Regeneron Pharmaceuticals (REGN) 10-K 11 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 04, 2016	Jun. 30, 2015
Entity Information [Line Items]
Entity Registrant Name	REGENERON PHARMACEUTICALS INC
Entity Central Index Key	872,589
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 50,626,000,000
Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		102,874,369
Class A Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		1,913,776

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 809,102	$ 648,719
Marketable securities	236,121	251,761
Accounts receivable - trade, net	1,152,489	739,379
Accounts receivable from Sanofi	153,152	111,510
Accounts receivable from Bayer HealthCare	162,152	125,483
Inventories	238,578	128,861
Prepaid expenses and other current assets	163,501	79,046
Total current assets	2,915,095	2,084,759
Marketable securities	632,162	460,154
Property, plant, and equipment, at cost, net of accumulated depreciation and amortization	1,594,120	974,309
Deferred tax assets	461,945	315,416
Other assets	5,810	3,034
Total assets	5,609,132	3,837,672
Current liabilities:
Accounts payable and accrued expenses	644,112	483,489
Deferred revenue from Sanofi, current portion	101,573	15,927
Deferred revenue - other, current portion	51,914	58,098
Other current liabilities	13,563	97,146
Total current liabilities	811,162	654,660
Deferred revenue from Sanofi	582,664	62,819
Deferred revenue - other	82,015	72,430
Facility lease obligations	362,919	310,938
Convertible senior notes	0	146,773
Other long term liabilities	115,535	39,801
Total liabilities	$ 1,954,295	$ 1,287,421
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred Stock	$ 0	$ 0
Additional paid-in capital	3,099,526	2,450,782
Retained earnings	852,700	216,644
Accumulated other comprehensive income	8,572	52,251
Treasury Stock	(306,069)	(169,530)
Total stockholders' equity	3,654,837	2,550,251
Total liabilities and stockholders' equity	5,609,132	3,837,672
Class A Stock
Stockholders' equity:
Common stock	2	2
Total stockholders' equity	2	2
Common Stock
Stockholders' equity:
Common stock	106	102
Total stockholders' equity	$ 106	$ 102

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Liabilities and Equity [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	30,000,000	30,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury stock, shares outstanding (in shares)	3,642,820	2,017,732
Class A Stock
Liabilities and Equity [Abstract]
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	40,000,000	40,000,000
Common Stock, shares issued (in shares)	1,913,776	1,973,368
Common Stock, shares outstanding (in shares)	1,913,776	1,973,368
Common Stock
Liabilities and Equity [Abstract]
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	320,000,000
Common Stock, shares issued (in shares)	106,378,001	102,475,154

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Net product sales	$ 2,689,478	$ 1,750,762	$ 1,425,839
Sanofi collaboration revenue	758,873	541,299	430,111
Bayer HealthCare collaboration revenue	580,488	495,555	220,289
Other revenue	74,889	31,941	28,506
Total revenues	4,103,728	2,819,557	2,104,745
Expenses:
Research and development	1,620,577	1,271,353	859,947
Selling, general, and administrative	838,526	519,267	346,393
Cost of goods sold	241,702	129,030	118,048
Cost of collaboration and contract manufacturing	151,007	75,988	37,307
Total expenses	2,851,812	1,995,638	1,361,695
Income from operations	1,251,916	823,919	743,050
Other income (expense):
Investment and other income (expense)	6,283	8,157	(231)
Interest expense	(14,241)	(37,372)	(46,437)
Loss on Extinguishment of Debt	(18,861)	(33,469)	0
Total other income (expense)	(26,819)	(62,684)	(46,668)
Income before income taxes	1,225,097	761,235	696,382
Income tax expense	(589,041)	(423,109)	(282,644)
Net income	$ 636,056	$ 338,126	$ 413,738
Net income per share - basic	$ 6.17	$ 3.36	$ 4.23
Net income per share - diluted	$ 5.52	$ 2.98	$ 3.72
Weighted average shares outstanding - basic	103,061	100,612	97,917
Weighted average shares outstanding - diluted	115,230	113,413	111,290
Statements of Comprehensive Income
Net income	$ 636,056	$ 338,126	$ 413,738
Other comprehensive income:
Unrealized gain (loss) on marketable securities, net of tax	(43,679)	53,439	(22)
Comprehensive income	$ 592,377	$ 391,565	$ 413,716

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Common Class A	Common Stock
Balance at Dec. 31, 2012	$ 1,256,618	$ 1,792,907	$ (535,220)	$ 0	$ (1,166)	$ 2	$ 95
Balance (shares) at Dec. 31, 2012				0		2,069	95,223
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	54,762	54,759					$ 3
Issuance of Common Stock in connection with exercise of stock options (shares)							3,052
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(195,087)	(195,086)					$ (1)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(701)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	5,718	5,718
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							38
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)							6
Conversion of Class A Stock to Common Stock (shares)						49	49
Stock-based compensation charges	217,080	217,080
Excess tax benefit from stock-based compensation	211,909	211,909
Net income	413,738
Other comprehensive income (loss), net of tax	(22)				(22)
Balance at Dec. 31, 2013	1,964,716	2,087,287	(121,482)	$ 0	(1,188)	$ 2	$ 97
Balance (shares) at Dec. 31, 2013				0		2,020	97,667
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	125,897	125,893					$ 4
Issuance of Common Stock in connection with exercise of stock options (shares)							3,468
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(267,584)	(267,583)					$ (1)
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(754)
Issuance of Common Stock in connection with conversion of convertible senior notes	691,356	691,354					$ 2
Issuance of Common Stock in connection with conversion of convertible senior notes (in shares)							2,018
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	13,125	13,125
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							21
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)							8
Conversion of Class A Stock to Common Stock (shares)						47	47
Stock-based compensation charges	326,815	326,815
Excess tax benefit from stock-based compensation	439,278	439,278
Acquisition of Common Stock in connection with exercise of convertible note hedges	0	169,530		$ 169,530
Acquisition of Common Stock in connection with exercise of convertible note hedges (in shares)				2,018
Reduction of warrants	(294,552)	(294,552)
Reclassification of warrant liability	(148,496)	(148,496)
Reduction of equity component of convertible senior notes	(691,869)	(691,869)
Net income	338,126
Other comprehensive income (loss), net of tax	53,439				53,439
Balance at Dec. 31, 2014	2,550,251	2,450,782	216,644	$ (169,530)	52,251	$ 2	$ 102
Balance (shares) at Dec. 31, 2014				2,018		1,973	102,475
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	215,462	215,460					$ 2
Issuance of Common Stock in connection with exercise of stock options (shares)							2,457
Common Stock tendered upon exercise of stock options in connection with employee tax obligations	(160,538)	(160,538)					$ 0
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (in shares)							(298)
Issuance of Common Stock in connection with conversion of convertible senior notes	818,360	818,358					$ 2
Issuance of Common Stock in connection with conversion of convertible senior notes (in shares)							1,625
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	15,382	15,382
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)							31
Issuance of restricted Common Stock under Long-Term Incentive Plan	0
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)							28
Conversion of Class A Stock to Common Stock (shares)						60	60
Stock-based compensation charges	464,022	464,022
Excess tax benefit from stock-based compensation	405,317	405,317
Acquisition of Common Stock in connection with exercise of convertible note hedges	0	136,539		$ 136,539
Acquisition of Common Stock in connection with exercise of convertible note hedges (in shares)				1,625
Reduction of warrants	(449,456)	(449,456)
Reclassification of warrant liability	(23,317)	(23,317)
Reduction of equity component of convertible senior notes	(819,657)	(819,657)
Net income	636,056
Other comprehensive income (loss), net of tax	(43,679)				(43,679)
Balance at Dec. 31, 2015	$ 3,654,837	$ 3,099,526	$ 852,700	$ (306,069)	$ 8,572	$ 2	$ 106
Balance (shares) at Dec. 31, 2015				3,643		1,913	106,378

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 636,056	$ 338,126	$ 413,738
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	74,909	52,686	41,204
Non-cash compensation expense	459,049	321,750	215,377
Loss on Extinguishment of Debt	18,861	33,469	0
Other non-cash charges and expenses, net	33,701	44,102	46,751
Increase (Decrease) in Deferred Income Taxes	(121,623)	(53,276)	62,195
Changes in assets and liabilites
Increase in Sanofi, Bayer HealthCare, and trade accounts receivable	(491,421)	(34,927)	(245,472)
Increase in Inventories	(111,825)	(56,947)	(47,956)
(Increase) decrease in prepaid expenses and other assets	(79,476)	(45,327)	7,571
Increase (decrease) in deferred revenue	608,892	(8,403)	(41,496)
Increase in accounts payable, accrued expenses and other liabilities	303,657	161,182	136,684
Total adjustments	694,724	414,309	174,858
Net cash provided by operating activities	1,330,780	752,435	588,596
Cash flows from investing activities:
Purchases of marketable securities	(557,105)	(564,188)	(577,278)
Sales or maturities of marketable securities	327,437	476,417	378,146
Capital expenditures	(677,933)	(333,006)	(156,323)
Net cash used in by investing activities	(907,601)	(420,777)	(355,455)
Cash flows from financing activities:
Proceeds from (Repayments of) Long-term Debt and Capital Securities	26,020	(1,095)	(2,024)
Repayments of convertible senior debt	(166,467)	(220,639)	0
Payments in connection with reduction of outstanding warrants	(573,487)	(294,552)	0
Proceeds from issuance of Common Stock	206,358	126,045	57,393
Payments in connection with Common Stock tendered for employee tax obligations	(160,537)	(267,584)	(195,087)
Excess tax benefit from stock-based compensation	405,317	439,278	211,909
Net cash (used in) provided by financing activities	(262,796)	(218,547)	72,191
Net increase in cash and cash equivalents	160,383	113,111	305,332
Cash and cash equivalents at beginning of period	648,719	535,608	230,276
Cash and cash equivalents at end of period	809,102	648,719	535,608
Cash paid for interest (net of amounts capitalized)	10,582	20,348	23,197
Cash paid for income taxes	276,092	59,847	$ 1,057
Warrant
Cash flows from financing activities:
Payments in connection with reduction of outstanding warrants	$ (399,500)	$ (294,600)

Business Overview and Summary o

Business Overview and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Business Overview and Summary of Significant Accounting Policies Organization and Business Regeneron Pharmaceuticals, Inc. and its subsidiaries (collectively, the "Company" or "Regeneron") is a fully integrated biopharmaceutical company that discovers, invents, develops, manufactures, and commercializes medicines for the treatment of serious medical conditions. The Company has product candidates in development in areas of high unmet medical need, including oncology, rheumatoid arthritis, asthma, atopic dermatitis, pain, and infectious diseases. The Company is a party to collaboration agreements to develop certain of these product candidates (see Note 3). The Company currently has three marketed products: • EYLEA ® (aflibercept) Injection , known in the scientific literature as VEGF Trap-Eye, which is available in the United States, European Union ("EU"), Japan, and certain other countries outside the United States for the treatment of neovascular age-related macular degeneration ("wet AMD"), diabetic macular edema ("DME"), macular edema following retinal vein occlusion ("RVO"), which includes macular edema following central retinal vein occlusion ("CRVO") and macular edema following branch retinal vein occlusion ("BRVO"). EYLEA is also available in Japan and the EU for the treatment of myopic choroidal neovascularization ("mCNV") and in the United States for the treatment of diabetic retinopathy in patients with DME. • Praluent ® (alirocumab) Injection , which was approved by the U.S. Food and Drug Administration ("FDA") in July 2015 as an adjunct to diet and maximally tolerated statin therapy for the treatment of adults with heterozygous familial hypercholesterolemia or clinical atherosclerotic cardiovascular disease ("ASCVD"), who require additional lowering of low-density lipoprotein ("LDL") cholesterol. In September 2015, the European Commission granted marketing authorization of Praluent for the treatment of adult patients with primary hypercholesterolemia (heterozygous familial hypercholesterolemia ("HeFH") and non-familial) or mixed dyslipidemia as an adjunct to diet: (a) in combination with a statin, or statin with other lipid-lowering therapies in patients unable to reach their LDL-cholesterol goals with the maximally-tolerated dose of a statin, or (b) alone or in combination with other lipid-lowering therapies for patients who are statin intolerant, or for whom a statin is contraindicated. The effect of Praluent on cardiovascular morbidity and mortality has not been determined. • ARCALYST ® (rilonacept) Injection for Subcutaneous Use , which is available in the United States for the treatment of Cryopyrin-Associated Periodic Syndromes ("CAPS"), including Familial Cold Auto-inflammatory Syndrome ("FCAS") and Muckle-Wells Syndrome ("MWS"), in adults and children 12 and older. The Company operates in one business segment, which includes all activities related to the discovery, development, and commercialization of pharmaceutical products for the treatment of serious medical conditions. The Company's business is subject to certain risks including, but not limited to, uncertainties relating to conducting pharmaceutical research, product development, obtaining regulatory approvals, market acceptance, competition, and obtaining and enforcing patents. Basis of Presentation The consolidated financial statements include the accounts of Regeneron and its wholly-owned subsidiaries. Intercompany balances and transactions are eliminated in consolidation. The previously issued (i) Consolidated Balance Sheet as of December 31, 2014 contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2014, and (ii) Consolidated Statements of Operations and Comprehensive Income for the years ended December 31, 2014 and 2013, Consolidated Statements of Stockholders' Equity for the years ended December 31, 2014 and 2013, and Consolidated Statements of Cash Flows for the years ended December 31, 2014 and 2013 contained in the Company's Annual Report on Form 10-K for the year ended December 31, 2014, have each been revised in this Annual Report on Form 10-K to reflect a correction in the Company's accounting for certain stock option awards. See Note 14. In addition, the previously issued Consolidated Balance Sheet as of December 31, 2014 in this Annual Report on Form 10-K was revised to reflect a correction related to the accounting for costs incurred in connection with commercial bulk drug product manufactured by the Company, but not billed, under the Company's collaboration agreements with Sanofi and Bayer HealthCare LLC, and the related tax impacts. The correcting adjustments resulted in a reduction to both accounts receivable and deferred revenue by $41.0 million , and reduced both income tax assets, net and additional paid-in capital by $14.2 million . The previously issued Consolidated Statements of Cash Flows for the years ended December 31, 2014 and 2013 were also revised in this Annual Report on Form 10-K to reflect a $9.3 million and $4.9 million increase, respectively, in cash flows from operating activities and a corresponding reduction in cash flows from financing activities related to the tax impact of these adjustments. These adjustments had no impact on the Company's previously issued Consolidated Statements of Operations and Comprehensive Income in any reporting period. The Company determined that the error is not material to any previously-issued financial statements. Certain reclassifications have been made to prior period amounts to conform with the current period's presentation. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Estimates which could have a significant impact on the Company's financial statements include provisions related to product sales, such as rebates, chargebacks, and distribution-related fees; periods over which payments, including non-refundable up-front, license, and milestone payments, are recognized as revenue in connection with collaboration and other agreements; periods over which certain clinical trial costs are recognized; fair value of stock options; inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value; capitalization of inventory costs associated with the Company's products prior to regulatory approval; deferred tax asset valuation allowances; and the assessment of uncertain tax positions. With respect to the Company's collaborations with Sanofi and Bayer HealthCare: • Included in Sanofi collaboration revenue is the Company's share of profits or losses from commercialization of antibodies, which is provided by Sanofi, and include an estimate of the Company's share of profits or losses for the most recent fiscal quarter. • Included in Bayer HealthCare collaboration revenue is the Company's share of profits or losses from commercialization of EYLEA outside the United States, which is provided by Bayer HealthCare, and includes an estimate of the Company's share of profits or losses for the most recent fiscal quarter. • Included in research and development expenses is the Company's share of development expenses incurred by Bayer HealthCare and Sanofi, including the Company's share of Bayer HealthCare and Sanofi estimated development expenses for the most recent fiscal quarter. These estimates for the most recent period are adjusted, if necessary, in the subsequent period to reflect actual amounts. Cash and Cash Equivalents The Company considers all highly liquid debt instruments with a maturity of three months or less when purchased to be cash equivalents. The carrying amount reported in the Balance Sheet for cash and cash equivalents approximates its fair value. Marketable Securities The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. The Company invests its excess cash primarily in marketable securities issued by investment grade institutions. The Company considers its marketable securities to be "available-for-sale," as defined by authoritative guidance issued by the Financial Accounting Standards Board ("FASB"). These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). If a decline in the value of a marketable security in the Company's investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. Accounts Receivable - Trade The Company's trade accounts receivable arise from product sales and represent amounts due from its distributors and specialty pharmacies (collectively, the Company's "customers"), which are all located in the United States. The Company monitors the financial performance and credit worthiness of its large customers so that it can properly assess and respond to changes in their credit profile. The Company provides reserves against trade receivables for estimated losses, if any, that may result from a customer's inability to pay. Amounts determined to be uncollectible are written-off against the reserve. Inventories Inventories are stated at the lower of cost or estimated realizable value. The Company determines the cost of inventory using the first-in, first-out, or FIFO, method. The Company capitalizes inventory costs associated with the Company's products prior to regulatory approval when, based on management's judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed as research and development. The determination to capitalize inventory costs is based on various factors, including status and expectations of the regulatory approval process, any known safety or efficacy concerns, potential labeling restrictions, and any other impediments to obtaining regulatory approval. The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes-down such inventories as appropriate. In addition, the Company's products are subject to strict quality control and monitoring which the Company performs throughout the manufacturing process. If certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, the Company records a charge to cost of goods sold to write down such unmarketable inventory to its estimated realizable value. Property, Plant, and Equipment Property, plant, and equipment are stated at cost, net of accumulated depreciation. Depreciation is provided on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the lease term. Costs of construction of certain long-lived assets include capitalized interest, which is amortized over the estimated useful life of the related asset. Expenditures for maintenance and repairs which do not materially extend the useful lives of the assets are charged to expense as incurred. The cost and accumulated depreciation or amortization of assets retired or sold are removed from the respective accounts, and any gain or loss is recognized in operations. The estimated useful lives of property, plant, and equipment are as follows: Building and improvements 10-30 years Laboratory and other equipment 3-10 years Furniture and fixtures 5 years The Company periodically assesses the recoverability of long-lived assets, such as property, plant, and equipment, and evaluates such assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Revenue Recognition a. Product Revenue Product sales consist of U.S. sales of EYLEA and ARCALYST. Revenue from product sales is recognized when persuasive evidence of an arrangement exists, title to product and associated risk of loss have passed to the customer, the price is fixed or determinable, collection from the customer is reasonably assured, the Company has no further performance obligations, and returns can be reasonably estimated. The Company's written contracts with its customers stipulate product is shipped freight on board destination (FOB destination). The Company records revenue from product sales upon delivery to its customers. The Company sells EYLEA in the United States to several distributors and specialty pharmacies. The Company sells ARCALYST in the United States to two specialty pharmacies. Under these distribution models, the distributors and specialty pharmacies generally take physical delivery of product. For EYLEA, the distributors and specialty pharmacies generally sell the product directly to healthcare providers, whereas for ARCALYST, the specialty pharmacies sell the product directly to patients. Revenue from product sales is recorded net of applicable provisions for rebates and chargebacks under governmental programs, distribution-related fees, and other sales-related deductions. Calculating these provisions involves estimates and judgments. The Company reviews its estimates of rebates, chargebacks, and other applicable provisions each period and records any necessary adjustments in the current period's net product sales. Government Rebates and Chargebacks: The Company estimates reductions to product sales for Medicaid and Veterans' Administration ("VA") programs, and for certain other qualifying federal and state government programs. Based upon the Company's contracts with government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, and estimated payer mix, the Company estimates and records an allowance for rebates and chargebacks. The Company's liability for Medicaid rebates consists of estimates for claims that a state will make for a current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, and invoices received for claims from prior quarters that have not been paid. The Company's reserves related to discounted pricing to VA, Public Health Services ("PHS"), and other institutions (collectively "qualified healthcare providers") represent the Company's estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices the Company charges to its customers (i.e., distributors and specialty pharmacies). The Company's customers charge the Company for the difference between what they pay for the products and the ultimate selling price to the qualified healthcare providers. The Company's reserve for this discounted pricing is based on expected sales to qualified healthcare providers and the chargebacks that customers have already claimed. Distribution-Related Fees: The Company has written contracts with its customers that include terms for distribution-related fees. The Company estimates and records distribution and related fees due to its customers based on gross sales. Prompt Pay Discounts: No prompt pay discounts are currently offered to the Company's customers on sales of EYLEA. In connection with sales of ARCALYST, the Company offers discounts to its customers for prompt payments. The Company estimates these discounts based on customer terms and historical experience, and expects that its customers will always take advantage of this discount. Therefore, the Company accrues 100% of the prompt pay discount that is based on the gross amount of each ARCALYST invoice, at the time of sale. Product Returns: Consistent with industry practice, the Company offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product's expiration date. The Company will accept returns for three months prior to and up to six months after the product expiration date. Product returned is generally not resalable given the nature of the Company's products and method of administration. The Company develops estimates for product returns based upon historical experience, inventory levels in the distribution channel, shelf life of the product, and other relevant factors. The Company monitors product supply levels in the distribution channel, as well as sales by its customers of EYLEA to healthcare providers and ARCALYST to patients using product-specific data provided by its customers. If necessary, the Company's estimates of product returns may be adjusted in the future based on actual returns experience, known or expected changes in the marketplace, or other factors. b. Collaboration Revenue The Company earns collaboration revenue in connection with collaboration agreements to develop and commercialize product candidates and utilize the Company's technology platforms. These arrangements may require the Company to deliver various rights, services, and/or goods across the entire life cycle of a product or product candidate. The terms of these agreements typically include that consideration be provided to the Company in the form of non-refundable up-front payments, milestone payments, payments for development and commercialization activities, and sharing of profits or losses arising from the commercialization of products. In connection with non-refundable up-front payments, the Company's performance period estimates are principally based on projections of the scope, progress, and results of its research and development activities. Due to the variability in the scope of activities and length of time necessary to develop a drug product, changes to development plans as programs progress, and uncertainty in the ultimate requirements to obtain regulatory approval for commercialization, revisions to performance period estimates are likely to occur periodically, and could result in material changes to the amount of revenue recognized each year in the future. In addition, estimated performance periods may change if development programs encounter delays, or the Company and its collaborators decide to expand or contract the clinical plans for a drug candidate in various disease indications. In arrangements involving multiple deliverables, each required deliverable is evaluated to determine whether it qualifies as a separate unit of accounting. This determination is generally based on whether the deliverables in the arrangement meet certain criteria, including whether the delivered item or items has value to the collaborator on a standalone basis. The arrangement's consideration that is fixed and determinable is allocated to each separate unit of accounting based on the relative selling price of each deliverable. If multiple collaboration activities or rights do not require separation, they are combined into a single unit of accounting and recognized over the performance period, which is the period over which the Company is obligated to deliver goods or services. The Company estimates its performance period based on the specific terms of each agreement, and adjusts the performance periods, if appropriate, based on the applicable facts and circumstances. Payments which are based on achieving a specific substantive performance milestone, involving a degree of risk, are recognized as revenue when the milestone is achieved and the related payment is due and non-refundable, provided there is no future service obligation associated with that milestone. Substantive performance milestones typically consist of significant achievements in the development life-cycle of the related product candidate, such as completion of clinical trials, filing for approval with regulatory agencies, and receipt of approvals by regulatory agencies. In determining whether a payment is deemed to be a substantive performance milestone, the Company takes into consideration (i) the enhancement in value to the related development product candidate, (ii) the Company's performance and the relative level of effort required to achieve the milestone, (iii) whether the milestone relates solely to past performance, and (iv) whether the milestone payment is considered reasonable relative to all of the deliverables and payment terms. Payments for achieving milestones which are not considered substantive are deferred and recognized over the related performance period. The Company enters into collaboration agreements that include varying arrangements regarding which parties perform and bear the costs of research and development activities. The Company may share the costs of research and development activities with a collaborator, or the Company may be reimbursed for all or a significant portion of the costs of the Company's research and development activities. The Company records its internal and third-party development costs associated with these collaborations as research and development expenses. When the Company is entitled to reimbursement of all or a portion of the research and development expenses that it incurs under a collaboration, the Company records those reimbursable amounts as collaboration revenue proportionately as the Company recognizes its expenses. If the collaboration is a cost-sharing arrangement in which both the Company and its collaborator perform development work and share costs, the Company also recognizes, as additional research and development expense in the period when its collaborator incurs development expenses, the portion of the collaborator's development expenses that the Company is obligated to reimburse. The Company may also be obligated to use commercially reasonable efforts to supply commercial bulk product to its collaborators. In such cases, the Company is reimbursed for its manufacturing costs as commercial product is shipped to its collaborators; however, recognition of such cost reimbursements as collaboration revenue is deferred until the product is sold by the Company's collaborators to third-party customers, at which time the Company's risk of inventory loss no longer exists. In addition, at that time, the related manufacturing costs for the sold product, which had been capitalized into inventory, are recognized by the Company. Under the Company's collaboration agreements, product sales and cost of sales for products which are currently approved are recorded by the Company's collaborators. The Company shares in any profits or losses arising from the commercialization of such products. The Company records its share of the profits or losses from commercialization of such products, representing net product sales less cost of goods sold and shared commercialization and other expenses, as collaboration revenue. Research and Development Expenses Research and development expenses include costs directly attributable to the conduct of research and development programs, including the cost of salaries, payroll taxes, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, costs related to research collaboration and licensing agreements, the cost of services provided by outside contractors, including services related to the Company's clinical trials, clinical trial expenses, the full cost of manufacturing drug for use in research, preclinical development, and clinical trials, amounts that the Company is obligated to reimburse to collaborators for research and development expenses that they incur, and the allocable portions of facility costs, such as rent, utilities, insurance, repairs and maintenance, depreciation, and general support services. Costs associated with research and development are expensed. Clinical trial costs are a significant component of research and development expenses and include costs associated with third-party contractors. The Company outsources a substantial portion of its clinical trial activities, utilizing external entities such as contract research organizations ("CROs"), independent clinical investigators, and other third-party service providers to assist the Company with the execution of its clinical studies. For each clinical trial that the Company conducts, certain clinical trial costs are expensed immediately, while others are expensed over time based on the expected total number of patients in the trial, the rate at which patients enter the trial, and/or the period over which clinical investigators or CROs are expected to provide services. Clinical activities which relate principally to clinical sites and other administrative functions to manage the Company's clinical trials are performed primarily by CROs. CROs typically perform most of the start-up activities for the Company's trials, including document preparation, site identification, screening and preparation, pre-study visits, training, and program management. These start-up costs usually occur within a few months after the contract has been executed and are event driven in nature. The remaining activities and related costs, such as patient monitoring and administration, generally occur ratably throughout the life of the individual contract or study. In the event of early termination of a clinical trial, the Company accrues and recognizes expenses in an amount based on its estimate of the remaining non-cancelable obligations associated with the winding down of the clinical trial and/or penalties. For clinical study sites, where payments are made periodically on a per-patient basis to the institutions performing the clinical study, the Company accrues expenses on an estimated cost-per-patient basis, based on subject enrollment and activity in each quarter. The amount of clinical study expense recognized in a quarter may vary from period to period based on the duration and progress of the study, the activities to be performed by the sites each quarter, the required level of patient enrollment, the rate at which patients actually enroll in and drop-out of the clinical study, and the number of sites involved in the study. Clinical trials that bear the greatest risk of change in estimates are typically those that have a significant number of sites, require a large number of patients, have complex patient screening requirements, and span multiple years. During the course of a trial, the Company adjusts its rate of clinical expense recognition if actual results differ from the Company's estimates. The Company's estimates and assumptions for clinical expense recognition could differ significantly from its actual results, which could cause material increases or decreases in research and development expenses in future periods when the actual results become known. Stock-based Compensation The Company recognizes stock-based compensation expense for grants of stock option awards and restricted stock under the Company's Long-Term Incentive Plans to employees and non-employee members of the Company's board of directors based on the grant-date fair value of those awards. The grant-date fair value of an award is generally recognized as compensation expense over the award's requisite service period. The Company uses the Black-Scholes model to compute the estimated fair value of stock option awards. Using this model, fair value is calculated based on assumptions with respect to (i) expected volatility of the Company's Common Stock price, (ii) the periods of time over which employees and members of the board of directors are expected to hold their options prior to exercise (expected lives), (iii) expected dividend yield on the Common Stock, and (iv) risk-free interest rates. Stock-based compensation expense also includes an estimate, which is made at the time of grant, of the number of awards that are expected to be forfeited. This estimate is revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Income Taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax assets and liabilities are determined on the basis of the difference between the tax basis of assets and liabilities and their respective financial reporting amounts ("temporary differences") at enacted tax rates in effect for the years in which the differences are expected to reverse. A valuation allowance is established for deferred tax assets for which it is more likely than not that some portion or all of the deferred tax assets will not be realized. Uncertain tax positions, for which management's assessment is that there is more than a 50% probability of sustaining the position upon challenge by a taxing authority based upon its technical merits, are subjected to certain recognition and measurement criteria. The Company re-evaluates uncertain tax positions and consider various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, and changes in facts or circumstances related to a tax position. The Company adjusts the level of the liability to reflect any subsequent changes in the relevant facts and circumstances surrounding the uncertain positions. The Company recognizes interest and penalties related to income tax matters in income tax expense. Per Share Data Basic net income per share is computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Basic net income per share excludes restricted stock awards until vested. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were converted or exercised during the period, when the effect is dilutive. Common stock equivalents include: (i) outstanding stock options and restricted stock awards under the Company's Long-Term Incentive Plans, which are included under the "treasury stock method" when dilutive, (ii) Common Stock to be issued upon the assumed conversion of the Company's convertible senior notes, which are included under the "if-converted method" when dilutive, and (iii) Common Stock to be issued upon the exercise of outstanding warrants, which are included under the "treasury stock method" when dilutive. Concentration of Credit Risk Financial instruments which potentially expose the Company to concentrations of credit risk consist of cash, cash equivalents, certain financial instruments, and accounts receivable. A large portion of the Company's cash is held by a few major financial institutions. In accordance with the Company's policies, the Company mandates asset diversification and monitors exposure with its counterparties. Concentrations of credit risk with respect to accounts receivable are significant. Accounts receivable from product sales of EYLEA and ARCALYST are due from several distributors and specialty pharmacies, who are the Company's customers. As of December 31, 2015 and 2014, one individual customer accounted for 68% and 70% , respectively, of the Company's net trade accounts receivable balances. The Company has contractual payment terms with each of its customers, and the Company monitors its customers' financial performance and credit worthiness so that it can properly assess and respond to any changes in their credit profile. In addition, the Company may insure a portion of its accounts receivables within its overall risk management practices. As of December 31, 2015 and 2014, there were no reserves against trade accounts receivable. In addition, during the years ended December 31, 2015, 2014, and 2013, the Company did no t recognize any charges for write-offs of trade accounts receivable. Recently Issued Accounting Standards In November 2015, the FASB issued Accounting Standards Update 2015-17, Balance Sheet Classification of Deferred Taxes , which is intended to simplify the balance sheet presentation of deferred income taxes. Current accounting principles require an entity to separate deferred income t

Net Product Sales

Net Product Sales	12 Months Ended
	Dec. 31, 2015
Revenues [Abstract]
Net Product Sales	Product Sales Net product sales consist of U.S. sales of EYLEA and ARCALYST. The Company received marketing approval from the FDA for EYLEA for the treatment of wet AMD in 2011, macular edema following CRVO in 2012, DME in July 2014, macular edema following BRVO in October 2014, and diabetic retinopathy in patients with DME in March 2015. EYLEA net product sales in the United States totaled $2,676.0 million , $1,736.4 million , and $1,408.7 million for the years ended December 31, 2015 , 2014, and 2013, respectively. ARCALYST net product sales totaled $13.5 million , $14.4 million , and $17.1 million for the years ended December 31, 2015 , 2014, and 2013, respectively. For the years ended December 31, 2015 , 2014, and 2013, the Company recorded 67% , 73% , and 76% , respectively, of its total gross product revenue from sales to Besse Medical, a subsidiary of AmerisourceBergen Corporation. Revenue from product sales is recorded net of applicable provisions for rebates and chargebacks under governmental programs, distribution-related fees, and other sales-related deductions. The following table summarizes the provisions, and credits/payments, for these sales-related deductions for the years ended December 31, 2015, 2014, and 2013. Rebates & Chargebacks Distribution- Related Fees Other Sales- Related Deductions Total Balance as of December 31, 2012 $ 2,983 $ 15,298 $ 545 $ 18,826 Provision related to current period sales 25,936 62,984 955 89,875 Credits/payments (24,519 ) (58,619 ) (962 ) (84,100 ) Balance as of December 31, 2013 4,400 19,663 538 24,601 Provision related to current period sales 33,117 77,160 1,578 111,855 Credits/payments (34,434 ) (75,657 ) (1,584 ) (111,675 ) Balance as of December 31, 2014 3,083 21,166 532 24,781 Provision related to current period sales 61,124 122,466 9,600 193,190 Credits/payments (57,788 ) (95,319 ) (9,615 ) (162,722 ) Balance as of December 31, 2015 $ 6,419 $ 48,313 $ 517 $ 55,249 Under the provisions of the Patient Protection and Affordable Care Act ("PPACA") and the Health Care and Education Reconciliation Act of 2010, a non-tax deductible annual fee (the "Branded Prescription Drug Fee") is imposed on pharmaceutical manufacturers that sell branded prescription drugs to specified government programs. Orphan drugs sales, including ARCALYST, are not subject to the fee. In July 2014, the Internal Revenue Service ("IRS") issued final regulations that provide guidance on the Branded Prescription Drug Fee. As a result of the issuance of these final IRS regulations, an incremental charge was recorded to (i) recognize a liability for the estimated fee payable based on 2014 sales through the first nine months of 2014, and (ii) expense the remaining prepaid asset recorded under the previous accounting for the estimated fee payable based on 2013 sales. The impact of the incremental charge in the third quarter of 2014 was $40.6 million , which was included in selling, general, and administrative expenses.

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2015
Collaboration Agreement [Abstract]
Collaboration and Contract Research Agreements	Collaboration Agreements The Company has entered into various agreements related to its activities to research, develop, manufacture, and commercialize product candidates and utilize its technology platforms. Significant agreements of this kind are described below. a. Sanofi Sanofi owned a total of 23,108,570 shares of the Company's Common Stock as of December 31, 2015, a portion of which was purchased in connection with the companies' ZALTRAP ® and antibody collaborations described below. See Note 13 for a description of the investor agreement between Sanofi and the Company. The collaboration revenue the Company earned from Sanofi is detailed below: Year Ended December 31, Sanofi Collaboration Revenue 2015 2014 2013 Antibody: Reimbursement of Regeneron research and development expenses $ 735,439 $ 547,761 $ 453,489 Reimbursement of Regeneron commercialization-related expenses 157,350 19,480 1,868 Regeneron's share of losses in connection with commercialization of antibodies (240,042 ) (41,378 ) — Up-front payments to Sanofi for acquisition of rights related to two antibodies — — (20,000 ) Other 10,243 10,243 10,243 Total Antibody 662,990 536,106 445,600 Immuno-oncology: Reimbursement of Regeneron research and development expenses 39,961 — — Other 40,000 — — Total Immuno-oncology 79,961 — — ZALTRAP: Regeneron's share of losses in connection with commercialization of ZALTRAP — (4,715 ) (30,810 ) Reimbursement of Regeneron research and development expenses 686 4,806 5,639 Other 15,236 5,102 9,682 Total ZALTRAP 15,922 5,193 (15,489 ) $ 758,873 $ 541,299 $ 430,111 Other selected financial information in connection with the Company's collaboration agreements with Sanofi is as follows: December 31, 2015 2014 Antibody: Accounts receivable, net $ 126,687 $ 110,559 Deferred revenue 84,237 64,408 Immuno-oncology: Accounts receivable, net $ 21,394 — Deferred revenue 600,000 — Antibodies In November 2007, the Company entered into a global, strategic collaboration with Sanofi to discover, develop, and commercialize fully human monoclonal antibodies (the "Antibody Collaboration") . The Antibody Collaboration is governed by the companies' Discovery and Preclinical Development Agreement ("Antibody Discovery Agreement") and a License and Collaboration Agreement (each as amended). In connection with the execution of the Antibody Discovery Agreement in 2007, the Company received a non-refundable up-front payment of $85.0 million from Sanofi. In addition, under the Antibody Discovery Agreement, Sanofi is funding the Company's research to identify and validate potential drug discovery targets and develop fully human monoclonal antibodies against these targets. In November 2009, the Company and Sanofi amended these collaboration agreements to expand and extend the Antibody Collaboration. Pursuant to the Antibody Discovery Agreement, as amended, Sanofi agreed to fund up to $160.0 million per year of the Company's research activities in 2010 through 2017. However, in July 2015, in connection with the Company’s new immuno-oncology collaboration with Sanofi, as described below, the Company’s Antibody Discovery Agreement and License and Collaboration Agreement with Sanofi were each amended. In connection with these amendments, Sanofi's funding of the Company’s antibody discovery activities under the existing Antibody Collaboration was reduced to up to $145.0 million in 2015, and up to $130.0 million in both 2016 and 2017, or an aggregate reduction of $75.0 million over this three -year period. In addition, the Company's discovery activities to identify and validate potential drug discovery targets in the field of immuno-oncology and develop fully human monoclonal antibodies against these targets will be funded by Sanofi under the terms of the companies’ new immuno-oncology collaboration. Sanofi has an option to extend certain antibody development and preclinical activities relating to selected program targets for up to an additional three years after 2017. For each drug candidate identified under the Antibody Discovery Agreement, Sanofi has the option to license rights to the candidate under the License and Collaboration Agreement. If it elects to do so, Sanofi will co-develop the drug candidate with the Company through product approval. Under certain defined circumstances, upon exercising its option to license rights to particular candidates, Sanofi must make a $10 million substantive milestone payment to the Company. If Sanofi does not exercise its option to license rights to a particular drug candidate under the License and Collaboration Agreement, or if Sanofi elects not to continue to co-develop a product candidate, the Company retains the exclusive right to develop and commercialize such drug candidate and Sanofi will receive a royalty on sales, if any. The Company and Sanofi are currently co-developing various therapeutic antibodies under the License and Collaboration Agreement. Under the License and Collaboration Agreement, agreed-upon worldwide development expenses incurred by both companies during the term of the agreement are funded by Sanofi, except that following receipt of the first positive Phase 3 trial results for a co-developed drug candidate, subsequent Phase 3 trial-related costs for that drug candidate ("Shared Phase 3 Trial Costs") are shared 80% by Sanofi and 20% by Regeneron. Consequently, commencing in 2013, the Company recognized as additional research and development expense $92.6 million , $109.7 million , and $17.6 million in 2015, 2014, and 2013, respectively, of antibody development expenses that the Company was obligated to reimburse to Sanofi related to Praluent and sarilumab. If the Antibody Collaboration becomes profitable, Regeneron will be obligated to reimburse Sanofi for 50% of worldwide development expenses that were fully funded by Sanofi and 30% of Shared Phase 3 Trial Costs, in accordance with a defined formula based on the amounts of these expenses and the Company's share of collaboration profits from commercialization of collaboration products. However, the Company is not required to apply more than 10% of its share of the profits from the Antibody Collaboration in any calendar quarter to reimburse Sanofi for these development costs. The Company's contingent reimbursement obligation to Sanofi under the Antibody Collaboration was approximately $1,832 million as of December 31, 2015. Sanofi will lead commercialization activities for products developed under the License and Collaboration Agreement, subject to the Company's right to co-promote such products. The parties will equally share profits and losses from sales within the United States. The parties will share profits outside the United States on a sliding scale based on sales starting at 65% (Sanofi)/ 35% (Regeneron) and ending at 55% (Sanofi)/ 45% (Regeneron), and losses outside the United States at 55% (Sanofi)/ 45% (Regeneron). In addition to profit sharing, the Company is entitled to receive up to $250 million in sales milestone payments, with milestone payments commencing only if and after aggregate annual sales outside the United States exceed $1.0 billion on a rolling twelve -month basis. Regeneron is obligated to use commercially reasonable efforts to supply clinical requirements of each drug candidate under the Antibody Collaboration until commercial supplies of that drug candidate are being manufactured. In connection with the November 2009 amendment of the collaboration's Antibody Discovery Agreement, Sanofi funded $30.0 million of agreed-upon costs the Company incurred to expand its manufacturing capacity at its Rensselaer, New York facilities. Additionally, during 2014, Sanofi agreed to fund up to $17.5 million of agreed-upon costs incurred by the Company in connection with expanding the Company's manufacturing capacity at its Rensselaer, New York facility, of which $13.2 million has been received or is receivable as of December 31, 2015. Payments received from Sanofi to fund agreed-upon expansions of the Company's manufacturing capacity are initially recorded as deferred revenue by the Company and are being recognized as collaboration revenue over the related performance period. With respect to each antibody product which enters development under the License and Collaboration Agreement, Sanofi or the Company may, by giving twelve months' notice, opt-out of further development and/or commercialization of the product, in which event the other party retains exclusive rights to continue the development and/or commercialization of the product. The Company may also opt-out of the further development of an antibody product if it gives notice to Sanofi within thirty days of the date that Sanofi enters joint development of such antibody product under the License and Collaboration Agreement. Each of the Antibody Discovery Agreement and the License and Collaboration Agreement contains other termination provisions, including for material breach by the other party. Prior to December 31, 2017, Sanofi has the right to terminate the amended Antibody Discovery Agreement without cause with at least three months advance written notice; however, except under defined circumstances, Sanofi would be obligated to immediately pay to the Company the full amount of unpaid research funding during the remaining term of the research agreement through December 31, 2017. Upon termination of the collaboration in its entirety, the Company's obligation to reimburse Sanofi for development costs out of any future profits from collaboration products will terminate. In the event of termination of the amended Antibody Discovery Agreement, the Company retains exclusive rights to continue the development and/or commercialization of such product(s). Upon expiration of the amended Antibody Discovery Agreement, Sanofi has an option to license the Company's VelocImmune ® technology for an annual license fee plus royalties on any future sales of products developed using VelocImmune technology. In connection with the Antibody Collaboration, in August 2008, the Company entered into a separate agreement with Sanofi, which extended through December 2012, to use Regeneron's proprietary VelociGene ® technology platform to supply Sanofi with genetically modified mammalian models of gene function and disease (the " VelociGene Agreement") . The VelociGene Agreement provided for minimum annual order quantities for the term of the agreement, for which the Company received payments totaling $21.5 million . Payments received were initially recorded as deferred revenue by the Company and are being recognized as collaboration revenue over the related performance period. In May 2013, the Company acquired from Sanofi full exclusive rights to two families of novel antibodies invented at Regeneron and previously included in the Company's Antibody Collaboration with Sanofi. The Company acquired full rights to antibodies targeting the platelet derived growth factor (PDGF) family of receptors and ligands in ophthalmology and all other indications and to antibodies targeting the angiopoietin-2 (Ang2) receptor and ligand in ophthalmology. As noted in the "Sanofi collaboration revenue" table above, in 2013, with respect to PDGF antibodies, the Company made a $10.0 million up-front payment to Sanofi, and, with respect to Ang2 antibodies in ophthalmology, the Company made a $10.0 million up-front payment to Sanofi. In addition, with respect to PDGF antibodies, the Company made two $5.0 million development milestone payments to Sanofi in 2014 and a $10.0 million development milestone payment to Sanofi in 2015, each of which was recorded as research and development expense. The Company is obligated to pay up to $20 million in additional potential development milestones as well as royalties on any future sales of PDGF antibodies. In July 2014, in connection with the Company's Antibody Collaboration with Sanofi, the Company purchased an FDA priority review voucher from a third party for $67.5 million . The Company and Sanofi equally shared the priority review voucher's purchase price, and the Company's share of the cost, or $33.8 million , was recorded as a research and development expense during 2014. The Company subsequently transferred the voucher to Sanofi, which used the priority review voucher in connection with the Biologics License Application submission to the FDA for Praluent. Reimbursement of Regeneron commercialization-related expenses represents reimbursement of internal and external costs in connection with preparing to commercialize or commercializing, as applicable, Praluent and sarilumab. Effective in the second and fourth quarters of 2014, the Company and Sanofi began sharing pre-launch commercialization expenses related to Praluent and sarilumab, respectively, in accordance with the companies’ License and Collaboration Agreement. Consequently, the Company began recording its share of losses in connection with preparing to commercialize these two antibody candidates within Sanofi collaboration revenue. As described in Note 1 above, in July 2015, the FDA approved Praluent in the United States and in September 2015, the European Commission granted marketing authorization of Praluent. Therefore, commencing in 2015, the Company also recorded within Sanofi collaboration revenue its share of the Antibody Collaboration's losses in connection with commercialization of Praluent. Immuno-Oncology In July 2015, the Company and Sanofi entered into a collaboration to discover, develop, and commercialize antibody-based cancer treatments in the field of immuno-oncology (the "IO Collaboration"). The IO Collaboration is governed by an Immuno-oncology Discovery and Development Agreement ("IO Discovery Agreement"), and an Immuno-oncology License and Collaboration Agreement ("IO License and Collaboration Agreement"). In connection with the IO Discovery Agreement, Sanofi made a $265.0 million non-refundable up-front payment to the Company. Pursuant to the IO Discovery Agreement, the Company will spend up to $1,090.0 million ("IO Discovery Budget") to identify and validate potential immuno-oncology targets and develop therapeutic antibodies against such targets through clinical proof-of-concept. Sanofi will reimburse the Company for up to $825.0 million ("IO Discovery Funding") of these costs, subject to certain annual limits, which consists of (i) $750.0 million in new funding and (ii) $75.0 million of funding that would have otherwise been available to Regeneron under the existing Antibody Discovery Agreement, as described above. The term of the IO Discovery Agreement will continue through the later of five years from the effective date of the IO Collaboration or the date the IO Discovery Budget is exhausted, subject to Sanofi’s option to extend it for up to an additional three years for the continued development (and funding) of selected ongoing programs. Pursuant to the IO Discovery Agreement, the Company will be primarily responsible for the design and conduct of all research activities, including target identification and validation, antibody development, preclinical activities, toxicology studies, manufacture of preclinical and clinical supplies, filing of Investigational New Drug ("IND") Applications, and clinical development through proof-of-concept. The Company will reimburse Sanofi for half of the development costs they funded that are attributable to clinical development of antibody product candidates under the IO Discovery Agreement from Regeneron's share of future profits, if any, from commercialized products to the extent they are sufficient for this purpose. However, the Company is not required to apply more than 10% of its share of the profits from IO Collaboration products in any calendar quarter towards reimbursing Sanofi for these development costs. With regard to product candidates for which proof-of-concept is established, Sanofi will have the option to license rights to the product candidate pursuant to the IO License and Collaboration Agreement (as further described below). If Sanofi does not exercise its option to license rights to a product candidate, the Company will retain the exclusive right to develop and commercialize such product candidate and Sanofi will be entitled to receive a royalty on sales. In connection with the IO License and Collaboration Agreement, Sanofi made a $375.0 million non-refundable up-front payment to the Company. If Sanofi exercises its option to license rights to a product candidate thereunder, it will co-develop the drug candidate with the Company through product approval. Principal control of development of each product candidate that enters development under the IO License and Collaboration Agreement will alternate between the Company and Sanofi on a candidate-by-candidate basis. Sanofi will fund drug candidate development costs up front for the candidates for which it is the principal controlling party and the Company will reimburse half of the total development costs for all such candidates from its share of future profits to the extent they are sufficient for this purpose, subject to the same 10% reimbursement limitation described above. In addition, Sanofi and the Company will share equally, on an ongoing basis, the development costs for the drug candidates for which the Company is the principal controlling party. The party having principal control over the development of a product candidate will also lead the commercialization activities for such product candidate in the United States. For all products commercialized under the IO License and Collaboration Agreement, Sanofi will lead commercialization activities outside of the United States. Each party will have the right to co-promote licensed products in countries where it is not the lead commercialization party. The parties will share equally in profits and losses in connection with the commercialization of collaboration products. The Company is obligated to use commercially reasonable efforts to supply clinical requirements of each drug candidate under the IO License and Collaboration Agreement until commercial supplies of that IO drug candidate are being manufactured. Under the terms of the IO License and Collaboration Agreement, the parties will also co-develop the Company’s antibody product candidate targeting the receptor known as Programmed Cell Death protein 1, or PD-1 ("REGN2810"). The parties will share equally, on an ongoing basis, development expenses for REGN2810 up to a total of $650.0 million . The Company will have principal control over the development of REGN2810 and will lead commercialization activities in the United States, subject to Sanofi’s right to co-promote, while Sanofi will lead commercialization activities outside of the United States and the parties will equally share profits from worldwide sales. The Company will be entitled to a milestone payment of $375.0 million in the event that sales of all licensed products targeting PD-1 (including REGN2810), together with sales of any other products licensed under the IO License and Collaboration Agreement and sold for use in combination with a licensed product targeting PD-1, equal or exceed $2 billion in any consecutive twelve -month period. With respect to each product candidate that enters development under the IO License and Collaboration Agreement, Sanofi or the Company may, by giving twelve months’ notice, opt-out of further development and/or commercialization of the product, in which event the other party will retain exclusive rights to continue the development and/or commercialization of such product. At the inception of the IO Collaboration, the Company's significant deliverables consisted of (i) license to certain rights and intellectual property, (ii) providing research and development services, and (iii) manufacturing clinical supplies. The Company concluded that the license did not have standalone value, primarily due to the fact that such rights were not sold separately by the Company, nor could Sanofi receive any benefit from the license without the fulfillment of other ongoing obligations by the Company, including the clinical supply arrangement. Therefore, the deliverables were considered a single unit of accounting. Consequently, the $640.0 million in aggregate up-front payments was initially recorded as deferred revenue, and will be recognized ratably as revenue over the related performance period. ZALTRAP In September 2003, the Company entered into a collaboration agreement ("ZALTRAP Collaboration Agreement") with Aventis Pharmaceuticals Inc. (predecessor to Sanofi U.S.) to jointly develop and commercialize ZALTRAP. Under the terms of the ZALTRAP Collaboration Agreement, as amended, Regeneron and Sanofi shared co-promotion rights and profits and losses on sales of ZALTRAP outside of Japan, and the Company was entitled to receive a percentage of sales of ZALTRAP in Japan. Sanofi commenced sales of ZALTRAP (ziv-aflibercept) Injection for Intravenous Infusion, in combination with 5-fluorouracil, leucovorin, irinotecan ("FOLFIRI"), for patients with metastatic colorectal cancer ("mCRC") that is resistant to or has progressed following an oxaliplatin-containing regimen, in the United States in 2012 and in certain European and other countries in 2013. In February 2015, the Company and Sanofi entered into an amended and restated ZALTRAP agreement ("Amended ZALTRAP Agreement"), with an effective date of July 1, 2014. Under the terms of the Amended ZALTRAP Agreement, Sanofi is solely responsible for the development and commercialization of ZALTRAP for cancer indications worldwide. Sanofi bears the cost of all development and commercialization activities and reimburses Regeneron for its costs for any such activities. Sanofi pays the Company a percentage of aggregate net sales of ZALTRAP during each calendar year, which percentage shall be from 15% to 30% , depending on the aggregate net sales of ZALTRAP in such calendar year. The Company will also be paid for all quantities of ZALTRAP manufactured by it, pursuant to a supply agreement, through the earlier of 2021 or the date Sanofi receives regulatory approval to manufacture ZALTRAP at one of its facilities, or a facility of a third party. In addition, Regeneron no longer has a contingent contractual obligation to reimburse Sanofi for 50% of the development expenses that Sanofi previously funded for the development of ZALTRAP under the ZALTRAP Collaboration Agreement. Unless terminated earlier in accordance with its provisions, the Amended ZALTRAP Agreement will continue to be in effect until such time as neither Sanofi nor its affiliates or sublicensees is developing or commercializing ZALTRAP. As a result of entering into the Amended ZALTRAP Agreement, in the first quarter of 2015, the Company recognized $14.9 million of collaboration revenue, which was previously recorded as deferred revenue under the ZALTRAP Collaboration Agreement, related to (i) amounts that were previously reimbursed by Sanofi for manufacturing commercial supplies of ZALTRAP since the risk of inventory loss no longer existed, and (ii) the unamortized portion of up-front payments from Sanofi as the Company had no further performance obligations. In addition, during the year ended December 31, 2015, the Company recorded $38.8 million , in other revenue, primarily related to (i) revenues earned from Sanofi based on a percentage of net sales of ZALTRAP and (ii) revenues earned from Sanofi for manufacturing ZALTRAP commercial supplies. b. Bayer HealthCare LLC The Company and Bayer HealthCare globally collaborate on the development and commercialization of EYLEA outside of the United States. The Company and Bayer HealthCare share the costs of the development of EYLEA. Bayer HealthCare commenced sales of EYLEA outside the United States for the treatment of wet AMD in 2012, macular edema secondary to CRVO in 2013, visual impairment due to DME in the third quarter of 2014, mCNV (in Japan) in the fourth quarter of 2014, and macular edema following BRVO in the second quarter of 2015. Bayer HealthCare markets EYLEA outside the United States, where, for countries other than Japan, the Company and Bayer HealthCare will share equally in profits and losses from sales of EYLEA. The Company is entitled to receive a percentage of between 33.5% and 40.0% of EYLEA annual sales in Japan. Within the United States, the Company is responsible for commercialization of EYLEA and retains exclusive rights to all profits from such commercialization in the United States. In 2014, the Company entered into a license and collaboration agreement with Bayer HealthCare governing the joint development and commercialization outside the United States of an antibody product candidate to Platelet Derived Growth Factor Receptor Beta (PDGFR-beta). The collaboration revenue the Company earned from Bayer HealthCare is detailed below: Year Ended December 31, Bayer HealthCare Collaboration Revenue 2015 2014 2013 EYLEA: Regeneron's net profit in connection with commercialization of EYLEA outside the United States $ 466,667 $ 301,302 $ 101,494 Sales and substantive development milestones 15,000 105,000 70,000 Cost-sharing of Regeneron EYLEA development expenses 8,887 23,383 20,905 Other 69,466 52,390 27,890 Total EYLEA 560,020 482,075 220,289 PDGFR-beta antibody: Cost-sharing of REGN2176-3 development expenses 10,075 2,848 — Other 10,393 10,632 — Total PDGFR-beta 20,468 13,480 — $ 580,488 $ 495,555 $ 220,289 Other selected financial information in connection with the Company's collaboration agreements with Bayer HealthCare is as follows: December 31, 2015 2014 EYLEA: Accounts receivable, net $ 160,755 $ 124,293 Deferred revenue 46,694 28,752 PDGFR-beta antibody: Accounts receivable, net $ 1,397 $ 1,191 Deferred revenue 9,522 19,909 EYLEA outside the United States In October 2006, the Company entered into a license and collaboration agreement with Bayer HealthCare for the global development and commercialization outside the United States of EYLEA. Under the terms of the agreement, Bayer HealthCare made a non-refundable up-front payment to the Company of $75.0 million . The Company also received from Bayer HealthCare a $20.0 million development milestone payment in 2007 (which, for the purpose of revenue recognition, was not considered substantive). The $75.0 million up-front payment and the $20.0 million milestone payment are being recognized as collaboration revenue over the related estimated performance period in accordance with the Company's revenue recognition policy as described in Note 1. Since 2009, all agreed-upon EYLEA development expenses incurred by the Company and Bayer HealthCare, under a global development plan, are being shared equally. The Company is also obligated to use commercially reasonable efforts to supply clinical and commercial bulk product of EYLEA. Bayer HealthCare has the right to terminate the license and collaboration agreement without cause with at least six months' or twelve months' advance notice depending on defined circumstances at the time of termination. In the event of termination of the agreement for any reason, the Company retains all rights to EYLEA. The Company is obligated to reimburse Bayer HealthCare out of its share of the collaboration profits (including the Company's percentage of sales of EYLEA in Japan) for 50% of the agreed-upon development expenses that Bayer HealthCare has incurred in accordance with a formula based on the amount of development expenses that Bayer HealthCare has incurred and the Company's share of the collaboration profits, or at a faster rate at the Company's option. The Company's contingent reimbursement obligation to Bayer HealthCare was approximately $258 million as of December 31, 2015. In 2013, the Company earned a $15.0 million and a $10.0 million substantive milestone payment related to marketing and pricing approval, respectively, of EYLEA for the treatment of macular edema secondary to CRVO. In addition, in 2013, the Company earned, and recorded as revenue, $45.0 million of sales milestone payments from Bayer HealthCare upon total aggregate net sales of EYLEA outside the United States achieving certain specified levels starting at $200 million over a twelve -month period. In 2014, the Company earned, and recorded as revenue, $90.0 million of sales milestone payments from Bayer HealthCare upon total aggregate net sales of EYLEA outside the United States achieving certain specified levels starting at $500 million over a twelve -month period. In addition, in connection with a November 2013 agreement under which Bayer HealthCare obtained rights to use certain of the Company's EYLEA clinical data for a regulatory filing, the Company earned, and recorded as revenue, a $15.0 million sales milestone payment in 2014 from Bayer HealthCare upon total aggregate net sales of specific commercial supplies of EYLEA outside the United States exceeding $100 million over a twelve -month period. In 2015, the Company earned, and recorded as revenue, the final sales milestone payment from Bayer HealthCare, in the amount of $15.0 million , upon total aggregate net sales of specific commercial supplies of EYLEA outside the United States exceeding $200 million over a twelve -month period. In January 2014, Bayer HealthCare decided to participate in the global development and commercialization of EYLEA outside the United States for the treatment of macular edema following BRVO. In connection with this decision, Bayer HealthCare reimbursed Regeneron $15.7 million for a defined share of the EYLEA global development costs that the Company had incurred prior to February 2014 for the BRVO indication, which was recognized as Bayer HealthCare collaboration revenue in the first quarter of 2014 and is included with "Cost-sharing of Regeneron EYLEA development expenses" in the table above. In addition, all future agreed upon global EYLEA development expenses incurred in connection with BRVO are being shared equally, and any profits or losses on sales of EYLEA outside of the United States for the treatment of macular edema following BRVO are also shared (for countries other than Japan). The Company is entitled to receive a tiered percentage of EYLEA net sales in Japan. In periods when Bayer HealthCare incurs agreed-upon EYLEA development expenses that benefit the collaboration and Regeneron, the Company recognizes, as additional research and development expense, the portion of Bayer HealthCare's EYLEA development expenses that the Company is obligated to reimburse. In 2015, 2014, and 2013, the Company recognized as research and development expense $13.7 million , $18.6 million , and $15.3 million , respectively, of EYLEA development expenses that the Company was obligated to reimburse to Bayer HealthCare. PDGFR-beta antibody outside the United States In January 2014, the Company entered into an agreement with Bayer HealthCare governing the joint development and commercialization outside the United States of an antibody product candidate to PDGFR-beta, including in combination with aflibercept, for the treatment of ocular diseases or disorders. REGN2176-3, a combination product candidate comprised of an antibody to PDGFR-beta co-formulated with aflibercept, is being developed under the agreement. Under the agreement, the Company will conduct the initial development of the PDGFR-beta antibody through completion of the first proof-of-concept study, upon which Bayer HealthCare will have a right to opt-in to license and collaborate on further development and commercialization outside the United States. In connection with the agreement, Bayer HealthCare made a $25.5 million non-refundable up-front payment to the Company in January 2014, and is obligated to pay 25% of global development costs and 50% of development costs exclusively for the territory outside the United States under the initial development plan. In addition, Bayer HealthCare is obligated to reimburse the Company for 50% of development milestone payments to Sanofi related to the Company's acquisition of rights to antibodies targeting the PDGF family of receptors in May 2013. In that regard, Bayer HealthCare made two $2.5 million development milestone payments to the Company in 2014 (both of which, for the purpose of revenue recognition, were not considered substantive) and a $5.0 million development milestone payment to the Company in 2015 (which was recognized as a substantive milestone). The Company is eligible to receive a $10.0 million additional future development milestone payment from Bayer HealthCare, although this payment could be reduced by half i

Technology Licensing Agreements

Technology Licensing Agreements	12 Months Ended
	Dec. 31, 2015
Technology Licensing Agreements [Abstract]
Technology Licensing Agreements	Technology Licensing Agreement In March 2007, the Company entered into a six -year, non-exclusive license agreement with Astellas Pharma Inc. to allow Astellas to utilize the Company's VelocImmune technology in its internal research programs to discover human monoclonal antibodies. In July 2010, the license agreement with Astellas was amended and extended through June 2023. Under the terms of the amended agreement, Astellas made a $165.0 million up-front payment to the Company in August 2010, which was deferred upon receipt and is being recognized as revenue ratably over the seven -year period beginning in mid-2011. In addition, Astellas will make a $130.0 million second payment to the Company in June 2018 unless the license agreement has been terminated prior to that date. Astellas has the right to terminate the agreement at any time by providing 90 days' advance written notice. Under certain limited circumstances, such as a material breach of the agreement by the Company, Astellas may terminate the agreement and receive a refund of a portion of its up-front payment or, if such termination occurs after June 2018, a portion of its second payment, to the Company under the July 2010 amendment to the agreement. The Company is entitled to receive a mid-single digit royalty on any future sales of antibody products discovered by Astellas using the Company's VelocImmune technology. In connection with the Astellas license agreement, for each of the years ended December 31, 2015, 2014, and 2013, the Company recognized $23.6 million of other revenue. In addition, deferred revenue at December 31, 2015 and 2014 was $57.4 million and $81.0 million , respectively.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Marketable securities as of December 31, 2015 and 2014 consist of both debt securities of investment grade issuers as well as equity securities. The Company also held restricted marketable securities as of December 31, 2014, consisting of the Company's investment in Avalanche Biotechnologies, Inc. common shares, which were subject to customary transfer restrictions until January 2015 under a lock-up agreement with the underwriters of Avalanche's initial public offering. The following tables summarize the Company's investments in marketable securities: Amortized Unrealized Fair As of December 31, 2015 Cost Basis Gains Losses Value Unrestricted Corporate bonds $ 770,092 $ 156 $ (2,565 ) $ 767,683 U.S. government and government agency obligations 51,402 — (193 ) 51,209 Municipal bonds 17,930 5 (11 ) 17,924 Equity securities 17,005 14,461 — 31,466 $ 856,429 $ 14,622 $ (2,769 ) $ 868,282 As of December 31, 2014 Unrestricted Corporate bonds $ 548,832 $ 136 $ (1,462 ) $ 547,506 U.S. government and government agency obligations 28,596 3 (46 ) 28,553 Municipal bonds 37,044 37 (43 ) 37,038 Equity securities 2,005 5,374 — 7,379 616,477 5,550 (1,551 ) 620,476 Restricted Equity securities 15,000 76,439 — 91,439 $ 631,477 $ 81,989 $ (1,551 ) $ 711,915 The Company classifies its debt security investments based on their contractual maturity dates. The debt securities listed as of December 31, 2015 mature at various dates through August 2020. The fair values of debt security investments by contractual maturity consist of the following: As of December 31, 2015 2014 Maturities within one year $ 236,121 $ 251,761 Maturities after one year through five years 600,695 360,208 Maturities after five years through ten years — 1,128 $ 836,816 $ 613,097 The following table shows the fair value of the Company's marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position. Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 668,199 $ (2,473 ) $ 23,749 $ (92 ) $ 691,948 $ (2,565 ) U.S. government and government agency obligations 51,215 (193 ) — — 51,215 (193 ) Municipal bonds 11,917 (11 ) — — 11,917 (11 ) $ 731,331 $ (2,677 ) $ 23,749 $ (92 ) $ 755,080 $ (2,769 ) As of December 31, 2014 Corporate bonds $ 390,613 $ (1,462 ) — — $ 390,613 $ (1,462 ) U.S. government and government agency obligations 25,549 (46 ) — — 25,549 (46 ) Municipal bonds 10,779 (43 ) — — 10,779 (43 ) $ 426,941 $ (1,551 ) — — $ 426,941 $ (1,551 ) During the year ended December 31, 2013, the Company recorded an other-than-temporary impairment charge of $2.9 million related to its investment in an equity security. There were no other-than-temporary impairment charges recorded on the Company's investments during 2015 or 2014. Realized gains and losses are included as a component of investment income. For the year ended December 31, 2015, total realized gains and losses were not material. For the year ended December 31, 2014, total realized gains on sales of marketable securities were $1.2 million , and there were no realized losses. For the year ended December 31, 2013, total realized gains on sales of marketable securities were $1.0 million , and there were no realized losses. Changes in the Company's accumulated other comprehensive income (loss) for the years ended December 31, 2015, 2014, and 2013 related to unrealized gains and losses on available-for-sale marketable securities. For the years ended December 31, 2015, 2014, and 2013, amounts reclassified from accumulated other comprehensive income (loss) into investment income in the Company's Statements of Operations were related to the 2013 impairment charge on the equity security, and realized gains and losses on sales of marketable securities described above.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company's assets that are measured at fair value on a recurring basis consist of the following: Fair Value Measurements at Reporting Date Using As of December 31, 2015 Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Available-for-sale marketable securities: Unrestricted Corporate bonds $ 767,683 — $ 767,683 U.S. government and government agency obligations 51,209 — 51,209 Municipal bonds 17,924 — 17,924 Equity securities 31,466 $ 31,466 — $ 868,282 $ 31,466 $ 836,816 As of December 31, 2014 Available-for-sale marketable securities: Unrestricted Corporate bonds $ 547,506 — $ 547,506 U.S. government and government agency obligations 28,553 — 28,553 Municipal bonds 37,038 — 37,038 Equity securities 7,379 $ 7,379 — 620,476 7,379 613,097 Restricted Equity securities 91,439 — 91,439 $ 711,915 $ 7,379 $ 704,536 Marketable securities included in Level 2 are valued using quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, or model-based valuations in which significant inputs used are observable. The Company considers market liquidity in determining the fair value for these securities. The Company did no t record any charges for other-than-temporary impairment of its Level 2 marketable securities in 2015 , 2014 , and 2013 . There were no purchases, sales, or maturities of Level 3 marketable securities and no unrealized gains or losses related to Level 3 marketable securities for the years ended December 31, 2015 and 2014. During 2015, transfers of marketable securities from Level 2 to Level 1 were $91.4 million in connection with the lapse of the transfer restrictions on the Company's investment in Avalanche common shares in January 2015. The Company's policy for recognition of transfers between levels of the fair value hierarchy is to recognize any transfer at the beginning of the fiscal quarter in which the determination to transfer was made. There were no other transfers of marketable securities between Levels 1, 2, or 3 classifications during the year ended December 31, 2015, and there were no transfers of marketable securities between Levels 1, 2, or 3 classifications during the year ended December 31, 2014. As of December 31, 2015 and 2014 , the Company had $11.2 million and $169.4 million , respectively, in aggregate principal amount of 1.875% convertible senior notes outstanding. See Note 11. The fair value of the outstanding convertible senior notes was estimated to be $72.8 million and $819.8 million as of December 31, 2015 and 2014 , respectively, and was determined based on Level 2 inputs, such as market and observable sources.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2015
Inventory Disclosure [Abstract]
Inventory	Inventories Inventories consist of the following: As of December 31, 2015 2014 Raw materials $ 59,151 $ 10,923 Work-in-process 132,068 73,519 Finished goods 11,197 10,768 Deferred costs 36,162 33,651 $ 238,578 $ 128,861 Deferred costs represent the costs of product manufactured and shipped to the Company's collaborators for which recognition of revenue has been deferred (see Note 1). In 2015 , 2014 , and 2013 , cost of goods sold included inventory write-downs and reserves totaling $10.6 million , $6.0 million , and $9.1 million , respectively.

Property, Plant, and Equipment

Property, Plant, and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant, and Equipment Property, plant, and equipment consist of the following: As of December 31, 2015 2014 Land $ 77,826 $ 2,768 Building and improvements 760,517 398,981 Leasehold improvements 95,226 42,600 Construction-in-progress 579,834 472,231 Laboratory and other equipment 330,432 253,058 Furniture, computer and office equipment, and other 81,381 58,655 1,925,216 1,228,293 Less, accumulated depreciation and amortization (331,096 ) (253,984 ) $ 1,594,120 $ 974,309 As of December 31, 2015 and 2014, $1,118.4 million and $754.7 million , respectively, of the Company's property, plant, and equipment was located in the United States and $475.7 million and $219.6 million , respectively, was located in Ireland. In 2015, the Company acquired an approximate 100-acre parcel of undeveloped land adjacent to the Company's current Tarrytown, New York location for an aggregate purchase price of $73.0 million . Depreciation and amortization expense on property, plant, and equipment amounted to $74.9 million , $52.7 million , and $41.2 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. Property, plant, and equipment, at cost, as of December 31, 2015 and 2014 included $254.6 million and $236.7 million , respectively, of costs incurred by the Company's landlord to construct laboratory and office facilities in Tarrytown, New York. See Note 12a.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following: As of December 31, 2015 2014 Accounts payable $ 140,962 $ 99,508 Accrued payroll and related costs 133,223 92,778 Accrued clinical trial expense 88,297 41,555 Accrued sales-related charges, deductions, and royalties 195,986 133,085 Other accrued expenses and liabilities 85,644 116,563 $ 644,112 $ 483,489

Deferred Revenue

Deferred Revenue	12 Months Ended
	Dec. 31, 2015
Deferred Revenue Disclosure [Abstract]
Deferred Revenue	Deferred Revenue Deferred revenue consists of the following: As of December 31, 2015 2014 Current portion: Received or receivable from Sanofi (see Note 3a) $ 101,573 $ 15,927 Received or receivable from Bayer HealthCare (see Note 3b) 24,290 33,652 Received for technology license agreement (see Note 4) 23,572 23,572 Other 4,052 874 $ 153,487 $ 74,025 Long-term portion: Received or receivable from Sanofi (see Note 3a) $ 582,664 $ 62,819 Received or receivable from Bayer HealthCare (see Note 3b) 31,926 15,007 Received for technology license agreement (see Note 4) 33,851 57,423 Other 16,238 — $ 664,679 $ 135,249

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Convertible Debt	Debt a. Convertible Debt In October 2011, the Company issued $400.0 million aggregate principal amount of 1.875% convertible senior notes (the "Notes") in a private placement. The Notes pay interest semi-annually on April 1 and October 1, and will mature on October 1, 2016 unless earlier converted (which can occur subject to certain conditions) or repurchased. The Notes are convertible, subject to certain conditions, into cash, shares of the Company's Common Stock, or a combination of cash and shares of Common Stock, at the Company's option. The Notes initial conversion price is approximately $84.02 per share. In the event that a fundamental change, as defined in the indenture under which the Notes have been issued, occurs prior to maturity of the Notes, the initial conversion rate may be increased to include additional shares upon conversion, or holders can require the Company to purchase from them all or a portion of their Notes for 100% of the principal value plus any accrued and unpaid interest. The Company has reserved sufficient shares of its Common Stock to satisfy the conversion requirements related to the Notes. The Company may not redeem the Notes prior to their maturity date. As of December 31, 2015, the "if converted value" exceeded the principal amount of the Notes by $70.4 million . In accordance with accounting guidance for debt with conversion and other options, the Company accounted for the liability and equity components of the Notes separately. The estimated fair value of the liability component at the date of issuance was $271.1 million , and was computed based on the fair value of similar debt instruments that do not include a conversion feature. The equity component of $120.9 million was recognized as a debt discount and represents the difference between the $392.0 million of gross proceeds from the issuance of the Notes and the $271.1 million estimated fair value of the liability component at the date of issuance. The debt discount is amortized over the expected life of a similar liability without the equity component. The Company determined this expected life to be equal to the term of the Notes, resulting in an amortization period ending October 1, 2016. The effective interest rate used to amortize the debt discount is approximately 10.2% , which was based on the Company's estimated non-convertible borrowing rate as of the date the Notes were issued. In connection with the offering of the Notes in October 2011, the Company entered into convertible note hedge ("call option") and warrant transactions with multiple counterparties, including an affiliate of the initial purchaser of the Notes. The convertible note hedge covers, subject to customary anti-dilution adjustments, the number of shares of the Company's Common Stock that initially underlie the Notes, and are intended to reduce the potential dilutive impact of the conversion feature of the Notes. The convertible note hedge will terminate upon the earlier of the maturity date of the Notes or the first day the Notes are no longer outstanding. The Company paid $117.5 million for the convertible note hedge, which was recorded as a reduction to additional paid-in capital. The warrants have an initial strike price of approximately $103.41 per share, and may be settled in cash or shares of the Company's Common Stock, at the Company's option. The warrants have a dilutive effect to the extent that the market price per share of the Company's Common Stock exceeds the applicable strike price of the warrants. Proceeds received from the warrant transactions totaled $93.8 million and were recorded as additional paid-in capital. The warrants will become exercisable (and, if not exercised, will expire) at various dates during 2017. The original convertible note hedge and warrants were both considered indexed to the Company's Common Stock and classified as equity; therefore, the convertible note hedge and warrants were not accounted for as derivative instruments. The Company has reserved sufficient shares of its Common Stock to satisfy the potential settlement of the warrants. During 2014, $230.6 million principal amount of the Company's $400.0 million aggregate principal amount of Notes was surrendered for conversion, of which $220.6 million was settled prior to December 31, 2014. The Company elected to settle these conversion obligations through a combination of cash, in an amount equal to the principal amount of the converted Notes, and shares of the Company's Common Stock in respect of any amounts due in excess thereof. Consequently, in 2014, the Company paid $220.6 million in cash and issued 2,017,732 shares of Common Stock. In addition, in 2014, the Company allocated $691.9 million of the settlement consideration provided to the Note holders to the reacquisition of the equity component of the Notes, and recognized such amount as a reduction of stockholder's equity, and recognized a $33.5 million loss on the debt extinguishment. During 2015, the Company settled conversion obligations for $166.5 million principal amount of the Company's Notes that was previously surrendered for conversion. In accordance with the terms of the Notes, the Company elected to settle these conversion obligations through a combination of cash, in an amount equal to the principal amount of the converted Notes, and shares of the Company's Common Stock in respect of any amounts due in excess thereof. Consequently, in 2015, the Company paid $166.5 million in cash and issued 1,625,113 shares of Common Stock. In addition, in 2015, the Company allocated $819.7 million of the settlement consideration provided to the Note holders to the reacquisition of the equity component of the Notes and recognized such amount as a reduction of stockholders' equity, and recognized a $18.9 million loss on the debt extinguishment. As of December 31, 2015, an aggregate principal amount of $11.2 million of the original $400.0 million aggregate principal amount of Notes remained outstanding. The net carrying amount of the liability component of the Notes consists of the following: As of December 31, 2015 2014 Total convertible senior notes - par $ 11,154 $ 169,400 Unamortized discount (352 ) (22,627 ) $ 10,802 $ 146,773 The December 31, 2015 net carrying amount of the liability component of the Notes was recorded within other current liabilities within the Company's Balance Sheet since the Notes are due to mature on October 1, 2016. Total interest expense associated with the Notes, net of capitalized interest as applicable (see Note 19), consists of the following: Year Ended December 31, 2015 2014 2013 Contractual coupon interest rate $ 544 $ 5,036 $ 7,230 Amortization of discount and note issuance costs 2,818 17,821 22,980 $ 3,362 $ 22,857 $ 30,210 As a result of the Note conversions described above, the Company also exercised a proportionate amount of its convertible note hedges during 2015 and 2014, for which the Company received 1,625,088 and 2,017,732 shares, respectively, of Common Stock, which was approximately equal to the number of shares the Company was required to issue to settle the non-cash portion of the related Note conversions. The Company recorded the cost of the shares received, or $136.5 million and $169.5 million , respectively, as Treasury Stock during 2015 and 2014. Warrant Transactions In November 2014, the Company entered into an amendment agreement with a warrant holder whereby the parties agreed to reduce a portion of the number of warrants held by the warrant holder by up to a maximum of 493,229 , for an aggregate amount payable by the Company not to exceed $148.5 million . The reduction in the number of warrants was determined based on the number of warrants with respect to which the warrant holder had closed out its hedge position, provided that the warrant holder did not effect any purchases at a price per share exceeding $397.75 per share, during the period starting on November 26, 2014 and ending no later than February 12, 2015. The Company was obligated to settle any payments due under the amendment agreement in February 2015. Given that the amendment agreement contained a conditional obligation that required settlement in cash, and the Company's obligation was indexed to the Company's share price, the Company reclassified the estimated fair value of the 493,229 warrants from additional paid-in capital to a liability in November 2014, with such liability subsequently measured at fair value with changes in fair value recognized in earnings. The change in fair value for the year ended December 31, 2014 resulted in the Company recording a gain of $1.2 million . As a result of the warrant holder closing out a portion of its hedge position prior to December 31, 2014, the Company recorded a $59.8 million accrued liability as of December 31, 2014. The estimated fair value of the remaining liability as of December 31, 2014 was $87.5 million , and was recorded within other current liabilities within the Company's Balance Sheet. During the first quarter of 2015, the warrant holder closed out additional portions of its hedge position, and, as a result, in February 2015 the Company paid a total of $124.0 million to reduce the number of warrants held by such warrant holder by 416,480 . Upon expiration of the November 2014 amended agreement, in the first quarter of 2015, the remaining warrants were re-measured at fair value, and $23.3 million was reclassified back to additional paid-in capital, consistent with the original classification of the warrants under the 2011 issuance. Total losses related to changes in fair value of the warrants during the first quarter of 2015 were not material. During 2014, in addition to the November 2014 warrant agreement described above, the Company entered into agreements to reduce the number of warrants held by the warrant holders. Pursuant to the agreements, the Company paid an aggregate amount of $294.6 million to the warrant holders to reduce the maximum number of shares of Common Stock issuable upon exercise of the warrants by 1,220,745 in the aggregate. In November 2015, the Company entered into an amendment agreement with a warrant holder whereby the parties agreed to reduce a portion of the number of warrants held by the warrant holder by up to a maximum of 476,376 . The reduction in the number of warrants was determined based on the number of warrants with respect to which the warrant holder closed out its hedge position, provided that the warrant holder did not effect any purchases at a price per share exceeding $535.00 per share, during the period starting on November 16, 2015 and ending no later than February 9, 2016 . As a result of the warrant holder closing out a portion of its hedge position prior to December 31, 2015, the Company paid a total of $50.0 million in 2015 to reduce the number of warrants it held by 115,970 . Additionally, during January 2016, the warrant holder closed out additional portions of its hedge position, and, as a result, the Company paid a total of $135.3 million to further reduce the number of warrants held by such warrant holder by 360,406 (which was the remaining maximum number of warrants to be reduced subject to the amendment agreement). In addition to the warrant transactions described above, during 2015, the Company entered into other agreements to reduce the number of warrants held by warrant holders. Pursuant to the agreements, the Company paid an aggregate amount of $399.5 million to the warrant holders during 2015 to reduce the number of shares of Common Stock issuable upon exercise of the warrant by 898,547 in the aggregate. As of December 31, 2015, an aggregate of 2,109,098 warrants (subject to adjustment from time to time as provided in the applicable warrant agreements) remained outstanding. b. Credit Facility In March 2015, the Company entered into an agreement with a syndicate of lenders (the "Credit Agreement") which provides for a $750.0 million senior unsecured five -year revolving credit facility (the "Credit Facility"). The Credit Agreement includes an option for the Company to elect to increase the commitments under the Credit Facility and/or to enter into one or more tranches of term loans in the aggregate principal amount of up to $250.0 million subject to the consent of the lenders providing the additional commitments or term loans, as applicable, and certain other conditions. Proceeds of the loans under the Credit Facility may be used to finance working capital needs, and for general corporate or other lawful purposes, of Regeneron and its subsidiaries. The Credit Agreement also provides a $100.0 million sublimit for letters of credit. The Credit Agreement includes an option for the Company to elect to extend the maturity date of the Credit Facility beyond March 2020, subject to the consent of the extending lenders and certain other conditions. Amounts borrowed under the Credit Facility may be prepaid, and the commitments under the Credit Facility may be terminated, at any time without premium or penalty. Any loans under the Credit Facility have a variable interest rate based on either the London Interbank Offered Rate ("LIBOR") or an alternate base rate, plus an applicable margin that varies with the Company's debt rating and total leverage ratio. The Company had no borrowings outstanding under the Credit Facility as of December 31, 2015. The Credit Agreement contains financial and operating covenants. Financial covenants include a maximum total leverage ratio and a minimum interest expense coverage ratio. The Company was in compliance with all covenants of the Credit Facility as of December 31, 2015.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies a. Leases Descriptions of Lease Agreements The Company leases laboratory and office facilities in Tarrytown, New York. The facilities leased by the Company in Tarrytown include (i) space in previously existing buildings, (ii) newly constructed space in two buildings ("Buildings A and B") that was completed in 2009, (iii) newly constructed space in a third building ("Building C") that was completed in 2011 and, (iv) under an April 2013 lease agreement, newly constructed laboratory and office space in two buildings ("Buildings D and E") that was completed in the third quarter of 2015. The lease agreements related to Buildings A, B, C, D, and E (collectively, the "Buildings") will expire in 2029; the remaining facilities under lease will expire in June 2024. The Tarrytown leases contain renewal options to extend the term of the lease, escalations at 2.5% per annum, and early termination options for various portions of the space. The leases provide for monthly payments over their respective terms (which, for Buildings A, B, C, D, and E were largely based on the landlord's cost of construction and tenant allowances) and additional charges for utilities, taxes, and operating expenses. Certain premises under the Tarrytown lease are accounted for as operating leases. However, as described further below under " Facility Lease Obligations ," for the Buildings that the Company is leasing, the Company is deemed, in substance, to be the owner of the landlord's Buildings in accordance with the application of FASB authoritative guidance. The Company also leases certain other laboratory, office, and storage space and equipment under operating leases which expire at various times through 2022. Commitments under Operating Leases The estimated future minimum noncancelable lease commitments under operating leases, as of December 31, 2015, are as follows: Facilities Equipment Total 2016 $ 10,894 $ 4,594 $ 15,488 2017 11,332 425 11,757 2018 11,607 140 11,747 2019 11,740 — 11,740 2020 11,375 — 11,375 Thereafter 50,746 — 50,746 $ 107,694 $ 5,159 $ 112,853 Rent expense under operating leases was: Year Ended December 31, Facilities Equipment Total 2015 $ 14,659 $ 543 $ 15,202 2014 13,360 952 14,312 2013 9,404 471 9,875 In addition to its rent expense under operating leases for various facilities, the Company paid rental charges for utilities, real estate taxes, and operating expenses of $15.5 million , $13.6 million , and $11.5 million for the years ended December 31, 2015, 2014, and 2013, respectively. Facility Lease Obligations Based upon various factors, including the Company's involvement in the construction of the Buildings and its responsibility for directly paying for a substantial portion of tenant improvements, the Company is deemed, in substance, to be the owner of the landlord's Buildings in accordance with the application of FASB authoritative guidance. Consequently, in addition to capitalizing the tenant improvements, the Company capitalizes the landlord's costs of constructing these new facilities, offset by a corresponding lease obligation on the Company's Balance Sheet. The Company also recognizes, as additional facility lease obligation, reimbursements from the Company's landlord for tenant improvement costs that the Company incurred since such payments that the Company receives from its landlord are deemed to be a financing obligation. The Company allocates a portion of its lease payments on these facilities between the Buildings and the land on which the Buildings are constructed, based on the initial estimated relative fair values of the land and Buildings. The land element of the lease is treated for accounting purposes as an operating lease. With respect to Buildings A and B, in 2009, monthly lease payments commenced and the buildings were placed in service by the Company. The imputed interest rate applicable to the Company's Buildings A and B facility lease obligation is approximately 11% . With respect to Building C, in 2011, monthly lease payments commenced and the building was placed in service by the Company. The imputed interest rate applicable to the Company's Building C facility lease obligation is approximately 10% . With respect to Buildings D and E, in 2015, monthly lease payments commenced and the buildings were placed in service by the Company. The imputed interest rate applicable to the Company's Buildings D and E facility lease obligation is approximately 7% . In 2015, 2014, and 2013, the Company recognized $9.7 million , $14.5 million , and $16.2 million , respectively, of interest expense in connection with the Buildings' facility lease obligations. Facility lease obligations consist of the following: As of December 31, 2015 2014 Buildings A and B $ 108,857 $ 110,210 Building C 49,475 49,312 Buildings D and E 206,376 152,770 $ 364,708 $ 312,292 The estimated future minimum noncancelable commitments under these facility lease obligations, as of December 31, 2015, are as follows: Buildings A and B Building C Buildings D and E Total 2016 $ 13,809 $ 4,688 $ 12,679 $ 31,176 2017 14,079 4,818 13,016 31,913 2018 14,356 4,951 13,360 32,667 2019 14,640 5,088 13,714 33,442 2020 14,931 5,227 14,076 34,234 Thereafter 117,096 54,760 137,079 308,935 $ 188,911 $ 79,532 $ 203,924 $ 472,367 b. Research Collaboration and Licensing Agreements As part of the Company's research and development efforts, the Company enters into research collaboration and licensing agreements with other companies and universities. These agreements contain varying terms and provisions which include fees to be paid by the Company, services to be provided, and license rights to certain proprietary technology developed under the agreements. Some of these agreements may require the Company to pay additional amounts upon the achievement of various development and commercial milestones, contingent upon the occurrence of various future events. Additionally, some of the agreements contain provisions which require the Company to pay royalties, as defined, at rates that range from 0.5% to 16.5% , in the event the Company sells or licenses any proprietary products developed under the respective agreements. The Company also has contingent reimbursement obligations to its collaborators Sanofi and Bayer HealthCare once the applicable collaboration becomes profitable. See Note 3 for additional information. In December 2011, the Company and Genentech, a member of the Roche Group, entered into a Non-Exclusive License and Partial Settlement Agreement (the "Original Genentech Agreement") that covered making, using, and selling EYLEA for the prevention of human eye diseases and disorders in the United States, and ended the litigation relating to those matters. Pursuant to the Original Genentech Agreement, the Company received a non-exclusive license to certain patents relating to VEGF receptor proteins, known as the Davis-Smyth patents, and other technology patents. The Original Genentech Agreement provided for the Company to make payments to Genentech based on U.S. sales of EYLEA commencing upon FDA approval of EYLEA in November 2011 through May 7, 2016. The Company made a one-time, non-refundable $60.0 million payment during 2012 upon cumulative U.S. sales of EYLEA reaching $400 million , and is obligated to pay royalties of 4.75% on cumulative U.S. sales of EYLEA between $400 million and $3 billion and 5.5% on any cumulative U.S sales of EYLEA over $3 billion . As the Company records net product sales of EYLEA, the Company is recognizing expense in connection with the Genentech Agreement using a blended mid-single digit royalty rate that reflects both the $60.0 million payment and the royalties payable on cumulative sales and that is based upon the Company's estimate of cumulative EYLEA sales through May 7, 2016. Effective May 17, 2013, the Company entered into an Amended and Restated Non-Exclusive License and Settlement Agreement with Genentech (the "Amended Genentech Agreement"), which amended the Original Genentech Agreement to include all sales of EYLEA worldwide and ended the litigation relating to those matters. Under the Amended Genentech Agreement, the Company received a worldwide non-exclusive license to the Davis-Smyth patents, and certain other patents, owned or co-owned by Genentech for the prevention or treatment of eye diseases and eye disorders in a human through administration of EYLEA to the eye. Under the Amended Genentech Agreement, the Company is obligated to make payments to Genentech based on sales of EYLEA in the United States, and EYLEA manufactured in the United States and sold outside the United States, through May 7, 2016 using the same milestone and royalty rates as in the Original Genentech Agreement. EYLEA is sold outside the United States by affiliates of Bayer HealthCare under the Company's license and collaboration agreement. All payments to Genentech under the Original Genentech Agreement and the Amended Genentech Agreement have been or will be made by the Company. Bayer HealthCare shares in all such payments based on the proportion of EYLEA sales outside the United States to worldwide EYLEA sales and determined consistent with the license and collaboration agreement. The Company recognizes royalty expense based on product sales of commercial products under various licensing agreements, including, for EYLEA sales both inside and outside of the United States, the Genentech agreements described above. For the years ended December 31, 2015, 2014, and 2013, the Company recorded royalty expense of $247.9 million , $169.9 million , and $128.1 million , respectively.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity The Company's Restated Certificate of Incorporation, as amended, provides for the issuance of up to 40 million shares of Class A Stock, par value $0.001 per share, and 320 million shares of Common Stock (increased from 160 million shares effective upon shareholder approval obtained in 2015), par value $0.001 per share. Shares of Class A Stock are convertible, at any time, at the option of the holder into shares of Common Stock on a share-for-share basis. Holders of Class A Stock have rights and privileges identical to Common Stockholders except that each share of Class A is entitled to ten votes per share , while each share of Common Stock is entitled to one vote per share . Class A Stock may only be transferred to specified Permitted Transferees, as defined. Under the Company's Restated Certificate of Incorporation, the Company's board of directors is authorized to issue up to 30 million shares of preferred stock, in series, with rights, privileges, and qualifications of each series determined by the board of directors. In December 2007, Sanofi purchased 12 million newly issued, unregistered shares of the Company's Common Stock. As a condition to the closing of this transaction, Sanofi entered into an investor agreement, as amended and restated in January 2014, with the Company. Under the terms of the amended and restated investor agreement, Sanofi has three demand rights to require the Company to use all reasonable efforts to conduct a registered underwritten public offering with respect to shares of the Company's Common Stock held by Sanofi from time to time. Under the amended and restated investor agreement, Sanofi has also agreed not to dispose of any shares of the Company's Common Stock beneficially owned by Sanofi from time to time until the later of (i) December 20, 2020, and (ii) the expiration of the Antibody Discovery Agreement with Sanofi, as amended (see Note 3a) if the agreement is extended beyond December 20, 2020. These restrictions on dispositions are subject to earlier termination upon the occurrence of certain events, such as the consummation of a change-of-control transaction involving the Company or the Company's dissolution or liquidation, and certain restrictions have been imposed on the manner of sales thereafter. Further, pursuant to the amended and restated investor agreement, Sanofi is bound by certain "standstill" provisions, which contractually prohibit Sanofi from seeking to directly or indirectly exert control of the Company or acquiring more than 30% of the outstanding shares of the Company's Class A Stock and Common Stock (taken together). This prohibition will remain in place until the earliest of (i) the later of the fifth anniversaries of the expiration or earlier termination of the Company's License and Collaboration Agreement with Sanofi and the Company's ZALTRAP Agreement with Sanofi, each as amended (see Note 3a) and (ii) other specified events. Sanofi has also agreed to vote as recommended by the Company's board of directors, except that it may elect to vote proportionally with the votes cast by all of the Company's other shareholders with respect to certain change-of-control transactions, and to vote in its sole discretion with respect to liquidation or dissolution, stock issuances equal to or exceeding 20% of the then outstanding shares or voting rights of the Company's Class A Stock and Common Stock (taken together), and new equity compensation plans or amendments if not materially consistent with the Company's historical equity compensation practices. The rights and restrictions under the investor agreement are subject to termination upon the occurrence of certain events. In addition, upon Sanofi reaching 20% ownership of the Company's then outstanding shares of Class A Stock and Common Stock (taken together) during 2014, the Company was required to appoint an individual agreed upon by the Company and Sanofi to the Company's board of directors. This individual is required to be independent of the Company, and not to be a current or former officer, director, employee, or paid consultant of Sanofi. In October 2011, the Company completed a private placement of $400.0 million aggregate principal amount of Notes, which are convertible into shares of the Company's Common Stock. In connection with the offering of the Notes in October 2011, the Company entered into convertible note hedge and warrant transactions. During 2015 and 2014, a substantial portion of the Notes were surrendered for conversion. The Company elected to settle these conversion obligations through a combination of cash, in an amount equal to the principal amount of the converted Notes, and shares of the Company's Common Stock in respect of any amounts due in excess thereof. A portion of the settlement consideration provided to the Note holders was allocated to the reacquisition of the equity component of the Notes. In addition, as a result of the Note conversions, the Company exercised a proportionate amount of its convertible note hedges, for which the Company received shares of Common Stock. The shares received were recorded as Treasury Stock, at cost. See Note 11. During 2015 and 2014, the Company entered into agreements to reduce the number of warrants held by warrant holders. Pursuant to the agreements, the Company made payments to the warrant holders to reduce the maximum number of shares of Common Stock issuable upon the exercise of the warrants by warrant holders. In addition, in November 2014, the Company entered into an amendment agreement with a warrant holder whereby the parties agreed to reduce a portion of the number of warrants held by the warrant holder. Given that the November 2014 amendment agreement contained a conditional obligation that required settlement in cash, and the Company's obligation was indexed to the Company's share price, the Company reclassified the estimated fair value of the warrants from additional paid-in capital to a liability in November 2014. See Note 11. In connection with the Company's January 2014 license and collaboration agreement with Bayer HealthCare for the joint development and commercialization outside the United States of antibody product candidates to PDGFR-beta (see Note 3b), Bayer HealthCare has also agreed to a "standstill" provision, which prohibits Bayer HealthCare and its affiliates from seeking to influence the control of the Company or acquiring more than 20% of the Company's then outstanding shares of Class A Stock and Common Stock (taken together).

Long-Term Incentive Plans

Long-Term Incentive Plans	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Long-Term Incentive Plans	Long-Term Incentive Plans During 2000, the Company established the Regeneron Pharmaceuticals, Inc. 2000 Long-Term Incentive Plan which, as amended and restated and approved by the Company's shareholders (the "2000 Incentive Plan"), provided for the issuance of up to 35,397,043 shares of Common Stock in respect of awards, in addition to any shares subject to awards that were returned to the 2000 Incentive Plan upon expiration, forfeiture, surrender, exchange, cancellation, or termination of previously granted awards. During 2014, the Company established, and the Company's shareholders approved, the Regeneron Pharmaceuticals, Inc. 2014 Long-Term Incentive Plan (the "2014 Incentive Plan"). As of the shareholder approval date, the 2014 Incentive Plan provides for the issuance of up to 16,485,333 shares of Common Stock in respect of awards (including 4,485,333 shares of Common Stock rolled over into the 2014 Incentive Plan from the 2000 Incentive Plan), which were registered with the Securities and Exchange Commission, in addition to any shares subject to awards under the 2000 Incentive Plan or the 2014 Incentive Plan that are added to the pool of shares available for grant under the 2014 Incentive Plan upon the expiration, forfeiture, surrender, exchange, cancellation, or termination of previously granted awards. Employees of the Company, including officers, and nonemployees, including consultants and nonemployee members of the Company's board of directors (collectively, "Participants"), may receive awards as determined by a committee of independent directors ("Committee"). The awards that may be made under the 2014 Incentive Plan include: (a) Incentive Stock Options ("ISOs") and Nonqualified Stock Options, (b) shares of Restricted Stock, (c) shares of Phantom Stock, (d) Stock Bonuses, and (e) Other Awards. Stock Option awards grant Participants the right to purchase shares of Common Stock at prices determined by the Committee; however, in the case of an ISO, the option exercise price may not be less than the fair market value of a share of Common Stock on the date the option is granted. Options vest over a period of time determined by the Committee, generally on a pro rata basis over a three - to four -year period. The Committee also determines the expiration date of each option; however, no ISO is exercisable more than ten years after the date of grant. The maximum term of options that have been awarded under the 2000 Incentive Plan or 2014 Incentive Plan (collectively, the "Incentive Plans") is ten years. Restricted Stock awards grant Participants shares of restricted Common Stock or allow Participants to purchase such shares at a price determined by the Committee. Such shares are nontransferable for a period determined by the Committee ("vesting period"). Should employment terminate, as specified in the Incentive Plans, except as determined by the Committee in its discretion and subject to the applicable Incentive Plan documents, the ownership of any unvested Restricted Stock will be transferred to the Company. In such an event, the Company will be obligated to repay the Participant the amount, if any, paid by the Participant for such shares. In addition, if the Company requires a return of the Restricted Stock, it also has the right to require a return of all dividends paid on such shares. Phantom Stock awards provide the Participant the right to receive, within 30 days of the date on which the share vests, an amount, in cash and/or shares of Common Stock as determined by the Committee, equal to the sum of the fair market value of a share of Common Stock on the date such share of Phantom Stock vests and the aggregate amount of cash dividends paid with respect to a share of Common Stock during the period from the grant date of the share of Phantom Stock to the date on which the share vests. Stock Bonus awards are bonuses payable in shares of Common Stock which are granted at the discretion of the Committee. Other Awards are other forms of awards which are valued based on the Common Stock. Subject to the provisions of the 2014 Incentive Plan, the terms and provisions of such Other Awards are determined solely on the authority of the Committee. The Incentive Plans contain provisions that allow for the Committee to provide for the immediate vesting of awards upon a change in control of the Company, as defined in the Plans. As of December 31, 2015 , there were 9,711,439 shares available for future grants under the 2014 Incentive Plan. No additional awards may be made under the 2000 Incentive Plan. a. Stock Options Transactions involving stock option awards during 2015 under the Company's Incentive Plans are summarized in the table below. Stock Options: Number of Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Intrinsic Value (in thousands) Outstanding as of December 31, 2014 21,506,260 $ 158.54 2015: Granted 4,495,487 $ 537.29 Forfeited (318,952 ) $ 292.14 Expired (363 ) $ 92.20 Exercised (2,516,663 ) $ 98.26 Outstanding as of December 31, 2015 23,165,769 $ 236.75 6.82 $ 7,209,994,851 Vested and expected to vest as of December 31, 2015 22,635,728 $ 231.75 6.76 $ 7,156,754,651 Exercisable as of December 31, 2015 13,212,236 $ 103.67 5.23 $ 5,852,659,560 The Company satisfies stock option exercises with newly issued shares of the Company's Common Stock. The total intrinsic value of stock options exercised during 2015 , 2014 , and 2013 was $1,031.6 million , $1,081.2 million , and $727.5 million , respectively. The intrinsic value represents the amount by which the market price of the underlying stock exceeds the exercise price of an option. The Company grants stock options with exercise prices that are equal to or greater than the average market price of the Company's Common Stock on the date of grant ("Market Price"). The table below summarizes the weighted-average exercise prices and weighted-average grant-date fair values of options issued during the years ended December 31, 2015 , 2014 , and 2013 . The fair value of each option granted under the Company's Incentive Plans during these periods was estimated on the date of grant using the Black-Scholes option-pricing model. Number of Options Granted Weighted-Average Exercise Price Weighted-Average Fair Value 2015: Exercise price equal to Market Price 4,495,487 $ 537.29 $ 181.65 2014: Exercise price equal to Market Price 3,913,368 $ 385.33 $ 140.38 2013: Exercise price equal to Market Price 3,937,989 $ 263.77 $ 104.90 For the years ended December 31, 2015 , 2014 , and 2013 , the Company recognized $443.7 million , $306.1 million , and $193.4 million , respectively, of non-cash stock-based compensation expense related to non-performance based stock option awards. As of December 31, 2015 , there was $962.6 million of stock-based compensation cost related to outstanding non-performance based stock options, net of estimated forfeitures, which had not yet been recognized. The Company expects to recognize this compensation cost over a weighted-average period of 2.0 years. For the years ended December 31, 2014 and 2013 , the Company recognized $4.1 million and $8.0 million , respectively, of non-cash stock-based compensation expense related to performance-based options. As of December 31, 2013, there were 770,250 performance-based options outstanding and unvested, which were issued in 2011, and fully vested during 2014. The Company has not issued any performance-based options since 2011 and there were no performance-based options that were unvested as of December 31, 2015. Fair Value Assumptions: The following table summarizes the weighted average values of the assumptions used in computing the fair value of option grants during 2015, 2014 and 2013. 2015 2014 2013 Expected volatility 35 % 39 % 42 % Expected lives from grant date 5.1 years 5.2 years 5.3 years Expected dividend yield 0 % 0 % 0 % Risk-free interest rate 1.68 % 1.62 % 1.73 % Expected volatility has been estimated based on actual movements in the Company's stock price over the most recent historical periods equivalent to the options' expected lives. Expected lives are principally based on the Company's historical exercise experience with previously issued employee and board of directors' option grants. The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. The risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the options' expected lives. b. Restricted Stock A summary of the Company's activity related to Restricted Stock awards for the year ended December 31, 2015 is summarized below: Restricted Stock: Number of Shares Weighted-Average Grant Date Fair Value Outstanding as of December 31, 2014 546,060 $ 115.26 2015: Granted 27,520 $ 540.40 Vested (31,880 ) $ 164.65 Outstanding as of December 31, 2015 541,700 $ 133.96 The Company recognized non-cash stock-based compensation expense from Restricted Stock awards of $15.3 million , $11.5 million , and $14.0 million in 2015 , 2014 , and 2013 , respectively. As of December 31, 2015, there was $33.9 million of stock-based compensation cost related to unvested shares of Restricted Stock which had not yet been recognized. The Company expects to recognize this compensation cost over a weighted-average period of 2.1 years. c. Revisions of Previously-Issued Financial Statements During the first quarter of 2015, the Company determined that for certain stock option awards granted to an employee in prior periods, the incorrect requisite service period was utilized in determining the period over which the related compensation expense should have been recorded. Such awards were made as part of the Company's annual employee option grants in December of each applicable year. As a result, compensation expense for the years ended December 31, 2014 and 2013 was understated. These revisions consisted entirely of non-cash adjustments, and therefore had no impact on the Company's previously reported total cash flows from operating activities and total cash flows in its Statements of Cash Flows. The Company evaluated the impact of these items on prior periods, assessing materiality quantitatively and qualitatively, and concluded that the errors were not considered to be material to any previously-issued quarterly or annual financial statements. However, the Company concluded that it would revise the applicable prior period amounts in this filing to reflect the impact of these corrections because the cumulative amount of such corrections was expected to be material to the year ending December 31, 2015. The tables below present the impact of these revisions, including the related tax effect, on the Company's previously-filed financial statements. December 31, 2014 As Previously Reported Adjustments As Revised Balance Sheet Data: Deferred tax assets $ 316,104 $ 22,152 $ 338,256 Total assets 3,871,827 22,152 3,893,979 Additional paid-in capital 2,404,118 60,890 2,465,008 Retained earnings 255,382 (38,738 ) 216,644 Total stockholders' equity 2,542,325 22,152 2,564,477 Total liabilities and stockholders' equity 3,871,827 22,152 3,893,979 Three Months Ended December 31, 2014 (Unaudited) As Previously Reported Adjustments As Revised Consolidated Statement of Operations Data: Selling, general, and administrative $ 143,743 $ 31,564 $ 175,307 Total operating expenses 554,962 31,564 586,526 Income from operations 247,367 (31,564 ) 215,803 Income before income taxes 221,287 (31,564 ) 189,723 Income tax expense 111,111 (11,483 ) 99,628 Net income 110,176 (20,081 ) 90,095 Net income per share - basic $ 1.09 $ (0.20 ) $ 0.89 Net income per share - diluted $ 0.96 $ (0.18 ) $ 0.78 Year Ended December 31, 2014 Year Ended December 31, 2013 As Previously Reported Adjustments As Revised As Previously Reported Adjustments As Revised Consolidated Statement of Operations Data: Selling, general, and administrative $ 504,755 $ 14,512 $ 519,267 $ 329,415 $ 16,978 $ 346,393 Total operating expenses 1,981,126 14,512 1,995,638 1,344,717 16,978 1,361,695 Income from operations 838,431 (14,512 ) 823,919 760,028 (16,978 ) 743,050 Income before income taxes 775,747 (14,512 ) 761,235 713,360 (16,978 ) 696,382 Income tax expense 427,673 (4,564 ) 423,109 288,998 (6,354 ) 282,644 Net income 348,074 (9,948 ) 338,126 424,362 (10,624 ) 413,738 Net income per share - basic $ 3.46 $ (0.10 ) $ 3.36 $ 4.33 $ (0.10 ) $ 4.23 Net income per share - diluted $ 3.07 $ (0.09 ) $ 2.98 $ 3.81 $ (0.09 ) $ 3.72 Year Ended December 31, 2014 Year Ended December 31, 2013 As Previously Reported Adjustments As Revised As Previously Reported Adjustments As Revised Consolidated Statement of Cash Flows Data: Cash flows from operating activities Net income $ 348,074 $ (9,948 ) $ 338,126 $ 424,362 $ (10,624 ) $ 413,738 Non-cash compensation expense 307,238 14,512 321,750 198,399 16,978 215,377 Deferred taxes (66,604 ) (4,564 ) (71,168 ) 63,601 (6,354 ) 57,247

Employee Savings Plan

Employee Savings Plan	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Savings Plan	Employee Savings Plans The Company maintains the Regeneron Pharmaceuticals, Inc. 401(k) Savings Plan (the "Savings Plan"). The terms of the Savings Plan, as amended and restated, allow U.S. employees who are age twenty-one or older to contribute to the Savings Plan a percentage of their compensation. In addition, the Company may make discretionary contributions ("Contribution"), as defined, to the accounts of participants under the Savings Plan. The Company recognized $15.4 million , $13.1 million , and $5.7 million of Contribution expense in 2015, 2014, and 2013, respectively. In 2014, the Regeneron Ireland Pension Plan (the "Ireland Plan"), a defined contribution occupational pension plan which covers all eligible Ireland-based employees (as defined by the Ireland Plan), was established. Contributions to the Ireland Plan are comprised of two components: (i) a minimum mandatory employee and employer contribution rate, and (ii) a matching scheme, whereby the Company will match employee contributions up to a certain percentage. Employees can make additional voluntary contributions to the Ireland Plan. Expenses related to the Company's contributions to the Ireland Plan were not material during 2015 and 2014.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state, and foreign income taxes. Components of income before income taxes consist of the following: Year Ended December 31, 2015 2014 2013 United States $ 1,665,087 $ 1,101,446 $ 795,300 Foreign (439,990 ) (340,211 ) (98,918 ) $ 1,225,097 $ 761,235 $ 696,382 Components of income tax expense consist of the following: Year Ended December 31, 2015 2014 2013 Current: Federal $ 686,561 $ 437,038 $ 196,527 State 28,568 28,718 23,489 Foreign 4,004 2,879 433 Total current tax expense 719,133 468,635 220,449 Deferred: Federal (119,849 ) (62,932 ) 53,504 State (3,768 ) 18,891 8,700 Foreign (6,475 ) (1,485 ) (9 ) Total deferred tax (benefit) expense (130,092 ) (45,526 ) 62,195 $ 589,041 $ 423,109 $ 282,644 In 2015, 2014, and 2013, the Company utilized $405.3 million , $439.3 million , and $211.9 million of excess tax benefits in connection with stock option exercises, which were credited to additional paid-in capital as realized. The Company also recorded an income tax provision in its Statement of Comprehensive Income of $24.9 million and $27.1 million during the years ended December 31, 2015 and 2014, respectively, in connection with unrealized gains (losses) on "available-for-sale" marketable securities. For the year ended December 31, 2013, no such income tax provision or benefit was recognized. A reconciliation of the U.S. statutory income tax rate to the Company's effective income tax rate is as follows: Year Ended December 31, 2015 2014 2013 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % State and local income taxes 1.0 2.4 3.4 Change in state effective rate (0.1 ) 2.9 — Foreign income tax rate differential 12.2 15.8 4.9 Income tax credits (1.6 ) (5.1 ) (4.9 ) Non-deductible Branded Prescription Drug Fee 2.0 2.8 1.1 Domestic production activities deduction (3.2 ) — — Other permanent differences 2.8 1.8 1.1 Effective income tax rate 48.1 % 55.6 % 40.6 % In 2015, the difference between the U.S. federal statutory rate of 35% and the Company's effective tax rate of 48.1% is primarily attributable to losses incurred in foreign jurisdictions with rates lower than the U.S. federal statutory rate, partly offset by the positive impact of the domestic manufacturing deduction. In 2014, the difference between the U.S. federal statutory rate of 35% and the Company's effective tax rate of 55.6% was primarily attributable to losses incurred in foreign jurisdictions with rates lower than the U.S. federal statutory rate and the non-deductible Branded Prescription Drug Fee, partly offset by the positive impact of the federal tax credit for increased research activities and state income tax credits. In 2013, the difference between the U.S. federal statutory rate of 35% and the Company's effective tax rate of 40.6% was primarily attributable to increases related to losses incurred in foreign jurisdictions with rates lower than the U.S. federal statutory rate and state and local taxes. These negative impacts were partially offset by federal and state income tax credits. In January, 2013, The American Taxpayer Relief Act was enacted, which included a provision to extend the income tax credit for increased research activities retroactively to the tax year ended December 31, 2012, as well as for 2013. As a result of the extension, during 2013, the Company recognized the benefit of both the 2012 and 2013 federal research tax credit, which totaled $34.0 million . Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets and liabilities are as follows: As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforward $ 140 $ 150 Fixed assets — 8,078 Deferred revenue 51,766 60,223 Deferred compensation 349,508 216,640 Income tax credit carryforwards — 8,539 Capitalized research and development costs 7,725 12,908 Accrued expenses 47,520 19,331 Other 26,580 21,922 483,239 347,791 Valuation allowance — (359 ) Total deferred tax assets 483,239 347,432 Deferred tax liabilities: Unrealized gains/losses on marketable securities (3,280 ) (28,186 ) Fixed assets (5,559 ) — Convertible senior notes — (252 ) Other (12,455 ) (3,578 ) Total deferred tax liabilities (21,294 ) (32,016 ) Net deferred tax assets $ 461,945 $ 315,416 The Company has state net operating loss carryforwards and state tax credits which will expire in various years from 2024 to 2034. The Internal Revenue Code and various state tax laws contain certain provisions that can limit a taxpayer's ability to utilize net operating losses and tax credit carryforwards in any given year resulting from cumulative changes in ownership interests in excess of 50% over a three-year period. The Company does not believe, however, that any such limitation would have a significant impact on the Company's ability to utilize its net operating losses or income tax credit carryforwards prior to expiration. The Company's 2012 through 2014 federal income tax returns remain open to examination by the IRS. The Company's 2012 federal income tax return is currently under audit by the IRS. The Company's state income tax returns from 2012 to 2014 remain open to examination. New York State Department of Taxation and Finance is currently auditing the Company's 2012 through 2014 tax returns, and the Department of Revenue of the Commonwealth of Pennsylvania is currently auditing the Company's 2013 and 2014 tax returns . The United States and many states generally have statutes of limitation ranging from 3 to 5 years; however, those statutes could be extended due to the Company's net operating loss and tax credit carryforward positions in a number of the Company's tax jurisdictions. In general, tax authorities have the ability to review income tax returns for loss periods in which the statute of limitation has previously expired to adjust the net operating loss carryforward or tax credits generated in those years. The following table summarizes the gross amounts of unrecognized tax benefits. The amount of unrecognized tax benefits that, if settled, would impact the effective tax rate is $102.1 million , $51.2 million , and $23.5 million as of December 31, 2015, 2014, and 2013, respectively. 2015 2014 2013 Balance as of January 1 $ 57,615 $ 26,627 $ 11,274 Gross increases related to current year tax positions 59,909 27,538 7,620 Gross (decreases) increases related to prior year tax positions (952 ) 6,464 8,305 Gross decrease due to settlements, recapture, filed returns, and lapse of statutes of limitation — (3,014 ) (572 ) Balance as of December 31 $ 116,572 $ 57,615 $ 26,627 In 2014 and 2015, the increases in unrecognized tax benefits related primarily to the Company's calculation of certain tax credits and other items related to the Company's international operations. In 2014, the decreases in unrecognized tax benefits resulted from the settlement of the IRS audit of the 2011 tax year and the New York State audit of the 2009 to 2011 tax years, as well as the reduction in the New York state income tax rate. In 2013, the increase in unrecognized tax benefits related primarily to the Company's calculation of certain tax credits. In 2015, the Company accrued interest of $1.2 million related to its unrecognized tax benefits. In 2014, accrued interest related to unrecognized tax benefits recorded by the Company was not material, and no interest was accrued in 2013. The Company believes that it is reasonably possible that its unrecognized tax benefits at December 31, 2015 may increase within the next twelve months relating to operations during that period, in excess of potential decreases due to the resolution of the federal audit.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Legal Matters	Legal Matters From time to time, the Company is a party to legal proceedings in the course of the Company's business. Costs associated with the Company's involvement in legal proceedings are expensed as incurred. Proceedings Relating to ' 287 Patent, ' 018 Patent, and '163 Patent The Company is a party to patent infringement litigation initiated by the Company involving its European Patent No. 1,360,287 (the "'287 Patent), its European Patent No. 2,264,163 (the "'163 Patent), and its U.S. Patent No. 8,502,018 (the "'018 Patent"). Each of these patents concerns genetically altered mice capable of producing chimeric antibodies that are part human and part mouse. Chimeric antibody sequences can be used to produce high-affinity fully human monoclonal antibodies. In these proceedings, the Company claims infringement of several claims of the '287 Patent, the '163 Patent, and the '018 Patent (as applicable), and seeks, among other types of relief, an injunction and an account of profits in connection with the defendants' infringing acts, which may include, among other things, the making, use, keeping, sale, or offer for sale of genetically engineered mice (or certain cells from which they are derived) that infringe one or more claims of the '287 Patent, the '163 Patent, and the '018 Patent (as applicable). At this time, the Company is not able to predict the outcome of, or an estimate of gain or a range of possible loss, if any, related to, these proceedings. Proceedings Relating to Praluent (alirocumab) Injection On October 17, 2014 and October 28, 2014, Amgen Inc. filed complaints against Regeneron, Sanofi, Aventisub LLC (subsequently removed and replaced with Sanofi-Aventis U.S. LLC), and Aventis Pharmaceuticals, Inc. in the United States District Court for the District of Delaware seeking an injunction to prohibit Regeneron and the other defendants from manufacturing, using, offering to sell, or selling within the United States (as well as importing into the United States) Praluent, which Regeneron is jointly developing with Sanofi. On November 11, 2014 and November 17, 2014 Amgen filed complaints against Regeneron, Sanofi, Sanofi-Aventis U.S. LLC, and Aventis Pharmaceuticals, Inc. in the same court seeking the same relief. Amgen asserts U.S. Patent Nos. 8,563,698, 8,829,165 (the "'165 Patent"), and 8,859,741 (the "'741 Patent") in the first complaint, U.S. Patent Nos. 8,871,913 and 8,871,914 (the "'914 Patent") in the second complaint, U.S. Patent No. 8,883,983 in the third complaint, and U.S. Patent No. 8,889,834 in the fourth complaint. Amgen also seeks a judgment of patent infringement of the asserted patents, monetary damages (together with interest), costs and expenses of the lawsuits, and attorneys' fees. On December 15, 2014, all of the four proceedings were consolidated into a single case. On September 15, 2015, Amgen filed a motion for leave to file a supplemental and second amended complaint, which was granted on January 29, 2016. As amended, the complaint alleges, among other things, willful infringement of the asserted patents, which would allow the court to increase damages up to three times the amount assessed if the court finds willful infringement. On October 20, 2015, the District Court issued its claim construction order, in which it defined the meaning of certain disputed claim terms; none of the court's rulings were dispositive of the issues in the case. On November 3, 2015, pursuant to court order, the patents asserted by Amgen were narrowed to the '165, '741, and '914 Patents. The trial is currently set to begin on March 7, 2016, and a permanent injunction hearing (which would be held if the court finds infringement of a valid patent claim by the Company and Sanofi) is currently scheduled to begin on March 23, 2016. At this time, the Company is not able to estimate a range of possible loss, if any, related to these proceedings. Proceedings Relating to Patents Owned by Genentech and City of Hope On July 27, 2015, the Company and Sanofi-Aventis U.S. LLC filed a complaint in the United States District Court for the Central District of California (Western Division) seeking a declaratory judgment of invalidity, as well as non-infringement by the manufacture, use, sale, offer of sale, or importation of Praluent (alirocumab), of U.S. Patent No. 7,923,221 (the "'221 Patent") jointly owned by Genentech, Inc. ("Genentech") and City of Hope relating to the production of recombinant antibodies by host cells. On the same day, the Company and Sanofi-Aventis U.S. LLC initiated an inter partes review in the United States Patent and Trademark Office ("USPTO") seeking a declaration of invalidity of certain claims of U.S. Patent No. 6,331,415 jointly owned by Genentech and City of Hope relating to the production of recombinant antibodies by host cells. On February 5, 2016, the USPTO instituted an inter partes review of the validity of most of the patent claims for which review had been requested. On September 17, 2015, Genentech and City of Hope answered the complaint previously filed by the Company and Sanofi in the District Court and counterclaimed, alleging that the Company and Sanofi infringe the '221 Patent and seeking, among other types of relief, damages and a permanent injunction. On November 2, 2015, the court set a tentative trial date beginning on September 27, 2016. At this time, the Company is not able to predict the outcome of, or an estimate of gain or range of possible loss, if any, related to these proceedings. Proceedings Relating to Shareholder Derivative Claims On December 30, 2015, an alleged shareholder filed a shareholder derivative complaint in the New York Supreme Court, naming the current and certain former non-employee members of the Company's board of directors, the Chairman of the board of directors, the Company's Chief Executive Officer, and the Company's Chief Scientific Officer as defendants and Regeneron as a nominal defendant. The complaint asserts that the individual defendants breached their fiduciary duties and were unjustly enriched when they approved and/or received allegedly excessive compensation in 2013 and 2014. The complaint seeks damages in favor of the Company for the alleged breaches of fiduciary duties and unjust enrichment; changes to Regeneron's corporate governance and internal procedures; invalidation of the 2014 Incentive Plan with respect to the individual defendants' compensation and a shareholder vote regarding the individual defendants' equity compensation; equitable relief, including an equitable accounting with disgorgement; and award of the costs of the action, including attorneys' fees. The Company intends to move to dismiss the shareholder derivative complaint. On or about December 15, 2015, the Company received a shareholder litigation demand upon the Company's board of directors made by a purported Regeneron shareholder. The demand asserts that the current and certain former non-employee members of the board of directors and the Chairman of the board of directors excessively compensated themselves in 2013 and 2014. The demand requests that the board of directors investigate and bring legal action against these directors for breach of fiduciary duty, unjust enrichment, and corporate waste, and implement internal controls and systems designed to prohibit and prevent similar actions in the future. The Company's board of directors, working with outside counsel, investigated the allegations in the demand and the shareholder derivative complaint, and has determined to defer its decision on the demand until the court rules on the forthcoming motion to dismiss the shareholder derivative complaint, as discussed above. At this time, the Company is not able to estimate a range of possible loss, if any, relating to these matters.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	Net Income Per Share The Company's basic net income per share amounts have been computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Diluted net income per share includes the potential dilutive effect of other securities as if such securities were converted or exercised during the period, when the effect is dilutive. The calculations of basic and diluted net income per share are as follows: Year Ended December 31, 2015 2014 2013 Net income - basic and diluted $ 636,056 $ 338,126 $ 413,738 (Shares in thousands) Weighted average shares - basic 103,061 100,612 97,917 Effect of dilutive securities: Stock options 9,446 9,440 10,233 Restricted stock 477 425 433 Warrants 2,246 2,936 2,707 Dilutive potential shares 12,169 12,801 13,373 Weighted average shares - diluted 115,230 113,413 111,290 Net income per share - basic $ 6.17 $ 3.36 $ 4.23 Net income per share - diluted $ 5.52 $ 2.98 $ 3.72 Shares which have been excluded from diluted per share amounts because their effect would have been antidilutive, include the following: Year Ended December 31, (Shares in thousands) 2015 2014 2013 Stock options 1,343 1,470 304 Convertible senior notes 994 4,247 4,761

Statement of Cash Flows

Statement of Cash Flows	12 Months Ended
	Dec. 31, 2015
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Statement of Cash Flows	Statement of Cash Flows Supplemental disclosure of non-cash investing and financing activities: Included in accounts payable and accrued expenses as of December 31, 2015, 2014, and 2013 were $50.7 million , $56.2 million , and $16.1 million , respectively, of accrued capital expenditures. Included in accounts payable and accrued expenses as of December 31, 2015 and 2014 was $1.6 million and $7.5 million , respectively, for the Company's conversion settlement obligation related to the Company's Notes which were surrendered for conversion but not settled as of the end of the respective period. No such amounts were payable as of December 31, 2013. Included in accounts payable and accrued expenses as of December 31, 2014 was $59.8 million related to the Company's payment obligation for a reduction in the number of warrants based on a warrant holder closing out a portion of its hedge position (see Note 11). Additionally, included within other current liabilities as of December 31, 2014 was $87.5 million in connection with the estimated fair value of the remaining warrant liability (see Note 11). There were no such liabilities recorded in connection with warrants as of December 31, 2015 and 2013. The Company recognized a facility lease obligation of $26.0 million , $127.8 million and $25.0 million during 2015, 2014 and 2013, respectively, in connection with capitalizing, on the Company's books, the landlord's costs of constructing new facilities that the Company has leased (see Note 12a).

Unaudited Quarterly Results

Unaudited Quarterly Results	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Results	Unaudited Quarterly Results Summarized quarterly financial data for the years ended December 31, 2015 and 2014 are set forth in the following tables. First Quarter Ended March 31, 2015 Second Quarter Ended June 30, 2015 Third Quarter Ended September 30, 2015 Fourth Quarter Ended December 31, 2015 (Unaudited) Revenues $ 869,612 $ 998,617 $ 1,137,422 $ 1,098,077 Net income $ 76,021 $ 194,643 $ 210,398 $ 154,994 Net income per share - basic $ 0.74 $ 1.89 $ 2.04 $ 1.49 Net income per share - diluted $ 0.66 $ 1.69 $ 1.82 $ 1.34 First Quarter Ended March 31, 2014 * Second Quarter Ended June 30, 2014 * Third Quarter Ended September 30, 2014 * Fourth Quarter Ended December 31, 2014 * (Unaudited) Revenues $ 625,740 $ 665,700 $ 725,788 $ 802,329 Net income (1) $ 68,305 $ 96,351 $ 83,375 $ 90,095 Net income per share - basic $ 0.69 $ 0.96 $ 0.83 $ 0.89 Net income per share - diluted $ 0.61 $ 0.85 $ 0.73 $ 0.78 * Certain revisions have been made to the amounts originally reported for quarterly periods ended March 31, June 30, September 30, and December 31, 2014. See Note 14. (1) Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.

Business Overview and Summary27

Business Overview and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Consolidation	Basis of Presentation The consolidated financial statements include the accounts of Regeneron and its wholly-owned subsidiaries. Intercompany balances and transactions are eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Estimates which could have a significant impact on the Company's financial statements include provisions related to product sales, such as rebates, chargebacks, and distribution-related fees; periods over which payments, including non-refundable up-front, license, and milestone payments, are recognized as revenue in connection with collaboration and other agreements; periods over which certain clinical trial costs are recognized; fair value of stock options; inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value; capitalization of inventory costs associated with the Company's products prior to regulatory approval; deferred tax asset valuation allowances; and the assessment of uncertain tax positions. With respect to the Company's collaborations with Sanofi and Bayer HealthCare: • Included in Sanofi collaboration revenue is the Company's share of profits or losses from commercialization of antibodies, which is provided by Sanofi, and include an estimate of the Company's share of profits or losses for the most recent fiscal quarter. • Included in Bayer HealthCare collaboration revenue is the Company's share of profits or losses from commercialization of EYLEA outside the United States, which is provided by Bayer HealthCare, and includes an estimate of the Company's share of profits or losses for the most recent fiscal quarter. • Included in research and development expenses is the Company's share of development expenses incurred by Bayer HealthCare and Sanofi, including the Company's share of Bayer HealthCare and Sanofi estimated development expenses for the most recent fiscal quarter. These estimates for the most recent period are adjusted, if necessary, in the subsequent period to reflect actual amounts.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid debt instruments with a maturity of three months or less when purchased to be cash equivalents. The carrying amount reported in the Balance Sheet for cash and cash equivalents approximates its fair value.
Marketable Securities	Marketable Securities The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. The Company invests its excess cash primarily in marketable securities issued by investment grade institutions. The Company considers its marketable securities to be "available-for-sale," as defined by authoritative guidance issued by the Financial Accounting Standards Board ("FASB"). These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). If a decline in the value of a marketable security in the Company's investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary.
Accounts Receivable - Trade	Accounts Receivable - Trade The Company's trade accounts receivable arise from product sales and represent amounts due from its distributors and specialty pharmacies (collectively, the Company's "customers"), which are all located in the United States. The Company monitors the financial performance and credit worthiness of its large customers so that it can properly assess and respond to changes in their credit profile. The Company provides reserves against trade receivables for estimated losses, if any, that may result from a customer's inability to pay. Amounts determined to be uncollectible are written-off against the reserve.
Inventories	Inventories Inventories are stated at the lower of cost or estimated realizable value. The Company determines the cost of inventory using the first-in, first-out, or FIFO, method. The Company capitalizes inventory costs associated with the Company's products prior to regulatory approval when, based on management's judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed as research and development. The determination to capitalize inventory costs is based on various factors, including status and expectations of the regulatory approval process, any known safety or efficacy concerns, potential labeling restrictions, and any other impediments to obtaining regulatory approval. The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes-down such inventories as appropriate. In addition, the Company's products are subject to strict quality control and monitoring which the Company performs throughout the manufacturing process. If certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, the Company records a charge to cost of goods sold to write down such unmarketable inventory to its estimated realizable value.
Property, Plant and Equipment	Property, Plant, and Equipment Property, plant, and equipment are stated at cost, net of accumulated depreciation. Depreciation is provided on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the lease term. Costs of construction of certain long-lived assets include capitalized interest, which is amortized over the estimated useful life of the related asset. Expenditures for maintenance and repairs which do not materially extend the useful lives of the assets are charged to expense as incurred. The cost and accumulated depreciation or amortization of assets retired or sold are removed from the respective accounts, and any gain or loss is recognized in operations. The estimated useful lives of property, plant, and equipment are as follows: Building and improvements 10-30 years Laboratory and other equipment 3-10 years Furniture and fixtures 5 years The Company periodically assesses the recoverability of long-lived assets, such as property, plant, and equipment, and evaluates such assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.
Revenue Recognition - Product Revenue	Product Revenue Product sales consist of U.S. sales of EYLEA and ARCALYST. Revenue from product sales is recognized when persuasive evidence of an arrangement exists, title to product and associated risk of loss have passed to the customer, the price is fixed or determinable, collection from the customer is reasonably assured, the Company has no further performance obligations, and returns can be reasonably estimated. The Company's written contracts with its customers stipulate product is shipped freight on board destination (FOB destination). The Company records revenue from product sales upon delivery to its customers. The Company sells EYLEA in the United States to several distributors and specialty pharmacies. The Company sells ARCALYST in the United States to two specialty pharmacies. Under these distribution models, the distributors and specialty pharmacies generally take physical delivery of product. For EYLEA, the distributors and specialty pharmacies generally sell the product directly to healthcare providers, whereas for ARCALYST, the specialty pharmacies sell the product directly to patients. Revenue from product sales is recorded net of applicable provisions for rebates and chargebacks under governmental programs, distribution-related fees, and other sales-related deductions. Calculating these provisions involves estimates and judgments. The Company reviews its estimates of rebates, chargebacks, and other applicable provisions each period and records any necessary adjustments in the current period's net product sales. Government Rebates and Chargebacks: The Company estimates reductions to product sales for Medicaid and Veterans' Administration ("VA") programs, and for certain other qualifying federal and state government programs. Based upon the Company's contracts with government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, and estimated payer mix, the Company estimates and records an allowance for rebates and chargebacks. The Company's liability for Medicaid rebates consists of estimates for claims that a state will make for a current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, and invoices received for claims from prior quarters that have not been paid. The Company's reserves related to discounted pricing to VA, Public Health Services ("PHS"), and other institutions (collectively "qualified healthcare providers") represent the Company's estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices the Company charges to its customers (i.e., distributors and specialty pharmacies). The Company's customers charge the Company for the difference between what they pay for the products and the ultimate selling price to the qualified healthcare providers. The Company's reserve for this discounted pricing is based on expected sales to qualified healthcare providers and the chargebacks that customers have already claimed. Distribution-Related Fees: The Company has written contracts with its customers that include terms for distribution-related fees. The Company estimates and records distribution and related fees due to its customers based on gross sales. Prompt Pay Discounts: No prompt pay discounts are currently offered to the Company's customers on sales of EYLEA. In connection with sales of ARCALYST, the Company offers discounts to its customers for prompt payments. The Company estimates these discounts based on customer terms and historical experience, and expects that its customers will always take advantage of this discount. Therefore, the Company accrues 100% of the prompt pay discount that is based on the gross amount of each ARCALYST invoice, at the time of sale. Product Returns: Consistent with industry practice, the Company offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product's expiration date. The Company will accept returns for three months prior to and up to six months after the product expiration date. Product returned is generally not resalable given the nature of the Company's products and method of administration. The Company develops estimates for product returns based upon historical experience, inventory levels in the distribution channel, shelf life of the product, and other relevant factors. The Company monitors product supply levels in the distribution channel, as well as sales by its customers of EYLEA to healthcare providers and ARCALYST to patients using product-specific data provided by its customers. If necessary, the Company's estimates of product returns may be adjusted in the future based on actual returns experience, known or expected changes in the marketplace, or other factors.
Revenue Recognition - Collaboration Revenue	Collaboration Revenue The Company earns collaboration revenue in connection with collaboration agreements to develop and commercialize product candidates and utilize the Company's technology platforms. These arrangements may require the Company to deliver various rights, services, and/or goods across the entire life cycle of a product or product candidate. The terms of these agreements typically include that consideration be provided to the Company in the form of non-refundable up-front payments, milestone payments, payments for development and commercialization activities, and sharing of profits or losses arising from the commercialization of products. In connection with non-refundable up-front payments, the Company's performance period estimates are principally based on projections of the scope, progress, and results of its research and development activities. Due to the variability in the scope of activities and length of time necessary to develop a drug product, changes to development plans as programs progress, and uncertainty in the ultimate requirements to obtain regulatory approval for commercialization, revisions to performance period estimates are likely to occur periodically, and could result in material changes to the amount of revenue recognized each year in the future. In addition, estimated performance periods may change if development programs encounter delays, or the Company and its collaborators decide to expand or contract the clinical plans for a drug candidate in various disease indications. In arrangements involving multiple deliverables, each required deliverable is evaluated to determine whether it qualifies as a separate unit of accounting. This determination is generally based on whether the deliverables in the arrangement meet certain criteria, including whether the delivered item or items has value to the collaborator on a standalone basis. The arrangement's consideration that is fixed and determinable is allocated to each separate unit of accounting based on the relative selling price of each deliverable. If multiple collaboration activities or rights do not require separation, they are combined into a single unit of accounting and recognized over the performance period, which is the period over which the Company is obligated to deliver goods or services. The Company estimates its performance period based on the specific terms of each agreement, and adjusts the performance periods, if appropriate, based on the applicable facts and circumstances. Payments which are based on achieving a specific substantive performance milestone, involving a degree of risk, are recognized as revenue when the milestone is achieved and the related payment is due and non-refundable, provided there is no future service obligation associated with that milestone. Substantive performance milestones typically consist of significant achievements in the development life-cycle of the related product candidate, such as completion of clinical trials, filing for approval with regulatory agencies, and receipt of approvals by regulatory agencies. In determining whether a payment is deemed to be a substantive performance milestone, the Company takes into consideration (i) the enhancement in value to the related development product candidate, (ii) the Company's performance and the relative level of effort required to achieve the milestone, (iii) whether the milestone relates solely to past performance, and (iv) whether the milestone payment is considered reasonable relative to all of the deliverables and payment terms. Payments for achieving milestones which are not considered substantive are deferred and recognized over the related performance period. The Company enters into collaboration agreements that include varying arrangements regarding which parties perform and bear the costs of research and development activities. The Company may share the costs of research and development activities with a collaborator, or the Company may be reimbursed for all or a significant portion of the costs of the Company's research and development activities. The Company records its internal and third-party development costs associated with these collaborations as research and development expenses. When the Company is entitled to reimbursement of all or a portion of the research and development expenses that it incurs under a collaboration, the Company records those reimbursable amounts as collaboration revenue proportionately as the Company recognizes its expenses. If the collaboration is a cost-sharing arrangement in which both the Company and its collaborator perform development work and share costs, the Company also recognizes, as additional research and development expense in the period when its collaborator incurs development expenses, the portion of the collaborator's development expenses that the Company is obligated to reimburse. The Company may also be obligated to use commercially reasonable efforts to supply commercial bulk product to its collaborators. In such cases, the Company is reimbursed for its manufacturing costs as commercial product is shipped to its collaborators; however, recognition of such cost reimbursements as collaboration revenue is deferred until the product is sold by the Company's collaborators to third-party customers, at which time the Company's risk of inventory loss no longer exists. In addition, at that time, the related manufacturing costs for the sold product, which had been capitalized into inventory, are recognized by the Company. Under the Company's collaboration agreements, product sales and cost of sales for products which are currently approved are recorded by the Company's collaborators. The Company shares in any profits or losses arising from the commercialization of such products. The Company records its share of the profits or losses from commercialization of such products, representing net product sales less cost of goods sold and shared commercialization and other expenses, as collaboration revenue.
Research and Development Expenses	Research and Development Expenses Research and development expenses include costs directly attributable to the conduct of research and development programs, including the cost of salaries, payroll taxes, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, costs related to research collaboration and licensing agreements, the cost of services provided by outside contractors, including services related to the Company's clinical trials, clinical trial expenses, the full cost of manufacturing drug for use in research, preclinical development, and clinical trials, amounts that the Company is obligated to reimburse to collaborators for research and development expenses that they incur, and the allocable portions of facility costs, such as rent, utilities, insurance, repairs and maintenance, depreciation, and general support services. Costs associated with research and development are expensed. Clinical trial costs are a significant component of research and development expenses and include costs associated with third-party contractors. The Company outsources a substantial portion of its clinical trial activities, utilizing external entities such as contract research organizations ("CROs"), independent clinical investigators, and other third-party service providers to assist the Company with the execution of its clinical studies. For each clinical trial that the Company conducts, certain clinical trial costs are expensed immediately, while others are expensed over time based on the expected total number of patients in the trial, the rate at which patients enter the trial, and/or the period over which clinical investigators or CROs are expected to provide services. Clinical activities which relate principally to clinical sites and other administrative functions to manage the Company's clinical trials are performed primarily by CROs. CROs typically perform most of the start-up activities for the Company's trials, including document preparation, site identification, screening and preparation, pre-study visits, training, and program management. These start-up costs usually occur within a few months after the contract has been executed and are event driven in nature. The remaining activities and related costs, such as patient monitoring and administration, generally occur ratably throughout the life of the individual contract or study. In the event of early termination of a clinical trial, the Company accrues and recognizes expenses in an amount based on its estimate of the remaining non-cancelable obligations associated with the winding down of the clinical trial and/or penalties. For clinical study sites, where payments are made periodically on a per-patient basis to the institutions performing the clinical study, the Company accrues expenses on an estimated cost-per-patient basis, based on subject enrollment and activity in each quarter. The amount of clinical study expense recognized in a quarter may vary from period to period based on the duration and progress of the study, the activities to be performed by the sites each quarter, the required level of patient enrollment, the rate at which patients actually enroll in and drop-out of the clinical study, and the number of sites involved in the study. Clinical trials that bear the greatest risk of change in estimates are typically those that have a significant number of sites, require a large number of patients, have complex patient screening requirements, and span multiple years. During the course of a trial, the Company adjusts its rate of clinical expense recognition if actual results differ from the Company's estimates. The Company's estimates and assumptions for clinical expense recognition could differ significantly from its actual results, which could cause material increases or decreases in research and development expenses in future periods when the actual results become known.
Stock-based Compensation	Stock-based Compensation The Company recognizes stock-based compensation expense for grants of stock option awards and restricted stock under the Company's Long-Term Incentive Plans to employees and non-employee members of the Company's board of directors based on the grant-date fair value of those awards. The grant-date fair value of an award is generally recognized as compensation expense over the award's requisite service period. The Company uses the Black-Scholes model to compute the estimated fair value of stock option awards. Using this model, fair value is calculated based on assumptions with respect to (i) expected volatility of the Company's Common Stock price, (ii) the periods of time over which employees and members of the board of directors are expected to hold their options prior to exercise (expected lives), (iii) expected dividend yield on the Common Stock, and (iv) risk-free interest rates. Stock-based compensation expense also includes an estimate, which is made at the time of grant, of the number of awards that are expected to be forfeited. This estimate is revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.
Income Taxes	Income Taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax assets and liabilities are determined on the basis of the difference between the tax basis of assets and liabilities and their respective financial reporting amounts ("temporary differences") at enacted tax rates in effect for the years in which the differences are expected to reverse. A valuation allowance is established for deferred tax assets for which it is more likely than not that some portion or all of the deferred tax assets will not be realized. Uncertain tax positions, for which management's assessment is that there is more than a 50% probability of sustaining the position upon challenge by a taxing authority based upon its technical merits, are subjected to certain recognition and measurement criteria. The Company re-evaluates uncertain tax positions and consider various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, and changes in facts or circumstances related to a tax position. The Company adjusts the level of the liability to reflect any subsequent changes in the relevant facts and circumstances surrounding the uncertain positions. The Company recognizes interest and penalties related to income tax matters in income tax expense.
Per Share Data	Per Share Data Basic net income per share is computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Basic net income per share excludes restricted stock awards until vested. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were converted or exercised during the period, when the effect is dilutive. Common stock equivalents include: (i) outstanding stock options and restricted stock awards under the Company's Long-Term Incentive Plans, which are included under the "treasury stock method" when dilutive, (ii) Common Stock to be issued upon the assumed conversion of the Company's convertible senior notes, which are included under the "if-converted method" when dilutive, and (iii) Common Stock to be issued upon the exercise of outstanding warrants, which are included under the "treasury stock method" when dilutive.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments which potentially expose the Company to concentrations of credit risk consist of cash, cash equivalents, certain financial instruments, and accounts receivable. A large portion of the Company's cash is held by a few major financial institutions. In accordance with the Company's policies, the Company mandates asset diversification and monitors exposure with its counterparties. Concentrations of credit risk with respect to accounts receivable are significant. Accounts receivable from product sales of EYLEA and ARCALYST are due from several distributors and specialty pharmacies, who are the Company's customers. As of December 31, 2015 and 2014, one individual customer accounted for 68% and 70% , respectively, of the Company's net trade accounts receivable balances. The Company has contractual payment terms with each of its customers, and the Company monitors its customers' financial performance and credit worthiness so that it can properly assess and respond to any changes in their credit profile. In addition, the Company may insure a portion of its accounts receivables within its overall risk management practices. As of December 31, 2015 and 2014, there were no reserves against trade accounts receivable. In addition, during the years ended December 31, 2015, 2014, and 2013, the Company did no t recognize any charges for write-offs of trade accounts receivable.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In November 2015, the FASB issued Accounting Standards Update 2015-17, Balance Sheet Classification of Deferred Taxes , which is intended to simplify the balance sheet presentation of deferred income taxes. Current accounting principles require an entity to separate deferred income tax liabilities and assets into current and noncurrent amounts in its balance sheet. The amendments require that deferred tax liabilities and assets be classified as noncurrent in its balance sheet. The amendments are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Companies may apply the new provisions either retrospectively or on a prospective basis, and early adoption is permitted. The Company early adopted the amendments effective December 31, 2015 on a retrospective basis. The impact of the adoption of the amendments on the Company's Consolidated Balance Sheet as of December 31, 2014 was a $46.2 million reclassification of current deferred tax assets to noncurrent deferred tax assets. In May 2014, the FASB issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers , which will replace existing revenue recognition guidance. The new standard requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. To achieve that core principle, an entity must identify the contract(s) with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies the performance obligation. In July 2015, the FASB decided to delay the effective date of the new standard by one year; as a result, the new standard will be effective for annual and interim reporting periods beginning after December 15, 2017. Early adoption will be permitted, but no earlier than 2017 for calendar year-end entities. The standard allows for two transition methods - retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial adoption. The Company has not yet determined its method of transition and is evaluating the impact that this guidance will have on the Company's financial statements. In January 2016, the FASB issued Accounting Standards Update 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . The amendments require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income, and separate presentation of financial assets and financial liabilities by measurement category and form of financial asset. Additionally, the amendments eliminate the requirement to disclose the methods and significant assumptions used to estimate the fair value of financial instruments. The amendments are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. Other than an amendment relating to presenting in comprehensive income the portion of the total change in the fair value of a liability resulting from a change in instrument-specific credit risk (if the entity has elected to measure the liability at fair value), early adoption is not permitted. The Company is evaluating the impact that this guidance will have on the Company's financial statements.
Legal Costs	Costs associated with the Company's involvement in legal proceedings are expensed as incurred.
Fair Value Transfer, Policy	The Company's policy for recognition of transfers between levels of the fair value hierarchy is to recognize any transfer at the beginning of the fiscal quarter in which the determination to transfer was made.

Business Overview and Summary28

Business Overview and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Estimated useful lives of property, plant, and equipment [Table Text Block]	The estimated useful lives of property, plant, and equipment are as follows: Building and improvements 10-30 years Laboratory and other equipment 3-10 years Furniture and fixtures 5 years

Net Product Sales (Tables)

Net Product Sales (Tables)	12 Months Ended
	Dec. 31, 2015
Revenues [Abstract]
Sales Related Deductions Activity	The following table summarizes the provisions, and credits/payments, for these sales-related deductions for the years ended December 31, 2015, 2014, and 2013. Rebates & Chargebacks Distribution- Related Fees Other Sales- Related Deductions Total Balance as of December 31, 2012 $ 2,983 $ 15,298 $ 545 $ 18,826 Provision related to current period sales 25,936 62,984 955 89,875 Credits/payments (24,519 ) (58,619 ) (962 ) (84,100 ) Balance as of December 31, 2013 4,400 19,663 538 24,601 Provision related to current period sales 33,117 77,160 1,578 111,855 Credits/payments (34,434 ) (75,657 ) (1,584 ) (111,675 ) Balance as of December 31, 2014 3,083 21,166 532 24,781 Provision related to current period sales 61,124 122,466 9,600 193,190 Credits/payments (57,788 ) (95,319 ) (9,615 ) (162,722 ) Balance as of December 31, 2015 $ 6,419 $ 48,313 $ 517 $ 55,249

Collaboration Agreements (Table

Collaboration Agreements (Tables)	12 Months Ended
	Dec. 31, 2015
Collaboration Agreement [Abstract]
Schedule of Related Party Transactions	The collaboration revenue the Company earned from Sanofi is detailed below: Year Ended December 31, Sanofi Collaboration Revenue 2015 2014 2013 Antibody: Reimbursement of Regeneron research and development expenses $ 735,439 $ 547,761 $ 453,489 Reimbursement of Regeneron commercialization-related expenses 157,350 19,480 1,868 Regeneron's share of losses in connection with commercialization of antibodies (240,042 ) (41,378 ) — Up-front payments to Sanofi for acquisition of rights related to two antibodies — — (20,000 ) Other 10,243 10,243 10,243 Total Antibody 662,990 536,106 445,600 Immuno-oncology: Reimbursement of Regeneron research and development expenses 39,961 — — Other 40,000 — — Total Immuno-oncology 79,961 — — ZALTRAP: Regeneron's share of losses in connection with commercialization of ZALTRAP — (4,715 ) (30,810 ) Reimbursement of Regeneron research and development expenses 686 4,806 5,639 Other 15,236 5,102 9,682 Total ZALTRAP 15,922 5,193 (15,489 ) $ 758,873 $ 541,299 $ 430,111
Collaboration revenue	The collaboration revenue the Company earned from Bayer HealthCare is detailed below: Year Ended December 31, Bayer HealthCare Collaboration Revenue 2015 2014 2013 EYLEA: Regeneron's net profit in connection with commercialization of EYLEA outside the United States $ 466,667 $ 301,302 $ 101,494 Sales and substantive development milestones 15,000 105,000 70,000 Cost-sharing of Regeneron EYLEA development expenses 8,887 23,383 20,905 Other 69,466 52,390 27,890 Total EYLEA 560,020 482,075 220,289 PDGFR-beta antibody: Cost-sharing of REGN2176-3 development expenses 10,075 2,848 — Other 10,393 10,632 — Total PDGFR-beta 20,468 13,480 — $ 580,488 $ 495,555 $ 220,289
Schedule of Selected Financial Information - Sanofi	Other selected financial information in connection with the Company's collaboration agreements with Sanofi is as follows: December 31, 2015 2014 Antibody: Accounts receivable, net $ 126,687 $ 110,559 Deferred revenue 84,237 64,408 Immuno-oncology: Accounts receivable, net $ 21,394 — Deferred revenue 600,000 —
Schedule of Selected Financial Information - Bayer	Other selected financial information in connection with the Company's collaboration agreements with Bayer HealthCare is as follows: December 31, 2015 2014 EYLEA: Accounts receivable, net $ 160,755 $ 124,293 Deferred revenue 46,694 28,752 PDGFR-beta antibody: Accounts receivable, net $ 1,397 $ 1,191 Deferred revenue 9,522 19,909

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	The following tables summarize the Company's investments in marketable securities: Amortized Unrealized Fair As of December 31, 2015 Cost Basis Gains Losses Value Unrestricted Corporate bonds $ 770,092 $ 156 $ (2,565 ) $ 767,683 U.S. government and government agency obligations 51,402 — (193 ) 51,209 Municipal bonds 17,930 5 (11 ) 17,924 Equity securities 17,005 14,461 — 31,466 $ 856,429 $ 14,622 $ (2,769 ) $ 868,282 As of December 31, 2014 Unrestricted Corporate bonds $ 548,832 $ 136 $ (1,462 ) $ 547,506 U.S. government and government agency obligations 28,596 3 (46 ) 28,553 Municipal bonds 37,044 37 (43 ) 37,038 Equity securities 2,005 5,374 — 7,379 616,477 5,550 (1,551 ) 620,476 Restricted Equity securities 15,000 76,439 — 91,439 $ 631,477 $ 81,989 $ (1,551 ) $ 711,915
Marketable Securities, Based on Contractual Maturity Dates	The fair values of debt security investments by contractual maturity consist of the following: As of December 31, 2015 2014 Maturities within one year $ 236,121 $ 251,761 Maturities after one year through five years 600,695 360,208 Maturities after five years through ten years — 1,128 $ 836,816 $ 613,097
Fair Value and Unrealized Losses of Marketable Securities	The following table shows the fair value of the Company's marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position. Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 668,199 $ (2,473 ) $ 23,749 $ (92 ) $ 691,948 $ (2,565 ) U.S. government and government agency obligations 51,215 (193 ) — — 51,215 (193 ) Municipal bonds 11,917 (11 ) — — 11,917 (11 ) $ 731,331 $ (2,677 ) $ 23,749 $ (92 ) $ 755,080 $ (2,769 ) As of December 31, 2014 Corporate bonds $ 390,613 $ (1,462 ) — — $ 390,613 $ (1,462 ) U.S. government and government agency obligations 25,549 (46 ) — — 25,549 (46 ) Municipal bonds 10,779 (43 ) — — 10,779 (43 ) $ 426,941 $ (1,551 ) — — $ 426,941 $ (1,551 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of assets measured at fair value on a recurring basis	The Company's assets that are measured at fair value on a recurring basis consist of the following: Fair Value Measurements at Reporting Date Using As of December 31, 2015 Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Available-for-sale marketable securities: Unrestricted Corporate bonds $ 767,683 — $ 767,683 U.S. government and government agency obligations 51,209 — 51,209 Municipal bonds 17,924 — 17,924 Equity securities 31,466 $ 31,466 — $ 868,282 $ 31,466 $ 836,816 As of December 31, 2014 Available-for-sale marketable securities: Unrestricted Corporate bonds $ 547,506 — $ 547,506 U.S. government and government agency obligations 28,553 — 28,553 Municipal bonds 37,038 — 37,038 Equity securities 7,379 $ 7,379 — 620,476 7,379 613,097 Restricted Equity securities 91,439 — 91,439 $ 711,915 $ 7,379 $ 704,536

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2015
Inventory Disclosure [Abstract]
Schedule of Inventory, Current	Inventories consist of the following: As of December 31, 2015 2014 Raw materials $ 59,151 $ 10,923 Work-in-process 132,068 73,519 Finished goods 11,197 10,768 Deferred costs 36,162 33,651 $ 238,578 $ 128,861

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant, and equipment consist of the following: As of December 31, 2015 2014 Land $ 77,826 $ 2,768 Building and improvements 760,517 398,981 Leasehold improvements 95,226 42,600 Construction-in-progress 579,834 472,231 Laboratory and other equipment 330,432 253,058 Furniture, computer and office equipment, and other 81,381 58,655 1,925,216 1,228,293 Less, accumulated depreciation and amortization (331,096 ) (253,984 ) $ 1,594,120 $ 974,309

Accounts Payable and Accrued 35

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	Accounts payable and accrued expenses consist of the following: As of December 31, 2015 2014 Accounts payable $ 140,962 $ 99,508 Accrued payroll and related costs 133,223 92,778 Accrued clinical trial expense 88,297 41,555 Accrued sales-related charges, deductions, and royalties 195,986 133,085 Other accrued expenses and liabilities 85,644 116,563 $ 644,112 $ 483,489

Deferred Revenue (Tables)

Deferred Revenue (Tables)	12 Months Ended
	Dec. 31, 2015
Deferred Revenue Disclosure [Abstract]
Deferred Revenue, by Arrangement, Disclosure	Deferred revenue consists of the following: As of December 31, 2015 2014 Current portion: Received or receivable from Sanofi (see Note 3a) $ 101,573 $ 15,927 Received or receivable from Bayer HealthCare (see Note 3b) 24,290 33,652 Received for technology license agreement (see Note 4) 23,572 23,572 Other 4,052 874 $ 153,487 $ 74,025 Long-term portion: Received or receivable from Sanofi (see Note 3a) $ 582,664 $ 62,819 Received or receivable from Bayer HealthCare (see Note 3b) 31,926 15,007 Received for technology license agreement (see Note 4) 33,851 57,423 Other 16,238 — $ 664,679 $ 135,249

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Instrument [Line Items]
Schedule of Long-term Debt Instruments	The net carrying amount of the liability component of the Notes consists of the following: As of December 31, 2015 2014 Total convertible senior notes - par $ 11,154 $ 169,400 Unamortized discount (352 ) (22,627 ) $ 10,802 $ 146,773
Interest Expense Associated with Convertible Notes	Year Ended December 31, 2015 2014 2013 Contractual coupon interest rate $ 544 $ 5,036 $ 7,230 Amortization of discount and note issuance costs 2,818 17,821 22,980 $ 3,362 $ 22,857 $ 30,210

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Facility lease obligation [Table Text Block]	Facility lease obligations consist of the following: As of December 31, 2015 2014 Buildings A and B $ 108,857 $ 110,210 Building C 49,475 49,312 Buildings D and E 206,376 152,770 $ 364,708 $ 312,292
Commitments Under Operating Leases	The estimated future minimum noncancelable lease commitments under operating leases, as of December 31, 2015, are as follows: Facilities Equipment Total 2016 $ 10,894 $ 4,594 $ 15,488 2017 11,332 425 11,757 2018 11,607 140 11,747 2019 11,740 — 11,740 2020 11,375 — 11,375 Thereafter 50,746 — 50,746 $ 107,694 $ 5,159 $ 112,853
Rent Expense Under Operating Leases	Rent expense under operating leases was: Year Ended December 31, Facilities Equipment Total 2015 $ 14,659 $ 543 $ 15,202 2014 13,360 952 14,312 2013 9,404 471 9,875
Commitments Under Facility Lease Obligations	The estimated future minimum noncancelable commitments under these facility lease obligations, as of December 31, 2015, are as follows: Buildings A and B Building C Buildings D and E Total 2016 $ 13,809 $ 4,688 $ 12,679 $ 31,176 2017 14,079 4,818 13,016 31,913 2018 14,356 4,951 13,360 32,667 2019 14,640 5,088 13,714 33,442 2020 14,931 5,227 14,076 34,234 Thereafter 117,096 54,760 137,079 308,935 $ 188,911 $ 79,532 $ 203,924 $ 472,367

Long-Term Incentive Plans (Tabl

Long-Term Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Transactions Involving Stock Option Awards	Transactions involving stock option awards during 2015 under the Company's Incentive Plans are summarized in the table below. Stock Options: Number of Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Intrinsic Value (in thousands) Outstanding as of December 31, 2014 21,506,260 $ 158.54 2015: Granted 4,495,487 $ 537.29 Forfeited (318,952 ) $ 292.14 Expired (363 ) $ 92.20 Exercised (2,516,663 ) $ 98.26 Outstanding as of December 31, 2015 23,165,769 $ 236.75 6.82 $ 7,209,994,851 Vested and expected to vest as of December 31, 2015 22,635,728 $ 231.75 6.76 $ 7,156,754,651 Exercisable as of December 31, 2015 13,212,236 $ 103.67 5.23 $ 5,852,659,560
Weighted-Average Exercise Prices and Weighted-Average Grant-Date Fair Values of Options Issued	The fair value of each option granted under the Company's Incentive Plans during these periods was estimated on the date of grant using the Black-Scholes option-pricing model. Number of Options Granted Weighted-Average Exercise Price Weighted-Average Fair Value 2015: Exercise price equal to Market Price 4,495,487 $ 537.29 $ 181.65 2014: Exercise price equal to Market Price 3,913,368 $ 385.33 $ 140.38 2013: Exercise price equal to Market Price 3,937,989 $ 263.77 $ 104.90
Weighted-Average Values of Assumptions Used in Computing Fair Value of Option Grants	The following table summarizes the weighted average values of the assumptions used in computing the fair value of option grants during 2015, 2014 and 2013. 2015 2014 2013 Expected volatility 35 % 39 % 42 % Expected lives from grant date 5.1 years 5.2 years 5.3 years Expected dividend yield 0 % 0 % 0 % Risk-free interest rate 1.68 % 1.62 % 1.73 %
Activity Related to Restricted Stock Awards	A summary of the Company's activity related to Restricted Stock awards for the year ended December 31, 2015 is summarized below: Restricted Stock: Number of Shares Weighted-Average Grant Date Fair Value Outstanding as of December 31, 2014 546,060 $ 115.26 2015: Granted 27,520 $ 540.40 Vested (31,880 ) $ 164.65 Outstanding as of December 31, 2015 541,700 $ 133.96

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	Components of income before income taxes consist of the following: Year Ended December 31, 2015 2014 2013 United States $ 1,665,087 $ 1,101,446 $ 795,300 Foreign (439,990 ) (340,211 ) (98,918 ) $ 1,225,097 $ 761,235 $ 696,382
Schedule of Components of Income Tax Expense (Benefit)	Components of income tax expense consist of the following: Year Ended December 31, 2015 2014 2013 Current: Federal $ 686,561 $ 437,038 $ 196,527 State 28,568 28,718 23,489 Foreign 4,004 2,879 433 Total current tax expense 719,133 468,635 220,449 Deferred: Federal (119,849 ) (62,932 ) 53,504 State (3,768 ) 18,891 8,700 Foreign (6,475 ) (1,485 ) (9 ) Total deferred tax (benefit) expense (130,092 ) (45,526 ) 62,195 $ 589,041 $ 423,109 $ 282,644
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the U.S. statutory income tax rate to the Company's effective income tax rate is as follows: Year Ended December 31, 2015 2014 2013 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % State and local income taxes 1.0 2.4 3.4 Change in state effective rate (0.1 ) 2.9 — Foreign income tax rate differential 12.2 15.8 4.9 Income tax credits (1.6 ) (5.1 ) (4.9 ) Non-deductible Branded Prescription Drug Fee 2.0 2.8 1.1 Domestic production activities deduction (3.2 ) — — Other permanent differences 2.8 1.8 1.1 Effective income tax rate 48.1 % 55.6 % 40.6 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company's deferred tax assets and liabilities are as follows: As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforward $ 140 $ 150 Fixed assets — 8,078 Deferred revenue 51,766 60,223 Deferred compensation 349,508 216,640 Income tax credit carryforwards — 8,539 Capitalized research and development costs 7,725 12,908 Accrued expenses 47,520 19,331 Other 26,580 21,922 483,239 347,791 Valuation allowance — (359 ) Total deferred tax assets 483,239 347,432 Deferred tax liabilities: Unrealized gains/losses on marketable securities (3,280 ) (28,186 ) Fixed assets (5,559 ) — Convertible senior notes — (252 ) Other (12,455 ) (3,578 ) Total deferred tax liabilities (21,294 ) (32,016 ) Net deferred tax assets $ 461,945 $ 315,416
Schedule Of Unrecognized Tax Benefits Roll Forward	The following table summarizes the gross amounts of unrecognized tax benefits. The amount of unrecognized tax benefits that, if settled, would impact the effective tax rate is $102.1 million , $51.2 million , and $23.5 million as of December 31, 2015, 2014, and 2013, respectively. 2015 2014 2013 Balance as of January 1 $ 57,615 $ 26,627 $ 11,274 Gross increases related to current year tax positions 59,909 27,538 7,620 Gross (decreases) increases related to prior year tax positions (952 ) 6,464 8,305 Gross decrease due to settlements, recapture, filed returns, and lapse of statutes of limitation — (3,014 ) (572 ) Balance as of December 31 $ 116,572 $ 57,615 $ 26,627

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic and Diluted Net Income (Loss) Per Share	The calculations of basic and diluted net income per share are as follows: Year Ended December 31, 2015 2014 2013 Net income - basic and diluted $ 636,056 $ 338,126 $ 413,738 (Shares in thousands) Weighted average shares - basic 103,061 100,612 97,917 Effect of dilutive securities: Stock options 9,446 9,440 10,233 Restricted stock 477 425 433 Warrants 2,246 2,936 2,707 Dilutive potential shares 12,169 12,801 13,373 Weighted average shares - diluted 115,230 113,413 111,290 Net income per share - basic $ 6.17 $ 3.36 $ 4.23 Net income per share - diluted $ 5.52 $ 2.98 $ 3.72
Antidilutive Securities	Shares which have been excluded from diluted per share amounts because their effect would have been antidilutive, include the following: Year Ended December 31, (Shares in thousands) 2015 2014 2013 Stock options 1,343 1,470 304 Convertible senior notes 994 4,247 4,761

Unaudited Quarterly Results (Ta

Unaudited Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Summarized quarterly financial data for the years ended December 31, 2015 and 2014 are set forth in the following tables. First Quarter Ended March 31, 2015 Second Quarter Ended June 30, 2015 Third Quarter Ended September 30, 2015 Fourth Quarter Ended December 31, 2015 (Unaudited) Revenues $ 869,612 $ 998,617 $ 1,137,422 $ 1,098,077 Net income $ 76,021 $ 194,643 $ 210,398 $ 154,994 Net income per share - basic $ 0.74 $ 1.89 $ 2.04 $ 1.49 Net income per share - diluted $ 0.66 $ 1.69 $ 1.82 $ 1.34 First Quarter Ended March 31, 2014 * Second Quarter Ended June 30, 2014 * Third Quarter Ended September 30, 2014 * Fourth Quarter Ended December 31, 2014 * (Unaudited) Revenues $ 625,740 $ 665,700 $ 725,788 $ 802,329 Net income (1) $ 68,305 $ 96,351 $ 83,375 $ 90,095 Net income per share - basic $ 0.69 $ 0.96 $ 0.83 $ 0.89 Net income per share - diluted $ 0.61 $ 0.85 $ 0.73 $ 0.78 * Certain revisions have been made to the amounts originally reported for quarterly periods ended March 31, June 30, September 30, and December 31, 2014. See Note 14. (1) Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.

Business Overview and Summary43

Business Overview and Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax asset, reclassification		$ 46,200,000
Reduction in deferred revenue		41,000,000
Decrease in total cash from financing		9,300,000	$ 4,900,000
Reduction in accounts receivable		41,000,000
Reduction in income tax assets, net		$ 14,200,000
Concentration risk, percentage	68.00%	70.00%
Increase in total cash from operating		$ 9,300,000	4,900,000
Reduction in APIC		14,200,000
Revenue Recognition [Abstract]
Percentage of prompt pay discount the company accrues	100.00%
Concentration Risks, Types, No Concentration Percentage [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 0	0
Provision for Doubtful Accounts	$ 0	$ 0	$ 0
Building and improvements | Minimum
Estimated useful life	10 years
Building and improvements | Maximum
Estimated useful life	30 years
Laboratory and other equipment | Minimum
Estimated useful life	3 years
Laboratory and other equipment | Maximum
Estimated useful life	10 years
Furniture and Fixtures [Member] | Maximum
Estimated useful life	5 years

Net Product Sales (Details)

Net Product Sales (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue Disclosure [Line Items]
Branded Prescription Drug Fee		$ 40,600
Net product sales	$ 2,689,478	$ 1,750,762	$ 1,425,839
Risks and Uncertainties [Abstract]
Concentration risk, percentage	68.00%	70.00%
Activity of Sales Related Deductions [Roll Forward]
Balance	$ 55,249	$ 24,781	24,601	$ 18,826
Provision related to current period sales	193,190	111,855	89,875
Credits/payments	(162,722)	(111,675)	(84,100)
Rebates and Chargebacks
Activity of Sales Related Deductions [Roll Forward]
Balance	6,419	3,083	4,400	2,983
Provision related to current period sales	61,124	33,117	25,936
Credits/payments	(57,788)	(34,434)	(24,519)
Distribution Related Fees
Activity of Sales Related Deductions [Roll Forward]
Balance	48,313	21,166	19,663	15,298
Provision related to current period sales	122,466	77,160	62,984
Credits/payments	(95,319)	(75,657)	(58,619)
Other Sales Related Deductions
Activity of Sales Related Deductions [Roll Forward]
Balance	517	532	538	$ 545
Provision related to current period sales	9,600	1,578	955
Credits/payments	$ (9,615)	$ (1,584)	$ (962)
Customer concentration risk | Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	67.00%	73.00%	76.00%
EYLEA
Revenue Disclosure [Line Items]
Net product sales	$ 2,676,000	$ 1,736,400	$ 1,408,700
ARCALYST
Revenue Disclosure [Line Items]
Net product sales	$ 13,500	$ 14,400	$ 17,100

Collaboration Agreements (Sanof

Collaboration Agreements (Sanofi) (Details) $ in Thousands	1 Months Ended				3 Months Ended		12 Months Ended
	Jul. 31, 2015USD ($)	Jul. 31, 2014USD ($)	Nov. 30, 2009USD ($)	Nov. 30, 2007USD ($)	Mar. 31, 2015USD ($)	Jun. 30, 2013USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Collaboration Agreements [Line Items]
Accounts receivable - trade, net									$ 1,152,489	$ 739,379
Deferred revenue from Sanofi, current portion									101,573	15,927
Research and Development Expense									1,620,577	1,271,353	$ 859,947
Revenue from Related Parties									$ 758,873	$ 541,299	430,111
Period for Achieving Sales Target for Milestone Payment, Rolling Basis										12 months
Collaboration Agreement with Sanofi
Collaboration Agreements [Line Items]
Common Stock, shares issued (in shares) | shares									23,108,570
IO Agreement [Member]
Collaboration Agreements [Line Items]
Deferred Revenue, Additions									$ 640,000
Antibody Collaboration
Collaboration Agreements [Line Items]
Accounts receivable - trade, net									126,687	$ 110,559
Deferred revenue from Sanofi, current portion									84,237	64,408
Contingent reimbursement obligation									1,832,000
Recognition of Deferred Revenue									10,243	10,243	10,243
Net profit (loss) from commercialization of products under collaboration agreement									(240,042)	(41,378)	0
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned									735,439	547,761	453,489
Contracts Revenue									157,350	19,480	1,868
Research and Development Asset Acquired Other than Through Business Combination, Written-off									0	0	(20,000)
License agreement term	3 years
Research and Development Expense									92,600	109,700	17,600
Revenue from Related Parties									$ 662,990	536,106	$ 445,600
Proceeds from Collaborators				$ 85,000
Percentage of repayment of development balance out of profits									50.00%
Minimum advance notice required to terminate collaboration agreement									3 months
Annual funding maximum of research activities per amended agreement			$ 160,000						$ 145,000
Reduction of Funding for Research Activities Per Agreement	$ 75,000
Substantive milestone payment to the Company									$ 10,000
Percentage of Trial Costs borne by collaborating party									80.00%
Percentage of Trial Costs borne by entity									20.00%
Percentage of trial costs to be reimbursed due to profitability of agreement									30.00%
Excess Share of profit not required to to be applied to reimburse development cost									10.00%
Starting share of profits outside the United States, based on sales, for collaborating party									65.00%
Starting share of profits outside the United States, based on sales, for Company									35.00%
Ending share of profits outside the United States, based on sales, for collaborating party									55.00%
Ending share of profits outside the United States, based on sales, for Company									45.00%
Share of losses outside the United States, for collaborating party									55.00%
Share of losses outside the United States, for Company									45.00%
Maximum amount of sales milestone payments if total sales achieve specific levels									$ 250,000
Starting specified levels of annual sales at which sales milestone payments may be received									$ 1,000,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis									12 months
Amount of funding of agreed-upon cost incurred to expand manufacturing capacity			$ 30,000
Maximum amount of reimbursement related to capital expenditures										17,500
Interest Receivable									$ 13,200
Period of Notice to Opt Out of Further Development and or Commercialization									12 months
Period of Notice to Opt Out of Further Development Upon Entering of Joint Development Product									30 days
Number of families of novel antibodies											2
Payments for Purchase of Other Assets		$ 67,500
Immuno-oncology Agreement [Member]
Collaboration Agreements [Line Items]
Accounts receivable - trade, net									$ 21,394	0
Deferred revenue from Sanofi, current portion									600,000	0
Recognition of Deferred Revenue									40,000	0	$ 0
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned									39,961	0	0
Revenue from Related Parties									79,961	$ 0	0
Sanofi
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off		$ (33,800)
VelociGene Agreement
Collaboration Agreements [Line Items]
Minimum payment received under the agreement									21,500
PDGF
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off						$ (10,000)
Number of Payments the Company made										2
Other Research and Development Expense									10,000	$ 5,000
Potential future milestone payments									20,000
Ang2
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off						$ (10,000)
ZALTRAP Agreement
Collaboration Agreements [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement									0	(4,715)	(30,810)
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned									686	4,806	5,639
Contracts Revenue									15,236	5,102	9,682
Percentage of development cost for the territory outside the United States to be paid for under the collaboration					50.00%
Deferred Revenue, Revenue Recognized					$ 14,900
Revenue from Related Parties									15,922	$ 5,193	$ (15,489)
Other Revenue, Net									$ 38,800
IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
License agreement term	5 years
Deferred Revenue, Additions	$ 265,000
Potential future R&D expenses	1,090,000
Funding Maximum of Research Activities Per Agreement	$ 825,000
Additional years to extend the agreement	3 years
Excess Share of profit not required to to be applied to reimburse development cost	10.00%
IO License and Collaboration Agreement [Member]
Collaboration Agreements [Line Items]
Deferred Revenue, Additions	$ 375,000
Excess Share of profit not required to to be applied to reimburse development cost	10.00%
Period of Notice to Opt Out of Further Development and or Commercialization	12 months
New Funding [Member] | IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
Funding Maximum of Research Activities Per Agreement	$ 750,000
Previous Funding under Antibody Discovery Agreement [Member] | IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
Funding Maximum of Research Activities Per Agreement	75,000
PD-1 [Member] | IO License and Collaboration Agreement [Member]
Collaboration Agreements [Line Items]
Levels of twelve month sales at which sales milestone payments would be received	2,000,000
Maximum amount of shared development costs	650,000
Maximum amount of sales milestone payments if total sales achieve specific levels	$ 375,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis	12 months
Minimum | ZALTRAP Agreement
Collaboration Agreements [Line Items]
Percentage of aggregate net sales to be paid by the related party in such calendar year					15.00%
Maximum | ZALTRAP Agreement
Collaboration Agreements [Line Items]
Percentage of aggregate net sales to be paid by the related party in such calendar year					30.00%
Scenario, Forecast [Member] | Antibody Collaboration
Collaboration Agreements [Line Items]
Annual funding maximum of research activities per amended agreement							$ 130,000	$ 130,000
Subsequent Event [Member] | Antibody Collaboration
Collaboration Agreements [Line Items]
License agreement term							3 years

Collaboration Agreements (Bayer

Collaboration Agreements (Bayer HealthCare LLC) (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Aug. 31, 2007	Oct. 31, 2006	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaboration Agreements [Line Items]
Accounts receivable from Bayer HealthCare			$ 162,152	$ 125,483
Deferred revenue, current portion			153,487	74,025
Other Collaboration Revenue			580,488	495,555	$ 220,289
Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreement [Abstract]
Contingent reimbursement obligation			$ 258,000
Collaboration Agreements [Line Items]
Deferred Revenue, Additions	$ 20,000	$ 75,000
Royalty rate minimum			33.50%
Royalty rate maximum			40.00%
Net profit (loss) from commercialization of products under collaboration agreement			$ 466,667	301,302	101,494
Revenue Recognition, Milestone Method, Revenue Recognized			15,000	105,000	70,000
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned			8,887	23,383	20,905
Contracts Revenue			69,466	52,390	27,890
Other Collaboration Revenue			560,020	482,075	220,289
EYLEA
Collaboration Agreements [Line Items]
Accounts receivable from Bayer HealthCare			160,755	124,293
Deferred revenue, current portion			46,694	28,752
PDGFR-beta outside the US
Collaboration Agreements [Line Items]
Deferred Revenue, Additions				2,500
Accounts receivable from Bayer HealthCare			1,397	1,191
Deferred revenue, current portion			9,522	19,909
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned			10,075	2,848	0
Contracts Revenue			10,393	10,632	0
Other Collaboration Revenue			$ 20,468	$ 13,480	$ 0

Collaboration Agreements (EYLEA

Collaboration Agreements (EYLEA) (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Aug. 31, 2007	Oct. 31, 2006	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaboration Agreements [Line Items]
Period for Achieving Sales Target for Milestone Payment, Rolling Basis					12 months
Levels of twelve month sales at which sales milestone payments were received					$ 500,000
level of twelve months sales at which sales milestone payments maybe received - 100 million					100,000
Accounts receivable from Bayer HealthCare				$ 162,152	125,483
Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Percentage of repayment of development balance out of profits				50.00%
Contingent reimbursement obligation				$ 258,000
Revenue Recognition, Milestone Method, Revenue Recognized				15,000	105,000	$ 70,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis						12 months
Levels of twelve months sales at which sales milestone payments were received - 200 million				200,000
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned				8,887	23,383	$ 20,905
Proceeds from Collaborators	$ 20,000	$ 75,000
Other Research and Development Expense				$ 13,700	18,600	15,300
Deferred Revenue, Additions	$ 20,000	$ 75,000
BRVO
Collaboration Agreements [Line Items]
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned			$ 15,700
Marketing Approval | Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized						15,000
Pricing Approval | Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized						10,000
starting at sales achievement - $200 million
Collaboration Agreements [Line Items]
Period for Achieving Sales Target for Milestone Payment, Rolling Basis				12 months
starting at sales achievement - $200 million | Collaboration Agreement with Bayer HealthCare LLC
Collaboration Agreements [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized						45,000
Levels of twelve months sales at which sales milestone payments were received - 200 million						$ 200,000
starting at sales achievement - $500 million
Collaboration Agreements [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized					90,000
sales achievement - 200 million
Collaboration Agreements [Line Items]
Maximum amount of sales milestone payments if total sales achieve specific levels					$ 15,000
sales achievement - 100 million
Collaboration Agreements [Line Items]
Period for Achieving Sales Target for Milestone Payment, Rolling Basis					12 months
Maximum amount of sales milestone payments if total sales achieve specific levels				$ 15,000

Collaboration Agreements (PDGFR

Collaboration Agreements (PDGFR-beta Antibody) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Collaboration Agreements [Line Items]
Accounts receivable from Bayer HealthCare	$ 162,152	$ 125,483
PDGFR-beta outside the US
Collaboration Agreements [Line Items]
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions	20.00%
Percentage of global development cost to be paid by the collaboration partner under the collaboration	25.00%
Percentage of development cost for the territory outside the United States to be paid for under the collaboration	50.00%
Percentage of development milestone payments to be reimbursed	50.00%
Number of development milestone payments the Company received		2
Deferred Revenue, Additions		$ 2,500
Substantive milestone payment to the Company	$ 5,000
Future development milestone payment the Company is eligible to receive	10,000
Opt in payment	20,000
Amount of milestone payment that may be received relating to marketing approval	20,000
Accounts receivable from Bayer HealthCare	$ 1,397	1,191
Proceeds from Collaborators		$ 25,500

Collaboration Agreements (Mitsu

Collaboration Agreements (Mitsubishi Tanabe Pharma) (Details) - Mitsubishi Tanabe Pharma Corporation (MTPC) [Member] - Collaborative Arrangement [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Mar. 31, 2016	Dec. 31, 2015
Collaboration Agreements [Line Items]
Deferred Revenue, Additions	$ 10
Future development milestone payment the Company is eligible to receive			$ 65
Contingent payments Company could receive			105
Collaborative Arrangement, Additional Eligible Aggregate Payments			100
Starting specified levels of annual sales at which sales milestone payments may be received			$ 200
Maximum
Collaboration Agreements [Line Items]
Collaborative Arrangement, Purchase Price, Percentage of Net Product Sales			50.00%
Minimum
Collaboration Agreements [Line Items]
Collaborative Arrangement, Purchase Price, Percentage of Net Product Sales			30.00%
Subsequent Event [Member]
Collaboration Agreements [Line Items]
Deferred Revenue, Additions		$ 45

Technology Licensing Agreemen50

Technology Licensing Agreements (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Aug. 31, 2010	Mar. 31, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Revenue Arrangement [Line Items]
Technology licensing revenue			$ 74,889	$ 31,941	$ 28,506
License Agreement with Astellas Pharma Inc.
Deferred Revenue Arrangement [Line Items]
Non-exclusive license agreement term		6 years
Advance payment received due to amended licensing agreement	$ 165,000
Recognition period for advance payment	7 years
Future payment to be made under terms of amended licensing agreement			$ 130,000
Number of days of advance written notice to terminate agreement			90 days
Technology licensing revenue			$ 23,600	23,600	$ 23,600
Deferred Revenue			$ 57,400	$ 81,000

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains		$ 1,200	$ 1,000
Amortized Cost Basis	$ 856,429	631,477
Unrealized Gains	14,622	81,989
Unrealized (Losses)	(2,769)	(1,551)
Total fair value of available-for-sale marketable securities	868,282	711,915
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Maturities within one year	236,121	251,761
Maturities after one year through five years	600,695	360,208
Maturities after five years through ten years	0	1,128
Total	836,816	613,097
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	731,331	426,941
Fair Value - 12 Months or Greater	23,749	0
Fair Value - Total	755,080	426,941
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(2,677)	(1,551)
Unrealized Loss- 12 Months or Greater	(92)	0
Unrealized Loss - Total	(2,769)	(1,551)
Available-for-sale Securities, Gross Realized Losses		0	0
Unrestricted
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	548,322	616,477
Unrealized Gains	392	5,550
Unrealized (Losses)	(447)	(1,551)
Total fair value of available-for-sale marketable securities	548,267	620,476
U.S. government and government agency obligations
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	51,215	25,549
Fair Value - 12 Months or Greater	0	0
Fair Value - Total	51,215	25,549
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(193)	(46)
Unrealized Loss- 12 Months or Greater	0	0
Unrealized Loss - Total	(193)	(46)
U.S. government and government agency obligations | Unrestricted
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	51,402	28,596
Unrealized Gains	0	3
Unrealized (Losses)	(193)	(46)
Total fair value of available-for-sale marketable securities	51,209	28,553
Corporate bonds
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	668,199	390,613
Fair Value - 12 Months or Greater	23,749	0
Fair Value - Total	691,948	390,613
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(2,473)	(1,462)
Unrealized Loss- 12 Months or Greater	(92)	0
Unrealized Loss - Total	(2,565)	(1,462)
Corporate bonds | Unrestricted
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	770,092	548,832
Unrealized Gains	156	136
Unrealized (Losses)	(2,565)	(1,462)
Total fair value of available-for-sale marketable securities	767,683	547,506
Municipal Bonds [Member]
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	11,917	10,779
Fair Value - 12 Months or Greater	0	0
Fair Value - Total	11,917	10,779
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(11)	(43)
Unrealized Loss- 12 Months or Greater	0	0
Unrealized Loss - Total	(11)	(43)
Municipal Bonds [Member] | Unrestricted
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	17,930	37,044
Unrealized Gains	5	37
Unrealized (Losses)	(11)	(43)
Total fair value of available-for-sale marketable securities	17,924	37,038
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments	0	0	$ 2,900
Equity Securities [Member] | Unrestricted
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	17,005	2,005
Unrealized Gains	14,461	5,374
Unrealized (Losses)	0	0
Total fair value of available-for-sale marketable securities	$ 31,466	7,379
Equity Securities [Member] | Restricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis		15,000
Unrealized Gains		76,439
Unrealized (Losses)		0
Total fair value of available-for-sale marketable securities		$ 91,439

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2011
Available-for-sale marketable securities:
Total fair value of available-for-sale marketable securities	$ 868,282,000	$ 711,915,000
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	91,400,000	0
Convertible Debt [Abstract]
Liabilities, Current	$ 811,162,000	654,660,000
Convertible senior notes
Convertible Debt [Abstract]
Convertible Debt, Noncurrent		$ 169,400,000
Interest rate, stated percentage	1.875%	1.875%		1.875%
Fair value of the outstanding notes	$ 72,800,000	$ 819,800,000
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other than Temporary Impairment Losses, Investments	0	0	$ 0
Significant Unobservable Inputs (Level 3)
Available-for-sale marketable securities:
Marketable Securities, Unrealized Gain (Loss)	0	0
Unrestricted
Available-for-sale marketable securities:
Total fair value of available-for-sale marketable securities	548,267,000	620,476,000
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale marketable securities:
Total fair value of available-for-sale marketable securities	31,466,000	7,379,000
Measured on a recurring basis | Significant Other Observable Inputs (Level 2)
Available-for-sale marketable securities:
Total fair value of available-for-sale marketable securities	836,816,000	704,536,000
Measured on a recurring basis | Unrestricted | Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale marketable securities:
Available-for-sale Securities, Equity Securities	31,466,000	7,379,000
Total fair value of available-for-sale marketable securities		7,379,000
Measured on a recurring basis | Unrestricted | Significant Other Observable Inputs (Level 2)
Available-for-sale marketable securities:
Financial Instruments, Owned, Corporate Debt, at Fair Value	767,683,000	547,506,000
U.S. government and government agency obligations	51,209,000	28,553,000
Municipal Debt Securities, at Carrying Value	17,924,000	37,038,000
Total fair value of available-for-sale marketable securities		613,097,000
Measured on a recurring basis | Restricted [Member]
Available-for-sale marketable securities:
Available-for-sale Securities, Equity Securities		91,439,000
Measured on a recurring basis | Restricted [Member] | Significant Other Observable Inputs (Level 2)
Available-for-sale marketable securities:
Available-for-sale Securities, Equity Securities		91,439,000
Fair Value | Measured on a recurring basis
Available-for-sale marketable securities:
Total fair value of available-for-sale marketable securities	868,282,000	711,915,000
Fair Value | Measured on a recurring basis | Unrestricted
Available-for-sale marketable securities:
Financial Instruments, Owned, Corporate Debt, at Fair Value	767,683,000	547,506,000
U.S. government and government agency obligations	51,209,000	28,553,000
Municipal Debt Securities, at Carrying Value	17,924,000	37,038,000
Available-for-sale Securities, Equity Securities	$ 31,466,000	7,379,000
Total fair value of available-for-sale marketable securities		$ 620,476,000

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Raw materials	$ 59,151	$ 10,923
Work in process	132,068	73,519
Finished goods	11,197	10,768
Deferred costs	36,162	33,651
Total Inventories	238,578	128,861
Inventory write-downs and reserves	$ 10,600	$ 6,000	$ 9,100

Property, Plant, and Equipmen54

Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Land	$ 77,826	$ 2,768
Buildings and Improvements, Gross	760,517	398,981
Leasehold Improvements, Gross	95,226	42,600
Construction in Progress, Gross	579,834	472,231
Property, plant, and equipment, gross	1,925,216	1,228,293
Furniture and Fixtures, Gross	81,381	58,655
Less: accumulated depreciation and amortization	(331,096)	(253,984)
Property, plant, and equipment, net	1,594,120	974,309
Depreciation and amortization expense	74,909	52,686	$ 41,204
New Laboratory and Office Facilities
Property, Plant and Equipment [Line Items]
Costs incurred by the landlord to construct new laboratory and office facilities	254,600	236,700
Laboratory and other equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	330,432	253,058
New land in Tarrytown, New York
Property, Plant and Equipment [Line Items]
Land	73,000
UNITED STATES
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	1,118,400	754,700
Foreign
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	$ 475,700	$ 219,600

Accounts Payable and Accrued 55

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accounts payable	$ 140,962	$ 99,508
Accrued payroll and related costs	133,223	92,778
Accrued clinical trial expense	88,297	41,555
Accrued sales-related charges, deductions and royalties	195,986	133,085
Other accrued expenses and liabilities	85,644	116,563
Accounts payable and accrued expenses	$ 644,112	$ 483,489

Deferred Revenue (Details)

Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current portion:
Deferred revenue, current portion	$ 153,487	$ 74,025
Long-term portion:
Deferred revenue, long-term portion	664,679	135,249
Received or receivable from Sanofi
Current portion:
Deferred revenue, current portion	101,573	15,927
Long-term portion:
Deferred revenue, long-term portion	582,664	62,819
Received or receivable from Bayer HealthCare
Current portion:
Deferred revenue, current portion	24,290	33,652
Long-term portion:
Deferred revenue, long-term portion	31,926	15,007
Received for technology license agreement
Current portion:
Deferred revenue, current portion	23,572	23,572
Long-term portion:
Deferred revenue, long-term portion	33,851	57,423
Other
Current portion:
Deferred revenue, current portion	4,052	874
Long-term portion:
Deferred revenue, long-term portion	$ 16,238	$ 0

Debt (Details)

Debt (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended			12 Months Ended
	Nov. 30, 2015	Feb. 28, 2015	Nov. 30, 2014	Oct. 31, 2011	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Treasury Stock, Value						$ 306,069		$ 306,069	$ 169,530
Net carrying amount of the liability component [Abstract]
Treasury Stock, Shares						3,642,820		3,642,820	2,017,732
Warrants [Abstract]
Adjustments to Additional Paid in Capital, Other								$ (449,456)	$ (294,552)
Payments for Repurchase of Warrants								573,487	294,552	$ 0
Maximum reduction of warrants held by warrant holder	476,376		493,229
Fair Value Adjustment of Warrants									1,200
Maximum amount of warrant payable								23,317	148,496
Maximum share price for warrant holders to close out hedge position	$ 535		$ 397.75
Convertible Debt [Abstract]
Debt Conversion									230,600
Repayments of Convertible Debt								$ 166,467	$ 220,639	0
Stock Issued During Period, Shares, New Issues								1,625,113	2,017,732
Loss on Extinguishment of Debt								$ 18,861	$ 33,469	0
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments								$ 819,657	$ 691,869
Warrant
Warrants [Abstract]
Strike price of the warrant transaction (in dollars per share)				$ 103.41
Proceeds received from the Warrant				$ 93,800
Reduction of number of warrants						115,970	416,480	898,547	1,220,745
Payments for Repurchase of Warrants		$ 124,000				$ 50,000		$ 399,500	$ 294,600
warrants outstanding								2,109,098
Accounts Payable, Other						0		$ 0	59,800	0
Liabilities, Fair Value Adjustment						0		0	87,500	0
Call option
Convertible Debt [Abstract]
Purchase of convertible note hedges				$ 117,500
Convertible senior notes
Debt Instrument [Line Items]
Treasury Stock, Value						$ 136,500		$ 136,500	$ 169,500
Interest rate, stated percentage				1.875%		1.875%		1.875%	1.875%
Initial conversion price (in dollars per share)				$ 84.02
Percentage of principal value that holders can require Company to repurchase				100.00%
Estimated fair value of the liability component				$ 271,100
Carrying amount of equity component				120,900
Gross proceeds from the issuance of the Notes				$ 392,000
Effective interest rate used to amortize the discount on the liability component						10.20%		10.20%
Net carrying amount of the liability component [Abstract]
Convertible Debt						$ 11,154		$ 11,154	$ 169,400
Unamortized discount						(352)		(352)	(22,627)
Convertible Notes Payable						$ 10,802		$ 10,802	146,773
Treasury Stock, Shares						1,625,088		1,625,088
Interest Expense, Debt [Abstract]
Contractual coupon interest rate								$ 544	5,036	7,230
Amortization of discount and note issuance costs								2,818	17,821	22,980
Total interest expense								3,362	22,857	$ 30,210
Convertible Debt [Abstract]
If-converted value in excess of principal								70,400
Credit Facility [Domain]
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity							$ 750,000
Line of Credit Facility, Expiration Period							5 years
Available increase to the credit facility							$ 250,000
Line of Credit Facility, Current Borrowing Capacity						$ 100,000		100,000
Additional Paid-in Capital
Warrants [Abstract]
Adjustments to Additional Paid in Capital, Other							$ 23,300	(449,456)	(294,552)
Maximum amount of warrant payable								23,317	148,496
Convertible Debt [Abstract]
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments								$ 819,657	$ 691,869
Subsequent Event [Member] | Warrant
Warrants [Abstract]
Reduction of number of warrants					360,406
Payments for Repurchase of Warrants					$ 135,300

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)building	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Operating Leased Assets [Line Items]
Rent Charges for Utilities, Real Estate Taxes, and Operating Expense	$ 15,500	$ 13,600	$ 11,500
Operating Leases [Abstract]
Lease renewal escalation percentage	2.50%
Commitments under operating leases [Abstract]
2,015	$ 15,488
2,016	11,757
2,017	11,747
2,018	11,740
2,019	11,375
Thereafter	50,746
Total	112,853
Rent expense under operating leases [Abstract]
Rent expense under operating leases	15,202	14,312	9,875
Facilities
Commitments under operating leases [Abstract]
2,015	10,894
2,016	11,332
2,017	11,607
2,018	11,740
2,019	11,375
Thereafter	50,746
Total	107,694
Rent expense under operating leases [Abstract]
Rent expense under operating leases	14,659	13,360	9,404
Equipment
Commitments under operating leases [Abstract]
2,015	4,594
2,016	425
2,017	140
2,018	0
2,019	0
Thereafter	0
Total	5,159
Rent expense under operating leases [Abstract]
Rent expense under operating leases	$ 543	$ 952	$ 471
Facilities - Buildings A and B
Operating Leases [Abstract]
Number of new buildings leased | building	2

Commitments and Contingencies59

Commitments and Contingencies - Facility Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Facility Leases [Line Items]
2,015	$ 31,176
2,016	31,913
2,017	32,667
2,018	33,442
2,019	34,234
Thereafter	308,935
Total	472,367
Facility lease obligations [Abstract]
Interest expense in connection with facility lease obligation	9,700	$ 14,500	$ 16,200
Commitments under facility leases [Abstract]
Facility lease obligation, including reimbursements	364,708	312,292
Facilities - Buildings A and B
Schedule of Facility Leases [Line Items]
2,015	13,809
2,016	14,079
2,017	14,356
2,018	14,640
2,019	14,931
Thereafter	117,096
Total	$ 188,911
Facility lease obligations [Abstract]
Imputed interest rate applicable to facility lease obligation	11.00%
Commitments under facility leases [Abstract]
Facility lease obligation, including reimbursements	$ 108,857	110,210
Facilities - Building C
Schedule of Facility Leases [Line Items]
2,015	4,688
2,016	4,818
2,017	4,951
2,018	5,088
2,019	5,227
Thereafter	54,760
Total	$ 79,532
Facility lease obligations [Abstract]
Imputed interest rate applicable to facility lease obligation	10.00%
Commitments under facility leases [Abstract]
Facility lease obligation, including reimbursements	$ 49,475	49,312
Facilities Building D and E
Schedule of Facility Leases [Line Items]
2,015	12,679
2,016	13,016
2,017	13,360
2,018	13,714
2,019	14,076
Thereafter	137,079
Total	$ 203,924
Facility lease obligations [Abstract]
Imputed interest rate applicable to facility lease obligation	7.00%
Commitments under facility leases [Abstract]
Facility lease obligation, including reimbursements	$ 206,376	$ 152,770

Commitments and Contingencies60

Commitments and Contingencies - Research Collaboration and Licensing Agreements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Agreements with Royalty Provisions
Research Collaboration and Licensing Arrangements [Line Items]
Royalty rate minimum	0.50%
Royalty rate maximum	16.50%
Royalty expense	$ 247.9	$ 169.9	$ 128.1
License agreement with Genentech - EYLEA
Research Collaboration and Licensing Arrangements [Line Items]
First payment made or maybe made upon reaching minimum sales target				$ 60
Cumulative relevant sales minimum sales target				$ 400
Cumulative sales range, 1st tier minimum	400
Sales range maximum 1st tier	3,000
Cumulative sales range, 2nd tier minimum	$ 3,000
Royalty payment percentage of cumulative sales within cumulative sales range	4.75%
Royalty payment percentage of cumulative sales over range	5.50%

Stockholders' Equity (Details)

Stockholders' Equity (Details)	1 Months Ended				12 Months Ended
	Nov. 30, 2015shares	Nov. 30, 2014shares	Oct. 31, 2011USD ($)	Dec. 31, 2007shares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)	Mar. 31, 2015shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares) | shares					30,000,000	30,000,000
Number of demand rights to require the Company to conduct registered underwritten public offering					3
Debt Conversion						$ 230,600,000
Total convertible senior notes - par							$ 400,000,000
Repayments of Convertible Debt					$ 166,467,000	220,639,000	0
Gains (Losses) on Extinguishment of Debt					(18,861,000)	(33,469,000)	0
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments					819,657,000	691,869,000
Payments for Repurchase of Warrants					573,487,000	294,552,000	$ 0
Maximum reduction of warrants held by warrant holder | shares	476,376	493,229
Maximum amount of warrant payable					$ 23,317,000	$ 148,496,000
Call option
Class of Stock [Line Items]
Purchase of convertible note hedges			$ 117,500,000
Convertible senior notes
Class of Stock [Line Items]
Total convertible senior notes - par			$ 400,000,000
Sanofi
Class of Stock [Line Items]
Number of shares of Common Stock purchased | shares				12,000,000
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions					30.00%
Percentage Of Outstanding Shares Or Voting Rights Under Amended Investor Agreement					20.00%
Percentage Of Outstanding Shares that the Company is required to appoint an individual agreed upon by the Company and the Collaborator to the Company's board of directors					20.00%
Class A Stock
Class of Stock [Line Items]
Common Stock, shares authorized (in shares) | shares					40,000,000	40,000,000
Common Stock, par value (in dollars per share) | $ / shares					$ 0.001	$ 0.001
Common Stock, voting rights					ten votes per share
Common Stock
Class of Stock [Line Items]
Common Stock, shares authorized (in shares) | shares					320,000,000			160,000,000
Common Stock, par value (in dollars per share) | $ / shares					$ 0.001	$ 0.001
Common Stock, voting rights					one vote per share
Debt Conversion, Converted Instrument, Shares Issued | shares					1,625,000	2,018,000
Bayer Collaboration Agreement - PDGFR-beta outside the US
Class of Stock [Line Items]
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions					20.00%
Additional Paid-in Capital
Class of Stock [Line Items]
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments					$ 819,657,000	$ 691,869,000
Maximum amount of warrant payable					$ 23,317,000	$ 148,496,000

Long-Term Incentive Plans (Deta

Long-Term Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation										$ 459,049	$ 321,750	$ 215,377
Selling, general, and administrative										838,526	519,267	346,393
Deferred Tax Assets, Net, Noncurrent	$ 461,945				$ 315,416					461,945	315,416
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Assets	5,609,132				3,837,672					5,609,132	3,837,672
Additional paid-in capital	3,099,526				2,450,782					3,099,526	2,450,782
Retained Earnings (Accumulated Deficit)	852,700				216,644					852,700	216,644
Stockholders' Equity Attributable to Parent	3,654,837				2,550,251					3,654,837	2,550,251	1,964,716	$ 1,256,618
Liabilities and Equity	5,609,132				3,837,672					5,609,132	3,837,672
Costs and Expenses										2,851,812	1,995,638	1,361,695
Operating Income (Loss)										1,251,916	823,919	743,050
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										1,225,097	761,235	696,382
Income Tax Expense (Benefit)										589,041	423,109	282,644
Net Income	$ 154,994	$ 210,398	$ 194,643	$ 76,021	$ 90,095	$ 83,375	[1]	$ 96,351	$ 68,305	$ 636,056	$ 338,126	$ 413,738
Earnings Per Share, Basic	$ 1.49	$ 2.04	$ 1.89	$ 0.74	$ 0.89	$ 0.83		$ 0.96	$ 0.69	$ 6.17	$ 3.36	$ 4.23
Net income per share - diluted	$ 1.34	$ 1.82	$ 1.69	$ 0.66	$ 0.78	$ 0.73		$ 0.85	$ 0.61	$ 5.52	$ 2.98	$ 3.72
Increase (Decrease) in Deferred Income Taxes										$ 121,623	$ 53,276	$ (62,195)
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of awards										10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of shares outstanding at beginning of period				21,506,260						21,506,260
Number of shares granted										4,495,487	3,913,368	3,937,989
Number of shares forfeited										(318,952)
Number of shares expired										(363)
Number of shares exercised										(2,516,663)
Number of shares outstanding at end of period	23,165,769				21,506,260					23,165,769	21,506,260
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average exercise price - outstanding at beginning of period				$ 158.54						$ 158.54
Weighted average exercise price - granted										537.29	$ 385.33	$ 263.77
Weighted average exercise price - forfeited										292.14
Weighted average exercise price - expired										92.20
Weighted average exercise price - exercised										98.26
Weighted average exercise price - outstanding at end of period	$ 236.75				$ 158.54					$ 236.75	$ 158.54
Weighted average remaining contractual term (in years) - outstanding										6 years 9 months 24 days
Instrinsic value - outstanding	$ 7,209,994,851									$ 7,209,994,851
Number of shares vested and expected to vest	22,635,728									22,635,728
Weighted average execise price - vested and expected to vest	$ 231.75									$ 231.75
Weighted average remaining contractual term - vested and expected to vest										6 years 9 months 5 days
Intrinsic value - vested and expected to vest	$ 7,156,754,651									$ 7,156,754,651
Number of shares exercisable	13,212,236									13,212,236
Weighted average exercise price - exercisable	$ 103.67									$ 103.67
Weighted average remaining contractual term - exercisable										5 years 2 months 23 days
Intrinsic value - exercisable	$ 5,852,659,560									$ 5,852,659,560
Total intrinsic value - of stock options exercised										$ 1,031,600	$ 1,081,200	$ 727,500
Exercise Price Equal to Market Price [Abstract]
Number of Options Granted (shares)										4,495,487	3,913,368	3,937,989
Weighted Average Exercise Price (dollars per share)										$ 537.29	$ 385.33	$ 263.77
Weighted Average Fair Value										$ 181.65	$ 140.38	$ 104.90
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility										35.00%	39.00%	42.00%
Expected lives from grant date										5 years 1 month 1 day	5 years 2 months 11 days	5 years 4 months 1 day
Expected dividend yield										0.00%	0.00%	0.00%
Risk-free interest rate										1.68%	1.62%	1.73%
Stock options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period										3 years
Stock options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period										4 years
Phantom stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period within vesting date that awards may be received										30 days
Non-performance based stock options
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Non-cash stock-based compensation expense										$ 443,700	$ 306,100	$ 193,400
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 962,600									$ 962,600
Weighted average period for recognition of total unrecognized compensation expense (in years)										2 years
Performance-based stock options
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Non-cash stock-based compensation expense											4,100	$ 8,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Share Based Compensation Arrangement By Share Based Payment Award Options Nonvested Number	0									0		770,250
Restricted stock
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Non-cash stock-based compensation expense										$ 15,300	$ 11,500	$ 14,000
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 33,900									$ 33,900
Weighted average period for recognition of total unrecognized compensation expense (in years)										2 years 1 month
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Number of shares outstanding at beginning of period				546,060						546,060
Number of shares granted										27,520
Number of shares vested										(31,880)
Number of shares outstanding at end of period	541,700				546,060					541,700	546,060
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted average grant date fair value at beginning of period				$ 115.26						$ 115.26
Weighted average grant date fair value - granted										540.40
Weighted average grant date fair value - vested										164.65
Weighted average grant date fair value at end of period	$ 133.96				$ 115.26					$ 133.96	$ 115.26
Long-Term Incentive Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance					16,485,333						16,485,333
Number of shares available for future grants	9,711,439									9,711,439
Long-Term Incentive Plan 2000 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance														35,397,043
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of shares exercised										(2,457,000)	(3,468,000)	(3,052,000)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Stockholders' Equity Attributable to Parent	$ 106				$ 102					$ 106	$ 102	$ 97	$ 95
Common Stock | Long-Term Incentive Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance					4,485,333						4,485,333
Scenario, Previously Reported [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation											$ 307,238	198,399
Selling, general, and administrative					$ 143,743						504,755	329,415
Deferred Tax Assets, Net, Noncurrent					316,104						316,104
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Assets					3,871,827						3,871,827
Additional paid-in capital					2,404,118						2,404,118
Retained Earnings (Accumulated Deficit)					255,382						255,382
Stockholders' Equity Attributable to Parent					2,542,325						2,542,325
Liabilities and Equity					3,871,827						3,871,827
Costs and Expenses					554,962						1,981,126	1,344,717
Operating Income (Loss)					247,367						838,431	760,028
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest					221,287						775,747	713,360
Income Tax Expense (Benefit)					111,111						427,673	288,998
Net Income					$ 110,176						$ 348,074	$ 424,362
Earnings Per Share, Basic					$ 1.09						$ 3.46	$ 4.33
Net income per share - diluted					$ 0.96						$ 3.07	$ 3.81
Increase (Decrease) in Deferred Income Taxes											$ (66,604)	$ 63,601
Restatement Adjustment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation											14,512	16,978
Selling, general, and administrative					$ 31,564
Deferred Tax Assets, Net, Noncurrent					22,152						22,152
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Assets					22,152						22,152
Additional paid-in capital					60,890						60,890
Retained Earnings (Accumulated Deficit)					(38,738)						(38,738)
Stockholders' Equity Attributable to Parent					22,152						22,152
Liabilities and Equity					22,152						22,152
Costs and Expenses					31,564						14,512	16,978
Operating Income (Loss)					(31,564)						(14,512)	(16,978)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest					(31,564)						(14,512)	(16,978)
Income Tax Expense (Benefit)					(11,483)
Net Income					$ (20,081)						$ (9,948)	$ (10,624)
Earnings Per Share, Basic					$ (0.20)						$ (0.10)	$ (0.10)
Net income per share - diluted					$ (0.18)						$ (0.09)	$ (0.09)
Increase (Decrease) in Deferred Income Taxes											$ (4,564)	$ (6,354)
Revised [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation											321,750	215,377
Selling, general, and administrative					$ 175,307						519,267	346,393
Deferred Tax Assets, Net, Noncurrent					338,256						338,256
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Assets					3,893,979						3,893,979
Additional paid-in capital					2,465,008						2,465,008
Retained Earnings (Accumulated Deficit)					216,644						216,644
Stockholders' Equity Attributable to Parent					2,564,477						2,564,477
Liabilities and Equity					3,893,979						3,893,979
Costs and Expenses					586,526						1,995,638	1,361,695
Operating Income (Loss)					215,803						823,919	743,050
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest					189,723						761,235	696,382
Income Tax Expense (Benefit)					99,628						423,109	282,644
Net Income					$ 90,095						$ 338,126	$ 413,738
Earnings Per Share, Basic					$ 0.89						$ 3.36	$ 4.23
Net income per share - diluted					$ 0.78						$ 2.98	$ 3.72
Increase (Decrease) in Deferred Income Taxes											$ (71,168)	$ 57,247
[1]	Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.

Employee Savings Plan (Details)

Employee Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contribution expense to 401(k) Savings Plan	$ 15.4	$ 13.1	$ 5.7

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 1,225,097	$ 761,235	$ 696,382
Current:
Federal	686,561	437,038	196,527
State	28,568	28,718	23,489
Current Foreign Tax Expense (Benefit)	4,004	2,879	433
Total current tax expense	719,133	468,635	220,449
Deferred:
Federal	(119,849)	(62,932)	53,504
State	(3,768)	18,891	8,700
Deferred Foreign Income Tax Expense (Benefit)	(6,475)	(1,485)	(9)
Total deferred tax (benefit) expense	(130,092)	(45,526)	62,195
Total income tax expense (benefit)	$ 589,041	$ 423,109	$ 282,644
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
State and local income taxes	1.00%	2.40%	3.40%
Change in state effective rate	(0.10%)	2.90%	0.00%
Foreign income tax rate differential	12.20%	15.80%	4.90%
Income tax credits	(1.60%)	(5.10%)	(4.90%)
Non-deductible Branded Prescription Drug Fee	2.00%	2.80%	1.10%
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Percent	(3.20%)	(0.00%)	(0.00%)
Other permanent differences	2.80%	1.80%	1.10%
Effective income tax rate	48.10%	55.60%	40.60%
Deferred tax assets:
Net operating loss carryforward	$ 140	$ 150
Fixed assets	0	8,078
Deferred revenue	51,766	60,223
Deferred compensation	349,508	216,640
Income tax credit carryforwards	0	8,539
Capitalized research and development costs	7,725	12,908
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	47,520	19,331
Other	26,580	21,922
Deferred tax assets, gross	483,239	347,791
Valuation allowance	0	(359)
Deferred tax assets, net	483,239	347,432
Deferred tax liabilities:
Accruals	(3,280)	(28,186)
Deferred Tax Liabilities, Property, Plant and Equipment	(5,559)	0
Convertible senior notes	0	(252)
Deferred Tax Liabilities, Other	(12,455)	(3,578)
Deferred tax liabilities, gross	(21,294)	(32,016)
Deferred Tax Assets, Net	461,945	315,416
Utilization of net operating loss carryforwards related to exercises of Nonqualified Stock Options and disqualifying dispositions of ISOs, credited to additional paid-in capital	405,317	439,278	$ 211,909
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount			34,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	102,100	51,200	23,500
Other Comprehensive Income (Loss), Tax	24,900	27,100	0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	57,615	26,627	11,274
Gross increases related to current year tax positions	59,909	27,538	7,620
Unrecognized Tax Benefits, Period Increase (Decrease)	(952)	6,464	8,305
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	0	3,014	572
Balance as of December 31	116,572	57,615	26,627
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	1,200
UNITED STATES
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	1,665,087	1,101,446	795,300
Foreign
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ (439,990)	$ (340,211)	$ (98,918)

Net Income (Loss) Per Share (De

Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 154,994	$ 210,398	$ 194,643	$ 76,021	$ 90,095	$ 83,375	[1]	$ 96,351	$ 68,305	$ 636,056	$ 338,126	$ 413,738
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding - basic										103,061	100,612	97,917
Effect of dilutive securities (in shares):
Stock options										9,446	9,440	10,233
Restricted stock										477	425	433
Warrants										2,246	2,936	2,707
Dilutive potential shares										12,169	12,801	13,373
Weighted average shares - diluted (in shares)										115,230	113,413	111,290
Earnings Per Share, Basic and Diluted [Abstract]
Net income per share - basic	$ 1.49	$ 2.04	$ 1.89	$ 0.74	$ 0.89	$ 0.83		$ 0.96	$ 0.69	$ 6.17	$ 3.36	$ 4.23
Net income per share - diluted	$ 1.34	$ 1.82	$ 1.69	$ 0.66	$ 0.78	$ 0.73		$ 0.85	$ 0.61	$ 5.52	$ 2.98	$ 3.72
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares										1,343	1,470	304
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares										994	4,247	4,761
[1]	Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.

Statement of Cash Flows (Detail

Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accrued capital expenditures	$ 50.7	$ 56.2	$ 16.1
Facilities Building D and E
Facility lease obligations recognized	26	127.8	25
Warrant
Accounts Payable, Other	0	59.8	0
Liabilities, Fair Value Adjustment	0	87.5	0
Convertible Notes Payable
Notes Payable	$ 1.6	$ 7.5	$ 0

Unaudited Quarterly Results (De

Unaudited Quarterly Results (Details) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015USD ($)$ / shares	Sep. 30, 2015USD ($)$ / shares	Jun. 30, 2015USD ($)$ / shares	Mar. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)$ / shares	Sep. 30, 2014USD ($)$ / shares		Jun. 30, 2014USD ($)$ / shares	Mar. 31, 2014USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)$ / shares	Dec. 31, 2013USD ($)$ / shares
Quarterly Financial Information Disclosure [Line Items]
Revenues	$ 1,098,077	$ 1,137,422	$ 998,617	$ 869,612	$ 802,329	$ 725,788		$ 665,700	$ 625,740	$ 4,103,728	$ 2,819,557	$ 2,104,745
Net income	$ 154,994	$ 210,398	$ 194,643	$ 76,021	$ 90,095	$ 83,375	[1]	$ 96,351	$ 68,305	$ 636,056	$ 338,126	$ 413,738
Net income per share - basic | $ / shares	$ 1.49	$ 2.04	$ 1.89	$ 0.74	$ 0.89	$ 0.83		$ 0.96	$ 0.69	$ 6.17	$ 3.36	$ 4.23
Net income per share - diluted | $ / shares	$ 1.34	$ 1.82	$ 1.69	$ 0.66	$ 0.78	$ 0.73		$ 0.85	$ 0.61	$ 5.52	$ 2.98	$ 3.72
Branded Prescription Drug Fee											$ 40,600
Antibody Collaboration
Quarterly Financial Information Disclosure [Line Items]
Number of families of novel antibodies												2
Up-front payments made to acquire full rights to antibodies										$ 0	$ 0	$ 20,000
[1]	Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.