market participants, including our unique ability to commercialize therapies for rare diseases, our existing relationships with specialty physicians who can identify patients with LAL-D, a global distribution network to facilitate drug delivery and other benefits that we believe will result from combining the operations of Synageva within our operations. We recorded a net deferred tax liability of $160 . This amount was primarily comprised of $603 of deferred tax liabilities related to the IPR&D and inventory acquired, offset by $443 of deferred tax assets related to net operating loss carryforwards (NOLs), tax credits, and other temporary differences, which we expect to utilize. For the year ended December 31, 2015, we recorded $96 of pre-tax operating losses associated with the continuing operations of Synageva in our consolidated statements of operations. Pro forma financial information (unaudited) The following unaudited pro forma information presents the combined results of Alexion and Synageva as if the acquisition of Synageva had been completed on January 1, 2014, with adjustments to give effect to pro forma events that are directly attributable to the acquisition. The unaudited pro forma results do not reflect operating efficiencies or potential cost savings which may result from the consolidation of operations. Accordingly, the unaudited pro forma financial information is not necessarily indicative of the results of operations that would have had we completed the transaction on January 1, 2014. Year Ended December 31, Year Ended December 31, 2015 2014 Pro forma revenues $ 2,606 $ 2,240 Pro forma net income 21 261 Earnings per common share Basic $ 0.09 $ 1.16 Diluted $ 0.09 $ 1.14 The unaudited pro forma consolidated results include the following pro forma adjustments related to non-recurring activity: • Alexion and Synageva expenses of $33 and $127 , respectively, associated with the accelerated vesting of stock based compensation as a result of the acquisition were excluded from net income for the year ended December 31, 2015. These expenses were included in net income for the year ended December 31, 2014; • Alexion and Synageva acquisition-related and restructuring costs of $53 and $62 , respectively, were excluded from income for the year ended December 31, 2015. These expenses were included in net income for the year ended December 31, 2014. Acquisition-Related Costs Acquisition-related costs associated with our business combinations for the years ended December 31, 2016 , 2015 and 2014 include the following: Year Ended December 31, 2016 2015 2014 Transaction costs (1) $ — $ 27 $ — Integration costs 2 12 — $ 2 $ 39 $ — (1) Transaction costs include investment advisory, legal, and accounting fees The acquisition of Synageva resulted in $13 of restructuring related charges for the year ended December 31, 2015. Synageva restructuring related charges were not material for the year ended December 31, 2016. See Note 17 for additional details.

Property, Plant and Equipment,

Property, Plant and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net A summary of property, plant and equipment is as follows: December 31, 2016 December 31, 2015 Land $ 10 $ 9 Buildings and improvements 450 252 Machinery and laboratory equipment 126 92 Computer hardware and software 123 84 Furniture and office equipment 25 16 Construction-in-progress 495 420 1,229 873 Less: Accumulated depreciation and amortization (193 ) (176 ) $ 1,036 $ 697 Included in construction-in-progress at December 31, 2015 was $227 of costs associated with the construction of our facility in New Haven, Connecticut. This facility was placed into service in 2016. Additionally, there were costs of $118 and $19 as of December 31, 2016 and 2015 , included within construction-in-process associated with the construction of a new manufacturing facility. Although we will not legally own these premises, we are deemed to be the owner of the buildings during the construction period based on applicable accounting guidance for build-to-suit leases, see Note 9, “Facility Lease Obligations” for additional information. In connection with the construction of the facility in New Haven, Connecticut, we entered into an agreement with the State of Connecticut Department of Economic and Community Development which provides for a forgivable loan and grants totaling $26 and tax credits of up to $25 . The program requires that we meet certain criteria in order to prevent forfeiture or repayment of the loan, grants and credits, which include (i) maintaining corporate headquarters in Connecticut for ten years ; (ii) satisfying minimum employment obligations; and (iii) minimum capital spending requirements. In the third quarter 2015, we received $26 for the forgivable loan and grants. In 2016, we satisfied the second and third criteria. The proceeds reduce the costs of our assets associated with the project. As of December 31, 2016 , we have not received any tax credits associated with our agreement with the State of Connecticut. Depreciation and amortization of property, plant and equipment was approximately $64 , $44 and $35 for the years ended December 31, 2016 , 2015 and 2014 , respectively. At December 31, 2016 and 2015 , computer software costs included in property, plant and equipment were $37 and $20 , respectively. Depreciation and amortization expense for capitalized computer software costs was $12 , $10 and $7 for the years ended December 31, 2016 , 2015 and 2014 , respectively.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible assets and goodwill, net of accumulated amortization, are as follows: December 31, 2016 December 31, 2015 Estimated Cost Accumulated Net Cost Accumulated Net Licenses 6-8 $ 29 $ (29 ) $ — $ 29 $ (29 ) $ — Patents 7 11 (11 ) — 11 (11 ) — Purchased technology 6-16 4,711 (439 ) 4,272 4,709 (117 ) 4,592 Acquired IPR&D Indefinite 31 — 31 116 — 116 Total $ 4,782 $ (479 ) $ 4,303 $ 4,865 $ (157 ) $ 4,708 Goodwill Indefinite $ 5,040 $ (3 ) $ 5,037 $ 5,051 $ (3 ) $ 5,048 Amortization expense was $322 , $117 and $11 for the years ended December 31, 2016 , 2015 and 2014 , respectively. Assuming no changes in the gross cost basis of intangible assets, the total estimated amortization expense for finite-lived intangible assets is $320 for each of the years ending December 31, 2017 through December 31, 2021 . During the fourth quarter 2016, we reviewed SBC-103, an early stage clinical indefinite-lived intangible asset related to the Synageva acquisition as part of our annual impairment testing. The fair value of this IPR&D asset was determined using the income approach and included significant unobservable (Level 3) inputs. These unobservable inputs included, among other things, expected development, regulatory and commercial time lines, risk-adjusted forecasted future cash flows to be generated by this asset, contributory asset charges for other assets employed in this IPR&D project and the determination of an appropriate discount rate based on a weighted cost of capital of 12% to be applied in calculating the present value of future cash flows. Based on our strategic portfolio evaluation, increases in development, regulatory and commercial time lines and updated cash flows, the estimated value that can be obtained for this asset from a market participant in an arm’s length transaction is $31 , which was lower than the carrying amount of the asset. As a result, in the fourth quarter 2016, we recognized an impairment charge of $85 to write-down this asset to fair value. The impairment was recorded in operating expenses in our consolidated statement of operations for the year ended December 31, 2016 . In February 2017, the Board of Directors of Alexion made the decision to reduce our investment in SBC-103. The current Phase I/II clinical trial will not be expanded and no new patients will be added to the trial. Patients currently enrolled in the trial will continue to receive therapy. We will reassess the value of this asset on a go forward basis for indicators of impairment. The following table summarizes the changes in the carrying amount of goodwill: Balance at December 31, 2014 $ 254 Goodwill resulting from the Synageva acquisition 4,794 Balance at December 31, 2015 $ 5,048 Change in goodwill associated with prior acquisition $ (11 ) Balance at December 31, 2016 $ 5,037

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities The amortized cost, gross unrealized holding gains, gross unrealized holding losses and estimated fair value of available-for-sale investments by type of security at December 31, 2016 and December 31, 2015 were as follows: December 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 114 $ — $ — $ 114 Corporate bonds 124 — (1 ) 123 Municipal bonds 91 — — 91 Other government related obligations: U.S. 28 — — 28 Foreign 73 — (1 ) 72 Bank certificates of deposit 5 — — 5 Total available-for-sale debt securities $ 435 $ — $ (2 ) $ 433 Equity securities — 1 — 1 Total available-for-sale securities $ 435 $ 1 $ (2 ) $ 434 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 254 $ — $ — $ 254 Corporate bonds 133 — — 133 Municipal bonds 87 — — 87 Other government related obligations: U.S. 25 — — 25 Foreign 164 — (1 ) 163 Bank certificates of deposit 27 — — 27 Total available-for-sale securities $ 690 $ — $ (1 ) $ 689 The aggregate fair value of available-for-sale securities in an unrealized loss position as of December 31, 2016 and December 31, 2015 was $265 and $294 . Investments that have been in a continuous unrealized loss position for more than 12 months were not material. As of December 31, 2016 we believe that the cost basis of our available-for-sale investments is recoverable. The fair values of available-for-sale securities by classification in the consolidated balance sheet were as follows: December 31, 2016 December 31, 2015 Cash and cash equivalents $ 120 $ 323 Marketable securities 314 366 $ 434 $ 689 The fair values of available-for-sale debt securities at December 31, 2016 , by contractual maturity, are summarized as follows: December 31, 2016 Due in one year or less $ 236 Due after one year through three years 197 Due after three years through five years — $ 433 As of December 31, 2016 and December 31, 2015 , the fair value of our trading securities was $13 and $9 . We utilize the specific identification method in computing realized gains and losses. Realized gains and losses on our available-for-sale and trading securities were not material for the year ended December 31, 2016 and 2015 .

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities [Abstract]
Derivative Instruments and Hedging Activities	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 our outstanding term loan debt. 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, 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 and to increase the visibility of the foreign exchange impact on forecasted revenues. These hedges are designated as cash flow hedges upon contract inception. At December 31, 2016 , we had open foreign exchange forward contracts with notional amounts totaling $1,742 that qualified for hedge accounting. To achieve a desired mix of floating and fixed interest rates on our term loan, we entered into two interest rate swap agreements in June 2016 that qualified for and are designated as cash flow hedges. The first agreement had a notional amount of $3,281 and was effective from June 30, 2016 through December 30, 2016. This agreement hedged the contractual floating interest rate of our term loan. As a result of this agreement, the interest rate for our term loan was fixed at 0.535% , plus the borrowing spread, until December 30, 2016. The second agreement has a notional amount of $656 and is effective December 31, 2016 through December 31, 2019. The second agreement converts the floating rate on a portion of our term loan to a fixed rate of 0.98% , plus a borrowing spread, from December 31, 2016 through December 2019. In the first quarter of 2017, we entered into an additional interest rate swap agreement with a notional amount of $300 that is effective from January 31, 2017 through December 31, 2018 that converts the floating rate on a portion of our term loan to a fixed rate of 1.29% , plus a borrowing spread, from January 2017 through December 2018. The impact on accumulated other comprehensive income (AOCI) and earnings from derivative instruments that qualified as cash flow hedges, for the years ended December 31, 2016 and 2015 were as follows: Year Ended December 31, Foreign Exchange Contracts: 2016 2015 Gain recognized in AOCI, net of tax $ 40 $ 111 Gain reclassified from AOCI to net product sales (effective portion), net of tax $ 47 $ 103 Gain reclassified from AOCI to other income and expense (ineffective portion), net of tax $ — $ 2 Interest Rate Contracts: Gain recognized in AOCI, net of tax $ 6 $ — Gain reclassified from AOCI to interest expense, net of tax $ — $ — Assuming no change in foreign exchange rates or LIBOR-based interest rates from market rates at December 31, 2016 , $78 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 immaterial. We enter into foreign exchange forward contracts, with durations of approximately 90 days, designed to limit the balance sheet exposure of monetary assets and liabilities. We enter into these hedges to reduce the impact of fluctuating exchange rates on our operating results. Hedge accounting is not applied to these derivative instruments as gains and losses on these hedge transactions are designed to offset gains and losses on underlying balance sheet exposures. As of December 31, 2016 , the notional amount of foreign exchange contracts where hedge accounting is not applied was $647 . We recognized a (loss) gain of $(5) , $5 and $26 , in other income and expense, for the years ended December 31, 2016 , 2015 and 2014 , respectively, associated with the foreign exchange contracts not designated as hedging instruments. These amounts were largely offset by gains or losses in monetary assets and liabilities. The following tables summarize the fair value of outstanding derivatives at December 31, 2016 and 2015 : December 31, 2016 Asset Derivatives Liability Derivatives Balance Sheet Fair Balance Sheet Fair Derivatives designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets $ 80 Other current liabilities $ 2 Foreign exchange forward contracts Other assets 59 Other liabilities 4 Interest rate contracts Prepaid expenses and other current assets — Other current liabilities — Interest rate contracts Other assets 10 Other liabilities — Derivatives not designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets 17 Other current liabilities 10 Total fair value of derivative instruments $ 166 $ 16 December 31, 2015 Asset Derivatives Liability Derivatives Balance Sheet Fair Balance Sheet Fair Derivatives designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets $ 85 Other current liabilities $ 1 Foreign exchange forward contracts Other assets 66 Other liabilities 5 Derivatives not designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets 7 Other current liabilities 4 Total fair value of derivative instruments $ 158 $ 10 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 consolidated balance sheets of offsetting our foreign exchange forward contracts and interest rate contracts subject to such provisions: December 31, 2016 Gross Amounts Not Offset in the Consolidated Balance Sheet Description Gross Amounts of Recognized Assets/Liabilities Gross Amounts Offset in the Consolidated Balance Sheet Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet Derivative Financial Instruments Cash Collateral Received (Pledged) Net Amount Derivative assets $ 166 $ — $ 166 $ (16 ) $ — $ 150 Derivative liabilities (16 ) — (16 ) 16 — — December 31, 2015 Gross Amounts Not Offset in the Consolidated Balance Sheet Description Gross Amounts of Recognized Assets/Liabilities Gross Amounts Offset in the Consolidated Balance Sheet Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet Derivative Financial Instruments Cash Collateral Received (Pledged) Net Amount Derivative assets $ 158 $ — $ 158 $ (10 ) $ — $ 148 Derivative liabilities (10 ) — (10 ) 10 — —

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2016
Accrued Liabilities [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consist of the following: December 31, 2016 December 31, 2015 Royalties $ 20 $ 30 Payroll and employee benefits 121 115 Taxes payable 39 12 Rebates payable 70 56 Clinical 64 57 Manufacturing 52 19 Other 142 114 $ 508 $ 403

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt [Abstract]
Debt	Debt On June 22, 2015, Alexion entered into a credit agreement (Credit Agreement) with a syndicate of banks, which provides for a $3,500 term loan facility and a $500 revolving credit facility maturing in five years. Borrowings under the term loan are payable in quarterly installments equal to 1.25% of the original loan amount, beginning December 31, 2015. Final repayment of the term loan and revolving credit loans are due on June 22, 2020. In addition to borrowings in which prior notice is required, the revolving credit facility includes a sublimit of $100 in the form of letters of credit and borrowings on same-day notice, referred to as swingline loans, of up to $25 . Borrowings can be used for working capital requirements, acquisitions and other general corporate purposes. With the consent of the lenders and the administrative agent, and subject to satisfaction of certain conditions, we may increase the term loan facility and/or the revolving credit facility in an amount that does not cause our consolidated net leverage ratio to exceed the maximum allowable amount. Under the Credit Agreement we may elect that the loans under the Credit Agreement bear interest at a rate per annum equal to either a base rate or a Eurodollar rate plus, in each case, an applicable margin. 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 depending upon our consolidated net leverage ratio (as calculated in accordance with the Credit Agreement). At December 31, 2016 , the interest rate on our outstanding loans under the Credit Agreement was 2.52% . Our obligations under the credit facilities are guaranteed by certain of Alexion’s foreign and domestic subsidiaries and secured by liens on certain of Alexion’s and its subsidiaries’ equity interests, subject to certain exceptions. The Credit Agreement requires us to comply with certain financial covenants on a quarterly basis. Under these financial covenants, we are required to deliver to the administrative agent, not later than 50 days after each fiscal quarter, our quarterly financial statements, and within 5 days thereafter, a compliance certificate. In November 2016, we obtained a waiver from the necessary lenders for this requirement and the due date for delivery of the third quarter 2016 financial statements and compliance certificate was extended to January 18, 2017. The posting of the Third Quarter report on Form 10-Q on our website on January 4, 2017 satisfied the financial statement covenant, and we simultaneously delivered the required compliance certificate, as required by the lenders. Further, the Credit Agreement includes negative covenants, subject to exceptions, restricting or limiting our ability and the ability of our subsidiaries to, among other things, incur additional indebtedness, grant liens, and engage in certain investment, acquisition and disposition transactions. The Credit Agreement also contains customary representations and warranties, affirmative covenants and events of default, including payment defaults, breach of representations and warranties, covenant defaults and cross defaults. If an event of default occurs, the interest rate would increase and the administrative agent would be entitled to take various actions, including the acceleration of amounts due under the loan. In connection with entering into the Credit Agreement, we paid $45 in financing costs which are being amortized as interest expense over the life of the debt. Amortization expense associated with deferred financing costs for the years ended December 31, 2016 and 2015 was $10 and $6 , respectively. Amortization expense associated with deferred financing costs for the year ended December 31, 2014 was not material. In connection with the acquisition of Synageva in June 2015, we borrowed $3,500 under the term loan facility and $200 under the revolving facility, and we used our available cash for the remaining cash consideration. We made principal payments of $375 during the year ended December 31, 2016 . At December 31, 2016 , we had $3,081 outstanding on the term loan and zero outstanding on the revolving facility. At December 31, 2016 , we had open letters of credit of $15 , and our borrowing availability under the revolving facility was $485 . The fair value of our long term debt, which is measured using Level 2 inputs, approximates book value. The contractual maturities of our long-term debt obligations due subsequent to December 31, 2016 are as follows: Year 2017 $ — 2018 150 2019 175 2020 2,756 Based upon our intent and ability to make payments during 2017, we included $175 within current liabilities on our consolidated balance sheet as of December 31, 2016 , net of current deferred financing costs.

Facility Lease Obligation

Facility Lease Obligation	12 Months Ended
	Dec. 31, 2016
Leases [Abstract]
Facility Lease Obligation	Facility Lease Obligations New Haven Facility Lease Obligation In November 2012, we entered into a lease agreement for office and laboratory space to be constructed in New Haven, Connecticut. The term of the lease commenced in 2015 and will expire in 2030, with a renewal option of 10 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 sheet. Construction of the new facility was completed and the building was placed into service in the first quarter 2016. The imputed interest rate on this facility lease obligation as of December 31, 2016 was approximately 11% . For the year ended December 31, 2016 and 2015 , we recognized $14 and $5 , respectively, of interest expense associated with this arrangement. As of December 31, 2016 and 2015 , our total facility lease obligation was $136 and $133 , respectively, recorded within other current liabilities and facility lease obligation on our consolidated balance sheets. Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2016 are as follows: Year 2017 $ 16 2018 15 2019 16 2020 16 2021 16 Thereafter 146 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. As of December 31, 2016 and 2015, we recorded a construction-in-process asset of $118 and $19 , respectively, and an offsetting facility lease obligation of $107 and $15 , respectively, associated with the manufacturing facility. Payments to Lonza under the agreement are allocated to the purchases of inventory and the repayment of the facility lease obligation on a relative fair value basis. In 2016 , we incurred $58 of payments to Lonza under this agreement, of which $8 was applied against the outstanding facility lease obligation and $50 was recognized as a prepayment of inventory. See Note 10 for minimum fixed payments due under Lonza agreements.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments License Agreements We have entered into a number of license agreements since our inception in order to advance and obtain technologies and services related to our business. License agreements generally provide for us to pay an initial fee followed by milestone and royalty payments if certain conditions are met. Certain agreements call for future payments upon the attainment of agreed upon development and/or commercial milestones. These agreements may also require minimum royalty payments based on sales of products developed from the applicable technologies, if any. In March 2015 , we entered into an agreement with a third party that allowed us to exercise an option with another third party for exclusive, worldwide, perpetual license rights to a specialized technology and other intellectual property, and we simultaneously exercised the option. Due to the early stage of these assets, we recorded expense for the payments of $47 during the first quarter 2015 . In March 2015 , we entered into a collaboration agreement with a third party that allows us to identify and optimize drug candidates. Alexion will have the exclusive worldwide rights to develop and commercialize products arising from the collaboration. Due to the early stage of the assets we are licensing in connection with the collaboration, we recorded expense for the upfront payment of $15 during the first quarter 2015 . In addition, as of December 31, 2016 , we could be required to pay up to an additional $249 if certain development, regulatory, and commercial milestones are met over time, as well as royalties on commercial sales. In January 2015 , we entered into a license agreement with a third party to obtain an exclusive research, development and commercial license for specific therapeutic molecules. Due to the early stage of these assets, we recorded expense for the upfront payment of $50 during the first quarter 2015 . In addition, we could be required to pay up to an additional $822 if certain development, regulatory, and commercial milestones are met over time, as well as royalties on commercial sales. In December 2014, we entered into an agreement with X-Chem Pharmaceuticals (X-Chem) that allows us to identify novel drug candidates from X-Chem’s proprietary drug discovery engine. Alexion will have the exclusive worldwide rights to develop and commercialize products arising from the collaboration in up to three program targets. Due to the early stage of these assets, we recorded expense for an upfront payment of $8 . In addition, for each program target, for a maximum of three targets, we could be required to make additional payments upon the achievement of specified research, development and regulatory milestones up to $75 , as well as royalties on commercial sales. In January 2014, we entered into an agreement with Moderna Therapeutics, Inc. (Moderna) that allows us to purchase ten product options to develop and commercialize treatments for rare diseases with Moderna’s messenger RNA (mRNA) therapeutics platform. Alexion will lead the discovery, development and commercialization of the treatments produced through this broad, long-term strategic agreement, while Moderna will retain responsibility for the design and manufacture of the messenger RNA against selected targets. Due to the early stage of these assets, we recorded expense for an upfront payment of $100 . We will also be responsible for funding research activities under the program. In addition, for each drug target, up to a maximum of ten targets, we could be required to make an option exercise payment of $15 and to pay up to an additional $120 with respect to a rare disease product and $400 with respect to a non-rare disease product in development and sales milestones if the specific milestones are met over time as well as royalties on commercial sales. Manufacturing Agreements We have various manufacturing development 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 Soliris and Strensiq. We have various agreements with Lonza, with remaining total non-cancellable future commitments of approximately $1,148 . 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 manufactured at Alexion Rhode Island Manufacturing Facility (ARIMF) and a payment with respect to sales of Soliris manufactured at Lonza facilities. In addition to Lonza, we have non-cancellable commitments of $27 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 available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims, 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 in the past 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 U.S. 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, Alexion received a request from the U.S. Department of Justice (DOJ) for the voluntary production of document 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. 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 such loss or range of loss, if any. Several securities class action lawsuits have been filed against the Company and former officers in federal district court alleging violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, 15 U.S.C. § 78j(b), and Rule 10b-5, promulgated thereunder, alleging that defendants made misstatements and/or omissions concerning the Company’s sales of Soliris. On November 17, 2016, a shareholder filed a putative class action in the U.S. District Court for the Southern District of New York. While the litigation was in the early stages, and before defendants had responded to the complaint, on December 30, 2016 plaintiffs filed a notice of voluntary dismissal and dismissed all claims without prejudice. This case is now closed. On December 29, 2016, a second 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 between February 10, 2014 and December 9, 2016. On January 17, 2017, three parties filed motions to be named lead plaintiff in this action. Briefing on these motions is ongoing. The litigation is in the early stages, and defendants have not yet responded to the complaint. Given the early stages of this litigation, management does not currently believe that a loss related to this matter is probable or that the potential magnitude of such loss or range of loss, if any, can be reasonably estimated. 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. Other companies have disclosed similar inquiries. We are cooperating with this inquiry. In March 2013, we received a Warning Letter (Warning Letter) from the FDA regarding compliance with current Good Manufacturing Practices (cGMP) at ARIMF. The Warning Letter followed receipt of a Form 483 Inspectional Observations by the FDA in connection with an FDA inspection that concluded in August 2012. The observations relate to commercial and clinical manufacture of Soliris at ARIMF. We responded to the Warning Letter in a letter to the FDA dated in April 2013. As previously disclosed, the FDA issued Form 483s in August 2014 and August 2015 related to observations at ARIMF and the inspectional observations from the August 2014 and 2015 Forms 483s have since been closed out by the FDA. During July 2016, the FDA completed a routine inspection at ARIMF and have since confirmed receipt of our responses to the inspectional observations included in the Form 483 received during that inspection. The observations are inspectional and do not represent a final FDA determination of compliance. We continue to manufacture products, including Soliris, in this facility. While the resolution of the issues raised in the Warning Letter is difficult to predict, we do not currently believe a loss related to this matter is probable or that the potential magnitude of such loss or range of loss, if any, can be reasonably estimated. Operating Leases As of December 31, 2016 , we have operating leases for office and laboratory space in U.S. and foreign locations to support our operations as a global organization. Aggregate lease expense was $29 , $28 and $23 for the years ended December 31, 2016 , 2015 and 2014 , respectively. Lease expense is being recorded on a straight-line basis over the applicable lease terms. Aggregate future minimum annual rental payments, for the next five years and thereafter under non-cancellable operating leases (including facilities and equipment) as of December 31, 2016 are: Year 2017 $ 21 2018 19 2019 13 2020 7 2021 6 Thereafter 24

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The income tax expense is based on income before income taxes as follows: Year Ended December 31, 2016 2015 2014 U.S. $ (165 ) $ (126 ) $ 222 Non-U.S. 741 624 650 $ 576 $ 498 $ 872 During the fourth quarter of 2013, in connection with the centralization of our global supply chain and technical operations in Ireland, our U.S. parent company became a direct partner in a captive foreign partnership. The partnership income, which is derived in foreign jurisdictions, is classified as “non-U.S. income” for purposes of financial reporting. Substantially all non-U.S. income for the years ended December 31, 2016 and 2015 relates to income from our captive foreign partnership. The components of the income tax expense are as follows: Year Ended December 31, 2016 2015 2014 Domestic Current $ 4 $ (88 ) $ 285 Deferred 107 389 (112 ) 111 301 173 Foreign Current 69 49 82 Deferred (3 ) 4 (40 ) 66 53 42 Total Current 73 (39 ) 367 Deferred 104 393 (152 ) $ 177 $ 354 $ 215 We continue to maintain a valuation allowance against certain deferred tax assets where realization is not certain. We continue to pay cash taxes in U.S. Federal, various U.S. state, and foreign jurisdictions where we have utilized all of our tax attributes or have met the applicable limitation for attribute utilization. At December 31, 2016 , we have tax effected federal and state net operating loss carryforwards of $57 and $5 , respectively. Our NOL’s expire between 2020 and 2036. We also have federal and state income tax credit carryforwards of $536 and $11 , respectively. These income tax credits expire between 2019 and 2036. The provision (benefit) for income taxes differs from the U.S. federal statutory tax rate. The reconciliation of the statutory U.S. federal income tax rate to our effective income tax rate is as follows: Year Ended December 31, 2016 2015 2014 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % State and local income taxes 4.1 % (0.8 )% 0.9 % Foreign income tax rate differential (33.8 )% (32.5 )% (16.5 )% Tax credits, net of nondeductible expenses (6.0 )% (7.6 )% (2.5 )% Foreign income tax credits (8.4 )% (7.6 )% (4.8 )% Foreign income subject to U.S. taxation 26.6 % 24.3 % 15.8 % U.S. deferred taxes on foreign earnings 16.5 % 60.1 % — % Other permanent differences (3.3 )% 0.1 % (3.2 )% Effective income tax rate 30.7 % 71.0 % 24.7 % During the fourth quarter of 2013, in connection with the centralization of our global supply chain and technical operations in Ireland, our U.S. parent company became a direct partner in a captive foreign partnership. Starting in 2014, a significant portion of the non-U.S. income flows through the partnership and the portion of the partnership income that is attributable to our U.S. parent company’s ownership percentage is taxed in the U.S. The remainder of the non-U.S. income is taxed based on the tax rate enacted in the local foreign jurisdictions in which the income is earned. We have operations in many foreign tax jurisdictions, which impose income taxes at different rates than the U.S. The impact of these rate differences is included in the foreign income tax rate differential that we disclose in our reconciliation of the U.S. statutory income tax rate to our effective tax rate. Additionally, included in the foreign income tax rate differential line item is the impact of taxes attributable to intercompany transactions in the amount of approximately $22 , $24 , and $23 of tax expense for 2016 , 2015 , and 2014 , respectively. Provisions have been made for deferred taxes based on the differences between the basis of the assets and liabilities for financial statement purposes and the basis of the assets and liabilities for tax purposes using currently enacted tax rates and regulations that will be in effect when the differences are expected to be recovered or settled. The components of the deferred tax assets and liabilities are as follows: December 31, December 31, 2016 2015 Deferred tax assets: Net operating losses $ 58 $ 168 Income tax credits 537 209 Stock compensation 89 74 Accruals and allowances 91 86 Research and development expenses 15 19 Accrued royalties 23 16 813 572 Valuation allowance (4 ) (5 ) Total deferred tax assets 809 567 Deferred tax liabilities: Depreciable assets (95 ) (83 ) Unrealized gains (44 ) (47 ) Investment in foreign partnership (546 ) (409 ) Intangible assets (502 ) (543 ) Total deferred tax liabilities (1,187 ) (1,082 ) Net deferred tax (liability) asset $ (378 ) $ (515 ) In the second quarter of 2016, we adopted the new share-based compensation guidance. Under the prior guidance, the effect of certain windfall tax benefit deductions were not recognized in deferred tax. The new guidance fully incorporates the deferred tax impact of these deductions. As a result, we recorded an increase to the deferred tax asset for income tax credits for the period ended December 31, 2016. Consistent with this new guidance, deferred tax balances for the period ended December 31, 2015 have not been restated. The decrease in our net operating losses is due to the utilization of historical Synageva net operating loss carryforwards. The increase in income tax credits is primarily attributable to the adoption of new share-based compensation guidance and the corresponding recognition of “windfall” tax benefits. The increase in our investment in foreign partnership deferred tax liability is due to 2016 distributions from our captive foreign partnership. We follow authoritative guidance regarding accounting for uncertainty in income taxes, which prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The interpretation also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosures, and transition. The beginning and ending amounts of unrecognized tax benefits reconciles as follows: 2016 2015 2014 Beginning of period balance $ 114 $ 29 $ 46 Increases for tax positions taken during a prior period 3 2 1 Decreases for tax positions taken during a prior period (1 ) — (2 ) Increases for tax positions taken during the current period 23 85 9 Decreases for tax positions related to settlements — (1 ) (25 ) Decreases for tax positions related to lapse of statute — (1 ) — $ 139 $ 114 $ 29 The total amount of accrued interest and penalties was not significant as of December 31, 2016 . The total amount of tax benefit recorded during 2016 , 2015 , and 2014 which related to unrecognized tax benefits was $22 , $83 , and $17 , respectively. All of our unrecognized tax benefits, if recognized, would have a favorable impact on the effective tax rate. It is reasonably possible that a portion of our unrecognized tax benefits could reverse within the next twelve months. Reversal of these amounts is contingent upon the completion of field audits by the taxing authorities in several jurisdictions, whether a tax adjustment is proposed, the nature and amount of any adjustment, and the administrative path to resolving the proposed adjustment. We cannot reasonably estimate the range of the potential change. We file federal and state income tax returns in the U.S. and in numerous foreign jurisdictions. The U.S. and foreign jurisdictions have statutes of limitations ranging from 3 to 5 years. However, the limitation period could be extended due to our tax attribute carryforward position in a number of our jurisdictions. The tax authorities generally have the ability to review income tax returns for periods where the limitation period has previously expired and can subsequently adjust tax attribute values. The Internal Revenue Service (IRS) has commenced an examination of our U.S. income tax returns for 2013 and 2014. We anticipate this audit will conclude within the next twelve months. As of February 16, 2017 , we have not been notified of any significant proposed adjustments by the IRS. We do not record U.S. tax expense on the undistributed earnings of our controlled foreign corporation (CFC) subsidiaries. We intend to reinvest these earnings permanently outside the U.S. or repatriate the earnings only when it is tax efficient to do so. Accordingly, we believe that U.S. tax on any earnings that might be repatriated would be substantially offset by other tax attributes, such as foreign tax credits or deficits in the foreign earnings and profits account. At December 31, 2016 , the cumulative amount of these earnings was approximately $1,462 . During the fourth quarter of 2013, in connection with the centralization of our global supply chain and technical operations in Ireland, our U.S. parent company became a direct partner in a captive foreign partnership. To the extent that our U.S. parent company receives its allocation of partnership income, the amounts will be taxable in the U.S. each year. The permanent reinvestment assertion is inapplicable to such earnings. We do not have any present or anticipated future need for cash held by our CFCs, as cash generated in the U.S., as well as borrowings, are expected to be sufficient to meet U.S. liquidity needs for the foreseeable future. It is not practicable to estimate the amount of additional taxes which might be payable on our CFCs’ undistributed earnings due to a variety of factors, including the timing, extent and nature of any repatriation. While our expectation is that all foreign undistributed earnings, other than our U.S. parent company’s share of the foreign partnership profits, are permanently invested, there could be certain unforeseen future events that could impact our permanent reinvestment assertion. Such events include acquisitions, corporate restructuring or tax law changes not currently contemplated.

Share-based Compensation

Share-based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation	Share-based Compensation Amended and Restated 2004 Incentive Plan The 2004 Plan was approved by our stockholders in May 2013 and is a broad based plan that provides for the grant of equity awards including restricted stock and restricted stock units (collectively referred to as Restricted Stock), incentive and non-qualified stock options, and other stock-related awards to our directors, officers, key employees and consultants, for up to a maximum of 48 shares. Stock options granted under the 2004 Plan have a maximum contractual term of ten years from the date of grant, have an exercise price not less than the fair value of the stock on the grant date and generally vest over four years. Restricted stock awards also generally vest over four years, with performance-based restricted stock units having a three -year vesting period. Stock Options A summary of the status of our stock option plans at December 31, 2016 , and changes during the year then ended is presented in the table and narrative below: Number of Weighted Weighted Aggregate Intrinsic Outstanding at December 31, 2015 6 $ 110.15 Granted 2 139.71 Exercised (1 ) 55.36 Forfeited and canceled (1 ) 157.80 Outstanding at December 31, 2016 6 $ 116.65 6.02 $ 177 Vested and unvested expected to vest at December 31, 2016 6 $ 116.08 5.97 $ 177 Exercisable at December 31, 2016 4 $ 97.02 4.59 $ 175 Total intrinsic value of stock options exercised during the years ended December 31, 2016 , 2015 and 2014 was $42 , $168 and $460 , respectively. We primarily utilize newly issued shares to satisfy the exercise of stock options. The total fair value of options vested during the years ended December 31, 2016 , 2015 and 2014 was $58 , $51 and $36 , respectively. The fair value of options at the date of grant was estimated using the Black-Scholes model with the following ranges of weighted average assumptions: December 31, December 31, December 31, 2016 2015 2014 Expected life in years 3.82 - 6.29 3.57 - 9.00 3.64 - 5.30 Interest rate 0.87% - 1.66% 0.84% - 2.17% 0.97% - 1.74% Volatility 33.45% - 37.61% 33.35% - 38.13% 32.15% - 34.87% Dividend yield — — — The expected stock price volatility rates are based on historical volatilities of our common stock. The risk-free interest rates are based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option. The average expected life represents the weighted average period of time that options granted are expected to be outstanding. We have evaluated three distinct employee groups in determining the expected life assumptions, and we estimate the expected life of stock options based on historical experience of exercises, cancellations and forfeitures of our stock options. The weighted average fair value at the date of grant for options granted during the years ended December 31, 2016 , 2015 and 2014 was $41.46 , $53.03 and $51.22 per option, respectively. Restricted Stock A summary of the status of our nonvested Restricted Stock and changes during the period then ended is as follows: Number of Shares Weighted Average Grant Date Fair Value Nonvested Restricted Stock at December 31, 2015 2 $ 167.21 Shares granted 2 133.35 Shares forfeited — 165.23 Shares vested (1 ) 155.03 Nonvested Restricted Stock at December 31, 2016 3 $ 149.48 The fair value of restricted stock at the date of grant is based on the fair market value of the shares of common stock underlying the awards on the date of grant. The weighted average fair value at the date of grant for restricted stock awards granted during the years ended December 31, 2016 , 2015 and 2014 , including restricted stock units with performance conditions, was $133.35 , $184.09 and $174.22 per share, respectively. The total weighted average grant date fair value of restricted stock vested during the years ended December 31, 2016 , 2015 and 2014 was $124 , $135 and $41 , respectively. We also grant market-based performance awards to senior management which provide the recipient the right to receive restricted stock at the end of a three year performance period, based on pre-established market-based performance goals. We use payout simulation models to estimate the grant date fair value of the awards. Expense recognized for market-based performance awards was not material for the years ended December 31, 2016 , 2015 and 2014 . Employee Stock Purchase Plan During 2015, the Company adopted the ESPP under which employees can purchase shares of our common stock based on a percentage of their compensation subject to certain limits. The purchase price per share is equal to the lower of 85% of the fair market value of our common stock on the offering date or the purchase date with a six month look-back feature. Under the ESPP, up to 1 shares of common stock may be issued to eligible employees who elect to participate in the purchase plan. Shares issued and compensation expense recognized under the ESPP for the years ended December 31, 2016 and 2015 were not material. Share-Based Compensation Expense The following table summarizes the share-based compensation expense in the consolidated statements of operations: Year Ended December 31, 2016 2015 2014 Cost of sales $ 11 $ 7 $ 4 Research and development 57 64 36 Selling, general and administrative 124 156 74 Total share-based compensation expense 192 227 114 Income tax effect (70 ) (84 ) (42 ) Total share-based compensation expense, net of tax $ 122 $ 143 $ 72 Share-based compensation expense capitalized to inventory during the years ended December 31, 2016 , 2015 and 2014 was $12 , $8 , and $10 , respectively. As of December 31, 2016 , there was $356 of total unrecognized share-based compensation expense related to non-vested share-based compensation arrangements granted under the 2004 Plan. The expense is expected to be recognized over a weighted-average period of 2.71 years.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Common and Preferred Stock [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock In June 2015, in connection with our acquisition of Synageva, we issued 26 shares of common stock to former Synageva stockholders and employees. The fair value of the stock was $4,914 , and we incurred $4 of issuance costs. Share Repurchases In November 2012, our Board of Directors authorized a share repurchase program. The repurchase program does not have an expiration date, and we are not obligated to acquire a particular number of shares. The repurchase program may be discontinued at any time at the Company’s discretion. In May 2015, our Board of Directors increased the authorization to acquire shares with an aggregate value of up to $1,000 for future purchases under the repurchase program, which superseded all prior repurchase programs. Under the program, we repurchased 3 and 2 shares of our common stock at a cost of $430 and $328 during the years ended December 31, 2016 and 2015 , respectively. The Company did not repurchase any shares during the pendency of the Synageva acquisition in the second quarter of 2015 and the Company began repurchasing shares again in the third quarter 2015. In February 2017, our Board of Directors increased the authorization to acquire shares with an aggregate value of up to $1,000 for future purchases under the repurchase program, which superseded all prior repurchase programs. As of February 16, 2017 , there is a total of $1,000 remaining for repurchases under the repurchase program.

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income (Notes)	12 Months Ended
	Dec. 31, 2016
Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract]
Other Comprehensive Income and Accumulated Other Comprehensive Income	Other Comprehensive Income and Accumulated Other Comprehensive Income The following table summarizes the changes in AOCI, by component, for the years ended December 31, 2016 , 2015 and 2014 : Defined Benefit Pension Plans Unrealized Gains (Losses) from Marketable Securities Unrealized Gains (Losses) from Hedging Activities Foreign Currency Translation Adjustment Total Accumulated Other Comprehensive Income (Loss) Balances, December 31, 2013 $ (12 ) $ — $ (4 ) $ (8 ) $ (24 ) Other comprehensive income before reclassifications (6 ) — 110 (6 ) 98 Amounts reclassified from other comprehensive income 1 — (19 ) — (18 ) Net other comprehensive income (loss) (5 ) — 91 (6 ) 80 Balances, December 31, 2014 $ (17 ) $ — $ 87 $ (14 ) $ 56 Other comprehensive income before reclassifications (2 ) (1 ) 111 (6 ) 102 Amounts reclassified from other comprehensive income 9 — (105 ) — (96 ) Net other comprehensive income (loss) 7 (1 ) 6 (6 ) 6 Balances, December 31, 2015 $ (10 ) $ (1 ) $ 93 $ (20 ) $ 62 Other comprehensive income before reclassifications 2 — 46 (4 ) 44 Amounts reclassified from other comprehensive income 1 — (47 ) — (46 ) Net other comprehensive income (loss) 3 — (1 ) (4 ) (2 ) Balances, December 31, 2016 $ (7 ) $ (1 ) $ 92 $ (24 ) $ 60 The table below provides details regarding significant reclassifications from AOCI during the years ended December 31, 2016 , 2015 and 2014 : Details about Accumulated Other Comprehensive Income Components Amount Reclassified From Accumulated Other Comprehensive Income during the year ended December 31, Affected Line Item in the Consolidated Statements of Operations 2016 2015 2014 Unrealized Gains (Losses) on Hedging Activity Effective portion of foreign exchange contracts $ 73 $ 118 $ 19 Net product sales Ineffective portion of foreign exchange contracts — 2 3 Foreign currency gain (loss) 73 120 22 (26 ) (15 ) (3 ) Income tax expense $ 47 $ 105 $ 19 Defined Benefit Pension Items Amortization of prior service costs and actuarial losses $ (1 ) $ (1 ) $ (1 ) (a) Curtailment — (10 ) — (a) (1 ) (11 ) (1 ) — 2 — Income tax expense $ (1 ) $ (9 ) $ (1 ) (a) This AOCI component is included in the computation of net periodic pension benefit cost (see Note 16 for additional details).

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement Authoritative guidance establishes a valuation hierarchy for disclosure of the inputs to the valuation used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. Level 3 inputs are unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value. The following tables present information about our assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2016 and 2015 , and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value. Fair Value Measurement at Balance Sheet Classification Type of Instrument Total Level 1 Level 2 Level 3 Cash equivalents Money market funds $ 266 $ — $ 266 $ — Cash equivalents Commercial paper $ 70 $ — $ 70 $ — Cash equivalents Corporate bonds $ 10 $ — $ 10 $ — Cash equivalents Municipal bonds $ 40 $ — $ 40 $ — Marketable securities Mutual funds $ 13 $ 13 $ — $ — Marketable securities Commercial paper $ 44 $ — $ 44 $ — Marketable securities Corporate bonds $ 113 $ — $ 113 $ — Marketable securities Municipal bonds $ 51 $ — $ 51 $ — Marketable securities Other government-related obligations $ 100 $ — $ 100 $ — Marketable securities Bank certificates of deposit $ 5 $ — $ 5 $ — Marketable securities Equity securities $ 1 $ 1 $ — $ — Prepaid expenses and other current assets Foreign exchange forward contracts $ 97 $ — $ 97 $ — Other assets Foreign exchange forward contracts $ 59 $ — $ 59 $ — Other current liabilities Foreign exchange forward contracts $ 12 $ — $ 12 $ — Other liabilities Foreign exchange forward contracts $ 4 $ — $ 4 $ — Other assets Interest rate contracts $ 10 $ — 10 $ — Current portion of contingent consideration Acquisition-related contingent consideration $ 24 $ — $ — $ 24 Contingent consideration Acquisition-related contingent consideration $ 129 $ — $ — $ 129 Fair Value Measurement at Balance Sheet Classification Type of Instrument Total Level 1 Level 2 Level 3 Cash equivalents Money market funds $ 180 $ — $ 180 $ — Cash equivalents Commercial paper $ 192 $ — $ 192 $ — Cash equivalents Corporate bonds $ 13 $ — $ 13 $ — Cash equivalents Municipal bonds $ 60 $ — $ 60 $ — Cash equivalents Other government-related obligations $ 31 $ — $ 31 $ — Cash equivalents Bank certificates of deposit $ 27 $ — $ 27 $ — Marketable securities Mutual funds $ 9 $ 9 $ — $ — Marketable securities Commercial paper $ 62 $ — $ 62 $ — Marketable securities Corporate bonds $ 120 $ — $ 120 $ — Marketable securities Municipal bonds $ 27 $ — $ 27 $ — Marketable securities Other government-related obligations $ 157 $ — $ 157 $ — Prepaid expenses and other current assets Foreign exchange forward contracts $ 92 $ — $ 92 $ — Other assets Foreign exchange forward contracts $ 66 $ — $ 66 $ — Other current liabilities Foreign exchange forward contracts $ 5 $ — $ 5 $ — Other liabilities Foreign exchange forward contracts $ 5 $ — $ 5 $ — Current portion of contingent consideration Acquisition-related contingent consideration $ 56 $ — $ — $ 56 Contingent consideration Acquisition-related contingent consideration $ 121 $ — $ — $ 121 There were no securities transferred between Level 1, 2 and 3 during the year ended December 31, 2016 . 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 institutional money market funds, commercial paper, municipal bonds, 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 the same or 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 December 31, 2016 , 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 acquisitions, 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 on the acquisition date 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 4.7% for developmental milestones and a weighted average cost of capital ranging from 10% to 21% 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. Estimated future contingent milestone payments related to prior business combinations range from zero if no milestone events are achieved, to a maximum of $766 if all development, regulatory and sales-based milestones are reached. As of December 31, 2016 , the fair value of acquisition-related contingent consideration was $153 . The following table represents a roll-forward of our acquisition-related contingent consideration: December 31, 2016 Balance at beginning of period $ (177 ) Milestone payments 60 Changes in fair value (36 ) Balance at end of period $ (153 ) In the fourth quarter 2016, the criteria was met for the achievement of a milestone payment associated with our acquisition of Enobia Pharma Corp. In connection with this, $60 was paid in December 2016.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans Deferred Compensation Plan We have a nonqualified deferred compensation plan which allows certain highly-compensated employees to make voluntary deferrals of up to 80% of their base salary and incentive bonuses. The plan is designed to work in conjunction with the 401(k) plan and provides for a total combined employer match of up to 6% of an employee’s eligible earnings, up to the IRS annual 401(k) contribution limitations. Deferred compensation amounts under this plan as of December 31, 2016 and 2015 were $13 and $9 , respectively, and are included in other liabilities within the consolidated balance sheets. Employer matching contributions under the plan for the years ended December 31, 2016 , 2015 and 2014 were not material. Defined Contribution Plan We have one qualified 401(k) plan covering all eligible employees. Under the plan, employees may contribute up to the statutory allowable amount for any calendar year. We make matching contributions equal to $1.00 for each dollar contributed up to the first 6% of an individual’s base salary and incentive cash bonus up to the annual IRS maximum. For the years ended December 31, 2016 , 2015 and 2014 , we recorded matching contributions of approximately $17 , $11 , and $9 respectively. Defined Benefit Plans We maintain defined benefit plans for employees in certain countries outside the U.S., including retirement benefit plans required by applicable local law. The plans are valued by independent actuaries using the projected unit credit method. The liabilities correspond to the projected benefit obligations of which the discounted net present value is calculated based on years of employment, expected salary increases, and pension adjustments. In 2015 we recorded the impacts of a curtailment related to our Swiss plan as a result of a reduction of employees due to the relocation of our European headquarters as discussed in Note 17, “Restructuring”. The following table sets forth the funded status and the amounts recognized for defined benefit plans, including the impacts of the 2015 curtailment: December 31, 2016 2015 Change in benefit obligation: Projected benefit obligation, beginning of year $ 45 $ 51 Prior service cost — — Service cost 8 10 Interest cost — 1 Change in assumptions (1 ) 2 Recognized actuarial net loss — 4 Curtailment — (25 ) Plan amendment (4 ) — Foreign currency exchange rate changes (3 ) — Net transfers to (from) plan — 2 Other 3 — Projected benefit obligation, end of year $ 48 $ 45 Accumulated benefit obligation, end of year $ 41 $ 42 December 31, 2016 2015 Change in plan assets: Fair value of plan assets, beginning of year $ 22 $ 27 Return on plan assets — — Employer contributions 3 4 Plan participants' contributions 2 2 Curtailment — (13 ) Foreign currency exchange rate changes (1 ) — Net transfers to (from) plan — 2 Other 2 — Fair value of plan assets, end of year $ 28 $ 22 Funded status at end of year $ (20 ) $ (23 ) The Company measures the fair value of plan assets based on the prices that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The following table presents total plan assets by investment category as of December 31, 2016 and 2015 and the classification of each investment category within the fair value hierarchy with respect to the inputs used to measure fair value: December 31, 2016 December 31, 2015 Fair Value (Level 2) as % of total plan assets Fair Value (Level 2) as % of total plan assets Cash and cash equivalents $ — — % $ — — % Equity security funds 2 7 % 2 9 % Debt security funds 22 79 % 17 77 % Real estate funds 4 14 % 3 14 % $ 28 100 % $ 22 100 % All plan asset investments are classified as Level 2 within the fair value hierarchy and are valued utilizing observable prices for similar instruments and quoted prices for identical or similar instruments in markets that are not active. Plan assets are managed by an independent investment fiduciary and are primarily invested in debt and equity securities and real estate funds in order to maximize the overall return from investment income considering asset allocation limits as determined by pension law. At December 31, 2016 , we have recorded a liability of $20 in other noncurrent liabilities and a charge to accumulated other comprehensive income, net of tax, of $7 related to an additional minimum liability. The following table provides the weighted average assumptions used to calculate net periodic benefit cost and the actuarial present value of projected benefit obligations: December 31, 2016 2015 Weighted average assumptions - Net Periodic Benefit Cost: Discount rate 0.6 % 1.4 % Long term rate of return on assets 3.0 % 3.5 % Rate of compensation increase 1.4 % 1.5 % Weighted average assumptions - Projected Benefit Obligation: Discount Rate 0.7 % 0.6 % Rate of compensation increase 1.4 % 1.4 % The discount rates used to determine the net periodic benefit cost and projected benefit obligation represent the yield on high quality AA-rated corporate bonds for periods that match the duration of the benefit obligations. The expected long-term rate of return on plan assets represents a weighted average of expected returns per asset category. The rate of return considers historical and estimated future risk free rates of return as well as risk premiums for the relevant investment categories. The components of net periodic benefit cost are as follows: Year Ended December 31, 2016 2015 2014 Service cost $ 8 $ 10 $ 8 Interest cost — 1 1 Expected return on plan assets — (1 ) (1 ) Employee contributions (2 ) (2 ) (2 ) Amortization of prior service costs — — — Curtailment — (2 ) — Amortization and deferral of actuarial gain 1 1 1 Total net periodic benefit cost $ 7 $ 7 $ 7 Other changes in plan assets and benefit obligations recognized in AOCI are as follows: Amount included in AOCI - December 31, 2014 $ (17 ) Prior service cost — Net loss arising during the period (4 ) Change in assumptions (2 ) Amortization of net gain 1 Plan assets losses (1 ) Curtailment 10 Foreign currency exchange rate changes — Taxes 3 Amount included in AOCI - December 31, 2015 $ (10 ) Prior service cost — Net loss arising during the period — Plan amendment 4 Change in assumptions 1 Amortization of net gain 1 Plan assets losses — Curtailment — Foreign currency exchange rate changes — Taxes (1 ) Other (2 ) Amount included in AOCI - December 31, 2016 $ (7 ) We estimate that we will pay employer contributions of approximately $3 in 2017 . The expected future benefits to be paid in respect of the pension plans as of December 31, 2016 were as follows: Year 2017 $ 2 2018 1 2019 1 2020 1 2021 1 2022 to 2026 5

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In connection with the completion of our new corporate headquarters located in New Haven, Connecticut, we entered into a lease termination agreement for the previous corporate headquarters located in Cheshire, Connecticut during December 2015. As a result of this action, we recorded restructuring expense of $11 for contract termination costs in the fourth quarter of 2015. In connection with the acquisition and integration of Synageva in 2015, we recorded restructuring expense of $13 primarily related to employee costs during 2015. Synageva restructuring charges were not material in 2016. In the fourth quarter 2014, we announced plans to relocate our European headquarters from Lausanne to Zurich, Switzerland. The relocation of our European headquarters supports our operational needs based on growth in the European region. As a result of this action, we recorded restructuring expenses of $15 related to employee costs in the fourth quarter of 2014. During the years ended December 31, 2016 and 2015 , we incurred additional restructuring costs of $4 and $18 , respectively. The following table presents a reconciliation of the restructuring reserve recorded within accrued expenses on the Company’s consolidated balance sheets for the years ended December 31, 2016 and 2015 , respectively: December 31, 2016 December 31, 2015 Employee Separation Costs Contract Termination Costs Other Costs Total Employee Separation Costs Contract Termination Costs Other Costs Total Liability, beginning of period $ 6 $ 1 $ — $ 7 $ 15 $ — $ — $ 15 Restructuring expenses — 2 1 3 22 12 4 38 Cash settlements (5 ) (4 ) (1 ) (10 ) (35 ) (11 ) (4 ) (50 ) Adjustments to previous estimates (1 ) 1 — — 4 — — 4 Liability, end of period $ — $ — $ — $ — $ 6 $ 1 $ — $ 7

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment Information	Segment Information We operate in a single segment, focusing on serving patients with devastating and ultra-rare disorders through the innovation, development and commercialization of life-transforming therapeutic products. Consistent with our operational structure, our chief operating decision maker manages and allocates resources at a global, consolidated level. Therefore, results of our operations are reported on a consolidated basis for purposes of segment reporting, consistent with our management reporting. Disclosures about net product sales and long-lived assets by geographic area are presented below. Net product sales Net product sales by product are as follows: Year Ended December 31, 2016 2015 2014 Net product sales: Soliris (1) $ 2,843 $ 2,591 $ 2,234 Strensiq 210 12 — Kanuma 29 — — $ 3,082 $ 2,603 $ 2,234 Geographical information Year Ended December 31, Net product sales: 2016 2015 2014 United States $ 1,257 $ 951 $ 730 Europe (1) 961 841 836 Asia Pacific 318 276 244 Rest of World 546 535 424 $ 3,082 $ 2,603 $ 2,234 (1) Included within the Soliris and Europe revenues for 2014 is a reimbursement of $88 for shipments made in years prior to January 1, 2014 as a result of an agreement with the French government. December 31, Long-lived assets (2): 2016 2015 United States $ 490 $ 444 Europe 538 248 Other 8 5 $ 1,036 $ 697 (2) Long-lived assets consist of property, plant and equipment.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Quarterly Financial Information (unaudited) The following condensed quarterly financial information is for the years ended December 31, 2016 and 2015 : March 31 June 30 September 30 December 31 2016: Revenues $ 701 $ 753 $ 799 $ 831 Cost of sales 59 60 71 68 Operating expenses 476 498 549 636 (1) Operating income 166 195 179 127 Net income (loss) $ 92 $ 120 (2) $ 94 $ 93 Earnings (loss) per common share Basic $ 0.41 $ 0.54 (2) $ 0.42 $ 0.41 Diluted $ 0.41 $ 0.53 (2) $ 0.42 $ 0.41 March 31 June 30 September 30 December 31 2015: Revenues $ 600 $ 636 $ 667 $ 701 Cost of sales 69 52 54 58 Operating expenses 427 403 458 546 Operating income 104 181 155 97 Net income (loss) $ 91 $ 170 $ (184 ) (3) $ 67 Earnings (loss) per common share Basic $ 0.46 $ 0.84 $ (0.81 ) $ 0.30 Diluted $ 0.45 $ 0.83 $ (0.81 ) $ 0.29 (1) Included within operating expenses for the fourth quarter of 2016 is an impairment charge of $85 associated with an early stage clinical indefinite-lived intangible asset . (2) Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02 , respectively. (3) Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.

Business Overview and Summary28

Business Overview and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Business Overview and Summary of Significant Accounting Policies [Abstract]
Business	Alexion Pharmaceuticals, Inc. (Alexion, the Company, we, our or us) is a biopharmaceutical company focused on serving patients with devastating and ultra-rare disorders through the innovation, development and commercialization of life-transforming therapeutic products. In our complement franchise, Soliris® is the first and only therapeutic approved for patients with either paroxysmal nocturnal hemoglobinuria (PNH), a life-threatening and ultra-rare genetic blood disorder, or atypical hemolytic uremic syndrome (aHUS), a life-threatening and ultra-rare genetic disease. PNH and aHUS are two disorders resulting from chronic uncontrolled activation of the complement component of the immune system. In our metabolic franchise, we commercialize Strensiq® for the treatment of patients with Hypophosphatasia (HPP) and Kanuma® for the treatment of patients with Lysosomal Acid Lipase Deficiency (LAL-D). HPP is an ultra-rare genetic disease characterized by defective bone mineralization that can lead to deformity of bones and other skeletal abnormalities. LAL-D is a serious, life threatening ultra-rare disease in which genetic mutations result in decreased activity of the Lysosomal Acid Lipase (LAL) enzyme leading to marked accumulation of lipids in vital organs, blood vessels and other tissues. We initiated sales of these products in the third quarter 2015. We are also evaluating additional potential indications for eculizumab in other severe and devastating diseases in which uncontrolled complement activation is the underlying mechanism, and we are progressing in various stages of development with additional product candidates as potential treatments for patients with devastating and ultra-rare disorders. In June 2015, we acquired all of the outstanding shares of common stock of Synageva BioPharma Corp. (Synageva), a publicly-held clinical-stage biotechnology company. The acquisition furthered our objective to develop and commercialize life-transforming therapies for patients with devastating and ultra-rare diseases.
Basis of Presentation and Principles of Consolidation	The accompanying consolidated financial statements include the accounts of Alexion and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. For each of our business combinations, all of the assets acquired and liabilities assumed were recorded at their respective fair values as of the date of acquisition, and their results of operations are included in the consolidated financial statements from the date of acquisition.
Dividend Policy	We have never paid a cash dividend on shares of our stock. We currently intend to retain our earnings to finance future operations and do not anticipate paying any cash dividends on our stock in the foreseeable future.
Critical Accounting Estimates	The preparation of our consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the U.S., requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosure of contingent assets and liabilities in our financial statements. We believe the most complex judgments result primarily from the need to make estimates about the effects of matters that are inherently uncertain and are significant to our consolidated financial statements. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. We evaluate our estimates, judgments and assumptions on an ongoing basis. Actual results may differ from these estimates under different assumptions or conditions. The most significant areas involving estimates, judgments and assumptions used in the preparation of our consolidated financial statements are as follows: • Revenue recognition; • Contingent liabilities; • Inventories; • Share-based compensation; • Valuation of goodwill, acquired intangible assets and in-process research and development (IPR&D); • Valuation of contingent consideration; and • Income taxes.
Foreign Currency Translation	The financial statements of our subsidiaries with functional currencies other than the U.S. dollar are translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates for operating results. Translation gains and losses are included in accumulated other comprehensive income (loss), net of tax, in stockholders’ equity. Foreign currency transaction gains and losses are included in the results of operations in other income and expense.
Cash and Cash Equivalents	Cash and cash equivalents are stated at cost plus accrued interest, which approximates fair value, and include short-term highly liquid investments with original maturities of three months or less.
Fair Value of Financial Instruments	The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, accounts receivable, other assets, accounts payable, accrued expenses and other liabilities approximate fair value due to their short-term maturities. Our marketable securities are valued based upon pricing of securities with similar investment characteristics and holdings. Our derivative financial instruments are measured at fair value using observable market inputs such as forward rates, interest rates, our own credit risk and our counterparties’ credit risks. Our debt obligations are carried at historical cost, which approximates fair value. Our contingent consideration liabilities related to our acquisitions are valued based on various estimates, including probability of success, estimated revenues, discount rates and amount of time until the conditions of the milestone payments are met.
Marketable Securities	We invest our excess cash balances in marketable securities of highly rated financial institutions and investment-grade debt instruments. We seek to diversify our investments and limit the amount of investment concentrations for individual institutions, maturities and investment types. We classify these marketable securities as available-for-sale and, accordingly, record such securities at fair value. We classify these marketable securities as current assets as these investments are intended to be available to the Company for use in funding current operations. Unrealized gains and losses that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If any adjustment to fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our consolidated statement of operations. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive income (loss). We sponsor a nonqualified deferred compensation plan which allows certain highly-compensated employees to elect to defer income to future periods. Participants in the plan earn a return on their deferrals based on several investments options, which mirror returns on underlying mutual fund investments. We choose to invest in the underlying mutual fund investments to offset the liability associated with our nonqualified deferred compensation plan. These securities are classified as trading securities and are carried at fair value with gains and losses included in investment income. The changes in the underlying liability to the employee are recorded in operating expenses.
Accounts Receivable	Our standard credit terms vary based on the country of sale and range from 30 to 120 days. Our consolidated average days’ sales outstanding ranges from 60 to 80 days. 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. For non-interest bearing receivables with an estimated payment beyond one year, we discount the accounts receivable to present value at the date of sale, with a corresponding adjustment to revenue. 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 reasonably assured at the time of sale.
Concentration of Credit Risk	Financial instruments that potentially expose the Company to concentrations of credit risk are limited to cash equivalents, marketable securities, accounts receivable and our foreign exchange derivative contracts. We invest our cash reserves in money market funds or high-quality marketable securities in accordance with our investment policy. The stated objectives of our investment policy is to preserve capital, provide liquidity consistent with forecasted cash flow requirements, maintain appropriate diversification and generate returns relative to these investment objectives and prevailing market conditions. At December 31, 2016 , three customers accounted for 47% of the accounts receivable balance, with these individual customers ranging from 14% to 19% of the accounts receivable balance. At December 31, 2015 , three customers accounted for 51% of the accounts receivable balance, with these individual customers ranging from 14% to 22% of the accounts receivable balance. For the year ended December 31, 2016 , three customers accounted for 37% of our product sales, with these individual customers ranging from 10% to 16% of our product sales. For the year ended December 31, 2015 , three customers accounted for 38% of our product sales, with these individual customers ranging from 10% to 18% of our product sales. No other customers accounted for more than 10% of accounts receivable or net product sales. David Anderson, Alexion’s Executive Vice President and Chief Financial Officer since December 2016, has been a member of the Board of Directors of Cardinal Health, Inc. since April 2014. Cardinal Health, Inc. and its affiliates provide product distribution and other services to Alexion in the United States. As a result of our foreign operations, we are exposed to changes in the general economic conditions in the countries in which we conduct business. Substantially all of our accounts receivable due from these countries are due from or backed by sovereign or local governments, and the amount of non-sovereign accounts receivable is not material. We continue to monitor economic conditions, including volatility associated with international economies and the associated impacts on the financial markets and our business. Although collection of our accounts receivables due from certain countries may extend beyond our standard credit terms, we do not expect any such delays to have a material impact on our financial condition or results of operations.
Inventories	Capitalization of Inventory Costs We capitalize inventory produced for commercial sale, which may include costs incurred for certain products awaiting regulatory approval. We capitalize inventory produced in preparation of product launches sufficient to support estimated initial market demand. Capitalization of such inventory begins when we have (i) obtained positive results in clinical trials that we believe are necessary to support regulatory approval, (ii) concluded that uncertainties regarding regulatory approval have been sufficiently reduced, and (iii) determined that the inventory has probable future economic benefit. In evaluating whether these conditions have been met, we consider clinical trial results for the underlying product candidate, results from meetings with regulatory authorities, and the compilation of the regulatory application. If we are aware of any material risks or contingencies outside of the standard regulatory review and approval process, or if there are any specific negative issues identified relating to the safety, efficacy, manufacturing, marketing or labeling of the product that would have a significant negative impact on its future economic benefits, the related inventory would not be capitalized. We had no inventory capitalized for products awaiting regulatory approval as of December 31, 2016 and 2015 . Products that have been approved by the U.S. Food and Drug Administration (FDA) or other regulatory authorities are also used in clinical programs to assess the safety and efficacy of the products for usage in diseases that have not been approved by the FDA or other regulatory authorities. The form of the products utilized for both commercial and clinical programs is identical and, as a result, the inventory has an “alternative future use” as defined in authoritative guidance. Raw materials and purchased drug product associated with clinical development programs are included in inventory and charged to research and development expense when the product enters the research and development process and no longer can be used for commercial purposes and, therefore, does not have an “alternative future use”. For products which are under development and have not yet been approved by regulatory authorities, purchased drug product is charged to research and development expense upon delivery. Delivery occurs when the inventory passes quality inspection and ownership transfers to us. Nonrefundable advance payments for research and development activities, including production of purchased drug product, are deferred and capitalized until the goods are delivered. We also recognize expense for raw materials purchased for developmental purposes when the raw materials pass quality inspection and we have an obligation to pay for the materials. Inventory Write-Offs We analyze our inventory levels to identify inventory that may expire prior to sale, inventory that has a cost basis in excess of its estimated realizable value, or inventory in excess of expected sales requirements. Although the manufacturing of our product is subject to strict quality control, certain batches or units of product may no longer meet quality specifications or may expire, which requires adjustments to our inventory values. We also apply judgment related to the results of quality tests that we perform throughout the production process, as well as our understanding of regulatory guidelines, to determine if it is probable that inventory will be saleable. These quality tests are performed throughout the pre-and post-production process, and we continually gather additional information regarding product quality for periods after the manufacture date. Our products currently have a maximum estimated life ranging from 36 to 48 months and, based on our sales forecasts, we expect to realize the carrying value of our inventory. In the future, reduced demand, quality issues or excess supply beyond those anticipated by management may result in a material adjustment to inventory levels, which would be recorded as an increase to cost of sales. The determination of whether or not inventory costs will be realizable requires estimates by our management. A critical input in this determination is future expected inventory requirements based on internal sales forecasts. We then compare these requirements to the expiry dates of inventory on hand. For inventories that are capitalized in preparation of product launch, we also consider the expected approval date in assessing realizability. To the extent that inventory is expected to expire prior to being sold, we will write down the value of inventory. Inventories are stated at the lower of cost or estimated realizable value. We determine the cost of inventory on a standard cost basis, which approximates average costs.
Derivative Instruments	We record the fair value of derivative instruments as either assets or liabilities on the balance sheet. The accounting for gains and losses resulting from changes in fair value is dependent on the use of the derivative and whether it is designated and qualifies for hedge accounting. All qualifying hedging activities are documented at the inception of the hedge and must meet the definition of highly effective in offsetting changes to future cash. The effectiveness of the qualifying hedge contract is assessed quarterly. We record the fair value of the qualifying hedges in other current assets, other assets, other current liabilities and other liabilities. Gains or losses resulting from changes in the fair value of qualifying hedges are recorded in other comprehensive income (loss) until the forecasted transaction occurs. When the forecasted transaction occurs, this amount is reclassified into revenue or interest expense, based on the nature of the derivative instrument. Any non-qualifying portion of the gains or losses resulting from changes in fair value, if any, is reported in other income and expense.
Property, Plant and Equipment	Property, plant and equipment are stated at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. We estimate economic lives as follows: • Building and improvements—fifteen to thirty five years • Machinery and laboratory equipment—five to fifteen years • Computer hardware and software—three to seven years • Furniture and office equipment— five to ten years Leasehold improvements and assets under capital lease arrangements are amortized over the lesser of the asset’s estimated useful life or the term of the respective lease. Maintenance costs are expensed as incurred. Construction-in-progress reflects amounts incurred for property, plant, or equipment construction or improvements that have not been placed in service. Manufacturing Facilities We capitalize costs incurred for the construction of facilities which support commercial manufacturing. We also capitalize costs related to validation activities which are directly attributable to preparing the facility for its intended use, including engineering runs and inventory production necessary to obtain approval of the facility from government regulators for the production of a commercially approved drug. When the facility is substantially complete and ready for its intended use and regulatory approval for commercial production has been received, we will place the asset in service. The production of inventory for preparing the facility for its intended use requires two types of production: engineering runs which are used for testing purposes only and do not result in saleable inventory, and validation runs which are used for validating equipment and may result in saleable inventory. The costs associated with inventory produced during engineering runs and normal production losses during validation runs are capitalized to fixed assets and depreciated over the asset’s useful life. Saleable inventory produced during the validation process is initially treated as a fixed asset; however, upon regulatory approval, this inventory is reclassified to inventory and expensed in cost of goods sold as product is sold, or in research and development expenses as product is utilized in R&D activities. Abnormal production costs incurred during the validation process are expensed as incurred.
Acquisitions	Business combinations are accounted for using the acquisition method of accounting. Under the acquisition method of accounting, the tangible and intangible assets acquired and the liabilities assumed are recorded as of the acquisition date at their respective fair values. We evaluate a business as an integrated set of activities and assets that is capable of being managed for the purpose of providing a return in the form of dividends, lower costs or other economic benefits and consists of inputs and processes that provide or have the ability to provide outputs. In an acquisition of a business, the excess of the fair value of the consideration transferred over the fair value of the net assets acquired is recorded as goodwill. In an acquisition of net assets that does not constitute a business, no goodwill is recognized. Our consolidated financial statements include the results of operations of an acquired business after the completion of the acquisition.
Intangible Assets	Our intangible assets consist of licenses, patents, purchased technology and acquired in-process research and development (IPR&D). Intangible assets with definite lives are amortized based on their pattern of economic benefit over their estimated useful lives and reviewed periodically for impairment. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment. If and when development is complete, which generally occurs when regulatory approval to market a product is obtained, the associated assets are deemed finite-lived and are amortized over a period that best reflects the economic benefits provided by these assets.
Goodwill	Goodwill represents the excess of purchase price over fair value of net assets acquired in a business combination and is not amortized. Goodwill is subject to impairment testing at least annually or when a triggering event occurs that could indicate a potential impairment. We are organized and operate as a single reporting unit and therefore the goodwill impairment test is performed using our overall market value, as determined by our traded share price, compared to our book value of net assets.
Impairment of Long-Lived Assets	Our long-lived assets are primarily comprised of intangible assets and property, plant and equipment. We evaluate our finite-lived intangible assets and property, plant and equipment, for impairment whenever events or changes in circumstances indicate the carrying value of an asset or group of assets is not recoverable. If these circumstances exist, recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. In addition, indefinite-lived intangible assets, comprised of IPR&D, are reviewed for impairment annually and whenever events or changes in circumstances indicate that it is more likely than not that the asset is impaired by comparing the fair value to the carrying value of the asset.
Contingent Consideration	We record contingent consideration resulting from a business combination at its fair value on the acquisition date. On a quarterly basis, we revalue these obligations and record increases or decreases in their fair value as an adjustment to operating earnings. Changes to contingent consideration obligations can result from adjustments to discount rates, accretion of the liability due to the passage of time, changes in our estimates of the likelihood or timing of achieving development or commercial milestones, changes in the probability of certain clinical events or changes in the assumed probability associated with regulatory approval.
Contingent liabilities	We are currently involved in various claims and legal proceedings. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, we accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals are based on our best estimates based on available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims, we may reassess the potential liability related to these matters and may revise these estimates.
Treasury Stock	Treasury stock is accounted for using the cost method, with the purchase price of the common stock recorded separately as a deduction from stockholders’ equity.
Revenue Recognition	Our principal source of revenue is product sales. We recognize revenue from product sales when persuasive evidence of an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collection from the customer is reasonably assured, and we have no further performance obligations. Depending on these criteria, revenue is usually recorded upon receipt of the product by the end customer, which is typically a hospital, physician’s office, private or government pharmacy or other healthcare facility. On a regular basis, we review revenue arrangements, such as distributor relationships, to determine whether changes in these criteria have an impact on revenue recognition. Amounts collected from customers and remitted to governmental authorities, such as value-added taxes (VAT) in foreign jurisdictions, are presented on a net basis in our consolidated statements of operations and do not impact net product sales. 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. 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 the lack of contractual return rights, our customers often carry limited inventory. We also monitor inventory within our sales channels to determine whether deferrals are appropriate based on factors such as inventory levels compared to demand, contractual terms, financial strength of distributors and our ability to estimate returns. In some cases, exact quantities of inventory in the channel are not precisely known, requiring us to estimate these amounts. If actual amounts of inventory differ from these estimates, these adjustments could have an impact in the period in which these estimates change. 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. We record estimated rebates payable under governmental programs, including Medicaid in the U.S. and other programs outside the U.S., as a reduction of revenue at the time of product sale. Our calculations related to these rebate accruals require 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. We have entered into volume-based arrangements with governments in certain countries 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 these governments as a rebate. We estimate incremental discounts resulting from these contractual limitations, based on estimated 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. We record distribution and other fees paid to our customers as a reduction of revenue, unless we receive an identifiable and separate benefit for the consideration and we can reasonably estimate the fair value of the benefit 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. We enter into foreign exchange forward contracts to hedge exposures resulting from portions of our forecasted revenues, including intercompany revenues, that are denominated in currencies other than the U.S. dollar. These hedges are designated as cash flow hedges upon inception. We record the effective portion of these cash flow hedges to revenue in the period in which the sale is made to an unrelated third party and the derivative contract is settled.
Research and Development Expenses	Research and development expenses are comprised of costs incurred in performing research and development activities including payroll and benefits, pre-clinical, clinical trial and related clinical manufacturing costs, manufacturing development and scale-up costs, product development and regulatory costs, contract services and other outside contractor costs, research license fees, depreciation and amortization of lab facilities, and lab supplies. These costs are expensed as incurred. We accrue costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the contract research organizations, clinical study sites, laboratories, consultants, or other clinical trial vendors that perform the activities.
Share-Based Compensation	We have two share-based compensation plans pursuant to which awards are currently being made: (i) the Amended and Restated 2004 Incentive Plan (2004 Plan) and (ii) the 2015 Employee Stock Purchase Plan (ESPP). Under the 2004 Plan, restricted stock, restricted stock units, stock options and other stock-related awards may be granted to our directors, officers, employees and consultants or advisors of the Company or any subsidiary. Under the ESPP, eligible employees can purchase shares of common stock at a discount semi-annually through payroll deductions. To date, share-based compensation issued under the plans consists of incentive and non-qualified stock options, restricted stock and restricted stock units, including restricted stock units with market and non-market performance conditions, and shares issued under our ESPP. Compensation expense for our share-based awards is recognized based on the estimated fair value of the awards on the grant date. Compensation expense reflects an estimate of the number of awards expected to vest and is primarily recognized on a straight-line basis over the requisite service period of the individual grants, which typically equals the vesting period. Compensation expense for awards with performance conditions is recognized using the graded-vesting method. Our estimates of employee stock option values rely on estimates of factors we input into the Black-Scholes model. The key factors involve an estimate of future uncertain events. Significant assumptions include the use of historical volatility to determine the expected stock price volatility. We also estimate expected term until exercise and the reduction in the expense from expected forfeitures. We currently use historical exercise and cancellation patterns as our best estimate of future estimated life. For our non-market performance-based awards, we estimate the anticipated achievement of the performance targets, including forecasting the achievement of future financial targets. These estimates are revised periodically based on the probability of achieving the performance targets and adjustments are made throughout the performance period as necessary. We use payout simulation models to estimate the grant date fair value of market performance-based awards. The payout simulation models assume volatility of our common stock and the common stock of a comparator group of companies, as well as correlations of returns of the price of our common stock and the common stock prices of the comparator group. The purchase price of common stock under our ESPP is equal to 85% of the lower of (i) the market value per share of the common stock on the first business day of an offering period or (ii) the market value per share of the common stock on the purchase date. The fair value of the discounted purchases made under our ESPP is calculated using the Black-Scholes model. The fair value of the look-back provision plus the 15% discount is recognized as compensation expense over the 6 month purchase period.
Earnings Per Common Share	We exclude from EPS the weighted-average number of securities whose effect is anti-dilutive. Excluded from the calculation of EPS for the years ended December 31, 2016 , 2015 and 2014 were 4 , 2 , and 1 shares of common stock, respectively, because their effect is anti-dilutive. Basic earnings per common share (EPS) is computed by dividing net income by the weighted-average number of shares of common stock outstanding. For purposes of calculating diluted EPS, the denominator reflects the potential dilution that could occur if stock options, unvested restricted stock units or other contracts to issue common stock were exercised or converted into common stock, using the treasury stock method
Income Taxes	We utilize the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement carrying amounts and tax basis of assets and liabilities using enacted tax rates in effect for years in which the temporary differences are expected to reverse. We periodically evaluate the likelihood of the realization of deferred tax assets and reduce the carrying amount of these deferred tax assets by a valuation allowance when it is more likely than not that deferred tax assets will not be realized. We recognize the benefit of an uncertain tax position that has been taken or we expect to take on income tax returns if such tax position is more likely than not to be sustained. The tax benefit recognized in the financial statements for a particular tax position is based on the largest benefit that is more likely than not to be realized. The amount of unrecognized tax benefits is adjusted, as appropriate, for changes in facts and circumstances, such as significant amendments to existing tax law, new regulations or interpretations by the taxing authorities, or new information obtained during a tax examination or resolution of an examination. We also accrued for potential interest and penalties related to unrecognized tax benefits as a component of tax expense.
Comprehensive Income	Comprehensive income is comprised of net income and other comprehensive income (loss). Other comprehensive income (loss) includes changes in equity that are excluded from net income, such as changes in pension liabilities, unrealized gains and losses on marketable securities, unrealized gains and losses on hedge contracts and foreign currency translation adjustments. Certain of these changes in equity are reflected net of tax.
Other Investments	We invest in companies with securities that are not publicly traded and where fair value is not readily available. Other investments include an investment in the preferred stock of the non-public entity Moderna Therapeutics, Inc. During 2014, we purchased $38 of preferred equity of Moderna. We recorded our investment at cost within other assets in our condensed consolidated balance sheets. We regularly monitor these investments to evaluate whether there has been an other-than-temporary decline in its fair value, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions. The carrying value of these investments was not impaired as of December 31, 2016 .
Reclassification	Certain items in the prior year’s consolidated financial statements have been reclassified to conform to the current presentation.
New Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board (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. The standard also requires enhanced disclosures pertaining to revenue recognition in both interim and annual periods. The standard is effective for interim and annual periods beginning after December 15, 2017 and allows for adoption using a full retrospective method, or a modified retrospective method. Entities may elect to early adopt the standard for annual periods beginning after December 15, 2016. We currently anticipate adopting the standard using the modified retrospective method. We do not expect the implementation of this new standard to have a material impact on our financial position and results of operations. In April 2015, the FASB issued a new standard simplifying the presentation of debt issuance costs. The new standard aligns the treatment of debt issuance costs with debt discounts and premiums and requires debt issuance costs be presented as a direct deduction from the carrying amount of the related debt. We adopted the provisions of this standard in the first quarter 2016 and reclassified $9 of deferred financing costs from prepaid expenses and other current assets to the current portion of long-term debt and $27 from other assets to long-term debt, less current portion in our consolidated balance sheets as of December 31, 2015. In April 2015, the FASB issued a new standard clarifying the accounting for a customer’s fees paid in a cloud computing arrangement. Under this standard, if a cloud computing arrangement includes a software license, the customer would account for the software license consistent with other software licenses. If a cloud computing arrangement does not include a software license, the customer would account for the arrangement as a service contract. We adopted the provisions of this standard in the first quarter 2016. The adoption did not have a material effect on our financial condition or results of operations. In February 2016, the 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 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. We are currently assessing the impact of this standard on our financial condition and results of operations. In March 2016, the FASB issued a new standard intended to simplify certain aspects of the accounting for employee share-based payments. We elected to early adopt this standard during the third quarter of 2016. One aspect of the standard requires an entity to recognize all excess tax benefits and deficiencies associated with stock-based compensation as a reduction or increase to tax expense in the income statement. Previously, such amounts were recognized in additional paid-in capital. This aspect of the new standard was adopted prospectively, and accordingly we recorded tax benefits of $10 , within income tax expense for the year ended December 31, 2016. The amendments require recognition of excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. As a result, $238 associated with previously unrecognized excess tax benefits was recorded as a deferred tax asset and an increase in retained earnings as of the beginning of 2016. Furthermore, the amendment requires that excess tax benefits be classified as an operating activity in the statement of cash flows instead of a financing activity. We elected to adopt this provision of the standard prospectively and thus, prior periods have not been adjusted. We have also elected to continue to estimate the impact of forfeitures when determining the amount of compensation cost to be recognized each period rather than account for forfeitures as they occur. In October 2016 the FASB issued a new standard that eliminates the prohibition of immediate recognition of current and deferred income tax impacts for an intra-entity asset transfer other than inventory. Under the new standard, entities should recognize the income tax consequences on an intra-entity transfer of an asset other than inventory when the transfer occurs. This new standard will be effective for interim periods beginning after December 15, 2017 and requires a modified retrospective adoption through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. We are currently assessing the impact of this standard on our financial condition and results of operations.

Business Overview and Summary29

Business Overview and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Business Overview and Summary of Significant Accounting Policies [Abstract]
Schedule of Inventories	The components of inventory are as follows: December 31, 2016 2015 Raw materials $ 17 $ 18 Work-in-process 143 180 Finished goods 215 92 $ 375 $ 290
Schedule of the Calculation of Basic and Diluted EPS	The following table summarizes the calculation of basic and diluted EPS for years ended December 31, 2016 , 2015 and 2014 : Year Ended December 31, 2016 2015 2014 Net income used for basic and diluted calculation $ 399 $ 144 $ 657 Shares used in computing earnings per common share—basic 224 213 198 Weighted-average effect of dilutive securities: Stock awards 3 3 4 Shares used in computing earnings per common share—diluted 227 216 202 Earnings per common share: Basic $ 1.78 $ 0.68 $ 3.32 Diluted $ 1.76 $ 0.67 $ 3.26

Acquisitions (Tables)

Acquisitions (Tables) - Synageva BioPharma Corp. [Member]	12 Months Ended
	Dec. 31, 2016
Schedule of Purchase Price Allocation	The aggregate consideration to acquire Synageva consisted of: Stock consideration $ 4,918 Cash consideration 4,565 Total purchase price $ 9,483
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table summarizes the estimated fair values of assets acquired and liabilities assumed: Cash $ 626 Inventory 24 In-process research and development (IPR&D) 4,236 Deferred tax liabilities, net (160 ) Other assets and liabilities (26 ) Net assets acquired 4,700 Goodwill 4,783 Total purchase price $ 9,483
Business Acquisition, Pro Forma Information	The following unaudited pro forma information presents the combined results of Alexion and Synageva as if the acquisition of Synageva had been completed on January 1, 2014, with adjustments to give effect to pro forma events that are directly attributable to the acquisition. The unaudited pro forma results do not reflect operating efficiencies or potential cost savings which may result from the consolidation of operations. Accordingly, the unaudited pro forma financial information is not necessarily indicative of the results of operations that would have had we completed the transaction on January 1, 2014. Year Ended December 31, Year Ended December 31, 2015 2014 Pro forma revenues $ 2,606 $ 2,240 Pro forma net income 21 261 Earnings per common share Basic $ 0.09 $ 1.16 Diluted $ 0.09 $ 1.14
Schedule of Acquisition Related Costs [Table Text Block]	Acquisition-related costs associated with our business combinations for the years ended December 31, 2016 , 2015 and 2014 include the following: Year Ended December 31, 2016 2015 2014 Transaction costs (1) $ — $ 27 $ — Integration costs 2 12 — $ 2 $ 39 $ — (1) Transaction costs include investment advisory, legal, and accounting fees

Property, Plant and Equipment31

Property, Plant and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Schedule of Property, Plant and Equipment	A summary of property, plant and equipment is as follows: December 31, 2016 December 31, 2015 Land $ 10 $ 9 Buildings and improvements 450 252 Machinery and laboratory equipment 126 92 Computer hardware and software 123 84 Furniture and office equipment 25 16 Construction-in-progress 495 420 1,229 873 Less: Accumulated depreciation and amortization (193 ) (176 ) $ 1,036 $ 697

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets and Goodwill	Intangible assets and goodwill, net of accumulated amortization, are as follows: December 31, 2016 December 31, 2015 Estimated Cost Accumulated Net Cost Accumulated Net Licenses 6-8 $ 29 $ (29 ) $ — $ 29 $ (29 ) $ — Patents 7 11 (11 ) — 11 (11 ) — Purchased technology 6-16 4,711 (439 ) 4,272 4,709 (117 ) 4,592 Acquired IPR&D Indefinite 31 — 31 116 — 116 Total $ 4,782 $ (479 ) $ 4,303 $ 4,865 $ (157 ) $ 4,708 Goodwill Indefinite $ 5,040 $ (3 ) $ 5,037 $ 5,051 $ (3 ) $ 5,048
Schedule of Goodwill	The following table summarizes the changes in the carrying amount of goodwill: Balance at December 31, 2014 $ 254 Goodwill resulting from the Synageva acquisition 4,794 Balance at December 31, 2015 $ 5,048 Change in goodwill associated with prior acquisition $ (11 ) Balance at December 31, 2016 $ 5,037

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation [Table Text Block]	The amortized cost, gross unrealized holding gains, gross unrealized holding losses and estimated fair value of available-for-sale investments by type of security at December 31, 2016 and December 31, 2015 were as follows: December 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 114 $ — $ — $ 114 Corporate bonds 124 — (1 ) 123 Municipal bonds 91 — — 91 Other government related obligations: U.S. 28 — — 28 Foreign 73 — (1 ) 72 Bank certificates of deposit 5 — — 5 Total available-for-sale debt securities $ 435 $ — $ (2 ) $ 433 Equity securities — 1 — 1 Total available-for-sale securities $ 435 $ 1 $ (2 ) $ 434 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 254 $ — $ — $ 254 Corporate bonds 133 — — 133 Municipal bonds 87 — — 87 Other government related obligations: U.S. 25 — — 25 Foreign 164 — (1 ) 163 Bank certificates of deposit 27 — — 27 Total available-for-sale securities $ 690 $ — $ (1 ) $ 689
Available-for-sale Securities by Balance Sheet Location Classification [Table Text Block]	The fair values of available-for-sale securities by classification in the consolidated balance sheet were as follows: December 31, 2016 December 31, 2015 Cash and cash equivalents $ 120 $ 323 Marketable securities 314 366 $ 434 $ 689
Investments Classified by Contractual Maturity Date [Table Text Block]	The fair values of available-for-sale debt securities at December 31, 2016 , by contractual maturity, are summarized as follows: December 31, 2016 Due in one year or less $ 236 Due after one year through three years 197 Due after three years through five years — $ 433

Derivative Instruments and He34

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities [Abstract]
Schedule of Other Comprehensive Income and Earnings from Foreign Exchange Contracts	The impact on accumulated other comprehensive income (AOCI) and earnings from derivative instruments that qualified as cash flow hedges, for the years ended December 31, 2016 and 2015 were as follows: Year Ended December 31, Foreign Exchange Contracts: 2016 2015 Gain recognized in AOCI, net of tax $ 40 $ 111 Gain reclassified from AOCI to net product sales (effective portion), net of tax $ 47 $ 103 Gain reclassified from AOCI to other income and expense (ineffective portion), net of tax $ — $ 2 Interest Rate Contracts: Gain recognized in AOCI, net of tax $ 6 $ — Gain reclassified from AOCI to interest expense, net of tax $ — $ —
Schedule of Fair Value of Outstanding Derivatives	The following tables summarize the fair value of outstanding derivatives at December 31, 2016 and 2015 : December 31, 2016 Asset Derivatives Liability Derivatives Balance Sheet Fair Balance Sheet Fair Derivatives designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets $ 80 Other current liabilities $ 2 Foreign exchange forward contracts Other assets 59 Other liabilities 4 Interest rate contracts Prepaid expenses and other current assets — Other current liabilities — Interest rate contracts Other assets 10 Other liabilities — Derivatives not designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets 17 Other current liabilities 10 Total fair value of derivative instruments $ 166 $ 16 December 31, 2015 Asset Derivatives Liability Derivatives Balance Sheet Fair Balance Sheet Fair Derivatives designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets $ 85 Other current liabilities $ 1 Foreign exchange forward contracts Other assets 66 Other liabilities 5 Derivatives not designated as hedging instruments: Foreign exchange forward contracts Prepaid expenses and other current assets 7 Other current liabilities 4 Total fair value of derivative instruments $ 158 $ 10
Offsetting Assets and Liabilities [Table Text Block]	The following tables summarize the potential effect on our consolidated balance sheets of offsetting our foreign exchange forward contracts and interest rate contracts subject to such provisions: December 31, 2016 Gross Amounts Not Offset in the Consolidated Balance Sheet Description Gross Amounts of Recognized Assets/Liabilities Gross Amounts Offset in the Consolidated Balance Sheet Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet Derivative Financial Instruments Cash Collateral Received (Pledged) Net Amount Derivative assets $ 166 $ — $ 166 $ (16 ) $ — $ 150 Derivative liabilities (16 ) — (16 ) 16 — — December 31, 2015 Gross Amounts Not Offset in the Consolidated Balance Sheet Description Gross Amounts of Recognized Assets/Liabilities Gross Amounts Offset in the Consolidated Balance Sheet Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheet Derivative Financial Instruments Cash Collateral Received (Pledged) Net Amount Derivative assets $ 158 $ — $ 158 $ (10 ) $ — $ 148 Derivative liabilities (10 ) — (10 ) 10 — —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Accrued Liabilities [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following: December 31, 2016 December 31, 2015 Royalties $ 20 $ 30 Payroll and employee benefits 121 115 Taxes payable 39 12 Rebates payable 70 56 Clinical 64 57 Manufacturing 52 19 Other 142 114 $ 508 $ 403

Debt Debt (Tables)

Debt Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	The contractual maturities of our long-term debt obligations due subsequent to December 31, 2016 are as follows: Year 2017 $ — 2018 150 2019 175 2020 2,756

Facility Lease Obligation (Tabl

Facility Lease Obligation (Tables)	12 Months Ended
	Dec. 31, 2016
Construction in Progress [Member]
Operating Leased Assets [Line Items]
Schedule of Aggregate Future Minimum Annual Rental Payments	Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2016 are as follows: Year 2017 $ 16 2018 15 2019 16 2020 16 2021 16 Thereafter 146

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment, Other Types [Member]
Commitments and Contingencies [Line Items]
Schedule of Aggregate Future Minimum Annual Rental Payments	Aggregate future minimum annual rental payments, for the next five years and thereafter under non-cancellable operating leases (including facilities and equipment) as of December 31, 2016 are: Year 2017 $ 21 2018 19 2019 13 2020 7 2021 6 Thereafter 24
Construction in Progress [Member]
Commitments and Contingencies [Line Items]
Schedule of Aggregate Future Minimum Annual Rental Payments	Aggregate future minimum non-cancellable commitments under the New Haven facility lease obligation, as of December 31, 2016 are as follows: Year 2017 $ 16 2018 15 2019 16 2020 16 2021 16 Thereafter 146

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Income Tax Provision (Benefit) on Income Before Income Taxes	The income tax expense is based on income before income taxes as follows: Year Ended December 31, 2016 2015 2014 U.S. $ (165 ) $ (126 ) $ 222 Non-U.S. 741 624 650 $ 576 $ 498 $ 872
Schedule of Components of Income Tax Provision (Benefit)	The components of the income tax expense are as follows: Year Ended December 31, 2016 2015 2014 Domestic Current $ 4 $ (88 ) $ 285 Deferred 107 389 (112 ) 111 301 173 Foreign Current 69 49 82 Deferred (3 ) 4 (40 ) 66 53 42 Total Current 73 (39 ) 367 Deferred 104 393 (152 ) $ 177 $ 354 $ 215
Reconciliation of the Statutory U.S. Federal Income Tax Rate to Effective Income Tax Rate	The reconciliation of the statutory U.S. federal income tax rate to our effective income tax rate is as follows: Year Ended December 31, 2016 2015 2014 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % State and local income taxes 4.1 % (0.8 )% 0.9 % Foreign income tax rate differential (33.8 )% (32.5 )% (16.5 )% Tax credits, net of nondeductible expenses (6.0 )% (7.6 )% (2.5 )% Foreign income tax credits (8.4 )% (7.6 )% (4.8 )% Foreign income subject to U.S. taxation 26.6 % 24.3 % 15.8 % U.S. deferred taxes on foreign earnings 16.5 % 60.1 % — % Other permanent differences (3.3 )% 0.1 % (3.2 )% Effective income tax rate 30.7 % 71.0 % 24.7 %
Schedule of Components of Deferred Tax Assets and Liabilities	The components of the deferred tax assets and liabilities are as follows: December 31, December 31, 2016 2015 Deferred tax assets: Net operating losses $ 58 $ 168 Income tax credits 537 209 Stock compensation 89 74 Accruals and allowances 91 86 Research and development expenses 15 19 Accrued royalties 23 16 813 572 Valuation allowance (4 ) (5 ) Total deferred tax assets 809 567 Deferred tax liabilities: Depreciable assets (95 ) (83 ) Unrealized gains (44 ) (47 ) Investment in foreign partnership (546 ) (409 ) Intangible assets (502 ) (543 ) Total deferred tax liabilities (1,187 ) (1,082 ) Net deferred tax (liability) asset $ (378 ) $ (515 )
Reconciliation of Unrecognized Tax Benefits	The beginning and ending amounts of unrecognized tax benefits reconciles as follows: 2016 2015 2014 Beginning of period balance $ 114 $ 29 $ 46 Increases for tax positions taken during a prior period 3 2 1 Decreases for tax positions taken during a prior period (1 ) — (2 ) Increases for tax positions taken during the current period 23 85 9 Decreases for tax positions related to settlements — (1 ) (25 ) Decreases for tax positions related to lapse of statute — (1 ) — $ 139 $ 114 $ 29

Share-based Compensation (Table

Share-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation	The following table summarizes the share-based compensation expense in the consolidated statements of operations: Year Ended December 31, 2016 2015 2014 Cost of sales $ 11 $ 7 $ 4 Research and development 57 64 36 Selling, general and administrative 124 156 74 Total share-based compensation expense 192 227 114 Income tax effect (70 ) (84 ) (42 ) Total share-based compensation expense, net of tax $ 122 $ 143 $ 72
Schedule of Share-based Compensation, Stock Options, Activity	A summary of the status of our stock option plans at December 31, 2016 , and changes during the year then ended is presented in the table and narrative below: Number of Weighted Weighted Aggregate Intrinsic Outstanding at December 31, 2015 6 $ 110.15 Granted 2 139.71 Exercised (1 ) 55.36 Forfeited and canceled (1 ) 157.80 Outstanding at December 31, 2016 6 $ 116.65 6.02 $ 177 Vested and unvested expected to vest at December 31, 2016 6 $ 116.08 5.97 $ 177 Exercisable at December 31, 2016 4 $ 97.02 4.59 $ 175
Schedule of Share-based Compensation Valuation Assumptions	The fair value of options at the date of grant was estimated using the Black-Scholes model with the following ranges of weighted average assumptions: December 31, December 31, December 31, 2016 2015 2014 Expected life in years 3.82 - 6.29 3.57 - 9.00 3.64 - 5.30 Interest rate 0.87% - 1.66% 0.84% - 2.17% 0.97% - 1.74% Volatility 33.45% - 37.61% 33.35% - 38.13% 32.15% - 34.87% Dividend yield — — —
Schedule of Share-based Compensation, Restricted Stock Activity	A summary of the status of our nonvested Restricted Stock and changes during the period then ended is as follows: Number of Shares Weighted Average Grant Date Fair Value Nonvested Restricted Stock at December 31, 2015 2 $ 167.21 Shares granted 2 133.35 Shares forfeited — 165.23 Shares vested (1 ) 155.03 Nonvested Restricted Stock at December 31, 2016 3 $ 149.48

Other Comprehensive Income an41

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table summarizes the changes in AOCI, by component, for the years ended December 31, 2016 , 2015 and 2014 : Defined Benefit Pension Plans Unrealized Gains (Losses) from Marketable Securities Unrealized Gains (Losses) from Hedging Activities Foreign Currency Translation Adjustment Total Accumulated Other Comprehensive Income (Loss) Balances, December 31, 2013 $ (12 ) $ — $ (4 ) $ (8 ) $ (24 ) Other comprehensive income before reclassifications (6 ) — 110 (6 ) 98 Amounts reclassified from other comprehensive income 1 — (19 ) — (18 ) Net other comprehensive income (loss) (5 ) — 91 (6 ) 80 Balances, December 31, 2014 $ (17 ) $ — $ 87 $ (14 ) $ 56 Other comprehensive income before reclassifications (2 ) (1 ) 111 (6 ) 102 Amounts reclassified from other comprehensive income 9 — (105 ) — (96 ) Net other comprehensive income (loss) 7 (1 ) 6 (6 ) 6 Balances, December 31, 2015 $ (10 ) $ (1 ) $ 93 $ (20 ) $ 62 Other comprehensive income before reclassifications 2 — 46 (4 ) 44 Amounts reclassified from other comprehensive income 1 — (47 ) — (46 ) Net other comprehensive income (loss) 3 — (1 ) (4 ) (2 ) Balances, December 31, 2016 $ (7 ) $ (1 ) $ 92 $ (24 ) $ 60
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The table below provides details regarding significant reclassifications from AOCI during the years ended December 31, 2016 , 2015 and 2014 : Details about Accumulated Other Comprehensive Income Components Amount Reclassified From Accumulated Other Comprehensive Income during the year ended December 31, Affected Line Item in the Consolidated Statements of Operations 2016 2015 2014 Unrealized Gains (Losses) on Hedging Activity Effective portion of foreign exchange contracts $ 73 $ 118 $ 19 Net product sales Ineffective portion of foreign exchange contracts — 2 3 Foreign currency gain (loss) 73 120 22 (26 ) (15 ) (3 ) Income tax expense $ 47 $ 105 $ 19 Defined Benefit Pension Items Amortization of prior service costs and actuarial losses $ (1 ) $ (1 ) $ (1 ) (a) Curtailment — (10 ) — (a) (1 ) (11 ) (1 ) — 2 — Income tax expense $ (1 ) $ (9 ) $ (1 ) (a) This AOCI component is included in the computation of net periodic pension benefit cost (see Note 16 for additional details).

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule Of Assets And Liabilites Measured At Fair Value	The following tables present information about our assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2016 and 2015 , and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value. Fair Value Measurement at Balance Sheet Classification Type of Instrument Total Level 1 Level 2 Level 3 Cash equivalents Money market funds $ 266 $ — $ 266 $ — Cash equivalents Commercial paper $ 70 $ — $ 70 $ — Cash equivalents Corporate bonds $ 10 $ — $ 10 $ — Cash equivalents Municipal bonds $ 40 $ — $ 40 $ — Marketable securities Mutual funds $ 13 $ 13 $ — $ — Marketable securities Commercial paper $ 44 $ — $ 44 $ — Marketable securities Corporate bonds $ 113 $ — $ 113 $ — Marketable securities Municipal bonds $ 51 $ — $ 51 $ — Marketable securities Other government-related obligations $ 100 $ — $ 100 $ — Marketable securities Bank certificates of deposit $ 5 $ — $ 5 $ — Marketable securities Equity securities $ 1 $ 1 $ — $ — Prepaid expenses and other current assets Foreign exchange forward contracts $ 97 $ — $ 97 $ — Other assets Foreign exchange forward contracts $ 59 $ — $ 59 $ — Other current liabilities Foreign exchange forward contracts $ 12 $ — $ 12 $ — Other liabilities Foreign exchange forward contracts $ 4 $ — $ 4 $ — Other assets Interest rate contracts $ 10 $ — 10 $ — Current portion of contingent consideration Acquisition-related contingent consideration $ 24 $ — $ — $ 24 Contingent consideration Acquisition-related contingent consideration $ 129 $ — $ — $ 129 Fair Value Measurement at Balance Sheet Classification Type of Instrument Total Level 1 Level 2 Level 3 Cash equivalents Money market funds $ 180 $ — $ 180 $ — Cash equivalents Commercial paper $ 192 $ — $ 192 $ — Cash equivalents Corporate bonds $ 13 $ — $ 13 $ — Cash equivalents Municipal bonds $ 60 $ — $ 60 $ — Cash equivalents Other government-related obligations $ 31 $ — $ 31 $ — Cash equivalents Bank certificates of deposit $ 27 $ — $ 27 $ — Marketable securities Mutual funds $ 9 $ 9 $ — $ — Marketable securities Commercial paper $ 62 $ — $ 62 $ — Marketable securities Corporate bonds $ 120 $ — $ 120 $ — Marketable securities Municipal bonds $ 27 $ — $ 27 $ — Marketable securities Other government-related obligations $ 157 $ — $ 157 $ — Prepaid expenses and other current assets Foreign exchange forward contracts $ 92 $ — $ 92 $ — Other assets Foreign exchange forward contracts $ 66 $ — $ 66 $ — Other current liabilities Foreign exchange forward contracts $ 5 $ — $ 5 $ — Other liabilities Foreign exchange forward contracts $ 5 $ — $ 5 $ — Current portion of contingent consideration Acquisition-related contingent consideration $ 56 $ — $ — $ 56 Contingent consideration Acquisition-related contingent consideration $ 121 $ — $ — $ 121
Schedule Of Acquisition-Related Contingent Consideration	The following table represents a roll-forward of our acquisition-related contingent consideration: December 31, 2016 Balance at beginning of period $ (177 ) Milestone payments 60 Changes in fair value (36 ) Balance at end of period $ (153 )

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Schedule of Change in Benefit Obligation	The following table sets forth the funded status and the amounts recognized for defined benefit plans, including the impacts of the 2015 curtailment: December 31, 2016 2015 Change in benefit obligation: Projected benefit obligation, beginning of year $ 45 $ 51 Prior service cost — — Service cost 8 10 Interest cost — 1 Change in assumptions (1 ) 2 Recognized actuarial net loss — 4 Curtailment — (25 ) Plan amendment (4 ) — Foreign currency exchange rate changes (3 ) — Net transfers to (from) plan — 2 Other 3 — Projected benefit obligation, end of year $ 48 $ 45 Accumulated benefit obligation, end of year $ 41 $ 42
Schedule of Change in Plan Assets	December 31, 2016 2015 Change in plan assets: Fair value of plan assets, beginning of year $ 22 $ 27 Return on plan assets — — Employer contributions 3 4 Plan participants' contributions 2 2 Curtailment — (13 ) Foreign currency exchange rate changes (1 ) — Net transfers to (from) plan — 2 Other 2 — Fair value of plan assets, end of year $ 28 $ 22 Funded status at end of year $ (20 ) $ (23 )
Schedule of Fair Value of Plan Assets and Target Asset Allocation	The following table presents total plan assets by investment category as of December 31, 2016 and 2015 and the classification of each investment category within the fair value hierarchy with respect to the inputs used to measure fair value: December 31, 2016 December 31, 2015 Fair Value (Level 2) as % of total plan assets Fair Value (Level 2) as % of total plan assets Cash and cash equivalents $ — — % $ — — % Equity security funds 2 7 % 2 9 % Debt security funds 22 79 % 17 77 % Real estate funds 4 14 % 3 14 % $ 28 100 % $ 22 100 %
Schedule of Weighted Average Assumptions Used to Calculate Net Periodic Benefit Cost and the Actuarial Present Value of Projected Benefit Obligations	The following table provides the weighted average assumptions used to calculate net periodic benefit cost and the actuarial present value of projected benefit obligations: December 31, 2016 2015 Weighted average assumptions - Net Periodic Benefit Cost: Discount rate 0.6 % 1.4 % Long term rate of return on assets 3.0 % 3.5 % Rate of compensation increase 1.4 % 1.5 % Weighted average assumptions - Projected Benefit Obligation: Discount Rate 0.7 % 0.6 % Rate of compensation increase 1.4 % 1.4 %
Schedule of Components of Net Periodic Benefit Costs	The components of net periodic benefit cost are as follows: Year Ended December 31, 2016 2015 2014 Service cost $ 8 $ 10 $ 8 Interest cost — 1 1 Expected return on plan assets — (1 ) (1 ) Employee contributions (2 ) (2 ) (2 ) Amortization of prior service costs — — — Curtailment — (2 ) — Amortization and deferral of actuarial gain 1 1 1 Total net periodic benefit cost $ 7 $ 7 $ 7
Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income	Other changes in plan assets and benefit obligations recognized in AOCI are as follows: Amount included in AOCI - December 31, 2014 $ (17 ) Prior service cost — Net loss arising during the period (4 ) Change in assumptions (2 ) Amortization of net gain 1 Plan assets losses (1 ) Curtailment 10 Foreign currency exchange rate changes — Taxes 3 Amount included in AOCI - December 31, 2015 $ (10 ) Prior service cost — Net loss arising during the period — Plan amendment 4 Change in assumptions 1 Amortization of net gain 1 Plan assets losses — Curtailment — Foreign currency exchange rate changes — Taxes (1 ) Other (2 ) Amount included in AOCI - December 31, 2016 $ (7 )
Schedule of Estimated Future Benefit Payments	The expected future benefits to be paid in respect of the pension plans as of December 31, 2016 were as follows: Year 2017 $ 2 2018 1 2019 1 2020 1 2021 1 2022 to 2026 5

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs [Table Text Block]	The following table presents a reconciliation of the restructuring reserve recorded within accrued expenses on the Company’s consolidated balance sheets for the years ended December 31, 2016 and 2015 , respectively: December 31, 2016 December 31, 2015 Employee Separation Costs Contract Termination Costs Other Costs Total Employee Separation Costs Contract Termination Costs Other Costs Total Liability, beginning of period $ 6 $ 1 $ — $ 7 $ 15 $ — $ — $ 15 Restructuring expenses — 2 1 3 22 12 4 38 Cash settlements (5 ) (4 ) (1 ) (10 ) (35 ) (11 ) (4 ) (50 ) Adjustments to previous estimates (1 ) 1 — — 4 — — 4 Liability, end of period $ — $ — $ — $ — $ 6 $ 1 $ — $ 7

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Revenue from External Customers by Products and Services	Net product sales by product are as follows: Year Ended December 31, 2016 2015 2014 Net product sales: Soliris (1) $ 2,843 $ 2,591 $ 2,234 Strensiq 210 12 — Kanuma 29 — — $ 3,082 $ 2,603 $ 2,234 Geographical information Year Ended December 31, Net product sales: 2016 2015 2014 United States $ 1,257 $ 951 $ 730 Europe (1) 961 841 836 Asia Pacific 318 276 244 Rest of World 546 535 424 $ 3,082 $ 2,603 $ 2,234 (1) Included within the Soliris and Europe revenues for 2014 is a reimbursement of $88 for shipments made in years prior to January 1, 2014 as a result of an agreement with the French government.
Schedule of Revenues and Tangible Long-Lived Assets by Significant Geographic Region	December 31, Long-lived assets (2): 2016 2015 United States $ 490 $ 444 Europe 538 248 Other 8 5 $ 1,036 $ 697 (2) Long-lived assets consist of property, plant and equipment.

Quarterly Financial Informati46

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Condensed Quarterly Financial Information	The following condensed quarterly financial information is for the years ended December 31, 2016 and 2015 : March 31 June 30 September 30 December 31 2016: Revenues $ 701 $ 753 $ 799 $ 831 Cost of sales 59 60 71 68 Operating expenses 476 498 549 636 (1) Operating income 166 195 179 127 Net income (loss) $ 92 $ 120 (2) $ 94 $ 93 Earnings (loss) per common share Basic $ 0.41 $ 0.54 (2) $ 0.42 $ 0.41 Diluted $ 0.41 $ 0.53 (2) $ 0.42 $ 0.41 March 31 June 30 September 30 December 31 2015: Revenues $ 600 $ 636 $ 667 $ 701 Cost of sales 69 52 54 58 Operating expenses 427 403 458 546 Operating income 104 181 155 97 Net income (loss) $ 91 $ 170 $ (184 ) (3) $ 67 Earnings (loss) per common share Basic $ 0.46 $ 0.84 $ (0.81 ) $ 0.30 Diluted $ 0.45 $ 0.83 $ (0.81 ) $ 0.29 (1) Included within operating expenses for the fourth quarter of 2016 is an impairment charge of $85 associated with an early stage clinical indefinite-lived intangible asset . (2) Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02 , respectively. (3) Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.

Business Overview and Summary47

Business Overview and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Inventory, Net		$ 375	$ 290
Impairment of intangible assets		85	0	$ 12
Payments to Acquire Investments		$ 0	0	$ 38
Purchase per share of fair market value of common stock (percent) (lower of)		85.00%
ESPP, discount (percent)		15.00%
Tax benefit resulting from adoption of new share-based compensation guidance	$ 5	$ 10
Adoption of new share-based compensation guidance, value			$ 238
Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Accounts Receivable, Standard Credit Term		30 days
Accounts Receivable, Consolidated Average Term of Sales Outstanding		60 days
Inventory estimated life (in months)		36 months
Minimum [Member] | Building and improvements
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		15 years
Minimum [Member] | Machinery and laboratory equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		5 years
Minimum [Member] | Computer hardware and software
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		3 years
Minimum [Member] | Furniture and office equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		5 years
Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Accounts Receivable, Standard Credit Term		120 days
Accounts Receivable, Consolidated Average Term of Sales Outstanding		80 days
Inventory estimated life (in months)		48 months
Maximum [Member] | Building and improvements
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		35 years
Maximum [Member] | Machinery and laboratory equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		15 years
Maximum [Member] | Computer hardware and software
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		7 years
Maximum [Member] | Furniture and office equipment
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives		10 years
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Accounts Receivable [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		47.00%	51.00%
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Accounts Receivable [Member] | Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		14.00%	14.00%
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Accounts Receivable [Member] | Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		19.00%	22.00%
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Sales Revenue, Product Line [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		37.00%	38.00%
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Sales Revenue, Product Line [Member] | Minimum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		10.00%	10.00%
Customer Concentration Risk [Member] | Three Largest Customers [Member] | Sales Revenue, Product Line [Member] | Maximum [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		16.00%	18.00%
Moderna LLC
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Payments to Acquire Investments		$ 38
Other Current Assets [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Debt Issuance Costs, Net			$ 9
Other Non Current Assets [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Debt Issuance Costs, Net			27
Retained Earnings [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Adoption of new share-based compensation guidance, value			238
Retained Earnings [Member] | Accounting Standards Update 2016-09 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Business Overview And Summary Of Significant Accounting Policies [Line Items]
Adoption of new share-based compensation guidance, value			$ 238

Business Overview and Summary48

Business Overview and Summary of Significant Accounting Policies (Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Business Overview and Summary of Significant Accounting Policies [Abstract]
Inventory, Raw Materials	$ 17	$ 18
Inventory, Work in Process	143	180
Inventory, Finished Goods	215	92
Inventory, Net	$ 375	$ 290

Business Overview and Summary49

Business Overview and Summary of Significant Accounting Policies (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	[1]	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Overview and Summary of Significant Accounting Policies [Abstract]
Net income used for basic calculation	$ 93	$ 94	$ 120		$ 92	$ 67	$ (184)	[2]	$ 170	$ 91	$ 399	$ 144	$ 657
Shares used in computing earnings per common share—basic											224	213	198
Weighted-average effect of dilutive securities:
Stock awards											3	3	4
Shares used in computing earnings per common share—diluted											227	216	202
Earnings per common share
Basic (in dollars per share)	$ 0.41	$ 0.42	$ 0.54		$ 0.41	$ 0.30	$ (0.81)		$ 0.84	$ 0.46	$ 1.78	$ 0.68	$ 3.32
Diluted (in dollars per share)	$ 0.41	$ 0.42	$ 0.53		$ 0.41	$ 0.29	$ (0.81)		$ 0.83	$ 0.45	$ 1.76	$ 0.67	$ 3.26
Antidilutive securities excluded from computation of EPS											4	2	1
[1]	Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02, respectively.
[2]	Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	Jun. 22, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	[1]	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Change in goodwill associated with prior acquisition												$ (11)
Business Combination, Provisional Information [Abstract]
Restructuring expenses												3	$ 38
Contingent consideration arrangements, range of outcomes, value, high		$ 766										766
Contingent consideration arrangements, range of outcomes, value, low		0										0
Contingent consideration		129					$ 121					129	121
Change in fair value of contingent consideration												36	64	$ 20
Deferred tax liabilities		378					515					378	515
Deferred tax liabilities, intangible assets		502					543					502	543
Deferred tax assets, tax credit carryforwards		537					209					537	209
Acquisition-related costs												0	27	0
Payment of contingent consideration												(60)	(50)	0
Net operating losses		58					168					58	168
Net income (loss)		93	$ 94	$ 120		$ 92	67	$ (184)		$ 170	$ 91	399	144	$ 657
Deferred Tax Liabilities, Gross		1,187					1,082					1,187	1,082
Deferred Tax Assets, Net		809					$ 567					809	567
Synageva BioPharma Corp. [Member]
Business Combination, Provisional Information [Abstract]
Restructuring expenses													13
Business acquisition, cash paid	$ 4,565
In-process research and development (IPR&D)	$ 4,236
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized													96
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	26
Inventory	$ 24
Weighted Average Cost of Capital	10.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	$ 160
Deferred Tax Liabilities, Gross	603
Deferred Tax Assets, Net	$ 443
Acquisition Related Contingent Consideration [Member]
Business Combination, Provisional Information [Abstract]
Contingent consideration		$ 153										153
Fair Value, Inputs, Level 3 [Member] | Acquisition Related Contingent Consideration [Member]
Business Combination, Provisional Information [Abstract]
Payment of contingent consideration												$ (60)
Fair Value, Inputs, Level 3 [Member] | Acquisition Related Contingent Consideration [Member] | Minimum [Member]
Business Combination, Provisional Information [Abstract]
Fair Value Inputs, Weighted Average Cost of Capital												10.00%
Fair Value, Inputs, Level 3 [Member] | Acquisition Related Contingent Consideration [Member] | Maximum [Member]
Business Combination, Provisional Information [Abstract]
Fair Value Inputs, Cost of Debt												4.70%
Fair Value Inputs, Weighted Average Cost of Capital												21.00%
Stock Based Compensation Expense [Member]
Business Combination, Provisional Information [Abstract]
Net income (loss)													33
Stock Based Compensation Expense [Member] | Synageva BioPharma Corp. [Member]
Business Combination, Provisional Information [Abstract]
Net income (loss)													127
Acquisition Related and Restructuring Costs [Member]
Business Combination, Provisional Information [Abstract]
Net income (loss)													53
Acquisition Related and Restructuring Costs [Member] | Synageva BioPharma Corp. [Member]
Business Combination, Provisional Information [Abstract]
Net income (loss)													$ 62
[1]	Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02, respectively.
[2]	Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.

Acquisitions (Reconciliation of

Acquisitions (Reconciliation of Upfront Payments To Total Purchase Price) (Details) - Synageva BioPharma Corp. [Member] $ in Millions	Jun. 22, 2015USD ($)
Business Acquisition [Line Items]
Stock consideration	$ 4,918
Cash consideration	4,565
Total purchase price	$ 9,483

Acquisitions (Purchase Price Al

Acquisitions (Purchase Price Allocation To Assets Acquired And Liabilities Assumed) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Jun. 22, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 5,037	$ 5,048		$ 254
Synageva BioPharma Corp. [Member]
Business Acquisition [Line Items]
Cash			$ 626
Inventory			24
In-process research and development (IPR&D)			4,236
Deferred tax liabilities, net			(160)
Other assets and liabilities			(26)
Net assets acquired			4,700
Goodwill			4,783
Total purchase price			$ 9,483

Acquisitions (Pro Forma Financi

Acquisitions (Pro Forma Financial Information Of Combined Results Of Operations) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Pro forma revenues	$ 2,606	$ 2,240
Pro forma net income	$ 21	$ 261
Earnings per common share, Basic	$ 0.09	$ 1.16
Earnings per common share, Diluted	$ 0.09	$ 1.14

Acquisitions (Acquisition Relat

Acquisitions (Acquisition Related Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Transaction costs	$ 0	$ 27	$ 0
Integration costs	2	12	0
Business Combination, Acquisition Related Costs, Including Changes In Fair Value of Contingent Consideration	$ 2	$ 39	$ 0

Property, Plant and Equipment55

Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 30, 2012	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Land			$ 10	$ 9
Buildings and improvements			450	252
Machinery and laboratory equipment			126	92
Computer hardware and software			123	84
Furniture and office equipment			25	16
Construction-in-progress			495	420
Property, Plant and Equipment, Gross			1,229	873
Less: Accumulated depreciation and amortization			(193)	(176)
Property, Plant and Equipment, Net			1,036	697
Depreciation and amortization of property, plant and equipment			396	167	$ 47
Computer software costs			37	20
Computer software, depreciation and amortization expense			12	10	7
Proceeds from development-related grants		$ 26	0	26	0
Property, Plant, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization of property, plant and equipment			64	44	$ 35
CONNECTICUT | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross				227
Government grants, eligibility requirements, period of maintaining headquarters	10 years
Maximum [Member] | CONNECTICUT | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Grants receivable	$ 26
Tax credits on government grants	$ 25
Lonza Group AG [Member] | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross			$ 118	$ 19

Intangible Assets and Goodwil56

Intangible Assets and Goodwill (Schedule of Intangible Assets and Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets [Line Items]
Intangible Assets, Cost	$ 4,782	$ 4,865
Intangible Assets, Accumulated Amortization	479	157
Intangible assets, net	4,303	4,708
Goodwill, Cost	5,040	5,051
Goodwill, Accumulated Amortization	(3)	(3)
Goodwill	5,037	5,048	$ 254
Impairment of intangible assets	85	0	$ 12
Acquired IPRD [Member]
Intangible Assets [Line Items]
Indefinite-lived Intangible Assets, Cost	31	116
Indefinite-Lived Intangible Assets, Accumulated Amortization	0	0
Licensing Agreements [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	29	29
Finite-lived Intangible Assets, Accumulated Amortization	(29)	(29)
Finite-lived Intangible Assets, Net	0	0
Patents [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	11	11
Finite-lived Intangible Assets, Accumulated Amortization	(11)	(11)
Finite-lived Intangible Assets, Net	$ 0	0
Intangible Assets, Estimated Life (months)	7 years
Purchased Technology [Member]
Intangible Assets [Line Items]
Finite-lived Intangible Assets, Cost	$ 4,711	4,709
Finite-lived Intangible Assets, Accumulated Amortization	(439)	(117)
Finite-lived Intangible Assets, Net	$ 4,272	$ 4,592
Minimum [Member] | Licensing Agreements [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	6 years
Minimum [Member] | Purchased Technology [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	6 years
Maximum [Member] | Licensing Agreements [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	8 years
Maximum [Member] | Purchased Technology [Member]
Intangible Assets [Line Items]
Intangible Assets, Estimated Life (months)	16 years

Intangible Assets and Goodwil57

Intangible Assets and Goodwill Narratives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangibles Disclosure [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Year Two	$ 320
Finite-Lived Intangible Assets, Amortization Expense, Year Three	320
Finite-Lived Intangible Assets, Amortization Expense, Year Four	320
Finite-Lived Intangible Assets, Amortization Expense, Year Five	320
Impairment of intangible assets	85	$ 0	$ 12
Amortization of Intangible Assets	322	117	$ 11
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	320
Acquired IPRD [Member]
Goodwill and Intangibles Disclosure [Line Items]
Indefinite-lived intangible assets	$ 31	116
Fair Value, Inputs, Level 3 [Member] | In Process Research and Development [Member]
Goodwill and Intangibles Disclosure [Line Items]
Discount rate	12.00%
Purchased Technology [Member]
Goodwill and Intangibles Disclosure [Line Items]
Finite-Lived Intangible Assets, Net	$ 4,272	$ 4,592

Intangible Assets and Goodwil58

Intangible Assets and Goodwill (Schedule of Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 5,048	$ 254
Goodwill resulting from the Synageva acquisition		4,794
Change in goodwill associated with prior acquisition	(11)
Goodwill, ending balance	$ 5,037	$ 5,048

Marketable Securities (Summary

Marketable Securities (Summary of Avaiable-for-sale Securities Held) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	$ 435
Available-for-sale debt securities, gross unrealized holding gains	0
Available-for-sale debt securities, gross unrealized holding losses	(2)
Available-for-sale debt securities, fair value	433	$ 689
Available-for-sale equity securities, amortized cost	0
Available-for-sale equity securities, gross unrealized holding gains	1
Available-for-sale equity securities, gross unrealized holding losses	0
Available-for-sale equity securities, fair value	1
Available-for-sale securities, amortized cost	435	690
Available-for-sale securities, gross unrealized holding gains	1	0
Available-for-sale securities, gross unrealized holding losses	(2)	(1)
Available-for-sale securities, fair value	434	689
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	114	254
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	0	0
Available-for-sale debt securities, fair value	114	254
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	124	133
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	(1)	0
Available-for-sale debt securities, fair value	123	133
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	91	87
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	0	0
Available-for-sale debt securities, fair value	91	87
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	28	25
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	0	0
Available-for-sale debt securities, fair value	28	25
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	73	164
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	(1)	(1)
Available-for-sale debt securities, fair value	72	163
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, amortized cost	5	27
Available-for-sale debt securities, gross unrealized holding gains	0	0
Available-for-sale debt securities, gross unrealized holding losses	0	0
Available-for-sale debt securities, fair value	$ 5	$ 27

Marketable Securities (Availabl

Marketable Securities (Available-for-sale Securities by Classification in Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	$ 433	$ 689
Available-for-sale Equity Securities, Amortized Cost Basis	0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	0
Available-for-sale Securities, Equity Securities	1
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	120	323
Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	$ 314	$ 366

Marketable Securities (Availa61

Marketable Securities (Available-for-sale Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	$ 236
Available-for-sale Securities, Debt Maturities, Year Two Through Three, Fair Value	197
Available-for-sale Securities, Debt Maturities, Year Four Through Five, Fair Value	0
Available-for-sale Securities, Debt Securities	$ 433	$ 689

Marketable Securities (Narrativ

Marketable Securities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 265	$ 294
Trading Securities	$ 13	$ 9

Derivative Instruments and He63

Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2017
Derivative [Line Items]
Estimated amount to be reclassified from other comprehenisve income in next year	$ 78
Gain in other income and expense	(5)	$ 5	$ 26
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	47	103
Gain reclassified from AOCI to other income and expense (ineffective portion), net of tax	$ 0	2
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign exchange forward contracts durations (months)	60 months
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Foreign exchange forward contracts durations (months)	90 days
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	$ 1,742
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of foreign exchange contracts	647
Senior Secured Term Loan [Member] | Credit Agreement [Member] | Interest Rate Swap One [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount	$ 3,281
Derivative fixed interest rate	0.535%
Senior Secured Term Loan [Member] | Credit Agreement [Member] | Interest Rate Swap Two [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount	$ 656
Derivative fixed interest rate	0.98%
Subsequent Event [Member] | Senior Secured Term Loan [Member] | Credit Agreement [Member] | Interest Rate Swap Three [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount				$ 300
Derivative fixed interest rate				1.29%
Interest Expense [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0

Derivative Instruments and He64

Derivative Instruments and Hedging Activities (Schedule Of Other Comprehensive Income And Earnings From Foreign Exchange Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in AOCI, net of tax	$ 40	$ 111
Gain (loss) reclassified from AOCI to net product sales (Effective portion), net of tax	47	103
Gain (loss) reclassified from AOCI to other income and expense (Ineffective portion), net of tax	0	2
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in AOCI, net of tax	6	0
Interest Expense [Member] | Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) reclassified from AOCI to net product sales (Effective portion), net of tax	$ 0	$ 0

Derivative Instruments and He65

Derivative Instruments and Hedging Activities (Schedule Of Fair Value Of Outstanding Derivatives) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 166	$ 158
Liability Derivatives, Fair Value	16	10
Foreign Exchange Forward [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	2	1
Foreign Exchange Forward [Member] | Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	10	4
Foreign Exchange Forward [Member] | Other Non Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	59	66
Foreign Exchange Forward [Member] | Other Non Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	4	5
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	80	85
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	17	$ 7
Interest Rate Contract [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	0
Interest Rate Contract [Member] | Other Non Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	10
Interest Rate Contract [Member] | Other Non Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	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	$ 0

Derivative Instruments and He66

Derivative Instruments and Hedging Activities (Schedule of Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Offsetting Assets and Liabilities [Line Items]
Asset Derivatives, Fair Value	$ 166	$ 158
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	166	158
Derivative, Collateral, Obligation to Return Securities	(16)	(10)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	150	148
Derivative Liability, Fair Value, Gross Liability	(16)	(10)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	16	10
Derivative, Collateral, Right to Reclaim Securities	16	10
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 0	$ 0

Accrued Expenses (Schedule of A

Accrued Expenses (Schedule of Accrued Expenses) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities [Abstract]
Royalties	$ 20	$ 30
Payroll and employee benefits	121	115
Taxes payable	39	12
Rebates payable	70	56
Clinical	64	57
Manufacturing	52	19
Other	142	114
Accrued expenses	$ 508	$ 403

Debt (Details)

Debt (Details) - USD ($)	Jun. 22, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Amortization of Financing Costs		$ 10,000,000	$ 6,000,000
Proceeds from term loan		0	3,500,000,000	$ 0
Repayments of Long-term Debt		375,000,000	101,000,000	$ 55,000,000
Current portion of long-term debt		$ 167,000,000	166,000,000
Credit Agreement [Member]
Debt Instrument [Line Items]
Debt covenant, maximum financial statement delivery after each fiscal quarter		50 days
Debt covenant, maximum compliance certificate delivery after financial statement delivery		5 days
Payments of Financing Costs			$ 45,000,000
Senior Secured Term Loan [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 3,500,000,000
Debt Instrument, Quarterly Payment, Percentage of Total Borrowings	1.25%
Debt Instrument, Interest Rate at Period End		2.52%
Long-term debt		$ 3,081,000,000
Proceeds from term loan			$ 3,500,000,000
Line of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500,000,000
Line of credit		0
Letters of credit, amount outstanding		15,000,000
Line of credit facility, borrowing availability		485,000,000
Proceeds from term loan			$ 200,000,000
Letter of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Sublimit for letter of credit for working capital requirements and other general corporate purposes	100,000,000
Bridge Loan [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Sublimit for letter of credit for working capital requirements and other general corporate purposes	$ 25,000,000
Eurodollar [Member] | Minimum [Member] | Line of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	1.25%
Eurodollar [Member] | Maximum [Member] | Line of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	2.00%
Base Rate [Member] | Minimum [Member] | Line of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	0.25%
Base Rate [Member] | Maximum [Member] | Line of Credit [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on varaible rate	1.00%
Current Liabilities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 175,000,000

Debt - Schedule of Maturities o

Debt - Schedule of Maturities of Long-term Debt (Details) $ in Millions	Dec. 31, 2016USD ($)
Debt Disclosure [Abstract]
2,017	$ 0
2,018	150
2,019	175
2,020	$ 2,756

Facility Lease Obligation (Deta

Facility Lease Obligation (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2012	Dec. 31, 2016	Dec. 31, 2015
Operating Leased Assets [Line Items]
Facility lease obligation		$ 233	$ 151
Property, Plant and Equipment, Gross		1,229	873
Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		58
Lonza Group AG [Member] | Construction in Progress [Member]
Operating Leased Assets [Line Items]
Property, Plant and Equipment, Gross		118	19
Lonza Group AG [Member] | Facility Lease Obligation [Member]
Operating Leased Assets [Line Items]
Facility lease obligation		107	15
CONNECTICUT | Construction in Progress [Member]
Operating Leased Assets [Line Items]
Facility lease obligation, interest expense		14	5
Property, Plant and Equipment, Gross			227
CONNECTICUT | Facility Lease Obligation [Member]
Operating Leased Assets [Line Items]
Facility lease obligation		136	$ 133
Minimum [Member] | CONNECTICUT | Construction in Progress [Member]
Operating Leased Assets [Line Items]
Operating leases, renewal term	10 years
Facility Lease Obligation [Member] | Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		8
Inventories [Member] | Lonza Group AG [Member]
Operating Leased Assets [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases		$ 50
Facility Lease Obligation | CONNECTICUT | Construction in Progress [Member]
Operating Leased Assets [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		11.00%

Facility Lease Obligation - Agg

Facility Lease Obligation - Aggregate Future Minimum Non-cancellable Commitments Under Facility Lease Obligation (Details) - CONNECTICUT - Construction in Progress [Member] $ in Millions	Dec. 31, 2016USD ($)
Operating Leased Assets [Line Items]
2,017	$ 16
2,018	15
2,019	16
2,020	16
2,021	16
Thereafter	$ 146

Commitments and Contingencies72

Commitments and Contingencies (Narrative) (Details)	1 Months Ended					12 Months Ended
	Mar. 31, 2015USD ($)	Jan. 31, 2015USD ($)	Dec. 31, 2014USD ($)target	Jan. 31, 2014USD ($)target	Nov. 30, 2012USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Commitments and Contingencies [Line Items]
Other Commitment, potential payment						$ 27,000,000
Property, Plant and Equipment, Gross						1,229,000,000	$ 873,000,000
Facility lease obligation						233,000,000	151,000,000
Option to Purchase Drug Products [Member]
Commitments and Contingencies [Line Items]
Research and development, number of drug targets | target				10
Research and development expense, upfront payment				$ 100,000,000
Research and Development Arrangement, Potential Option Exercise Payment						15,000,000
License Agreement 1 [Member]
Commitments and Contingencies [Line Items]
Research and development expense, upfront payment	$ 47,000,000
License Agreement 2 [Member]
Commitments and Contingencies [Line Items]
Research and development expense, upfront payment	$ 15,000,000
Research and development arrangement, potential payment, maximum						249,000,000
License Agreement Three [Member]
Commitments and Contingencies [Line Items]
Research and development expense, upfront payment		$ 50,000,000
Research and development arrangement, potential payment, maximum						822,000,000
Lonza Agreement [Member]
Commitments and Contingencies [Line Items]
Remaining total commitments with Lonza						1,148,000,000
Construction in Progress [Member] | CONNECTICUT
Commitments and Contingencies [Line Items]
Property, Plant and Equipment, Gross							227,000,000
Government grants, eligibility requirements, period of maintaining headquarters					10 years
Construction in Progress [Member] | CONNECTICUT | Minimum [Member]
Commitments and Contingencies [Line Items]
Operating leases, renewal term					10 years
Construction in Progress [Member] | CONNECTICUT | Maximum [Member]
Commitments and Contingencies [Line Items]
Grants receivable					$ 26,000,000
Tax credits on government grants					$ 25,000,000
Property, Plant and Equipment, Other Types [Member]
Commitments and Contingencies [Line Items]
Lease expense						29,000,000	$ 28,000,000	$ 23,000,000
Rare Disease Products [Member] | Option to Purchase Drug Products [Member]
Commitments and Contingencies [Line Items]
Research and development arrangement, potential payment, maximum						120,000,000
Non-Rare Disease Product [Member] | Option to Purchase Drug Products [Member]
Commitments and Contingencies [Line Items]
Research and development arrangement, potential payment, maximum						400,000,000
Licensing Agreements | X-Chem Pharmaceuticals [Member]
Commitments and Contingencies [Line Items]
Research and development, number of drug targets | target			3
Research and development expense, upfront payment			$ 8,000,000
Research and development arrangement, potential payment, maximum						$ 75,000,000

Commitments and Contingencies73

Commitments and Contingencies (Schedule of Aggregate Future Minimum Annual Rental Payments) (Details) $ in Millions	Dec. 31, 2016USD ($)
Property, Plant and Equipment, Other Types [Member]
Operating Leased Assets [Line Items]
2,017	$ 21
2,018	19
2,019	13
2,020	7
2,021	6
Thereafter	24
CONNECTICUT | Construction in Progress [Member]
Operating Leased Assets [Line Items]
2,017	16
2,018	15
2,019	16
2,020	16
2,021	16
Thereafter	$ 146

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Cash paid for income taxes	$ 38	$ 123	$ 91
Income tax expense	177	354	215
Foreign income tax rate differential, intercompany transactions expense (benefit), amount	22	24	23
Change in unrecognized tax benefits	$ 22	$ 83	$ 17
Statute of limitations, minimum (years)	3 years
Statute of limitations, maximum (years)	5 years
Undistributed Earnings of Foreign Subsidiaries	$ 1,462
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	57
Income tax credit carryforwards	536
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	5
Income tax credit carryforwards	$ 11

Income Taxes (Schedule of Incom

Income Taxes (Schedule of Income Tax Provision (Benefit) on Income Before Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S.	$ (165)	$ (126)	$ 222
Non-U.S.	741	624	650
Income before income taxes	$ 576	$ 498	$ 872

Income Taxes (Schedule of Compo

Income Taxes (Schedule of Components of Income Tax Provision (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Domestic
Current	$ 4	$ (88)	$ 285
Deferred	107	389	(112)
Total Domestic	111	301	173
Foreign
Current	69	49	82
Deferred	(3)	4	(40)
Total Foreign	66	53	42
Total
Current	73	(39)	367
Deferred	104	393	(152)
Income Tax Expense (Benefit)	$ 177	$ 354	$ 215

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of the Statutory U.S. Federal Income Tax Rate to Effective Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
State and local income taxes	4.10%	(0.80%)	0.90%
Foreign income tax rate differential	(33.80%)	(32.50%)	(16.50%)
Tax credits, net of nondeductible expenses	(6.00%)	(7.60%)	(2.50%)
Foreign income tax credits	(8.40%)	(7.60%)	(4.80%)
Foreign income subject to U.S. taxation	26.60%	24.30%	15.80%
U.S. deferred taxes on foreign earnings	16.50%	60.10%	0.00%
Other permanent differences	(3.30%)	0.10%	(3.20%)
Effective income tax rate	30.70%	71.00%	24.70%

Income Taxes (Schedule of Com78

Income Taxes (Schedule of Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating losses	$ 58	$ 168
Income tax credits	537	209
Stock compensation	89	74
Accruals and allowances	91	86
Research and development expenses	15	19
Accrued royalties	23	16
Gross deferred tax assets	813	572
Valuation allowance	(4)	(5)
Total deferred tax assets	809	567
Deferred tax liabilities:
Depreciable assets	(95)	(83)
Unrealized gains	(44)	(47)
Investment in foreign partnership	(546)	(409)
Intangible assets	(502)	(543)
Total deferred tax liabilities	(1,187)	(1,082)
Net deferred tax (liability) asset	$ (378)	$ (515)

Income Taxes (Reconciliation 79

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning of period balance	$ 114	$ 29	$ 46
Increases for tax positions taken during a prior period	3	2	1
Decreases for tax positions taken during a prior period	(1)	0	(2)
Increases for tax positions taken during the current period	23	85	9
Decreases for tax positions related to settlements	0	(1)	(25)
Decreases for tax positions related to lapse of statute	0	(1)	0
End of period balance	$ 139	$ 114	$ 29

Share-based Compensation (Narra

Share-based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares authorized	48,000,000
Maximum contractual term under all plans (in years)	10
Total compensation cost not yet recognized on non-vested awards	$ 356
Period for rececognition for compensation cost not yet recognized of non-vested awards	2 years 8 months 16 days
Total intrinsic value of stock options exercised	$ 42	$ 168	$ 460
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value	$ 58	$ 51	$ 36
Weighted average fair value at the date of grant for options granted	$ 41.46	$ 53.03	$ 51.22
Restricted Stock, Grants in Period	2,000,000
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value	$ 133.35
Allocated Share-based Compensation Expense	$ 192	$ 227	$ 114
Purchase per share of fair market value of common stock (percent) (lower of)	85.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	4 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	4 years
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value	$ 133.35	$ 184.09	$ 174.22
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value	$ 124	$ 135	$ 41
Performance-based Restricted Stock Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (in years)	3 years
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares authorized	1,000,000
Inventory [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 12	$ 8	$ 10

Share-based Compensation (Sched

Share-based Compensation (Schedule of Components of Allocated Share-Based Compensation Expense and Capitalization of Share Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 192	$ 227	$ 114
Income tax effect	(70)	(84)	(42)
Total share-based compensation expense, net of tax	122	143	72
Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	11	7	4
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	57	64	36
Selling, General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 124	$ 156	$ 74

Share-based Compensation (Sch82

Share-based Compensation (Schedule of Status of Stock Option Plans) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period, Number of shares | shares	6
Outstanding at beginning of period, Weighted Average Exercise Price | $ / shares	$ 110.15
Granted, Number of shares | shares	2
Granted, Weighted Average Exercise Price | $ / shares	$ 139.71
Exercised, Number of shares | shares	(1)
Exercised, Weighted Average Exercise Price | $ / shares	$ 55.36
Forfeited and cancelled, Number of shares | shares	(1)
Forfeited and cancelled, Weighted Average Exercise Price | $ / shares	$ 157.80
Outstanding at end of period, Number of shares | shares	6
Outstanding at end of period, Weighted Average Exercise Price | $ / shares	$ 116.65
Outstanding at end of period, Weighted Average Remaining Contractual Term (in years)	6 years 7 days
Outstanding at end of period, Aggregate Intrinsic Value | $	$ 177
Vested and unvested expected to vest at end of period, Number of shares | shares	6
Vested and unvested expected to vest at end of period, Weighted Average Exercise Price | $ / shares	$ 116.08
Vested and unvested expected to vest at end of period, Weighted Average Remaining Contractual Term (in years)	5 years 11 months 19 days
Vested and unvested expected to vest at end of period, Aggregate Intrinsic Value | $	$ 177
Exercisable at end of period, Number of shares | shares	4
Exercisable at end of period, Weighted Average Exercise Price | $ / shares	$ 97.02
Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	4 years 7 months 2 days
Exercisable at end of period, Aggregate Intrinsic Value | $	$ 175

Share-based Compensation (Sch83

Share-based Compensation (Schedule of Ranges of Weighted Average Assumptions) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Interest rate, minimum	0.87%	0.84%	0.97%
Interest rate, maximum	1.66%	2.17%	1.74%
Volatility, minimum	33.45%	33.35%	32.15%
Volatility, maximum	37.61%	38.13%	34.87%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years, minimum	3 years 9 months 26 days	3 years 6 months 26 days	3 years 7 months 21 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years, minimum	6 years 3 months 15 days	9 years	5 years 3 months 18 days

Share-based Compensation (Sch84

Share-based Compensation (Schedule of Status of Non-Vested Restricted Stock) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested restricted stock, beginning of period | shares	2
Shares issued | shares	2
Shares cancelled | shares	0
Shares vesting | shares	(1)
Nonvested restricted stock, end of period | shares	3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average grant date fair value | $ / shares	$ 167.21
Restricted Stock, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares	133.35
Cancelled, Weighted average grant date fair value | $ / shares	165.23
Vested, Weighted average grant date fair value | $ / shares	155.03
Weighted average grant date fair value | $ / shares	$ 149.48

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 16, 2017	Feb. 13, 2017	May 06, 2015
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs of $4			$ 4,914
Repurchase of common stock		$ 430	$ 328	$ 303
Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount							$ 1,000
Repurchase of common stock, shares		3	2
Synageva BioPharma Corp. [Member]
Class of Stock [Line Items]
Equity offering issuance costs	$ 4
Subsequent Event [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 1,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount					$ 1,000
Common Stock [Member]
Class of Stock [Line Items]
Issuance of common stock, shares			26
Repurchase of common stock, shares			0
Common Stock [Member] | Synageva BioPharma Corp. [Member]
Class of Stock [Line Items]
Issuance of common stock, shares	26
Additional Paid-In Capital [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs of $4			$ 4,914
Additional Paid-In Capital [Member] | Synageva BioPharma Corp. [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs of $4	$ 4,914

Other Comprehensive Income an86

Other Comprehensive Income and Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	$ 62	$ 56	$ (24)
Other Comprehensive Income before Reclassifications	44	102	98
Amounts reclassified from other comprehensive income	(46)	(96)	(18)
Other comprehensive (loss) income, net of tax	(2)	6	80
Accumulated comprehensive income (loss), Ending balance	60	62	56
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(10)	(17)	(12)
Other Comprehensive Income before Reclassifications	2	(2)	(6)
Amounts reclassified from other comprehensive income	1	9	1
Other comprehensive (loss) income, net of tax	3	7	(5)
Accumulated comprehensive income (loss), Ending balance	(7)	(10)	(17)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(1)	0	0
Other Comprehensive Income before Reclassifications	0	(1)	0
Amounts reclassified from other comprehensive income	0	0	0
Other comprehensive (loss) income, net of tax	0	(1)	0
Accumulated comprehensive income (loss), Ending balance	(1)	(1)	0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	93	87	(4)
Other Comprehensive Income before Reclassifications	46	111	110
Amounts reclassified from other comprehensive income	(47)	(105)	(19)
Other comprehensive (loss) income, net of tax	(1)	6	91
Accumulated comprehensive income (loss), Ending balance	92	93	87
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated comprehensive income (loss), Beginning balance	(20)	(14)	(8)
Other Comprehensive Income before Reclassifications	(4)	(6)	(6)
Amounts reclassified from other comprehensive income	0	0	0
Other comprehensive (loss) income, net of tax	(4)	(6)	(6)
Accumulated comprehensive income (loss), Ending balance	$ (24)	$ (20)	$ (14)

Other Comprehensive Income an87

Other Comprehensive Income and Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	[1]	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net product sales												$ 3,082	$ 2,603	$ 2,234
Foreign currency gain (loss)												(5)	1	(2)
Investment income												11	8	8
Curtailment												0	10
Income before income taxes												576	498	872
Income tax expense												(177)	(354)	(215)
Net income		$ 93	$ 94	$ 120		$ 92	$ 67	$ (184)		$ 170	$ 91	399	144	657
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net product sales												73	118	19
Foreign currency gain (loss)												0	2	3
Income before income taxes												73	120	22
Income tax expense												(26)	(15)	(3)
Net income												47	105	19
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service costs and actuarial losses	[3]											(1)	(1)	(1)
Curtailment	[3]											0	(10)	0
Income before income taxes												(1)	(11)	(1)
Income tax expense												0	2	0
Net income												$ (1)	$ (9)	$ (1)
[1]	Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02, respectively.
[2]	Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.
[3]	This AOCI component is included in the computation of net periodic pension benefit cost (see Note 16 for additional details).

Fair Value Measurement (Schedul

Fair Value Measurement (Schedule Of Assets And Liabilites Measured At Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 129	$ 121
Payment for Contingent Consideration	60	50	$ 0
Acquisition Related Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	153
Acquisition Related Contingent Consideration [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payment for Contingent Consideration	60
Cash Equivalents [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	10	13
Cash Equivalents [Member] | Corporate Bond Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Corporate Bond Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	10	13
Cash Equivalents [Member] | Corporate Bond Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Institutional Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	266	180
Cash Equivalents [Member] | Institutional Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Institutional Money Market Funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	266	180
Cash Equivalents [Member] | Institutional Money Market Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	70	192
Cash Equivalents [Member] | Commercial Paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	70	192
Cash Equivalents [Member] | Commercial Paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	40	60
Cash Equivalents [Member] | Municipal Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Municipal Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	40	60
Cash Equivalents [Member] | Municipal Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Cash Equivalents [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Cash Equivalents [Member] | Other Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		31
Cash Equivalents [Member] | Other Government Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Cash Equivalents [Member] | Other Government Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		31
Cash Equivalents [Member] | Other Government Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Marketable Securities [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	113	120
Marketable Securities [Member] | Corporate Bond Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Corporate Bond Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	113	120
Marketable Securities [Member] | Corporate Bond Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	44	62
Marketable Securities [Member] | Commercial Paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	44	62
Marketable Securities [Member] | Commercial Paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	51	27
Marketable Securities [Member] | Municipal Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Municipal Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	51	27
Marketable Securities [Member] | Municipal Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	5
Marketable Securities [Member] | Certificates of Deposit [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Marketable Securities [Member] | Certificates of Deposit [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	5
Marketable Securities [Member] | Certificates of Deposit [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Marketable Securities [Member] | Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	13	9
Marketable Securities [Member] | Mutual Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	13	9
Marketable Securities [Member] | Mutual Funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Mutual Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Other Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	100	157
Marketable Securities [Member] | Other Government Obligations [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Other Government Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	100	157
Marketable Securities [Member] | Other Government Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Marketable Securities [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	1
Marketable Securities [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	1
Marketable Securities [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Marketable Securities [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Other Non Current Assets [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	10
Other Non Current Assets [Member] | Interest Rate Contract [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
Other Non Current Assets [Member] | Interest Rate Contract [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	10
Other Non Current Assets [Member] | Interest Rate Contract [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
Other Non Current Assets [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	59	66
Other Non Current Assets [Member] | Foreign Exchange Forward [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0	0
Other Non Current Assets [Member] | Foreign Exchange Forward [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	59	66
Other Non Current Assets [Member] | Foreign Exchange Forward [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0	0
Currentportionofcontingentconsideration [Member] | Acquisition Related Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	24	56
Currentportionofcontingentconsideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0
Currentportionofcontingentconsideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0
Currentportionofcontingentconsideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	24	56
Other Current Liabilities [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	12	5
Other Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0	0
Other Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	12	5
Other Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0	0
Other Non Current Liabilities [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	4	5
Other Non Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0	0
Other Non Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	4	5
Other Non Current Liabilities [Member] | Foreign Exchange Forward [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, liability	0	0
Prepaid Expenses and Other Current Assets [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	97	92
Prepaid Expenses and Other Current Assets [Member] | Foreign Exchange Forward [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0	0
Prepaid Expenses and Other Current Assets [Member] | Foreign Exchange Forward [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	97	92
Prepaid Expenses and Other Current Assets [Member] | Foreign Exchange Forward [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign exchange forward contracts, asset	0	0
Contingent Consideration [Member] | Acquisition Related Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	129	121
Contingent Consideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0
Contingent Consideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0
Contingent Consideration [Member] | Acquisition Related Contingent Consideration [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 129	$ 121

Fair Value Measurement (Sched89

Fair Value Measurement (Schedule Of Acquisition-Related Contingent Consideration) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration arrangements, range of outcomes, value, low	$ 0
Contingent consideration arrangements, range of outcomes, value, high	766
Contingent consideration	129	$ 121
Acquisition-Related Contingent Consideration [Roll Forward]
Milestone payments	60	50	$ 0
Acquisition Related Contingent Consideration [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration	153
Acquisition Related Contingent Consideration [Member] | Level 3 [Member]
Acquisition-Related Contingent Consideration [Roll Forward]
Balance at beginning of period	(177)
Milestone payments	60
Changes in fair value	(36)
Balance at end of period	$ (153)	$ (177)
Acquisition Related Contingent Consideration [Member] | Minimum [Member] | Level 3 [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Weighted Average Cost of Capital	10.00%
Acquisition Related Contingent Consideration [Member] | Maximum [Member] | Level 3 [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Cost of Debt	4.70%
Fair Value Inputs, Weighted Average Cost of Capital	21.00%

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Deferred Compensation Arrangement with Individual, Voluntary Deferrals, Percent of Employees' Gross Pay, Maximum	80.00%
Deferred Compensation Arrangement with Individual, Employer Matching Contribution, Percent of Match	6.00%
Amount of each dollar matching contributed up to first six percent of individual base salary and incentive cash bonus	$ 1
Percentage of contribution of individual's base salary and incentive cash bonus	6.00%
Defined benefit plan, contributions by employer	$ 17,000,000	$ 11,000,000	$ 9,000,000
Additional minimum liability recorded in other non-current liabiliites	20,000,000
Additional minimum liability charged against other comprehensive income	7,000,000
Estimated future employer contributions in next fiscal year	3,000,000
Other Liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation liability	$ 13,000,000	$ 9,000,000

Employee Benefit Plans (Schedul

Employee Benefit Plans (Schedule of Change in Benefit Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation, beginning of year	$ 45	$ 51
Prior service cost	0	0
Service cost	8	10	$ 8
Interest cost	0	1	1
Change in assumptions	(1)	2
Recognized actuarial net loss	0	4
Curtailment	0	(25)
Plan amendment	(4)	0
Foreign currency exchange rate changes	(3)	0
Net transfers to (from) plan	0	2
Other	3	0
Projected benefit obligation, end of year	48	45	$ 51
Accumulated benefit obligation, end of year	$ 41	$ 42

Employee Benefit Plans (Sched92

Employee Benefit Plans (Schedule of Change in Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in plan assets:
Fair value of plan assets, beginning of year	$ 22	$ 27
Return on plan assets	0	0
Employer contributions	3	4
Plan participants' contributions	2	2	$ 2
Curtailment	0	(13)
Foreign currency exchange rate changes	(1)	0
Net transfers to (from) plan	0	2
Other	2	0
Fair value of plan assets, end of year	28	22	$ 27
Funded status at end of year	$ (20)	$ (23)

Employee Benefit Plans (Sched93

Employee Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 28	$ 22	$ 27
Actual plan asset allocations	100.00%	100.00%
Fair Value (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 28	$ 22
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	0.00%	0.00%
Cash and Cash Equivalents [Member] | Fair Value (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 0	$ 0
Equity Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	7.00%	9.00%
Equity Security Funds [Member] | Fair Value (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 2	$ 2
Debt Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	79.00%	77.00%
Debt Security Funds [Member] | Fair Value (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 22	$ 17
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocations	14.00%	14.00%
Real Estate Funds [Member] | Fair Value (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, end of year	$ 4	$ 3
Minimum [Member] | Cash and Notes Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	0.00%
Minimum [Member] | Equity Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	30.00%
Minimum [Member] | Debt Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	16.00%
Minimum [Member] | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	10.00%
Minimum [Member] | Other Investments or Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	0.00%
Maximum [Member] | Cash and Notes Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	10.00%
Maximum [Member] | Equity Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	60.00%
Maximum [Member] | Debt Security Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	45.00%
Maximum [Member] | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	20.00%
Maximum [Member] | Other Investments or Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	12.00%

Employee Benefit Plans (Sched94

Employee Benefit Plans (Schedule of Weighted Average Assumptions Used to Calculate Net Periodic Benefit Cost and the Actuarial Present Value of Projected Benefit Obligations) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Weighted average assumptions - Net Periodic Benefit Cost:
Discount rate	0.60%	1.40%
Long term rate of return on assets	3.00%	3.50%
Rate of compensation increase	1.40%	1.50%
Weighted average assumptions - Projected Benefit Obligation:
Discount Rate	0.70%	0.60%
Rate of compensation increase	1.40%	1.40%

Employee Benefit Plans (Sched95

Employee Benefit Plans (Schedule of Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 8	$ 10	$ 8
Interest cost	0	1	1
Expected return on plan assets	0	(1)	(1)
Employee contributions	(2)	(2)	(2)
Amortization of prior service costs	0	0	0
Curtailment	0	(2)	0
Amortization and deferral of actuarial gain	1	1	1
Total net periodic benefit cost	$ 7	$ 7	$ 7

Employee Benefit Plans (Sched96

Employee Benefit Plans (Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Roll Forward]
Amount included in AOCI - Beginning of year	$ (10)	$ (17)
Prior service cost	0	0
Net gain (loss) arising during the period	0	(4)
Plan amendment	4
Change in assumptions	1	(2)
Amortization of net gain (loss)	1	1
Plan assets losses	0	(1)
Curtailment	0	10
Foreign currency exchange rate changes	0	0
Taxes	(1)	3
Other	(2)
Amount included in AOCI - End of year	$ (7)	$ (10)

Employee Benefit Plans (Sched97

Employee Benefit Plans (Schedule of Estimated Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2016USD ($)
Compensation and Retirement Disclosure [Abstract]
2,017	$ 2
2,018	1
2,019	1
2,020	1
2,021	1
2022 to 2026	$ 5

Restructuring (Details)

Restructuring (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring expenses			$ 3	$ 38
Synageva BioPharma Corp. [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses				13
Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses			2	12
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses			0	22
Corporate Headquarter Relocation Plan [Member] | Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 11
Relocation of European Headquarters [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Period Increase (Decrease)			$ 4	$ 18
Relocation of European Headquarters [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		$ 15

Restructuring - Reconciliation

Restructuring - Reconciliation of Restructuring Reserve (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Liability, beginning of period	$ 7	$ 15
Restructuring expenses	3	38
Cash settlements	(10)	(50)
Adjustments to previous estimates	0	4
Liability, end of period	0	7
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period	6	15
Restructuring expenses	0	22
Cash settlements	(5)	(35)
Adjustments to previous estimates	(1)	4
Liability, end of period	0	6
Contract Termination [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period	1	0
Restructuring expenses	2	12
Cash settlements	(4)	(11)
Adjustments to previous estimates	1	0
Liability, end of period	0	1
Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Liability, beginning of period	0	0
Restructuring expenses	1	4
Cash settlements	(1)	(4)
Adjustments to previous estimates	0	0
Liability, end of period	$ 0	$ 0

Segment Information - Net Produ

Segment Information - Net Product Sales (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue from External Customer [Line Items]
Revenues		$ 3,082	$ 2,603	$ 2,234
Soliris
Revenue from External Customer [Line Items]
Revenues	[1]	2,843	2,591	2,234
Strensiq
Revenue from External Customer [Line Items]
Revenues		210	12	0
Kanuma
Revenue from External Customer [Line Items]
Revenues		$ 29	$ 0	$ 0
[1]	Included within the Soliris and Europe revenues for 2014 is a reimbursement of $88 for shipments made in years prior to January 1, 2014 as a result of an agreement with the French government.

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues		$ 3,082	$ 2,603	$ 2,234
Long-lived assets	[1]	1,036	697
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues		1,257	951	730
Long-lived assets	[1]	490	444
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	[2]	961	841	836
Long-lived assets	[1]	538	248
Asia Pacific (primarily Japan) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues		318	276	244
Rest of World [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues		546	535	424
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	[1]	8	5
Soliris
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	[2]	$ 2,843	$ 2,591	2,234
Soliris | FRANCE
Revenues from External Customers and Long-Lived Assets [Line Items]
Reimbursement Revenue				$ 88
[1]	Long-lived assets consist of property, plant and equipment.
[2]	Included within the Soliris and Europe revenues for 2014 is a reimbursement of $88 for shipments made in years prior to January 1, 2014 as a result of an agreement with the French government.

Quarterly Financial Informat102

Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016		Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information [Line Items]
Revenues	$ 831		$ 799	$ 753		$ 701	$ 701	$ 667		$ 636	$ 600	$ 3,084	$ 2,604	$ 2,234
Cost of sales	68		71	60		59	58	54		52	69	258	233	174
Operating expenses	636	[1]	549	498		476	546	458		403	427	2,159	1,834	1,191
Operating income	127		179	195		166	97	155		181	104	667	537	869
Net income (loss)	$ 93		$ 94	$ 120	[2]	$ 92	$ 67	$ (184)	[3]	$ 170	$ 91	$ 399	$ 144	$ 657
Earnings per common share
Basic (in dollars per share)	$ 0.41		$ 0.42	$ 0.54	[2]	$ 0.41	$ 0.30	$ (0.81)		$ 0.84	$ 0.46	$ 1.78	$ 0.68	$ 3.32
Diluted (in dollars per share)	$ 0.41		$ 0.42	$ 0.53	[2]	$ 0.41	$ 0.29	$ (0.81)		$ 0.83	$ 0.45	$ 1.76	$ 0.67	$ 3.26
Impairment of intangible assets												$ 85	$ 0	$ 12
Acquisition-related costs												0	27	0
Amortization of purchased intangible assets												322	117	0
Tax benefit resulting from adoption of new share-based compensation guidance				$ 5								10
Adoption of new share-based compensation guidance, increase in basic earnings per share				$ 0.03
Adoption of new share-based compensation guidance, increase in diluted earnings per share				$ 0.02
Tax expense attributable to change in deferred tax liability from outside basis difference								$ 0
Restructuring expenses												3	42	15
Restructuring expenses												$ 3	$ 38
Soliris | FRANCE
Earnings per common share
Reimbursement Revenue														$ 88
[1]	Included within operating expenses for the fourth quarter of 2016 is an impairment charge of $85 associated with an early stage clinical indefinite-lived intangible asset .
[2]	Included within net income for the second quarter of 2016 are tax benefits of $5 resulting from our adoption of new share-based compensation guidance during the third quarter of 2016. This resulted in an increase in basic EPS and diluted EPS of $0.03 and $0.02, respectively.
[3]	Included within net income for the third quarter of 2015 is a one-time tax expense of $316 resulting from our integration of the Synageva business with and into the Alexion business. This tax expense is attributable to the change in our deferred tax liability for the outside basis difference resulting from the movement of assets into our captive foreign partnership.