0001532176-19-000034 | 10-Q | XBRL Viewer | Regeneron Pharmaceuticals INC

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Collaboration Agreements - Schedule of Significant Changes in Deferred Revenue Balances, Antibody Collaboration (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Increase due to shipments of commercial supplies to Sanofi	$ 375.8	$ (29.5)
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Increase due to shipments of commercial supplies to Sanofi	294.3
Revenue recognized that was included in deferred revenue at the beginning of the period	$ (159.0)

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 1,384.8	$ 1,467.7
Marketable securities	1,493.1	1,342.2
Accounts receivable - trade, net	2,027.7	1,723.7
Accounts receivable from Sanofi	345.4	226.4
Accounts receivable from Bayer	286.9	293.1
Inventories	1,344.3	1,151.2
Prepaid expenses and other current assets	226.9	243.3
Total current assets	7,109.1	6,447.6
Marketable securities	3,112.6	1,755.0
Property, plant, and equipment, net	2,771.4	2,575.8
Deferred tax assets	808.3	828.7
Other noncurrent assets	137.9	127.4
Total assets	13,939.3	11,734.5
Current liabilities:
Accounts payable	335.6	218.2
Accrued expenses and other current liabilities	821.1	772.1
Total current liabilities	1,765.4	1,442.8
Finance lease liabilities	712.7
Finance lease liabilities		708.5
Other noncurrent liabilities	273.0	361.7
Total liabilities	3,434.9	2,977.2
Stockholders' equity:
Preferred Stock, $.01 par value; 30,000,000 shares authorized; issued and outstanding - none	0.0	0.0
Additional paid-in capital	4,388.4	3,911.6
Retained earnings	6,587.8	5,254.3
Accumulated other comprehensive income (loss)	16.5	(12.3)
Treasury Stock, at cost; 4,167,018 shares in 2019 and 3,990,021 shares in 2018	(488.4)	(396.4)
Total stockholders' equity	10,504.4	8,757.3
Total liabilities and stockholders' equity	13,939.3	11,734.5
Class A Stock
Stockholders' equity:
Common stock	0.0	0.0
Total stockholders' equity	0.0	0.0
Common Stock
Stockholders' equity:
Common stock	0.1	0.1
Total stockholders' equity	0.1	0.1
Sanofi
Current liabilities:
Deferred revenue, current	427.1	246.7
Deferred revenue, noncurrent	551.9	279.3
Other
Current liabilities:
Deferred revenue, current	181.6	205.8
Deferred revenue, noncurrent	$ 131.9	$ 184.9

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Class A Stock	Common Stock
Beginning Balance (in shares) at Dec. 31, 2017					(3.8)	1.9	109.5
Beginning Balance at Dec. 31, 2017	$ 6,144.1	$ 3,512.9	$ 2,946.7	$ 0.6	$ (316.2)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.1
Issuance of Common Stock in connection with exercise of stock options	13.6	13.6
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan (in shares)							0.1
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan	(0.7)	(0.7)
Stock-based compensation charges	85.8	85.8
Net income	477.9		477.9
Other comprehensive gain (loss), net of tax	(9.7)			(9.7)
Ending Balance (in shares) at Mar. 31, 2018					(3.8)	1.9	109.7
Ending Balance at Mar. 31, 2018	6,567.5	3,611.6	3,287.7	(15.7)	$ (316.2)	$ 0.0	$ 0.1
Beginning Balance (in shares) at Dec. 31, 2017					(3.8)	1.9	109.5
Beginning Balance at Dec. 31, 2017	6,144.1	3,512.9	2,946.7	0.6	$ (316.2)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,624.0
Ending Balance (in shares) at Sep. 30, 2018					(4.0)	1.9	110.3
Ending Balance at Sep. 30, 2018	7,868.2	3,841.2	4,433.8	(10.5)	$ (396.4)	$ 0.0	$ 0.1
Beginning Balance (in shares) at Mar. 31, 2018					(3.8)	1.9	109.7
Beginning Balance at Mar. 31, 2018	6,567.5	3,611.6	3,287.7	(15.7)	$ (316.2)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.4
Issuance of Common Stock in connection with exercise of stock options	19.8	19.8
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)							(0.2)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(31.9)	(31.9)
Repurchases of Common Stock from Sanofi (in shares)					(0.1)
Repurchases of Common Stock from Sanofi	(37.6)				$ (37.6)
Stock-based compensation charges	113.1	113.1
Net income	551.4		551.4
Other comprehensive gain (loss), net of tax	4.1			4.1
Ending Balance (in shares) at Jun. 30, 2018					(3.9)	1.9	109.9
Ending Balance at Jun. 30, 2018	7,186.4	3,712.6	3,839.1	(11.6)	$ (353.8)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.4
Issuance of Common Stock in connection with exercise of stock options	57.3	57.3
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(45.2)	(45.2)
Repurchases of Common Stock from Sanofi (in shares)					(0.1)
Repurchases of Common Stock from Sanofi	(42.6)				$ (42.6)
Stock-based compensation charges	116.5	116.5
Net income	594.7		594.7
Other comprehensive gain (loss), net of tax	1.1			1.1
Ending Balance (in shares) at Sep. 30, 2018					(4.0)	1.9	110.3
Ending Balance at Sep. 30, 2018	7,868.2	3,841.2	4,433.8	(10.5)	$ (396.4)	$ 0.0	$ 0.1
Beginning Balance (in shares) at Dec. 31, 2018					(4.0)	1.9	111.1
Beginning Balance at Dec. 31, 2018	8,757.3	3,911.6	5,254.3	(12.3)	$ (396.4)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.6
Issuance of Common Stock in connection with exercise of stock options	140.9	140.9
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(10.7)	(10.7)
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan (in shares)					0.1
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan	10.5	4.3			$ 6.2
Repurchases of Common Stock from Sanofi (in shares)					(0.1)
Repurchases of Common Stock from Sanofi	(54.0)				$ (54.0)
Stock-based compensation charges	114.8	114.8
Net income	461.1		461.1
Other comprehensive gain (loss), net of tax	15.1			15.1
Ending Balance (in shares) at Mar. 31, 2019					(4.0)	1.9	111.7
Ending Balance at Mar. 31, 2019	9,444.7	4,160.9	5,725.1	2.8	$ (444.2)	$ 0.0	$ 0.1
Beginning Balance (in shares) at Dec. 31, 2018					(4.0)	1.9	111.1
Beginning Balance at Dec. 31, 2018	8,757.3	3,911.6	5,254.3	(12.3)	$ (396.4)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,323.8
Ending Balance (in shares) at Sep. 30, 2019					(4.2)	1.8	112.1
Ending Balance at Sep. 30, 2019	10,504.4	4,388.4	6,587.8	16.5	$ (488.4)	$ 0.0	$ 0.1
Beginning Balance (in shares) at Mar. 31, 2019					(4.0)	1.9	111.7
Beginning Balance at Mar. 31, 2019	9,444.7	4,160.9	5,725.1	2.8	$ (444.2)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.3
Issuance of Common Stock in connection with exercise of stock options	13.9	13.9
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)							(0.1)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(29.7)	(29.7)
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan	11.7	9.3			$ 2.4
Stock-based compensation charges	109.2	109.2
Net income	193.1		193.1
Other comprehensive gain (loss), net of tax	13.0			13.0
Ending Balance (in shares) at Jun. 30, 2019					(4.0)	1.9	111.9
Ending Balance at Jun. 30, 2019	9,755.9	4,263.6	5,918.2	15.8	$ (441.8)	$ 0.0	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options (in shares)							0.1
Issuance of Common Stock in connection with exercise of stock options	8.3	8.3
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(0.1)	(0.1)
Issuance/distribution of Common Stock in connection with 401(k) Savings Plan	6.0	3.9			$ 2.1
Repurchases of Common Stock from Sanofi (in shares)					(0.2)
Repurchases of Common Stock from Sanofi	(48.7)				$ (48.7)
Conversion of Class A Stock to Common Stock (in shares)						0.1	0.1
Stock-based compensation charges	112.7	112.7
Net income	669.6		669.6
Other comprehensive gain (loss), net of tax	0.7			0.7
Ending Balance (in shares) at Sep. 30, 2019					(4.2)	1.8	112.1
Ending Balance at Sep. 30, 2019	$ 10,504.4	$ 4,388.4	$ 6,587.8	$ 16.5	$ (488.4)	$ 0.0	$ 0.1

Marketable Securities - Narrative (Details)	3 Months Ended
Marketable Securities - Narrative (Details)	Sep. 30, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract]
Realized gain (loss) on sales of marketable securities	$ 0

Product Sales

9 Months Ended

Sep. 30, 2019

Revenues [Abstract]

Product Sales

Net product sales consist of the following:



	Three Months Ended September 30,				Nine Months Ended September 30,
Net Product Sales in the United States	2019		2018		2019		2018
EYLEA^®	$	1,187.7	$	1,021.8	$	3,422.1	$	2,997.8
Libtayo^®	47.6		—		115.2		—
ARCALYST^®	3.0		3.7		10.7		12.0
	$	1,238.3	$	1,025.5	$	3,548.0	$	3,009.8

The Company had product sales to certain customers that accounted for more than 10% of total gross product revenue for each of the three and nine months ended September 30, 2019 and 2018. Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Besse Medical, a subsidiary of AmerisourceBergen Corporation	57	%	57	%	57	%	56	%
McKesson Corporation	34	%	36	%	33	%	37	%

The following table summarizes the provisions, and credits/payments, for sales-related deductions during the nine months ended September 30, 2019 and 2018.



	Rebates, Chargebacks, and Discounts			Distribution-Related Fees			Other Sales-Related Deductions			Total
Balance as of December 31, 2018	$	41.1		$	42.0		$	8.3		$	91.4
Provisions	301.0			177.3			46.0			524.3
Credits/payments	(265.8		)	(172.5		)	(40.7		)	(479.0		)
Balance as of September 30, 2019	$	76.3		$	46.8		$	13.6		$	136.7

Balance as of December 31, 2017	$	29.9		$	34.1		$	21.3		$	85.3
Provisions	159.1			155.5			29.7			344.3
Credits/payments	(145.9		)	(150.9		)	(35.7		)	(332.5		)
Balance as of September 30, 2018	$	43.1		$	38.7		$	15.3		$	97.1

Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 4,148.9	$ 3,026.6
Unrealized Gains	27.8	1.0
Unrealized Losses	(0.7)	(18.4)
Available-for-sale debt securities:	4,176.0	3,009.2
Corporate bonds \| Unrestricted
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	3,880.6	2,734.8
Unrealized Gains	27.0	1.0
Unrealized Losses	(0.6)	(17.4)
Available-for-sale debt securities:	3,907.0	2,718.4
U.S. government and government agency obligations \| Unrestricted
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	65.9	110.4
Unrealized Gains	0.2	0.0
Unrealized Losses	(0.1)	(1.0)
Available-for-sale debt securities:	66.0	109.4
Sovereign bonds \| Unrestricted
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	26.9	7.6
Unrealized Gains	0.5	0.0
Unrealized Losses	0.0	0.0
Available-for-sale debt securities:	27.4	7.6
Commercial paper \| Unrestricted
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	108.8	113.8
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Available-for-sale debt securities:	108.8	113.8
Certificates of deposit \| Unrestricted
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	66.7	60.0
Unrealized Gains	0.1	0.0
Unrealized Losses	0.0	0.0
Available-for-sale debt securities:	$ 66.8	$ 60.0

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state, and foreign income taxes. The Company's effective tax rate was 12.9% and 6.5% for the three months ended September 30, 2019 and 2018, respectively, and 14.0% and 13.5% for the nine months ended September 30, 2019 and 2018, respectively. The Company's effective tax rate for the three and nine months ended September 30, 2019 was positively impacted, compared to the U.S. federal statutory rate, primarily by federal tax credits for research activities, the foreign-derived intangible income deduction, and income earned in foreign jurisdictions with tax rates lower than the U.S. federal statutory rate, partly offset by the taxation of certain global intangible low-taxed income and the non-deductible Branded Prescription Drug Fee. The Company's effective tax rate for the three and nine months ended September 30, 2018 was positively impacted, compared to the U.S. federal statutory rate, primarily by the tax benefit associated with tax planning in connection with the "Tax Cuts and Jobs Act," the federal tax credit for research activities, and, to a lesser extent, stock-based compensation and income earned in foreign jurisdictions with tax rates lower than the U.S. federal statutory rate.

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

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 September 30, 2019	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	$	3,907.0	—		$	3,907.0
U.S. government and government agency obligations	66.0		—		66.0
Sovereign bonds	27.4		—		27.4
Commercial paper	108.8		—		108.8
Certificates of deposit	66.8		—		66.8
Equity securities (unrestricted)	46.9		$	46.9	—
Equity securities (restricted)	382.8		49.3		333.5
	$	4,605.7	$	96.2	$	4,509.5

As of December 31, 2018
Available-for-sale debt securities:
Corporate bonds	$	2,718.4	—		$	2,718.4
U.S. government and government agency obligations	109.4		—		109.4
Sovereign bonds	7.6		—		7.6
Commercial paper	113.8		—		113.8
Certificates of deposit	60.0		—		60.0
Equity securities (unrestricted)	43.6		$	43.6	—
Equity securities (restricted)	44.4		—		44.4
	$	3,097.2	$	43.6	$	3,053.6

Collaboration Agreements - Alnylam Narrative (Details) - USD ($)		1 Months Ended	3 Months Ended
	Aug. 31, 2019	Apr. 30, 2019	Jun. 30, 2019
Alnylam
Research Collaboration and Licensing Arrangements [Line Items]
Upfront payment made			$ 400,000,000.0
Additional payment eligible to be made		$ 200,000,000.0
Initial research term		5 years
Potential extension of research term		5 years
Maximum amount of sales milestone payments if total sales achieve specific levels	$ 325,000,000.0
Alnylam Stock Purchase Agreement
Research Collaboration and Licensing Arrangements [Line Items]
Cash consideration		$ 400,000,000.0
Minimum \| Alnylam
Research Collaboration and Licensing Arrangements [Line Items]
Extension of research term fee		$ 200,000,000.0
Maximum \| Alnylam
Research Collaboration and Licensing Arrangements [Line Items]
Initial research term		7 years
Extension of research term fee		$ 400,000,000.0

Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Available-for-sale Debt Securities

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



	Amortized		Unrealized					Fair
As of September 30, 2019	Cost Basis		Gains		Losses			Value
Corporate bonds	$	3,880.6	$	27.0	$	(0.6	)	$	3,907.0
U.S. government and government agency obligations	65.9		0.2		(0.1		)	66.0
Sovereign bonds	26.9		0.5		—			27.4
Commercial paper	108.8		—		—			108.8
Certificates of deposit	66.7		0.1		—			66.8
	$	4,148.9	$	27.8	$	(0.7	)	$	4,176.0

As of December 31, 2018
Corporate bonds	$	2,734.8	$	1.0	$	(17.4	)	$	2,718.4
U.S. government and government agency obligations	110.4		—		(1.0		)	109.4
Sovereign bonds	7.6		—		—			7.6
Commercial paper	113.8		—		—			113.8
Certificates of deposit	60.0		—		—			60.0
	$	3,026.6	$	1.0	$	(18.4	)	$	3,009.2

Marketable Securities, Based on Contractual Maturity Dates

The fair values of available-for-sale debt security investments by contractual maturity consist of the following:



	September 30,		December 31,
	2019		2018
Maturities within one year	$	1,493.1	$	1,342.2
Maturities after one year through five years	2,682.9		1,667.0
	$	4,176.0	$	3,009.2

Fair Value and Unrealized Losses of Marketable Securities

The following table shows the fair value of the Company's available-for-sale 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 September 30, 2019	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	294.8	$	(0.3	)	$	216.3	$	(0.3	)	$	511.1	$	(0.6	)
U.S. government and government agency obligations	18.5		(0.1		)	19.5		—			38.0		(0.1		)
	$	313.3	$	(0.4	)	$	235.8	$	(0.3	)	$	549.1	$	(0.7	)

As of December 31, 2018
Corporate bonds	$	1,482.6	$	(6.1	)	$	801.6	$	(11.3	)	$	2,284.2	$	(17.4	)
U.S. government and government agency obligations	—		—			99.1		(1.0		)	99.1		(1.0		)
	$	1,482.6	$	(6.1	)	$	900.7	$	(12.3	)	$	2,383.3	$	(18.4	)

Marketable Securities - Schedule of Debt Securities Based on Contractual Maturity Dates (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Maturities within one year	$ 1,493.1	$ 1,342.2
Maturities after one year through five years	2,682.9	1,667.0
Total	$ 4,176.0	$ 3,009.2

Inventories - Schedule of Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 229.0	$ 226.8
Work-in-process	633.5	571.1
Finished goods	49.4	24.4
Deferred costs	432.4	328.9
Total Inventories	$ 1,344.3	$ 1,151.2

Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2017
Leases [Abstract]
Finance lease, term of contract		5 years
Finance lease, extension option		5 years
Property, plant, and equipment, at cost	$ 723.9
Accumulated amortization	$ 61.7

Net Income Per Share - Schedule of Antidilutive Securities Excluded From Computation (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares (in shares)	18.3	14.4	18.2	14.8
Restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares (in shares)	0.4	0.0	0.4	0.1

Statement of Cash Flows - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 1,384.8	$ 1,467.7	$ 1,087.8
Restricted cash included in Other noncurrent assets	12.5		12.5
Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows	$ 1,397.3	$ 1,480.2	$ 1,100.3	$ 825.2

Recently Issued Accounting Standards	9 Months Ended
Recently Issued Accounting Standards	Sep. 30, 2019
Accounting Policies [Abstract]
Recently Issued Accounting Standards	Recently Issued Accounting Standards In June 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires an entity to measure and recognize expected credit losses for certain financial instruments, including trade receivables, as an allowance that reflects the entity's current estimate of credit losses expected to be incurred. For available-for-sale debt securities with unrealized losses, the standard requires allowances to be recorded through net income instead of directly reducing the amortized cost of the investment under the current other-than-temporary impairment model. The standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We do not expect the adoption of this standard to have a significant impact on our financial statements or internal controls; however, the ultimate impact will depend on the composition of the Company's portfolio of financial instruments as of the adoption date.

Label	Element	Value
Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 9,700,000
Accounting Standards Update 2016-02 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	9,700,000
Accounting Standards Update 2016-01 [Member] \| AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(6,600,000)
Accounting Standards Update 2014-09 And 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(143,500,000)
Accounting Standards Update 2014-09 And 2016-01 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (136,900,000)

Net Income Per Share - Narrative (Details) - Subsequent Event	Nov. 05, 2019 USD ($) shares
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized amount \| $	$ 1,000,000,000.0
Number of shares repurchased to date (in shares) \| shares	0

Inventories

9 Months Ended

Sep. 30, 2019

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	September 30,		December 31,
	2019		2018
Raw materials	$	229.0	$	226.8
Work-in-process	633.5		571.1
Finished goods	49.4		24.4
Deferred costs	432.4		328.9
	$	1,344.3	$	1,151.2

Deferred costs represent the costs of product manufactured and shipped to the Company's collaborators for which recognition of revenue has been deferred. In these instances, the Company is reimbursed for its manufacturing costs as product is shipped to its collaborators; however, recognition of such cost reimbursements as revenue is deferred until the product is sold by the Company's collaborators to third-party customers.

Collaboration Agreements (Tables)

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Schedule of collaboration revenue

Net product sales consist of the following:



	Three Months Ended September 30,				Nine Months Ended September 30,
Net Product Sales in the United States	2019		2018		2019		2018
EYLEA^®	$	1,187.7	$	1,021.8	$	3,422.1	$	2,997.8
Libtayo^®	47.6		—		115.2		—
ARCALYST^®	3.0		3.7		10.7		12.0
	$	1,238.3	$	1,025.5	$	3,548.0	$	3,009.8

Revenue earned in connection with our Bayer EYLEA collaboration is as follows (note that the table excludes amounts in connection with our Bayer Ang2 antibody and PDGFR-beta antibody collaboration agreements, which were previously terminated):



	Three Months Ended September 30,				Nine Months Ended September 30,
Bayer EYLEA Collaboration Revenue	2019		2018		2019		2018
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	275.0	$	243.2	$	793.3	$	721.5
Reimbursement of Regeneron EYLEA development expenses	5.0		1.7		15.6		8.8
Other	22.8		20.7		59.1		45.4
	$	302.8	$	265.6	$	868.0	$	775.7

The collaboration revenue we earned from Sanofi is detailed below:



	Three Months Ended September 30,						Nine Months Ended September 30,
Sanofi Collaboration Revenue	2019			2018			2019			2018
Antibody:
Reimbursement of Regeneron research and development expenses	$	60.2		$	76.2		$	216.5		$	201.0
Reimbursement of Regeneron commercialization-related expenses	111.6			103.7			349.3			292.8
Reimbursement for Regeneron's manufacturing of commercial supplies	78.5			40.3			133.3			94.4
Regeneron's share of profits (losses) in connection with commercialization of antibodies	94.2			(38.9		)	105.2			(182.6		)
Other	4.8			(7.2		)	(0.6		)	(12.3		)
Total Antibody	349.3			174.1			803.7			393.3
Immuno-oncology:
Reimbursement of Regeneron research and development expenses	38.0			74.8			120.9			225.7
Reimbursement of Regeneron commercialization-related expenses	3.0			3.2			7.0			6.5
Amounts recognized in connection with up-front payments received	18.5			7.9			73.8			65.2
Other	(4.6		)	(3.7		)	(5.7		)	(7.2		)
Total Immuno-oncology	54.9			82.2			196.0			290.2
	$	404.2		$	256.3		$	999.7		$	683.5

Schedule of accounts receivable and deferred revenue information

The following table summarizes contract balances in connection with the Company's Antibody Collaboration with Sanofi:



	September 30,		December 31,
	2019		2018
Accounts receivable	$	332.5	$	138.2
Deferred revenue	$	377.0	$	236.1

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Increase due to shipments of commercial supplies to Sanofi	$	294.3
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(159.0	)

The following table summarizes contract balances in connection with the Teva Collaboration Agreement:



	September 30,		December 31,
	2019		2018
Accounts receivable (recorded within Prepaid expenses and other current assets)	$	36.0	$	28.8
Deferred revenue	$	127.8	$	194.5

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(68.7	)

The following table summarizes contract balances in connection with the Company's IO Collaboration with Sanofi:



	September 30,		December 31,
	2019		2018
Accounts receivable	$	8.2	$	77.9
Deferred revenue	$	602.0	$	289.9

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Increase as a result of payment received from Sanofi in connection with the Amended IO Discovery Agreement	$	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(73.8	)
Revenue recognized that was added to deferred revenue during the period	$	(37.9	)

Leases

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Leases

We conduct certain of our research, development, and administrative activities at leased facilities. We also lease certain warehouses and vehicles. As described in Note 1, during the first quarter of 2019, we adopted ASC 842, Leases.

We determine if an arrangement is a lease considering whether there is an identified asset and the contract conveys the right to control its use. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Our lease terms may include options to extend or terminate a lease when it is reasonably certain that we will exercise that option. We account for lease components (e.g., rental payments) separately from non-lease components (e.g., common area maintenance costs).

Right-of-use assets and lease liabilities are recognized at lease commencement date based on the present value of lease payments over the lease term, unless there is a transfer of title or purchase option we are reasonably certain to exercise. For leases where an implicit rate is not readily determinable, we use our incremental borrowing rate based on information available at the lease commencement date to determine the present value of future lease payments. Lease expense for operating leases is recognized on a straight-line basis over the expected lease term.

Operating leases

Amounts recognized in our Condensed Consolidated Balance Sheets and Statements of Operations included in this report associated with operating leases were not material. Operating lease right-of-use assets are included within Other noncurrent assets, and lease liabilities are included in Accrued expenses and other current liabilities and Other noncurrent liabilities.

Finance leases

In March 2017, we entered into a Participation Agreement with BA Leasing BSC, LLC, an affiliate of Banc of America Leasing & Capital LLC ("BAL"), as lessor, and a syndicate of lenders (collectively, the "Participants"). In March 2017, we also entered into a Lease and Remedies Agreement with BAL, pursuant to which we have leased laboratory and office facilities in Tarrytown, New York (the "Facility") for a five-year term. The Participation Agreement, the Lease and Remedies Agreement, and certain other related agreements were amended and restated in May 2019, among other things, to revise certain covenants, representations and warranties, and events of default to be substantially similar to those set forth in the agreement governing the Company's revolving credit facility (as so amended and restated, the "Participation Agreement" and the "Lease," respectively). The Lease requires us to pay all maintenance, insurance, taxes, and other costs arising out of the use of the Facility. We are also required to make monthly payments of basic rent during the term of the Lease in an amount equal to a variable rate per annum based on the one-month LIBOR, plus an applicable margin that varies with our debt rating and total leverage ratio. The Participation Agreement and the Lease include an option for us to elect to extend the maturity date of the Participation Agreement and the term of the Lease for an additional five-year period, subject to the consent of all the Participants and certain other conditions. We also have the option prior to the end of the term of the Lease to (a) purchase the Facility by paying an amount equal to the outstanding principal amount of the Participants' advances under the Participation Agreement, all accrued and unpaid interest and yield thereon, and all other outstanding amounts under the Participation Agreement, the Lease, and certain related documents or (b) sell the Facility to a third

party on behalf of BAL. The advances under the Participation Agreement mature, and all amounts outstanding thereunder will become due and payable in full, at the end of the term of the Lease.

Prior to January 1, 2019, for certain of the premises under the Lease we were deemed, in substance, to be the owner of the buildings (collectively, the "Build-to-Suit Buildings"). Upon the adoption of ASC 842, the classification of the Build-to-Suit Buildings, for which the construction period had been completed, was reassessed and, consequently, they were derecognized and recognized as a finance lease. These premises, along with the other premises under the Lease, are classified as a finance lease as we have the option to purchase the Facility under terms that make it reasonably certain to be exercised.

The agreements governing the Lease financing contain financial and operating covenants. The Company was in compliance with all such covenants as of September 30, 2019.

Amounts recognized in the Condensed Consolidated Balance Sheet related to the Lease are included in the table below. Other than the Lease described above, we had no leases accounted for as finance leases as of September 30, 2019.



		September 30,
	Classification	2019
Finance lease right-of-use assets	Property, plant, and equipment, net ⁽¹⁾	$	663.7
Finance lease liabilities	Finance lease liabilities (noncurrent)	$	712.7

⁽¹⁾ Finance lease right-of-use assets are recorded net of accumulated amortization of $72.5 million as of September 30, 2019.

As of December 31, 2018, property, plant, and equipment, at cost, included $723.9 million of leased property under the Lease. Accumulated amortization related to these assets amounted to $61.7 million as of December 31, 2018.

Finance lease costs consist of the following:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Amortization of right-of-use assets	$	3.6	$	10.8
Interest on lease liabilities	6.9		21.4
	$	10.5	$	32.2

Other information related to our finance lease includes the following:



	September 30,
	2019
Remaining lease term (in years)	2.42
Discount rate	2.89	%

Supplemental information

The following is an analysis of lease liability maturities as of September 30, 2019:



	Operating Leases			Finance Leases
2019	$	1.9		$	5.7
2020	8.0			21.2
2021	6.6			20.1
2022	3.3			725.0
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	28.4			772.0
Imputed interest	(3.1		)	(53.2		)
Debt financing costs	—			(6.1		)
Total lease liabilities	$	25.3		$	712.7

As of December 31, 2018, the estimated future minimum noncancelable lease commitments, excluding the purchase price we would be obligated to pay if we were to exercise our option to purchase the Facility, were as follows:



	Operating Leases		Capital and Facility Lease Obligations
2019	$	10.4	$	26.4
2020	3.8		28.4
2021	3.4		27.9
2022	2.2		7.0
2023	1.5		—
Thereafter	4.1		—
	$	25.4	$	89.7

Leases

Operating leases

Finance leases

party on behalf of BAL. The advances under the Participation Agreement mature, and all amounts outstanding thereunder will become due and payable in full, at the end of the term of the Lease.

The agreements governing the Lease financing contain financial and operating covenants. The Company was in compliance with all such covenants as of September 30, 2019.



		September 30,
	Classification	2019
Finance lease right-of-use assets	Property, plant, and equipment, net ⁽¹⁾	$	663.7
Finance lease liabilities	Finance lease liabilities (noncurrent)	$	712.7

⁽¹⁾ Finance lease right-of-use assets are recorded net of accumulated amortization of $72.5 million as of September 30, 2019.

Finance lease costs consist of the following:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Amortization of right-of-use assets	$	3.6	$	10.8
Interest on lease liabilities	6.9		21.4
	$	10.5	$	32.2

Other information related to our finance lease includes the following:



	September 30,
	2019
Remaining lease term (in years)	2.42
Discount rate	2.89	%

Supplemental information

The following is an analysis of lease liability maturities as of September 30, 2019:



	Operating Leases			Finance Leases
2019	$	1.9		$	5.7
2020	8.0			21.2
2021	6.6			20.1
2022	3.3			725.0
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	28.4			772.0
Imputed interest	(3.1		)	(53.2		)
Debt financing costs	—			(6.1		)
Total lease liabilities	$	25.3		$	712.7



	Operating Leases		Capital and Facility Lease Obligations
2019	$	10.4	$	26.4
2020	3.8		28.4
2021	3.4		27.9
2022	2.2		7.0
2023	1.5		—
Thereafter	4.1		—
	$	25.4	$	89.7

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Net unrealized gain (loss) on securities	$ 15.7	$ (4.9)	$ (58.4)	$ 21.0
Securities owned not readily marketable	$ 43.1		$ 43.1		$ 45.5

Collaboration Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 2,048.4	$ 1,663.5	$ 5,693.9	$ 4,783.0
Bayer \| Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	302.8	264.4	868.0	775.2
Outside United States \| Bayer \| Product and service, other
Disaggregation of Revenue [Line Items]
Revenues	302.8	265.6	868.0	775.7
Outside United States \| Bayer \| Regeneron's net profit in connection with commercialization of EYLEA outside the United States
Disaggregation of Revenue [Line Items]
Revenues	275.0	243.2	793.3	721.5
Outside United States \| Bayer \| Reimbursement of Regeneron EYLEA development expenses
Disaggregation of Revenue [Line Items]
Revenues	5.0	1.7	15.6	8.8
Outside United States \| Bayer \| Other
Disaggregation of Revenue [Line Items]
Revenues	$ 22.8	$ 20.7	$ 59.1	$ 45.4

Collaboration Agreements - Schedule of Contract Balances, Antibody Collaboration (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 345.4	$ 226.4
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Accounts receivable	332.5	138.2
Deferred revenue	$ 377.0	$ 236.1

Collaboration Agreements - Teva Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues	$ 2,048.4	$ 1,663.5	$ 5,693.9	$ 4,783.0
Teva
Disaggregation of Revenue [Line Items]
Up-front payment received					$ 250.0
Revenues	57.4	$ 69.1	172.2	$ 196.6
Revenue, performance obligation amount	$ 300.6		$ 300.6

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2019	Oct. 24, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	0-19034
Entity Registrant Name	REGENERON PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	NY
Entity Tax Identification Number	13-3444607
Entity Address, Address Line One	777 Old Saw Mill River Road
Entity Address, City or Town	Tarrytown,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10591-6707
City Area Code	914
Local Phone Number	847-7000
Title of 12(b) Security	Common Stock - par value $.001 per share
Trading Symbol	REGN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000872589
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		107,946,794
Class A Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		1,848,970

Product Sales - Schedule of Sales Related Deductions Activity (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 91.4	$ 85.3
Provisions	524.3	344.3
Credits/payments	(479.0)	(332.5)
Ending Balance	136.7	97.1
Rebates, Chargebacks, and Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	41.1	29.9
Provisions	301.0	159.1
Credits/payments	(265.8)	(145.9)
Ending Balance	76.3	43.1
Distribution-Related Fees
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	42.0	34.1
Provisions	177.3	155.5
Credits/payments	(172.5)	(150.9)
Ending Balance	46.8	38.7
Other Sales-Related Deductions
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	8.3	21.3
Provisions	46.0	29.7
Credits/payments	(40.7)	(35.7)
Ending Balance	$ 13.6	$ 15.3

Product Sales (Tables)

9 Months Ended

Sep. 30, 2019

Revenues [Abstract]

Schedule of product sales

Net product sales consist of the following:



	Three Months Ended September 30,				Nine Months Ended September 30,
Net Product Sales in the United States	2019		2018		2019		2018
EYLEA^®	$	1,187.7	$	1,021.8	$	3,422.1	$	2,997.8
Libtayo^®	47.6		—		115.2		—
ARCALYST^®	3.0		3.7		10.7		12.0
	$	1,238.3	$	1,025.5	$	3,548.0	$	3,009.8



	Three Months Ended September 30,				Nine Months Ended September 30,
Bayer EYLEA Collaboration Revenue	2019		2018		2019		2018
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	275.0	$	243.2	$	793.3	$	721.5
Reimbursement of Regeneron EYLEA development expenses	5.0		1.7		15.6		8.8
Other	22.8		20.7		59.1		45.4
	$	302.8	$	265.6	$	868.0	$	775.7

The collaboration revenue we earned from Sanofi is detailed below:



	Three Months Ended September 30,						Nine Months Ended September 30,
Sanofi Collaboration Revenue	2019			2018			2019			2018
Antibody:
Reimbursement of Regeneron research and development expenses	$	60.2		$	76.2		$	216.5		$	201.0
Reimbursement of Regeneron commercialization-related expenses	111.6			103.7			349.3			292.8
Reimbursement for Regeneron's manufacturing of commercial supplies	78.5			40.3			133.3			94.4
Regeneron's share of profits (losses) in connection with commercialization of antibodies	94.2			(38.9		)	105.2			(182.6		)
Other	4.8			(7.2		)	(0.6		)	(12.3		)
Total Antibody	349.3			174.1			803.7			393.3
Immuno-oncology:
Reimbursement of Regeneron research and development expenses	38.0			74.8			120.9			225.7
Reimbursement of Regeneron commercialization-related expenses	3.0			3.2			7.0			6.5
Amounts recognized in connection with up-front payments received	18.5			7.9			73.8			65.2
Other	(4.6		)	(3.7		)	(5.7		)	(7.2		)
Total Immuno-oncology	54.9			82.2			196.0			290.2
	$	404.2		$	256.3		$	999.7		$	683.5

Schedules of Concentration of Risk, by Risk Factor



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Besse Medical, a subsidiary of AmerisourceBergen Corporation	57	%	57	%	57	%	56	%
McKesson Corporation	34	%	36	%	33	%	37	%

Sales Related Deductions Activity

The following table summarizes the provisions, and credits/payments, for sales-related deductions during the nine months ended September 30, 2019 and 2018.



	Rebates, Chargebacks, and Discounts			Distribution-Related Fees			Other Sales-Related Deductions			Total
Balance as of December 31, 2018	$	41.1		$	42.0		$	8.3		$	91.4
Provisions	301.0			177.3			46.0			524.3
Credits/payments	(265.8		)	(172.5		)	(40.7		)	(479.0		)
Balance as of September 30, 2019	$	76.3		$	46.8		$	13.6		$	136.7

Balance as of December 31, 2017	$	29.9		$	34.1		$	21.3		$	85.3
Provisions	159.1			155.5			29.7			344.3
Credits/payments	(145.9		)	(150.9		)	(35.7		)	(332.5		)
Balance as of September 30, 2018	$	43.1		$	38.7		$	15.3		$	97.1

CONDENSED CONSOLIDATED BALANCE SHEET (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
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, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Treasury stock, outstanding (in shares)	4,167,018	3,990,021
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)	1,848,970	1,911,354
Common Stock, shares outstanding (in shares)	1,848,970	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)	112,039,746	111,084,951

Interim Financial Statements	9 Months Ended
Interim Financial Statements	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Interim Financial Statements	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 condensed consolidated financial statements 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, 2018 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, 2018. Certain reclassifications have been made to prior period amounts to conform with the current period's presentation. We adopted Accounting Standards Codification ("ASC") 842, Leases, on January 1, 2019 (the "effective date") and used the effective date as our date of initial application. See Note 8. The new standard requires a lessee to recognize on its balance sheet (for both finance and operating leases) a liability for future lease payments and a right-of-use asset representing its right to use the underlying asset over the lease term. We elected the practical expedients upon transition, which permitted companies to not reassess lease identification, classification, and initial direct costs under the new standard for leases that commenced prior to the effective date. Upon adoption of the new standard, we recognized right-of-use assets of $33.2 million related to operating leases as of January 1, 2019. The impact of adopting the standard for the facilities that we had historically applied build-to-suit and capital lease accounting was not material to our Condensed Consolidated Financial Statements. Prior period amounts have not been adjusted in connection with the adoption of this standard.

Collaboration Agreements - Schedule of Significant Changes in Deferred Revenue Balances, IO Collaboration (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Increase as a result of payment received from Sanofi in connection with the Amended IO Discovery Agreement	$ 375.8	$ (29.5)
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Increase as a result of payment received from Sanofi in connection with the Amended IO Discovery Agreement	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	(73.8)
Revenue recognized that was added to deferred revenue during the period	$ (37.9)

Inventories (Tables)

9 Months Ended

Sep. 30, 2019

Inventory Disclosure [Abstract]

Schedule of Inventory, Current

Inventories consist of the following:



	September 30,		December 31,
	2019		2018
Raw materials	$	229.0	$	226.8
Work-in-process	633.5		571.1
Finished goods	49.4		24.4
Deferred costs	432.4		328.9
	$	1,344.3	$	1,151.2

Collaboration Agreements - Sanofi, Antibody Narrative (Details) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Research and development	$ 663,400,000		$ 557,000,000.0		$ 2,353,500,000	$ 1,584,800,000
Cost of Treasury stock shares received	$ 48,700,000	$ 54,000,000.0	42,600,000	$ 37,600,000
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Percentage of Trial Costs borne by collaborating party					80.00%
Percentage of Trial Costs borne by entity					20.00%
Treasury stock, shares acquired	103,761
Cost of Treasury stock shares received	$ 19,400,000
Maximum amount of sales milestone payments if total sales achieve specific levels					$ 250,000,000.0
Levels of twelve month sales at which sales milestone payments would be received					$ 1,000,000,000.0
Period for achieving sales target for milestone payment, rolling basis					12 months
Praluent, Kevzara, and Dupixent \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Research and development	$ 10,200,000		$ 13,400,000		$ 29,800,000	$ 37,200,000

Legal Matters	9 Months Ended
Legal Matters	Sep. 30, 2019
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. The Company recognizes accruals for loss contingencies associated with such proceedings when it is probable that a liability will be incurred and the amount of loss can be reasonably estimated. Unless otherwise noted below, the Company is unable to predict the outcome, or estimate a range of possible loss or possible gain, of the respective proceedings. 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 and '163 Patent The Company is a party to patent infringement litigation initiated by the Company involving its European Patent No. 1,360,287 (the "'287 Patent") and its European Patent No. 2,264,163 (the "'163 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 and the '163 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 and the '163 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. Following a trial to adjudicate the claims of infringement and counterclaims of invalidity of the '287 Patent and the '163 Patent, the court issued a final judgment on February 1, 2016, 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. On appeal, 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 and subsequently issued a final order, which enjoins Kymab from infringing the '287 Patent and '163 Patent (subject to certain exceptions) and requires Kymab to destroy or deliver to a third party all products and antibodies and cells engineered to produce antibodies which infringe the '287 Patent and '163 Patent (subject to certain exceptions). Thereafter, the Supreme Court of the United Kingdom granted Kymab's application for permission to appeal the order made by the Court of Appeal with respect to an issue of validity of the '287 Patent and the '163 Patent and scheduled an oral hearing for February 11–12, 2020. The provisions of the final order of the Court of Appeal are stayed pending final determination of Kymab's appeal to the Supreme Court of the United Kingdom. The Company has also been awarded a portion of the legal fees incurred by it in connection with the proceedings in the English High Court and the Court of Appeal described above. On July 31, 2019, the Company filed an action in the English High Court for a calculation of damages relating to Kymab's infringement of the '287 Patent and the '163 Patent. 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. 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, Merus, and Novo Nordisk each filed a notice of appeal of the Opposition Division's decision on February 9, 2018, May 25, 2018, and June 26, 2018, respectively. On January 7, 2019, Merus withdrew its appeal of the '163 Patent in the EPO in connection with the previously reported global settlement. 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 claims of 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. The first jury trial in this litigation (the "First Trial") 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 First 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 in the First Trial, 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 October 5, 2017, the United States Court of Appeals for the Federal Circuit (the "Federal Circuit") reversed in part the District Court's decision and remanded for a new trial on the issues of written description and enablement. In addition, it affirmed the District Court's ruling that Amgen's patents were not obvious. On January 3, 2019, the District Court held oral argument in the remanded proceedings on the Company and the Sanofi defendants' motion for judgment on the pleadings regarding Amgen's willful infringement claim. On January 18, 2019, the District Court entered an order (i) denying the Company and the Sanofi defendants' motion for summary judgment on validity, (ii) denying Amgen's motion for partial summary judgment on estoppel, and (iii) granting the Company and the Sanofi defendants' cross-motion for summary judgment on estoppel. On February 8, 2019, the District Court granted the Company and the Sanofi defendants' motion for judgment on the pleadings, thereby dismissing Amgen's claim of willful infringement. The second jury trial in this litigation (the "Second Trial") was held before the District Court in February 2019 to determine the validity of Amgen's asserted patent claims. On February 25, 2019, the jury returned a verdict in the Second Trial generally in favor of Amgen, finding that two claims of the '165 Patent and one claim of the '741 Patent were not invalid. The jury also found that two claims of the '165 Patent were invalid for lack of adequate written description while rejecting the lack of enablement challenges to those two claims. On August 28, 2019, the District Court ruled as a matter of law that Amgen's asserted patent claims are invalid based on lack of enablement. The District Court also conditionally denied the Company and the Sanofi defendants' motion for a new trial. On October 23, 2019, Amgen filed a notice of appeal of the District Court's decision with the Federal Circuit. On March 18, 2019, Amgen filed a renewed motion for a permanent injunction to prohibit the Company and the Sanofi defendants from Commercializing Praluent in the United States (a "Permanent Injunction"), and an oral hearing on this motion was held in June 2019. Previously, the Federal Circuit stayed and then vacated a Permanent Injunction granted by the District Court in connection with the First Trial. On August 28, 2019, the District Court dismissed as moot Amgen's renewed motion for a Permanent Injunction. 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 held an oral hearing on September 11, 2018 and ruled on December 10, 2018 that the infringement proceedings would be reopened. On July 11, 2019, the Düsseldorf Regional Court found that Praluent infringes the '124 Patent and granted an injunction prohibiting the Company and Sanofi's manufacture, sale, and marketing of Praluent in Germany (the "July 11 Decision"). On July 12, 2019, the Company and Sanofi appealed the July 11 Decision to the Higher Regional Court of Düsseldorf (the "Higher Regional Court"). An oral hearing on the merits of the appeal to the Higher Regional Court has been scheduled for April 2, 2020. On August 5, 2019 and October 31, 2019, the Higher Regional Court denied the Company and Sanofi's requests for a stay of preliminary enforcement of the July 11 Decision pending the appeal on the merits. On July 12, 2018, Sanofi-Aventis Deutschland GmbH, Sanofi-Aventis Groupe S.A., and Sanofi Winthrop Industrie S.A. filed an action in the Federal Patents Court (the "FPC") in Munich, Germany, seeking a compulsory license from Amgen based on the '124 Patent for the continued commercializing of Praluent in Germany. This compulsory license action included a request for a provisional compulsory license. The FPC held an oral hearing on September 6, 2018 and denied the Sanofi parties' request for the provisional compulsory license. On January 16, 2019, the Sanofi parties appealed the FPC's denial of the provisional compulsory license to the Federal Court of Justice (the "FCJ") of Germany. The FCJ held an oral hearing on June 4, 2019 on the appeal of the provisional compulsory license ruling and dismissed the Sanofi parties' appeal. On September 16, 2019, the Sanofi parties filed a brief to withdraw the compulsory license action with the FPC. 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 S.A., 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 (originally scheduled for February 12, 2019) has yet to be scheduled. 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. An oral hearing on the oppositions against the '124 Patent was held on November 28–30, 2018, at which the Opposition Division upheld the validity of the '124 Patent's claims in amended form. The Company and Sanofi filed notices of appeal to the Technical Board of Appeal (the "TBA") of the EPO on November 30, 2018. An oral hearing before the TBA has been scheduled for March 24–25, 2020. The Company has recorded an accrual for loss contingencies associated with the '124 Patent proceedings discussed above. The ultimate resolution of these proceedings is not expected to have a material impact on the Company’s financial statements. 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 (the "Tokyo District Court") 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. On January 17, 2019, the Tokyo District Court upheld the validity of the '333 Patent and '288 Patent and ordered a permanent injunction against Sanofi K.K. to stop manufacturing, selling or otherwise transferring, and offering to sell or otherwise transfer Praluent (alirocumab) in Japan (as well as importing Praluent (alirocumab) into Japan) and to dispose of all product. However, the Tokyo District Court stayed the enforcement of such injunction pending appeal to the Intellectual Property High Court of Japan (the "IPHC"). On January 30, 2019, Sanofi K.K. appealed the Tokyo District Court's decision in the infringement proceedings to the IPHC. Following an oral hearing on October 30, 2019, the IPHC affirmed the Tokyo District Court's decision in the infringement proceedings. The injunction will remain stayed pending appeal of the IPHC's decision to the Supreme Court of Japan. 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. Oral hearings on the Additional IPR Petitions before the PTAB were held on November 14, 2018. On February 14, 2019, the PTAB issued final written decisions on the Additional IPR Petitions, invalidating all 17 claims of the '487 Patent as obvious based on one of the Additional IPR Petitions while declining to hold the challenged claims of the '487 Patent invalid based on the other. In April 2019, the parties filed notices of appeal with the Federal Circuit appealing the PTAB's respective adverse final written decisions on the Additional IPR Petitions. 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 the Company and the Sanofi parties' motion for summary judgment on the issue of indefiniteness of the '487 Patent claims was held on July 12, 2018. On August 24, 2018, the court issued an order denying this motion and construed the disputed claim terms as proposed by Amgen. On February 28, 2019, the court granted a joint stipulation by the parties to stay the litigation pending resolution of the appeals of the PTAB's final written decisions on the Additional IPR Petitions discussed above. On September 30, 2016, Sanofi initiated a revocation proceeding in the United Kingdom to invalidate the U.K. counterpart of European Patent No. 2,292,665 (the "'665 Patent"), another patent owned by Immunex relating to antibodies that bind the human interleukin-4 receptor. At the joint request of the parties to the revocation proceeding, the U.K. Patents Court ordered on January 30, 2017 that the revocation action be stayed pending the final determination of the currently pending EPO opposition proceedings initiated by the Company and Sanofi in relation to the '665 Patent. The oral hearing before the EPO on the oppositions occurred on November 20, 2017, at which the claims of the '665 Patent were found invalid and the patent was revoked. A final written decision of revocation of the '665 Patent was issued by the EPO on January 4, 2018. Immunex filed a notice of appeal of the EPO's decision on January 31, 2018. On September 20, 2017 and September 21, 2017, respectively, the Company and Sanofi initiated opposition proceedings in the EPO against Immunex's European Patent No. 2,990,420 (the "'420 Patent"), a divisional patent of the '665 Patent (i.e., a patent that shares the same priority date, disclosure, and patent term of the parent '665 Patent but contains claims to a different invention). The oral hearing before the EPO on the oppositions occurred on February 14–15, 2019, at which the '420 Patent was revoked in its entirety. Immunex filed a notice of appeal of the EPO's decision on May 31, 2019. The original patent term of the Immunex patents is set to expire in 2021. 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 (dismissed on October 24, 2018); 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. On March 20, 2019, the court issued its Opinion and Order on Claim Construction (the "Claim Construction Order") in the '688 Patent infringement litigation. Pursuant to the Claim Construction Order, on April 1, 2019, the court approved a joint stipulation and entered a partial judgment of noninfringement of the '688 Patent of nine asserted claims. On August 14, 2019, the court issued a second Opinion and Order on Claim Construction concerning the one remaining asserted claim in this litigation. On September 5, 2019, the court entered a stipulated judgment of noninfringement and dismissed with prejudice all of the Novartis Parties' claims of the '688 Patent, finding that the manufacture, use, offer for sale, sale, or importation into the United States of aflibercept does not infringe the claims of the '688 Patent. On May 14, 2019, the Company filed an IPR in the USPTO seeking a declaration of invalidity of the '688 Patent. On September 26, 2019, in connection with the dismissal of the '688 Patent infringement litigation discussed above, the Company and the Novartis Parties filed a joint motion to terminate the IPR petition, and the PTAB dismissed the IPR petition on October 1, 2019. Department of Justice Investigations 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. In September 2019, the Company and Regeneron Healthcare Solutions, Inc., a wholly-owned subsidiary of the Company, each received a civil investigative demand ("CID") from the U.S. Department of Justice pursuant to the federal False Claims Act relating to remuneration paid to physicians in the form of consulting fees, advisory boards, speaker fees, and payment or reimbursement for travel and entertainment allegedly in violation of the federal Anti-Kickback Statute. The CIDs relate to EYLEA, Praluent, Dupixent, ZALTRAP, ARCALYST, and Kevzara and cover the period from January 2015 to the present. The Company is cooperating with this investigation.

Leases (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Schedule of amounts recognized in the Condensed Consolidated Balance Sheet



		September 30,
	Classification	2019
Finance lease right-of-use assets	Property, plant, and equipment, net ⁽¹⁾	$	663.7
Finance lease liabilities	Finance lease liabilities (noncurrent)	$	712.7

⁽¹⁾ Finance lease right-of-use assets are recorded net of accumulated amortization of $72.5 million as of September 30, 2019.

Schedule of lease cost and other information

Finance lease costs consist of the following:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Amortization of right-of-use assets	$	3.6	$	10.8
Interest on lease liabilities	6.9		21.4
	$	10.5	$	32.2

Other information related to our finance lease includes the following:



	September 30,
	2019
Remaining lease term (in years)	2.42
Discount rate	2.89	%

Schedule of maturities of lease liabilities

The following is an analysis of lease liability maturities as of September 30, 2019:



	Operating Leases			Finance Leases
2019	$	1.9		$	5.7
2020	8.0			21.2
2021	6.6			20.1
2022	3.3			725.0
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	28.4			772.0
Imputed interest	(3.1		)	(53.2		)
Debt financing costs	—			(6.1		)
Total lease liabilities	$	25.3		$	712.7

Schedule of maturities of lease liabilities

The following is an analysis of lease liability maturities as of September 30, 2019:



	Operating Leases			Finance Leases
2019	$	1.9		$	5.7
2020	8.0			21.2
2021	6.6			20.1
2022	3.3			725.0
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	28.4			772.0
Imputed interest	(3.1		)	(53.2		)
Debt financing costs	—			(6.1		)
Total lease liabilities	$	25.3		$	712.7

Schedule of future minimum noncancelable lease commitments



	Operating Leases		Capital and Facility Lease Obligations
2019	$	10.4	$	26.4
2020	3.8		28.4
2021	3.4		27.9
2022	2.2		7.0
2023	1.5		—
Thereafter	4.1		—
	$	25.4	$	89.7

Schedule of future minimum noncancelable lease commitments



	Operating Leases		Capital and Facility Lease Obligations
2019	$	10.4	$	26.4
2020	3.8		28.4
2021	3.4		27.9
2022	2.2		7.0
2023	1.5		—
Thereafter	4.1		—
	$	25.4	$	89.7

Statement of Cash Flows

9 Months Ended

Sep. 30, 2019

Supplemental Cash Flow Information [Abstract]

Statement of Cash Flows

As described in Note 6, included in our purchases of marketable securities during the nine months ended September 30, 2019 is our purchase of Alnylam common stock.

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:



	September 30,		September 30,
	2019		2018
Cash and cash equivalents	$	1,384.8	$	1,087.8
Restricted cash included in Other noncurrent assets	12.5		12.5
Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows	$	1,397.3	$	1,100.3

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 September 30, 2019 and December 31, 2018 were $100.5 million and $54.5 million, respectively, of accrued capital expenditures. Included in accounts payable, accrued expenses, and other liabilities as of September 30, 2018 and December 31, 2017 were $40.5 million and $41.8 million, respectively, of accrued capital expenditures.

As described in Note 3, during the nine months ended September 30, 2019, we purchased (by issuing a credit towards the amount owed by Sanofi) 210,733 shares of our Common Stock from Sanofi to satisfy Sanofi's funding obligation related to Libtayo development costs, and recorded the cost of the shares received, or $73.3 million, as Treasury Stock. During the nine months ended September 30, 2018, we purchased (by issuing a credit towards the amount owed by Sanofi) 215,387 shares of our Common Stock from Sanofi, and recorded the cost of the shares received, or $75.8 million, as Treasury Stock.

Net Income Per Share (Tables)

9 Months Ended

Sep. 30, 2019

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 September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Net income - basic and diluted	$	669.6	$	594.7	$	1,323.8	$	1,624.0

(Shares in millions)
Weighted average shares - basic	109.4		108.0		109.2		107.8
Effect of dilutive securities:
Stock options	4.8		7.1		5.5		7.0
Weighted average shares - diluted	114.2		115.1		114.7		114.8

Net income per share - basic	$	6.12	$	5.50	$	12.12	$	15.06
Net income per share - diluted	$	5.86	$	5.17	$	11.54	$	14.14

Antidilutive Securities

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



	Three Months Ended September 30,		Nine Months Ended September 30,
(Shares in millions)	2019	2018	2019	2018
Stock options	18.3	14.4	18.2	14.8
Restricted stock	0.4	—	0.4	0.1

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Revenues	$ 2,048.4	$ 1,663.5	$ 5,693.9	$ 4,783.0
Expenses:
Research and development	663.4	557.0	2,353.5	1,584.8
Selling, general, and administrative	419.9	369.2	1,248.0	1,064.9
Total expenses	1,309.9	1,036.6	4,159.8	2,966.7
Income from operations	738.5	626.9	1,534.1	1,816.3
Other income (expense):
Other income (expense), net	37.8	16.4	28.7	81.8
Interest expense	(7.8)	(7.4)	(23.5)	(20.8)
Total other income (expense)	30.0	9.0	5.2	61.0
Income before income taxes	768.5	635.9	1,539.3	1,877.3
Income tax expense	(98.9)	(41.2)	(215.5)	(253.3)
Net income	$ 669.6	$ 594.7	$ 1,323.8	$ 1,624.0
Net income per share - basic (in dollars per share)	$ 6.12	$ 5.50	$ 12.12	$ 15.06
Net income per share - diluted (in dollars per share)	$ 5.86	$ 5.17	$ 11.54	$ 14.14
Weighted average shares outstanding - basic (in shares)	109.4	108.0	109.2	107.8
Weighted average shares - diluted (in shares)	114.2	115.1	114.7	114.8
Statements of Comprehensive Income
Net income	$ 669.6	$ 594.7	$ 1,323.8	$ 1,624.0
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on debt securities	1.0	0.7	31.5	(6.9)
Unrealized (loss) gain on cash flow hedges	(0.3)		(2.7)
Unrealized (loss) gain on cash flow hedges		0.3		2.4
Comprehensive income	670.3	595.7	1,352.6	1,619.5
Product
Revenues:
Revenues	1,238.3	1,025.5	3,548.0	3,009.8
Expenses:
Cost of goods sold	115.9	30.8	253.8	136.1
Collaboration and contract manufacturing
Expenses:
Cost of goods sold	110.7	79.6	304.5	180.9
Sanofi \| Product and service, other
Revenues:
Revenues	404.2	256.3	999.7	683.5
Bayer \| Product and service, other
Revenues:
Revenues	302.8	264.4	868.0	775.2
Other \| Product and service, other
Revenues:
Revenues	$ 103.1	$ 117.3	$ 278.2	$ 314.5

Leases - Finance lease costs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Amortization of right-of-use assets	$ 3.6	$ 10.8
Interest on lease liabilities	6.9	21.4
Finance lease costs	$ 10.5	$ 32.2

Recently Issued Accounting Standards (Policies)	9 Months Ended
Recently Issued Accounting Standards (Policies)	Sep. 30, 2019
Accounting Policies [Abstract]
Leases	Leases with an initial term of 12 months or less are not recorded on the balance sheet. Our lease terms may include options to extend or terminate a lease when it is reasonably certain that we will exercise that option. We account for lease components (e.g., rental payments) separately from non-lease components (e.g., common area maintenance costs).
Legal Matters	Costs associated with the Company's involvement in legal proceedings are expensed as incurred.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In June 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires an entity to measure and recognize expected credit losses for certain financial instruments, including trade receivables, as an allowance that reflects the entity's current estimate of credit losses expected to be incurred. For available-for-sale debt securities with unrealized losses, the standard requires allowances to be recorded through net income instead of directly reducing the amortized cost of the investment under the current other-than-temporary impairment model. The standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. We do not expect the adoption of this standard to have a significant impact on our financial statements or internal controls; however, the ultimate impact will depend on the composition of the Company's portfolio of financial instruments as of the adoption date.

Leases - Maturities on leases (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Operating Leases
2019	$ 1.9
2020	8.0
2021	6.6
2022	3.3
2023	2.0
2024	2.3
Thereafter	4.3
Total undiscounted lease payments	28.4
Imputed interest	(3.1)
Debt financing costs	0.0
Total lease liabilities	25.3
Finance Leases
2019	5.7
2020	21.2
2021	20.1
2022	725.0
2023	0.0
2024	0.0
Thereafter	0.0
Total undiscounted lease payments	772.0
Imputed interest	(53.2)
Debt financing costs	(6.1)
Finance lease liabilities	$ 712.7
Operating Leases
2019		$ 10.4
2020		3.8
2021		3.4
2022		2.2
2023		1.5
Thereafter		4.1
Operating Leases		25.4
Capital and Facility Lease Obligations
2019		26.4
2020		28.4
2021		27.9
2022		7.0
2023		0.0
Thereafter		0.0
Capital and Facility Lease Obligations		$ 89.7

Interim Financial Statements - Narrative (Details) $ in Millions	Jan. 01, 2019 USD ($)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	$ 33.2

Collaboration Agreements

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Collaboration Agreements

a. Sanofi

The collaboration revenue we earned from Sanofi is detailed below:



	Three Months Ended September 30,						Nine Months Ended September 30,
Sanofi Collaboration Revenue	2019			2018			2019			2018
Antibody:
Reimbursement of Regeneron research and development expenses	$	60.2		$	76.2		$	216.5		$	201.0
Reimbursement of Regeneron commercialization-related expenses	111.6			103.7			349.3			292.8
Reimbursement for Regeneron's manufacturing of commercial supplies	78.5			40.3			133.3			94.4
Regeneron's share of profits (losses) in connection with commercialization of antibodies	94.2			(38.9		)	105.2			(182.6		)
Other	4.8			(7.2		)	(0.6		)	(12.3		)
Total Antibody	349.3			174.1			803.7			393.3
Immuno-oncology:
Reimbursement of Regeneron research and development expenses	38.0			74.8			120.9			225.7
Reimbursement of Regeneron commercialization-related expenses	3.0			3.2			7.0			6.5
Amounts recognized in connection with up-front payments received	18.5			7.9			73.8			65.2
Other	(4.6		)	(3.7		)	(5.7		)	(7.2		)
Total Immuno-oncology	54.9			82.2			196.0			290.2
	$	404.2		$	256.3		$	999.7		$	683.5

Antibody

The Company is party to a global, strategic collaboration with Sanofi to discover, develop, and commercialize fully human monoclonal antibodies (the "Antibody Collaboration"). Under the companies' Antibody License and Collaboration Agreement, 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. All other agreed-upon worldwide development expenses incurred by both companies are funded by Sanofi. The Company recognized as research and development expense $10.2 million and $13.4 million during the three months ended September 30, 2019 and 2018, respectively, and during the nine months ended September 30, 2019 and 2018, the Company recognized as research and development expense $29.8 million and $37.2 million, respectively, its share of antibody development expenses that Sanofi incurred related to Dupixent^® (dupilumab), Praluent^®(alirocumab), and Kevzara^® (sarilumab).

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 dupilumab and REGN3500 (collectively, the "Dupilumab/REGN3500 Eligible Investments"). Refer to the "Immuno-Oncology" section below for further details regarding the Letter Agreement. During the three months ended September 30, 2019, Sanofi elected to sell, and we elected to purchase (in cash), 69,143 shares of the Company's Common Stock in connection with Sanofi's funding obligation for Dupilumab/REGN3500 Eligible Investments. Consequently, we recorded the cost of the shares received, or $19.4 million, as Treasury Stock during the three months ended September 30, 2019.

Sanofi leads commercialization activities for products developed under the Antibody Collaboration, subject to the Company's right to co-commercialize 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 our share of profits and losses, as well as sales milestones, is deemed to be constrained as of September 30, 2019, and therefore has not been included in the transaction price.

The following table summarizes contract balances in connection with the Company's Antibody Collaboration with Sanofi:



	September 30,		December 31,
	2019		2018
Accounts receivable	$	332.5	$	138.2
Deferred revenue	$	377.0	$	236.1

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Increase due to shipments of commercial supplies to Sanofi	$	294.3
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(159.0	)

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. Therefore, we do not disclose the value of the transaction price allocated to our remaining unsatisfied performance obligations.

Immuno-Oncology

In 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 Amended and Restated Immuno-oncology Discovery and Development Agreement ("Amended IO Discovery Agreement"), and an Immuno-oncology License and Collaboration Agreement ("IO License and Collaboration Agreement").

Effective December 31, 2018, the Company and Sanofi entered into an Amended IO Discovery Agreement, which narrowed the scope of the existing discovery and development activities conducted by the Company ("IO Development Activities") under the

2015 IO Discovery Agreement to developing therapeutic bispecific antibodies targeting (i) BCMA and CD3 (the "BCMAxCD3 Program") and (ii) MUC16 and CD3 (the "MUC16xCD3 Program") through clinical proof-of-concept. The Amended IO Discovery Agreement provided for Sanofi’s payment of $461.9 million to the Company as consideration for (x) the termination of the 2015 IO Discovery Agreement, (y) the prepayment for certain IO Development Activities regarding the BCMAxCD3 Program and the MUC16xCD3 Program, and (z) the reimbursement of costs incurred by the Company under the 2015 IO Discovery Agreement during the fourth quarter of 2018.

If Sanofi exercises its option to license rights to a BCMAxCD3 Program antibody or MUC16xCD3 Program antibody thereunder, it will co-develop these drug candidates with the Company through product approval. Sanofi will fund development costs up front for a BCMAxCD3 Program antibody and we will reimburse half of the total development costs for such antibody from our share of future IO Collaboration profits to the extent they are sufficient for this purpose. In addition, we and Sanofi will share equally, on an ongoing basis, the development costs for a MUC16xCD3 Program antibody.

Under the terms of the IO License and Collaboration Agreement, the parties are co-developing and co-commercializing Libtayo (cemiplimab), an antibody targeting the receptor known as programmed cell death protein 1 (PD-1). The parties share equally, on an ongoing basis, agreed-upon development and commercialization expenses for Libtayo. Pursuant to the Letter Agreement, the Libtayo development budget was increased and the Company has agreed to allow Sanofi to satisfy in whole or in part its funding obligations with respect to the Libtayo development and Dupilumab/REGN3500 Eligible Investments by selling up to an aggregate of 1,400,000 shares (of which 869,828 currently remains available) of our Common Stock directly or indirectly owned by Sanofi through September 30, 2020. If Sanofi desires to sell shares of our Common Stock during the term of the Letter Agreement to satisfy a portion or all of its funding obligations for the Libtayo development and/or Dupilumab/REGN3500 Eligible Investments, we may elect to purchase, in whole or in part, such shares from Sanofi. If we do 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. During the three months ended September 30, 2019, Sanofi elected to sell, and we elected to purchase (by issuing a credit towards the amount owed by Sanofi), 103,761 shares of the Company's Common Stock to satisfy Sanofi's funding obligation related to Libtayo development costs. Consequently, we recorded the cost of the shares received, or $29.2 million, as Treasury Stock during the three months ended September 30, 2019. Refer to the "Antibody" section above for a description of share transactions related to Dupilumab/REGN3500 Eligible Investments.

The Company has principal control over the development of Libtayo and leads commercialization activities in the United States, while Sanofi leads commercialization activities outside of the United States and the parties equally share profits and losses from worldwide sales. As it relates to revenue earned in connection with the IO Collaboration, "Reimbursement of Regeneron commercialization-related expenses" represents reimbursement of costs by Sanofi in connection with the commercialization of Libtayo outside of the United States.

The following table summarizes contract balances in connection with the Company's IO Collaboration with Sanofi:



	September 30,		December 31,
	2019		2018
Accounts receivable	$	8.2	$	77.9
Deferred revenue	$	602.0	$	289.9

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Increase as a result of payment received from Sanofi in connection with the Amended IO Discovery Agreement	$	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(73.8	)
Revenue recognized that was added to deferred revenue during the period	$	(37.9	)

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 September 30, 2019 was $1,196.9 million. This amount is expected to be recognized as revenue over the remaining period in which the Company is obligated to satisfy its performance obligation in connection with performing development activities.

b. Bayer



	Three Months Ended September 30,				Nine Months Ended September 30,
Bayer EYLEA Collaboration Revenue	2019		2018		2019		2018
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	275.0	$	243.2	$	793.3	$	721.5
Reimbursement of Regeneron EYLEA development expenses	5.0		1.7		15.6		8.8
Other	22.8		20.7		59.1		45.4
	$	302.8	$	265.6	$	868.0	$	775.7

The Company is party to a license and collaboration agreement with Bayer for the global development and commercialization of EYLEA outside the United States. 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 currently entitled to receive a tiered percentage of between 33.5% and 40.0% of EYLEA net product sales. In addition, the Company and Bayer share the funding of agreed-upon EYLEA development costs.

c. Teva

In 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 during 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.

The Company recognized $57.4 million and $69.1 million of revenue for the three months ended September 30, 2019 and 2018, respectively, and $172.2 million and $196.6 million for the nine months ended September 30, 2019 and 2018, respectively, in connection with the Teva Collaboration Agreement.

The following table summarizes contract balances in connection with the Teva Collaboration Agreement:



	September 30,		December 31,
	2019		2018
Accounts receivable (recorded within Prepaid expenses and other current assets)	$	36.0	$	28.8
Deferred revenue	$	127.8	$	194.5

Significant changes in deferred revenue balances are as follows:



	Nine Months Ended September 30, 2019
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(68.7	)

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 September 30, 2019 was $300.6 million. This amount is expected to be recognized as revenue over the remaining period in which the Company is obligated to satisfy its performance obligation in connection with performing development activities.

d. Alnylam

In April 2019, the Company and Alnylam Pharmaceuticals, Inc. entered into a global, strategic collaboration to discover, develop, and commercialize RNA interference ("RNAi") therapeutics for a broad range of diseases by addressing therapeutic disease targets expressed in the eye and central nervous system ("CNS"), in addition to a select number of targets expressed in the liver. The collaboration is governed by a Master Collaboration Agreement (the "Master Agreement") (including the form of a License Agreement and a Co-Commercialization Collaboration Agreement). Under the terms of the Master Agreement, we made an up-front payment of $400.0 million to Alnylam, which was recorded in Research and development expense during the second quarter of 2019. For each program, we will provide Alnylam with a specified amount of funding at program initiation and at lead candidate designation, and Alnylam is eligible to receive up to $200.0 million in clinical proof-of-principle milestones for eye or CNS programs.

Under the collaboration, the parties plan to perform discovery research until designation of lead candidates. Following designation of a lead candidate, the parties may further advance such lead candidate under either a License Agreement or a Co-Commercialization Collaboration Agreement structure. The initial target nomination and discovery period is five years (which may under certain situations automatically be extended for up to seven years in the aggregate) (the "Research Term"). In addition, we have an option to extend the Research Term for an additional five-year period for a research extension fee ranging from $200.0 million to $400.0 million; the actual amount of the fee will be determined based on the acceptance of one or more INDs (or their equivalent in certain other countries) for programs in the eye and CNS.

In connection with the collaboration, we and Alnylam also entered into a Stock Purchase Agreement. Pursuant to the terms of the Stock Purchase Agreement, we purchased shares of Alnylam common stock for aggregate cash consideration of $400.0 million.

In August 2019, the parties entered into a Co-Commercialization Collaboration Agreement for a silencing RNA ("siRNA") therapeutic targeting the C5 component of the human complement pathway being developed by Alnylam, with Alnylam as the lead party, and a License Agreement for a combination product consisting of such siRNA therapeutic and a fully human monoclonal antibody targeting C5 being developed by us, with us as the licensee. The C5 siRNA Co-Commercialization Collaboration Agreement is consistent with the financial terms contained in the form of the existing Co-Commercialization Collaboration Agreement with Alnylam and the parties will share in development expenses equally. The C5 siRNA License Agreement contains a flat low double-digit royalty payable to Alnylam on our potential future net sales of the combination product only subject to customary reductions, as well as up to $325.0 million in commercial milestones.

Marketable Securities

9 Months Ended

Sep. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable securities as of September 30, 2019 and December 31, 2018 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 September 30, 2019	Cost Basis		Gains		Losses			Value
Corporate bonds	$	3,880.6	$	27.0	$	(0.6	)	$	3,907.0
U.S. government and government agency obligations	65.9		0.2		(0.1		)	66.0
Sovereign bonds	26.9		0.5		—			27.4
Commercial paper	108.8		—		—			108.8
Certificates of deposit	66.7		0.1		—			66.8
	$	4,148.9	$	27.8	$	(0.7	)	$	4,176.0

As of December 31, 2018
Corporate bonds	$	2,734.8	$	1.0	$	(17.4	)	$	2,718.4
U.S. government and government agency obligations	110.4		—		(1.0		)	109.4
Sovereign bonds	7.6		—		—			7.6
Commercial paper	113.8		—		—			113.8
Certificates of deposit	60.0		—		—			60.0
	$	3,026.6	$	1.0	$	(18.4	)	$	3,009.2

The Company classifies its investments in available-for-sale debt securities based on their contractual maturity dates. The available-for-sale debt securities listed as of September 30, 2019 mature at various dates through September 2024. The fair values of available-for-sale debt security investments by contractual maturity consist of the following:



	September 30,		December 31,
	2019		2018
Maturities within one year	$	1,493.1	$	1,342.2
Maturities after one year through five years	2,682.9		1,667.0
	$	4,176.0	$	3,009.2



	Less than 12 Months					12 Months or Greater					Total
As of September 30, 2019	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	294.8	$	(0.3	)	$	216.3	$	(0.3	)	$	511.1	$	(0.6	)
U.S. government and government agency obligations	18.5		(0.1		)	19.5		—			38.0		(0.1		)
	$	313.3	$	(0.4	)	$	235.8	$	(0.3	)	$	549.1	$	(0.7	)

As of December 31, 2018
Corporate bonds	$	1,482.6	$	(6.1	)	$	801.6	$	(11.3	)	$	2,284.2	$	(17.4	)
U.S. government and government agency obligations	—		—			99.1		(1.0		)	99.1		(1.0		)
	$	1,482.6	$	(6.1	)	$	900.7	$	(12.3	)	$	2,383.3	$	(18.4	)

There were no realized losses on sales of marketable securities, and realized gains were not material, for the three and nine months ended September 30, 2019. Realized gains and losses on sales of marketable securities were not material for the three and nine months ended September 30, 2018.

With respect to marketable securities, for the three and nine months ended September 30, 2019 and 2018, amounts reclassified from Accumulated other comprehensive income (loss) into Other income (expense), net were related to realized gains and losses on sales of available-for-sale debt securities.

Leases - Other information related to finance leases (Details)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Remaining lease term (in years)	2 years 5 months 1 day
Discount rate	2.89%

Net Income Per Share - Schedule of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income - basic and diluted	$ 669.6	$ 193.1	$ 461.1	$ 594.7	$ 551.4	$ 477.9	$ 1,323.8	$ 1,624.0
Weighted average shares outstanding - basic (in shares)	109.4			108.0			109.2	107.8
Dilutive effect of stock options (in shares)	4.8			7.1			5.5	7.0
Weighted average shares - diluted (in shares)	114.2			115.1			114.7	114.8
Net income per share - basic (in dollars per share)	$ 6.12			$ 5.50			$ 12.12	$ 15.06
Net income per share - diluted (in dollars per share)	$ 5.86			$ 5.17			$ 11.54	$ 14.14

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e1337-109256

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=117326831&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

+ Details

- Definition

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

+ References + Details

Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 2,048.4	$ 1,663.5	$ 5,693.9	$ 4,783.0
Product
Disaggregation of Revenue [Line Items]
Revenues	1,238.3	1,025.5	3,548.0	3,009.8
UNITED STATES \| EYLEA
Disaggregation of Revenue [Line Items]
Revenues	1,187.7	1,021.8	3,422.1	2,997.8
UNITED STATES \| Libtayo
Disaggregation of Revenue [Line Items]
Revenues	47.6	0.0	115.2	0.0
UNITED STATES \| ARCALYST
Disaggregation of Revenue [Line Items]
Revenues	3.0	3.7	10.7	12.0
UNITED STATES \| Product
Disaggregation of Revenue [Line Items]
Revenues	$ 1,238.3	$ 1,025.5	$ 3,548.0	$ 3,009.8

Leases - Amounts recognized in Condensed Consolidated Balance Sheet (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Abstract]
Finance lease right-of-use assets	$ 663.7
Finance lease liabilities	712.7
Accumulated amortization	$ 72.5

Statement of Cash Flows (Tables)

9 Months Ended

Sep. 30, 2019

Supplemental Cash Flow Information [Abstract]

Restrictions on Cash and Cash Equivalents



	September 30,		September 30,
	2019		2018
Cash and cash equivalents	$	1,384.8	$	1,087.8
Restricted cash included in Other noncurrent assets	12.5		12.5
Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows	$	1,397.3	$	1,100.3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 1,323.8	$ 1,624.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	156.0	105.4
Non-cash compensation expense	330.8	300.7
Other non-cash items, net	113.2	(82.7)
Deferred taxes	(110.0)	(33.5)
Changes in assets and liabilities:
Increase in Sanofi, Bayer, and trade accounts receivable	(460.9)	(228.6)
Increase in inventories	(227.2)	(281.6)
Decrease (increase) in prepaid expenses and other assets	21.2	(87.8)
Increase (decrease) in deferred revenue	375.8	(29.5)
Increase in accounts payable, accrued expenses, and other liabilities	119.9	179.9
Total adjustments	318.8	(157.7)
Net cash provided by operating activities	1,642.6	1,466.3
Cash flows from investing activities:
Purchases of marketable and other securities	(2,834.9)	(1,533.6)
Sales or maturities of marketable securities	1,306.4	644.1
Capital expenditures	(290.6)	(297.6)
Other	0.0	(10.0)
Net cash used in investing activities	(1,819.1)	(1,197.1)
Cash flows from financing activities:
Proceeds from issuance of Common Stock	163.5	87.4
Payments in connection with Common Stock tendered for employee tax obligations	(40.5)	(77.1)
Repurchases of Common Stock	(29.4)	(4.4)
Net cash provided by financing activities	93.6	5.9
Net (decrease) increase in cash, cash equivalents, and restricted cash	(82.9)	275.1
Cash, cash equivalents, and restricted cash at beginning of period	1,480.2	825.2
Cash, cash equivalents, and restricted cash at end of period	$ 1,397.3	$ 1,100.3

Collaboration Agreements - Bayer Narrative (Details) - Bayer	9 Months Ended
	Sep. 30, 2019
Minimum
Disaggregation of Revenue [Line Items]
Revenue based on percentage of annual sales in Japan	33.50%
Maximum
Disaggregation of Revenue [Line Items]
Revenue based on percentage of annual sales in Japan	40.00%

Collaboration Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 2,048.4	$ 1,663.5	$ 5,693.9	$ 4,783.0
Product and service, other \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	349.3	174.1	803.7	393.3
Product and service, other \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues	54.9	82.2	196.0	290.2
Product and service, other \| Sanofi
Disaggregation of Revenue [Line Items]
Revenues	404.2	256.3	999.7	683.5
Reimbursement of Regeneron research and development expenses \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	60.2	76.2	216.5	201.0
Reimbursement of Regeneron research and development expenses \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues	38.0	74.8	120.9	225.7
Reimbursement of Regeneron commercialization-related expenses \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	111.6	103.7	349.3	292.8
Reimbursement of Regeneron commercialization-related expenses \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues	3.0	3.2	7.0	6.5
Reimbursement for Regeneron's manufacturing of commercial supplies \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	78.5	40.3	133.3	94.4
Regeneron's share of profits (losses) in connection with commercialization of antibodies \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	94.2	(38.9)	105.2	(182.6)
Other \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues	4.8	(7.2)	(0.6)	(12.3)
Other \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues	(4.6)	(3.7)	(5.7)	(7.2)
Amounts recognized in connection with up-front payments received \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues	$ 18.5	$ 7.9	$ 73.8	$ 65.2

Collaboration Agreements - Schedule of Contract Balances, Teva Collaboration (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable (recorded within Prepaid expenses and other current assets)	$ 226.9	$ 243.3
Teva
Disaggregation of Revenue [Line Items]
Accounts receivable (recorded within Prepaid expenses and other current assets)	36.0	28.8
Deferred revenue	$ 127.8	$ 194.5

Legal Matters (Details) € in Thousands	Jul. 31, 2017 claim	Sep. 26, 2016 EUR (€)	Apr. 01, 2019 claim	Feb. 25, 2019 claim	Feb. 14, 2019 claim
Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, damages sought, per unit produced \| €		€ 10
Loss contingency, damages sought \| €		€ 10,000
'165 Patent \| Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Pending claims				2
Invalid claims				2
'487 Patent
Loss Contingencies [Line Items]
Number of IPR filed	2
Number of claims invalidated					17
'741 Patent \| Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Pending claims				1
'688 Patent \| Pending Litigation
Loss Contingencies [Line Items]
Asserted claims			9

Collaboration Agreements - Sanofi, Immuno-Oncology Narrative (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Cost of Treasury stock shares received	$ 48.7	$ 54.0	$ 42.6	$ 37.6
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Maximum shares the collaborator could sell (in shares)	869,828				869,828		1,400,000
Cost of Treasury stock shares received	$ 29.2				$ 73.3	$ 75.8
Revenue, performance obligation amount	$ 1,196.9				$ 1,196.9
Sanofi Collaboration Agreement, Immuno-oncology \| Libtayo
Disaggregation of Revenue [Line Items]
Treasury stock, shares acquired	69,143				210,733	215,387
Sanofi Collaboration Agreement, Immuno-oncology \| Amended IO Discovery Agreement
Disaggregation of Revenue [Line Items]
Aggregate payment received with regards to amendment							$ 461.9

Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 313.3	$ 1,482.6
Unrealized Loss - Less than 12 months	(0.4)	(6.1)
Fair Value - 12 Months or Greater	235.8	900.7
Unrealized Loss - 12 Months or Greater	(0.3)	(12.3)
Fair Value - Total	549.1	2,383.3
Unrealized Loss - Total	(0.7)	(18.4)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	294.8	1,482.6
Unrealized Loss - Less than 12 months	(0.3)	(6.1)
Fair Value - 12 Months or Greater	216.3	801.6
Unrealized Loss - 12 Months or Greater	(0.3)	(11.3)
Fair Value - Total	511.1	2,284.2
Unrealized Loss - Total	(0.6)	(17.4)
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	18.5	0.0
Unrealized Loss - Less than 12 months	(0.1)	0.0
Fair Value - 12 Months or Greater	19.5	99.1
Unrealized Loss - 12 Months or Greater	0.0	(1.0)
Fair Value - Total	38.0	99.1
Unrealized Loss - Total	$ (0.1)	$ (1.0)

Income Taxes (Details)	3 Months Ended		9 Months Ended
Income Taxes (Details)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate	12.90%	6.50%	14.00%	13.50%

Net Income Per Share

9 Months Ended

Sep. 30, 2019

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 September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Net income - basic and diluted	$	669.6	$	594.7	$	1,323.8	$	1,624.0

(Shares in millions)
Weighted average shares - basic	109.4		108.0		109.2		107.8
Effect of dilutive securities:
Stock options	4.8		7.1		5.5		7.0
Weighted average shares - diluted	114.2		115.1		114.7		114.8

Net income per share - basic	$	6.12	$	5.50	$	12.12	$	15.06
Net income per share - diluted	$	5.86	$	5.17	$	11.54	$	14.14

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



	Three Months Ended September 30,		Nine Months Ended September 30,
(Shares in millions)	2019	2018	2019	2018
Stock options	18.3	14.4	18.2	14.8
Restricted stock	0.4	—	0.4	0.1

Share repurchase program

In November 2019, our board of directors authorized a share repurchase program to repurchase up to $1.0 billion of our Common Stock. The share repurchase program permits the Company to effect repurchases through a variety of methods, including open-market transactions (including pursuant to a trading plan adopted in accordance with Rule 10b5-1 of the Exchange Act), privately negotiated transactions, accelerated share repurchases, block trades, and other transactions in compliance with Rule 10b-18 of the Exchange Act. Repurchases may be made from time to time at management’s discretion, and the timing and amount of any such repurchases will be determined based on share price, market conditions, legal requirements, and other relevant factors. The program has no time limit and can be discontinued at any time. No shares have been repurchased under the program to date, and there can be no assurance as to the timing or number of shares of any repurchases in the future.

Collaboration Agreements - Schedule of Contract Balances, IO Collaboration (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 345.4	$ 226.4
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Accounts receivable	8.2	77.9
Deferred revenue	$ 602.0	$ 289.9

Statement of Cash Flows - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Accrued capital expenditures	$ 100.5		$ 40.5		$ 100.5	$ 40.5	$ 54.5	$ 41.8
Cost of Treasury stock shares received	48.7	$ 54.0	$ 42.6	$ 37.6
Sanofi Collaboration Agreement, Immuno-oncology
Condensed Cash Flow Statements, Captions [Line Items]
Cost of Treasury stock shares received	$ 29.2				$ 73.3	$ 75.8
Libtayo \| Sanofi Collaboration Agreement, Immuno-oncology
Condensed Cash Flow Statements, Captions [Line Items]
Treasury stock, shares acquired	69,143				210,733	215,387

Product Sales - Schedule of Concentration of Risk, by Risk Factor (Details) - Gross Sales Revenue - Customer concentration risk	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Besse Medical, a subsidiary of AmerisourceBergen Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	57.00%	57.00%	57.00%	56.00%
McKesson Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	34.00%	36.00%	33.00%	37.00%

Fair Value Measurements

9 Months Ended

Sep. 30, 2019

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 September 30, 2019	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	$	3,907.0	—		$	3,907.0
U.S. government and government agency obligations	66.0		—		66.0
Sovereign bonds	27.4		—		27.4
Commercial paper	108.8		—		108.8
Certificates of deposit	66.8		—		66.8
Equity securities (unrestricted)	46.9		$	46.9	—
Equity securities (restricted)	382.8		49.3		333.5
	$	4,605.7	$	96.2	$	4,509.5

As of December 31, 2018
Available-for-sale debt securities:
Corporate bonds	$	2,718.4	—		$	2,718.4
U.S. government and government agency obligations	109.4		—		109.4
Sovereign bonds	7.6		—		7.6
Commercial paper	113.8		—		113.8
Certificates of deposit	60.0		—		60.0
Equity securities (unrestricted)	43.6		$	43.6	—
Equity securities (restricted)	44.4		—		44.4
	$	3,097.2	$	43.6	$	3,053.6

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 held certain restricted equity securities as of September 30, 2019, including its investment in Alnylam (see Note 3), which are subject to transfer restrictions that expire at various dates through 2023.

During the three and nine months ended September 30, 2019, we recorded $15.7 million of net unrealized gains and $58.4 million of net unrealized losses, respectively, on equity securities in Other income (expense), net. During the three and nine months ended September 30, 2018, we recorded $4.9 million of net unrealized losses and $21.0 million of net unrealized gains, respectively, on equity securities in Other income (expense), net.

As of September 30, 2019 and December 31, 2018, the Company had $43.1 million and $45.5 million, respectively, in equity investments that do not have a readily determinable fair value. These investments are recorded 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

Collaboration Agreements - Schedule of Significant Changes in Deferred Revenue Balances, Teva Collaboration (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Teva
Disaggregation of Revenue [Line Items]
Revenue recognized that was included in deferred revenue at the beginning of the period	$ (68.7)

Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	$ 4,176.0	$ 3,009.2
Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	96.2	43.6
Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	4,509.5	3,053.6
Unrestricted \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	46.9	43.6
Unrestricted \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Restricted \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	49.3	0.0
Restricted \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	333.5	44.4
Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	4,605.7	3,097.2
Estimate of Fair Value Measurement \| Unrestricted \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	46.9	43.6
Estimate of Fair Value Measurement \| Restricted \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	382.8	44.4
Corporate bonds \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0.0	0.0
Corporate bonds \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	3,907.0	2,718.4
Corporate bonds \| Unrestricted
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	3,907.0	2,718.4
Corporate bonds \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	3,907.0	2,718.4
U.S. government and government agency obligations \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0.0	0.0
U.S. government and government agency obligations \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	66.0	109.4
U.S. government and government agency obligations \| Unrestricted
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	66.0	109.4
U.S. government and government agency obligations \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	66.0	109.4
Sovereign bonds \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0.0	0.0
Sovereign bonds \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	27.4	7.6
Sovereign bonds \| Unrestricted
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	27.4	7.6
Sovereign bonds \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	27.4	7.6
Commercial paper \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0.0	0.0
Commercial paper \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	108.8	113.8
Commercial paper \| Unrestricted
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	108.8	113.8
Commercial paper \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	108.8	113.8
Certificates of deposit \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0.0	0.0
Certificates of deposit \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	66.8	60.0
Certificates of deposit \| Unrestricted
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	66.8	60.0
Certificates of deposit \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	$ 66.8	$ 60.0