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Three Months Ended
March 31,

(Shares in thousands)

Stock options

Restricted stock

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	Apr. 12, 2018
Entity Information [Line Items]
Entity Registrant Name	REGENERON PHARMACEUTICALS INC
Entity Central Index Key	0000872589
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		105,949,824
Class A Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		1,911,354

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,019,491	$ 812,733
Marketable securities	605,461	596,847
Accounts receivable - trade, net	1,531,936	1,538,642
Accounts Receivable from Sanofi	168,855	193,684
Accounts receivable from Bayer	243,141	242,014
Inventories	820,397	726,138
Prepaid expenses and other current assets	155,451	224,972
Total current assets	4,544,732	4,335,030
Marketable securities	1,821,985	1,486,494
Property, Plant, and Equipment, Net	2,394,727	2,358,605
Deferred tax assets	532,268	506,291
Other assets	78,984	77,866
Total assets	9,372,696	8,764,286
Current liabilities:
Accounts Payable	207,611	178,183
Accrued Liabilities and Other Liabilities	666,216	637,162
Deferred revenue from Sanofi, current portion	231,447	177,746
Deferred Revenue, Current	160,466	142,392
Total current liabilities	1,265,740	1,135,483
Capital and facility lease obligations	704,645	703,453
Deferred revenue from Sanofi	406,778	379,936
Deferred Revenue, Noncurrent	257,967	249,263
Other long-term liabilities	169,922	152,073
Total liabilities	2,805,052	2,620,208
Stockholders' equity:
Preferred Stock	0	0
Additional paid-in capital	3,611,599	3,512,833
Retained earnings	3,287,767	2,946,733
Accumulated other comprehensive income (loss)	(15,594)	640
Treasury stock	(316,240)	(316,240)
Total stockholders' equity	6,567,644	6,144,078
Total liabilities and stockholders' equity	9,372,696	8,764,286
Class A Stock
Stockholders' equity:
Common stock	2	2
Common Stock
Stockholders' equity:
Common stock	$ 110	$ 110

CONSOLIDATED BALANCE SHEET (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Stockholders' equity:
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)	3,763,868	3,763,868
Class A Stock
Stockholders' equity:
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)	1,911,354	1,911,354
Common Stock, shares outstanding (in shares)	1,911,354	1,911,354
Common Stock
Stockholders' equity:
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	320,000,000	320,000,000
Common Stock, shares issued (in shares)	109,703,771	109,477,222

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Net product sales	$ 987,909	$ 858,245
Sanofi collaboration revenue	189,490	210,367
Bayer Collaboration Revenue	247,928	193,939
Other revenue	86,158	56,440
Total revenues	1,511,485	1,318,991
Expenses:
Research and development	498,586	507,435
Selling, general, and administrative	330,770	296,846
Cost of goods sold	69,243	61,253
Cost of collaboration and contract manufacturing	45,655	22,915
Total expenses	944,254	888,449
Income from operations	567,231	430,542
Other income (expense):
Other income, net	24,606	9,248
Interest Expense	(6,439)	(7,501)
Total other income (expense)	18,167	1,747
Income before income taxes	585,398	432,289
Income tax expense	(107,418)	(183,358)
Net income	$ 477,980	$ 248,931
Net income per share - basic	$ 4.44	$ 2.36
Net income per share - diluted	$ 4.16	$ 2.16
Weighted average shares outstanding - basic	107,648	105,572
Weighted average shares outstanding - diluted	114,906	115,106
Statements of Comprehensive Income
Net income	$ 477,980	$ 248,931
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on marketable securities	(11,080)	6,956
Unrealized gain on cash flow hedges	1,439	0
Comprehensive income	$ 468,339	$ 255,887

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 477,980	$ 248,931
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,358	38,115
Non-cash compensation expense	82,422	133,789
Other non-cash charges and expenses, net	(4,193)	3,956
Deferred taxes	(6,366)	(40,988)
Changes in assets and liabilites
Decrease (increase) in Sanofi, Bayer, and trade accounts receivable	30,408	(137,928)
Increase in Inventories	(88,760)	(69,744)
Decrease (increase) in prepaid expenses and other assets	68,836	(20,325)
(Decrease) increase in deferred revenue	(54,596)	12,400
Increase in accounts payable, accrued expenses and other liabilities	76,654	187,695
Total adjustments	140,763	106,970
Net cash provided by operating activities	618,743	355,901
Cash flows from investing activities:
Purchases of marketable securities	(601,313)	(208,694)
Sales or maturities of marketable securities	255,276	119,012
Capital expenditures	(79,375)	(50,461)
Net cash used in investing activities	(425,412)	(140,143)
Cash flows from financing activities:
Proceeds in connection with capital and facility lease obligations	0	57,000
Payments in connection with capital and facility lease obligations	0	(12,861)
Proceeds from issuance of Common Stock	13,427	16,673
Net cash provided by financing activities	13,427	60,812
Net increase in cash, cash equivalents, and restricted cash	206,758	276,570
Cash, cash equivalents, and restricted cash at beginning of period	825,233	547,703
Cash, cash equivalents, and restricted cash at end of period	$ 1,031,991	$ 824,273

Interim Financial Statements (Notes)

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Interim Financial Statements

The interim Condensed Consolidated Financial Statements of Regeneron Pharmaceuticals, Inc. and its subsidiaries ("Regeneron," "Company," "we," "us," and "our") have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all information and disclosures necessary for a presentation of the Company's financial position, results of operations, and cash flows in conformity with accounting principles generally accepted in the United States of America. In the opinion of management, these financial statements reflect all normal recurring adjustments and accruals necessary for a fair statement of the Company's financial position, results of operations, and cash flows for such periods. The results of operations for any interim period are not necessarily indicative of the results for the full year. The December 31, 2017 Condensed Consolidated Balance Sheet data were derived from audited financial statements, but do not include all disclosures required by accounting principles generally accepted in the United States of America. These financial statements should be read in conjunction with the financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Certain reclassifications have been made to prior period amounts to conform with the current period's presentation.

We adopted Accounting Standards Codification ("ASC") 606, Revenue from Contracts with Customers, as of January 1, 2018. The Company adopted the standard using the modified retrospective method, and thus recognized a cumulative-effect adjustment to reduce Retained earnings and increase Deferred revenue on January 1, 2018 by $143.4 million, net of tax. Prior period amounts have not been adjusted in connection with the adoption of this standard.

The new standard did not have an impact on the recognition of revenue from product sales (see Note 2). However, the new standard has resulted in certain changes to the timing of revenue recognition related to our collaboration agreements (see Note 3). As a result of adopting ASC 606, non-refundable upfront payments, which were previously recognized ratably over the performance period, and substantive development milestones, which were previously recognized in the period when the milestone was achieved, will be recognized over the remaining performance period based on the Company's progress towards satisfying its identified performance obligation.

The following tables summarize the impacts of adopting ASC 606 on the Company's condensed consolidated financial statements for the three months ended March 31, 2018 as compared with the guidance that was in effect before the change.



	March 31, 2018
Balance Sheet Data	As Reported		Adjustments			Balance Without Adoption of ASC 606
Deferred tax assets	$	532,268	$	(18,206	)	$	514,062
Total assets	$	9,372,696	$	(18,206	)	$	9,354,490
Accrued expenses and other current liabilities	$	666,216	$	(1,513	)	$	664,703
Deferred revenue from Sanofi (current)	$	231,447	$	(33,632	)	$	197,815
Deferred revenue - other (current)	$	160,466	$	(69,241	)	$	91,225
Total current liabilities	$	1,265,740	$	(104,386	)	$	1,161,354
Deferred revenue from Sanofi (noncurrent)	$	406,778	$	(51,604	)	$	355,174
Deferred revenue - other (noncurrent)	$	257,967	$	18,277		$	276,244
Total liabilities	$	2,805,052	$	(137,713	)	$	2,667,339
Retained earnings	$	3,287,767	$	119,507		$	3,407,274
Total stockholders' equity	$	6,567,644	$	119,507		$	6,687,151
Total liabilities and stockholders' equity	$	9,372,696	$	(18,206	)	$	9,354,490



	Three Months Ended March 31, 2018
Consolidated Statement of Operations Data	As Reported			Adjustments			Balance Without Adoption of ASC 606
Sanofi collaboration revenue	$	189,490		$	(8,407	)	$	181,083
Other revenue	$	86,158		$	(17,310	)	$	68,848
Total revenues	$	1,511,485		$	(25,717	)	$	1,485,768
Income from operations	$	567,231		$	(25,717	)	$	541,514
Income before income taxes	$	585,398		$	(25,717	)	$	559,681
Income tax expense	$	(107,418	)	$	1,789		$	(105,629	)
Net income	$	477,980		$	(23,928	)	$	454,052

The Company also adopted Accounting Standards Update ("ASU") 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, as of January 1, 2018. The amendments require companies to measure equity investments at fair value with changes in fair value recognized in net income. We have elected the measurement alternative for equity investments we hold that do not have readily determinable fair values. Therefore, we will measure such investments at cost minus impairment, if any, and adjust for observable price changes in orderly transactions for identical or similar investments of the same issuer. Upon adoption, the Company recognized a cumulative-effect adjustment, related to unrealized gains on equity securities, to reduce Accumulated other comprehensive income and increase Retained earnings on January 1, 2018 by $6.6 million. See Note 5 and Note 6.

Net Product Sales (Notes)

3 Months Ended

Mar. 31, 2018

Revenues [Abstract]

Product Sales and Concentration Risk [Text Block]

Product Sales

Net product sales consist of the following:



	Three Months Ended March 31,
Net Product Sales in the United States	2018		2017
EYLEA^®	$	984,049	$	854,387
ARCALYST^®	3,860		3,858
	$	987,909	$	858,245

The Company had product sales to certain customers that accounted for more than 10% of total gross product revenue for the three months ended March 31, 2018 and 2017. Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows:



	Three Months Ended March 31,
	2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	55	%	53	%
McKesson Corporation	40	%	27	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		19	%
** For the three months ended March 31, 2018, sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue.

Revenue from product sales is recognized at a point in time when our customer is deemed to have obtained control of the product, which generally occurs upon receipt by our distributors and specialty pharmacies. The Company's written contracts with its customers stipulate product is shipped freight on board destination (FOB destination).

The amount of revenue we recognize varies due to rebates and chargebacks provided under governmental and other programs, distribution-related fees, and other sales-related deductions. We estimate the amount of variable consideration that we will be entitled to, in order to determine the transaction price, based upon contracts with customers and government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, estimated payer mix, and other relevant factors.

The following table summarizes the provisions, and credits/payments, for these sales-related deductions during the three months ended March 31, 2018 and 2017.



	Rebates & Chargebacks			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2017	$	29,840		$	34,142		$	21,320		$	85,302
Provisions	48,495			51,716			11,170			111,381
Credits/payments	(30,674		)	(42,025		)	(14,665		)	(87,364		)
Balance as of March 31, 2018	$	47,661		$	43,833		$	17,825		$	109,319

Balance as of December 31, 2016	$	12,712		$	29,465		$	3,674		$	45,851
Provisions	38,908			41,175			9,520			89,603
Credits/payments	(28,502		)	(42,287		)	(8,632		)	(79,421		)
Balance as of March 31, 2017	$	23,118		$	28,353		$	4,562		$	56,033

Accruals for chargebacks are recorded as a direct reduction to accounts receivable and accruals for rebates and distribution-related fees are recorded within accrued liabilities.

Collaboration Agreements (Notes)

3 Months Ended

Mar. 31, 2018

Collaboration Agreement [Abstract]

Collaboration Agreements

We have entered into various agreements related to our activities to research, develop, manufacture, and commercialize product candidates and utilize our technology platforms. The Company earns collaboration revenue in connection with collaboration agreements to utilize our technology platforms and develop and/or commercialize product candidates. As described in Note 1, during the first quarter of 2018, we adopted ASC 606. Under the terms of the new standard, revenue is measured as the amount of consideration we expect to be entitled to in exchange for transferring promised goods or providing services to a customer, and is recognized when (or as) we satisfy performance obligations under the terms of a contract. Depending on the terms of the arrangement, we may defer the recognition of all or a portion of the consideration received because the performance obligations are satisfied over time.

Our collaboration agreements may require us to deliver various rights, services, and/or goods across the entire life cycle of a product or product candidate. In agreements involving multiple goods or services promised to be transferred to customer, we must assess, at the inception of the contract, whether each promise represents a separate performance obligation (i.e., is "distinct"), or whether such promises should be combined as a single performance obligation.

The terms of these agreements typically include consideration to be provided to the Company in the form of non-refundable up-front payments, development milestones, payments for development activities, as well as payments for commercialization activities, sales milestones, and sharing of profits or losses arising from the commercialization of products.

At the inception of the contract, the transaction price reflects the amount of consideration we expect to be entitled to in exchange for transferring promised goods or services to our customer. We review our estimate of the transaction price each period, and make revisions to such estimates as necessary. In arrangements where we satisfy performance obligation(s) during the development phase over time, we recognize collaboration revenue over time typically using an input method on the basis of our research and development costs incurred relative to the total expected cost which determines the extent of our progress toward completion.

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 as they are deemed to be the principal in the transaction. The Company shares in any profits or losses arising from the commercialization of such products, and records its share of the variable consideration, representing net product sales less cost of goods sold and shared commercialization and other expenses, as collaboration revenue in the period in which such underlying sales occur and costs are incurred by the collaborator.

In arrangements where the collaborator records product sales, the Company may be obligated to use commercially reasonable efforts to supply commercial bulk product to its collaborators, and may be 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. In addition, we may also be reimbursed for a portion of costs incurred for other commercial-related activities, which are recorded as collaboration revenue in the period in which such costs are incurred.

a. Sanofi

The collaboration revenue we earned from Sanofi is detailed below:



	Three Months Ended March 31,
Sanofi Collaboration Revenue	2018			2017
Antibody:
Reimbursement of Regeneron research and development expenses	$	60,394		$	155,245
Reimbursement of Regeneron commercialization-related expenses	85,424			73,559
Regeneron's share of losses in connection with commercialization of antibodies	(74,874		)	(108,402		)
Other	17,330			11,286
Total Antibody	88,274			131,688
Immuno-oncology:
Reimbursement of Regeneron research and development expenses	73,824			58,679
Reimbursement of Regeneron commercialization-related expenses	1,210			—
Other	26,182			20,000
Total Immuno-oncology	101,216			78,679
	$	189,490		$	210,367

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 was governed by the companies' Discovery and Preclinical Development Agreement ("Antibody Discovery Agreement") and a License and Collaboration Agreement (each as amended). Pursuant to the Antibody Discovery Agreement, Sanofi agreed to fund up to $130.0 million of the Company's research activities in 2017. The Company's Antibody Discovery Agreement with Sanofi ended on December 31, 2017 without any extension and, therefore, funding from Sanofi under the Antibody Discovery Agreement ceased after 2017. Under the License and Collaboration Agreement, agreed-upon worldwide development expenses incurred by both companies 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, during the three months ended March 31, 2018 and 2017, the Company recognized as research and development expense $13.9 million and $25.0 million, respectively, its share of antibody development expenses that Sanofi incurred related to Praluent^®(alirocumab), Kevzara^® (sarilumab), and Dupixent^® (dupilumab).

Effective January 7, 2018, the Company and Sanofi entered into a letter agreement (the "Letter Agreement") in connection with, among other matters, the allocation of additional funds to certain activities relating to the development of dupilumab and REGN3500 and non-approval trials of dupilumab (collectively, the "Dupilumab/REGN3500 Eligible Investments"). Refer to the "Immuno-Oncology" section below for further details regarding the Letter Agreement.

In March 2017, the U.S. Food and Drug Administration ("FDA") approved Dupixent for the treatment of adult patients with moderate-to-severe atopic dermatitis, and in September 2017, the European Commission granted marketing authorization for Dupixent for use in adults with moderate-to-severe atopic dermatitis who are candidates for systemic therapy. In May 2017, the FDA approved Kevzara for the treatment of adult patients with moderately to severely active rheumatoid arthritis, and in June 2017, the European Commission granted marketing authorization for Kevzara for the treatment of rheumatoid arthritis in adult patients.

Sanofi leads commercialization activities for products developed under the Antibody Collaboration, subject to the Company's right to co-promote such products. In addition to profit and loss sharing, the Company is entitled to receive up to $250.0 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. The amount of variable consideration related to such share of profits and losses and sales milestones is deemed to be constrained as of March 31, 2018, and therefore has not been included in the transaction price.

The Company's significant promised goods and services consist of providing research and development services, including the manufacturing of clinical supplies, and providing commercial-related services, including the manufacturing of commercial supplies. As it relates to the Antibody Collaboration, "Reimbursement of Regeneron commercialization-related expenses" in the table above represents reimbursement of internal and external costs in connection with commercializing Praluent, Kevzara, and Dupixent. As we recognize Sanofi antibody collaboration revenue in an amount equal to the amount we have the right to invoice and such amount corresponds directly with the value to Sanofi of our performance to date, we do not disclose the value of the transaction price allocated to our remaining unsatisfied performance obligations.

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's Antibody Collaboration with Sanofi:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	94,022	$	121,001
Deferred revenue	$	132,991	$	117,682

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase due to shipments of commercial supplies to Sanofi	$	37,036
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(21,727	)

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. 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 our budget for IO Discovery activities, which has been agreed to with Sanofi, 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.

In connection with the IO License and Collaboration Agreement, Sanofi made a $375.0 million non-refundable up-front payment to the Company. Under the terms of the IO License and Collaboration Agreement, the parties are co-developing the Company's antibody product candidate (cemiplimab) targeting the receptor known as programmed cell death protein 1 (PD-1). The parties share equally, on an ongoing basis, development expenses for cemiplimab up to a total of $1.640 billion, an increase of $990.0 million over the budget set forth in the original IO License and Collaboration Agreement. The cemiplimab development budget has been increased pursuant to the Letter Agreement. Pursuant to the Letter Agreement, the Company has agreed to allow Sanofi to satisfy in whole or in part its funding obligations with respect to cemiplimab development and Dupilumab/REGN3500 Eligible Investments by selling up to an aggregate of 1,400,000 shares of the Company's Common Stock directly or indirectly owned by Sanofi through September 30, 2020. If Sanofi desires to sell shares of the Company's Common Stock during the term of the Letter Agreement to satisfy a portion or all of its funding obligations for the cemiplimab development and/or Dupilumab/REGN3500 Eligible Investments, the Company may elect to purchase, in whole or in part, such shares from Sanofi. If the Company does not elect to purchase such shares, Sanofi may sell the applicable number of shares (subject to certain daily and quarterly limits) in one or more open-market transactions.

The Company has principal control over the development of cemiplimab 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 global sales of certain licensed products targeting PD-1 (including cemiplimab), together with sales of any other products licensed under the IO License and Collaboration Agreement and sold for use in combination with any of such licensed products targeting PD-1, equal or exceed $2.0 billion in any consecutive twelve-month period. The amount of variable consideration related to such milestone is deemed to be constrained as of March 31, 2018, and therefore has not been included in the transaction price.

At the inception of the IO Collaboration, the Company's significant promised goods and services consisted of a license to certain rights and intellectual property and providing research and development services, including the manufacturing of clinical supplies. The Company concluded that the license was not distinct, primarily as a result of (i) Sanofi being unable to benefit from the license on its own or together with other resources that are readily available as the license provides access to Regeneron's complex and specialized know-how and (ii) the research and development services, including manufacturing in support of such services, were expected to significantly modify the initial license. Therefore the promised goods and services were considered a single performance obligation. Consequently, the $640.0 million in aggregate up-front payments made by Sanofi during 2015 in connection with the execution of the IO Collaboration has been recorded as deferred revenue and has been included in the transaction price at the inception of the contract. "Other" Sanofi immuno-oncology revenue in the Sanofi Collaboration Revenue table above primarily includes recognition of deferred revenue from $640.0 million of up-front payments.

As it relates to the IO Collaboration, "Reimbursement of Regeneron commercialization-related expenses" in the table above represents reimbursement of costs in connection with the commercialization of cemiplimab outside of the United States.

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's IO Collaboration with Sanofi:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	70,887	$	59,274
Deferred revenue	$	505,235	$	440,000

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase as a result of cumulative-effect adjustment arising from the adoption of ASC 606	$	93,643
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(28,408	)

The aggregate amount of the transaction price under the IO Collaboration allocated to the Company's performance obligation that was unsatisfied (or partially unsatisfied) as of March 31, 2018 was $1,656.0 million. This amount is expected to be recognized as revenue over the remaining period the Company is obligated to satisfy its performance obligation in connection with performing development activities.

b. Bayer

EYLEA outside the United States

Revenue earned in connection with our EYLEA collaboration with Bayer is detailed below:



	Three Months Ended March 31,
Bayer EYLEA Collaboration Revenue	2018		2017
EYLEA:
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	232,068	$	174,876
Reimbursement of Regeneron EYLEA development expenses	3,457		2,451
Other	11,863		10,603
Total EYLEA	$	247,388	$	187,930

Under the terms of the license and collaboration agreement with Bayer for the global development and commercialization outside the United States of EYLEA, Bayer markets EYLEA outside the United States, where, for countries other than Japan, the companies share equally in profits and losses from sales of EYLEA. In Japan, the Company is entitled to receive a tiered percentage of between 33.5% and 40.0% of EYLEA net sales. In addition, the Company and Bayer share the funding of agreed-upon EYLEA development costs.

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's EYLEA collaboration with Bayer:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	243,141	$	241,153
Deferred revenue	$	70,378	$	68,734

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase due to shipments of commercial supplies to Bayer	$	11,436
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(9,792	)

Ang2 antibody and PDGFR-beta antibody outside the United States

In 2016, the Company entered into an agreement with Bayer governing the joint development and commercialization outside the United States of nesvacumab, an antibody product candidate to angiopoietin-2 (Ang2), including REGN910-3 (Ang2 in combination with aflibercept), for the treatment of ocular diseases or disorders. In connection with the agreement, Bayer made a non-refundable up-front payment and paid a portion of our global development costs and development costs exclusively for the territory outside the United States. In the fourth quarter of 2017, the Company reported that results from two Phase 2 studies of REGN910-3 did not provide sufficient differentiation to warrant Phase 3 development. Therefore, during the fourth quarter of 2017, the Company accelerated and recognized the remaining amount of deferred revenue from the $50.0 million up-front payment (which was initially recorded as deferred revenue) received from Bayer as the Company deemed its performance obligation to be satisfied.

In 2014, the Company entered into a license and collaboration agreement with Bayer governing the joint development and commercialization outside the United States of an antibody product candidate to Platelet Derived Growth Factor Receptor Beta (PDGFR-beta), including REGN2176-3, a combination product candidate comprised of an antibody to PDGFR-beta co-formulated with aflibercept. Effective in the first quarter of 2017, the Company discontinued clinical development of REGN2176-3, and on July 31, 2017, the Company and Bayer agreed to terminate this collaboration agreement.

c. Teva

In September 2016, the Company and Teva entered into a collaboration agreement (the "Teva Collaboration Agreement") to develop and commercialize fasinumab globally, excluding certain Asian countries that are subject to our collaboration agreement with Mitsubishi Tanabe Pharma Corporation. In connection with the Teva Collaboration Agreement, Teva made a $250.0 million non-refundable up-front payment in September 2016. The Company leads global development activities, and the parties share development costs equally, on an ongoing basis, under a global development plan. The Company is also responsible for the manufacture and supply of fasinumab globally.

In 2017, the Company earned, and recognized as substantive milestones, development milestones of $25.0 million and $35.0 million, respectively, from Teva upon initiation of two Phase 3 trials. In addition, the Company is entitled to receive up to an aggregate of $400.0 million in development milestones and up to an aggregate of $1,890.0 million in contingent payments upon achievement of specified annual net sales amounts. The amount of variable consideration related to such milestones is deemed to be constrained as of March 31, 2018, and therefore has not been included in the transaction price.

At the inception of the Teva Collaboration Agreement, the Company's significant promised goods and services consisted of a license to certain rights and intellectual property and providing research and development services, including the manufacturing of clinical supplies. The Company concluded that the license was not distinct, primarily as a result of (i) Teva being unable to benefit from the license on its own or together with other resources that are readily available as the license providing access to Regeneron's complex and specialized know-how and (ii) the research and development services, including manufacturing in support of such services, were expected to significantly modify the initial license. Therefore the promised goods and services were considered a single performance obligation. Consequently, the $250.0 million up-front payment and development milestones received from Teva, as described above, have been recorded as deferred revenue and have been included in the transaction price.

The Company recognized $58.6 million and $33.1 million of revenue for the three months ended March 31, 2018 and 2017, respectively, in connection with the Teva Collaboration Agreement.

The following tables summarize accounts receivable and deferred revenue information in connection with the Teva Collaboration Agreement:



	March 31,		December 31,
	2018		2017
Accounts receivable, net (recorded within Prepaid expenses and other current assets)	$	40,625	$	71,297
Deferred revenue	$	227,714	$	197,357

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase as a result of cumulative-effect adjustment arising from the adoption of ASC 606	$	48,216
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(18,917	)

The aggregate amount of the transaction price under the Teva Collaboration Agreement allocated to the Company's performance obligation that was unsatisfied (or partially unsatisfied) as of March 31, 2018 was $686.0 million. This amount is expected to be recognized as revenue over the remaining period the Company is obligated to satisfy its performance obligation in connection with performing development activities.

In April 2018, an independent Data Monitoring Committee monitoring the ongoing safety and efficacy of our fasinumab clinical trials recommended that the higher dose-regimens be discontinued based on the risk benefit assessment and that the program may continue with the lower dose-regimens of fasinumab. The trials are being modified accordingly, which may ultimately impact the transaction price allocated to the remaining performance obligation.

Net Income Per Share (Notes)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

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:



	Three Months Ended March 31,
	2018		2017
Net income - basic and diluted	$	477,980	$	248,931

(Shares in thousands)
Weighted average shares - basic	107,648		105,572
Effect of dilutive securities:
Stock options	7,244		9,050
Restricted stock	14		484
Dilutive potential shares	7,258		9,534
Weighted average shares - diluted	114,906		115,106

Net income per share - basic	$	4.44	$	2.36
Net income per share - diluted	$	4.16	$	2.16

Shares which have been excluded from diluted per share amounts because their effect would have been antidilutive include the following:

Marketable Securities (Notes)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable securities as of March 31, 2018 and December 31, 2017 consist of both available-for-sale debt securities of investment grade issuers (see below and Note 6) as well as equity securities of publicly traded companies (see Note 6).

The following tables summarize the Company's investments in available-for-sale debt securities:



	Amortized		Unrealized					Fair
As of March 31, 2018	Cost Basis		Gains		Losses			Value
Available-for-sale debt securities:
Corporate bonds	$	2,126,820	$	1,948	$	(18,159	)	$	2,110,609
U.S. government and government agency obligations	156,281		30		(1,611		)	154,700
Municipal bonds	2,591		—		(11		)	2,580
Commercial paper	70,385		—		—			70,385
Certificates of deposit	20,097		—		—			20,097
	$	2,376,174	$	1,978	$	(19,781	)	$	2,358,371

As of December 31, 2017
Available-for-sale debt securities:
Corporate bonds	$	1,717,976	$	2,176	$	(7,672	)	$	1,712,480
U.S. government and government agency obligations	186,699		34		(1,241		)	185,492
Municipal bonds	4,600		—		(13		)	4,587
Commercial paper	106,973		—		—			106,973
Certificates of deposit	11,024		—		—			11,024
	$	2,027,272	$	2,210	$	(8,926	)	$	2,020,556

The Company classifies its investments in debt securities based on their contractual maturity dates. The debt securities listed as of March 31, 2018 mature at various dates through March 2023. The fair values of debt security investments by contractual maturity consist of the following:



	March 31, 2018		December 31, 2017
Maturities within one year	$	605,461	$	593,783
Maturities after one year through five years	1,752,910		1,426,773
	$	2,358,371	$	2,020,556

The following table shows the fair value of the Company's debt 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 March 31, 2018	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	1,343,778	$	(13,950	)	$	234,258	$	(4,209	)	$	1,578,036	$	(18,159	)
U.S. government and government agency obligations	70,872		(623		)	76,793		(988		)	147,665		(1,611		)
Municipal bonds	2,579		(11		)	—		—			2,579		(11		)
	$	1,417,229	$	(14,584	)	$	311,051	$	(5,197	)	$	1,728,280	$	(19,781	)

As of December 31, 2017
Corporate bonds	$	930,970	$	(4,924	)	$	256,750	$	(2,748	)	$	1,187,720	$	(7,672	)
U.S. government and government agency obligations	110,532		(409		)	67,921		(832		)	178,453		(1,241		)
Municipal bonds	2,582		(10		)	2,005		(3		)	4,587		(13		)
	$	1,044,084	$	(5,343	)	$	326,676	$	(3,583	)	$	1,370,760	$	(8,926	)

There were no realized losses on sales of marketable securities, and realized gains were not material, for the three months ended March 31, 2018 and 2017.

With respect to marketable securities, for the three months ended March 31, 2018 and 2017, amounts reclassified from Accumulated other comprehensive (loss) income into Other income, net were related to realized gains on sales. The Company adopted ASU 2016-01 (see Note 1) during the first quarter of 2018; as a result, there was $9.4 million of unrealized gains on equity securities recognized during the three months ended March 31, 2018 that was recorded in Other income, net. For the three months ended March 31, 2017, there was $5.4 million of unrealized gains and losses on equity securities that was recorded in Other comprehensive income (loss).

Fair Value Measurements (Notes)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

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 March 31, 2018	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Corporate bonds	$	2,110,609	—		$	2,110,609
U.S. government and government agency obligations	154,700		—		154,700
Municipal bonds	2,580		—		2,580
Commercial paper	70,385		—		70,385
Certificates of deposit	20,097		—		20,097
Equity securities	69,075		$	69,075	—
	$	2,427,446	$	69,075	$	2,358,371

As of December 31, 2017
Available-for-sale debt securities:
Corporate bonds	$	1,712,480	—		$	1,712,480
U.S. government and government agency obligations	185,492		—		185,492
Municipal bonds	4,587		—		4,587
Commercial paper	106,973		—		106,973
Certificates of deposit	11,024		—		11,024
Equity securities	62,785		$	62,785	—
	$	2,083,341	$	62,785	$	2,020,556

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 not record any charges for other-than-temporary impairment of its Level 2 marketable securities during the three months ended March 31, 2018 and 2017. There were no transfers of marketable securities between Levels 1 or 2 classifications during the three months ended March 31, 2018 and 2017.

The fair value of interest rate swap and interest rate cap contracts, which were recorded within Other noncurrent assets, was not material as of March 31, 2018 and December 31, 2017 (see Note 8). The fair value of these contracts was determined based on Level 2 inputs, using significant inputs that are observable either directly or indirectly, including London Interbank Offered Rate ("LIBOR") and interest rate swap rates.

As of March 31, 2018, the Company had $37.5 million in equity investments that do not have a readily determinable fair value. These investments are recorded at cost within Other noncurrent assets.

- Definition

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

+ References + Details

Inventory (Notes)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Inventory

Inventories

Inventories consist of the following:



	March 31,		December 31,
	2018		2017
Raw materials	$	201,429	$	190,045
Work-in-process	374,505		302,042
Finished goods	22,848		21,791
Deferred costs	221,615		212,260
	$	820,397	$	726,138

Deferred costs represent the costs of product manufactured and shipped to the Company's collaborators for which recognition of revenue has been deferred.

Derivative Instruments (Notes)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments and Hedging Activities Disclosure [Text Block]

Derivative Instruments and Hedging Activities

The Company is exposed to market fluctuations in interest rates, including those in connection with its March 2017 lease of laboratory and office facilities in Tarrytown, New York. Commencing in the second quarter of 2017, the Company entered into interest rate swap and interest rate cap agreements to manage a portion of such interest rate risk; no new agreements of this nature were entered into during the first quarter of 2018. All of the Company's derivative instruments are utilized for risk management purposes, and are not used for trading or speculative purposes.

The Company's derivative instruments are designated as cash flow hedges for accounting purposes. Since the specific terms of the derivative instruments match those of the item being hedged, the derivative instruments are deemed to be highly effective in offsetting the changes in cash flows of the hedged item. As such, changes in the fair value of these derivatives are recorded in accumulated other comprehensive income (loss) until the underlying transaction affects earnings, and are then reclassified to earnings in the same account as the hedged transaction. The Company would record any gain or loss related to the ineffectiveness directly to earnings.

The Company assesses, both at inception and on an ongoing basis, whether derivatives used continue to be highly effective in offsetting changes in cash flows of the hedged items. The Company does not exclude any portion of the cash flow hedge contracts from the assessment of hedge effectiveness. If and when a derivative is no longer expected to be highly effective, hedge accounting is discontinued.

The following table summarizes the notional amounts of the Company's outstanding interest rate swap and cap agreements:



	March 31,		December 31,
	2018		2017
Interest rate swap contracts	$	75,000	$	75,000
Interest rate cap contracts	$	75,000	$	75,000

As it relates to cash flow hedges, for the three months ended March 31, 2018, amounts of gains and losses recognized in Other comprehensive income (loss), and amounts reclassified from Accumulated other comprehensive (loss) income into Interest expense were not material. As of March 31, 2018, the amounts expected to be reclassified out of Accumulated other comprehensive income into Interest expense over the next 12 months are not expected to be material. For the three months ended March 31, 2018, there were no gains or losses recorded related to the ineffective portion of the derivative instruments.

Income Taxes (Notes)	3 Months Ended
Income Taxes (Notes)	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state, and foreign income taxes. The Company recorded an income tax provision in its Statement of Operations of $107.4 million and $183.4 million for the three months ended March 31, 2018 and 2017, respectively. The Company's effective tax rate was 18.3% and 42.4% for the three months ended March 31, 2018 and 2017, respectively. On December 22, 2017, the bill known as the "Tax Cuts and Jobs Act" (the "Act") was signed into law. The Act, which became effective with respect to most of its provisions as of January 1, 2018, significantly revised U.S. corporate income tax laws by, among other things, reducing the U.S. federal corporate income tax rate from 35% to 21%, changing the taxation of foreign earnings (including taxation of certain global intangible low-taxed income ("GILTI")), allowing for a foreign-derived intangible income deduction and immediate expensing for qualified assets, repealing the deduction for domestic manufacturing, and imposing further limitations on the deductibility of executive compensation. As a result of the Act being signed into law, we recognized a provisional charge of $326.2 million in the fourth quarter of 2017 related to the re-measurement of the Company's U.S. net deferred tax assets at the lower enacted corporate tax rates; such amount was not adjusted in the first quarter of 2018. The provisional charge recorded in the fourth quarter of 2017 is an estimate, and the measurement of deferred tax assets is subject to further analysis, such as developing interpretations and clarifications of the provisions of the Act, which could result in changes to this estimate during 2018. In addition, we have not yet elected an accounting method regarding whether to record deferred tax assets and liabilities for expected amounts of GILTI inclusions or whether to treat such amounts as a period cost. The Company's effective tax rate for the three months ended March 31, 2018 was positively impacted, compared to the U.S. federal statutory rate, primarily by the foreign-derived intangible income deduction and the federal tax credit for research activities. The Company's effective tax rate for the three months ended March 31, 2017 was negatively impacted, compared to the U.S. federal statutory rate, by losses incurred in foreign jurisdictions with rates lower than the U.S. federal statutory rate and the non-tax deductible Branded Prescription Drug Fee, partly offset by the tax benefit associated with stock-based compensation, the domestic manufacturing deduction, and the federal tax credit for research activities. The income tax provision recorded in the Statement of Comprehensive Income for the three months ended March 31, 2018 was not material, and there was no such income tax benefit or provision recorded for the three months ended March 31, 2017.

Statement of Cash Flows (Notes)

3 Months Ended

Mar. 31, 2018

Supplemental Cash Flow Information [Abstract]

Statement of Cash Flows

The Company adopted ASU 2016-18, Statement of Cash Flows - Restricted Cash, during the first quarter of 2018, and the standard has been retrospectively applied to all periods presented. The following provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheet to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows:



	March 31,		March 31,
	2018		2017
Cash and cash equivalents	$	1,019,491	$	811,773
Restricted cash included in Other noncurrent assets	12,500		12,500
Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows	$	1,031,991	$	824,273

Restricted cash consists of amounts held by financial institutions pursuant to contractual arrangements.

Supplemental disclosure of non-cash investing and financing activities

Included in accounts payable, accrued expenses, and other liabilities as of March 31, 2018 and December 31, 2017 were $40.2 million and $41.8 million, respectively, of accrued capital expenditures. Included in accounts payable, accrued expenses, and other liabilities as of March 31, 2017 and December 31, 2016 were $32.3 million and $28.2 million, respectively, of accrued capital expenditures.

The Company recognized an additional capital lease obligation of $201.2 million in connection with the Company's lease of additional premises at its Tarrytown, New York facility during the three months ended March 31, 2017. No such amount was recognized during the three months ended March 31, 2018.

Legal Matters (Notes)	3 Months Ended
Legal Matters (Notes)	Mar. 31, 2018
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. The outcome of any such proceedings, regardless of the merits, is inherently uncertain. If the Company were unable to prevail in any such proceedings, its consolidated financial position, results of operations, and future cash flows may be materially impacted. Proceedings Relating to '287 Patent, '163 Patent, and '018 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 engineered 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). On September 25, 2013, the Company commenced patent infringement litigation against Kymab Ltd in the English High Court of Justice, Chancery Division, Patents Court, in London, asserting the '287 Patent and '163 Patent. A trial to adjudicate the claims of infringement and counterclaims of invalidity of the '287 Patent and the '163 Patent was held from November 16, 2015 through December 8, 2015. On February 1, 2016, the court issued a final judgment, finding that the asserted claims of the '287 and '163 Patents are novel, not obvious, and infringed by Kymab's genetically engineered mice. However, the court invalidated the '287 and '163 Patents on the ground of insufficiency. The hearing for the Company's appeal and Kymab's cross-appeal was held on October 17–20, 2017. On March 28, 2018, the Court of Appeal (Civil Division of England and Wales) reversed the English High Court's decision and held that the '287 Patent and '163 Patent are both valid and infringed by Kymab. Pending issuance of the final order, the Court of Appeal has granted a pro tem injunction against Kymab, which prevents Kymab from disposing of or removing from England and Wales any infringing mice, cells, antibodies, or antibody-producing cells without the Company's consent (subject to certain exceptions). On March 11, 2014, the Company commenced '287 Patent infringement litigation and '018 Patent infringement litigation against Merus N.V., a company based in Utrecht, The Netherlands, in the District Court of The Hague (currently stayed by agreement of the parties) and the United States District Court for the Southern District of New York, respectively. On November 21, 2014, the United States District Court for the Southern District of New York issued its Opinion and Order on Claim Construction in the '018 Patent infringement litigation, in which it held the '018 Patent invalid and not infringed. On November 2, 2015, the United States District Court for the Southern District of New York issued an opinion and order finding that the '018 Patent was procured by inequitable conduct, thus rendering it unenforceable. On July 27, 2017, the United States Court of Appeals for the Federal Circuit (the "Federal Circuit") affirmed the District Court's decision regarding inequitable conduct without deciding the issues of validity and infringement. On September 12, 2017, the Company filed a petition for panel rehearing and/or rehearing en banc in the Federal Circuit. On December 26, 2017, the Federal Circuit issued an order denying the Company's petition for panel rehearing and rehearing en banc. On July 8 and July 13, 2016, notices of opposition against the '163 Patent were filed in the European Patent Office (the "EPO") by Merus N.V. and Kymab and Novo Nordisk A/S, respectively. The notices assert, as applicable, lack of novelty, lack of inventive step, and insufficiency. The Company's response to the oppositions was filed on December 30, 2016. Following an oral hearing before the Opposition Division of the EPO on February 5–7, 2018, the Opposition Division upheld the '163 Patent without amendments. Kymab filed a notice of appeal of the Opposition Division's decision on February 9, 2018. With respect to the '018 Patent infringement litigation against Merus N.V., on March 26, 2018, the United States District Court for the Southern District of New York granted Merus's motion for attorneys' fees and costs; if the Company is ultimately required to pay such fees and costs (the amount of which has not yet been determined by the court), such payment is not expected to have a material impact on the Company's financial statements. Other than as noted in the preceding sentence, the Company is not at this time able to predict the outcome of, or estimate possible gain or a range of possible loss, if any, related to, the '287 Patent, '163 Patent, and '018 Patent proceedings. Proceedings Relating to Praluent (alirocumab) Injection As described in greater detail below, the Company is currently a party to patent infringement actions initiated by Amgen Inc. against the Company and Sanofi (and/or the Company's and Sanofi's respective affiliated entities) in a number of jurisdictions relating to Praluent, which the Company is jointly developing and commercializing with Sanofi. In the United States, Amgen has asserted a number of U.S. patents, which were subsequently narrowed to U.S. Patent Nos. 8,829,165 (the "'165 Patent") and 8,859,741 (the "'741 Patent"), and seeks a permanent injunction to prevent the Company and the Sanofi defendants from commercial manufacturing, using, offering to sell, or selling within the United States (as well as importing into the United States) (collectively, "Commercializing") Praluent. 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. A jury trial in this litigation was held in the United States District Court for the District of Delaware (the "District Court") from March 8 to March 16, 2016. During the course of the trial, the District Court ruled as a matter of law in favor of Amgen that the asserted patent claims were not obvious, and in favor of the Company and the Sanofi defendants that there was no willful infringement of the asserted patent claims by the Company or the Sanofi defendants. On March 16, 2016, the jury returned a verdict in favor of Amgen, finding that the asserted claims of the '165 and '741 Patents were not invalid based on either a lack of written description or a lack of enablement. On January 3, 2017, the District Court issued a final opinion and judgment, denying the Company and the Sanofi defendants' motions for new trial and judgment as a matter of law. The District Court also denied as moot Amgen's motion to strike the Company and the Sanofi defendants' request to obtain a judgment as a matter of law, which allowed the Federal Circuit to address the Company and the Sanofi defendants' patent invalidity arguments on appeal. On January 12, 2017, the Company and the Sanofi defendants filed a notice of appeal with the Federal Circuit. On April 19, 2017, the District Court granted Amgen's motion to amend the judgment on an accounting of supplemental damages and enhancement of such damages if deemed appropriate, but deferred the order until after the Federal Circuit issued a decision on the appeal. Oral argument on the appeal was held on June 6, 2017. On October 5, 2017, the Federal Circuit reversed in part the District Court's decision, remanded for a new trial on the issues of written description and enablement, and, as discussed below, vacated the District Court's permanent injunction. In addition, it affirmed the District Court's ruling that Amgen's patents were not obvious. The Federal Circuit further concluded the Company and the Sanofi defendants were not entitled to judgment as a matter of law on the issues of written description and enablement on this record. On February 23, 2018, the Federal Circuit denied Amgen's petition for rehearing en banc, and on March 2, 2018 the Federal Circuit issued a mandate to transfer jurisdiction of the case back to the District Court. A new jury trial has been scheduled to begin on February 19, 2019. On January 5, 2017, the District Court granted a permanent injunction prohibiting Regeneron and the Sanofi defendants from Commercializing Praluent in the United States but subsequently delayed its imposition until February 21, 2017. The Federal Circuit stayed the injunction pending appeal on February 8, 2017 and vacated it on October 5, 2017. On July 25, 2016, Amgen filed a lawsuit against Regeneron, Sanofi-Aventis Groupe S.A., Sanofi-Synthelabo Limited, Aventis Pharma Limited, Sanofi Winthrop Industrie S.A., and Sanofi-Aventis Deutschland GmbH in the English High Court of Justice, Chancery Division, Patents Court, in London, seeking a declaration of infringement of Amgen's European Patent No. 2,215,124 (the "'124 Patent"), which pertains to PCSK9 monoclonal antibodies, by Praluent. The lawsuit also seeks a permanent injunction, damages, an accounting of profits, and costs and interest. On February 8, 2017, the court temporarily stayed this litigation on terms mutually agreed by the parties. Also on July 25, 2016, Amgen filed a lawsuit for infringement of the '124 Patent against Regeneron, Sanofi-Aventis Groupe S.A., Sanofi Winthrop Industrie S.A., and Sanofi-Aventis Deutschland GmbH in the Regional Court of Düsseldorf, Germany (the "Düsseldorf Regional Court"), seeking a permanent injunction, an accounting of marketing activities, a recall of Praluent and its removal from distribution channels, and damages. On November 14, 2017, the Düsseldorf Regional Court issued a decision staying the infringement proceedings until a decision of the Opposition Division of the EPO concerning the pending opposition filed by the Company, Sanofi, and several other opponents against the '124 Patent (as discussed below). Following Amgen's request to reopen the proceedings in light of the issuance of the Preliminary Opinion (as defined below), the Düsseldorf Regional Court has scheduled an oral hearing for September 11, 2018. On September 26, 2016, Amgen filed a lawsuit for infringement of the '124 Patent in the Tribunal de grande instance in Paris, France against Regeneron, Sanofi-Aventis Groupe S.A., Sanofi Winthrop Industrie, and Sanofi Chimie (subsequently added as a defendant). Amgen is seeking the prohibition of allegedly infringing activities with a €10,000 penalty per drug unit of Praluent produced in violation of the court order sought by Amgen; an appointment of an expert for the assessment of damages; disclosure of technical (including supply-chain) and accounting information to the expert and the court; provisional damages of €10.0 million (which would be awarded on an interim basis pending final determination); reimbursement of costs; publication of the ruling in three newspapers; and provisional enforcement of the decision to be issued, which would ensure enforcement of the decision (including any provisional damages) pending appeal. Amgen is not seeking a preliminary injunction in this proceeding at this time. On April 10, 2017, the Company and the Sanofi parties filed briefs seeking invalidation of certain of the claims of the '124 Patent, and Amgen filed a response on July 28, 2017. Oral hearing on this infringement lawsuit is currently scheduled for June 29, 2018. The '124 Patent is also subject to opposition proceedings in the EPO seeking to invalidate certain of its claims, which were initiated by Sanofi on February 24, 2016 and, separately, by the Company, Sanofi, and several other opponents on November 24, 2016. On December 13, 2017, the Opposition Division of the EPO issued a preliminary, non-binding opinion (the "Preliminary Opinion") regarding the validity of the '124 Patent, indicating that it currently considers the claims of a new request filed by Amgen in response to the opposition to satisfy the requirements for patentability. The Preliminary Opinion was accompanied by a summons to oral hearing to be held on November 28–30, 2018. On May 19, 2017, Amgen filed a lawsuit for infringement of Amgen's Japanese Patent Nos. 5,906,333 (the "'333 Patent") and 5,705,288 (the "'288 Patent") in the Tokyo District Court Civil Division against Sanofi K.K. Amgen's complaint alleges that manufacturing, selling or otherwise transferring, and offering to sell or otherwise transfer Praluent (alirocumab) in Japan (as well as importing Praluent (alirocumab) into Japan) infringe the '333 and '288 Patents. The complaint further seeks a permanent injunction, disposal of product, and court costs. The Company has not been named as a defendant in this litigation. At this time, the Company is not able to predict the outcome of, or estimate a range of possible loss, if any, related to these proceedings. Proceedings Relating to Dupixent (dupilumab) Injection On March 20, 2017, the Company, Sanofi-Aventis U.S. LLC, and Genzyme Corporation filed a lawsuit against Amgen and Immunex Corporation, a wholly owned subsidiary of Amgen, in the United States District Court for the District of Massachusetts seeking a declaratory judgment that the Company's and the other plaintiffs' Commercializing of Dupixent does not directly or indirectly infringe U.S. Patent No. 8,679,487 (the "'487 Patent") owned by Immunex Corporation relating to antibodies that bind the human interleukin-4 receptor. On May 1, 2017, the Company and the other plaintiffs filed a notice of voluntary dismissal of this action without prejudice. On March 23, 2017, the Company, Sanofi-Aventis U.S. LLC, and Genzyme Corporation initiated an inter partes review ("IPR") in the United States Patent and Trademark Office ("USPTO") seeking a declaration of invalidity of the '487 Patent. On July 28 and 31, 2017, the same parties filed two additional IPR petitions in the USPTO seeking declarations of invalidity of the '487 Patent based on different grounds (the "Additional IPR Petitions"). On October 4, 2017, the Patent Trial and Appeal Board ("PTAB") of the USPTO issued a decision on the first IPR petition and declined to institute an IPR proceeding to review the validity of the '487 Patent. On February 15, 2018, the PTAB issued two decisions instituting the Company's and Sanofi's Additional IPR Petitions on all claims of the '487 Patent for which review had been requested. On April 5, 2017, Immunex Corporation filed a lawsuit against the Company, Sanofi, Sanofi-Aventis U.S. LLC, Genzyme Corporation, and Aventisub LLC in the United States District Court for the Central District of California seeking a judgment of patent infringement of the '487 Patent and a declaratory judgment of infringement of the '487 Patent, in each case by the Company's and the other defendants' Commercializing of Dupixent; monetary damages (together with interest); an order of willful infringement of the '487 Patent, which would allow the court in its discretion to award damages up to three times the amount assessed; costs and expenses of the lawsuit; and attorneys' fees. Immunex is not seeking an injunction in this proceeding at this time. On June 21, 2017, the court denied a motion to dismiss Immunex's complaint previously filed by the Company and the Sanofi parties. On June 28, 2017, the Company and the Sanofi parties filed an answer to Immunex's complaint and counterclaims against Immunex and Amgen (which was amended on October 31, 2017 to, among other things, add an inequitable conduct allegation), and Immunex and Amgen filed an answer to the counterclaims on July 28, 2017. A combined hearing on the construction of certain disputed claim terms of the '487 Patent and summary judgment on the issue of indefiniteness of the '487 Patent claims was scheduled for April 27, 2018, but was later cancelled by the court. The issues of claim construction and summary judgment, among others, are still pending with the court. A jury trial has been scheduled to start on March 19, 2019. At this time, the Company is not able to predict the outcome of, or estimate a range of possible loss, if any, related to these proceedings. Proceedings Relating to EYLEA (aflibercept) Injection and ZALTRAP^® (ziv-aflibercept) Injection for Intravenous Infusion On March 19, 2018, Novartis Vaccines and Diagnostics, Inc., Novartis Pharma AG, and Grifols Worldwide Operations Limited (collectively, the "Novartis Parties") filed a lawsuit against the Company in the United States District Court for the Southern District of New York, seeking a judgment of patent infringement of U.S. Patent No. 5,688,688 (the "'688 Patent") by the Company's manufacture of aflibercept (the active ingredient used in both EYLEA and ZALTRAP); monetary damages (together with interest) for a limited period prior to the '688 Patent expiration; an order of willful infringement of the '688 Patent, which would allow the court in its discretion to award damages up to three times the amount assessed; costs and expenses of the lawsuit; and attorneys' fees. The '688 Patent expired on November 18, 2014. The Novartis Parties are not seeking an injunction in these proceedings. At this time, the Company is not able to predict the outcome of, or estimate a 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 then 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 Regeneron Pharmaceuticals, Inc. 2014 Long-Term 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. On June 28, 2017, the court dismissed the plaintiff's claims with respect to certain compensation awarded in 2013 but denied the defendants' motion to dismiss the other claims set forth in the complaint. On November 8, 2017, another alleged shareholder filed a second shareholder derivative complaint in the New York Supreme Court, naming the then 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, the Company's Chief Scientific Officer, and Regeneron as defendants. 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 2014, 2015, and 2016. The complaint seeks damages in favor of Regeneron for the alleged breaches of fiduciary duties and unjust enrichment; changes to Regeneron's corporate governance and internal procedures; invalidation of Regeneron's 2014 Long-Term Incentive Plan with respect to the individual defendants' compensation and the imposition of meaningful limits on the amount of equity payable to the individual defendants; 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. On December 4, 2017, the plaintiff in the second action moved to consolidate both actions, to be appointed lead plaintiff, and to have its counsel be appointed lead counsel in the proposed consolidated action. The court heard oral argument on March 7, 2018 and denied the motion. The parties in both the first derivative action and the second derivative action have agreed to a schedule for document discovery and the filing of defendants' appeal of the court's June 28, 2017 decision, as well as a stay of all non-document discovery pending a decision on defendants' appeal. On March 19, 2018, the defendants appealed the court's June 28, 2017 decision to the Appellate Division of the Supreme Court, First Judicial Department. On April 19, 2018, the Appellate Division granted the second plaintiff's motion to intervene in this appeal. Pursuant to the Company's By-Laws and the New York Business Corporation Law, expenses in connection with the foregoing are being advanced by the Company for the individual defendants. 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. On or about November 3, 2017, the Company received a second shareholder litigation demand upon the Company's board of directors made by another purported Regeneron shareholder, which was substantially similar to the December 15, 2015 shareholder litigation demand. The demands asserted that the then 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 demands requested 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. On December 20, 2017, the parties to the shareholder derivative action filed on December 30, 2015 entered into a stipulation with the second demanding shareholder. The stipulation provides that the purported shareholder will intervene as a plaintiff in the action, and that the purported shareholder's litigation demand will be withdrawn and deemed null and void. The stipulation was approved by the court on January 18, 2018. The first shareholder litigation demand has also since been withdrawn. At this time, the Company is not able to predict the outcome of, or estimate a range of possible loss, if any, relating to these matters. Department of Justice Investigation In January 2017, the Company received a subpoena from the U.S. Attorney's Office for the District of Massachusetts requesting documents relating to its support of 501(c)(3) organizations that provide financial assistance to patients; documents concerning its provision of financial assistance to patients with respect to products sold or developed by Regeneron (including EYLEA, Praluent, ARCALYST, and ZALTRAP); and certain other related documents and communications. The Company is cooperating with this investigation. The Company cannot predict the outcome or duration of this investigation or any other legal proceedings or any enforcement actions or other remedies that may be imposed on the Company arising out of this investigation.

Recently Issued Accounting Standards (Notes)	3 Months Ended
Recently Issued Accounting Standards (Notes)	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	Recently Issued Accounting Standards In February 2016, the FASB issued ASU 2016-02, Leases. The new standard requires a lessee to recognize on its balance sheet (for both finance and operating leases) a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. The amendments are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted. We plan to adopt this standard in the first quarter of 2019 and are evaluating the impact that this guidance will have on our financial statements, including related disclosures. The new standard will result in the Company recording additional assets and corresponding liabilities related to operating leases; however, we do not expect the standard to have a material impact to our Consolidated Balance Sheets. The ultimate impact that the new standard will have will depend on the total amount of the Company's lease commitments as of the adoption date. We are in process of implementing a new lease accounting software system, and expect the implementation of the new standard to have a significant impact on our internal controls and processes.

Legal Matters (Policies)	3 Months Ended
Legal Matters (Policies)	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Legal Costs, Policy [Policy Text Block]	Costs associated with the Company's involvement in legal proceedings are expensed as incurred.

Interim Financial Statements (Tables)

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]



	March 31, 2018
Balance Sheet Data	As Reported		Adjustments			Balance Without Adoption of ASC 606
Deferred tax assets	$	532,268	$	(18,206	)	$	514,062
Total assets	$	9,372,696	$	(18,206	)	$	9,354,490
Accrued expenses and other current liabilities	$	666,216	$	(1,513	)	$	664,703
Deferred revenue from Sanofi (current)	$	231,447	$	(33,632	)	$	197,815
Deferred revenue - other (current)	$	160,466	$	(69,241	)	$	91,225
Total current liabilities	$	1,265,740	$	(104,386	)	$	1,161,354
Deferred revenue from Sanofi (noncurrent)	$	406,778	$	(51,604	)	$	355,174
Deferred revenue - other (noncurrent)	$	257,967	$	18,277		$	276,244
Total liabilities	$	2,805,052	$	(137,713	)	$	2,667,339
Retained earnings	$	3,287,767	$	119,507		$	3,407,274
Total stockholders' equity	$	6,567,644	$	119,507		$	6,687,151
Total liabilities and stockholders' equity	$	9,372,696	$	(18,206	)	$	9,354,490



	Three Months Ended March 31, 2018
Consolidated Statement of Operations Data	As Reported			Adjustments			Balance Without Adoption of ASC 606
Sanofi collaboration revenue	$	189,490		$	(8,407	)	$	181,083
Other revenue	$	86,158		$	(17,310	)	$	68,848
Total revenues	$	1,511,485		$	(25,717	)	$	1,485,768
Income from operations	$	567,231		$	(25,717	)	$	541,514
Income before income taxes	$	585,398		$	(25,717	)	$	559,681
Income tax expense	$	(107,418	)	$	1,789		$	(105,629	)
Net income	$	477,980		$	(23,928	)	$	454,052

Net Product Sales (Tables)

3 Months Ended

Mar. 31, 2018

Revenue from External Customer [Line Items]

Revenue from External Customers by Products and Services [Table Text Block]

Net product sales consist of the following:



	Three Months Ended March 31,
Net Product Sales in the United States	2018		2017
EYLEA^®	$	984,049	$	854,387
ARCALYST^®	3,860		3,858
	$	987,909	$	858,245

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]



	Three Months Ended March 31,
	2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	55	%	53	%
McKesson Corporation	40	%	27	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		19	%
** For the three months ended March 31, 2018, sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue.

Sales Related Deductions Activity

The following table summarizes the provisions, and credits/payments, for these sales-related deductions during the three months ended March 31, 2018 and 2017.



	Rebates & Chargebacks			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2017	$	29,840		$	34,142		$	21,320		$	85,302
Provisions	48,495			51,716			11,170			111,381
Credits/payments	(30,674		)	(42,025		)	(14,665		)	(87,364		)
Balance as of March 31, 2018	$	47,661		$	43,833		$	17,825		$	109,319

Balance as of December 31, 2016	$	12,712		$	29,465		$	3,674		$	45,851
Provisions	38,908			41,175			9,520			89,603
Credits/payments	(28,502		)	(42,287		)	(8,632		)	(79,421		)
Balance as of March 31, 2017	$	23,118		$	28,353		$	4,562		$	56,033

Collaboration Agreements (Tables)

3 Months Ended

Mar. 31, 2018

Collaboration Agreement [Abstract]

Collaboration revenue with related party

The collaboration revenue we earned from Sanofi is detailed below:



	Three Months Ended March 31,
Sanofi Collaboration Revenue	2018			2017
Antibody:
Reimbursement of Regeneron research and development expenses	$	60,394		$	155,245
Reimbursement of Regeneron commercialization-related expenses	85,424			73,559
Regeneron's share of losses in connection with commercialization of antibodies	(74,874		)	(108,402		)
Other	17,330			11,286
Total Antibody	88,274			131,688
Immuno-oncology:
Reimbursement of Regeneron research and development expenses	73,824			58,679
Reimbursement of Regeneron commercialization-related expenses	1,210			—
Other	26,182			20,000
Total Immuno-oncology	101,216			78,679
	$	189,490		$	210,367

Schedule of Selected Financial Information - Antibody

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's Antibody Collaboration with Sanofi:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	94,022	$	121,001
Deferred revenue	$	132,991	$	117,682

Changes In Deferred Revenue Balance - Antibody

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase due to shipments of commercial supplies to Sanofi	$	37,036
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(21,727	)

Schedule of Selected Financial information - IO

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's IO Collaboration with Sanofi:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	70,887	$	59,274
Deferred revenue	$	505,235	$	440,000

Changes in Deferred Revenue Balance - IO

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase as a result of cumulative-effect adjustment arising from the adoption of ASC 606	$	93,643
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(28,408	)

Collaboration revenue

Revenue earned in connection with our EYLEA collaboration with Bayer is detailed below:



	Three Months Ended March 31,
Bayer EYLEA Collaboration Revenue	2018		2017
EYLEA:
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	232,068	$	174,876
Reimbursement of Regeneron EYLEA development expenses	3,457		2,451
Other	11,863		10,603
Total EYLEA	$	247,388	$	187,930

Schedule of Selected Financial Information - Bayer

The following table summarizes accounts receivable and deferred revenue information in connection with the Company's EYLEA collaboration with Bayer:



	March 31,		December 31,
	2018		2017
Accounts receivable, net	$	243,141	$	241,153
Deferred revenue	$	70,378	$	68,734

Changes In Deferred Revenue Balance - Bayer

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase due to shipments of commercial supplies to Bayer	$	11,436
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(9,792	)

Schedule of Selected Financial Information - Teva

The following tables summarize accounts receivable and deferred revenue information in connection with the Teva Collaboration Agreement:



	March 31,		December 31,
	2018		2017
Accounts receivable, net (recorded within Prepaid expenses and other current assets)	$	40,625	$	71,297
Deferred revenue	$	227,714	$	197,357

Changes in Deferred Revenue Balance - Teva

Significant changes in deferred revenue balances are as follows:



	Three Months Ended March 31, 2018
Increase as a result of cumulative-effect adjustment arising from the adoption of ASC 606	$	48,216
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(18,917	)

Net Income Per Share (Tables)

3 Months Ended

Mar. 31, 2018

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:



	Three Months Ended March 31,
	2018		2017
Net income - basic and diluted	$	477,980	$	248,931

(Shares in thousands)
Weighted average shares - basic	107,648		105,572
Effect of dilutive securities:
Stock options	7,244		9,050
Restricted stock	14		484
Dilutive potential shares	7,258		9,534
Weighted average shares - diluted	114,906		115,106

Net income per share - basic	$	4.44	$	2.36
Net income per share - diluted	$	4.16	$	2.16

Antidilutive Securities

Shares which have been excluded from diluted per share amounts because their effect would have been antidilutive include the following:

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Available-for-sale Securities

The following tables summarize the Company's investments in available-for-sale debt securities:



	Amortized		Unrealized					Fair
As of March 31, 2018	Cost Basis		Gains		Losses			Value
Available-for-sale debt securities:
Corporate bonds	$	2,126,820	$	1,948	$	(18,159	)	$	2,110,609
U.S. government and government agency obligations	156,281		30		(1,611		)	154,700
Municipal bonds	2,591		—		(11		)	2,580
Commercial paper	70,385		—		—			70,385
Certificates of deposit	20,097		—		—			20,097
	$	2,376,174	$	1,978	$	(19,781	)	$	2,358,371

As of December 31, 2017
Available-for-sale debt securities:
Corporate bonds	$	1,717,976	$	2,176	$	(7,672	)	$	1,712,480
U.S. government and government agency obligations	186,699		34		(1,241		)	185,492
Municipal bonds	4,600		—		(13		)	4,587
Commercial paper	106,973		—		—			106,973
Certificates of deposit	11,024		—		—			11,024
	$	2,027,272	$	2,210	$	(8,926	)	$	2,020,556

Marketable Securities, Based on Contractual Maturity Dates

The fair values of debt security investments by contractual maturity consist of the following:



	March 31, 2018		December 31, 2017
Maturities within one year	$	605,461	$	593,783
Maturities after one year through five years	1,752,910		1,426,773
	$	2,358,371	$	2,020,556

Fair Value and Unrealized Losses of Marketable Securities



	Less than 12 Months					12 Months or Greater					Total
As of March 31, 2018	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	1,343,778	$	(13,950	)	$	234,258	$	(4,209	)	$	1,578,036	$	(18,159	)
U.S. government and government agency obligations	70,872		(623		)	76,793		(988		)	147,665		(1,611		)
Municipal bonds	2,579		(11		)	—		—			2,579		(11		)
	$	1,417,229	$	(14,584	)	$	311,051	$	(5,197	)	$	1,728,280	$	(19,781	)

As of December 31, 2017
Corporate bonds	$	930,970	$	(4,924	)	$	256,750	$	(2,748	)	$	1,187,720	$	(7,672	)
U.S. government and government agency obligations	110,532		(409		)	67,921		(832		)	178,453		(1,241		)
Municipal bonds	2,582		(10		)	2,005		(3		)	4,587		(13		)
	$	1,044,084	$	(5,343	)	$	326,676	$	(3,583	)	$	1,370,760	$	(8,926	)

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

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 March 31, 2018	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Corporate bonds	$	2,110,609	—		$	2,110,609
U.S. government and government agency obligations	154,700		—		154,700
Municipal bonds	2,580		—		2,580
Commercial paper	70,385		—		70,385
Certificates of deposit	20,097		—		20,097
Equity securities	69,075		$	69,075	—
	$	2,427,446	$	69,075	$	2,358,371

As of December 31, 2017
Available-for-sale debt securities:
Corporate bonds	$	1,712,480	—		$	1,712,480
U.S. government and government agency obligations	185,492		—		185,492
Municipal bonds	4,587		—		4,587
Commercial paper	106,973		—		106,973
Certificates of deposit	11,024		—		11,024
Equity securities	62,785		$	62,785	—
	$	2,083,341	$	62,785	$	2,020,556

Inventory (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Schedule of Inventory, Current

Inventories consist of the following:



	March 31,		December 31,
	2018		2017
Raw materials	$	201,429	$	190,045
Work-in-process	374,505		302,042
Finished goods	22,848		21,791
Deferred costs	221,615		212,260
	$	820,397	$	726,138

Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]

The following table summarizes the notional amounts of the Company's outstanding interest rate swap and cap agreements:



	March 31,		December 31,
	2018		2017
Interest rate swap contracts	$	75,000	$	75,000
Interest rate cap contracts	$	75,000	$	75,000

Statement of Cash Flows (Tables)

3 Months Ended

Mar. 31, 2018

Supplemental Cash Flow Information [Abstract]

Restrictions on Cash and Cash Equivalents [Table Text Block]

The following provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheet to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows:



	March 31,		March 31,
	2018		2017
Cash and cash equivalents	$	1,019,491	$	811,773
Restricted cash included in Other noncurrent assets	12,500		12,500
Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows	$	1,031,991	$	824,273

Interim Financial Statements (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from Related Parties		$ 189,490	$ 210,367
Deferred tax assets		532,268		$ 506,291
Total assets		9,372,696		8,764,286
Accrued Liabilities and Other Liabilities		666,216		637,162
Deferred Revenue From Related Party Current		231,447		177,746
Deferred Revenue, Current		160,466		142,392
Liabilities, Current		1,265,740		1,135,483
Deferred Revenue From Related Party Noncurrent		(406,778)		(379,936)
Deferred Revenue, Noncurrent		257,967		249,263
Liabilities		2,805,052		2,620,208
Retained earnings		3,287,767		2,946,733
Total stockholders' equity		6,567,644		6,144,078
Liabilities and Equity		9,372,696		$ 8,764,286
Other revenue		86,158	56,440
Revenues		1,511,485	1,318,991
Operating Income (Loss)		567,231	430,542
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		585,398	432,289
Income Tax Expense (Benefit)		(107,418)	(183,358)
Net Income (Loss) Attributable to Parent		477,980	$ 248,931
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	$ 143,400
Accounting Standards Update 2016-01 [Member] \| Unrestricted [Member] \| Equity Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	(6,600)
Reclassification from AOCI to Retained Earnings	6,600
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
(Decrease) increase in deferred revenue	$ 143,400
Adjustments \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from Related Parties		(8,407)
Deferred tax assets		(18,206)
Total assets		(18,206)
Accrued Liabilities and Other Liabilities		(1,513)
Deferred Revenue From Related Party Current		(33,632)
Deferred Revenue, Current		(69,241)
Liabilities, Current		(104,386)
Deferred Revenue From Related Party Noncurrent		51,604
Deferred Revenue, Noncurrent		18,277
Liabilities		(137,713)
Retained earnings		119,507
Total stockholders' equity		119,507
Liabilities and Equity		(18,206)
Other revenue		(17,310)
Revenues		(25,717)
Operating Income (Loss)		(25,717)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		(25,717)
Income Tax Expense (Benefit)		1,789
Net Income (Loss) Attributable to Parent		(23,928)
Balance Without Adoption of ASC 606 \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from Related Parties		181,083
Deferred tax assets		514,062
Total assets		9,354,490
Accrued Liabilities and Other Liabilities		664,703
Deferred Revenue From Related Party Current		197,815
Deferred Revenue, Current		91,225
Liabilities, Current		1,161,354
Deferred Revenue From Related Party Noncurrent		(355,174)
Deferred Revenue, Noncurrent		276,244
Liabilities		2,667,339
Retained earnings		3,407,274
Total stockholders' equity		6,687,151
Liabilities and Equity		9,354,490
Other revenue		68,848
Revenues		1,485,768
Operating Income (Loss)		541,514
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		559,681
Income Tax Expense (Benefit)		(105,629)
Net Income (Loss) Attributable to Parent		$ 454,052

Net Product Sales (Details) - USD ($) $ in Thousands	3 Months Ended
Net Product Sales (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Revenue Disclosure [Line Items]
Net product sales	$ 987,909	$ 858,245
Activity of Sales Related Deductions [Roll Forward]
Balance	109,319	56,033	$ 85,302	$ 45,851
Provision related to current period sales	111,381	89,603
Credits/payments	(87,364)	(79,421)
Rebates and Chargebacks
Activity of Sales Related Deductions [Roll Forward]
Balance	47,661	23,118	29,840	12,712
Provision related to current period sales	48,495	38,908
Credits/payments	(30,674)	(28,502)
Distribution Related Fees
Activity of Sales Related Deductions [Roll Forward]
Balance	43,833	28,353	34,142	29,465
Provision related to current period sales	51,716	41,175
Credits/payments	(42,025)	(42,287)
Other Sales Related Deductions
Activity of Sales Related Deductions [Roll Forward]
Balance	17,825	4,562	$ 21,320	$ 3,674
Provision related to current period sales	11,170	9,520
Credits/payments	$ (14,665)	$ (8,632)
Besse Medical [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	55.00%	53.00%
EYLEA
Revenue Disclosure [Line Items]
Net product sales	$ 984,049	$ 854,387
ARCALYST
Revenue Disclosure [Line Items]
Net product sales	$ 3,860	$ 3,858
McKesson Corporation [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	40.00%	27.00%
Curascript SD [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage		19.00%
Minimum [Member] \| Customer concentration risk \| Gross Sales Revenue
Risks and Uncertainties [Abstract]
Concentration risk, percentage	10.00%	10.00%

Collaboration Agreements (Sanofi) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			12 Months Ended
	Jul. 31, 2015	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2017
Collaboration Agreement [Line Items]
Accounts Receivable from Sanofi		$ 168,855				$ 193,684
Revenue from Related Parties		189,490	$ 210,367
Research and development		498,586	507,435
Maximum shares the collaborator could sell						1,400,000
Antibody Collaboration
Collaboration Agreement [Line Items]
Accounts Receivable from Sanofi		94,022				$ 121,001
Deferred Revenue From Related Party		132,991				117,682
Deferred Revenue, Period Increase (Decrease)		37,036
Deferred Revenue, Revenue Recognized		(21,727)
Net profit (loss) from commercialization of products under collaboration agreement		(74,874)	(108,402)
Annual funding maximum of research activities per amended agreement						130,000
Reimbursement of Regeneron research and development expenses		60,394	155,245
Reimbursement of Regeneron commercialization-related expenses		85,424	73,559
Other		17,330	11,286
Revenue from Related Parties		$ 88,274	131,688
Percentage of Trial Costs borne by collaborating party		80.00%
Percentage of Trial Costs borne by entity		20.00%
Maximum amount of sales milestone payments if total sales achieve specific levels		$ 250,000
IO Discovery Agreement
Collaboration Agreement [Line Items]
Up-front payment received	$ 265,000
License agreement term	5 years
Additional years to extend the agreement	3 years
IO License and Collaboration Agreement
Collaboration Agreement [Line Items]
Deferred Revenue, Additions	$ 375,000
Maximum amount of shared development costs		2,000,000
Increase amount of shared development costs		990,000
IO Agreement
Collaboration Agreement [Line Items]
Up-front payment received				$ 640,000
Immuno-oncology Agreement
Collaboration Agreement [Line Items]
Revenue, Remaining Performance Obligation		1,656,000
Accounts Receivable from Sanofi		70,887				59,274
Deferred Revenue From Related Party		505,235				$ 440,000
Deferred Revenue, Period Increase (Decrease)		93,643
Deferred Revenue, Revenue Recognized		(28,408)
Reimbursement of Regeneron research and development expenses		73,824	58,679
Reimbursement of Regeneron commercialization-related expenses		1,210	0
Other		26,182	20,000
Revenue from Related Parties		101,216	78,679
Praluent, Kevzara, and Dupixent [Member] \| Antibody Collaboration
Collaboration Agreement [Line Items]
Research and development		$ 13,900	$ 25,000
Scenario, Forecast [Member] \| Antibody Collaboration
Collaboration Agreement [Line Items]
Levels of twelve month sales at which sales milestone payments would be received					$ 1,000,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis					12 months
PD-1 \| IO License and Collaboration Agreement
Collaboration Agreement [Line Items]
Maximum amount of sales milestone payments if total sales achieve specific levels	375,000
Levels of twelve month sales at which sales milestone payments would be received	$ 2,000,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis	12 months

Collaboration Agreements (Bayer) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Collaboration Agreement [Line Items]
Accounts receivable from Bayer	$ 243,141	$ 242,014
Other Collaboration Revenue	247,928		$ 193,939
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	232,068		174,876
Reimbursement of Regeneron research and development expenses	3,457		2,451
Contracts Revenue	11,863		10,603
Other Collaboration Revenue	247,388		$ 187,930
Ang2 Antibody [Member]
Collaboration Agreement [Line Items]
Up-front payment received		50,000
EYLEA
Collaboration Agreement [Line Items]
Accounts receivable from Bayer	243,141	241,153
Deferred Revenue	70,378	$ 68,734
Bayer HealthCare LLC [Member]
Collaboration Agreement [Line Items]
Deferred Revenue, Period Increase (Decrease)	11,436
Deferred Revenue, Revenue Recognized	$ (9,792)
Minimum [Member] \| EYLEA
Collaboration Agreement [Line Items]
Revenue based on percentage of annual sales in Japan	33.50%
Maximum [Member] \| EYLEA
Collaboration Agreement [Line Items]
Revenue based on percentage of annual sales in Japan	40.00%

Collaboration Agreements (Teva Agreement) (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended				12 Months Ended
	Jan. 01, 2018	Sep. 30, 2016	Sep. 30, 2016	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Prepaid expenses and other current assets				$ 155,451	$ 224,972
Teva Pharmaceuticals [Member] \| Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front payment received		$ 250,000	$ 250,000
Revenue Recognition, Milestone Method, Revenue Recognized					35,000	$ 25,000
Collaboration revenue				58,600			$ 33,100
Teva Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Prepaid expenses and other current assets				40,625	71,297
Deferred Revenue				686,000
Deferred Revenue				227,714	$ 197,357
Accounting Standards Update 2014-09 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred Revenue, Period Increase (Decrease)	$ 143,400
Accounting Standards Update 2014-09 [Member] \| Teva Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred Revenue, Period Increase (Decrease)				48,216
Deferred Revenue, Revenue Recognized				$ (18,917)
Scenario, Forecast [Member] \| Teva Pharmaceuticals [Member] \| Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative Arrangement, Additional Eligible Aggregate Payments								$ 1,890,000
Scenario, Forecast [Member] \| Teva Pharmaceuticals [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate future development milestone payments the Company is eligible to receive								$ 400,000

Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 477,980	$ 248,931
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding - basic	107,648	105,572
Effect of dilutive securities (in shares):
Stock options	7,244	9,050
Restricted stock	14	484
Dilutive potential shares	7,258	9,534
Weighted average shares - diluted (in shares)	114,906	115,106
Earnings Per Share, Basic and Diluted [Abstract]
Net income per share - basic	$ 4.44	$ 2.36
Net income per share - diluted (in dollars per share)	$ 4.16	$ 2.16
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	14,878	11,535
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares	57	18

Marketable Securities (Details) - USD ($)	3 Months Ended
Marketable Securities (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Document Period End Date	Mar. 31, 2018
Marketable Securities, Realized Gain (Loss)	$ 0	$ 0
Unrealized Gain on Securities	9,400,000	$ 5,400,000
Amortized Cost Basis	2,376,174,000		$ 2,027,272,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,978,000		2,210,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(19,781,000)		(8,926,000)
Available-for-sale Securities	2,358,371,000		2,020,556,000
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Maturities within one year	605,461,000		593,783,000
Maturities after one year through five years	1,752,910,000		1,426,773,000
Total	2,358,371,000		2,020,556,000
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	1,417,229,000		1,044,084,000
Fair Value - 12 Months or Greater	311,051,000		326,676,000
Fair Value - Total	1,728,280,000		1,370,760,000
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(14,584,000)		(5,343,000)
Unrealized Loss - 12 Months or Greater	(5,197,000)		(3,583,000)
Unrealized Loss - Total	(19,781,000)		(8,926,000)
Corporate Bond Securities [Member]
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	1,343,778,000		930,970,000
Fair Value - 12 Months or Greater	234,258,000		256,750,000
Fair Value - Total	1,578,036,000		1,187,720,000
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(13,950,000)		(4,924,000)
Unrealized Loss - 12 Months or Greater	(4,209,000)		(2,748,000)
Unrealized Loss - Total	(18,159,000)		(7,672,000)
U.S. government and government agency obligations
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	70,872,000		110,532,000
Fair Value - 12 Months or Greater	76,793,000		67,921,000
Fair Value - Total	147,665,000		178,453,000
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(623,000)		(409,000)
Unrealized Loss - 12 Months or Greater	(988,000)		(832,000)
Unrealized Loss - Total	(1,611,000)		(1,241,000)
Municipal bonds
Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value - Less than 12 Months	2,579,000		2,582,000
Fair Value - 12 Months or Greater	0		2,005,000
Fair Value - Total	2,579,000		4,587,000
Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Unrealized Loss - Less than 12 months	(11,000)		(10,000)
Unrealized Loss - 12 Months or Greater	0		(3,000)
Unrealized Loss - Total	(11,000)		(13,000)
Unrestricted [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	2,126,820,000		1,717,976,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,948,000		2,176,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(18,159,000)		(7,672,000)
Available-for-sale Securities	2,110,609,000		1,712,480,000
Unrestricted [Member] \| U.S. government and government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	156,281,000		186,699,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	30,000		34,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,611,000)		(1,241,000)
Available-for-sale Securities	154,700,000		185,492,000
Unrestricted [Member] \| Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	2,591,000		4,600,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(11,000)		(13,000)
Available-for-sale Securities	2,580,000		4,587,000
Unrestricted [Member] \| Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	70,385,000		106,973,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0		0
Available-for-sale Securities	70,385,000		106,973,000
Unrestricted [Member] \| Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	20,097,000		11,024,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0		0
Available-for-sale Securities	$ 20,097,000		$ 11,024,000

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0
Proceeds from Sale and Maturity of Marketable Securities	$ 255,276	119,012
Document Period End Date	Mar. 31, 2018
Payments to Acquire Marketable Securities	$ 601,313	208,694
Marketable securities:
Securities Owned Not Readily Marketable	37,500
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other than Temporary Impairment Losses, Investments	0	$ 0
Measured on a recurring basis \| Fair Value, Inputs, Level 1 [Member]
Marketable securities:
Marketable Securities	69,075		$ 62,785
Measured on a recurring basis \| Fair Value, Inputs, Level 2 [Member]
Marketable securities:
Marketable Securities	2,358,371		2,020,556
Measured on a recurring basis \| Unrestricted [Member] \| Fair Value, Inputs, Level 1 [Member]
Marketable securities:
Corporate bonds	0		0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0		0
Municipal bonds	0		0
Commercial Paper	0		0
Certificates of Deposit, at Carrying Value	0		0
Marketable Securities, Equity Securities	69,075		62,785
Measured on a recurring basis \| Unrestricted [Member] \| Fair Value, Inputs, Level 2 [Member]
Marketable securities:
Corporate bonds	2,110,609		1,712,480
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	154,700		185,492
Municipal bonds	2,580		4,587
Commercial Paper	70,385		106,973
Certificates of Deposit, at Carrying Value	20,097		11,024
Marketable Securities, Equity Securities	0		0
Estimate of Fair Value Measurement [Member] \| Measured on a recurring basis
Marketable securities:
Marketable Securities	2,427,446		2,083,341
Estimate of Fair Value Measurement [Member] \| Measured on a recurring basis \| Unrestricted [Member]
Marketable securities:
Corporate bonds	2,110,609		1,712,480
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	154,700		185,492
Municipal bonds	2,580		4,587
Commercial Paper	70,385		106,973
Certificates of Deposit, at Carrying Value	20,097		11,024
Marketable Securities, Equity Securities	$ 69,075		$ 62,785

Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 201,429	$ 190,045
Work in process	374,505	302,042
Finished goods	22,848	21,791
Deferred costs	221,615	212,260
Total Inventories	$ 820,397	$ 726,138

Derivative Instruments (Details) - USD ($)	3 Months Ended
Derivative Instruments (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness	$ 0
Interest Rate Swap Contracts
Derivative [Line Items]
Derivative, Notional Amount	75,000,000	$ 75,000,000
Interest Rate Cap Contracts
Derivative [Line Items]
Derivative, Notional Amount	$ 75,000,000	$ 75,000,000

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Operating Loss Carryforwards [Line Items]
Total income tax expense (benefit)	$ 107,418		$ 183,358
Effective income tax rate	18.30%		42.40%
Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss)			$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Provisional charge for re-measurement of U.S. deferred tax assets due to US Tax Reform		$ 326,200

Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
Statement of Cash Flows (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 1,019,491	$ 811,773	$ 812,733
Restricted Cash	12,500	12,500
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,031,991	824,273	825,233	$ 547,703
Accrued capital expenditures	40,200	32,300	$ 41,800	$ 28,200
Capital Lease Obligations Incurred	$ 0	$ 201,200

Legal Matters (Details)	3 Months Ended
Legal Matters (Details)	Mar. 31, 2018 EUR (€)
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, per unit produced.	€ 10,000
Loss Contingency, Damages Sought, Value	€ 10,000,000