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Deferred Revenue (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]



	As of December 31,
	2019		2018
Accounts receivable	$	272.7	$	138.2
Deferred revenue	$	337.2	$	236.1

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase due to shipments of commercial supplies to Sanofi	$	335.7
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(240.4	)

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



	As of December 31,
	2019		2018
Accounts receivable (recorded within Prepaid expenses and other current assets)	$	21.2	$	28.8
Deferred revenue	$	114.4	$	194.5

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(82.1	)

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



	As of December 31,
	2019			2018
Accounts receivable, net	$	(16.7	)	$	77.9
Deferred revenue	$	568.0		$	289.9

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement	$	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(92.7	)
Revenue recognized that was added to deferred revenue during the period	$	(48.4	)

Deferred revenue consists of the following:



	As of December 31,
	2019		2018
Current portion:
Received or receivable from Sanofi (see Note 3a)	$	395.5	$	246.7
Received or receivable from Bayer (see Note 3b)	49.2		44.4
Received or receivable from Teva (see Note 3c)	89.5		92.5
Other	57.5		68.9
	$	591.7	$	452.5
Noncurrent portion:
Received or receivable from Sanofi (see Note 3a)	$	509.7	$	279.3
Received or receivable from Bayer (see Note 3b)	73.8		45.1
Received or receivable from Teva (see Note 3c)	24.9		102.0
Other	10.6		37.8
	$	619.0	$	464.2

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 1,617.8	$ 1,467.7
Marketable securities	1,596.5	1,342.2
Accounts receivable - trade, net	2,100.0	1,723.7
Accounts receivable from Sanofi	260.6	226.4
Accounts receivable from Bayer	311.6	293.1
Inventories	1,415.5	1,151.2
Prepaid expenses and other current assets	387.1	243.3
Total current assets	7,689.1	6,447.6
Marketable securities	3,256.8	1,755.0
Property, plant, and equipment, net	2,890.4
Property, plant, and equipment, net		2,575.8
Deferred tax assets	824.2	828.7
Other noncurrent assets	144.7	127.4
Total assets	14,805.2	11,734.5
Current liabilities:
Accounts payable	418.1	218.2
Accrued expenses and other current liabilities	1,086.8	772.1
Deferred revenue, current	591.7	452.5
Total current liabilities	2,096.6	1,442.8
Finance lease liabilities	713.9
Finance lease liabilities		708.5
Deferred revenue, noncurrent	619.0	464.2
Other noncurrent liabilities	286.0	361.7
Total liabilities	3,715.5	2,977.2
Commitments and contingencies
Stockholders' equity:
Preferred Stock, $.01 par value; 30,000,000 shares authorized; issued and outstanding - none	0.0	0.0
Additional paid-in capital	4,428.6	3,911.6
Retained earnings	7,379.8	5,254.3
Accumulated other comprehensive income (loss)	21.1	(12.3)
Treasury Stock, at cost; 4,860,123 shares in 2019 and 3,990,021 shares in 2018	(739.9)	(396.4)
Total stockholders' equity	11,089.7	8,757.3
Total liabilities and stockholders' equity	14,805.2	11,734.5
Class A Stock
Stockholders' equity:
Common stock	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	395.5	246.7
Deferred revenue, noncurrent	509.7	279.3
Other
Current liabilities:
Deferred revenue, current	196.2	205.8
Deferred revenue, noncurrent	$ 109.3	$ 184.9

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 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, 2016					(3.8)	1.9	107.9
Beginning Balance at Dec. 31, 2016	$ 4,449.3	$ 3,030.0	$ 1,748.2	$ (12.8)	$ (316.2)		$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)							2.4
Issuance of Common Stock for equity awards granted under long-term incentive plans	240.6	240.6
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)							(0.8)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(301.7)	(301.7)
Issuance/distribution of Common Stock for 401(k) Savings Plan	19.4	19.4
Stock-based compensation charges	524.6	524.6
Net income	1,198.5		1,198.5
Other comprehensive income (loss), net of tax	13.4			13.4
Ending Balance (in shares) at Dec. 31, 2017					(3.8)	1.9	109.5
Ending Balance at Dec. 31, 2017	6,144.1	3,512.9	2,946.7	0.6	$ (316.2)		$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)							2.0
Issuance of Common Stock for equity awards granted under long-term incentive plans	114.2	114.2
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)							(0.5)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(187.2)	(187.2)
Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares)							0.1
Issuance/distribution of Common Stock for 401(k) Savings Plan	26.9	26.9
Stock-based compensation charges	444.8	444.8
Net income	2,444.4		2,444.4
Other comprehensive income (loss), net of tax	(6.3)			(6.3)
Repurchases of Common Stock (in shares)					(0.2)
Repurchases of Common Stock	(80.2)				$ (80.2)
Ending Balance (in shares) at Dec. 31, 2018					(4.0)	1.9	111.1
Ending Balance at Dec. 31, 2018	8,757.3	3,911.6	5,254.3	(12.3)	$ (396.4)		$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)							2.6
Issuance of Common Stock for equity awards granted under long-term incentive plans	213.2	213.2
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)							(0.5)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(188.0)	(188.0)
Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares)					0.1
Issuance/distribution of Common Stock for 401(k) Savings Plan	38.1	24.9			$ 13.2
Stock-based compensation charges	466.9	466.9
Net income	2,115.8		2,115.8
Other comprehensive income (loss), net of tax	33.4			33.4
Repurchases of Common Stock (in shares)					(1.0)
Repurchases of Common Stock	(356.7)				$ (356.7)
Conversion of Class A Stock to Common Stock						0.1	0.1
Ending Balance (in shares) at Dec. 31, 2019					(4.9)	1.8	113.3
Ending Balance at Dec. 31, 2019	$ 11,089.7	$ 4,428.6	$ 7,379.8	$ 21.1	$ (739.9)		$ 0.1

Collaboration and License Agreements - Sanofi, Immuno-Oncology Narrative (Details) - Sanofi Collaboration Agreement, Immuno-oncology - USD ($)		1 Months Ended		12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015
Disaggregation of Revenue [Line Items]
Excess share of profit not required to to be applied to reimburse development cost						10.00%
Contingent reimbursement obligation				$ 75,000,000
Maximum shares the collaborator could sell (in shares)				1,400,000
Number of shares the collaborator available to sell (in shares)				869,828
Amount related to obligation to pay gross profits sharing				$ 78,200,000
Upfront payment made			$ 20,000,000.0
Remaining performance obligation				1,138,000,000
IO Discovery Agreement
Disaggregation of Revenue [Line Items]
Up-front payment received						$ 265,000,000.0
Potential future R&D expenses						1,090,000,000.000
Maximum funding amount of research activities to be reimbursed per agreement						$ 825,000,000.0
License agreement term						5 years
Additional years to extend the agreement						3 years
Amended IO Discovery Agreement
Disaggregation of Revenue [Line Items]
Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement				$ 415,900,000	$ 135,000,000.0
BCMAxCD3 Program
Disaggregation of Revenue [Line Items]
Aggregate payment received with regards to amendment					461,900,000
Expenditure costs cap	$ 70,000,000.0
MUC16xCD3 Program
Disaggregation of Revenue [Line Items]
Expenditure costs cap	50,000,000.0
Potential maximum expenditure	70,000,000.0				$ 70,000,000.0
Optional payment to increase development cost funding	$ 20,000,000.0
IO Agreement
Disaggregation of Revenue [Line Items]
Up-front payment received						$ 640,000,000.0
IO License and Collaboration Agreement
Disaggregation of Revenue [Line Items]
Up-front payment received						$ 375,000,000.0
Excess share of profit not required to to be applied to reimburse development cost						10.00%
Maximum amount of sales milestone payments if total sales achieve specific levels		$ 375,000,000.0
Period of notice to opt out of further development and or commercialization				12 months
IO License and Collaboration Agreement \| PD-1
Disaggregation of Revenue [Line Items]
Levels of twelve month sales at which sales milestone payments would be received		$ 2,000,000,000.0
Through December 31, 2023 \| Libtayo
Disaggregation of Revenue [Line Items]
Percentage of royalties to be paid			8.00%
January 1, 2024 Through December 31, 2026 \| Libtayo
Disaggregation of Revenue [Line Items]
Percentage of royalties to be paid			2.50%

Credit Facility (Details) - Line of credit - USD ($)	1 Months Ended
Credit Facility (Details) - Line of credit - USD ($)	Dec. 31, 2018	Dec. 31, 2019
Prior Credit Agreement
Debt Instrument [Line Items]
Borrowings outstanding	$ 0
Senior unsecured revolving credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 750,000,000.0
Line of credit facility, expiration period	5 years
Borrowings outstanding		$ 0
Increase Limit	$ 250,000,000.0
Letters of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000.0

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Product Sales

12 Months Ended

Dec. 31, 2019

Revenues [Abstract]

Product Sales

Net product sales consist of the following:



	Year Ended December 31,
Net Product Sales in the United States	2019		2018		2017
EYLEA	$	4,644.2	$	4,076.7	$	3,701.9
Libtayo	175.7		14.8		—
ARCALYST	14.5		14.7		16.6
	$	4,834.4	$	4,106.2	$	3,718.5

The Company had product sales to certain customers that accounted for more than 10% of total gross product revenue for each of the years ended December 31, 2019, 2018, and 2017. Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows:



	Year Ended December 31,
	2019		2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	57	%	56	%	51	%
McKesson Corporation	33	%	36	%	29	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		**		19	%

** Sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue during the period.

Revenue from product sales is recorded net of applicable provisions for rebates, chargebacks, and discounts, distribution-related fees, and other sales-related deductions. Accruals for chargebacks and discounts are recorded as a direct reduction to accounts receivable. Accruals for rebates, distribution-related fees, and other sales-related deductions are recorded within accrued liabilities.

The following table summarizes the provisions, and credits/payments, for sales-related deductions for the years ended December 31, 2019, 2018, and 2017.



	Rebates, Chargebacks, and Discounts			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2016	$	12.7		$	29.5		$	3.6		$	45.8
Provisions	167.8			194.1			46.4			408.3
Credits/payments	(150.6		)	(189.5		)	(28.7		)	(368.8		)
Balance as of December 31, 2017	29.9			34.1			21.3			85.3
Provisions	223.4			211.0			44.5			478.9
Credits/payments	(212.2		)	(203.1		)	(57.5		)	(472.8		)
Balance as of December 31, 2018	41.1			42.0			8.3			91.4
Provisions	423.2			242.9			61.8			727.9
Credits/payments	(384.0		)	(238.5		)	(40.7		)	(663.2		)
Balance as of December 31, 2019	$	80.3		$	46.4		$	29.4		$	156.1

Deferred Revenue

Deferred revenue consists of the following:



	As of December 31,
	2019		2018
Current portion:
Received or receivable from Sanofi (see Note 3a)	$	395.5	$	246.7
Received or receivable from Bayer (see Note 3b)	49.2		44.4
Received or receivable from Teva (see Note 3c)	89.5		92.5
Other	57.5		68.9
	$	591.7	$	452.5
Noncurrent portion:
Received or receivable from Sanofi (see Note 3a)	$	509.7	$	279.3
Received or receivable from Bayer (see Note 3b)	73.8		45.1
Received or receivable from Teva (see Note 3c)	24.9		102.0
Other	10.6		37.8
	$	619.0	$	464.2

Inventories - Schedule of Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 216.3	$ 226.8
Work-in-process	727.7	571.1
Finished goods	70.6	24.4
Deferred costs	400.9	328.9
Total Inventories	$ 1,415.5	$ 1,151.2

Commitments and Contingencies - Analysis of lease liability maturities (Details) $ in Millions	Dec. 31, 2019 USD ($)
Operating Leases
2020	$ 7.6
2021	6.6
2022	3.3
2023	2.0
2024	2.3
Thereafter	4.3
Total undiscounted lease payments	26.1
Imputed interest	(2.5)
Debt financing costs	0.0
Total operating lease liabilities	23.6
Finance Leases
2020	22.2
2021	21.9
2022	725.4
2023	0.0
2024	0.0
Thereafter	0.0
Total undiscounted lease payments	769.5
Imputed interest	(50.1)
Debt financing costs	(5.5)
Total finance lease liabilities	$ 713.9

Collaboration and License Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 2,169.5	$ 2,048.4	$ 1,933.7	$ 1,711.8	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 7,863.4	$ 6,710.8	$ 5,872.2
Product and service, other \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									1,172.1	559.0	553.7
Product and service, other \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues									254.7	552.1	323.5
Product and service, other \| Sanofi
Disaggregation of Revenue [Line Items]
Revenues									1,426.8	1,111.1	877.2
Reimbursement of research and development expenses \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									277.7	265.3	508.4
Reimbursement of research and development expenses \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues									163.0	311.8	240.0
Reimbursement of commercialization-related expenses \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									479.9	417.2	368.8
Reimbursement of commercialization-related expenses \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues									10.3	8.9	7.0
Reimbursement for manufacturing of commercial supplies \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									206.7	127.6	35.1
Regeneron's share of profits (losses) in connection with commercialization of antibodies \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									209.3	(227.0)	(442.6)
Amounts recognized in connection with up-front payments received \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues									92.7	243.8	80.0
Other \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Revenues									(1.5)	(24.1)	84.0
Other \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenues									$ (11.3)	$ (12.4)	$ (3.5)

Deferred Revenue

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Deferred Revenue

Product Sales

Net product sales consist of the following:



	Year Ended December 31,
Net Product Sales in the United States	2019		2018		2017
EYLEA	$	4,644.2	$	4,076.7	$	3,701.9
Libtayo	175.7		14.8		—
ARCALYST	14.5		14.7		16.6
	$	4,834.4	$	4,106.2	$	3,718.5



	Year Ended December 31,
	2019		2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	57	%	56	%	51	%
McKesson Corporation	33	%	36	%	29	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		**		19	%

** Sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue during the period.

The following table summarizes the provisions, and credits/payments, for sales-related deductions for the years ended December 31, 2019, 2018, and 2017.



	Rebates, Chargebacks, and Discounts			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2016	$	12.7		$	29.5		$	3.6		$	45.8
Provisions	167.8			194.1			46.4			408.3
Credits/payments	(150.6		)	(189.5		)	(28.7		)	(368.8		)
Balance as of December 31, 2017	29.9			34.1			21.3			85.3
Provisions	223.4			211.0			44.5			478.9
Credits/payments	(212.2		)	(203.1		)	(57.5		)	(472.8		)
Balance as of December 31, 2018	41.1			42.0			8.3			91.4
Provisions	423.2			242.9			61.8			727.9
Credits/payments	(384.0		)	(238.5		)	(40.7		)	(663.2		)
Balance as of December 31, 2019	$	80.3		$	46.4		$	29.4		$	156.1

Deferred Revenue

Deferred revenue consists of the following:



	As of December 31,
	2019		2018
Current portion:
Received or receivable from Sanofi (see Note 3a)	$	395.5	$	246.7
Received or receivable from Bayer (see Note 3b)	49.2		44.4
Received or receivable from Teva (see Note 3c)	89.5		92.5
Other	57.5		68.9
	$	591.7	$	452.5
Noncurrent portion:
Received or receivable from Sanofi (see Note 3a)	$	509.7	$	279.3
Received or receivable from Bayer (see Note 3b)	73.8		45.1
Received or receivable from Teva (see Note 3c)	24.9		102.0
Other	10.6		37.8
	$	619.0	$	464.2

Long-Term Incentive Plans - Summary of weighted-average exercise prices and weighted-average grant-date fair values of options issued (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options Granted (in shares)	3,271,222,000	4,665,320,000	4,235,015,000
Weighted-Average Exercise Price (in dollars per share)	$ 366.65	$ 378.51	$ 383.56
Weighted-Average Fair Value (in dollars per share)	$ 100.80	$ 114.39	$ 118.70

Income Taxes - Schedule of components of income tax expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 444.6	$ 223.7	$ 560.3
State	1.9	4.8	(4.1)
Foreign	(2.6)	20.6	4.8
Total current tax expense	443.9	249.1	561.0
Deferred:
Federal	(132.0)	687.6	317.1
State	(1.7)	(1.9)	(1.3)
Foreign	3.1	(825.7)	3.2
Total deferred tax (benefit) expense	(130.6)	(140.0)	319.0
Total income tax expense (benefit)	$ 313.3	$ 109.1	$ 880.0

Stockholders' Equity (Details)	12 Months Ended
Stockholders' Equity (Details)	Dec. 31, 2019 USD ($) vote $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2007 demand_right shares	Nov. 30, 2019 USD ($)
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	30,000,000	30,000,000
Stock repurchase program, authorized amount \| $				$ 1,000,000,000.0
Treasury stock, shares acquired (in shares)	722,596
Cost of treasury stock shares received \| $	$ 254,000,000.0
Number of demand rights to require the company to conduct registered underwritten public offering \| demand_right			3
Class A Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Number of votes per share \| vote	10
Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	320,000,000	320,000,000
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001	$ 0.001
Number of votes per share \| vote	1
Sanofi
Class of Stock [Line Items]
Number of shares of common stock purchased (in shares)			12,000,000
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions	30.00%
Percentage of outstanding shares or voting rights under amended investor agreement	20.00%
Percentage of outstanding shares that the Company is required to appoint an individual agreed upon by the Company and the Collaborator to the Company's board of directors	20.00%
Sanofi Collaboration Agreement, Immuno-oncology
Class of Stock [Line Items]
Treasury stock, shares acquired (in shares)	210,733	215,387
Cost of treasury stock shares received \| $	$ 73,300,000	$ 75,800,000
Maximum shares the collaborator could sell (in shares)	1,400,000
Number of shares the collaborator available to sell (in shares)	869,828
Bayer
Class of Stock [Line Items]
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions	20.00%
Teva
Class of Stock [Line Items]
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions	5.00%

Collaboration and License Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, IO Collaboration (Details) - Sanofi Collaboration Agreement, Immuno-oncology - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ (16.7)	$ 77.9
Deferred revenue	$ 568.0	$ 289.9

Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 3,812.8	$ 3,304.5
Less, accumulated depreciation and amortization	(922.4)	(728.7)
Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization	2,890.4
Property, plant, and equipment, net		2,575.8
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	230.8	199.0
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	1,683.4	1,507.2
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	97.6	97.0
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	644.8	469.6
Laboratory and other equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	850.7	773.7
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	183.7	145.8
Furniture, office equipment, and other
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 121.8	$ 112.2

Statement of Cash Flows

12 Months Ended

Dec. 31, 2019

Supplemental Cash Flow Information [Abstract]

Statement of Cash Flows

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



	December 31,
	2019		2018		2017
Cash and cash equivalents	$	1,617.8	$	1,467.7	$	812.7
Restricted cash included in Other noncurrent assets	12.5		12.5		12.5
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows	$	1,630.3	$	1,480.2	$	825.2

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 December 31, 2019, 2018, and 2017 were $133.7 million, $54.5 million, and $41.8 million, respectively, of accrued capital expenditures.

As described in Note 3, during 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 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.

During 2017, the Company recognized additional lease obligations of $201.2 million in connection with the Company's Tarrytown Lease. No additional amounts were recognized during 2018 or 2019. See Note 11.

Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 2,169.5	$ 2,048.4	$ 1,933.7	$ 1,711.8	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 7,863.4	$ 6,710.8	$ 5,872.2
Product
Disaggregation of Revenue [Line Items]
Revenues									4,834.4	4,106.2	3,718.5
United States \| EYLEA
Disaggregation of Revenue [Line Items]
Revenues									4,644.2	4,076.7	3,701.9
United States \| Libtayo
Disaggregation of Revenue [Line Items]
Revenues									175.7	14.8	0.0
United States \| ARCALYST
Disaggregation of Revenue [Line Items]
Revenues									14.5	14.7	16.6
United States \| Product
Disaggregation of Revenue [Line Items]
Revenues									$ 4,834.4	$ 4,106.2	$ 3,718.5

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Net unrealized gains (losses) on equity securities in other income (expense)	$ 118.3	$ (41.9)
Net unrealized gains on equity securities in other comprehensive income (loss)			$ 14.7
Securities without readily determinable fair value	$ 55.6	$ 45.5

Net Income Per Share

12 Months Ended

Dec. 31, 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:



	Year Ended December 31,
	2019		2018		2017
Net income - basic and diluted	$	2,115.8	$	2,444.4	$	1,198.5

(Shares in millions)
Weighted average shares - basic	109.2		107.9		106.3
Effect of dilutive securities:
Stock options	5.4		6.9		9.1
Restricted stock	—		—		0.5
Weighted average shares - diluted	114.6		114.8		115.9

Net income per share - basic	$	19.38	$	22.65	$	11.27
Net income per share - diluted	$	18.46	$	21.29	$	10.34

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



	Year Ended December 31,
(Shares in millions)	2019	2018	2017
Stock options	18.4	14.9	9.2

Collaboration and License Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, Antibody Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 260.6	$ 226.4
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Accounts receivable	272.7	138.2
Deferred revenue	$ 337.2	$ 236.1

Collaboration and License Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 2,169.5	$ 2,048.4	$ 1,933.7	$ 1,711.8	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 7,863.4	$ 6,710.8	$ 5,872.2
Bayer \| Product and service, other
Disaggregation of Revenue [Line Items]
Revenues									1,188.8	1,076.7	938.1
Outside United States \| Bayer \| Product and service, other
Disaggregation of Revenue [Line Items]
Revenues									1,188.8	1,077.1	874.3
Outside United States \| Bayer \| Regeneron's net profit in connection with commercialization of EYLEA outside the United States
Disaggregation of Revenue [Line Items]
Revenues									1,091.4	992.3	802.3
Outside United States \| Bayer \| Reimbursement of EYLEA development expenses
Disaggregation of Revenue [Line Items]
Revenues									23.0	11.2	13.3
Outside United States \| Bayer \| Other
Disaggregation of Revenue [Line Items]
Revenues									$ 74.4	$ 73.6	$ 58.7

Legal Matters (Details) $ in Millions	Jul. 31, 2017 claim	Sep. 26, 2016 EUR (€)	Dec. 31, 2019 USD ($)	Apr. 01, 2019 claim	Feb. 25, 2019 claim	Feb. 14, 2019 claim	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Accruals for loss contingencies \| $			$ 100.0				$ 30.0
Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, damages sought, per unit produced \| €		€ 10,000
Loss contingency, damages sought \| €		€ 10,000,000.0
'165 Patent \| Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Pending claims					2
Invalid claims					2
'741 Patent \| Amgen v.s. Regeneron \| Pending Litigation
Loss Contingencies [Line Items]
Pending claims					1
'487 Patent
Loss Contingencies [Line Items]
Number of IPR filed	2
Number of claims invalidated						17
'688 Patent \| Pending Litigation
Loss Contingencies [Line Items]
Asserted claims				9

Collaboration and License Agreements - Bayer Narrative (Details) - Bayer $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Minimum advance notice required to terminate collaboration agreement	6 months
Maximum advance notice required to terminate collaboration agreement	12 months
Percentage of repayment of development balance out of profits	50.00%
Contingent reimbursement obligation	$ 270
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%

Product Sales - Schedule of Sales Related Deductions Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 91.4	$ 85.3	$ 45.8
Provisions	727.9	478.9	408.3
Credits/payments	(663.2)	(472.8)	(368.8)
Ending Balance	156.1	91.4	85.3
Rebates, Chargebacks, and Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	41.1	29.9	12.7
Provisions	423.2	223.4	167.8
Credits/payments	(384.0)	(212.2)	(150.6)
Ending Balance	80.3	41.1	29.9
Distribution- Related Fees
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	42.0	34.1	29.5
Provisions	242.9	211.0	194.1
Credits/payments	(238.5)	(203.1)	(189.5)
Ending Balance	46.4	42.0	34.1
Other Sales- Related Deductions
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	8.3	21.3	3.6
Provisions	61.8	44.5	46.4
Credits/payments	(40.7)	(57.5)	(28.7)
Ending Balance	$ 29.4	$ 8.3	$ 21.3

Marketable Securities - Schedule of Debt Securities Based on Contractual Maturity Dates (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Maturities within one year	$ 1,596.5	$ 1,342.2
Maturities after one year through five years	2,638.0	1,667.0
Total	$ 4,234.5	$ 3,009.2

Deferred Revenue - Schedule of deferred revenue (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current portion:
Deferred revenue, current	$ 591.7	$ 452.5
Noncurrent portion:
Deferred revenue, noncurrent	619.0	464.2
Sanofi
Current portion:
Deferred revenue, current	395.5	246.7
Noncurrent portion:
Deferred revenue, noncurrent	509.7	279.3
Bayer
Current portion:
Deferred revenue, current	49.2	44.4
Noncurrent portion:
Deferred revenue, noncurrent	73.8	45.1
Teva
Current portion:
Deferred revenue, current	89.5	92.5
Noncurrent portion:
Deferred revenue, noncurrent	24.9	102.0
Other
Current portion:
Deferred revenue, current	57.5	68.9
Noncurrent portion:
Deferred revenue, noncurrent	$ 10.6	$ 37.8

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity The Company's Restated Certificate of Incorporation, as amended, provides for the issuance of up to 40 million shares of Class A Stock, par value $0.001 per share, and 320 million shares of Common Stock, par value $0.001 per share. Shares of Class A Stock are convertible, at any time, at the option of the holder into shares of Common Stock on a share-for-share basis. Holders of Class A Stock have rights and privileges identical to Common Stockholders except that each share of Class A is entitled to ten votes per share, while each share of Common Stock is entitled to one vote per share. Class A Stock may only be transferred to specified Permitted Transferees, as defined. Under the Company's Restated Certificate of Incorporation, the Company's board of directors is authorized to issue up to 30 million shares of Preferred Stock, in series, with rights, privileges, and qualifications of each series determined by the board of directors. 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. During 2019, we repurchased 722,596 shares of Common Stock under the program and recorded the cost of the shares received, or $254.0 million, as Treasury Stock. There can be no assurance as to the timing or number of shares of any repurchases in the future. Arrangements with Collaborators In 2007, Sanofi purchased 12 million newly issued, unregistered shares of the Company's Common Stock. As a condition to the closing of this transaction, Sanofi entered into an investor agreement, as amended and restated, with the Company. Under the terms of the amended and restated investor agreement, Sanofi has three demand rights to require the Company to use all reasonable efforts to conduct a registered underwritten public offering with respect to shares of the Company's Common Stock held by Sanofi from time to time. Under the amended and restated investor agreement, Sanofi has also agreed not to dispose of any shares of the Company's Common Stock beneficially owned by Sanofi from time to time until December 20, 2020 (subject to the limited waiver described below). These restrictions on dispositions are subject to earlier termination upon the occurrence of certain events, such as the consummation of a change-of-control transaction involving the Company or the Company's dissolution or liquidation, and certain restrictions have been imposed on the manner of sales thereafter. As described in Note 3, effective January 7, 2018, the Company and Sanofi entered into a Letter Agreement, which, among other things, amended certain provisions of the amended and restated investor agreement. Pursuant to the Letter Agreement, the Company has granted Sanofi a limited waiver of the lock-up obligations under the investor agreement to allow Sanofi to sell up to an aggregate of 1,400,000 shares (of which 869,828 shares remain available to be sold as of December 31, 2019) of the Company's Common Stock held by Sanofi through September 30, 2020. Further, pursuant to the amended and restated investor agreement, Sanofi is bound by certain "standstill" provisions, which contractually prohibit Sanofi from seeking to directly or indirectly exert control of the Company or acquiring more than 30% of the outstanding shares of the Company's Class A Stock and Common Stock (taken together). This prohibition will remain in place until the earliest of (i) the later of the fifth anniversaries of the expiration or earlier termination of the Company's License and Collaboration Agreement with Sanofi and the Company's ZALTRAP Agreement with Sanofi, each as amended, and (ii) other specified events. Sanofi has also agreed to vote as recommended by the Company's board of directors, except that it may elect to vote proportionally with the votes cast by all of the Company's other shareholders with respect to certain change-of-control transactions, and to vote in its sole discretion with respect to liquidation or dissolution, stock issuances equal to or exceeding 20% of the outstanding shares or voting rights of the Company's Class A Stock and Common Stock (taken together), and new equity compensation plans or amendments if not materially consistent with the Company's historical equity compensation practices. The rights and restrictions under the investor agreement are subject to termination upon the occurrence of certain events. In addition, upon Sanofi reaching 20% ownership of the Company's outstanding shares of Class A Stock and Common Stock (taken together) during 2014, the Company was required to appoint an individual agreed upon by the Company and Sanofi to the Company's board of directors. This individual is required to be independent of the Company, and not to be a current or former officer, director, employee, or paid consultant of Sanofi. Subject to certain exceptions, the Company is required to use its reasonable efforts (including recommending that its shareholders vote in favor) to cause the election of this designee at the Company's annual shareholder meetings for so long as (other than during the term of the Letter Agreement) Sanofi maintains a specified equity interest in the Company. In connection with the Company's license and collaboration agreements with Bayer for the joint development and commercialization outside the United States of antibody product candidates to PDGFR-beta and Ang2, Bayer is bound by certain "standstill" provisions, which contractually prohibit Bayer from seeking to influence the control of the Company or acquiring more than 20% of the Company's outstanding shares of Class A Stock and Common Stock (taken together). With respect to each of these agreements, this prohibition will remain in place until the earliest of (i) the fifth anniversary of the expiration or earlier termination of the agreement (which, in the case of the PDGFR-beta license and collaboration agreement, occurred on July 31, 2017, and, in the case of the Ang2 agreement, occurred on November 1, 2018) or (ii) other specified events. Further, pursuant to the 2016 Teva Collaboration Agreement, Teva and its affiliates are bound by certain "standstill" provisions, which contractually prohibit them from seeking to directly or indirectly exert control of the Company or acquiring more than 5% of the Company's Class A Stock and Common Stock (taken together). This prohibition will remain in place until the earliest of (i) the fifth anniversary of the expiration or earlier termination of the agreement or (ii) other specified events.

Long-Term Incentive Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of awards	10 years
Total intrinsic value - of stock options exercised	$ 558.9	$ 510.6	$ 735.6
Expected dividend yield	0.00%	0.00%	0.00%
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Non-performance based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 422.8	$ 421.8	$ 492.8
Capitalized to inventory	2.4	17.1	16.8
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 521.9
Weighted average period for recognition of total unrecognized compensation expense (in years)	1 year 10 months 24 days
Phantom stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period within vesting date that awards may be received	30 days
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 41.5	$ 5.6	$ 14.5
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 274.6
Weighted average period for recognition of total unrecognized compensation expense (in years)	3 years 4 months 24 days
Amended & Restated Long-Term Incentive Plan 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares registered (in shares)			12,000,000
Number of shares authorized for issuance (in shares)			18,559,431
Long-Term Incentive Plan 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grants (in shares)	9,546,628
Long-Term Incentive Plan 2000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grants (in shares)	0

Label	Element	Value
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 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 2014-09 And 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(143,400,000)
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	$ (136,800,000)

Collaboration and License Agreements - Sanofi, Antibody Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Disaggregation of Revenue [Line Items]
Research and development		$ 3,036,600,000	$ 2,186,100,000	$ 2,075,100,000
Treasury stock, shares acquired (in shares)		722,596
Cost of treasury stock shares received		$ 254,000,000.0
Sanofi
Disaggregation of Revenue [Line Items]
Common stock, shares issued (in shares)	23,350,365	23,350,365
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Proceeds from collaborators				85,000,000.0
Annual funding maximum of research activities per amended agreement				130,000,000.0
Percentage of Trial Costs borne by collaborating party		80.00%
Percentage of Trial Costs borne by entity		20.00%
Percentage of repayment of development balance out of profits		50.00%
Percentage of trial costs to be reimbursed due to profitability of agreement		30.00%
Excess share of profit not required to to be applied to reimburse development cost		10.00%
Contingent reimbursement obligation	$ 2,990,000,000	$ 2,990,000,000
Treasury stock, shares acquired (in shares)		93,286
Cost of treasury stock shares received		$ 29,400,000
Starting share of profits outside the United States, based on sales, for collaborating party		65.00%
Starting share of profits outside the United States, based on sales, for Company		35.00%
Ending share of profits outside the United States, based on sales, for collaborating party		55.00%
Ending share of profits outside the United States, based on sales, for Company		45.00%
Share of losses outside the United States, for collaborating party		55.00%
Share of losses outside the United States, for Company		45.00%
Maximum amount of sales milestone payments if total sales achieve specific levels		$ 250,000,000.0
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
Period of notice to opt out of further development and or commercialization		12 months
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Excess share of profit not required to to be applied to reimburse development cost					10.00%
Contingent reimbursement obligation	75,000,000	$ 75,000,000
Treasury stock, shares acquired (in shares)		210,733	215,387
Cost of treasury stock shares received		$ 73,300,000	$ 75,800,000
Praluent, Kevzara, and Dupixent \| Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Research and development		$ 46,000,000.0	$ 47,700,000	$ 91,800,000
Employee severance costs \| Sanofi
Disaggregation of Revenue [Line Items]
Restructuring-related costs	$ 35,200,000

Long-Term Incentive Plans - Summary of activity related to restricted stock awards (Details) - Restricted stock	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Number of Shares/Units
Beginning balance (in shares) \| shares	472,630
Granted (in shares) \| shares	698,103
Vested (in shares) \| shares	(3,090)
Forfeited/Cancelled (in shares) \| shares	(5,857)
Ending balance (in shares) \| shares	1,161,786
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars of shares) \| $ / shares	$ 386.10
Granted (in dollars of shares) \| $ / shares	356.33
Vested (in dollars of shares) \| $ / shares	406.65
Forfeited/Cancelled (in dollars of shares) \| $ / shares	385.90
Ending balance (in dollars of shares) \| $ / shares	$ 368.16

Income Taxes - Schedule of unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	$ 189.5	$ 146.2	$ 117.2
Gross increases related to current year tax positions	37.9	51.4	49.0
Gross increases related to prior year tax positions		5.6
Gross decreases related to prior year tax positions	(7.2)		(5.6)
Gross decreases due to settlements and lapse of statutes of limitations	(9.4)	(13.7)	(14.4)
Balance as of December 31	$ 210.8	$ 189.5	$ 146.2

Property, Plant, and Equipment

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, Plant, and Equipment

Property, plant, and equipment consists of the following:



	As of December 31,
	2019			2018
Land	$	230.8		$	199.0
Building and improvements	1,683.4			1,507.2
Leasehold improvements	97.6			97.0
Construction in progress	644.8			469.6
Laboratory equipment	850.7			773.7
Computer equipment and software	183.7			145.8
Furniture, office equipment, and other	121.8			112.2
	3,812.8			3,304.5
Less, accumulated depreciation and amortization	(922.4		)	(728.7		)
	$	2,890.4		$	2,575.8

Property, plant, and equipment in the table above includes leased property under the Company's finance lease at its Tarrytown, New York facility. See Note 11.

Depreciation and amortization expense (including as it relates to the Company's finance lease) on property, plant, and equipment amounted to $205.2 million, $144.1 million, and $142.2 million for the years ended December 31, 2019, 2018, and 2017, respectively.

As of December 31, 2019 and 2018, $2,117.6 million and $1,813.8 million, respectively, of the Company's net property, plant, and equipment was located in the United States and $772.8 million and $762.0 million, respectively, was located in Europe (primarily in Ireland).

Employee Savings Plans (Details) - USD ($) $ in Millions	12 Months Ended
Employee Savings Plans (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Employer contribution expense to 401(k) Savings Plan	$ 38.1	$ 27.0	$ 19.6

Commitments and Contingencies - Research Collaboration and Licensing Agreements Narrative (Details) - Agreements with Royalty Provisions - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Research Collaboration and Licensing Arrangements [Line Items]
Royalty rate minimum	0.50%
Royalty rate maximum	11.50%
Royalty expense	$ 54.2	$ 36.7	$ 30.8

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

The Company is subject to U.S. federal, state, and foreign income taxes. Components of income before income taxes consist of the following:



	Year Ended December 31,
	2019		2018		2017
United States	$	2,011.2	$	2,151.7	$	1,964.7
Foreign	417.9		401.8		113.8
	$	2,429.1	$	2,553.5	$	2,078.5

Components of income tax expense consist of the following:



	Year Ended December 31,
	2019			2018			2017
Current:
Federal	$	444.6		$	223.7		$	560.3
State	1.9			4.8			(4.1		)
Foreign	(2.6		)	20.6			4.8
Total current tax expense	443.9			249.1			561.0
Deferred:
Federal	(132.0		)	687.6			317.1
State	(1.7		)	(1.9		)	(1.3		)
Foreign	3.1			(825.7		)	3.2
Total deferred tax (benefit) expense	(130.6		)	(140.0		)	319.0
	$	313.3		$	109.1		$	880.0

A reconciliation of the U.S. statutory income tax rate to the Company's effective income tax rate is as follows:



	Year Ended December 31,
	2019		2018		2017
U.S. federal statutory tax rate	21.0	%	21.0	%	35.0	%
Income tax credits	(4.6	)	(2.6	)	(1.3	)
Stock-based compensation	(2.5	)	(2.5	)	(9.0	)
Foreign-derived intangible income deduction	(1.6	)	(1.0	)	—
Taxation of non-U.S. operations	(1.0	)	(1.9	)	0.7
Non-deductible Branded Prescription Drug Fee	0.7		0.6		1.7
Sale of non-inventory related assets between foreign subsidiaries	—		(6.3	)	—
Impact of change in U.S. corporate tax rate (the Act)	—		(2.7	)	15.7
Domestic production activities deduction	—		—		(2.6	)
Other permanent differences	0.9		(0.3	)	2.1
Effective income tax rate	12.9	%	4.3	%	42.3	%

The difference between the U.S. federal statutory rate and the Company's effective tax rate for each of the three years ended December 31, 2019, 2018, and 2017 is summarized in the table above. In 2018, the difference between the U.S. federal statutory rate of 21% and the Company's effective tax rate of 4.3% was partly attributable to the impact of the Company's sale of non-inventory related assets between foreign subsidiaries (including the associated impact of global intangible low-taxed income). In

2017, the difference between the U.S. federal statutory rate of 35% and the Company's effective tax rate of 42.3% was partly impacted by the charge related to the re-measurement of the Company's U.S. net deferred tax assets upon the enactment of the Act (see below).

In December 2017, the bill known as the "Tax Cuts and Jobs Act" (the "Act") was signed into law. The Act, which became effective with respect to most of its provisions as of January 1, 2018, significantly revised U.S. corporate income tax laws by, among other things, reducing the U.S. federal corporate income tax rate from 35% to 21%, changing the taxation of foreign earnings (including taxation of certain global intangible low-taxed income ("GILTI")), allowing for a foreign-derived intangible income deduction and immediate expensing for qualified assets, repealing the deduction for domestic manufacturing, and imposing further limitations on the deductibility of executive compensation. As a result of the Act being signed into law, the Company recognized a provisional charge of $326.2 million in the fourth quarter of 2017 related to the re-measurement of its U.S. net deferred tax assets at the lower enacted corporate tax rate. The provisional charge recorded in the fourth quarter of 2017 was an estimate, and the measurement of deferred tax assets was subject to further analysis, such as developing interpretations and clarifications of the provisions of the Act. During 2018, we recorded an income tax benefit of $68.0 million as a final adjustment to the provisional amount recorded as of December 31, 2017, which was partly attributable to our election to record deferred tax assets and liabilities for expected amounts of GILTI inclusions.

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets and liabilities are as follows:



	As of December 31,
	2019			2018
Deferred tax assets:
Deferred compensation	$	519.7		$	458.2
Fixed assets and intangible assets	192.0			107.8
Accrued expenses	75.9			53.3
Deferred revenue	22.0			20.2
Other	—			33.3
Total deferred tax assets	809.6			672.8
Valuation allowance	(7.0		)	—
Deferred tax assets, net of valuation allowance	802.6			672.8

Deferred tax liabilities:
Other	(11.2		)	(2.7		)
Net deferred tax assets	$	791.4		$	670.1

The Company's 2015 through 2018 federal income tax returns remain open to examination by the IRS. The Company's 2015 and 2016 federal income tax returns are currently under audit by the IRS. In general, the Company's state income tax returns from 2016 to 2018 remain open to examination. The United States and many states generally have statutes of limitation ranging from 3 to 5 years; however, those statutes could be extended due to the Company's tax credit carryforward position. In general, tax authorities have the ability to review income tax returns in which the statute of limitation has previously expired to adjust the tax credits generated in those years.

The following table reconciles the beginning and ending amounts of unrecognized tax benefits. The amount of unrecognized tax benefits that, if settled, would impact the effective tax rate is $210.8 million, $189.5 million, and $146.2 million as of December 31, 2019, 2018, and 2017, respectively.



	2019			2018			2017
Balance as of January 1	$	189.5		$	146.2		$	117.2
Gross increases related to current year tax positions	37.9			51.4			49.0
Gross (decreases) increases related to prior year tax positions	(7.2		)	5.6			(5.6		)
Gross decreases due to settlements and lapse of statutes of limitations	(9.4		)	(13.7		)	(14.4		)
Balance as of December 31	$	210.8		$	189.5		$	146.2

In 2019, 2018 and 2017, the increases in unrecognized tax benefits primarily related to the Company's calculation of certain tax credits and other items related to the Company's international operations.

During 2019, 2018, and 2017, interest expense related to unrecognized tax benefits recorded by the Company was not material. The Company does not believe that it is reasonably possible that the resolution of tax exposures within the next twelve months would have a material impact on its unrecognized tax benefits as of December 31, 2019.

Income Taxes - Schedule of effective income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	21.00%	21.00%	35.00%
Income tax credits	(4.60%)	(2.60%)	(1.30%)
Stock-based compensation	(2.50%)	(2.50%)	(9.00%)
Foreign-derived intangible income deduction	(1.60%)	(1.00%)	0.00%
Taxation of non-U.S. operations	(1.00%)	(1.90%)	0.70%
Non-deductible Branded Prescription Drug Fee	0.70%	0.60%	1.70%
Sale of non-inventory related assets between foreign subsidiaries	0.00%	(6.30%)	0.00%
Impact of change in U.S. corporate tax rate (the Act)	0.00%	(2.70%)	15.70%
Domestic production activities deduction	0.00%	0.00%	(2.60%)
Other permanent differences	0.90%	(0.30%)	2.10%
Effective income tax rate	12.90%	4.30%	42.30%

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:



	As of December 31,
	2019		2018
Accrued payroll and related costs	$	344.4	$	261.8
Accrued clinical expenses	142.7		142.2
Accrued sales-related charges, deductions, and royalties	249.0		182.7
Income taxes payable	49.4		20.8
Other accrued expenses and liabilities	301.3		164.6
	$	1,086.8	$	772.1

Commitments and Contingencies - Finance lease costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Amortization of right-of-use assets	$ 14.4
Interest on lease liabilities	27.6
Finance lease costs	$ 42.0

Collaboration and License Agreements - Schedule of Significant Changes in Deferred Revenue Balances, IO Collaboration (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue recognized that was included in deferred revenue at the beginning of the period	$ (294.0)	$ 194.5	$ 113.1
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenue recognized that was added to deferred revenue during the period	(48.4)
Accounting Standards Update 2014-09 \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Revenue recognized that was included in deferred revenue at the beginning of the period	(92.7)
Amended IO Discovery Agreement \| Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement	$ 415.9	$ 135.0

Net Income Per Share (Tables)

12 Months Ended

Dec. 31, 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:



	Year Ended December 31,
	2019		2018		2017
Net income - basic and diluted	$	2,115.8	$	2,444.4	$	1,198.5

(Shares in millions)
Weighted average shares - basic	109.2		107.9		106.3
Effect of dilutive securities:
Stock options	5.4		6.9		9.1
Restricted stock	—		—		0.5
Weighted average shares - diluted	114.6		114.8		115.9

Net income per share - basic	$	19.38	$	22.65	$	11.27
Net income per share - diluted	$	18.46	$	21.29	$	10.34

Antidilutive Securities

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



	Year Ended December 31,
(Shares in millions)	2019	2018	2017
Stock options	18.4	14.9	9.2

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Schedule of accrued expenses and other current liabilities

Accrued expenses and other current liabilities consist of the following:



	As of December 31,
	2019		2018
Accrued payroll and related costs	$	344.4	$	261.8
Accrued clinical expenses	142.7		142.2
Accrued sales-related charges, deductions, and royalties	249.0		182.7
Income taxes payable	49.4		20.8
Other accrued expenses and liabilities	301.3		164.6
	$	1,086.8	$	772.1

Long-Term Incentive Plans - Summary of transactions involving stock option awards (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Outstanding at beginning of period (in shares)	28,279,696,000
Granted (in shares)	3,271,222,000	4,665,320,000	4,235,015,000
Forfeited (in shares)	(576,806,000)
Expired (in shares)	(300,581,000)
Exercised (in shares)	(2,064,254,000)
Outstanding at end of period (in shares)	28,609,277,000	28,279,696,000
Vested and expected to vest (in shares)	27,524,704,000
Exercisable (in shares)	19,291,335,000
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 319.28
Granted (in dollars per share)	366.65	$ 378.51	$ 383.56
Forfeited (in dollars per share)	395.88
Expired (in dollars per share)	460.37
Exercised (in dollars per share)	103.51
Outstanding at end of period (in dollars per share)	337.24	$ 319.28
Vested and expected to vest (in dollars per share)	335.73
Exercisable (in dollars per share)	$ 318.15
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years) - outstanding	6 years 2 months 1 day
Weighted average remaining contractual term - vested and expected to vest	6 years 21 days
Weighted average remaining contractual term - exercisable	4 years 10 months 24 days
Intrinsic value - outstanding	$ 1,805.9
Intrinsic value - vested and expected to vest	1,800.5
Intrinsic value - exercisable	$ 1,763.9

Statement of Cash Flows - Narrative (Details) - USD ($)	12 Months Ended
Statement of Cash Flows - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Accrued capital expenditures	$ 133,700,000	$ 54,500,000	$ 41,800,000
Treasury stock, shares acquired (in shares)	722,596
Cost of treasury stock shares received	$ 254,000,000.0
Capital lease obligations incurred	$ 0	$ 0	$ 201,200,000
Sanofi Collaboration Agreement, Immuno-oncology
Condensed Cash Flow Statements, Captions [Line Items]
Treasury stock, shares acquired (in shares)	210,733	215,387
Cost of treasury stock shares received	$ 73,300,000	$ 75,800,000

Unaudited Quarterly Results (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Summarized quarterly financial data (unaudited) for the years ended December 31, 2019 and 2018 are set forth in the following tables.



	First Quarter Ended March 31, 2019		Second Quarter Ended June 30, 2019⁽¹⁾		Third Quarter Ended September 30, 2019		Fourth Quarter Ended December 31, 2019
Revenues	$	1,711.8	$	1,933.7	$	2,048.4	$	2,169.5
Operating expenses	$	1,231.8	$	1,618.1	$	1,309.9	$	1,493.8
Net income	$	461.1	$	193.1	$	669.6	$	792.0
Net income per share - basic	$	4.23	$	1.77	$	6.12	$	7.25
Net income per share - diluted	$	3.99	$	1.68	$	5.86	$	6.93


	First Quarter Ended March 31, 2018		Second Quarter Ended June 30, 2018		Third Quarter Ended September 30, 2018		Fourth Quarter Ended December 31, 2018⁽²⁾⁽³⁾
Revenues	$	1,511.5	$	1,608.0	$	1,663.5	$	1,927.8
Operating expenses	$	944.3	$	985.8	$	1,036.6	$	1,209.7
Net income	$	478.0	$	551.4	$	594.7	$	820.4
Net income per share - basic	$	4.44	$	5.12	$	5.50	$	7.58
Net income per share - diluted	$	4.16	$	4.82	$	5.17	$	7.15

⁽¹⁾Included in research and development expenses was a $400.0 million up-front payment in connection with the Alnylam collaboration agreement. See Note 3.
⁽²⁾ Includes impact of a cumulative catch-up adjustment recorded to revenue upon termination of the 2015 IO Discovery Agreement. See Note 3.
⁽³⁾ Includes tax impact of the sale of non-inventory related assets between foreign subsidiaries completed during the fourth quarter of 2018. See Note 15.

Cover Cover - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2019

Jan. 31, 2020

Jun. 28, 2019

Entity Information [Line Items]

Document Type

10-K

Document Annual Report

true

Document Period End Date

Dec. 31, 2019

Document Transition Report

false

Entity File Number

0-19034

Entity Registrant Name

REGENERON PHARMACEUTICALS, INC.

Entity Incorporation, State or Country Code

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

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 Well-known Seasoned Issuer

Yes

Entity Voluntary Filers

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 Public Float

$ 32,929

Documents Incorporated by Reference

DOCUMENTS INCORPORATED BY REFERENCE

Specified portions of the Registrant's definitive proxy statement to be filed in connection with solicitation of proxies for its 2020 Annual Meeting of Shareholders are incorporated by reference into Part III of this Form 10-K. Exhibit index is located on pages 76 to 81 of this filing.

Entity Central Index Key

0000872589

Current Fiscal Year End Date

--12-31

Document Fiscal Year Focus

2019

Document Fiscal Period Focus

Amendment Flag

false

Class A Stock

Entity Information [Line Items]

Entity Common Stock, Shares Outstanding

1,848,970

Common Stock

Entity Information [Line Items]

Entity Common Stock, Shares Outstanding

108,170,839

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on a recurring basis

The table below summarizes the Company's assets which are measured at fair value on a recurring basis. The following fair value hierarchy is used to classify assets, based on inputs to valuation techniques utilized to measure fair value:


•	Level 1 - Quoted prices in active markets for identical assets


•	Level 2 - Significant other observable inputs, such as 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


•	Level 3 - Significant other unobservable inputs



			Fair Value Measurements at Reporting Date
As of December 31, 2019	Fair Value		Level 1		Level 2
Available-for-sale debt securities:
Corporate bonds	$	3,988.1	—		$	3,988.1
U.S. government and government agency obligations	54.4		—		54.4
Sovereign bonds	27.3		—		27.3
Commercial paper	92.3		—		92.3
Certificates of deposit	72.4		—		72.4
Equity securities (unrestricted)	61.6		$	61.6	—
Equity securities (restricted)	557.2		557.2		—
	$	4,853.3	$	618.8	$	4,234.5

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

Employee Savings Plans	12 Months Ended
Employee Savings Plans	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Savings Plans	Employee Savings Plans The Company maintains the Regeneron Pharmaceuticals, Inc. 401(k) Savings Plan, as amended and restated (the "Savings Plan"). The terms of the Savings Plan allow U.S. employees (as defined by the Savings Plan) to contribute to the Savings Plan a percentage of their compensation. In addition, the Company may make discretionary contributions ("Contribution"), as defined, to the accounts of participants under the Savings Plan. The Company recognized $38.1 million, $27.0 million, and $19.6 million of Contribution expense in 2019, 2018, and 2017, respectively. The Company also maintains additional employee savings plans outside of the United States, which cover eligible employees. Expenses recognized by the Company related to contributions to such plans were not material during 2019, 2018, and 2017.

Commitments and Contingencies - Other information related to finance lease (Details)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Remaining lease term (in years)	2 years 2 months 1 day
Discount rate	3.05%

Unaudited Quarterly Results - Schedule of unaudited quarterly results (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 2,169.5	$ 2,048.4	$ 1,933.7	$ 1,711.8	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 7,863.4	$ 6,710.8	$ 5,872.2
Operating expenses	1,493.8	1,309.9	1,618.1	1,231.8	1,209.7	1,036.6	985.8	944.3	5,653.6	4,176.4	3,792.6
Net income	$ 792.0	$ 669.6	$ 193.1	$ 461.1	$ 820.4	$ 594.7	$ 551.4	$ 478.0	$ 2,115.8	$ 2,444.4	$ 1,198.5
Net income per share - basic (in dollars per share)	$ 7.25	$ 6.12	$ 1.77	$ 4.23	$ 7.58	$ 5.50	$ 5.12	$ 4.44	$ 19.38	$ 22.65	$ 11.27
Net income per share - diluted (in dollars per shares)	$ 6.93	$ 5.86	$ 1.68	$ 3.99	$ 7.15	$ 5.17	$ 4.82	$ 4.16	$ 18.46	$ 21.29	$ 10.34
Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Upfront payment made			$ 400.0

- 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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- Definition

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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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

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Liabilities and Equity [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	30,000,000	30,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Treasury stock, outstanding (in shares)	4,860,123	3,990,021
Class A Stock
Liabilities and Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	1,848,970	1,911,354
Common stock, shares outstanding (in shares)	1,848,970	1,911,354
Common Stock
Liabilities and Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	320,000,000	320,000,000
Common stock, shares issued (in shares)	113,288,103	111,084,951

Business Overview and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Business Overview and Summary of Significant Accounting Policies

Organization and Business

Regeneron Pharmaceuticals, Inc. and its subsidiaries ("Regeneron," "Company," "we," "us," and "our") is a fully integrated biotechnology company that discovers, invents, develops, manufactures, and commercializes medicines for the treatment of serious diseases. Our commercialized medicines and product candidates in development are designed to help patients with eye diseases, allergic and inflammatory diseases, cancer, cardiovascular and metabolic diseases, pain, infectious diseases, and rare diseases. The Company's products that have received marketing approval, which are currently marketed by us and/or our collaborators, consist of EYLEA^®(aflibercept), Dupixent^®(dupilumab), Libtayo^® (cemiplimab), Praluent^®(alirocumab), Kevzara^®(sarilumab), ARCALYST^®(rilonacept), and ZALTRAP^®(ziv-aflibercept). The Company is a party to collaboration agreements to develop and commercialize, as applicable, certain products and product candidates (see Note 3).

The Company operates in one business segment, which includes all activities related to the discovery, development, and commercialization of medicines for the treatment of serious diseases. The Company's business is subject to certain risks including, but not limited to, uncertainties relating to conducting pharmaceutical research, product development, obtaining regulatory approvals, market acceptance, competition, and obtaining and enforcing patents.

Basis of Presentation

The consolidated financial statements include the accounts of Regeneron and its wholly-owned subsidiaries. Intercompany balances and transactions are eliminated in consolidation. 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 11. 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 Consolidated Financial Statements. Prior period amounts have not been adjusted in connection with the adoption of this standard.

We adopted ASC 606, Revenue from Contracts with Customers, as of January 1, 2018. The Company adopted the standard using the modified retrospective method, and thus recognized a cumulative-effect adjustment to reduce Retained earnings and increase Deferred revenue on January 1, 2018 by $143.4 million, net of tax. Prior period amounts were not adjusted in connection with the adoption of this standard. We also adopted Accounting Standards Update ("ASU") 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, as of January 1, 2018. The Company recognized a cumulative-effect adjustment, related to unrealized gains on equity securities, to reduce Accumulated other comprehensive income and increase Retained earnings on January 1, 2018 by $6.6 million.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Concentration of Credit Risk

Financial instruments which potentially expose the Company to concentrations of credit risk consist of cash, cash equivalents, certain investments, and accounts receivable. In accordance with the Company's policies, the Company mandates asset diversification and monitors exposure with its counterparties.

Concentrations of credit risk with respect to accounts receivable are significant. The Company has a concentration of credit risk associated with the receivables due from its collaborators Bayer, Sanofi, and Teva. The Company is also subject to credit risk with accounts receivable from its product sales, which are due from several distributors and specialty pharmacies (the Company's customers). As of December 31, 2019 and 2018, three individual customers accounted for 97% and 99%, respectively, of the Company's net trade accounts receivable balances. The Company has contractual payment terms with each of its customers, and the Company monitors its customers' financial performance and credit worthiness so that it can properly assess and respond to any changes in their credit profile. As of December 31, 2019 and 2018, there were no reserves against trade accounts receivable. In addition, during the years ended December 31, 2019, 2018, and 2017, the Company did not recognize any charges for write-offs of trade accounts receivable.

Significant Accounting Policies

Cash and Cash Equivalents

The Company considers all highly liquid debt instruments with a maturity of three months or less when purchased to be cash equivalents. The carrying amount reported in the Consolidated Balance Sheet for cash and cash equivalents approximates its fair value.

Debt and Equity Securities

The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. We invest our cash primarily in debt securities of investment grade institutions. We consider our investments in debt securities to be "available-for-sale," as defined by authoritative guidance issued by the Financial Accounting Standards Board ("FASB"). These assets are carried at fair value and the unrealized gains and losses are included in Accumulated other comprehensive income (loss). Realized gains and losses on available-for-sale debt securities are included in Other income (expense), net.

We also have investments in equity securities that are carried at fair value with changes in fair value recognized within Other income (expense), net. We have elected to measure certain equity investments we hold that do not have readily determinable fair values at cost less impairment, if any, and adjust for observable price changes in orderly transactions for identical or similar investments of the same issuer within Other income (expense), net.

The Company reviews its portfolio of available-for-sale debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. If a decline in the fair value of an available-for-sale debt security in the Company's investment portfolio is deemed to be other-than-temporary, the Company writes down the cost basis of the security to its current fair value and recognizes a loss as a charge against income.

Accounts Receivable

The Company's trade accounts receivable arise from product sales and represent amounts due from its distributors and specialty pharmacies (collectively, the Company's trade "customers"), which are all located in the United States. In addition, the Company records accounts receivable arising from its collaboration and licensing agreements. The Company monitors the financial performance and credit worthiness of its counterparties so that it can properly assess and respond to changes in their credit profile. The Company provides reserves against receivables for estimated losses, if any, that may result from a counterparty's inability to pay. Amounts determined to be uncollectible are written-off against the reserve.

Inventories

Inventories are stated at the lower of cost or net realizable value. The Company determines the cost of inventory using the first-in, first-out, or FIFO, method.

The Company capitalizes inventory costs associated with the Company's products prior to regulatory approval when, based on management's judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed. The determination to capitalize inventory costs is based on various factors, including status and expectations of the regulatory approval process, any known safety or efficacy concerns, potential labeling restrictions, and any other impediments to obtaining regulatory approval.

The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes-down such inventories as appropriate. In addition, the Company's products are subject to strict quality control and monitoring which the Company performs throughout the manufacturing process. If certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, the Company records a charge to write down such unmarketable inventory to its estimated realizable value.

Property, Plant, and Equipment

Property, plant, and equipment are stated at cost, net of accumulated depreciation. Depreciation is calculated on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the remaining lease term. Costs of construction of certain long-lived assets include capitalized interest, which is amortized over the estimated useful life of the related asset. Expenditures for maintenance and repairs which do not materially extend the useful lives of the assets are charged to expense as incurred. The cost and accumulated depreciation or amortization of assets retired or sold are removed from the respective accounts, and any gain or loss is recognized in operations. The estimated useful lives of property, plant, and equipment are as follows:



Building and improvements		10–50 years
Laboratory and other equipment		3–10 years
Furniture and fixtures		5 years

The Company periodically assesses the recoverability of long-lived assets, such as property, plant, and equipment, and evaluates such assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

Revenue Recognition

Product Revenue

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

The Company sells its marketed products in the United States to several distributors and specialty pharmacies. Under these distribution models, the distributors and specialty pharmacies take physical delivery of product. For EYLEA and Libtayo, the distributors and specialty pharmacies sell the product directly to healthcare providers.

The amount of revenue we recognize from product sales varies due to rebates, chargebacks, and discounts provided under governmental and other programs, distribution-related fees, and other sales-related deductions. In order to determine the transaction price, we estimate, utilizing the expected value method, the amount of variable consideration that we will be entitled to. This estimate is based upon contracts with customers and government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, estimated payor mix, and other relevant factors. The Company reviews its estimates of rebates, chargebacks, and other applicable provisions each period and records any necessary adjustments in the current period's net product sales.

Rebates, Chargebacks, and Discounts: The Company estimates reductions to product sales for Medicaid and Veterans' Administration ("VA") programs as well as certain other qualifying federal and state government programs, and for other programs, including group purchasing organizations. Based upon the Company's contracts with government agencies and other organizations, statutorily-defined discounts applicable to government-funded programs, historical experience, and estimated payor mix, the Company estimates and records an allowance for rebates and chargebacks. The Company's liability for Medicaid rebates consists of estimates for claims that a state will make for a current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, and invoices received for claims from prior quarters that have not been paid. The Company's reserves related to discounted pricing to VA, Public Health Services, and others (collectively "qualified healthcare providers") represent the Company's estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices the Company charges to its customers (i.e., distributors and specialty pharmacies). The Company's customers charge the Company for the difference between what they pay for the products and the ultimate selling price to the

qualified healthcare providers. The Company's reserve for this discounted pricing is based on expected sales to qualified healthcare providers and the chargebacks that customers have already claimed.

Distribution-Related Fees: The Company has written contracts with its customers that include terms for distribution-related fees. The Company estimates and records distribution and related fees due to its customers generally based on gross sales.

Other Sales-Related Deductions: The Company estimates other sales-related deductions offered to customers based on written contracts. The Company estimates and records other sales-related deductions generally based on gross sales.

Consistent with industry practice, the Company offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product's expiration date. The Company will accept returns for three months prior to and up to six months after the product expiration date. Product returned is generally not resalable given the nature of the Company's products and method of administration. The Company develops estimates for product returns based upon historical experience, shelf life of the product, and other relevant factors. The Company monitors product supply levels in the distribution channel, as well as sales by its customers of EYLEA and Libtayo to healthcare providers and ARCALYST to patients using product-specific data provided by its customers. If necessary, the Company's estimates of product returns may be adjusted in the future based on actual returns experience, known or expected changes in the marketplace, or other factors.

Collaboration Revenue

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

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

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

At the inception of the contract, the transaction price reflects the amount of consideration we expect to be entitled to in exchange for transferring promised goods or services to our customer. In arrangements where we satisfy performance obligation(s) during the development phase over time, we recognize collaboration revenue over time typically using an input method on the basis of our research and development costs incurred relative to the total expected cost which determines the extent of our progress toward completion. We review our estimate of the transaction price and the total expected cost each period, and make revisions to such estimates as necessary. When we are entitled to reimbursement of all or a portion of the research and development expenses that we incur under a collaboration, we record those reimbursable amounts proportionately as we recognize our expenses. We recognized collaboration revenue for non-refundable up-front payments, development milestones, and payments for development activities, for which we used an input method, of $497.6 million and $837.7 million for the years ended December 31, 2019 and 2018, respectively.

If the collaboration is a cost-sharing arrangement in which both we and our collaborator perform development work and share costs, we also recognize, as research and development expense in the period when our collaborator incurs development expenses, the portion of the collaborator's development expenses that we are obligated to reimburse. Our collaborators provide us with estimated development expenses for the most recent fiscal quarter.

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

sales occur and costs are incurred by the collaborator. Our collaborators provide us with estimates of our share of the profits or losses for such quarter; these estimates are reconciled to actual results in the subsequent fiscal quarter, and our share of the profit or loss is adjusted accordingly, as necessary

In arrangements where the collaborator records product sales, the Company may be obligated to use commercially reasonable efforts to supply commercial product to its collaborators, and may be reimbursed for its manufacturing costs as commercial product is shipped to its collaborators; however, recognition of such cost reimbursements as revenue is deferred until the product is sold by the Company's collaborators to third-party customers. In addition, we may also be reimbursed for a portion of costs incurred for other commercial-related activities, which are recorded as collaboration revenue in the period in which such costs are incurred.

Research and Development Expenses

Research and development expenses include costs directly attributable to the conduct of research and development programs, including the cost of salaries, payroll taxes, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, costs related to research collaboration and licensing agreements, the cost of services provided by outside contractors, including services related to the Company's clinical trials, clinical trial expenses, the full cost of manufacturing drug for use in research, preclinical development, and clinical trials, amounts that the Company is obligated to reimburse to collaborators for research and development expenses that they incur, and the allocable portions of facility costs, such as rent, utilities, insurance, repairs and maintenance, depreciation, and general support services. Costs associated with research and development are expensed.

For each clinical trial that we conduct, certain clinical trial costs are expensed immediately, while others are expensed over time based on the expected total number of patients in the trial, the rate at which patients enter the trial, and/or the period over which clinical investigators, contract research organizations ("CROs"), or other third-party service providers are expected to provide services. In the event of early termination of a clinical trial, we accrue and recognize expenses in an amount based on our estimate of the remaining noncancelable obligations associated with the winding down of the clinical trial and/or penalties.

Stock-based Compensation

The Company recognizes stock-based compensation expense for equity grants under the Company's long-term incentive plans to employees and non-employee members of the Company's board of directors (as applicable) based on the grant-date fair value of those awards. The grant-date fair value of an award is generally recognized as compensation expense over the award's requisite service period.

The fair value of stock option awards are estimated using the Black-Scholes model. Stock-based compensation expense also includes an estimate, which is made at the time of grant, of the number of awards that are expected to be forfeited. This estimate is revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

The fair value of performance-based restricted stock units which are subject to vesting based on the Company’s attainment of pre-established performance goals is estimated using a Monte Carlo simulation. The probability of the number of actual shares expected to be earned is considered in the grant-date valuation, and therefore, stock-based compensation expense is not adjusted at the vesting date to reflect the actual number of shares earned.

Income Taxes

The provision for income taxes includes U.S. federal, state, local, and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns, including deferred tax assets and liabilities for expected amounts of global intangible low-taxed income ("GILTI") inclusions, are recognized on the difference between the tax basis of assets and liabilities and their respective financial reporting amounts ("temporary differences") at enacted tax rates in effect for the years in which the differences are expected to reverse. A valuation allowance is established for deferred tax assets for which it is more likely than not that some portion or all of the deferred tax assets will not be realized.

Uncertain tax positions, for which management's assessment is that there is more than a 50% probability of sustaining the position upon challenge by a taxing authority based upon its technical merits, are subjected to certain recognition and measurement criteria. The Company re-evaluates uncertain tax positions and considers various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, and changes in facts or circumstances related to a tax position. The Company adjusts the level of the liability to reflect any subsequent changes in the relevant facts and circumstances

surrounding the uncertain positions. The Company recognizes interest and penalties related to income tax matters in income tax expense.

Per Share Data

Basic net income per share is computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Basic net income per share excludes restricted stock until vested. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were converted or exercised during the period, when the effect is dilutive. Common stock equivalents include: (i) outstanding stock options and restricted stock under the Company's long-term incentive plans, which are included under the "treasury stock method" when dilutive and (ii) Common Stock to be issued upon the achievement of certain market conditions, which are included under the "treasury stock method" when dilutive.

Recently Issued Accounting Standards

In June 2016, the FASB issued 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.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of income before income tax

Components of income before income taxes consist of the following:



	Year Ended December 31,
	2019		2018		2017
United States	$	2,011.2	$	2,151.7	$	1,964.7
Foreign	417.9		401.8		113.8
	$	2,429.1	$	2,553.5	$	2,078.5

Schedule of components of income tax expense

Components of income tax expense consist of the following:



	Year Ended December 31,
	2019			2018			2017
Current:
Federal	$	444.6		$	223.7		$	560.3
State	1.9			4.8			(4.1		)
Foreign	(2.6		)	20.6			4.8
Total current tax expense	443.9			249.1			561.0
Deferred:
Federal	(132.0		)	687.6			317.1
State	(1.7		)	(1.9		)	(1.3		)
Foreign	3.1			(825.7		)	3.2
Total deferred tax (benefit) expense	(130.6		)	(140.0		)	319.0
	$	313.3		$	109.1		$	880.0

Schedule of effective income tax rate reconciliation

A reconciliation of the U.S. statutory income tax rate to the Company's effective income tax rate is as follows:



	Year Ended December 31,
	2019		2018		2017
U.S. federal statutory tax rate	21.0	%	21.0	%	35.0	%
Income tax credits	(4.6	)	(2.6	)	(1.3	)
Stock-based compensation	(2.5	)	(2.5	)	(9.0	)
Foreign-derived intangible income deduction	(1.6	)	(1.0	)	—
Taxation of non-U.S. operations	(1.0	)	(1.9	)	0.7
Non-deductible Branded Prescription Drug Fee	0.7		0.6		1.7
Sale of non-inventory related assets between foreign subsidiaries	—		(6.3	)	—
Impact of change in U.S. corporate tax rate (the Act)	—		(2.7	)	15.7
Domestic production activities deduction	—		—		(2.6	)
Other permanent differences	0.9		(0.3	)	2.1
Effective income tax rate	12.9	%	4.3	%	42.3	%

Schedule of deferred tax assets and liabilities

Significant components of the Company's deferred tax assets and liabilities are as follows:



	As of December 31,
	2019			2018
Deferred tax assets:
Deferred compensation	$	519.7		$	458.2
Fixed assets and intangible assets	192.0			107.8
Accrued expenses	75.9			53.3
Deferred revenue	22.0			20.2
Other	—			33.3
Total deferred tax assets	809.6			672.8
Valuation allowance	(7.0		)	—
Deferred tax assets, net of valuation allowance	802.6			672.8

Deferred tax liabilities:
Other	(11.2		)	(2.7		)
Net deferred tax assets	$	791.4		$	670.1

Schedule of unrecognized tax benefits



	2019			2018			2017
Balance as of January 1	$	189.5		$	146.2		$	117.2
Gross increases related to current year tax positions	37.9			51.4			49.0
Gross (decreases) increases related to prior year tax positions	(7.2		)	5.6			(5.6		)
Gross decreases due to settlements and lapse of statutes of limitations	(9.4		)	(13.7		)	(14.4		)
Balance as of December 31	$	210.8		$	189.5		$	146.2

Unaudited Quarterly Results

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Unaudited Quarterly Results

Summarized quarterly financial data (unaudited) for the years ended December 31, 2019 and 2018 are set forth in the following tables.



	First Quarter Ended March 31, 2019		Second Quarter Ended June 30, 2019⁽¹⁾		Third Quarter Ended September 30, 2019		Fourth Quarter Ended December 31, 2019
Revenues	$	1,711.8	$	1,933.7	$	2,048.4	$	2,169.5
Operating expenses	$	1,231.8	$	1,618.1	$	1,309.9	$	1,493.8
Net income	$	461.1	$	193.1	$	669.6	$	792.0
Net income per share - basic	$	4.23	$	1.77	$	6.12	$	7.25
Net income per share - diluted	$	3.99	$	1.68	$	5.86	$	6.93


	First Quarter Ended March 31, 2018		Second Quarter Ended June 30, 2018		Third Quarter Ended September 30, 2018		Fourth Quarter Ended December 31, 2018⁽²⁾⁽³⁾
Revenues	$	1,511.5	$	1,608.0	$	1,663.5	$	1,927.8
Operating expenses	$	944.3	$	985.8	$	1,036.6	$	1,209.7
Net income	$	478.0	$	551.4	$	594.7	$	820.4
Net income per share - basic	$	4.44	$	5.12	$	5.50	$	7.58
Net income per share - diluted	$	4.16	$	4.82	$	5.17	$	7.15

⁽¹⁾Included in research and development expenses was a $400.0 million up-front payment in connection with the Alnylam collaboration agreement. See Note 3.
⁽²⁾ Includes impact of a cumulative catch-up adjustment recorded to revenue upon termination of the 2015 IO Discovery Agreement. See Note 3.
⁽³⁾ Includes tax impact of the sale of non-inventory related assets between foreign subsidiaries completed during the fourth quarter of 2018. See Note 15.

Property, Plant, and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

The estimated useful lives of property, plant, and equipment are as follows:



Building and improvements		10–50 years
Laboratory and other equipment		3–10 years
Furniture and fixtures		5 years

Property, plant, and equipment consists of the following:



	As of December 31,
	2019			2018
Land	$	230.8		$	199.0
Building and improvements	1,683.4			1,507.2
Leasehold improvements	97.6			97.0
Construction in progress	644.8			469.6
Laboratory equipment	850.7			773.7
Computer equipment and software	183.7			145.8
Furniture, office equipment, and other	121.8			112.2
	3,812.8			3,304.5
Less, accumulated depreciation and amortization	(922.4		)	(728.7		)
	$	2,890.4		$	2,575.8

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

See Note 16 for disclosures related to legal contingencies.

a. 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 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 "Lease 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 Lease 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 Lease 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 December 31, 2019.

Amounts recognized in the 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 December 31, 2019.



		December 31,
	Classification	2019
Finance lease right-of-use assets	Property, plant, and equipment, net⁽¹⁾	$	660.1
Finance lease liabilities	Finance lease liabilities (noncurrent)	$	713.9

⁽¹⁾ Finance lease right-of-use assets are recorded net of accumulated amortization of $76.1 million as of December 31, 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:



	Year Ended December 31, 2019
Amortization of right-of-use assets	$	14.4
Interest on lease liabilities	27.6
	$	42.0

Other information related to our finance lease includes the following:



	December 31,
	2019
Remaining lease term (in years)	2.17
Discount rate	3.05	%

Supplemental information

The following is a maturity analysis of our lease liabilities as of December 31, 2019:



	Operating Leases			Finance Leases
2020	$	7.6		$	22.2
2021	6.6			21.9
2022	3.3			725.4
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	26.1			769.5
Imputed interest	(2.5		)	(50.1		)
Debt financing costs	—			(5.5		)
Total lease liabilities	$	23.6		$	713.9

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

b. Research Collaboration and Licensing Agreements

As part of our research and development efforts, we enter into research collaboration and licensing agreements with other companies, universities, and other organizations. These agreements contain varying terms and provisions which include fees to be paid by the Company, services to be provided, and license rights to certain proprietary technology developed under the agreements. Some of these agreements may require the Company to pay additional amounts upon the achievement of various development and commercial milestones, contingent upon the occurrence of various future events. Additionally, we have in-license patent and/or technology agreements which contain provisions which require the Company to pay royalties, as defined, at rates that range from 0.5% to 11.5%, in the event the Company sells or licenses any proprietary products developed under the respective agreements. The Company also has contingent reimbursement obligations to its collaborators Sanofi and Bayer out of the respective collaboration's profits, if they are sufficient for that purpose. See Note 3 for a more detailed description of collaboration agreements.

For the years ended December 31, 2019, 2018, and 2017, the Company recorded royalty expense in Cost of goods sold and Cost of collaboration and contract manufacturing of $54.2 million, $36.7 million, and $30.8 million, respectively, based on product sales of commercial products under various licensing agreements.

Business Overview and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Concentration of Credit Risk

Cash and Cash Equivalents

Debt and Equity Securities

Accounts Receivable

Inventories

Inventories are stated at the lower of cost or net realizable value. The Company determines the cost of inventory using the first-in, first-out, or FIFO, method.

Property, Plant and Equipment

Property, Plant, and Equipment



Building and improvements		10–50 years
Laboratory and other equipment		3–10 years
Furniture and fixtures		5 years

Revenue Recognition

Product Revenue

qualified healthcare providers. The Company's reserve for this discounted pricing is based on expected sales to qualified healthcare providers and the chargebacks that customers have already claimed.

Collaboration Revenue

Research and Development Expenses

Stock-based Compensation

Income Taxes

surrounding the uncertain positions. The Company recognizes interest and penalties related to income tax matters in income tax expense.

Per Share Data

Recently Issued Accounting Standards

Leases

Operating leases

Finance leases

Legal Costs

Costs associated with the Company's involvement in legal proceedings are expensed as incurred.

Credit Facility	12 Months Ended
Credit Facility	Dec. 31, 2019
Debt Disclosure [Abstract]
Credit Facility	Credit Facility In December 2018, we entered into an agreement with a syndicate of lenders (the "Credit Agreement") which provides for a $750.0 million senior unsecured five-year revolving credit facility (the "Credit Facility"), and contemporaneously terminated our then-existing credit agreement (the "Prior Credit Agreement"). The Credit Agreement was entered into on terms substantially similar to those of the Prior Credit Agreement. No borrowings were outstanding under the Prior Credit Agreement at the time of its termination. The Credit Agreement includes an option for us to elect to increase the commitments under the Credit Facility and/or to enter into one or more tranches of term loans in the aggregate principal amount of up to $250.0 million, subject to the consent of the lenders providing the additional commitments or term loans, as applicable, and certain other conditions. Proceeds of the loans under the Credit Facility may be used to finance working capital needs, and for general corporate or other lawful purposes, of Regeneron and its subsidiaries. The Credit Agreement also provides a $50.0 million sublimit for letters of credit. The Credit Agreement includes an option for us to elect to extend the maturity date of the Credit Facility beyond December 2023, subject to the consent of the extending lenders and certain other conditions. Amounts borrowed under the Credit Facility may be prepaid, and the commitments under the Credit Facility may be terminated, at any time without premium or penalty. We had no borrowings outstanding under the Credit Facility as of December 31, 2019. The Credit Agreement contains financial and operating covenants. The Company was in compliance with all covenants of the Credit Facility as of December 31, 2019.

Legal Matters	12 Months Ended
Legal Matters	Dec. 31, 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. As of December 31, 2019 and 2018, the Company had accruals for loss contingencies of $100.0 million and $30.0 million, respectively. 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 United States As described in greater detail below, the Company is currently a party to patent infringement actions initiated by Amgen Inc. (and/or its affiliated entities) against the Company and/or 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. Europe 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"). Amgen subsequently enforced the injunction and, as a result, commercialization of Praluent in Germany has been discontinued. 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 rescheduled. On December 17, 2019, Amgen initiated a lawsuit alleging infringement of the Dutch designation of the '124 Patent in the District Court of The Hague in the Netherlands, against Sanofi-Aventis Netherlands B.V. and Sanofi-Aventis Groupe S.A. The Company has not been named as a defendant in this action. Amgen alleges, among other things, patent infringement based on the production, importation, and commercialization of Praluent (alirocumab) in the Netherlands. Amgen's requests are made on an accelerated basis and include, among other things, a request for a permanent injunction, damages, an order for customer information, a recall order, a destruction order, and an order for costs. A trial has been scheduled for October 30, 2020. On December 20, 2019, Amgen filed a lawsuit for infringement of the Italian designation of the '124 Patent in the Tribunale di Milano - Enterprise Chamber in Milan, Italy, against Sanofi-Aventis Groupe S.A., Sanofi Chimie, and Sanofi SpA. The Company has not been named as a defendant in this action. Amgen alleges that the production, importation, and commercialization of Praluent (alirocumab) in Italy infringes the '124 Patent. The writ of summons filed by Amgen seeks, among other things, a declaration of infringement, a permanent injunction, withdrawal of product from the market, and damages. On December 20, 2019, Amgen also filed a lawsuit alleging infringement of the Spanish designation of the '124 Patent in the Juzgado de lo Mercantil No. 5 (Commercial Court) in Barcelona, Spain, against Sanofi-Aventis, S.A. The Company has not been named as a defendant in this action. Amgen alleges, among other things, patent infringement based on the manufacture, offering for sale, introduction into the market, use, and importation or possession of Praluent (alirocumab) in Spain. Amgen seeks, among other things, a permanent injunction, withdrawal of Praluent from the market, seizure and destruction of Praluent from the market and in storage, and damages in the form of lost profits and costs and expenses. 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. Other 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. Sanofi K.K. appealed the IPHC's decision in the infringement proceedings to the Supreme Court of Japan on November 12, 2019. The injunction will remain stayed pending appeal of the IPHC's decision to the Supreme Court of Japan. Proceedings Relating to Dupixent (dupilumab) Injection United States 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. Europe 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.

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Revenues	$ 7,863.4	$ 6,710.8	$ 5,872.2
Expenses:
Research and development	3,036.6	2,186.1	2,075.1
Selling, general, and administrative	1,834.8	1,556.2	1,320.4
Total expenses	5,653.6	4,176.4	3,792.6
Income from operations	2,209.8	2,534.4	2,079.6
Other income (expense):
Other income (expense), net	249.5	47.3	24.0
Interest expense	(30.2)	(28.2)	(25.1)
Total other income (expense)	219.3	19.1	(1.1)
Income before income taxes	2,429.1	2,553.5	2,078.5
Income tax expense	(313.3)	(109.1)	(880.0)
Net income	$ 2,115.8	$ 2,444.4	$ 1,198.5
Net income per share - basic (in dollars per share)	$ 19.38	$ 22.65	$ 11.27
Net income per share - diluted (in dollars per share)	$ 18.46	$ 21.29	$ 10.34
Weighted average shares outstanding - basic (in shares)	109.2	107.9	106.3
Weighted average shares outstanding - diluted (in shares)	114.6	114.8	115.9
Statements of Comprehensive Income
Net income	$ 2,115.8	$ 2,444.4	$ 1,198.5
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on marketable securities	35.9	(7.0)	12.7
Unrealized (loss) gain on cash flow hedges	(2.5)
Unrealized (loss) gain on cash flow hedges		0.7	0.8
Comprehensive income	2,149.2	2,438.1	1,212.0
Product
Revenues:
Revenues	4,834.4	4,106.2	3,718.5
Expenses:
Cost of goods sold	362.3	180.0	202.5
Collaboration and contract manufacturing
Expenses:
Cost of goods sold	419.9	254.1	194.6
Sanofi \| Product and service, other
Revenues:
Revenues	1,426.8	1,111.1	877.2
Bayer \| Product and service, other
Revenues:
Revenues	1,188.8	1,076.7	938.1
Other \| Product and service, other
Revenues:
Revenues	$ 413.4	$ 416.8	$ 338.4

Collaboration and License Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, Teva Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Accounts receivable (recorded within Prepaid expenses and other current assets)	$ 387.1	$ 243.3
Teva
Disaggregation of Revenue [Line Items]
Accounts receivable (recorded within Prepaid expenses and other current assets)	21.2	28.8
Deferred revenue	$ 114.4	$ 194.5

Commitments and Contingencies - Amounts recognized in Condensed Consolidated Balance Sheet (Details) $ in Millions	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Finance lease right-of-use assets	$ 660.1
Finance lease liabilities	713.9
Accumulated amortization	$ 76.1

Property, Plant, and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 205.2	$ 144.1	$ 142.2
Property, plant, and equipment, net		2,575.8
United States
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	2,117.6	1,813.8
Europe
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	$ 772.8	$ 762.0

Long-Term Incentive Plans

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Long-Term Incentive Plans

The Company has used long-term incentive plans for the purpose of granting equity awards to employees of the Company, including officers, and nonemployees, including consultants and nonemployee members of the Company's board of directors (collectively, "Participants"). The Participants may receive awards as determined by a committee of independent members of the Company's board of directors or, to the extent authorized by such committee with respect to certain Participants, a duly authorized employee (collectively, the "Committee"). The incentive plan currently used by the Company is the Amended and Restated Regeneron Pharmaceuticals, Inc. 2014 Long-Term Incentive Plan (the "Amended and Restated 2014 Incentive Plan"). It was adopted and approved by the Company's shareholders in 2017, at which time the Company registered an additional 12,000,000 shares of Common Stock for issuance thereunder. As of the shareholder approval date, the Amended and Restated 2014 Incentive Plan provided for the issuance of up to 18,559,431 shares of Common Stock in respect of awards. In addition, upon expiration, forfeiture, surrender, exchange, cancellation, or termination of any award previously granted under the Amended and Restated 2014 Incentive Plan, the Regeneron Pharmaceuticals, Inc. 2014 Long-Term Incentive Plan (the "Original 2014 Incentive Plan"), or the Second Amended and Restated 2000 Long-Term Incentive Plan (the predecessor to the Original 2014 Incentive Plan), any shares subject to such award are added to the pool of shares available for grant under the Amended and Restated 2014 Incentive Plan.

The awards that may be made under the Amended and Restated 2014 Incentive Plan include: (a) incentive stock options and nonqualified stock options, (b) shares of restricted stock, (c) shares of phantom stock (also referred to as restricted stock units, which may be time- or performance-based), and (d) other awards. Any award granted may (but is not required to) be subject to vesting based on the attainment by the Company of performance goals pre-established by the Committee.

Stock option awards grant Participants the right to purchase shares of Common Stock at prices determined by the Committee, with exercise prices that are equal to or greater than the average of the high and low market prices of the Company's Common Stock on the date of grant (the "Market Price"). Options vest over a period of time determined by the Committee, generally on a pro rata basis over a three- to four-year period. The Committee also determines the expiration date of each option. The maximum term of options that have been awarded under the 2000 Incentive Plan, the Original 2014 Incentive Plan, and the Amended and Restated 2014 Incentive Plan (collectively, the "Incentive Plans") is ten years.

Restricted stock awards grant Participants shares of restricted Common Stock or allow Participants to purchase such shares at a price determined by the Committee. Such shares are nontransferable for a period determined by the Committee ("vesting period"). Should employment terminate, as specified in the Incentive Plans, except as determined by the Committee in its discretion and subject to the applicable Incentive Plan documents, the ownership of any unvested restricted stock will be transferred to the Company.

Phantom stock awards provide the Participant the right to receive, within 30 days of the date on which the share vests, an amount, in cash and/or shares of Common Stock as determined by the Committee, equal to the sum of the fair market value of a share of Common Stock on the date such share of phantom stock vests and the aggregate amount of cash dividends paid with respect to a share of Common Stock during the period from the grant date of the share of phantom stock to the date on which the share vests.

The Incentive Plans contain provisions that allow for the Committee to provide for the immediate vesting of awards upon a change in control of the Company, as defined in the Incentive Plans.

As of December 31, 2019, there were 9,546,628 shares available for future grants under the Amended and Restated 2014 Incentive Plan. No additional awards may be made under the 2000 Incentive Plan or the Original 2014 Incentive Plan.


a.	Stock Options

Transactions involving stock option awards during 2019 under the Company's Incentive Plans are summarized in the table below.



		Number of Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Intrinsic Value
Outstanding as of December 31, 2018		28,279,696		$	319.28
2019:	Granted	3,271,222		$	366.65
	Forfeited	(576,806	)	$	395.88
	Expired	(300,581	)	$	460.37
	Exercised	(2,064,254	)	$	103.51
Outstanding as of December 31, 2019		28,609,277		$	337.24	6.17	$	1,805.9

Vested and expected to vest as of December 31, 2019		27,524,704		$	335.73	6.06	$	1,800.5

Exercisable as of December 31, 2019		19,291,335		$	318.15	4.90	$	1,763.9

The Company satisfies stock option exercises with newly issued shares of the Company's Common Stock. The total intrinsic value of stock options exercised during 2019, 2018, and 2017 was $558.9 million, $510.6 million, and $735.6 million, respectively. The intrinsic value represents the amount by which the market price of the underlying stock exceeds the exercise price of an option.

The table below summarizes the weighted-average exercise prices and weighted-average grant-date fair values of options issued during the years ended December 31, 2019, 2018, and 2017. The fair value of each option granted under the Company's Incentive Plans during these periods was estimated on the date of grant using the Black-Scholes option-pricing model.



	Number of Options Granted	Weighted-Average Exercise Price		Weighted-Average Fair Value
2019:
Exercise price equal to Market Price	3,271,222	$	366.65	$	100.80
2018:
Exercise price equal to Market Price	4,665,320	$	378.51	$	114.39
2017:
Exercise price equal to Market Price	4,235,015	$	383.56	$	118.70

For the years ended December 31, 2019, 2018, and 2017, the Company recognized $422.8 million, $421.8 million, and $492.8 million, respectively, of non-cash stock-based compensation expense related to stock option awards (net of amounts capitalized as inventory of $2.4 million, $17.1 million, and $16.8 million, respectively). As of December 31, 2019, there was $521.9 million of stock-based compensation cost related to outstanding stock options, net of estimated forfeitures, which had not yet been recognized. The Company expects to recognize this compensation cost over a weighted-average period of 1.9 years.

Fair Value Assumptions:

The following table summarizes the weighted average values of the assumptions used in computing the fair value of option grants during 2019, 2018, and 2017.



	2019		2018		2017
Expected volatility	28	%	29	%	31	%
Expected lives from grant date	5.0 years		4.9 years		5.1 years
Expected dividend yield	0	%	0	%	0	%
Risk-free interest rate	1.74	%	2.69	%	2.16	%

Expected volatility has been estimated based on actual movements in the Company's stock price over the most recent historical periods equivalent to the options' expected lives. Expected lives are principally based on the Company's historical exercise experience with previously issued employee and board of directors' option grants. The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. The risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the options' expected lives.


b.	Restricted Stock Awards and Restricted Stock Units

A summary of the Company's activity related to restricted stock awards and restricted stock units (including performance-based restricted stock units) (collectively, "restricted stock") during 2019 is summarized below. As described in Note 1, the fair value of performance-based restricted stock units is estimated using a Monte Carlo simulation.



		Number of Shares/Units		Weighted-Average Grant Date Fair Value
Balance as of December 31, 2018		472,630		$	386.10
2019:	Granted	698,103		$	356.33
	Vested	(3,090	)	$	406.65
	Forfeited/Cancelled	(5,857	)	$	385.90
Balance as of December 31, 2019		1,161,786		$	368.16

The Company recognized non-cash stock-based compensation expense from restricted stock of $41.5 million, $5.6 million, and $14.5 million in 2019, 2018, and 2017, respectively (net of amounts capitalized as inventory, which were not material for each of the three years). As of December 31, 2019, there was $274.6 million of stock-based compensation cost related to unvested restricted stock which had not yet been recognized. The Company expects to recognize this compensation cost over a weighted-average period of 3.4 years.

Collaboration and License Agreements - Alnylam Narratives (Details) - USD ($)		1 Months Ended	3 Months Ended
	Aug. 31, 2019	Apr. 30, 2019	Jun. 30, 2019
Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Upfront payment made			$ 400,000,000.0
Collaborative arrangement additional payment eligible		$ 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 Pharmaceuticals, Inc. Stock Purchase Agreement
Disaggregation of Revenue [Line Items]
Payments made to acquire equity		$ 400,000,000.0
Maximum \| Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Initial research term		7 years
Extension of research term fee		$ 400,000,000.0
Minimum \| Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Extension of research term fee		$ 200,000,000.0

Product Sales (Tables)

12 Months Ended

Dec. 31, 2019

Revenues [Abstract]

Schedule of Product Sales

Net product sales consist of the following:



	Year Ended December 31,
Net Product Sales in the United States	2019		2018		2017
EYLEA	$	4,644.2	$	4,076.7	$	3,701.9
Libtayo	175.7		14.8		—
ARCALYST	14.5		14.7		16.6
	$	4,834.4	$	4,106.2	$	3,718.5

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):



	Year Ended December 31,
Bayer EYLEA Collaboration Revenue	2019		2018		2017
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	1,091.4	$	992.3	$	802.3
Reimbursement of EYLEA development expenses	23.0		11.2		13.3
Other	74.4		73.6		58.7
	$	1,188.8	$	1,077.1	$	874.3

The collaboration revenue we earned from Sanofi is detailed below:



	Year Ended December 31,
Sanofi Collaboration Revenue	2019			2018			2017
Antibody:
Reimbursement of research and development expenses	$	277.7		$	265.3		$	508.4
Reimbursement of commercialization-related expenses	479.9			417.2			368.8
Reimbursement for manufacturing of commercial supplies	206.7			127.6			35.1
Regeneron's share of profits (losses) in connection with commercialization of antibodies	209.3			(227.0		)	(442.6		)
Other	(1.5		)	(24.1		)	84.0
Total Antibody	1,172.1			559.0			553.7
Immuno-oncology:
Reimbursement of research and development expenses	163.0			311.8			240.0
Reimbursement of commercialization-related expenses	10.3			8.9			7.0
Amounts recognized in connection with up-front payments received	92.7			243.8			80.0
Other	(11.3		)	(12.4		)	(3.5		)
Total Immuno-oncology	254.7			552.1			323.5
	$	1,426.8		$	1,111.1		$	877.2

Schedules of Concentration of Risk, by Risk Factor



	Year Ended December 31,
	2019		2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	57	%	56	%	51	%
McKesson Corporation	33	%	36	%	29	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		**		19	%

** Sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue during the period.

Sales Related Deductions Activity

The following table summarizes the provisions, and credits/payments, for sales-related deductions for the years ended December 31, 2019, 2018, and 2017.



	Rebates, Chargebacks, and Discounts			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2016	$	12.7		$	29.5		$	3.6		$	45.8
Provisions	167.8			194.1			46.4			408.3
Credits/payments	(150.6		)	(189.5		)	(28.7		)	(368.8		)
Balance as of December 31, 2017	29.9			34.1			21.3			85.3
Provisions	223.4			211.0			44.5			478.9
Credits/payments	(212.2		)	(203.1		)	(57.5		)	(472.8		)
Balance as of December 31, 2018	41.1			42.0			8.3			91.4
Provisions	423.2			242.9			61.8			727.9
Credits/payments	(384.0		)	(238.5		)	(40.7		)	(663.2		)
Balance as of December 31, 2019	$	80.3		$	46.4		$	29.4		$	156.1

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Collaboration and License Agreements

a. Sanofi

Sanofi owned a total of 23,350,365 shares of our Common Stock as of December 31, 2019, a portion of which was purchased in connection with the companies' antibody collaboration described below. See Note 12 for a description of the investor agreement between us and Sanofi.

The collaboration revenue we earned from Sanofi is detailed below:



	Year Ended December 31,
Sanofi Collaboration Revenue	2019			2018			2017
Antibody:
Reimbursement of research and development expenses	$	277.7		$	265.3		$	508.4
Reimbursement of commercialization-related expenses	479.9			417.2			368.8
Reimbursement for manufacturing of commercial supplies	206.7			127.6			35.1
Regeneron's share of profits (losses) in connection with commercialization of antibodies	209.3			(227.0		)	(442.6		)
Other	(1.5		)	(24.1		)	84.0
Total Antibody	1,172.1			559.0			553.7
Immuno-oncology:
Reimbursement of research and development expenses	163.0			311.8			240.0
Reimbursement of commercialization-related expenses	10.3			8.9			7.0
Amounts recognized in connection with up-front payments received	92.7			243.8			80.0
Other	(11.3		)	(12.4		)	(3.5		)
Total Immuno-oncology	254.7			552.1			323.5
	$	1,426.8		$	1,111.1		$	877.2

Antibody

In 2007, the Company entered into a global, strategic collaboration with Sanofi to discover, develop, and commercialize fully human monoclonal antibodies (the "Antibody Collaboration"). The Antibody Collaboration was governed by the companies' Discovery and Preclinical Development Agreement ("Antibody Discovery Agreement") and a License and Collaboration Agreement (each as amended). In connection with the execution of the Antibody Discovery Agreement in 2007, the Company received a non-refundable up-front payment of $85.0 million from Sanofi. In addition, under the Antibody Discovery Agreement, Sanofi funded the Company's research to identify and validate potential drug discovery targets and develop fully human monoclonal antibodies against these targets. Pursuant to the Antibody Discovery Agreement, as amended, Sanofi funded $130.0 million of the Company's research activities in 2017. The Company's Antibody Discovery Agreement with Sanofi ended on December 31, 2017 without any extension and, therefore, funding from Sanofi under the Antibody Discovery Agreement ceased after 2017. The Company accelerated the recognition of deferred revenue from the $85.0 million up-front payment and other payments in connection with Sanofi's decision to end the Antibody Discovery Agreement between the Company and Sanofi on December 31, 2017. The Company has the right to develop or continue to develop product candidates discovered under the Antibody Discovery Agreement, with the exception of those that are being developed (and commercialized, as applicable) under the Antibody License and Collaboration Agreement (i.e., Dupixent, Praluent, Kevzara, and REGN3500), independently, or with other collaborators.

Under the 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. The Company recognized as research and development expense $46.0 million, $47.7 million, and $91.8 million in 2019, 2018, and 2017, respectively, its share of antibody development expenses that Sanofi incurred related to Dupixent, Praluent, and Kevzara. All other agreed-upon worldwide development expenses incurred by both companies are funded by Sanofi. We are obligated to reimburse Sanofi for 50% of worldwide development expenses that were fully funded by Sanofi and 30% of Shared Phase 3 Trial Costs, in accordance with a defined formula based on the amounts of these expenses and the Company's share of collaboration profits from commercialization of collaboration products. However, we are only required to apply 10% of our share of the profits from the Antibody Collaboration in any calendar quarter to reimburse Sanofi for these

development costs. The Company's contingent reimbursement obligation to Sanofi under the Antibody Collaboration was approximately $2.990 billion as of December 31, 2019.

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 2019, Sanofi elected to sell, and we elected to purchase (in cash), 93,286 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 $29.4 million, as Treasury Stock during 2019. During 2018, the cost of shares of the Company's Common Stock that we elected to purchase from Sanofi (in cash) in connection with Sanofi's funding obligation for Dupilumab/REGN3500 Eligible Investments was not material.

Regeneron is obligated to use commercially reasonable efforts to supply clinical requirements of each drug candidate under the Antibody Collaboration until commercial supplies of that drug candidate are being manufactured. Sanofi leads commercialization activities for products developed under the License and Collaboration Agreement, subject to the Company's right to co-commercialize such products. The Company has exercised its option to co-commercialize Dupixent, Praluent, and Kevzara in the United States. While we are not currently co-commercializing these antibodies outside the United States, we have recently exercised our option to co-commercialize Dupixent in certain countries outside the United States. We currently anticipate commencing co-commercialization of Dupixent outside the United States at the end of 2020. The parties equally share profits and losses from sales within the United States. The parties share profits outside the United States on a sliding scale based on sales starting at 65% (Sanofi)/35% (Regeneron) and ending at 55% (Sanofi)/45% (Regeneron), and losses outside the United States at 55% (Sanofi)/45% (Regeneron). In addition to profit and loss sharing, the Company is entitled to receive up to $250.0 million in sales milestone payments, with milestone payments commencing after aggregate annual sales of antibodies (subject to this agreement) outside the United States exceed $1.0 billion on a rolling twelve-month basis.

"Reimbursement of commercialization-related expenses" in the table above represents reimbursement of internal and external costs in connection with commercializing Dupixent, Praluent, and Kevzara. During the same periods that the Company recorded reimbursements from Sanofi related to the Company's commercialization expenses, the Company also recorded its share of profits or losses in connection with the companies commercializing Dupixent, Praluent, and Kevzara, within Sanofi collaboration revenue.

With respect to each antibody product in development under the License and Collaboration Agreement, Sanofi or the Company may, by giving twelve months' notice, opt-out of further development and/or commercialization of the product, in which event the other party retains exclusive rights to continue the development and/or commercialization of the product. Upon termination of the collaboration in its entirety, the Company's obligation to reimburse Sanofi for development costs out of any future profits from collaboration products will terminate.

In December 2019, we and Sanofi announced our intent to restructure the Antibody Collaboration for Kevzara and Praluent and enter into a royalty-based arrangement. Under the proposed terms of the agreement, Sanofi is expected to gain sole global rights to Kevzara and sole rights to Praluent outside of the United States. Regeneron is expected to gain sole U.S. rights to Praluent. Under the proposed terms, each party will be solely responsible for funding development and commercialization expenses in their respective territories. In the fourth quarter of 2019, we recorded a $35.2 million charge related to employee separation costs, as the Company has eliminated certain commercialization activities and related headcount in connection with the proposed restructuring of the antibody agreement with Sanofi. The proposed agreement with Sanofi to restructure the antibody agreement, which is expected to be finalized in the first quarter of 2020, will not impact Dupixent and REGN3500 as the companies will continue to collaborate on these antibodies under the terms of the License and Collaboration Agreement.

The Company's significant promised goods and services consist of providing research and development services, including the manufacturing of clinical supplies, and providing commercial-related services, including the manufacturing of commercial supplies. 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. 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 December 31, 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:



	As of December 31,
	2019		2018
Accounts receivable	$	272.7	$	138.2
Deferred revenue	$	337.2	$	236.1

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase due to shipments of commercial supplies to Sanofi	$	335.7
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(240.4	)

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"). In connection with the execution of the original Immuno-oncology Discovery and Development Agreement in 2015 ("2015 IO Discovery Agreement"), which has been replaced by the Amended IO Discovery Agreement (as discussed below), Sanofi made a $265.0 million non-refundable up-front payment to the Company. Pursuant to the 2015 IO Discovery Agreement, the Company was to spend up to $1.090 billion ("IO Discovery Budget") to identify and validate potential immuno-oncology targets and develop therapeutic antibodies against such targets through clinical proof-of-concept, and Sanofi was to reimburse the Company for up to $825.0 million of these costs, subject to certain annual limits. The original term of the 2015 IO Discovery Agreement was to continue through the later of five years from the effective date of the IO Collaboration or the date the IO Discovery Budget was exhausted, subject to Sanofi’s option to extend it for up to an additional three years for the continued development (and funding) of selected ongoing programs.

Effective December 31, 2018, the Company and Sanofi entered into the 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.

Under the terms of the Amended IO Discovery Agreement, the Company is required to conduct development activities with respect to (i) the BCMAxCD3 Program through the earlier of clinical proof-of-concept or the expenditure of $70.0 million and (ii) the MUC16xCD3 Program through the earlier of clinical proof-of-concept or the expenditure of $50.0 million (the "MUC16xCD3 Program Costs Cap"); provided that under certain circumstances, Sanofi will have the option to increase the MUC16xCD3 Program Costs Cap to $70.0 million by making a payment to the Company in the amount of $20.0 million.

Pursuant to the Amended IO Discovery Agreement, we are primarily responsible for antibody development, preclinical activities, toxicology studies, manufacture of clinical supplies, filing of Investigational New Drug Applications ("INDs"), and clinical development through proof-of-concept with respect to the BCMAxCD3 Program and MUC16xCD3 Program. We are obligated to reimburse Sanofi for half of the development costs they funded that are attributable to clinical development of antibody product candidates from our share of future profits from commercialized IO Collaboration products. However, the Company is only required to apply 10% of its share of the profits from IO Collaboration products in any calendar quarter towards reimbursing Sanofi for these development costs. The Company's contingent reimbursement obligation to Sanofi under the IO Collaboration was approximately $75 million as of December 31, 2019.

With regard to the BCMAxCD3 Program and the MUC16xCD3 Program, when (i) clinical proof-of-concept is established, (ii) the applicable Program Costs Cap is reached, or (iii) in certain other limited circumstances, Sanofi will have the option to license rights to the product candidate and other antibodies targeting the same targets for, with regard to BCMAxCD3, immuno-oncology indications, and with regard to MUC16xCD3, all indications, pursuant to the IO License and Collaboration Agreement, as amended. If Sanofi does not exercise its option to license rights to a product candidate, we will retain the exclusive right to develop and commercialize such product candidate and Sanofi will receive a royalty on sales. Pursuant to the Amended IO Discovery Agreement, the parties agreed that (i) if Sanofi exercises its option with respect to a BCMAxCD3 Program antibody, Sanofi will lead the development and global commercialization of such BCMAxCD3 Program antibody; and (ii) if Sanofi exercises its option with respect to a MUC16xCD3 Program antibody, (x) we will lead the development of such MUC16xCD3 Program antibody and commercialization of such MUC16xCD3 Program antibody within the United States and (y) Sanofi will lead the commercialization of such MUC16xCD3 Program antibody outside of the United States.

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, subject to the same 10% reimbursement provision described above. In addition, we and Sanofi will share equally, on an ongoing basis, the development costs for a MUC16xCD3 Program antibody. The Amended IO Discovery Agreement will terminate as of the earlier of (a) Sanofi having elected to exercise or not exercise its options with respect to the BCMAxCD3 Program and the MUC16xCD3 Program in accordance with the terms of the Amended IO Discovery Agreement and (b) December 31, 2022.

In connection with the execution of the IO License and Collaboration Agreement in 2015, Sanofi made a $375.0 million non-refundable up-front payment to the Company. Under the terms of the IO License and Collaboration Agreement, the parties are co-developing 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. Refer to Note 18 for details regarding shares Sanofi elected to sell, and we elected to purchase (by issuing a credit towards the amount owed by Sanofi) to satisfy Sanofi's funding obligation related to Libtayo development costs and 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 (see Note 2 for related product sales information), while Sanofi leads commercialization activities outside of the United States and the parties equally share profits and losses from worldwide sales. Consequently, in 2019, we recorded $78.2 million, within Cost of goods sold, related to our obligation to pay Sanofi its share of Libtayo U.S. gross profits; such amounts were not material in 2018. As it relates to the commercialization of Libtayo outside of the United States, we recognize our share of profits and losses within Sanofi collaboration revenue.

In September 2018, the FDA approved Libtayo for the treatment of patients with metastatic or locally advanced cutaneous squamous cell carcinoma ("CSCC"), and Sanofi exercised its option to co-commercialize Libtayo in the United States. The Company will be entitled to a milestone payment of $375.0 million in the event that global sales of certain licensed products targeting PD-1 (including Libtayo), together with sales of any other products licensed under the IO License and Collaboration Agreement and sold for use in combination with any of such licensed products targeting PD-1, equal or exceed $2.0 billion in any consecutive twelve-month period. The amount of variable consideration related to such milestone is deemed to be constrained as of December 31, 2019, and therefore has not been included in the transaction price.

In August 2018, we and Sanofi entered into a license agreement with Bristol-Myers Squibb Company, E. R. Squibb & Sons, L.L.C., and Ono Pharmaceutical Co., Ltd. to obtain a license under certain patents owned and/or exclusively licensed by one or more of those parties that includes the right to develop and sell Libtayo. Under the agreement, we and Sanofi made an up-front payment of $20.0 million and are obligated to pay royalties of 8.0% on worldwide sales of Libtayo through December 31, 2023, and royalties

of 2.5% from January 1, 2024 through December 31, 2026. The up-front payment was shared, and the royalties are shared, equally by us and Sanofi.

Each party will have the right to co-commercialize licensed products in countries where it is not the lead commercialization party. The parties will share equally in profits and losses in connection with the commercialization of collaboration products. The Company is obligated to use commercially reasonable efforts to supply clinical requirements of each drug candidate under the IO License and Collaboration Agreement until commercial supplies of that IO drug candidate are being manufactured. With respect to each product candidate that enters development under the IO License and Collaboration Agreement, Sanofi or the Company may, by giving twelve months' notice, opt-out of further development and/or commercialization of the product, in which event the other party will retain exclusive rights to continue the development and/or commercialization of such product.

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

"Amounts recognized in connection with up-front payments received" in the Sanofi Collaboration Revenue table above includes recognition of deferred revenue from (i) the aggregate up-front payments received during 2015 and (ii) amounts received in connection with the termination of the 2015 IO Discovery Agreement (as described above). During 2018, we reduced our estimate of the total research and development costs expected to complete the contract, including in connection with the termination of the 2015 IO Discovery Agreement, and, as result, a cumulative catch-up adjustment of $135.0 million was recognized for the year ended December 31, 2018.

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



	As of December 31,
	2019			2018
Accounts receivable, net	$	(16.7	)	$	77.9
Deferred revenue	$	568.0		$	289.9

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement	$	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(92.7	)
Revenue recognized that was added to deferred revenue during the period	$	(48.4	)

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 December 31, 2019 was $1.138 billion. 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

EYLEA outside the United States



	Year Ended December 31,
Bayer EYLEA Collaboration Revenue	2019		2018		2017
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	1,091.4	$	992.3	$	802.3
Reimbursement of EYLEA development expenses	23.0		11.2		13.3
Other	74.4		73.6		58.7
	$	1,188.8	$	1,077.1	$	874.3

In 2006, the Company entered into a license and collaboration agreement with Bayer for the global development and commercialization outside the United States of EYLEA. All agreed-upon EYLEA development expenses incurred by the Company and Bayer, under a global development plan, are shared equally. The Company is also obligated to use commercially reasonable efforts to supply clinical and commercial bulk product of EYLEA. Bayer has the right to terminate the license and collaboration agreement without cause with at least six months' or twelve months' advance notice depending on defined circumstances at the time of termination. In the event of termination of the agreement for any reason, the Company retains all rights to EYLEA.

Bayer markets EYLEA outside the United States, where, for countries other than Japan, the companies share equally in profits and losses from sales of EYLEA. In Japan, the Company is entitled to receive a tiered percentage of between 33.5% and 40.0% of EYLEA net sales through 2021, and thereafter, the companies will share equally in profits and losses from the sales of EYLEA. Within the United States, the Company is responsible for commercialization of EYLEA and retains exclusive rights to all profits from such commercialization in the United States. The Company is obligated to reimburse Bayer out of its share of the collaboration profits (including the Company's percentage of sales of EYLEA in Japan) for 50% of the agreed-upon development expenses that Bayer has incurred in accordance with a formula based on the amount of development expenses that Bayer has incurred and the Company's share of the collaboration profits, or at a faster rate at the Company's option. The Company's contingent reimbursement obligation to Bayer was approximately $270 million as of December 31, 2019.

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. 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.

Within the United States, the Company will lead commercialization activities, and the parties will share equally in any profits and losses in connection with commercialization of fasinumab. In the territory outside the United States, Teva will lead commercialization activities and the Company will supply product to Teva at a tiered purchase price, which is calculated as a percentage of net sales of the product (subject to adjustment in certain circumstances). Unless terminated earlier in accordance with its provisions, the Teva Collaboration Agreement will continue to be in effect until such time as neither party is developing or commercializing fasinumab.

In 2017, the Company earned, and recognized as substantive milestones, development milestones of $25.0 million and $35.0 million, respectively, from Teva upon initiation of two Phase 3 trials. During 2018, the Company achieved a development milestone of $60.0 million. The Company is entitled to receive up to an aggregate of $340.0 million in additional development milestones and up to an aggregate of $1,890.0 million in contingent payments upon achievement of specified annual net sales amounts; the amount of variable consideration related to such milestones is deemed to be constrained as of December 31, 2019, and therefore has not been included in the transaction price.

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

The Company recognized $206.5 million, $244.6 million, and $221.5 million of revenue in 2019, 2018, and 2017, respectively, in connection with the Teva Collaboration Agreement.

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



	As of December 31,
	2019		2018
Accounts receivable (recorded within Prepaid expenses and other current assets)	$	21.2	$	28.8
Deferred revenue	$	114.4	$	194.5

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(82.1	)

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 December 31, 2019 was $267.1 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.

e. Other

In addition to the collaboration agreements discussed above, the Company has various other collaboration agreements that are not individually, or in the aggregate, significant to its operating results or financial condition at this time. Pursuant to the terms of those agreements, the Company may be required to pay, or it may receive, additional amounts upon the achievement of various development and commercial milestones which in the aggregate could be significant. The Company may also incur, or get reimbursed for, significant research and development costs if the related product candidate(s) were to advance to late stage clinical trials. In addition, if any products related to these collaborations are approved for sale, the Company may be required to pay, or it may receive, royalties on future sales. The payment or receipt of these amounts, however, is contingent upon the occurrence of various future events.

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements


•	Level 1 - Quoted prices in active markets for identical assets


•	Level 2 - Significant other observable inputs, such as 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


•	Level 3 - Significant other unobservable inputs



			Fair Value Measurements at Reporting Date
As of December 31, 2019	Fair Value		Level 1		Level 2
Available-for-sale debt securities:
Corporate bonds	$	3,988.1	—		$	3,988.1
U.S. government and government agency obligations	54.4		—		54.4
Sovereign bonds	27.3		—		27.3
Commercial paper	92.3		—		92.3
Certificates of deposit	72.4		—		72.4
Equity securities (unrestricted)	61.6		$	61.6	—
Equity securities (restricted)	557.2		557.2		—
	$	4,853.3	$	618.8	$	4,234.5

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

The Company held certain restricted equity securities as of December 31, 2019, including its investment in Alnylam (see Note 3), which are subject to transfer restrictions that expire at various dates through 2023.

The Company adopted ASU 2016-01 during the first quarter of 2018 (see Note 1); as a result, we recorded $118.3 million of net unrealized gains and $41.9 million of net unrealized losses on equity securities in Other income (expense), net for the years ended December 31, 2019 and 2018, respectively. During the year ended December 31, 2017, we recorded net unrealized gains of $14.7 million on equity securities in Other comprehensive income (loss).

In addition to the investments summarized in the table above, as of December 31, 2019 and 2018, the Company had $55.6 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 and License Agreements - Schedule of Significant Changes in Deferred Revenue Balances, Teva Collaboration (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Teva \| Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Revenue recognized that was included in deferred revenue at the beginning of the period	$ (82.1)

Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Deferred compensation	$ 519.7	$ 458.2
Fixed assets and intangible assets	192.0	107.8
Accrued expenses	75.9	53.3
Deferred revenue	22.0	20.2
Other	0.0	33.3
Total deferred tax assets	809.6	672.8
Valuation allowance	(7.0)	0.0
Deferred tax assets, net of valuation allowance	802.6	672.8
Deferred tax liabilities:
Other	(11.2)	(2.7)
Net deferred tax assets	$ 791.4	$ 670.1

Product Sales - Schedule of Concentration of Risk, by Risk Factor (Details) - Gross Sales Revenue - Customer concentration risk	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	57.00%	56.00%	51.00%
McKesson Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	33.00%	36.00%	29.00%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts
Concentration Risk [Line Items]
Concentration risk, percentage			19.00%

Collaboration and License Agreements (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Schedule of collaboration revenue

Net product sales consist of the following:



	Year Ended December 31,
Net Product Sales in the United States	2019		2018		2017
EYLEA	$	4,644.2	$	4,076.7	$	3,701.9
Libtayo	175.7		14.8		—
ARCALYST	14.5		14.7		16.6
	$	4,834.4	$	4,106.2	$	3,718.5



	Year Ended December 31,
Bayer EYLEA Collaboration Revenue	2019		2018		2017
Regeneron's net profit in connection with commercialization of EYLEA outside the United States	$	1,091.4	$	992.3	$	802.3
Reimbursement of EYLEA development expenses	23.0		11.2		13.3
Other	74.4		73.6		58.7
	$	1,188.8	$	1,077.1	$	874.3

The collaboration revenue we earned from Sanofi is detailed below:



	Year Ended December 31,
Sanofi Collaboration Revenue	2019			2018			2017
Antibody:
Reimbursement of research and development expenses	$	277.7		$	265.3		$	508.4
Reimbursement of commercialization-related expenses	479.9			417.2			368.8
Reimbursement for manufacturing of commercial supplies	206.7			127.6			35.1
Regeneron's share of profits (losses) in connection with commercialization of antibodies	209.3			(227.0		)	(442.6		)
Other	(1.5		)	(24.1		)	84.0
Total Antibody	1,172.1			559.0			553.7
Immuno-oncology:
Reimbursement of research and development expenses	163.0			311.8			240.0
Reimbursement of commercialization-related expenses	10.3			8.9			7.0
Amounts recognized in connection with up-front payments received	92.7			243.8			80.0
Other	(11.3		)	(12.4		)	(3.5		)
Total Immuno-oncology	254.7			552.1			323.5
	$	1,426.8		$	1,111.1		$	877.2

Schedule of accounts receivable and deferred revenue information



	As of December 31,
	2019		2018
Accounts receivable	$	272.7	$	138.2
Deferred revenue	$	337.2	$	236.1

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase due to shipments of commercial supplies to Sanofi	$	335.7
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(240.4	)

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



	As of December 31,
	2019		2018
Accounts receivable (recorded within Prepaid expenses and other current assets)	$	21.2	$	28.8
Deferred revenue	$	114.4	$	194.5

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(82.1	)

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



	As of December 31,
	2019			2018
Accounts receivable, net	$	(16.7	)	$	77.9
Deferred revenue	$	568.0		$	289.9

Significant changes in deferred revenue balances are as follows:



	Year Ended December 31, 2019
Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement	$	415.9
Revenue recognized that was included in deferred revenue at the beginning of the period	$	(92.7	)
Revenue recognized that was added to deferred revenue during the period	$	(48.4	)

Deferred revenue consists of the following:



	As of December 31,
	2019		2018
Current portion:
Received or receivable from Sanofi (see Note 3a)	$	395.5	$	246.7
Received or receivable from Bayer (see Note 3b)	49.2		44.4
Received or receivable from Teva (see Note 3c)	89.5		92.5
Other	57.5		68.9
	$	591.7	$	452.5
Noncurrent portion:
Received or receivable from Sanofi (see Note 3a)	$	509.7	$	279.3
Received or receivable from Bayer (see Note 3b)	73.8		45.1
Received or receivable from Teva (see Note 3c)	24.9		102.0
Other	10.6		37.8
	$	619.0	$	464.2

Collaboration and License Agreements - Teva Narrative (Details) - USD ($)	3 Months Ended										12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues	$ 2,169,500,000	$ 2,048,400,000	$ 1,933,700,000	$ 1,711,800,000	$ 1,927,800,000	$ 1,663,500,000	$ 1,608,000,000.0	$ 1,511,500,000			$ 7,863,400,000	$ 6,710,800,000	$ 5,872,200,000
Teva
Disaggregation of Revenue [Line Items]
Up-front payment received														$ 250,000,000.0
Revenue recognition, milestone method, revenue recognized									$ 35,000,000.0	$ 25,000,000.0
Development milestone achieved												60,000,000.0
Aggregate future development milestone payments the Company is eligible to receive											340,000,000.0
Collaborative arrangement, additional eligible aggregate payments											1,890,000,000.0
Revenues											206,500,000	$ 244,600,000	$ 221,500,000
Remaining performance obligation	$ 267,100,000										$ 267,100,000

Business Overview and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives of Property, Plant, and Equipment

The estimated useful lives of property, plant, and equipment are as follows:



Building and improvements		10–50 years
Laboratory and other equipment		3–10 years
Furniture and fixtures		5 years

Property, plant, and equipment consists of the following:



	As of December 31,
	2019			2018
Land	$	230.8		$	199.0
Building and improvements	1,683.4			1,507.2
Leasehold improvements	97.6			97.0
Construction in progress	644.8			469.6
Laboratory equipment	850.7			773.7
Computer equipment and software	183.7			145.8
Furniture, office equipment, and other	121.8			112.2
	3,812.8			3,304.5
Less, accumulated depreciation and amortization	(922.4		)	(728.7		)
	$	2,890.4		$	2,575.8

Net Income Per Share - Schedule of Antidilutive Securities Excluded From Computation (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares (in shares)	18.4	14.9	9.2

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 2,115.8	$ 2,444.4	$ 1,198.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	210.3	148.2	145.5
Non-cash compensation expense	464.3	427.4	507.3
Other non-cash items, net	(29.3)	12.1	63.5
Deferred taxes	(130.6)	(140.0)	318.8
Changes in assets and liabilities:
Increase in Sanofi, Bayer, and trade accounts receivable	(473.1)	(268.9)	(362.7)
Increase in inventories	(335.5)	(387.9)	(314.2)
Increase in prepaid expenses and other assets	(130.4)	(55.7)	(113.3)
Increase (decrease) in deferred revenue	294.0	(194.5)	(113.1)
Increase (decrease) in accounts payable, accrued expenses, and other liabilities	444.5	210.0	(23.2)
Total adjustments	314.2	(249.3)	108.6
Net cash provided by operating activities	2,430.0	2,195.1	1,307.1
Cash flows from investing activities:
Purchases of marketable and other securities	(3,202.4)	(1,845.5)	(1,277.2)
Sales or maturities of marketable securities	1,604.2	775.6	544.6
Capital expenditures	(429.6)	(383.1)	(272.6)
Other	0.0	(10.0)	0.0
Net cash used in investing activities	(2,027.8)	(1,463.0)	(1,005.2)
Cash flows from financing activities:
Proceeds in connection with finance lease liabilities		0.0	57.0
Payments in connection with finance lease liabilities		0.0	(19.9)
Proceeds from issuance of Common Stock	211.8	114.5	240.2
Payments in connection with Common Stock tendered for employee tax obligations	(188.0)	(187.2)	(301.7)
Repurchases of Common Stock	(275.9)	(4.4)	0.0
Net cash used in financing activities	(252.1)	(77.1)	(24.4)
Net increase in cash, cash equivalents, and restricted cash	150.1	655.0	277.5
Cash, cash equivalents, and restricted cash at beginning of period	1,480.2	825.2	547.7
Cash, cash equivalents, and restricted cash at end of period	1,630.3	1,480.2	825.2
Supplemental disclosure of cash flow information
Cash paid for interest (net of amounts capitalized)	25.0	22.3	18.7
Cash paid for income taxes	$ 342.3	$ 205.6	$ 754.8

Statement of Cash Flows (Tables)

12 Months Ended

Dec. 31, 2019

Supplemental Cash Flow Information [Abstract]

Schedule of restrictions on cash and cash equivalents

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



	December 31,
	2019		2018		2017
Cash and cash equivalents	$	1,617.8	$	1,467.7	$	812.7
Restricted cash included in Other noncurrent assets	12.5		12.5		12.5
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows	$	1,630.3	$	1,480.2	$	825.2

Inventories (Tables)

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

Schedule of inventory

Inventories consist of the following:



	As of December 31,
	2019		2018
Raw materials	$	216.3	$	226.8
Work-in-process	727.7		571.1
Finished goods	70.6		24.4
Deferred costs	400.9		328.9
	$	1,415.5	$	1,151.2

Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of option grants (Details) - Stock options	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	28.00%	29.00%	31.00%
Expected lives from grant date	5 years	4 years 10 months 24 days	5 years 1 month 6 days
Expected dividend yield	0.00%	0.00%	0.00%
Risk-free interest rate	1.74%	2.69%	2.16%

Business Overview and Summary of Significant Accounting Policies - Narrative (Details)		12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
Number of business segments \| segment		1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for doubtful accounts receivable, current		$ 0	$ 0
Provision for doubtful accounts		$ 0	0	$ 0
Period prior to products expiration date for returns accepted		3 months
Period up to products expiration date for returns accepted		6 months
Collaboration revenue for non-refundable up-front payments, development milestones, and payments for development activities, for which used an input method		$ 497,600,000	$ 837,700,000
Three individual customers \| Customer concentration risk \| Gross Sales Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage		97.00%	99.00%
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset					$ 33,200,000
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue	$ 143,400,000
Accounting Standards Update 2014-09 \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment upon adoption of new accounting standards	143,400,000
Accounting Standards Update 2016-01 \| Equity Securities \| Unrestricted
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax	6,600,000
Accounting Standards Update 2016-01 \| Retained Earnings \| Equity Securities \| Unrestricted
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment upon adoption of new accounting standards	$ 6,600,000

Commitments and Contingencies - Analysis of lease liability maturities, prior to ASC 842 adoption (Details) $ in Millions	Dec. 31, 2018 USD ($)
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

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								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income - basic and diluted	$ 792.0	$ 669.6	$ 193.1	$ 461.1	$ 820.4	$ 594.7	$ 551.4	$ 478.0	$ 2,115.8	$ 2,444.4	$ 1,198.5
Weighted average shares outstanding - basic (in shares)									109.2	107.9	106.3
Effect of dilutive securities:
Weighted average shares - diluted (in shares)									114.6	114.8	115.9
Net income per share - basic (in dollars per share)	$ 7.25	$ 6.12	$ 1.77	$ 4.23	$ 7.58	$ 5.50	$ 5.12	$ 4.44	$ 19.38	$ 22.65	$ 11.27
Net income per share - diluted (in dollars per share)	$ 6.93	$ 5.86	$ 1.68	$ 3.99	$ 7.15	$ 5.17	$ 4.82	$ 4.16	$ 18.46	$ 21.29	$ 10.34
Stock options
Effect of dilutive securities:
Effect of dilutive securities (in shares)									5.4	6.9	9.1
Restricted stock
Effect of dilutive securities:
Effect of dilutive securities (in shares)									0.0	0.0	0.5

Marketable Securities - Narrative (Details)	12 Months Ended
Marketable Securities - Narrative (Details)	Dec. 31, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract]
Realized loss on sales of marketable securities	$ 0

Statement of Cash Flows - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 1,617.8	$ 1,467.7	$ 812.7
Restricted cash included in Other noncurrent assets	12.5	12.5	12.5
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows	$ 1,630.3	$ 1,480.2	$ 825.2	$ 547.7

(Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of amounts recognized in the Condensed Consolidated Balance Sheet



		December 31,
	Classification	2019
Finance lease right-of-use assets	Property, plant, and equipment, net⁽¹⁾	$	660.1
Finance lease liabilities	Finance lease liabilities (noncurrent)	$	713.9

⁽¹⁾ Finance lease right-of-use assets are recorded net of accumulated amortization of $76.1 million as of December 31, 2019.

Schedule of lease cost and other information

Finance lease costs consist of the following:



	Year Ended December 31, 2019
Amortization of right-of-use assets	$	14.4
Interest on lease liabilities	27.6
	$	42.0

Other information related to our finance lease includes the following:



	December 31,
	2019
Remaining lease term (in years)	2.17
Discount rate	3.05	%

Schedule of maturities of operating lease liabilities

The following is a maturity analysis of our lease liabilities as of December 31, 2019:



	Operating Leases			Finance Leases
2020	$	7.6		$	22.2
2021	6.6			21.9
2022	3.3			725.4
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	26.1			769.5
Imputed interest	(2.5		)	(50.1		)
Debt financing costs	—			(5.5		)
Total lease liabilities	$	23.6		$	713.9

Schedule of maturities of finance lease liabilities

The following is a maturity analysis of our lease liabilities as of December 31, 2019:



	Operating Leases			Finance Leases
2020	$	7.6		$	22.2
2021	6.6			21.9
2022	3.3			725.4
2023	2.0			—
2024	2.3			—
Thereafter	4.3			—
Total undiscounted lease payments	26.1			769.5
Imputed interest	(2.5		)	(50.1		)
Debt financing costs	—			(5.5		)
Total lease liabilities	$	23.6		$	713.9

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

Collaboration and License Agreements - Schedule of Significant Changes in Deferred Revenue Balances, Antibody Collaboration (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Increase (decrease) in deferred revenue	$ 294.0	$ (194.5)	$ (113.1)
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Increase (decrease) in deferred revenue	335.7
Revenue recognized that was included in deferred revenue at the beginning of the period	$ (240.4)

Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 4,206.3	$ 3,026.6
Unrealized Gains	28.5	1.0
Unrealized Losses	(0.3)	(18.4)
Fair Value	4,234.5	3,009.2
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	3,960.5	2,734.8
Unrealized Gains	27.8	1.0
Unrealized Losses	(0.2)	(17.4)
Fair Value	3,988.1	2,718.4
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	54.3	110.4
Unrealized Gains	0.2	0.0
Unrealized Losses	(0.1)	(1.0)
Fair Value	54.4	109.4
Sovereign bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	26.9	7.6
Unrealized Gains	0.4	0.0
Unrealized Losses	0.0	0.0
Fair Value	27.3	7.6
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	92.3	113.8
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	92.3	113.8
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	72.3	60.0
Unrealized Gains	0.1	0.0
Unrealized Losses	0.0	0.0
Fair Value	$ 72.4	$ 60.0

Marketable Securities

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Marketable securities as of December 31, 2019 and 2018 consist of both available-for-sale debt securities of investment grade issuers (see below and Note 5) as well as equity securities of publicly traded companies (see Note 5).

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



	Amortized		Unrealized					Fair
As of December 31, 2019	Cost Basis		Gains		Losses			Value
Corporate bonds	$	3,960.5	$	27.8	$	(0.2	)	$	3,988.1
U.S. government and government agency obligations	54.3		0.2		(0.1		)	54.4
Sovereign bonds	26.9		0.4		—			27.3
Commercial paper	92.3		—		—			92.3
Certificates of deposit	72.3		0.1		—			72.4
	$	4,206.3	$	28.5	$	(0.3	)	$	4,234.5

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 December 31, 2019 mature at various dates through December 2024. The fair values of available-for-sale debt security investments by contractual maturity consist of the following:



	As of December 31,
	2019		2018
Maturities within one year	$	1,596.5	$	1,342.2
Maturities after one year through five years	2,638.0		1,667.0
	$	4,234.5	$	3,009.2

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 December 31, 2019	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	257.2	$	(0.2	)	$	41.1	$	—		$	298.3	$	(0.2	)
U.S. government and government agency obligations	17.3		(0.1		)	2.0		—			19.3		(0.1		)
	$	274.5	$	(0.3	)	$	43.1	$	—		$	317.6	$	(0.3	)

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 year ended December 31, 2019. Realized gains and losses on sales of marketable securities were not material for the years ended December 31, 2018 and 2017.

With respect to marketable securities, for the years ended December 31, 2019, 2018, and 2017, amounts reclassified from Accumulated other comprehensive income (loss) into Other income (expense), net were related to realized gains and losses on sales of securities (as described above).

Long-Term Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of transactions involving stock option awards

Transactions involving stock option awards during 2019 under the Company's Incentive Plans are summarized in the table below.



		Number of Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Intrinsic Value
Outstanding as of December 31, 2018		28,279,696		$	319.28
2019:	Granted	3,271,222		$	366.65
	Forfeited	(576,806	)	$	395.88
	Expired	(300,581	)	$	460.37
	Exercised	(2,064,254	)	$	103.51
Outstanding as of December 31, 2019		28,609,277		$	337.24	6.17	$	1,805.9

Vested and expected to vest as of December 31, 2019		27,524,704		$	335.73	6.06	$	1,800.5

Exercisable as of December 31, 2019		19,291,335		$	318.15	4.90	$	1,763.9

Schedule of weighted-average exercise prices and weighted-average grant-date fair values of options issued

The fair value of each option granted under the Company's Incentive Plans during these periods was estimated on the date of grant using the Black-Scholes option-pricing model.



	Number of Options Granted	Weighted-Average Exercise Price		Weighted-Average Fair Value
2019:
Exercise price equal to Market Price	3,271,222	$	366.65	$	100.80
2018:
Exercise price equal to Market Price	4,665,320	$	378.51	$	114.39
2017:
Exercise price equal to Market Price	4,235,015	$	383.56	$	118.70

Schedule of weighted-average values of assumptions used in computing fair value of option grants

The following table summarizes the weighted average values of the assumptions used in computing the fair value of option grants during 2019, 2018, and 2017.



	2019		2018		2017
Expected volatility	28	%	29	%	31	%
Expected lives from grant date	5.0 years		4.9 years		5.1 years
Expected dividend yield	0	%	0	%	0	%
Risk-free interest rate	1.74	%	2.69	%	2.16	%

Schedule of activity related to restricted stock awards



		Number of Shares/Units		Weighted-Average Grant Date Fair Value
Balance as of December 31, 2018		472,630		$	386.10
2019:	Granted	698,103		$	356.33
	Vested	(3,090	)	$	406.65
	Forfeited/Cancelled	(5,857	)	$	385.90
Balance as of December 31, 2019		1,161,786		$	368.16

Inventories - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory write-downs and reserves	$ 73.8	$ 12.5	$ 20.9

Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 274.5	$ 1,482.6
Unrealized Loss - Less than 12 months	(0.3)	(6.1)
Fair Value - 12 Months or Greater	43.1	900.7
Unrealized Loss - 12 Months or Greater	0.0	(12.3)
Fair Value - Total	317.6	2,383.3
Unrealized Loss - Total	(0.3)	(18.4)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	257.2	1,482.6
Unrealized Loss - Less than 12 months	(0.2)	(6.1)
Fair Value - 12 Months or Greater	41.1	801.6
Unrealized Loss - 12 Months or Greater	0.0	(11.3)
Fair Value - Total	298.3	2,284.2
Unrealized Loss - Total	(0.2)	(17.4)
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	17.3	0.0
Unrealized Loss - Less than 12 months	(0.1)	0.0
Fair Value - 12 Months or Greater	2.0	99.1
Unrealized Loss - 12 Months or Greater	0.0	(1.0)
Fair Value - Total	19.3	99.1
Unrealized Loss - Total	$ (0.1)	$ (1.0)

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 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 December 31, 2019	Cost Basis		Gains		Losses			Value
Corporate bonds	$	3,960.5	$	27.8	$	(0.2	)	$	3,988.1
U.S. government and government agency obligations	54.3		0.2		(0.1		)	54.4
Sovereign bonds	26.9		0.4		—			27.3
Commercial paper	92.3		—		—			92.3
Certificates of deposit	72.3		0.1		—			72.4
	$	4,206.3	$	28.5	$	(0.3	)	$	4,234.5

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:



	As of December 31,
	2019		2018
Maturities within one year	$	1,596.5	$	1,342.2
Maturities after one year through five years	2,638.0		1,667.0
	$	4,234.5	$	3,009.2

Fair Value and Unrealized Losses of Marketable Securities



	Less than 12 Months					12 Months or Greater					Total
As of December 31, 2019	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	257.2	$	(0.2	)	$	41.1	$	—		$	298.3	$	(0.2	)
U.S. government and government agency obligations	17.3		(0.1		)	2.0		—			19.3		(0.1		)
	$	274.5	$	(0.3	)	$	43.1	$	—		$	317.6	$	(0.3	)

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	)

Inventories

12 Months Ended

Dec. 31, 2019

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	As of December 31,
	2019		2018
Raw materials	$	216.3	$	226.8
Work-in-process	727.7		571.1
Finished goods	70.6		24.4
Deferred costs	400.9		328.9
	$	1,415.5	$	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 (see Note 1 for a further description of the related accounting policy). For the years ended December 31, 2019, 2018, and 2017, Cost of goods sold included inventory write-downs and reserves of $73.8 million, $12.5 million, and $20.9 million, respectively.

Business Overview and Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2019
Building and improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Building and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Laboratory and other equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Laboratory and other equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate		12.90%	4.30%	42.30%
Recognition of provisional charge	$ 326.2
Adjustment to provisional amount recorded			$ 68.0
Unrecognized tax benefits that would impact effective tax rate	$ 146.2	$ 210.8	$ 189.5	$ 146.2

Commitments and Contingencies - Leases narrative (Details) - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2017
Commitments and Contingencies Disclosure [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

Income Taxes - Schedule of income before income tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income before income taxes, United States	$ 2,011.2	$ 2,151.7	$ 1,964.7
Income before income taxes, Foreign	417.9	401.8	113.8
Income before income taxes	$ 2,429.1	$ 2,553.5	$ 2,078.5

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued payroll and related costs	$ 344.4	$ 261.8
Accrued clinical expenses	142.7	142.2
Accrued sales-related charges, deductions, and royalties	249.0	182.7
Income taxes payable	49.4	20.8
Other accrued expenses and liabilities	301.3	164.6
Accrued expenses and other current liabilities	$ 1,086.8	$ 772.1

Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale debt securities:
Available-for-sale debt securities	$ 4,234.5	$ 3,009.2
Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Total marketable securities	618.8	43.6
Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Total marketable securities	4,234.5	3,053.6
Unrestricted \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Available-for-sale debt securities		43.6
Equity securities	61.6
Unrestricted \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Available-for-sale debt securities		0.0
Equity securities	0.0
Restricted \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Equity securities	557.2	0.0
Restricted \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Equity securities	0.0	44.4
Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Total marketable securities	4,853.3	3,097.2
Estimate of Fair Value Measurement \| Unrestricted \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities		43.6
Equity securities	61.6
Estimate of Fair Value Measurement \| Restricted \| Measured on a recurring basis
Available-for-sale debt securities:
Equity securities	557.2	44.4
Corporate bonds
Available-for-sale debt securities:
Available-for-sale debt securities	3,988.1	2,718.4
Corporate bonds \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Corporate bonds \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Available-for-sale debt securities	3,988.1	2,718.4
Corporate bonds \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities	3,988.1	2,718.4
U.S. government and government agency obligations
Available-for-sale debt securities:
Available-for-sale debt securities	54.4	109.4
U.S. government and government agency obligations \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
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)
Available-for-sale debt securities:
Available-for-sale debt securities	54.4	109.4
U.S. government and government agency obligations \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities	54.4	109.4
Sovereign bonds
Available-for-sale debt securities:
Available-for-sale debt securities	27.3	7.6
Sovereign bonds \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Sovereign bonds \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Available-for-sale debt securities	27.3	7.6
Sovereign bonds \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities	27.3	7.6
Commercial paper
Available-for-sale debt securities:
Available-for-sale debt securities	92.3	113.8
Commercial paper \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Commercial paper \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Available-for-sale debt securities	92.3	113.8
Commercial paper \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities	92.3	113.8
Certificates of deposit
Available-for-sale debt securities:
Available-for-sale debt securities	72.4	60.0
Certificates of deposit \| Measured on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Certificates of deposit \| Measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Available-for-sale debt securities:
Available-for-sale debt securities	72.4	60.0
Certificates of deposit \| Estimate of Fair Value Measurement \| Measured on a recurring basis
Available-for-sale debt securities:
Available-for-sale debt securities	$ 72.4	$ 60.0