Regeneron Pharmaceuticals (REGN) 10-K 5 Feb 24 2023 FY Annual report Financial data

Cover

Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Jan. 25, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	000-19034
Entity Registrant Name	REGENERON PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	NY
Entity Tax Identification Number	13-3444607
Entity Address, Address Line One	777 Old Saw Mill River Road
Entity Address, City or Town	Tarrytown
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10591-6707
City Area Code	914
Local Phone Number	847-7000
Title of 12(b) Security	Common Stock - par value $.001 per share
Trading Symbol	REGN
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 76.7
Documents Incorporated by Reference	Specified portions of the Registrant's definitive proxy statement to be filed in connection with solicitation of proxies for its 2024 Annual Meeting of Shareholders are incorporated by reference into Part III of this Form 10-K. Exhibit index is located on pages 92 to 96 of this filing.
Entity Central Index Key	0000872589
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Class A Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		1,818,146
Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		107,943,750

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Florham Park, New Jersey

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) shares in Millions, $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 2,730	$ 3,105.9
Marketable securities	8,114.8	4,636.4
Accounts receivable, net	5,667.3	5,328.7
Inventories	2,580.5	2,401.9
Prepaid expenses and other current assets	386.6	411.2
Total current assets	19,479.2	15,884.1
Marketable securities	5,396.5	6,591.8
Property, plant, and equipment, net	4,146.4	3,763
Intangible assets, net	1,038.6	915.5
Deferred tax assets	2,575.4	1,723.7
Other noncurrent assets	444.1	336.4
Total assets	33,080.2	29,214.5
Current liabilities:
Accounts payable	606.6	589.2
Accrued expenses and other current liabilities	2,357.9	2,074.2
Deferred revenue	458.9	477.9
Total current liabilities	3,423.4	3,141.3
Long-term debt	1,982.9	1,981.4
Finance lease liabilities	720	720
Deferred revenue	126.7	69.8
Other noncurrent liabilities	854.1	638
Total liabilities	7,107.1	6,550.5
Commitments and contingencies
Stockholders' equity:
Preferred Stock, par value $.01 per share; 30.0 shares authorized; shares issued and outstanding - none	0	0
Additional paid-in capital	11,354	9,949.3
Retained earnings	27,260.3	23,306.7
Accumulated other comprehensive loss	(80.9)	(238.8)
Treasury Stock, at cost; 25.5 shares in 2023 and 22.6 shares in 2022	(12,560.4)	(10,353.3)
Total stockholders' equity	25,973.1	22,664
Total liabilities and stockholders' equity	33,080.2	29,214.5
Class A Stock
Stockholders' equity:
Common stock	$ 0	$ 0
Common Stock, shares issued (in shares)	1.8	1.8
Common Stock
Stockholders' equity:
Common stock	$ 0.1	$ 0.1
Common Stock, shares issued (in shares)	133.1	130.4

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
LIABILITIES AND STOCKHOLDERS' EQUITY
Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, shares authorized (in shares)	30,000,000	30,000,000
Preferred Stock, shares issued (in shares)	0	0
Preferred Stock, shares outstanding (in shares)	0	0
Treasury stock (in shares)	25,500,000	22,600,000
Class A Stock
LIABILITIES AND STOCKHOLDERS' EQUITY
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	40,000,000	40,000,000
Common Stock, shares issued (in shares)	1,800,000	1,800,000
Common Stock, shares outstanding (in shares)	1,800,000	1,800,000
Common Stock
LIABILITIES AND STOCKHOLDERS' EQUITY
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	320,000,000	320,000,000
Common Stock, shares issued (in shares)	133,100,000	130,400,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Revenue from contract with customer	$ 13,117.2	$ 12,172.9	$ 16,071.7
Expenses:
Research and development	4,439	3,592.5	2,860.1
Acquired in-process research and development	186.1	255.1	48
Selling, general, and administrative	2,631.3	2,115.9	1,824.9
Other operating (income) expense, net	(2.1)	(89.9)	(45.6)
Total expenses	9,070.1	7,434	7,124.9
Income from operations	4,047.1	4,738.9	8,946.8
Other income (expense):
Other income (expense), net	225.2	179.3	436.3
Interest expense	(73)	(59.4)	(57.3)
Total other income (expense)	152.2	119.9	379
Income before income taxes	4,199.3	4,858.8	9,325.8
Income tax expense	245.7	520.4	1,250.5
Net income	$ 3,953.6	$ 4,338.4	$ 8,075.3
Net income per share - basic (in dollars per share)	$ 37.05	$ 40.51	$ 76.40
Net income per share - diluted (in dollars per share)	$ 34.77	$ 38.22	$ 71.97
Weighted average shares outstanding - basic (in shares)	106.7	107.1	105.7
Weighted average shares outstanding - diluted (in shares)	113.7	113.5	112.2
Statements of Comprehensive Income
Net income	$ 3,953.6	$ 4,338.4	$ 8,075.3
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on debt securities	158.2	(213.6)	(56.4)
Loss on foreign currency translation	(0.3)	0	0
Unrealized gain on cash flow hedges	0	1	0.9
Comprehensive income	4,111.5	4,125.8	8,019.8
Net product sales
Revenues:
Revenue from contract with customer	7,078	6,893.7	12,117.2
Expenses:
Cost of goods sold and of collaboration and contract manufacturing	932.1	800	1,773.1
Collaboration revenue
Revenues:
Revenue from contract with customer	5,503.1	4,914.1	3,673.3
Other revenue
Revenues:
Revenue from contract with customer	536.1	365.1	281.2
Cost of collaboration and contract manufacturing
Expenses:
Cost of goods sold and of collaboration and contract manufacturing	$ 883.7	$ 760.4	$ 664.4

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Class A Stock	Class A Stock Common Stock
Beginning Balance (in shares) at Dec. 31, 2020		121.5						1.8
Beginning Balance, treasury (in shares) at Dec. 31, 2020						(16.4)
Beginning Balance at Dec. 31, 2020	$ 11,025.3	$ 0.1	$ 6,716.2	$ 10,893	$ 29.3	$ (6,613.3)		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)		6.2
Issuance of Common Stock for equity awards granted under long-term incentive plans	1,676		1,676
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)		(1.5)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(944.6)		(944.6)
Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares)						0.1
Issuance/distribution of Common Stock for 401(k) Savings Plan	48.1		40.7			$ 7.4
Repurchases of Common Stock (in shares)						(3.1)
Repurchases of Common Stock	(1,655)					$ (1,655)
Stock-based compensation charges	599.2		599.2
Net income	8,075.3			8,075.3
Other comprehensive income (loss), net of tax	(55.5)				(55.5)
Ending Balance (in shares) at Dec. 31, 2021		126.2						1.8
Beginning Ending, treasury (in shares) at Dec. 31, 2021						(19.4)
Ending Balance at Dec. 31, 2021	18,768.8	$ 0.1	8,087.5	18,968.3	(26.2)	$ (8,260.9)		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)		4.8
Issuance of Common Stock for equity awards granted under long-term incentive plans	1,517.4		1,517.4
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares)		(0.6)
Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations	(445.7)		(445.7)
Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares)						0.1
Issuance/distribution of Common Stock for 401(k) Savings Plan	59.7		52.3			$ 7.4
Repurchases of Common Stock (in shares)						(3.3)
Repurchases of Common Stock	(2,099.8)					$ (2,099.8)
Stock-based compensation charges	737.8		737.8
Net income	4,338.4			4,338.4
Other comprehensive income (loss), net of tax	$ (212.6)				(212.6)
Ending Balance (in shares) at Dec. 31, 2022		130.4					1.8	1.8
Beginning Ending, treasury (in shares) at Dec. 31, 2022	(22.6)					(22.6)
Ending Balance at Dec. 31, 2022	$ 22,664	$ 0.1	9,949.3	23,306.7	(238.8)	$ (10,353.3)		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares)		3.5
Issuance of Common Stock for equity awards granted under long-term incentive plans	1,152.2		1,152.2
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	(708.4)		(708.4)
Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares)						0.1
Issuance/distribution of Common Stock for 401(k) Savings Plan	74.1		66.6			$ 7.5
Repurchases of Common Stock (in shares)						(3)
Repurchases of Common Stock	(2,214.6)					$ (2,214.6)
Stock-based compensation charges	894.3		894.3
Net income	3,953.6			3,953.6
Other comprehensive income (loss), net of tax	$ 157.9				157.9
Ending Balance (in shares) at Dec. 31, 2023		133.1					1.8	1.8
Beginning Ending, treasury (in shares) at Dec. 31, 2023	(25.5)					(25.5)
Ending Balance at Dec. 31, 2023	$ 25,973.1	$ 0.1	$ 11,354	$ 27,260.3	$ (80.9)	$ (12,560.4)		$ 0

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income	$ 3,953.6	$ 4,338.4	$ 8,075.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	421	341.4	286.2
Stock-based compensation expense	885	725	601.7
Losses (gains) on marketable and other securities, net	266.4	36.8	(387)
Other non-cash items, net	(0.1)	368	568.7
Deferred income taxes	(837.8)	(746.4)	(147.1)
Acquired in-process research and development in connection with asset acquisition	0	195	0
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	(338.8)	707.8	(1,927.4)
Increase in inventories	(271.7)	(696.5)	(494.3)
Increase in prepaid expenses and other assets	(120.1)	(148.6)	(240.7)
Increase (decrease) in deferred revenue	37.9	32.4	(120.2)
Increase (decrease) in accounts payable, accrued expenses, and other liabilities	598.6	(138.4)	866.1
Total adjustments	640.4	676.5	(994)
Net cash provided by operating activities	4,594	5,014.9	7,081.3
Cash flows from investing activities:
Purchases of marketable and other securities	(11,646)	(7,487.9)	(7,048.1)
Sales or maturities of marketable and other securities	9,442.2	5,550.5	2,215.3
Capital expenditures	(718.6)	(590.1)	(551.9)
Payments for Libtayo intangible asset	(207.8)	(1,026.8)	0
Acquisitions, net of cash acquired	(54.9)	(230.3)	0
Net cash used in investing activities	(3,185.1)	(3,784.6)	(5,384.7)
Cash flows from financing activities:
Proceeds from issuance of Common Stock	1,145.5	1,519.5	1,672.3
Payments in connection with Common Stock tendered for employee tax obligations	(700.6)	(445.7)	(1,032.7)
Repurchases of Common Stock	(2,235)	(2,082.8)	(1,645.4)
Net cash used in financing activities	(1,790.1)	(1,009)	(1,005.8)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(0.4)	0	0
Net (decrease) increase in cash, cash equivalents, and restricted cash	(381.6)	221.3	690.8
Cash, cash equivalents, and restricted cash at beginning of period	3,119.4	2,898.1	2,207.3
Cash, cash equivalents, and restricted cash at end of period	2,737.8	3,119.4	2,898.1
Supplemental disclosure of cash flow information
Cash paid for interest (net of amounts capitalized)	73.1	53.7	55.8
Cash paid for income taxes	$ 870.3	$ 1,502.4	$ 1,218.4

Business Overview and Summary o

Business Overview and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Business Overview and Summary of Significant Accounting Policies	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 invents, develops, manufactures, and commercializes medicines for people with serious diseases. The Company's products and product candidates in development are designed to help patients with eye diseases, allergic and inflammatory diseases, cancer, cardiovascular and metabolic diseases, hematologic conditions, infectious diseases, and rare diseases. The Company's research and development efforts have led to eleven products that have received marketing approval by the U.S. Food and Drug Administration ("FDA"). In addition, REGEN-COV ® was authorized under an Emergency Use Authorization ("EUA") from November 2020 until January 2022 when the EUA was revised to exclude its use in geographic regions where infection or exposure is likely due to a variant that is not susceptible to the treatment; as a result, REGEN-COV is not currently authorized for use in any U.S. states, territories, or jurisdictions. 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 serious diseases. The Company's business is subject to certain risks including, but not limited to, uncertainties relating to conducting research activities, product development, obtaining regulatory approvals, 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. 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 collaborator (see Note 3) and customer accounts receivable are significant. As of December 31, 2023 and 2022, two individual customers accounted for 83% and 86% of the Company's net trade accounts receivable balances, respectively. The Company has contractual payment terms with each of its collaborators and customers, and the Company monitors their financial performance and credit worthiness so that it can properly assess and respond to any changes in their credit profile. As of December 31, 2023 and 2022, there were no write-offs and allowances of accounts receivable related to credit risk for the Company's collaborators or customers. 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 diversification. The Company invests its cash primarily in debt securities. The Company considers its 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. 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 have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, a loss is recognized in net income, whereas if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss). The Company also has investments in equity securities that are carried at fair value with changes in fair value recognized within other income (expense), net. The Company has elected to measure certain equity investments it holds that do not have readily determinable fair values at cost less impairment, if any, and adjusts for observable price changes in orderly transactions for identical or similar investments of the same issuer within other income (expense), net. Accounts Receivable The Company's trade accounts receivable arise from product sales and represent amounts due from its customers. 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 allowances 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 allowance. 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 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 within income from 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. Leases The Company determines 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. The Company may include options to extend or terminate a lease within the lease term when it is reasonably certain that it will exercise that option. The Company accounts for lease components (e.g., rental payments) separately from non-lease components (e.g., common area maintenance costs). Lease liabilities are recognized at the lease commencement date based on the present value of the remaining lease payments, discounted using the rate implicit in the lease. For leases where an implicit rate is not readily determinable, the Company uses its 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. Acquisitions The Company makes a determination whether a transaction should be accounted for as a business combination or as an asset acquisition. In a business combination, the acquisition method of accounting generally requires that the assets acquired and liabilities assumed be recorded as of the date of the acquisition at their respective fair values. Amounts allocated to acquired in-process research and development are capitalized as indefinite-lived intangible assets. Any excess of the purchase price (consideration transferred) over the fair values of net assets acquired is recorded as goodwill. In a business combination, contingent consideration obligations are recorded at fair value as of the acquisition date and remeasured each subsequent reporting period until the contingencies have been resolved, with any changes in fair value recorded in Other operating (income) expense, net. If it is determined that the assets acquired do not meet the definition of a business, or if substantially all of the fair value of the assets acquired are concentrated in a single identifiable asset, then the transaction is accounted for as an asset acquisition rather than a business combination. In an asset acquisition, assets acquired are recorded at cost, goodwill is not recognized, and acquired in-process research and development with no alternative future use is charged to expense. Intangible Assets Intangible assets acquired in a business combination are recorded at fair value, while intangible assets acquired in connection with an asset acquisition are recorded at cost. Payments to acquire intangible assets in an asset acquisition may include up-front payments and contingent consideration. With regard to contingent consideration in an asset acquisition, the Company recognizes regulatory milestones upon achievement, royalties in the period in which the underlying sales occur, and sales-based milestones when the milestone is deemed probable by the Company of being achieved. If contingent consideration is recognized subsequent to the acquisition date in an asset acquisition, the amount of such consideration is recorded as an addition to the cost basis of the intangible asset with a cumulative catch-up adjustment for amortization expense as if the additional amount of consideration had been accrued from the outset of the acquisition. Indefinite-lived intangible assets are subject to impairment testing until completion or abandonment of the associated research and development efforts. Definite-lived intangible assets are amortized to Cost of goods sold over the estimated useful lives of the assets based on the pattern in which the economic benefits of the intangible assets are consumed; if that pattern cannot be reliably determined, a straight-line basis is used. Intangible assets are reviewed for recoverability whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. If an indicator of impairment exists, the Company compares the projected undiscounted cash flows to be generated by the asset to the intangible asset's carrying amount. If the projected undiscounted cash flows of the intangible asset are less than the carrying amount, the intangible asset is written down to its fair value in the period in which the impairment occurs. Product Revenue Revenue from product sales is recognized at a point in time when the Company's customer is deemed to have obtained control of the product, which generally occurs upon receipt or acceptance by its customer. The amount of revenue the Company recognizes from product sales may vary 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, the Company estimates, utilizing the expected value method, the amount of variable consideration to which the Company will be entitled. This estimate is based upon contracts with customers, healthcare providers, payors, 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: The Company's rebates include amounts paid to managed care organizations, group purchasing organizations, state Medicaid programs, and other rebate programs. The Company estimates reductions to product sales for each type of rebate and records an allowance for rebates in the same period in which the related product sales are recognized. The Company's liability for rebates consists of estimates for claims related to the current and prior periods that have not been paid and estimates for claims that will be made related to product that exists in the distribution channel at the end of the period. • Chargebacks and Discounts: The Company's reserves related to discounted pricing to eligible physicians, Veterans' Administration ("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 discounted selling price to the qualified healthcare providers. The Company estimates reductions to product sales for each type of chargeback and records an allowance for chargebacks in the same period that the related product sales are recognized. The Company's reserve for chargebacks consists of amounts for which it expects to issue credit based on expected sales by its customers to qualified healthcare providers and chargebacks that customers have claimed but for which the Company has not yet issued credit. • 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's other sales-related deductions include co-pay assistance programs and product returns. The Company estimates and records other sales-related deductions generally based on gross sales, written contracts, and other relevant factors. Consistent with industry practice, the Company generally offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product's 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, 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. Collaborative Arrangements The Company has entered into various collaborative arrangements to research, develop, manufacture, and commercialize products and/or product candidates. Although each of these arrangements is unique in nature, such arrangements involve a joint operating activity where both parties are active participants in the activities of the collaboration and exposed to significant risks and rewards dependent on the commercial success of the activities. In arrangements where the Company does not deem its collaborator to be its customer, payments to and from its collaborator are presented in the Company's statement of operations based on the nature of our business operations, the nature of the arrangement, including the contractual terms, and the nature of the payments. In general, the presentation of such amounts is summarized below. Nature/Type of Payment Statement of Operations Presentation Regeneron's share of profits or losses in connection with commercialization of products Collaboration revenue Reimbursement for manufacturing of commercial supplies Collaboration revenue Royalties and/or sales-based milestones earned Collaboration revenue Reimbursement of Regeneron's research and development expenses Reduction to Research and development expenses Regeneron's obligation for its share of collaborator's research and development expenses Research and development expense Up-front/opt-in and development milestone payments to collaborators Acquired in-process research and development expense Reimbursement of Regeneron's commercialization-related expenses Reduction to Selling, general, and administrative expense Regeneron's obligation for its share of collaborator's commercialization-related expenses Selling, general, and administrative expense Regeneron's obligation to pay collaborator for its share of gross profits when Regeneron is deemed to be the principal Cost of goods sold Up-front and development milestones earned (when there is a combined unit of account which includes a license and providing research and development services) Other operating income In agreements involving multiple goods or services promised to be transferred to the Company's collaborator, the Company assesses, at the inception of the contract, whether each promise represents a separate obligation (i.e., is "distinct"), or whether such promises should be combined as a single unit of account. When the Company has a combined unit of account which includes a license and providing research and development services to its collaborator, recognition of up-front payments and development milestones earned from its collaborator is deferred (as a liability) and recognized over the development period (i.e., over time) typically using an input method on the basis of the Company's research and development costs incurred relative to the total expected cost which determines the extent of the Company's progress toward completion. The Company reviews its estimates each period and makes revisions to such estimates as necessary. When the Company is entitled to reimbursement of all or a portion of the expenses (e.g., research and development expenses) that it incurs under a collaboration, it records those reimbursable amounts in the period in which such costs are incurred. If the Company's collaborator performs research and development work or commercialization-related activities and the parties share the related costs, the Company also recognizes, as expense (e.g., research and development expense or selling, general, and administrative expense, as applicable) in the period when its collaborator incurs such expenses, the portion of the collaborator's expenses that the Company is obligated to reimburse. The Company's collaborators provide the Company with estimated expenses for the most recent fiscal quarter. The estimates are revised, if necessary, in subsequent periods if actual expenses differ from those estimates. 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. In arrangements where the Company: • supplies commercial product to its collaborator, the Company may be reimbursed for its manufacturing costs as commercial product is shipped to the collaborator (however, recognition of such cost reimbursements may be deferred until the product is sold by the Company's collaborator to third-party customers); • shares in any profits or losses arising from the commercialization of such products, the Company records its share of the variable consideration, representing net product sales less cost of goods sold and shared commercialization and other expenses, in the period in which such underlying sales occur and costs are incurred by the collaborator; • receives royalties and/or sales-based milestone payments from its collaborator, the Company recognizes such amounts in the period earned. The Company's collaborators provide it with estimates of product sales and the Company's share of profits or losses, as applicable, for each quarter. The estimates are revised, if necessary, in subsequent periods if the Company's actual share of profits or losses differ from those estimates. Research and Development Expenses Research and development expenses include costs 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, clinical trial expenses, the cost of services provided by outside contractors, including services related to the Company's clinical trials, the cost of manufacturing drug for use in research and development, 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. Costs associated with research and development are expensed. For each clinical trial that the Company conducts, certain clinical trial costs are expensed immediately, while others are expensed over time based on the expected total number of patients in the trial, the rate at which patients enter and remain in 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, the Company accrues and recognizes expenses in an amount based on its estimate of the remaining noncancelable obligations associated with the winding-down of the clinical trial, including any applicable penalties. Stock-based Compensation The Company recognizes stock-based compensation expense for equity grants under the Company's long-term incentive plans (including stock options, restricted stock awards, and restricted stock units (both time-based and performance-based)) 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. 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. In addition, the Company reassesses its forfeiture rate assumptions at least annually, considering both historical forfeiture experience and an estimate of future forfeitures for currently outstanding unvested awards. The Company uses the Black-Scholes model to compute the estimated fair value of stock option awards. Additionally, the Company uses a Monte Carlo simulation to compute the estimated fair value of performance-based restricted stock units that are subject to vesting based on the Company’s attainment of pre-established criteria that include a market condition. For performance-based restricted stock units that contain a performance condition, the Company recognizes stock-based compensation expense if and when the Company determines that it is probable the performance condition will be achieved (based on the number of shares expected to be vested and issued). The Company reassesses the probability of achievement at each reporting period and adjusts compensation cost, as necessary. If there are any changes in the Company's probability assessment, the Company recognizes a cumulative catch-up adjustment in the period of the change in estimate, with the remaining unrecognized expense recognized prospectively over the remaining requisite service period. If the Company subsequently determines that the performance criteria are not met or are not expected to be met, any amounts previously recognized as compensation expense are reversed in the period when such determination is made. 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 are recognized 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. Deferred tax assets and liabilities are determined as 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. The Company recognizes the financial statement effects of a tax position when management's assessment is that there is more than a 50% probability that the position will be sustained upon examination by a taxing authority based upon its technical merits. Uncertain tax positions are recorded based upon 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, the effective settlement of matters subject to audit, information obtained during in-process audit activities, and changes in facts or circumstances related to a tax position. The Company adjusts the amount of the liability to reflect any subsequent changes in the relevant facts and circumstances surrounding the uncertain tax 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 outstanding stock options and unvested restricted stock under the Company's long-term incentive plans, which are included under the treasury stock method when dilutive. Recently Issued Accounting Standards In November 2023, the FASB issued Accounting Standards Update No. 2023-07, Segment Reporting - Improvements to Reportable Segment Disclosures . The amendments require disclosure of incremental segment information on an annual and interim basis. The amendments also require companies with a single reportable segment to provide all disclosures required by this amendment and all existing segment disclosures in Accounting Standards Codification 280, Segment Reporting . The amendments are effective for fiscal years beginning after December 15, 2023, and interim periods beginning after December 15, 2024. The Company does not expect the adoption of the amendments to have a significant impact on its financial statements. In December 2023, the FASB issued Accounting Standards Update No. 2023-09, Income Taxes - Improvements to Income Tax Disclosures . The amendments require (i) enhanced disclosures in connection with an entity's effective tax rate reconciliation and (ii) income taxes paid disaggregated by jurisdiction. The amendments are effective for annual periods beginning after December 15, 2024. The Company does not expect the adoption of the amendments to have a significant impact on its financial statements.

Product Sales

Product Sales	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Product Sales	Product Sales Net product sales consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 EYLEA ® HD U.S. $ 165.8 $ — $ — EYLEA ® U.S. 5,719.6 6,264.6 5,792.3 Total EYLEA HD and EYLEA U.S. 5,885.4 6,264.6 5,792.3 Libtayo ®(a) U.S. 538.8 374.5 306.3 Libtayo (a) ROW (b) 324.3 73.0 — Total Libtayo Global 863.1 447.5 306.3 Praluent ® U.S. 182.4 130.0 170.0 REGEN-COV ®(c) U.S. — — 5,828.0 Evkeeza ® U.S. 77.3 48.6 18.4 Inmazeb ® U.S. 69.8 3.0 — ARCALYST ®(d) U.S. — — 2.2 $ 7,078.0 $ 6,893.7 $ 12,117.2 (a) Prior to July 1, 2022, Regeneron recorded net product sales of Libtayo in the United States and Sanofi recorded net product sales of Libtayo outside the United States. Effective July 1, 2022, the Company records global net product sales of Libtayo. See Note 3 for further details. (b) Rest of world ("ROW") (c) Net product sales of REGEN-COV in the United States relate to product sold in connection with the Company's agreements with the U.S. government. See Note 3 for further details. (d) Effective April 1, 2021, Kiniksa records net product sales of ARCALYST in the United States. Previously, the Company recorded net product sales of ARCALYST in the United States. As of December 31, 2023 and 2022, the Company had $3.888 billion and $3.586 billion, respectively, of trade accounts receivable that were recorded within Accounts receivable, net. 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, 2023, 2022, and 2021. Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows: Year Ended December 31, 2023 2022 2021 Besse Medical, a subsidiary of Cencora, Inc. 51 % 55 % 30 % McKesson Corporation 25 % 28 % 18 % U.S. government * * 43 % * Sales to the U.S. government 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. (In millions) Rebates, Chargebacks, Distribution- Other Sales- Total Balance as of December 31, 2020 $ 202.2 $ 77.2 $ 44.8 $ 324.2 Provisions 1,047.1 363.6 150.4 1,561.1 Credits/payments (1,034.7) (360.8) (127.6) (1,523.1) Balance as of December 31, 2021 214.6 80.0 67.6 362.2 Provisions 1,537.3 431.1 141.1 2,109.5 Credits/payments (1,398.0) (399.7) (127.2) (1,924.9) Balance as of December 31, 2022 353.9 111.4 81.5 546.8 Provisions 2,074.5 439.2 155.3 2,669.0 Credits/payments (1,972.7) (388.3) (157.5) (2,518.5) Balance as of December 31, 2023 $ 455.7 $ 162.3 $ 79.3 $ 697.3

Collaboration, License, and Oth

Collaboration, License, and Other Agreements	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Collaboration, License, and Other Agreements	Collaboration, License, and Other Agreements a. Sanofi Amounts recognized in the Company's Statements of Operations in connection with its collaborations with Sanofi are detailed below: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Antibody: Regeneron's share of profits in connection with commercialization of antibodies Collaboration revenue $ 3,136.5 $ 2,082.0 * $ 1,363.0 Sales-based milestones earned Collaboration revenue $ 50.0 $ 100.0 $ 50.0 Reimbursement for manufacturing of commercial supplies Collaboration revenue $ 613.0 $ 633.7 $ 488.8 Other Collaboration revenue $ — $ 28.7 $ — Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (83.7) $ 43.0 $ 129.2 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ 534.4 $ 437.4 $ 320.5 Immuno-oncology (a) : Regeneron's share of profits (losses) in connection with commercialization of Libtayo outside the United States Collaboration revenue $ — $ 6.7 $ (13.6) Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ — $ 4.6 $ 14.0 Reimbursement of R&D expenses Reduction of R&D expense $ — $ 42.7 $ 85.1 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ — $ 41.4 $ 89.6 Regeneron's obligation for its share of Sanofi commercial expenses SG&A expense $ — $ (19.9) $ (36.3) Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits Cost of goods sold $ — $ (70.1) $ (133.0) Amounts recognized in connection with up-front payments received Other operating income $ — $ 35.1 $ 6.1 * Net of one-time payment of $56.9 million to Sanofi in connection with the amendment to the Antibody License and Collaboration Agreement (a) As described within the " Immuno-Oncology " section below, effective July 1, 2022, the Company obtained the exclusive right to develop, commercialize, and manufacture Libtayo worldwide. Antibody The Company is party to a global, strategic collaboration with Sanofi to research, develop, and commercialize fully human monoclonal antibodies (the "Antibody Collaboration"), which currently consists of Dupixent ® (dupilumab), Kevzara ® (sarilumab), and itepekimab . Under the terms of the Antibody License and Collaboration Agreement (the "LCA"), Sanofi is generally responsible for funding 80% to 100% of agreed-upon development costs. The Company is obligated to reimburse Sanofi for 30% to 50% of worldwide development expenses that were funded by Sanofi based on the Company's share of collaboration profits from commercialization of collaboration products. Under the terms of the LCA, the Company was required to apply 10% of its share of the profits from the Antibody Collaboration in any calendar quarter to reimburse Sanofi for these development costs. On July 1, 2022, an amendment to the LCA became effective, pursuant to which the percentage of the Company's share of profits used to reimburse Sanofi for such development costs increased from 10% to 20%. A portion of the value associated with the increase in reimbursement percentage was deemed to be contingent consideration attributable to the Company's acquisition of the Libtayo (cemiplimab) rights described within the " Immuno-Oncology " section below; this portion is recorded as an increase to the Libtayo intangible asset over time as the Company repays such development costs to Sanofi. The Company's contingent reimbursement obligation to Sanofi under the Antibody Collaboration was approximately $2.330 billion as of December 31, 2023. Sanofi leads commercialization activities for products under the Antibody Collaboration, subject to the Company's right to co-commercialize such products. The Company co-commercializes Dupixent in the United States and in certain countries outside the United States. The parties equally share profits 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). In addition to profit sharing, the Company was entitled to receive sales milestone payments from Sanofi. In 2023, the Company earned the final $50.0 million sales-based milestone from Sanofi, upon aggregate annual sales of antibodies outside the United States (including Praluent, which was previously included in the LCA) exceeding $3.0 billion on a rolling twelve-month basis. In 2022, the Company earned two $50.0 million sales-based milestones from Sanofi, upon aggregate annual sales of antibodies outside the United States (including Praluent) exceeding $2.0 billion and $2.5 billion, respectively, on a rolling twelve-month basis. In 2021, the Company earned a $50.0 million sales-based milestone from Sanofi, upon aggregate annual sales of antibodies outside the United States (including Praluent) exceeding $1.5 billion, on a rolling twelve-month basis. The Company's significant promised goods and services in connection with the Antibody Collaboration consist of providing research and development services, including the manufacturing of clinical supplies, and providing commercial-related services, including the manufacturing of commercial supplies. The Company recognizes amounts in connection with the Antibody Collaboration based on the amount it has the right to invoice and such amount corresponds directly with the Company's performance to date. The following table summarizes contract balances in connection with the Company's Antibody Collaboration with Sanofi: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ 1,029.1 $ 692.3 Deferred revenue $ 427.7 $ 415.8 Immuno-Oncology The Company was previously a party to a collaboration with Sanofi for antibody-based cancer treatments in the field of immuno-oncology (the "IO Collaboration"). The IO Collaboration was 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 was subsequently 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 identify and validate potential immuno-oncology targets and develop therapeutic antibodies against such targets through clinical proof-of-concept. 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 under the 2015 IO Discovery Agreement to developing therapeutic bispecific antibodies targeting (i) BCMA and CD3 and (ii) MUC16 and CD3 through clinical proof-of-concept. During 2021, Sanofi did not exercise its options to license rights to these product candidates; as a result, the Company retains the exclusive right to develop and commercialize such product candidates and Sanofi will receive a royalty on sales (if any). In addition, the Company has no further obligations to develop drug product candidates under the Amended IO Discovery Agreement. 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 were co-developing and co-commercializing Libtayo. The parties shared equally, on an ongoing basis, development and commercialization expenses for Libtayo. The Company had principal control over the development of Libtayo and led commercialization activities in the United States, while Sanofi led commercialization activities outside the United States. The parties shared equally in profits and losses in connection with the commercialization of Libtayo. Recognition of the up-front payments received from Sanofi had been deferred (recorded within Other liabilities), and such amounts were being recognized over the remaining period in which the Company was obligated to perform development activities. During 2021, the Company updated its estimate of the total research and development costs expected to be incurred (which resulted in a change to the estimate of the stage of completion) in connection with the IO Collaboration, and, as a result, recorded a cumulative catch-up adjustment of $66.9 million as a reduction to other operating income. In connection with the Amended and Restated Immuno-oncology License and Collaboration Agreement with Sanofi (the "A&R IO LCA") described below, the remaining IO Collaboration Other liabilities balance of $241.0 million as of July 1, 2022 was recognized as a reduction to the intangible asset recorded in connection with the transaction during 2022. Effective July 1, 2022, the Company obtained the exclusive right to develop, commercialize, and manufacture Libtayo worldwide under the A&R IO LCA. In connection with the A&R IO LCA, in 2022, the Company made a $900.0 million up-front payment to Sanofi, as well as a $100.0 million regulatory milestone payment. In addition, Sanofi was eligible to earn an aggregate of $100.0 million in Libtayo sales-based milestones under the terms of the A&R IO LCA, of which they earned $65.0 million in 2022 and $35.0 million in 2023. The Company also pays Sanofi an 11% royalty on net product sales of Libtayo through March 31, 2034. The transaction was accounted for as an asset acquisition and amounts paid to Sanofi in connection with obtaining the worldwide rights to Libtayo, including the up-front payment and any contingent consideration, are recorded as an intangible asset. See Note 8 for additional information related to the intangible asset. In accordance with the Amended IO Discovery Agreement, the Company was obligated to reimburse Sanofi for half of the development costs it funded that were attributable to clinical development of product candidates from the Company's share of profits from commercialized IO Collaboration products. Under the A&R IO LCA, the amount of development costs incurred under the IO Collaboration for which the Company was obligated to reimburse Sanofi was $35.0 million as of the effective date of the A&R IO LCA, and the Company pays Sanofi a 0.5% royalty on net product sales of Libtayo until all such development costs have been reimbursed by Regeneron. The Company's contingent reimbursement obligation to Sanofi under the A&R IO LCA was approximately $28 million as of December 31, 2023. b. Bayer The Company is party to a license and collaboration agreement with Bayer for the global development and commercialization of EYLEA 8 mg (aflibercept 8 mg) and EYLEA (aflibercept) outside the United States. Agreed-upon development expenses incurred by the Company and Bayer are generally shared equally. The Company is also obligated to use commercially reasonable efforts to supply clinical and commercial bulk product. Within the United States, the Company is responsible for commercialization and retains profits from such sales. Bayer is responsible for commercialization activities outside the United States, and the companies share equally in profits from such sales. In Japan, the Company was entitled to receive a tiered percentage of between 33.5% and 40.0% of EYLEA net product sales through 2021, and effective January 1, 2022, the companies share equally in profits from sales in Japan. The Company is obligated to reimburse Bayer out of its share of the collaboration profits 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 $293 million as of December 31, 2023. Amounts recognized in the Company's Statements of Operations in connection with its Bayer collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Regeneron's share of profits in connection with commercialization of EYLEA outside the United States Collaboration revenue $ 1,376.4 $ 1,317.4 $ 1,349.2 Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ 111.1 $ 91.4 $ 60.1 One-time payment in connection with change in Japan arrangement Collaboration revenue $ — $ 21.9 $ — Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (44.0) $ 16.7 $ 5.2 The following table summarizes contract balances in connection with the Company's Bayer collaboration: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ 381.7 $ 348.2 Deferred revenue $ 138.2 $ 131.9 c. Alnylam In 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. In connection with entering into the collaboration, the Company made an up-front payment of $400.0 million to Alnylam, and also purchased shares of Alnylam common stock for $400.0 million. For each program, the Company provides Alnylam with a specified amount of funding at program initiation and at lead candidate designation. Under the terms of the collaboration, the parties 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 co-development/co-commercialization collaboration agreement (under which the parties are advancing ALN-APP and ALN-PNP, which are currently in clinical development) or a license agreement. 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, the Company has the option to extend the Research Term for an additional five-year period for a research extension fee of $300.0 million. During 2023, the Company paid a $100.0 million development milestone to Alnylam, which was recorded to Acquired in-process research and development expense, upon the achievement of specified proof-of-principle criteria for the ALN-APP program. Alnylam is eligible to receive an additional $100.0 million clinical proof-of-principle milestone in connection with an eye program. Amounts recognized in the Company's Statements of Operations in connection with its Alnylam collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Regeneron's obligation for its share of Alnylam R&D expenses, net of reimbursement of R&D expenses (R&D expense) $ (74.1) $ (55.8) $ (60.5) Development milestone Acquired in-process research and development $ (100.0) $ — $ — The following table summarizes contract balances in connection with the Company's Alnylam collaboration: As of December 31, (In millions) 2023 2022 Accrued expenses and other current liabilities $ 22.6 $ 7.4 d. Roche The Company is a party to a collaboration agreement with Roche to develop, manufacture, and distribute the casirivimab and imdevimab antibody cocktail (known as REGEN-COV in the United States and Ronapreve ™ in other countries). Under the terms of the collaboration agreement, the parties jointly fund certain studies, and the Company has the right to distribute the product in the United States while Roche has the right to distribute the product outside the United States. The parties share gross profits from worldwide sales based on a pre-specified formula, depending on the amount of manufactured product supplied by each party to the market. Amounts recognized in the Company's Statements of Operations in connection with its Roche collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Global gross profit payment from Roche in connection with sales of REGEN-COV and Ronapreve Collaboration revenue $ 224.3 $ 627.3 $ 361.8 Other Collaboration revenue $ (13.3) $ — $ — Reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (1.5) $ 6.8 $ 128.1 Global gross profit payment to Roche in connection with sales of REGEN-COV and Ronapreve Cost of goods sold $ — $ — $ 259.6 The following table summarizes contract balances in connection with the Company's Roche collaboration: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ — $ 396.6 e. Intellia In 2016, the Company entered into a license and collaboration agreement with Intellia Therapeutics, Inc. to advance CRISPR/Cas9 gene-editing technology for in vivo therapeutic development. The parties collaborate to conduct research for the discovery, development, and commercialization of new therapies, in addition to the research and technology development of the CRISPR/Cas9 platform. Under the terms of the 2016 agreement, the parties agreed to a target selection process, whereby the Company may obtain exclusive rights in up to 10 targets to be chosen by the Company during the collaboration term, subject to various adjustments and limitations set forth in the agreement. Certain targets that either the Company or Intellia selects may be subject to a co-development and co-commercialization arrangement at the Company's option or Intellia’s option, as applicable. NTLA-2001, which is in clinical development, is subject to a co-development and co-commercialization arrangement pursuant to which Intellia will lead development and commercialization activities and the parties share an agreed-upon percentage of development expenses and profits (if commercialized). In 2020, the Company expanded its existing collaboration with Intellia to provide the Company with rights to develop products for additional in vivo CRISPR/Cas9-based therapeutic targets and for the parties to jointly develop potential products for the treatment of hemophilia A and B, with Regeneron leading development and commercialization activities. In addition, the Company also received non-exclusive rights to independently develop and commercialize ex vivo gene edited products. In connection with the agreement, in 2020, the Company made a $70.0 million up-front payment. In September 2023, the Company further expanded its existing collaboration to develop additional in vivo CRISPR-based gene editing therapies focused on neurological and muscular diseases. Intellia will lead the design of the editing methodology, the Company will lead the design of the targeted viral vector delivery approach, and the parties share costs equally. Each company will have the opportunity to lead potential development and commercialization of product candidates for one target, and the company that is not leading development and commercialization will have the option to enter into a co-development and co-commercialization agreement for the target. In October 2023, the Company elected to extend the period for selecting targets under the 2016 license and collaboration agreement for an additional two years until April 2026; as a result, the Company became obligated to make a $30.0 million extension payment to Intellia (which was recorded to Acquired in-process research and development expense in 2023). Amounts recognized in the Company's Statements of Operations in connection with research and development activities co-funded under the Intellia agreements were not material for the years ended December 31, 2023, 2022, and 2021. In addition, contract balances in the Company's Balance Sheets in connection with the Intellia agreements were not material as of December 31, 2023 and 2022. f. Sonoma In March 2023, the Company and Sonoma Biotherapeutics, Inc. entered into a license and collaboration agreement to bring together the Company's VelociSuite ® technologies with Sonoma's technology platform for the discovery, development, and commercialization of novel regulatory T cell ("Treg") therapies for autoimmune diseases. In connection with the agreement, the Company made a $45.0 million up-front payment (which was recorded to Acquired in-process research and development expense in 2023) and, in April 2023, the Company purchased an aggregate of $30.0 million of Sonoma preferred stock. Sonoma is also eligible to receive a $45.0 million development milestone payment. The Company and Sonoma will co-fund research and development activities and share equally any future commercial expenses and profits. The Company will have the option to lead late-stage development and commercialization on all products globally, with Sonoma retaining rights to co-promote all such products in the United States. Amounts recognized in the Company's Statements of Operations in connection with research and development activities co-funded under the Sonoma agreement were not material for the year ended December 31, 2023. In addition, contract balances in the Company's Balance Sheets in connection with the Sonoma agreement were not material as of December 31, 2023. g. U.S. Government In 2021, the Company entered into agreements with the U.S. Department of Defense and the U.S. Department of Health and Human Services ("HHS") to manufacture and deliver filled and finished drug product of REGEN-COV to the U.S. government. Roche supplied a portion of the doses to Regeneron to fulfill the Company's agreement with the U.S. government (see "Roche" above for further details regarding the Company's collaboration agreement with Roche). As of December 31, 2021, the Company had completed its final deliveries of drug product under these agreements. See Note 2 for REGEN-COV net product sales recognized during the year ended December 31, 2021 in connection with these agreements. In August 2023, the Company expanded its Other Transaction Agreement ("OTA") with the Biomedical Advanced Research and Development Authority ("BARDA"), pursuant to which the HHS is obligated to fund up to 70% of the Company's costs incurred for certain development activities related to a next-generation COVID-19 monoclonal antibody therapy for the prevention of SARS-CoV-2 infection. Pursuant to the terms of the expanded agreement, the Company could receive payments of up to approximately $326 million in the aggregate to support clinical development, clinical manufacturing, and the regulatory licensure process. Amounts recognized within Other revenue in the Company's Statements of Operations in connection with the expanded BARDA agreement were $50.4 million for the year ended December 31, 2023. The following table summarizes the Company's contract balances in connection with this BARDA agreement: As of December 31, (In millions) 2023 Accounts receivable, net $ 18.5 h. Decibel In 2017, the Company entered into an agreement with Decibel Therapeutics, Inc. to discover and develop new potential therapeutics to protect, repair and restore hearing (including DB-OTO, which is currently in clinical development, and preclinical programs for GJB2-related and stereocilin-related hearing loss). In connection with the agreement, the Company also purchased shares of Decibel stock. In August 2023, the Company entered into an Agreement and Plan of Merger to acquire Decibel, and in September 2023, the Company completed its acquisition of Decibel (which was accounted for as a business combination). The Company paid $101.3 million in cash (or $4.00 per share of Decibel common stock), of which $6.6 million was attributed to post-combination services to be rendered by Decibel equity award holders, and as a result, was excluded from the amount of consideration transferred for purchase accounting. In addition, Decibel shareholders received one non-tradeable contingent value right ("CVR") per share of Decibel common stock, which entitles the holder to receive up to $3.50 per share in cash upon achievement of certain clinical development and regulatory milestones for DB-OTO within specified time periods. At closing, the Company recorded a liability related to the fair value of the CVRs of $43.7 million (see Note 5). The maximum aggregate amount that holders of the CVRs may be entitled to receive if all the milestones contemplated by the CVRs are achieved is approximately $97 million. The fair value of the Company's investment in Decibel stock immediately before the acquisition date was $10.3 million. The following table summarizes the amounts recognized for assets acquired and liabilities assumed based on their estimated fair values as of the acquisition date: September 25, (In millions) 2023 Cash and cash equivalents $ 42.2 Marketable securities 12.1 Deferred tax assets, net 58.1 Indefinite-lived intangible asset related to in-process research and development 42.5 Goodwill 5.2 Other assets and liabilities, net (11.4) $ 148.7 The final determination of fair values of assets acquired, liabilities assumed, and tax-related items will be completed no later than one year from the acquisition date. i. Checkmate In 2022, the Company completed its acquisition of Checkmate Pharmaceuticals, Inc. for a total equity value of approximately $250 million. As a result of the transaction, which was accounted for as an asset acquisition, the Company recorded, during 2022, (i) a charge of $195.0 million to Acquired in-process research and development and (ii) net assets of $61.7 million, including $26.4 million of cash and cash equivalents acquired, related to the assets acquired (including deferred tax assets and investments) and liabilities assumed. j. Other In addition to the collaboration agreements discussed above, the Company has various other license and collaboration agreements that are not individually 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 contingent upon the occurrence of various future events (e.g., 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. The Company has also in-licensed patent and/or technology pursuant to agreements which contain provisions that require the Company to pay royalties, as defined, at rates that range from 0.5% to 12.0%, in the event the Company sells or licenses any proprietary products developed under the respective agreements. As described above, as a result of obtaining worldwide rights to Libtayo, the Company pays Sanofi a royalty on net product sales of Libtayo. In addition, in 2018, the Company 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, the Company paid royalties of 8.0% on worldwide sales of Libtayo through December 31, 2023, and is obligated to pay royalties of 2.5% from January 1, 2024 through December 31, 2026. Prior to July 1, 2022, royalties on such sales were shared equally by the Company and Sanofi. For the years ended December 31, 2023, 2022, and 2021, the Company recorded royalty expense (net of reimbursements from collaborators, as applicable) in its Statements of Operations of $117.6 million, $84.5 million, and $66.9 million, respectively, based on product sales under various licensing agreements.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Marketable securities as of December 31, 2023 and 2022 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: (In millions) Amortized Unrealized Fair As of December 31, 2023 Cost Basis Gains Losses Value Corporate bonds $ 6,492.5 $ 10.4 $ (104.9) $ 6,398.0 U.S. government and government agency obligations 4,839.6 2.4 (8.6) 4,833.4 Sovereign bonds 58.1 — (0.9) 57.2 Commercial paper 636.8 0.2 (0.2) 636.8 Certificates of deposit 520.8 0.6 — 521.4 Asset-backed securities 88.2 0.1 (1.2) 87.1 $ 12,636.0 $ 13.7 $ (115.8) $ 12,533.9 As of December 31, 2022 Corporate bonds $ 6,975.5 $ — $ (291.1) $ 6,684.4 U.S. government and government agency obligations 2,945.4 0.9 (6.9) 2,939.4 Sovereign bonds 67.1 — (3.0) 64.1 Commercial paper 121.1 — — 121.1 Certificates of deposit 182.1 — (0.1) 182.0 Asset-backed securities 28.9 — (1.7) 27.2 $ 10,320.1 $ 0.9 $ (302.8) $ 10,018.2 The Company classifies its investments in available-for-sale debt securities based on their contractual maturity dates. The available-for-sale debt securities as of December 31, 2023 mature at various dates through April 2029. The fair values of available-for-sale debt securities by contractual maturity consist of the following: As of December 31, (In millions) 2023 2022 Maturities within one year $ 8,114.8 $ 4,636.4 Maturities after one year through five years 4,414.5 5,381.4 Maturities after five years 4.6 0.4 $ 12,533.9 $ 10,018.2 The following table shows the fair value of the Company's available-for-sale debt securities that have unrealized losses, aggregated by investment category and length of time that the individual securities have been in a continuous loss position. Less than 12 Months 12 Months or Greater Total (In millions) As of December 31, 2023 Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 2,363.3 $ (2.4) $ 4,034.7 $ (102.5) $ 6,398.0 $ (104.9) U.S. government and government agency obligations 4,780.6 (6.0) 52.7 (2.6) 4,833.3 (8.6) Sovereign bonds 12.4 (0.1) 44.8 (0.8) 57.2 (0.9) Commercial paper 636.8 (0.2) — — 636.8 (0.2) Asset-backed securities 61.8 (0.3) 25.3 (0.9) 87.1 (1.2) $ 7,854.9 $ (9.0) $ 4,157.5 $ (106.8) $ 12,012.4 $ (115.8) As of December 31, 2022 Corporate bonds $ 2,445.4 $ (73.1) $ 4,200.4 $ (218.0) $ 6,645.8 $ (291.1) U.S. government and government agency obligations 785.2 (2.0) 71.0 (4.9) 856.2 (6.9) Sovereign bonds 18.6 (1.1) 45.6 (1.9) 64.2 (3.0) Certificates of deposit 40.2 (0.1) — — 40.2 (0.1) Asset-backed securities 11.5 (0.6) 15.2 (1.1) 26.7 (1.7) $ 3,300.9 $ (76.9) $ 4,332.2 $ (225.9) $ 7,633.1 $ (302.8) The unrealized losses on corporate bonds as of December 31, 2023 and 2022 were primarily driven by increased interest rates. The Company has reviewed its portfolio of available-for-sale debt securities and determined that the decline in fair value below cost did not result from credit-related factors. In addition, the Company does not intend to sell, and it is not more likely than not that the Company will be required to sell, such securities before recovery of their amortized cost bases. With respect to marketable securities, for the years ended December 31, 2023, 2022, and 2021, amounts reclassified from Accumulated other comprehensive loss into Other income (expense), net were related to realized gains/losses on sales of available-for-sale debt securities. Realized gains and losses on sales of marketable securities were not material for the years ended December 31, 2023, 2022, and 2021. The Company recognized interest income of $495.9 million, $160.1 million, and $45.8 million for the years ended December 31, 2023, 2022, and 2021, respectively, in Other income (expense), net.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The table below summarizes the Company's assets and liabilities which are measured at fair value on a recurring basis. The following fair value hierarchy is used to classify assets and liabilities, based on inputs to valuation techniques utilized to measure fair value: • Level 1 - Quoted prices in active markets for identical assets or liabilities • 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 (In millions) Fair Value Measurements at Reporting Date As of December 31, 2023 Fair Value Level 1 Level 2 Level 3 Assets: Cash equivalents $ 928.1 $ 6.4 $ 921.7 $ — Available-for-sale debt securities: Corporate bonds 6,398.0 — 6,398.0 — U.S. government and government agency obligations 4,833.4 — 4,833.4 — Sovereign bonds 57.2 — 57.2 — Commercial paper 636.8 — 636.8 — Certificates of deposit 521.4 — 521.4 — Asset-backed securities 87.1 — 87.1 — Equity securities (unrestricted) 864.5 864.5 — — Equity securities (restricted) 112.9 112.9 — — Total assets $ 14,439.4 $ 983.8 $ 13,455.6 $ — Liabilities: Contingent consideration - CVRs $ 43.7 $ — $ — $ 43.7 As of December 31, 2022 Assets: Cash equivalents $ 1,662.8 $ 88.3 $ 1,574.5 $ — Available-for-sale debt securities: Corporate bonds 6,684.4 — 6,684.4 — U.S. government and government agency obligations 2,939.4 — 2,939.4 — Sovereign bonds 64.1 — 64.1 — Commercial paper 121.1 — 121.1 — Certificates of deposit 182.0 — 182.0 — Asset-backed securities 27.2 — 27.2 — Equity securities (unrestricted) 24.6 24.6 — — Equity securities (restricted) 1,185.4 1,185.4 — — Total assets $ 12,891.0 $ 1,298.3 $ 11,592.7 $ — The Company held certain restricted equity securities as of December 31, 2023 which are subject to transfer restrictions that expire at various dates throug h 2024 . During the years ended December 31, 2023 and 2022, the Company recorded $237.8 million and $39.8 million, respectively, of net unrealized losses on equity securities in Other income (expense), net. During the year ended December 31, 2021, the Company recorded $386.1 million of net unrealized gains on equity securities in Other income (expense), net. In addition, during the year ended December 31, 2023, the Company recorded a write-down of $29.0 million in Other income (expense), net related to the Company's investments in private companies. In addition to the investments summarized in the table above, as of December 31, 2023 and 2022, the Company had $74.3 million and $48.3 million, respectively, in equity investments that do not have a readily determinable fair value. These investments are recorded within Other noncurrent assets. As described in Note 3, in September 2023, the Company acquired Decibel and recorded a liability for the CVRs within other liabilities. The fair value of the CVR liability is determined based on the probability of achieving certain clinical development and regulatory milestones and estimated discount rates. Through December 31, 2023, there were no changes in the fair value of the CVRs subsequent to the date of acquisition. The fair value of the Company's long-term debt (see Note 10), which was determined based on Level 2 inputs, was estimated to be $1.528 billion and $1.443 billion as of December 31, 2023 and 2022, respectively.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: As of December 31, (In millions) 2023 2022 Raw materials $ 789.3 $ 818.4 Work-in-process 1,121.8 963.1 Finished goods 147.3 98.6 Deferred costs 522.1 521.8 $ 2,580.5 $ 2,401.9 Deferred costs represent the costs of product manufactured and shipped to the Company's collaborators for which recognition of revenue has been deferred. Inventory balances in the table above are net of reserves of $705.9 million and $720.7 million as of December 31, 2023 and 2022, respectively. For the years ended December 31, 2023, 2022, and 2021, Cost of goods sold included inventory write-offs and reserves of $102.3 million, $258.7 million, and $457.1 million, respectively. Inventory write-offs and reserves for the years ended 2022 and 2021 primarily related to REGEN-COV.

Property, Plant, and Equipment

Property, Plant, and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment	Property, Plant, and Equipment Property, plant, and equipment, net consists of the following: As of December 31, (In millions) 2023 2022 Building and improvements $ 2,423.1 $ 2,270.0 Leasehold improvements 133.9 114.3 Laboratory equipment 1,384.5 1,315.3 Computer equipment and software 389.7 337.4 Furniture, office equipment, and other 165.9 150.2 Land 283.1 264.5 Construction in progress 1,345.0 980.5 6,125.2 5,432.2 Accumulated depreciation and amortization (1,978.8) (1,669.2) $ 4,146.4 $ 3,763.0 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 on property, plant, and equipment was $328.8 million, $303.9 million, and $281.1 million for the years ended December 31, 2023, 2022, and 2021, respectively. As of December 31, 2023 and 2022, $3.375 billion and $2.960 billion, respectively, of the Company's net property, plant, and equipment was located in the United States and $771.4 million and $803.0 million, respectively, was located outside the United States (primarily in Ireland).

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Intangible Assets Intangible assets. net consist of the following: As of December 31, 2023 2022 (In millions) Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross carrying Amount Accumulated Amortization Net Carrying Amount Acquired product rights - Libtayo 13 years $ 1,119.1 $ (126.7) $ 992.4 $ 946.3 $ (35.7) $ 910.6 Other intangibles 8 years 10.0 (6.3) 3.7 10.0 (5.1) 4.9 Acquired in-process research and development Indefinite 42.5 — 42.5 — — — $ 1,171.6 $ (133.0) $ 1,038.6 $ 956.3 $ (40.8) $ 915.5 As described in Note 3, during the year ended December 31, 2023, the Company recorded an indefinite-lived intangible asset of $42.5 million in connection with its acquisition of Decibel. During the year ended December 31, 2022, the Company recorded an intangible asset in connection with obtaining the exclusive right to develop, commercialize, and manufacture Libtayo worldwide. The intangible asset recognized upon the effective date of the A&R IO LCA primarily consisted of the $900.0 million up-front payment, offset by the remaining IO Collaboration other liabilities balance of $241.0 million. Additionally, during the years ended December 31, 2023 and 2022, the Company recorded additions to the Libtayo intangible asset related to contingent consideration (including regulatory and sales-based milestones) due to Sanofi. See Note 3. Amortization expense on intangible assets was $92.2 million and $37.6 million for the years ended December 31, 2023 and 2022, respectively. Amortization expense for the year ended December 31, 2021 was not material. As of December 31, 2023, assuming no changes in the gross carrying amount of intangible assets, amortization expense is estimated to be approximately $85 million for each of the years ending December 31, 2024 through December 31, 2028.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following: As of December 31, (In millions) 2023 2022 Accrued payroll and related costs $ 618.2 $ 497.3 Accrued clinical expenses 292.2 295.0 Accrued sales-related costs 780.8 633.6 Other accrued expenses and liabilities 666.7 648.3 $ 2,357.9 $ 2,074.2

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt	Debt Credit Facility In December 2022, the Company entered into an agreement with a syndicate of lenders (the "2022 Credit Agreement") which provides for a $750.0 million senior unsecured five-year revolving credit facility (the "2022 Credit Facility") and replaced the Company's then-existing credit agreement, which was contemporaneously terminated. The 2022 Credit Agreement includes an option for the Company to elect to increase the commitments under the 2022 Credit Facility and/or to enter into one or more tranches of term loans in the aggregate principal amount of up to $500.0 million, subject to the consent of the lenders providing the additional commitments or term loans, as applicable, and certain other conditions. The 2022 Credit Agreement also provides a $50.0 million sublimit for letters of credit. Proceeds of the loans under the 2022 Credit Facility may be used to finance working capital needs, and for general corporate or other lawful purposes, of Regeneron and its subsidiaries. Regeneron Pharmaceuticals, Inc. has guaranteed all obligations under the 2022 Credit Facility. The 2022 Credit Agreement includes an option for the Company to elect to extend the maturity date of the 2022 Credit Facility beyond December 2027, subject to the consent of the extending lenders and certain other conditions. The Company had no borrowings outstanding under the 2022 Credit Facility as of December 31, 2023. The 2022 Credit Agreement contains operating covenants and a maximum total leverage ratio financial covenant. The Company was in compliance with all covenants of the 2022 Credit Agreement as of December 31, 2023. Senior Notes In 2020, the Company issued and sold $1.250 billion aggregate principal amount of senior unsecured notes due 2030 and $750 million aggregate principal amount of senior unsecured notes due 2050 (collectively, the "Notes"). The underwriting discounts and offering expenses are being amortized as additional interest expense over the period from issuance through maturity. Long-term debt in connection with the Notes, net of underwriting discounts and offering expenses, consists of the following: As of December 31, (In millions) 2023 2022 1.750% Senior Notes due September 2030 $ 1,242.2 $ 1,241.0 2.800% Senior Notes due September 2050 740.7 740.4 $ 1,982.9 $ 1,981.4 Interest on each series of Notes is payable semi-annually in arrears on March 15 and September 15 of each year until their respective maturity dates. Interest expense related to the Notes was $44.4 million in each of the years ended December 31, 2023, 2022, and 2021. The Notes may be redeemed at the Company’s option at any time at 100% of the principal amount plus accrued and unpaid interest, and, until a specified period before maturity, a specified make-whole amount. The Notes contain a change-of-control provision that, under certain circumstances, may require the Company to offer to repurchase the Notes at a price equal to 101% of the principal amount plus accrued and unpaid interest. The Notes also contain certain limitations on the Company's ability to incur liens and enter into sale and leaseback transactions, as well as customary events of default.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Leases The Company conducts certain of its research, development, and administrative activities at leased facilities. The Company also leases vehicles and other assets. Tarrytown, New York Lease The Company is party to a Third Amended and Restated Lease and Remedies Agreement (the "Third Amended and Restated Lease") with BA Leasing BSC, LLC, an affiliate of Banc of America Leasing & Capital, LLC ("BAL"), as lessor, which relates to the Company’s lease of laboratory and office facilities in Tarrytown, New York (the “Facility”); and a Third Amended and Restated Participation Agreement (the "Third Amended and Restated Participation Agreement") with Bank of America, N.A., as administrative agent (the "Administrative Agent"), and a syndicate of lenders (collectively with BAL, the "Participants"), as rent assignees. The Third Amended and Restated Lease and Third Amended and Restated Participation Agreement provide for a March 2027 maturity date of the $720.0 million lease financing (previously advanced by the Participants in March 2017 in connection with the acquisition by BAL of the Facility and the Company's lease of the Facility from BAL) and the end of the term of the Company's lease of the Facility from BAL, at which time all amounts outstanding thereunder will become due and payable in full. In accordance with the terms of the Third Amended and Restated Lease, the Company pays all maintenance, insurance, taxes, and other costs arising out of the use of the Facility. The Company is also required to make monthly payments of basic rent during the remaining term of the Third Amended and Restated Lease to satisfy the yield payable to the Participants on their outstanding advances under the Third Amended and Restated Participation Agreement. Such advances accrue yield at a variable rate per annum based on the one-month forward-looking Secured Overnight Financing Rate ("SOFR") term rate, plus a spread adjustment, plus an applicable margin that varies with the Company's debt rating and total leverage ratio. The Third Amended and Restated Participation Agreement and Third Amended and Restated Lease include an option for the Company to elect to further extend the maturity date of the Third Amended and Restated Participation Agreement and the term of the Third Amended and Restated Lease for an additional five-year period, subject to the consent of all the Participants and certain other conditions. The Company also has the option prior to the end of the term of the Third Amended and Restated Lease to (a) purchase the Facility by paying an amount equal to the outstanding principal amount of the Participants' advances under the Third Amended and Restated Participation Agreement, all accrued and unpaid yield thereon, and all other outstanding amounts under the Third Amended and Restated Participation Agreement, Third Amended and Restated Lease, and certain related documents or (b) sell the Facility to a third party on behalf of BAL. The Third Amended and Restated Lease is classified as a finance lease as the Company has the option to purchase the Facility under terms that make it reasonably certain to be exercised. The agreements governing the Third Amended and Restated Lease financing contain financial and operating covenants. Such financial covenants and certain of the operating covenants are substantially similar to the covenants set forth in the 2022 Credit Agreement. The Company was in compliance with all such covenants as of December 31, 2023. Aggregate Lease Information Amounts recognized in the Consolidated Balance Sheet related to the Company's leases are included in the table below. As of December 31, (In millions) Classification 2023 2022 Assets: Finance lease right-of-use assets Property, plant, and equipment, net (a) $ 605.7 $ 620.3 Operating lease right-of-use assets Other noncurrent assets (b) 78.0 71.2 $ 683.7 $ 691.5 Liabilities: Finance lease liabilities - noncurrent Finance lease liabilities $ 720.0 $ 720.0 Operating lease liabilities - current Accrued expenses and other current liabilities 19.0 12.4 Operating lease liabilities - noncurrent Other noncurrent liabilities 68.7 55.8 $ 807.7 $ 788.2 (a) Finance lease right-of-use assets were recorded net of accumulated amortization of $133.9 million and $119.4 million as of December 31, 2023 and 2022, respectively. (b) Operating lease right-of-use assets were recorded net of accumulated amortization of $44.6 million and $31.0 million as of December 31, 2023 and 2022, respectively. Lease costs consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 Operating lease costs $ 19.2 $ 12.4 $ 10.3 Finance lease costs: Amortization of finance lease right-of-use assets 14.5 14.5 14.4 Interest on finance lease liabilities 45.0 21.6 11.9 Total finance lease costs 59.5 36.1 26.3 Total lease costs $ 78.7 $ 48.5 $ 36.6 Other information related to the Company's leases includes the following: As of December 31, 2023 2022 Weighted-average remaining lease term (in years): Finance leases 3.2 4.2 Operating leases 7.4 7.2 Weighted-average discount rate: Finance leases 5.08% 4.84% Operating leases 5.38% 5.20% Supplemental cash flow information related to the Company's leases includes the following: Year Ended December 31, (In millions) 2023 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities (included within cash flows from operating activities) $ 22.5 $ 7.7 $ 10.2 Right-of-use assets obtained in exchange for operating lease liabilities $ 31.9 $ 35.1 $ 0.2 The following is a maturity analysis of the Company's lease liabilities as of December 31, 2023: (In millions) Finance Leases Operating Leases Total 2024 $ 44.8 $ 24.1 $ 68.9 2025 39.5 20.1 59.6 2026 30.9 15.6 46.5 2027 728.4 12.4 740.8 2028 — 11.0 11.0 Thereafter — 20.1 20.1 Total undiscounted lease payments 843.6 103.3 946.9 Imputed interest (123.6) (15.6) (139.2) Total lease liabilities $ 720.0 $ 87.7 $ 807.7
Leases	Leases The Company conducts certain of its research, development, and administrative activities at leased facilities. The Company also leases vehicles and other assets. Tarrytown, New York Lease The Company is party to a Third Amended and Restated Lease and Remedies Agreement (the "Third Amended and Restated Lease") with BA Leasing BSC, LLC, an affiliate of Banc of America Leasing & Capital, LLC ("BAL"), as lessor, which relates to the Company’s lease of laboratory and office facilities in Tarrytown, New York (the “Facility”); and a Third Amended and Restated Participation Agreement (the "Third Amended and Restated Participation Agreement") with Bank of America, N.A., as administrative agent (the "Administrative Agent"), and a syndicate of lenders (collectively with BAL, the "Participants"), as rent assignees. The Third Amended and Restated Lease and Third Amended and Restated Participation Agreement provide for a March 2027 maturity date of the $720.0 million lease financing (previously advanced by the Participants in March 2017 in connection with the acquisition by BAL of the Facility and the Company's lease of the Facility from BAL) and the end of the term of the Company's lease of the Facility from BAL, at which time all amounts outstanding thereunder will become due and payable in full. In accordance with the terms of the Third Amended and Restated Lease, the Company pays all maintenance, insurance, taxes, and other costs arising out of the use of the Facility. The Company is also required to make monthly payments of basic rent during the remaining term of the Third Amended and Restated Lease to satisfy the yield payable to the Participants on their outstanding advances under the Third Amended and Restated Participation Agreement. Such advances accrue yield at a variable rate per annum based on the one-month forward-looking Secured Overnight Financing Rate ("SOFR") term rate, plus a spread adjustment, plus an applicable margin that varies with the Company's debt rating and total leverage ratio. The Third Amended and Restated Participation Agreement and Third Amended and Restated Lease include an option for the Company to elect to further extend the maturity date of the Third Amended and Restated Participation Agreement and the term of the Third Amended and Restated Lease for an additional five-year period, subject to the consent of all the Participants and certain other conditions. The Company also has the option prior to the end of the term of the Third Amended and Restated Lease to (a) purchase the Facility by paying an amount equal to the outstanding principal amount of the Participants' advances under the Third Amended and Restated Participation Agreement, all accrued and unpaid yield thereon, and all other outstanding amounts under the Third Amended and Restated Participation Agreement, Third Amended and Restated Lease, and certain related documents or (b) sell the Facility to a third party on behalf of BAL. The Third Amended and Restated Lease is classified as a finance lease as the Company has the option to purchase the Facility under terms that make it reasonably certain to be exercised. The agreements governing the Third Amended and Restated Lease financing contain financial and operating covenants. Such financial covenants and certain of the operating covenants are substantially similar to the covenants set forth in the 2022 Credit Agreement. The Company was in compliance with all such covenants as of December 31, 2023. Aggregate Lease Information Amounts recognized in the Consolidated Balance Sheet related to the Company's leases are included in the table below. As of December 31, (In millions) Classification 2023 2022 Assets: Finance lease right-of-use assets Property, plant, and equipment, net (a) $ 605.7 $ 620.3 Operating lease right-of-use assets Other noncurrent assets (b) 78.0 71.2 $ 683.7 $ 691.5 Liabilities: Finance lease liabilities - noncurrent Finance lease liabilities $ 720.0 $ 720.0 Operating lease liabilities - current Accrued expenses and other current liabilities 19.0 12.4 Operating lease liabilities - noncurrent Other noncurrent liabilities 68.7 55.8 $ 807.7 $ 788.2 (a) Finance lease right-of-use assets were recorded net of accumulated amortization of $133.9 million and $119.4 million as of December 31, 2023 and 2022, respectively. (b) Operating lease right-of-use assets were recorded net of accumulated amortization of $44.6 million and $31.0 million as of December 31, 2023 and 2022, respectively. Lease costs consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 Operating lease costs $ 19.2 $ 12.4 $ 10.3 Finance lease costs: Amortization of finance lease right-of-use assets 14.5 14.5 14.4 Interest on finance lease liabilities 45.0 21.6 11.9 Total finance lease costs 59.5 36.1 26.3 Total lease costs $ 78.7 $ 48.5 $ 36.6 Other information related to the Company's leases includes the following: As of December 31, 2023 2022 Weighted-average remaining lease term (in years): Finance leases 3.2 4.2 Operating leases 7.4 7.2 Weighted-average discount rate: Finance leases 5.08% 4.84% Operating leases 5.38% 5.20% Supplemental cash flow information related to the Company's leases includes the following: Year Ended December 31, (In millions) 2023 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities (included within cash flows from operating activities) $ 22.5 $ 7.7 $ 10.2 Right-of-use assets obtained in exchange for operating lease liabilities $ 31.9 $ 35.1 $ 0.2 The following is a maturity analysis of the Company's lease liabilities as of December 31, 2023: (In millions) Finance Leases Operating Leases Total 2024 $ 44.8 $ 24.1 $ 68.9 2025 39.5 20.1 59.6 2026 30.9 15.6 46.5 2027 728.4 12.4 740.8 2028 — 11.0 11.0 Thereafter — 20.1 20.1 Total undiscounted lease payments 843.6 103.3 946.9 Imputed interest (123.6) (15.6) (139.2) Total lease liabilities $ 720.0 $ 87.7 $ 807.7

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
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 Programs In January 2021, the Company's board of directors authorized a share repurchase program to repurchase up to $1.5 billion of the Company's Common Stock. As of December 31, 2021, the Company had repurchased the entire $1.5 billion of its Common Stock that it was authorized to repurchase under the program. In November 2021, the Company's board of directors authorized a share repurchase program to repurchase up to $3.0 billion of the Company's Common Stock. As of June 30, 2023, the Company had repurchased the entire $3.0 billion of its Common Stock that it was authorized to repurchase under the program. In January 2023, the Company's board of directors authorized an additional share repurchase program to repurchase up to $3.0 billion of the Company's Common Stock. The share repurchase program permits the Company to make 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. There can be no assurance as to the timing or number of shares of any repurchases in the future. As of December 31, 2023, $1.531 billion remained available for share repurchases under the program. The table below summarizes the shares of the Company's Common Stock repurchased and the cost of the shares, which were recorded as Treasury Stock. Year Ended December 31, (In millions) 2023 2022 2021 Number of shares 2.9 3.3 3.0 Total cost of shares $ 2,214.6 $ 2,099.8 $ 1,655.0

Long-Term Incentive Plans

Long-Term Incentive Plans	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Long-Term Incentive Plans	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 non-employee 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 Second Amended and Restated Regeneron Pharmaceuticals, Inc. 2014 Long-Term Incentive Plan (the "Second Amended and Restated 2014 Incentive Plan"). It was most recently adopted and approved by the Company's shareholders in 2020. As of the most recent shareholder approval date, the Second Amended and Restated 2014 Incentive Plan provided for the issuance of up to 22.3 million 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 Regeneron Pharmaceuticals, Inc. 2014 Long-Term Incentive Plan (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 "2000 Incentive Plan"), any shares subject to such award are added to the pool of shares available for grant under the Second Amended and Restated 2014 Incentive Plan. The awards that may be made under the Second Amended and Restated 2014 Incentive Plan include: (a) non-qualified stock options and incentive stock options, (b) restricted stock awards, (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 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, the Amended and Restated 2014 Incentive Plan, and the Second 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 awards will be transferred to the Company. Phantom stock awards provide the Participant the right to receive Common Stock or an amount of cash based on the value of the Common Stock at a future date. The award is subject to such restrictions, if any, as the Committee may impose at the date of grant or thereafter, including a specified period of employment or the achievement of performance goals. Time-based restricted stock units and performance-based restricted stock units are each a type of phantom stock award permitted under the Second Amended and Restated 2014 Incentive Plan. 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, 2023, there were 14.6 million shares available for future grants under the Second Amended and Restated 2014 Incentive Plan. a. Stock Options The table below summarizes the activity related to stock option awards under the Company's Incentive Plans during 2023. Number of Shares (In millions) Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term Intrinsic Value (In millions) Outstanding as of December 31, 2022 15.6 $ 481.62 2023: Granted 1.6 $ 835.91 Forfeited (0.2) $ 580.17 Exercised (2.8) $ 412.05 Outstanding as of December 31, 2023 14.2 $ 534.13 6.0 years $ 4,918.6 Vested and expected to vest as of December 31, 2023 13.8 $ 526.95 5.9 years $ 4,852.2 Exercisable as of December 31, 2023 9.6 $ 450.01 4.7 years $ 4,118.0 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 2023, 2022, and 2021 was $1.096 billion, $1.214 billion, and $1.707 billion, 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, 2023, 2022, and 2021. Number of Options Granted (In millions) Weighted-Average Exercise Price Weighted-Average Fair Value 2023: Exercise price equal to Market Price 1.6 $ 835.91 $ 264.37 2022: Exercise price equal to Market Price 2.0 $ 705.02 $ 220.88 2021: Exercise price equal to Market Price 2.3 $ 628.43 $ 174.20 For the years ended December 31, 2023, 2022, and 2021, the Company recognized $357.1 million, $341.9 million, and $328.7 million, respectively, of stock-based compensation expense related to stock option awards (net of amounts capitalized as inventory, which were not material for each of the three years). As of December 31, 2023, there was $589.6 million of stock-based compensation cost related to unvested 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 1.8 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 2023, 2022, and 2021. 2023 2022 2021 Expected volatility 26 % 28 % 27 % Expected lives from grant date 5.1 years 5.2 years 5.5 years Expected dividend yield 0 % 0 % 0 % Risk-free interest rate 4.29 % 3.50 % 1.22 % 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 have plans to do so. 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 Time-Based Restricted Stock Units A summary of the Company's activity related to restricted stock awards and time-based restricted stock units (excluding performance-based restricted stock units, which are detailed further below) (collectively, "restricted stock") during 2023 is summarized below. Number of Shares/Units (In millions) Weighted-Average Grant Unvested as of December 31, 2022 2.6 $ 571.19 2023: Granted 0.8 $ 838.11 Vested (1.0) $ 458.49 Forfeited (0.1) $ 585.23 Unvested as of December 31, 2023 2.3 $ 705.37 For the years ended December 31, 2023, 2022, and 2021, the Company recognized $475.9 million, $331.1 million, and $221.0 million, respectively, of stock-based compensation expense related to restricted stock (net of amounts capitalized as inventory, which were not material for each of the three years). As of December 31, 2023, there was $1.023 billion 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 2.2 years. c. Performance-based Restricted Stock Units Performance-based restricted stock units ("PSUs") have been granted to certain members of senior management of the Company. PSUs may be earned based upon the attainment of pre-established performance criteria, which may include a market and/or performance condition. Depending on the terms of the PSUs and the outcome of the pre-established performance criteria, a recipient may ultimately earn the target number of PSUs granted or a specified multiple thereof at the end of a 4–6 year vesting period, as applicable. The table below summarizes activity related to PSUs during 2023. The number of unvested PSUs represents the maximum number of units that are eligible to be earned. Number of Shares/Units (In millions) Weighted-Average Grant Unvested as of December 31, 2022 1.5 $ 245.94 2023: Vested (0.1) $ 198.10 Unvested as of December 31, 2023 1.4 $ 247.91 For each of the years ended December 31, 2023, 2022, and 2021 the Company recognized $52.0 million of stock-based compensation expense related to PSUs. As of December 31, 2023, there was $104.1 million of stock-based compensation cost related to unvested PSUs which had not yet been recognized. The Company expects to recognize this compensation cost on a straight-line basis over a weighted average period of 2.3 years. Fair Value Assumptions: The following table summarizes the weighted average values of the assumptions used in computing the fair value of PSUs that were granted during 2022. The Company did not grant PSUs during 2023 and 2021. 2022 Expected volatility 32% Expected dividend yield 0% Risk-free interest rate 3.3%

Employee Savings Plans

Employee Savings Plans	12 Months Ended
	Dec. 31, 2023
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, as defined, to the accounts of participants under the Savings Plan. The Company also maintains additional employee savings plans outside the United States, which cover eligible employees. Expenses recognized by the Company related to contributions to such plans were $84.7 million, $67.6 million, and $55.5 million for the years ended December 31, 2023, 2022, and 2021, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state, and foreign income taxes. Components of income before income taxes consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 United States $ (362.3) $ 839.9 $ 5,944.7 Foreign 4,561.6 4,018.9 3,381.1 $ 4,199.3 $ 4,858.8 $ 9,325.8 Components of income tax expense consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 Current: Federal $ 667.9 $ 968.5 $ 1,429.8 State 7.7 7.4 6.2 Foreign 407.9 290.9 (38.4) Total current tax expense 1,083.5 1,266.8 1,397.6 Deferred: Federal (834.5) (797.7) (423.2) State (6.5) (2.7) (0.6) Foreign 3.2 54.0 276.7 Total deferred tax benefit (837.8) (746.4) (147.1) $ 245.7 $ 520.4 $ 1,250.5 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, 2023 2022 2021 U.S. federal statutory tax rate 21.0 % 21.0 % 21.0 % Taxation of non-U.S. operations (6.6) (5.5) (2.8) Stock-based compensation (4.6) (2.9) (2.4) Income tax credits (3.2) (2.0) (1.0) Foreign-derived intangible income deduction (0.3) (1.0) (1.4) Other permanent differences (0.4) 1.1 — Effective income tax rate 5.9 % 10.7 % 13.4 % 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, (In millions) 2023 2022 Deferred tax assets: Capitalized research and development expenses $ 1,728.2 $ 845.3 Deferred compensation 413.6 416.2 Accrued expenses 214.1 235.6 Fixed assets and intangible assets 154.8 227.6 Tax attribute carryforwards 88.7 41.3 Other 26.4 15.9 Total deferred tax assets 2,625.8 1,781.9 Deferred tax liabilities: Unrealized gains on investments (50.4) (58.2) Net deferred tax assets $ 2,575.4 $ 1,723.7 The Company's federal income tax returns for 2017 through 2022 remain open to examination by the IRS. The Company's 2017 and 2018 federal income tax returns are currently under audit by the IRS. In general, the Company's state income tax returns from 2018 to 2022 remain open to examination. The Company's income tax returns outside the United States remain open to examination from 2018 to 2022. 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: (In millions) 2023 2022 2021 Balance as of January 1 $ 542.8 $ 410.9 $ 267.0 Gross increases related to current year tax positions 153.4 136.9 182.3 Gross increases (decreases) related to prior year tax positions 3.2 (5.0) 2.9 Gross decreases due to settlements and lapse of statutes of limitations (3.0) — (41.3) Balance as of December 31 $ 696.4 $ 542.8 $ 410.9 In 2023, 2022, and 2021, 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. In 2021, the decrease in unrecognized tax benefits due to settlements and lapse of statutes of limitations was related to the closing of audits for the Company's federal income tax returns for 2015 and 2016. Interest expense related to unrecognized tax benefits was not material in 2023, 2022, and 2021. 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 the consolidated financial statements as of December 31, 2023. The amount of net unrecognized tax benefits that, if settled, would impact the effective tax rate is $442.5 million, $373.7 million, and $321.1 million as of December 31, 2023, 2022, and 2021, respectively.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2023
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. The outcome of any such proceedings, regardless of the merits, is inherently uncertain. If the Company were unable to prevail in any such proceedings, its consolidated financial position, results of operations, and future cash flows may be materially impacted. Costs associated with the Company's involvement in legal proceedings are expensed as incurred. 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, 2023 and 2022, the Company's accruals for loss contingencies were not material. There are certain loss contingencies that the Company deems reasonably possible for which the possible loss or range of possible loss is not estimable at this time. Proceedings Relating to Praluent (alirocumab) Injection As described 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. In addition, as described below, the Company filed a lawsuit against Amgen alleging that Amgen engaged in an anticompetitive bundling scheme which was designed to exclude Praluent from the market in violation of U.S. federal and state laws. United States In the United States, Amgen asserted claims of U.S. Patent Nos. 8,829,165 (the "'165 Patent") and 8,859,741 (the "'741 Patent"), and sought 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) Praluent. Amgen also sought a judgment of patent infringement of the asserted patents, monetary damages (together with interest), costs and expenses of the lawsuits, and attorneys' fees. As previously reported, on February 11, 2021, the United States Court of Appeals for the Federal Circuit (the "Federal Circuit") affirmed the lower court's decision that certain of Amgen's asserted patent claims are invalid based on lack of enablement. On April 14, 2021, Amgen filed a petition for a rehearing en banc with the Federal Circuit, which was denied on June 21, 2021. On November 4, 2022, the United States Supreme Court granted Amgen's petition for writ of certiorari. An oral hearing was held on March 27, 2023. On May 28, 2023, the United States Supreme Court affirmed the Federal Circuit's decision that certain of Amgen's asserted patent claims are invalid based on lack of enablement. On May 27, 2022, the Company filed a lawsuit against Amgen in the United States District Court for the District of Delaware, alleging that, beginning in 2020, Amgen engaged in an anticompetitive bundling scheme which was designed to exclude Praluent from the market in violation of federal and state laws. The lawsuit seeks damages for harm caused by the alleged scheme, as well as injunctive relief restraining Amgen from continuing its alleged anticompetitive conduct. On August 1, 2022, Amgen filed a motion to dismiss the complaint. On August 11, 2022, Amgen filed a motion to stay these proceedings pending resolution of the patent litigation described in the preceding paragraph. An oral hearing on Amgen's motion to dismiss and motion to stay was held on January 6, 2023. On February 10, 2023, the court denied Amgen's motion to stay; and on March 21, 2023, the court denied Amgen's motion to dismiss. On August 28, 2023, the Company filed an amended complaint in this matter; and, as part of its response, on September 20, 2023, Amgen filed a counterclaim alleging that the Company engaged in unfair business practices in violation of state law. A trial has been scheduled to begin in November 2024. Europe Amgen has asserted European Patent No. 2,215,124 (the "'124 Patent"), which pertains to PCSK9 monoclonal antibodies, in certain countries in Europe. In October 2020, the '124 Patent claims directed to compositions of matter and medical use relevant to Praluent were ruled invalid based on a lack of inventive step by the Technical Board of Appeal (the "TBA") of the European Patent Office (the "EPO"). Following the EPO's decision, each of the '124 Patent infringement proceedings initiated by Amgen against the Company and certain of Sanofi's affiliated entities in these countries was dismissed, including in Germany. The dismissal in Germany followed an earlier finding of infringement and granting of an injunction, both of which were subsequently overturned. As a result of the overturned injunction in Germany, the Company and/or certain of Sanofi's affiliated entities are seeking damages caused by Amgen's enforcement of the injunction. An oral hearing has been scheduled for February 28, 2024. As part of its opposition to these damages claims, on March 23, 2022, Amgen filed a counterclaim that asserted the German designation of European Patent No. 2,641,917 (the "'917 Patent") and seeks, among other things, a judgment of patent infringement, injunctive relief, and monetary damages. The '917 Patent is a divisional patent of the '124 Patent discussed above (i.e., a patent that shares the same priority date, disclosure, and patent term of the parent '124 Patent but contains claims to a different invention). An oral hearing before the Munich Regional Court was held on November 29, 2023, at which Amgen's counterclaim was dismissed. The '917 Patent is also subject to opposition proceedings in the EPO, which were initiated by Sanofi on May 5, 2021. An oral hearing before the EPO was held on February 21, 2023, at which the '917 Patent was revoked. Amgen filed a notice to appeal to the TBA of the EPO on February 27, 2023. On June 1, 2023, Amgen filed a lawsuit against the Company and certain of Sanofi's affiliated entities in the Munich Local Division of the Unified Patent Court (the "UPC") alleging infringement of Amgen's European Patent No. 3,666,797 (the "'797 Patent"). The lawsuit seeks, among other things, a permanent injunction in several countries in Europe and monetary damages. The '797 Patent is a divisional patent of the '124 Patent discussed above. A trial has been scheduled for October 16–17, 2024. Also on June 1, 2023, Sanofi filed an action in the Munich Central Division of the UPC seeking revocation of the '797 Patent. A trial has been scheduled for June 4–5, 2024. Proceedings Relating to EYLEA (aflibercept) Injection Certain of the Company's patents pertaining to EYLEA are subject to post-grant proceedings before the United States Patent and Trademark Office ("USPTO"), EPO, or other comparable foreign authorities, including those described in greater detail below. In addition, the Company has filed patent infringement lawsuits in several jurisdictions alleging infringement of certain Company patents pertaining to EYLEA, including those described in greater detail below. United States Post-Grant Proceedings Before USPTO Company Patent(s) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status U.S. Patent Nos. 10,406,226 (the "'226 Patent") and 10,464,992 (the "'992 Patent") Anonymous parties Ex parte reexamination February 11, 2020 On September 11, 2023, the USPTO dismissed the '226 Patent reexamination proceedings following the Company's filing of a Notice of Disclaimer, disclaiming all claims of the '226 Patent. On September 8, 2023, the '992 Patent reexamination proceedings were stayed by the USPTO pending resolution of the inter partes review ("IPR") of the '992 Patent initiated by Celltrion, Inc., as discussed further below. On January 17, 2024, the Company filed a Notice of Disclaimer with the USPTO, disclaiming all claims of the '992 Patent. Company Patent(s) (continued) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status U.S. Patent Nos. 9,254,338 (the "'338 Patent") and 9,669,069 (the "'069 Patent") Mylan Pharmaceuticals Inc., joined by Apotex Inc. and Celltrion IPR petitions seeking declarations of invalidity May 5, 2021 On November 9, 2022, the USPTO issued final written decisions finding that the challenged claims of the '338 and '069 Patents are unpatentable and, therefore, invalid. On January 10, 2023, the Company filed notices of appeal of the USPTO written decisions concerning the '338 and '069 Patents with the Federal Circuit. U.S. Patent Nos. 10,130,681 (the "'681 Patent"), 10,888,601 (the "'601 Patent"), and 10,857,205 (the "'205 Patent") Mylan, joined by Celltrion ('601 and '681 Patents) and Samsung Bioepis Co., Ltd. ('601 Patent) IPR petitions seeking declarations of invalidity July 1, 2022 ('681 Patent and '601 Patent) October 28, 2022 ('205 Patent) On January 9, 2024, the USPTO issued final written decisions finding that that the challenged claims of the '681 and '601 Patents are unpatentable and, therefore, invalid. On March 1, 2023, the USPTO denied institution of Mylan's IPR petition against the '205 Patent following the Company's filing of a Notice of Disclaimer with the USPTO, disclaiming all claims of the '205 Patent. '681 Patent and '601 Patent Samsung Bioepis, joined by Biocon Biologics Inc. ('601 Patent) IPR petitions seeking declarations of invalidity January 6, 2023 ('681 Patent) March 26, 2023 ('601 Patent) On July 19, 2023 and October 20, 2023, the USPTO instituted IPR proceedings concerning the '681 Patent and the '601 Patent, respectively. U.S. Patent No. 11,253,572 (the "'572 Patent") Apotex IPR petition seeking declaration of invalidity September 9, 2022 On March 10, 2023, the USPTO declined to institute an IPR proceeding based on the Apotex IPR petition. Samsung Bioepis IPR petition seeking declaration of invalidity April 27, 2023 On November 17, 2023, the USPTO instituted IPR proceedings concerning the '572 Patent based on the Samsung IPR petition. '992 Patent and '226 Patent Celltrion, joined by Samsung Bioepis ('992 Patent) IPR petitions seeking declarations of invalidity January 17, 2023 ('992 Patent) February 28, 2023 ('226 Patent) On July 20, 2023, the USPTO instituted an IPR proceeding concerning the '992 Patent. On January 17, 2024, the Company filed a Notice of Disclaimer with the USPTO, disclaiming all claims of the '992 Patent. On September 1, 2023, the USPTO denied institution of Celltrion's IPR petition against the '226 Patent following the Company's filing of a Notice of Disclaimer with the USPTO, disclaiming all claims of the '226 Patent. U.S. Patent Litigation On August 2, 2022, the Company filed a patent infringement lawsuit against Mylan, a wholly-owned subsidiary of Viatris Inc., in the United States District Court for the Northern District of West Virginia alleging that Mylan's filing for FDA approval of an aflibercept 2 mg biosimilar infringes certain Company patents. On April 20, 2023, Mylan filed a motion for summary judgment or partial summary judgment concerning four of the asserted patents. On April 26, 2023, the Company filed a stipulation accepting summary judgment of noninfringement of all asserted claims of the Company's U.S. Patent No. 11,104,715. On June 5, 2023, Biocon, as successor-in-interest to the aflibercept 2 mg biosimilar, was joined as a defendant to the lawsuit. A trial was held from June 12, 2023 through June 23, 2023 concerning certain claims of the '601 Patent, the '572 Patent, and the Company's U.S. Patent No. 11,084,865 (the "'865 Patent"). Closing arguments were presented on August 3, 2023. On December 27, 2023, the court issued a decision finding that (i) the asserted claims of the '865 Patent were valid and infringed by Mylan and (ii) the asserted claims of the '601 and '572 Patents were infringed by Mylan but were invalid as obvious. On November 8, November 22, and November 29, 2023, respectively, the Company filed patent infringement lawsuits against Celltrion, Samsung Bioepis, and Formycon AG in the United States District Court for the Northern District of West Virginia following service on Regeneron of each company's notice of commercial marketing. The lawsuits allege that each company has infringed certain Company patents, including based on each company's filing for FDA approval of an aflibercept 2 mg biosimilar. On December 27, 2023, the Company filed a second patent infringement lawsuit against Samsung Bioepis in the United States District Court for the Northern District of West Virginia alleging that Samsung's filing for FDA approval of an aflibercept 2 mg biosimilar infringes certain Company patents. A preliminary injunction hearing concerning each of these lawsuits has been scheduled for May 2, 2024. On January 10, 2024, the Company filed a patent infringement lawsuit against Amgen in the United States District Court for the Central District of California alleging that Amgen's filing for FDA approval of an aflibercept 2 mg biosimilar infringes certain Company patents. On January 11, 2024, the Company filed a motion with the United States Judicial Panel on Multidistrict Litigation seeking to transfer this lawsuit to the United States District Court for the Northern District of West Virginia for coordinated pretrial proceedings with the lawsuits described in the preceding paragraph. A hearing on the motion to transfer has been scheduled for March 28, 2024. Europe Post-Grant Proceedings Authority/Court Company Patent(s) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status EPO European Patent No. 2,944,306 (the "'306 Patent") Anonymous parties Opposition proceedings October 26 and October 27, 2021 Oral hearing to be scheduled. EPO European Patent No. 3,716,992 (the "EP '992 Patent") Amgen and three anonymous parties Opposition proceedings May 5-10, 2023 Oral hearing to be scheduled. German Federal Patent Court German designation of European Patent No. 2,364,691 (the "'691 Patent") Samsung Bioepis NL B.V. Invalidation proceedings June 22, 2023 Trial has been scheduled to begin in June 2025. Canada On June 15, July 15, August 30, and October 4, 2022, the Company and Bayer Inc. filed patent infringement lawsuits against BGP Pharma ULC d.b.a Viatris Canada ("Viatris Canada") in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's Canadian Patent Nos. 2,654,510 (the "'510 Patent") and 3,007,276 (the "'276 Patent") (in the lawsuit filed on June 15, 2022); the Company's Canadian Patent No. 2,965,495 (the "'495 Patent") (in the lawsuit filed on July 15, 2022); the Company's Canadian Patent No. 2,906,768 (the "'768 Patent") (in the lawsuit filed on August 30, 2022, which has been joined with the lawsuit filed on July 15, 2022); and the Company's Canadian Patent No. 3,129,193 (the "'193 Patent") (in the lawsuit filed on October 4, 2022). A trial for the lawsuit concerning the '510 Patent and the '276 Patent (the "Viatris Canada 510/276 Lawsuit") has been scheduled for March 2024; a trial for the lawsuit concerning the '193 Patent has been scheduled for May 2024; and a trial for the lawsuit concerning the '495 Patent and the '768 Patent has been scheduled for November/December 2024. The filing of the Viatris Canada 510/276 Lawsuit resulted in a statutory 24-month stay of regulatory approval of Viatris Canada's aflibercept 2 mg biosimilar in Canada unless the lawsuit is resolved earlier. On March 27, 2023, in light of the transfer of Viatris Canada's New Drug Submission ("NDS") of its aflibercept 2 mg biosimilar to Biosimilar Collaborations Ireland Limited ("BCIL"), the Company filed a motion in the Federal Court of Canada seeking termination of the Viatris Canada 510/276 Lawsuit. On June 5, 2023, BCIL was added as a defendant in the Viatris Canada 510/276 Lawsuit. On March 23, 2023 and June 14, 2023, the Company and Bayer Inc. filed patent infringement lawsuits against BCIL in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's '510 and '276 Patents. The June 14, 2023 lawsuit was filed after BCIL served Bayer Inc. with a statutory notification in relation to the NDS on May 23, 2023. On September 14, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Viatris Canada and BCIL in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of Bayer Healthcare LLC's Canadian Patent No. 2,970,315 (the "'315 Patent"). On May 9, 2023, Amgen Canada Inc. ("Amgen Canada") filed invalidation proceedings against the Company in the Federal Court of Canada seeking revocation of the '510 Patent and the '276 Patent. On September 14, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the '315 Patent. On September 14, 2023, the Company and Bayer Inc. filed three separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's '193 Patent, '495 Patent, and '768 Patent, respectively. On October 11, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed two separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's '510 Patent and '276 Patent, respectively. A trial for the lawsuits concerning the '510 Patent and the '276 Patent has been scheduled for May 2025. On January 15, 2024, the Company and Bayer Inc. filed patent infringement lawsuits against Celltrion, Inc., Celltrion Healthcare Co, Ltd., Celltrion Pharma Inc., and Celltrion Healthcare Canada Ltd. in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the '510 Patent, the '276 Patent, the '495 Patent, the '768 Patent, the '193 Patent, and the '315 Patent. South Korea On October 31, 2022 and December 13, 2022, Samsung Bioepis Co., Ltd. initiated invalidation proceedings before the Intellectual Property Trial and Appeal Board of the Korean Intellectual Property Office against the Company's Korean Patent Nos. 1131429 and 1406811, respectively, seeking revocation of each of such patents in its entirety. On January 16, 2023, the Company filed patent infringement lawsuits against Samsung Bioepis Co., Ltd. and its parent company Samsung Biologics Co., Ltd. before the Seoul Central District Court seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would infringe one or more claims of the Company's Korean Patent No. 659477 (the "'477 Patent"). On July 20, 2023, the Company filed a preliminary injunction petition against Samsung Bioepis Co., Ltd. and its parent company Samsung Biologics Co., Ltd. before the Seoul Central District Court seeking a court order enjoining the manufacture, use, and assignment of an aflibercept 2 mg biosimilar that infringes one or more claims of the '477 Patent; and on December 20, 2023, the Seoul Central District Court granted a preliminary injunction. On January 10, 2024, the injunction was lifted against the Samsung entities following the expiration of the '477 Patent. On March 2, 2023, the Company filed an affirmative scope confirmation action against Samsung Bioepis Co., Ltd. before the Intellectual Property Tribunal and Appeal Board of the Korean Intellectual Property Office seeking a ruling that Samsung Bioepis's aflibercept 2 mg biosimilar is covered by the claims of the '477 Patent. On March 7, 2023, the action was designated for expedited proceedings. Proceedings Relating to EYLEA (aflibercept) Injection Pre-filled Syringe On June 19, 2020, Novartis Pharma AG, Novartis Pharmaceuticals Corporation, and Novartis Technology LLC (collectively, "Novartis") filed a patent infringement lawsuit (as amended on August 2, 2021) in the U.S. District Court for the Northern District of New York asserting claims of Novartis's U.S. Patent No. 9,220,631 (the "'631 Patent") and seeking preliminary and permanent injunctions to prevent the Company from continuing to infringe the '631 Patent. Novartis also seeks a judgment of patent infringement of the '631 Patent, monetary damages (together with interest), an order of willful infringement of the '631 Patent (which would allow the court in its discretion to award damages up to three times the amount assessed), costs and expenses of the lawsuits, and attorneys' fees. On November 7, 2022, the Company and Novartis entered into a stipulation staying the lawsuit in light of the decision in the IPR proceeding discussed below. On July 16, 2020, the Company initiated two IPR petitions in the USPTO seeking a declaration of invalidity of the '631 Patent on two separate grounds. On October 26, 2021, the USPTO issued a decision instituting the IPR proceeding. An oral hearing was held on July 21, 2022. On October 25, 2022, the Patent Trial and Appeal Board ("PTAB") of the USPTO issued a final written decision invalidating all claims of the '631 Patent. On December 23, 2022, Novartis filed a notice of appeal of the PTAB's decision to the Federal Circuit. On July 17, 2020, the Company filed an antitrust lawsuit against Novartis and Vetter Pharma International Gmbh ("Vetter") in the United States District Court for the Southern District of New York seeking a declaration that the '631 Patent is unenforceable and a judgment that the defendants' conduct violates Sections 1 and 2 of the Sherman Antitrust Act of 1890, as amended (the "Sherman Antitrust Act"). The Company is also seeking injunctive relief and treble damages. On September 4, 2020, Novartis filed, and Vetter moved to join, a motion to dismiss the complaint, to transfer the lawsuit to the Northern District of New York, or to stay the suit; and on October 19, 2020, Novartis filed, and Vetter moved to join, a second motion to dismiss the complaint on different grounds. On January 25, 2021, the Company filed an amended complaint seeking a judgment that Novartis's conduct violates Section 2 of the Sherman Antitrust Act based on additional grounds, as well as a judgment of tortious interference with contract. On February 22, 2021, Novartis filed, and Vetter moved to join, a motion to dismiss the amended complaint. On September 21, 2021, the court granted Novartis and Vetter's motion to transfer this lawsuit to the Northern District of New York. As a result, this lawsuit was transferred to the same judge that had been assigned to the patent infringement lawsuit discussed above. On November 5, 2021, the Company filed a motion to stay these proceedings in light of the pending IPR proceeding discussed above. On January 31, 2022, the court denied the Company's motion to stay these proceedings and granted Novartis and Vetter's motion to dismiss the amended complaint. On June 10, 2022, the Company filed an appeal of the District Court's decision to dismiss the amended complaint with the U.S. Court of Appeals for the Second Circuit. An oral hearing before the U.S. Court of Appeals for the Second Circuit was held on October 11, 2023. Proceedings Relating to REGEN-COV (casirivimab and imdevimab) On October 5, 2020, Allele Biotechnology and Pharmaceuticals, Inc. ("Allele") filed a lawsuit (as amended on April 8, 2021 and December 12, 2022) against the Company in the United States District Court for the Southern District of New York, asserting infringement of U.S. Patent No. 10,221,221 (the "'221 Patent"). Allele seeks a judgment of patent infringement of the '221 Patent, an award of monetary damages (together with interest), an order of willful infringement of the '221 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. On July 16, 2021, the Company filed a motion to dismiss the complaint, which motion was denied on March 2, 2022. On September 18, 2023, the parties entered into a stipulation that narrowed the case to (i) whether any safe harbor defense under federal law applies to Regeneron's use of the invention covered, based on the court's claim construction, by the '221 Patent; (ii) damages for any use by Regeneron found to not be covered by such safe harbor defense; and (iii) whether any use referred to in clause (ii) above was willful. Department of Justice Matters 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. On June 24, 2020, the U.S. Attorney's Office for the District of Massachusetts filed a civil complaint in the U.S. District Court for the District of Massachusetts alleging violations of the federal Anti-Kickback Statute, and asserting causes of action under the federal False Claims Act and state law. On August 24, 2020, the Company filed a motion to dismiss the complaint in its entirety. On December 4, 2020, the court denied the motion to dismiss. On December 28, 2022, the U.S. Attorney’s Office for the District of Massachusetts filed a motion for partial summary judgment. On January 31, 2023, the Company filed a motion for summary judgment. An oral hearing on the parties' respective motions for summary judgment was held on July 21, 2023. On September 27, 2023, the court (i) denied in part and granted in part the Company's motion for summary judgment and (ii) denied in its entirety the motion for partial summary judgment filed by the U.S. Attorney's Office for the District of Massachusetts. On October 25, 2023, the court certified for interlocutory appeal a portion of the court's September 27, 2023 order that addressed the causation standard applicable to the alleged violations of the federal Anti-Kickback Statute and federal False Claims Act; and on December 11, 2023, the U.S. Court of Appeals for the First Circuit certified for appeal the court's September 27, 2023 order. 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. On June 3, 2021, the United States District Court for the Central District of California unsealed a qui tam complaint filed against the Company, Regeneron Healthcare Solutions, Inc., and Sanofi-Aventis U.S. LLC by two qui tam plaintiffs (known as relators) purportedly on behalf of the United States and various states (the "State Plaintiffs"), asserting causes of action under the federal False Claims Act and state law. Also on June 3, 2021, the United States and the State Plaintiffs notified the court of their decision to decline to intervene in the case. On October 29, 2021, the qui tam plaintiffs filed an amended complaint in this matter. On January 14, 2022, the Company filed a motion to dismiss the amended complaint in its entirety. On July 25, 2023, the court in part granted and in part denied the Company's motion to dismiss. On September 1, 2023, the Company filed a second motion to dismiss the amended complaint or, in the alternative, a motion for judgment on the pleadings. A trial has been scheduled for April 2025. In June 2021, the Company received a CID from the U.S. Department of Justice pursuant to the federal False Claims Act. The CID states that the investigation concerns allegations that the Company (i) violated the False Claims Act by paying kickbacks to distributors and ophthalmology practices to induce purchase of EYLEA, including through discounts, rebates, credit card fees, free units of EYLEA, and inventory management systems; and (ii) inflated reimbursement rates for EYLEA by excluding applicable discounts, rebates, and benefits from the average sales price reported to the Centers for Medicare & Medicaid Services. The CID covers the period from January 2011 through June 2021. The Company is cooperating with this investigation. On November 29, 2023, the U.S. Department of Justice informed the Company that it had filed a notice of partial intervention in this matter. California Department of Insurance Subpoena In September 2022, the Company received a subpoena from the Insurance Commissioner for the State of California pursuant to the California Insurance Code. The subpoena seeks information relating to the marketing, sale, and distribution of EYLEA, including (i) discounts, rebates, credit card fees, and inventory management systems; (ii) Regeneron's relationships with distributors; (iii) price reporting; (iv) speaker programs; and (v) patient support programs. The subpoena covers the period from January 1, 2014 through August 1, 2021. The Company is cooperating with this investigation. Proceedings Initiated by Other Payors Relating to Patient Assistance Organization Support The Company is party to several lawsuits relating to the conduct alleged in the civil complaint filed by the U.S. Attorney's Office for the District of Massachusetts discussed under "Department of Justice Matters" above. These lawsuits were filed by UnitedHealthcare Insurance Company and United Healthcare Services, Inc. (collectively, "UHC") and Humana Inc. ("Humana") in the United States District Court for the Southern District of New York on December 17, 2020 and July 22, 2021, respectively; and by Blue Cross and Blue Shield of Massachusetts, Inc. and Blue Cross and Blue Shield of Massachusetts HMO Blue, Inc. (collectively, "BCBS"), Medical Mutual of Ohio ("MMO"), Horizon Healthcare Services, Inc. d/b/a Horizon Blue Cross Blue Shield of New Jersey ("Horizon"), and Local 464A United Food and Commercial Workers Union Welfare Service Benefit Fund ("Local 464A") in the U.S. District Court for the District of Massachusetts on December 20, 2021, February 23, 2022, April 4, 2022, and June 17, 2022, respectively. These lawsuits allege causes of action under state law and the federal Racketeer Influenced and Corrupt Organizations Act and seek monetary damages and equitable relief. The MMO and Local 464A lawsuits are putative class action lawsuits. On December 29, 2021, the lawsuits filed by UHC and Humana were stayed by the United States District Court for the Southern District of New York pending resolution of the proceedings before the U.S. District Court for the District of Massachusetts discussed under "Department of Justice Matters" above. On September 27, 2022, the lawsuits filed by BCBS, MMO, and Horizon were stayed by the U.S. District Court for the District of Massachusetts pending resolution of the proceedings before the same court discussed under "Department of Justice Matters" above; and, in light of these stays, the parties to the Local 464A action have also agreed to stay that matter. Proceedings Relating to Shareholder Derivative Complaint

Net Income Per Share

Net Income Per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Income Per Share	Net Income Per Share The calculations of basic and diluted net income per share are as follows: Year Ended December 31, (In millions, except per share data) 2023 2022 2021 Net income - basic and diluted $ 3,953.6 $ 4,338.4 $ 8,075.3 Weighted average shares - basic 106.7 107.1 105.7 Effect of dilutive securities: Stock options 4.9 4.9 5.4 Restricted stock awards and restricted stock units 2.1 1.5 1.1 Weighted average shares - diluted 113.7 113.5 112.2 Net income per share - basic $ 37.05 $ 40.51 $ 76.40 Net income per share - diluted $ 34.77 $ 38.22 $ 71.97 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) 2023 2022 2021 Stock options 1.8 2.3 2.9

Statement of Cash Flows

Statement of Cash Flows	12 Months Ended
	Dec. 31, 2023
Cash and Cash Equivalents [Abstract]
Statement of Cash Flows	Statement of Cash Flows The following provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheet to the total of the same such amounts shown in the Consolidated Statement of Cash Flows: December 31, (In millions) 2023 2022 2021 Cash and cash equivalents $ 2,730.0 $ 3,105.9 $ 2,885.6 Restricted cash included in Other noncurrent assets 7.8 13.5 12.5 Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows $ 2,737.8 $ 3,119.4 $ 2,898.1 Restricted cash consists of amounts held by financial institutions pursuant to contractual arrangements. Supplemental disclosure of non-cash investing and financing activities As of December 31, (In millions) 2023 2022 2021 Accrued capital expenditures $ 75.4 $ 70.8 $ 74.8 Accrued contingent consideration in connection with acquisitions $ 71.6 $ 135.5 $ —

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net income	$ 3,953.6	$ 4,338.4	$ 8,075.3

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended	12 Months Ended
	Dec. 31, 2023 shares	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		As disclosed in the table below, during the three months ended December 31, 2023, certain of our directors and/or executive officers adopted plans for trading arrangements intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) of the Exchange Act. Name Position Date of Plan Adoption Scheduled End Date of Trading Arrangement (a) Total Number of Securities to Be Sold Under the Plan Robert E. Landry Executive Vice President, Finance and Chief Financial Officer 11/9/2023 5/6/2024 14,337 (a) The trading arrangement may expire on an earlier date if and when all transactions under the arrangement are completed.
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Robert E. Landry [Member]
Trading Arrangements, by Individual
Name	Robert E. Landry
Title	Executive Vice President, Finance and Chief Financial Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	11/9/2023
Arrangement Duration	179 days
Aggregate Available	14,337	14,337

Business Overview and Summary_2

Business Overview and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	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.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments which potentially expose the Company to concentrations of credit risk consist of cash, cash equivalents, certain investments, and accounts receivable. In accordance with the Company's policies, the Company mandates asset diversification and monitors exposure with its counterparties.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid debt instruments with a maturity of three months or less when purchased to be cash equivalents. The carrying amount reported in the Consolidated Balance Sheet for cash and cash equivalents approximates its fair value.
Debt and Equity Securities	Debt and Equity Securities The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and diversification. The Company invests its cash primarily in debt securities. The Company considers its 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. 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 have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, a loss is recognized in net income, whereas if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss).
Accounts Receivable	Accounts Receivable
Inventories	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 inventory to its estimated realizable value.
Property, Plant and Equipment	Property, Plant, and Equipment Property, plant, and equipment are stated at cost, net of accumulated depreciation. Depreciation is 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 within income from 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
Leases	Leases The Company determines 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. The Company may include options to extend or terminate a lease within the lease term when it is reasonably certain that it will exercise that option. The Company accounts for lease components (e.g., rental payments) separately from non-lease components (e.g., common area maintenance costs). Lease liabilities are recognized at the lease commencement date based on the present value of the remaining lease payments, discounted using the rate implicit in the lease. For leases where an implicit rate is not readily determinable, the Company uses its 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. The Company conducts certain of its research, development, and administrative activities at leased facilities. The Company also leases vehicles and other assets. Tarrytown, New York Lease The Company is party to a Third Amended and Restated Lease and Remedies Agreement (the "Third Amended and Restated Lease") with BA Leasing BSC, LLC, an affiliate of Banc of America Leasing & Capital, LLC ("BAL"), as lessor, which relates to the Company’s lease of laboratory and office facilities in Tarrytown, New York (the “Facility”); and a Third Amended and Restated Participation Agreement (the "Third Amended and Restated Participation Agreement") with Bank of America, N.A., as administrative agent (the "Administrative Agent"), and a syndicate of lenders (collectively with BAL, the "Participants"), as rent assignees. The Third Amended and Restated Lease and Third Amended and Restated Participation Agreement provide for a March 2027 maturity date of the $720.0 million lease financing (previously advanced by the Participants in March 2017 in connection with the acquisition by BAL of the Facility and the Company's lease of the Facility from BAL) and the end of the term of the Company's lease of the Facility from BAL, at which time all amounts outstanding thereunder will become due and payable in full. In accordance with the terms of the Third Amended and Restated Lease, the Company pays all maintenance, insurance, taxes, and other costs arising out of the use of the Facility. The Company is also required to make monthly payments of basic rent during the remaining term of the Third Amended and Restated Lease to satisfy the yield payable to the Participants on their outstanding advances under the Third Amended and Restated Participation Agreement. Such advances accrue yield at a variable rate per annum based on the one-month forward-looking Secured Overnight Financing Rate ("SOFR") term rate, plus a spread adjustment, plus an applicable margin that varies with the Company's debt rating and total leverage ratio. The Third Amended and Restated Participation Agreement and Third Amended and Restated Lease include an option for the Company to elect to further extend the maturity date of the Third Amended and Restated Participation Agreement and the term of the Third Amended and Restated Lease for an additional five-year period, subject to the consent of all the Participants and certain other conditions. The Company also has the option prior to the end of the term of the Third Amended and Restated Lease to (a) purchase the Facility by paying an amount equal to the outstanding principal amount of the Participants' advances under the Third Amended and Restated Participation Agreement, all accrued and unpaid yield thereon, and all other outstanding amounts under the Third Amended and Restated Participation Agreement, Third Amended and Restated Lease, and certain related documents or (b) sell the Facility to a third party on behalf of BAL. The Third Amended and Restated Lease is classified as a finance lease as the Company has the option to purchase the Facility under terms that make it reasonably certain to be exercised. The agreements governing the Third Amended and Restated Lease financing contain financial and operating covenants. Such financial covenants and certain of the operating covenants are substantially similar to the covenants set forth in the 2022 Credit Agreement. The Company was in compliance with all such covenants as of December 31, 2023.
Acquisitions	Acquisitions The Company makes a determination whether a transaction should be accounted for as a business combination or as an asset acquisition. In a business combination, the acquisition method of accounting generally requires that the assets acquired and liabilities assumed be recorded as of the date of the acquisition at their respective fair values. Amounts allocated to acquired in-process research and development are capitalized as indefinite-lived intangible assets. Any excess of the purchase price (consideration transferred) over the fair values of net assets acquired is recorded as goodwill. In a business combination, contingent consideration obligations are recorded at fair value as of the acquisition date and remeasured each subsequent reporting period until the contingencies have been resolved, with any changes in fair value recorded in Other operating (income) expense, net. If it is determined that the assets acquired do not meet the definition of a business, or if substantially all of the fair value of the assets acquired are concentrated in a single identifiable asset, then the transaction is accounted for as an asset acquisition rather than a business combination. In an asset acquisition, assets acquired are recorded at cost, goodwill is not recognized, and acquired in-process research and development with no alternative future use is charged to expense.
Intangible Assets	Intangible Assets Intangible assets acquired in a business combination are recorded at fair value, while intangible assets acquired in connection with an asset acquisition are recorded at cost. Payments to acquire intangible assets in an asset acquisition may include up-front payments and contingent consideration. With regard to contingent consideration in an asset acquisition, the Company recognizes regulatory milestones upon achievement, royalties in the period in which the underlying sales occur, and sales-based milestones when the milestone is deemed probable by the Company of being achieved. If contingent consideration is recognized subsequent to the acquisition date in an asset acquisition, the amount of such consideration is recorded as an addition to the cost basis of the intangible asset with a cumulative catch-up adjustment for amortization expense as if the additional amount of consideration had been accrued from the outset of the acquisition. Indefinite-lived intangible assets are subject to impairment testing until completion or abandonment of the associated research and development efforts. Definite-lived intangible assets are amortized to Cost of goods sold over the estimated useful lives of the assets based on the pattern in which the economic benefits of the intangible assets are consumed; if that pattern cannot be reliably determined, a straight-line basis is used. Intangible assets are reviewed for recoverability whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. If an indicator of impairment exists, the Company compares the projected undiscounted cash flows to be generated by the asset to the intangible asset's carrying amount. If the projected undiscounted cash flows of the intangible asset are less than the carrying amount, the intangible asset is written down to its fair value in the period in which the impairment occurs.
Revenue Recognition	Product Revenue Revenue from product sales is recognized at a point in time when the Company's customer is deemed to have obtained control of the product, which generally occurs upon receipt or acceptance by its customer. The amount of revenue the Company recognizes from product sales may vary 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, the Company estimates, utilizing the expected value method, the amount of variable consideration to which the Company will be entitled. This estimate is based upon contracts with customers, healthcare providers, payors, 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: The Company's rebates include amounts paid to managed care organizations, group purchasing organizations, state Medicaid programs, and other rebate programs. The Company estimates reductions to product sales for each type of rebate and records an allowance for rebates in the same period in which the related product sales are recognized. The Company's liability for rebates consists of estimates for claims related to the current and prior periods that have not been paid and estimates for claims that will be made related to product that exists in the distribution channel at the end of the period. • Chargebacks and Discounts: The Company's reserves related to discounted pricing to eligible physicians, Veterans' Administration ("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 discounted selling price to the qualified healthcare providers. The Company estimates reductions to product sales for each type of chargeback and records an allowance for chargebacks in the same period that the related product sales are recognized. The Company's reserve for chargebacks consists of amounts for which it expects to issue credit based on expected sales by its customers to qualified healthcare providers and chargebacks that customers have claimed but for which the Company has not yet issued credit. • 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's other sales-related deductions include co-pay assistance programs and product returns. The Company estimates and records other sales-related deductions generally based on gross sales, written contracts, and other relevant factors. Consistent with industry practice, the Company generally offers its customers a limited right to return product purchased directly from the Company, which is principally based upon the product's 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, 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. Collaborative Arrangements The Company has entered into various collaborative arrangements to research, develop, manufacture, and commercialize products and/or product candidates. Although each of these arrangements is unique in nature, such arrangements involve a joint operating activity where both parties are active participants in the activities of the collaboration and exposed to significant risks and rewards dependent on the commercial success of the activities. In arrangements where the Company does not deem its collaborator to be its customer, payments to and from its collaborator are presented in the Company's statement of operations based on the nature of our business operations, the nature of the arrangement, including the contractual terms, and the nature of the payments. In general, the presentation of such amounts is summarized below. Nature/Type of Payment Statement of Operations Presentation Regeneron's share of profits or losses in connection with commercialization of products Collaboration revenue Reimbursement for manufacturing of commercial supplies Collaboration revenue Royalties and/or sales-based milestones earned Collaboration revenue Reimbursement of Regeneron's research and development expenses Reduction to Research and development expenses Regeneron's obligation for its share of collaborator's research and development expenses Research and development expense Up-front/opt-in and development milestone payments to collaborators Acquired in-process research and development expense Reimbursement of Regeneron's commercialization-related expenses Reduction to Selling, general, and administrative expense Regeneron's obligation for its share of collaborator's commercialization-related expenses Selling, general, and administrative expense Regeneron's obligation to pay collaborator for its share of gross profits when Regeneron is deemed to be the principal Cost of goods sold Up-front and development milestones earned (when there is a combined unit of account which includes a license and providing research and development services) Other operating income In agreements involving multiple goods or services promised to be transferred to the Company's collaborator, the Company assesses, at the inception of the contract, whether each promise represents a separate obligation (i.e., is "distinct"), or whether such promises should be combined as a single unit of account. When the Company has a combined unit of account which includes a license and providing research and development services to its collaborator, recognition of up-front payments and development milestones earned from its collaborator is deferred (as a liability) and recognized over the development period (i.e., over time) typically using an input method on the basis of the Company's research and development costs incurred relative to the total expected cost which determines the extent of the Company's progress toward completion. The Company reviews its estimates each period and makes revisions to such estimates as necessary. When the Company is entitled to reimbursement of all or a portion of the expenses (e.g., research and development expenses) that it incurs under a collaboration, it records those reimbursable amounts in the period in which such costs are incurred. If the Company's collaborator performs research and development work or commercialization-related activities and the parties share the related costs, the Company also recognizes, as expense (e.g., research and development expense or selling, general, and administrative expense, as applicable) in the period when its collaborator incurs such expenses, the portion of the collaborator's expenses that the Company is obligated to reimburse. The Company's collaborators provide the Company with estimated expenses for the most recent fiscal quarter. The estimates are revised, if necessary, in subsequent periods if actual expenses differ from those estimates. 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. In arrangements where the Company: • supplies commercial product to its collaborator, the Company may be reimbursed for its manufacturing costs as commercial product is shipped to the collaborator (however, recognition of such cost reimbursements may be deferred until the product is sold by the Company's collaborator to third-party customers); • shares in any profits or losses arising from the commercialization of such products, the Company records its share of the variable consideration, representing net product sales less cost of goods sold and shared commercialization and other expenses, in the period in which such underlying sales occur and costs are incurred by the collaborator; • receives royalties and/or sales-based milestone payments from its collaborator, the Company recognizes such amounts in the period earned.
Research and Development Expenses	Research and Development Expenses Research and development expenses include costs 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, clinical trial expenses, the cost of services provided by outside contractors, including services related to the Company's clinical trials, the cost of manufacturing drug for use in research and development, 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. Costs associated with research and development are expensed.
Stock-based Compensation	Stock-based Compensation The Company recognizes stock-based compensation expense for equity grants under the Company's long-term incentive plans (including stock options, restricted stock awards, and restricted stock units (both time-based and performance-based)) 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. 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. In addition, the Company reassesses its forfeiture rate assumptions at least annually, considering both historical forfeiture experience and an estimate of future forfeitures for currently outstanding unvested awards. The Company uses the Black-Scholes model to compute the estimated fair value of stock option awards. Additionally, the Company uses a Monte Carlo simulation to compute the estimated fair value of performance-based restricted stock units that are subject to vesting based on the Company’s attainment of pre-established criteria that include a market condition. For performance-based restricted stock units that contain a performance condition, the Company recognizes stock-based compensation expense if and when the Company determines that it is probable the performance condition will be achieved (based on the number of shares expected to be vested and issued). The Company reassesses the probability of achievement at each reporting period and adjusts compensation cost, as necessary. If there are any changes in the Company's probability assessment, the Company recognizes a cumulative catch-up adjustment in the period of the change in estimate, with the remaining unrecognized expense recognized prospectively over the remaining requisite service period. If the Company subsequently determines that the performance criteria are not met or are not expected to be met, any amounts previously recognized as compensation expense are reversed in the period when such determination is made.
Income Taxes	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 are recognized 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. Deferred tax assets and liabilities are determined as 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. The Company recognizes the financial statement effects of a tax position when management's assessment is that there is more than a 50% probability that the position will be sustained upon examination by a taxing authority based upon its technical merits. Uncertain tax positions are recorded based upon 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, the effective settlement of matters subject to audit, information obtained during in-process audit activities, and changes in facts or circumstances related to a tax position. The Company adjusts the amount of the liability to reflect any subsequent changes in the relevant facts and circumstances surrounding the uncertain tax positions. The Company recognizes interest and penalties related to income tax matters in income tax expense.
Per Share Data	Per Share Data Basic net income per share is computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Basic net income per share excludes restricted stock 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 outstanding stock options and unvested restricted stock under the Company's long-term incentive plans, which are included under the treasury stock method when dilutive.
Legal Matters	Costs associated with the Company's involvement in legal proceedings are expensed as incurred
Recently Issued Accounting Standards	Recently Issued Accounting Standards In November 2023, the FASB issued Accounting Standards Update No. 2023-07, Segment Reporting - Improvements to Reportable Segment Disclosures . The amendments require disclosure of incremental segment information on an annual and interim basis. The amendments also require companies with a single reportable segment to provide all disclosures required by this amendment and all existing segment disclosures in Accounting Standards Codification 280, Segment Reporting . The amendments are effective for fiscal years beginning after December 15, 2023, and interim periods beginning after December 15, 2024. The Company does not expect the adoption of the amendments to have a significant impact on its financial statements. In December 2023, the FASB issued Accounting Standards Update No. 2023-09, Income Taxes - Improvements to Income Tax Disclosures . The amendments require (i) enhanced disclosures in connection with an entity's effective tax rate reconciliation and (ii) income taxes paid disaggregated by jurisdiction. The amendments are effective for annual periods beginning after December 15, 2024. The Company does not expect the adoption of the amendments to have a significant impact on its financial statements.

Business Overview and Summary_3

Business Overview and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
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, net consists of the following: As of December 31, (In millions) 2023 2022 Building and improvements $ 2,423.1 $ 2,270.0 Leasehold improvements 133.9 114.3 Laboratory equipment 1,384.5 1,315.3 Computer equipment and software 389.7 337.4 Furniture, office equipment, and other 165.9 150.2 Land 283.1 264.5 Construction in progress 1,345.0 980.5 6,125.2 5,432.2 Accumulated depreciation and amortization (1,978.8) (1,669.2) $ 4,146.4 $ 3,763.0
Summary of presentation in statement of operations of payments to and from collaborators	In arrangements where the Company does not deem its collaborator to be its customer, payments to and from its collaborator are presented in the Company's statement of operations based on the nature of our business operations, the nature of the arrangement, including the contractual terms, and the nature of the payments. In general, the presentation of such amounts is summarized below. Nature/Type of Payment Statement of Operations Presentation Regeneron's share of profits or losses in connection with commercialization of products Collaboration revenue Reimbursement for manufacturing of commercial supplies Collaboration revenue Royalties and/or sales-based milestones earned Collaboration revenue Reimbursement of Regeneron's research and development expenses Reduction to Research and development expenses Regeneron's obligation for its share of collaborator's research and development expenses Research and development expense Up-front/opt-in and development milestone payments to collaborators Acquired in-process research and development expense Reimbursement of Regeneron's commercialization-related expenses Reduction to Selling, general, and administrative expense Regeneron's obligation for its share of collaborator's commercialization-related expenses Selling, general, and administrative expense Regeneron's obligation to pay collaborator for its share of gross profits when Regeneron is deemed to be the principal Cost of goods sold Up-front and development milestones earned (when there is a combined unit of account which includes a license and providing research and development services) Other operating income

Product Sales (Tables)

Product Sales (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Schedule of product sales	Net product sales consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 EYLEA ® HD U.S. $ 165.8 $ — $ — EYLEA ® U.S. 5,719.6 6,264.6 5,792.3 Total EYLEA HD and EYLEA U.S. 5,885.4 6,264.6 5,792.3 Libtayo ®(a) U.S. 538.8 374.5 306.3 Libtayo (a) ROW (b) 324.3 73.0 — Total Libtayo Global 863.1 447.5 306.3 Praluent ® U.S. 182.4 130.0 170.0 REGEN-COV ®(c) U.S. — — 5,828.0 Evkeeza ® U.S. 77.3 48.6 18.4 Inmazeb ® U.S. 69.8 3.0 — ARCALYST ®(d) U.S. — — 2.2 $ 7,078.0 $ 6,893.7 $ 12,117.2 (a) Prior to July 1, 2022, Regeneron recorded net product sales of Libtayo in the United States and Sanofi recorded net product sales of Libtayo outside the United States. Effective July 1, 2022, the Company records global net product sales of Libtayo. See Note 3 for further details. (b) Rest of world ("ROW") (c) Net product sales of REGEN-COV in the United States relate to product sold in connection with the Company's agreements with the U.S. government. See Note 3 for further details. (d) Effective April 1, 2021, Kiniksa records net product sales of ARCALYST in the United States. Previously, the Company recorded net product sales of ARCALYST in the United States. Amounts recognized in the Company's Statements of Operations in connection with its collaborations with Sanofi are detailed below: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Antibody: Regeneron's share of profits in connection with commercialization of antibodies Collaboration revenue $ 3,136.5 $ 2,082.0 * $ 1,363.0 Sales-based milestones earned Collaboration revenue $ 50.0 $ 100.0 $ 50.0 Reimbursement for manufacturing of commercial supplies Collaboration revenue $ 613.0 $ 633.7 $ 488.8 Other Collaboration revenue $ — $ 28.7 $ — Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (83.7) $ 43.0 $ 129.2 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ 534.4 $ 437.4 $ 320.5 Immuno-oncology (a) : Regeneron's share of profits (losses) in connection with commercialization of Libtayo outside the United States Collaboration revenue $ — $ 6.7 $ (13.6) Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ — $ 4.6 $ 14.0 Reimbursement of R&D expenses Reduction of R&D expense $ — $ 42.7 $ 85.1 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ — $ 41.4 $ 89.6 Regeneron's obligation for its share of Sanofi commercial expenses SG&A expense $ — $ (19.9) $ (36.3) Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits Cost of goods sold $ — $ (70.1) $ (133.0) Amounts recognized in connection with up-front payments received Other operating income $ — $ 35.1 $ 6.1 * Net of one-time payment of $56.9 million to Sanofi in connection with the amendment to the Antibody License and Collaboration Agreement (a) As described within the " Immuno-Oncology " section below, effective July 1, 2022, the Company obtained the exclusive right to develop, commercialize, and manufacture Libtayo worldwide. Amounts recognized in the Company's Statements of Operations in connection with its Bayer collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Regeneron's share of profits in connection with commercialization of EYLEA outside the United States Collaboration revenue $ 1,376.4 $ 1,317.4 $ 1,349.2 Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ 111.1 $ 91.4 $ 60.1 One-time payment in connection with change in Japan arrangement Collaboration revenue $ — $ 21.9 $ — Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (44.0) $ 16.7 $ 5.2 Amounts recognized in the Company's Statements of Operations in connection with its Roche collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Global gross profit payment from Roche in connection with sales of REGEN-COV and Ronapreve Collaboration revenue $ 224.3 $ 627.3 $ 361.8 Other Collaboration revenue $ (13.3) $ — $ — Reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (1.5) $ 6.8 $ 128.1 Global gross profit payment to Roche in connection with sales of REGEN-COV and Ronapreve Cost of goods sold $ — $ — $ 259.6
Schedules of concentration of risk, by risk factor	Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows: Year Ended December 31, 2023 2022 2021 Besse Medical, a subsidiary of Cencora, Inc. 51 % 55 % 30 % McKesson Corporation 25 % 28 % 18 % U.S. government * * 43 % * Sales to the U.S. government 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. (In millions) Rebates, Chargebacks, Distribution- Other Sales- Total Balance as of December 31, 2020 $ 202.2 $ 77.2 $ 44.8 $ 324.2 Provisions 1,047.1 363.6 150.4 1,561.1 Credits/payments (1,034.7) (360.8) (127.6) (1,523.1) Balance as of December 31, 2021 214.6 80.0 67.6 362.2 Provisions 1,537.3 431.1 141.1 2,109.5 Credits/payments (1,398.0) (399.7) (127.2) (1,924.9) Balance as of December 31, 2022 353.9 111.4 81.5 546.8 Provisions 2,074.5 439.2 155.3 2,669.0 Credits/payments (1,972.7) (388.3) (157.5) (2,518.5) Balance as of December 31, 2023 $ 455.7 $ 162.3 $ 79.3 $ 697.3

Collaboration, License, and O_2

Collaboration, License, and Other Agreements (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Schedule of collaboration revenue	Net product sales consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 EYLEA ® HD U.S. $ 165.8 $ — $ — EYLEA ® U.S. 5,719.6 6,264.6 5,792.3 Total EYLEA HD and EYLEA U.S. 5,885.4 6,264.6 5,792.3 Libtayo ®(a) U.S. 538.8 374.5 306.3 Libtayo (a) ROW (b) 324.3 73.0 — Total Libtayo Global 863.1 447.5 306.3 Praluent ® U.S. 182.4 130.0 170.0 REGEN-COV ®(c) U.S. — — 5,828.0 Evkeeza ® U.S. 77.3 48.6 18.4 Inmazeb ® U.S. 69.8 3.0 — ARCALYST ®(d) U.S. — — 2.2 $ 7,078.0 $ 6,893.7 $ 12,117.2 (a) Prior to July 1, 2022, Regeneron recorded net product sales of Libtayo in the United States and Sanofi recorded net product sales of Libtayo outside the United States. Effective July 1, 2022, the Company records global net product sales of Libtayo. See Note 3 for further details. (b) Rest of world ("ROW") (c) Net product sales of REGEN-COV in the United States relate to product sold in connection with the Company's agreements with the U.S. government. See Note 3 for further details. (d) Effective April 1, 2021, Kiniksa records net product sales of ARCALYST in the United States. Previously, the Company recorded net product sales of ARCALYST in the United States. Amounts recognized in the Company's Statements of Operations in connection with its collaborations with Sanofi are detailed below: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Antibody: Regeneron's share of profits in connection with commercialization of antibodies Collaboration revenue $ 3,136.5 $ 2,082.0 * $ 1,363.0 Sales-based milestones earned Collaboration revenue $ 50.0 $ 100.0 $ 50.0 Reimbursement for manufacturing of commercial supplies Collaboration revenue $ 613.0 $ 633.7 $ 488.8 Other Collaboration revenue $ — $ 28.7 $ — Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (83.7) $ 43.0 $ 129.2 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ 534.4 $ 437.4 $ 320.5 Immuno-oncology (a) : Regeneron's share of profits (losses) in connection with commercialization of Libtayo outside the United States Collaboration revenue $ — $ 6.7 $ (13.6) Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ — $ 4.6 $ 14.0 Reimbursement of R&D expenses Reduction of R&D expense $ — $ 42.7 $ 85.1 Reimbursement of commercialization-related expenses Reduction of SG&A expense $ — $ 41.4 $ 89.6 Regeneron's obligation for its share of Sanofi commercial expenses SG&A expense $ — $ (19.9) $ (36.3) Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits Cost of goods sold $ — $ (70.1) $ (133.0) Amounts recognized in connection with up-front payments received Other operating income $ — $ 35.1 $ 6.1 * Net of one-time payment of $56.9 million to Sanofi in connection with the amendment to the Antibody License and Collaboration Agreement (a) As described within the " Immuno-Oncology " section below, effective July 1, 2022, the Company obtained the exclusive right to develop, commercialize, and manufacture Libtayo worldwide. Amounts recognized in the Company's Statements of Operations in connection with its Bayer collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Regeneron's share of profits in connection with commercialization of EYLEA outside the United States Collaboration revenue $ 1,376.4 $ 1,317.4 $ 1,349.2 Reimbursement for manufacturing of ex-U.S. commercial supplies Collaboration revenue $ 111.1 $ 91.4 $ 60.1 One-time payment in connection with change in Japan arrangement Collaboration revenue $ — $ 21.9 $ — Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (44.0) $ 16.7 $ 5.2 Amounts recognized in the Company's Statements of Operations in connection with its Roche collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Global gross profit payment from Roche in connection with sales of REGEN-COV and Ronapreve Collaboration revenue $ 224.3 $ 627.3 $ 361.8 Other Collaboration revenue $ (13.3) $ — $ — Reimbursement of R&D expenses (R&D expense)/Reduction of R&D expense $ (1.5) $ 6.8 $ 128.1 Global gross profit payment to Roche in connection with sales of REGEN-COV and Ronapreve Cost of goods sold $ — $ — $ 259.6
Schedule of accounts receivable and deferred revenue information	The following table summarizes contract balances in connection with the Company's Antibody Collaboration with Sanofi: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ 1,029.1 $ 692.3 Deferred revenue $ 427.7 $ 415.8 The following table summarizes contract balances in connection with the Company's Bayer collaboration: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ 381.7 $ 348.2 Deferred revenue $ 138.2 $ 131.9 The following table summarizes contract balances in connection with the Company's Alnylam collaboration: As of December 31, (In millions) 2023 2022 Accrued expenses and other current liabilities $ 22.6 $ 7.4 The following table summarizes contract balances in connection with the Company's Roche collaboration: As of December 31, (In millions) 2023 2022 Accounts receivable, net $ — $ 396.6 The following table summarizes the Company's contract balances in connection with this BARDA agreement: As of December 31, (In millions) 2023 Accounts receivable, net $ 18.5
Schedule of other operating costs and expense, by component	Amounts recognized in the Company's Statements of Operations in connection with its Alnylam collaboration are as follows: Statement of Operations Classification Year Ended December 31, (In millions) 2023 2022 2021 Regeneron's obligation for its share of Alnylam R&D expenses, net of reimbursement of R&D expenses (R&D expense) $ (74.1) $ (55.8) $ (60.5) Development milestone Acquired in-process research and development $ (100.0) $ — $ —
Schedule of recognized identified assets acquired and liabilities assumed	The following table summarizes the amounts recognized for assets acquired and liabilities assumed based on their estimated fair values as of the acquisition date: September 25, (In millions) 2023 Cash and cash equivalents $ 42.2 Marketable securities 12.1 Deferred tax assets, net 58.1 Indefinite-lived intangible asset related to in-process research and development 42.5 Goodwill 5.2 Other assets and liabilities, net (11.4) $ 148.7

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2023
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: (In millions) Amortized Unrealized Fair As of December 31, 2023 Cost Basis Gains Losses Value Corporate bonds $ 6,492.5 $ 10.4 $ (104.9) $ 6,398.0 U.S. government and government agency obligations 4,839.6 2.4 (8.6) 4,833.4 Sovereign bonds 58.1 — (0.9) 57.2 Commercial paper 636.8 0.2 (0.2) 636.8 Certificates of deposit 520.8 0.6 — 521.4 Asset-backed securities 88.2 0.1 (1.2) 87.1 $ 12,636.0 $ 13.7 $ (115.8) $ 12,533.9 As of December 31, 2022 Corporate bonds $ 6,975.5 $ — $ (291.1) $ 6,684.4 U.S. government and government agency obligations 2,945.4 0.9 (6.9) 2,939.4 Sovereign bonds 67.1 — (3.0) 64.1 Commercial paper 121.1 — — 121.1 Certificates of deposit 182.1 — (0.1) 182.0 Asset-backed securities 28.9 — (1.7) 27.2 $ 10,320.1 $ 0.9 $ (302.8) $ 10,018.2
Marketable securities, based on contractual maturity dates	The fair values of available-for-sale debt securities by contractual maturity consist of the following: As of December 31, (In millions) 2023 2022 Maturities within one year $ 8,114.8 $ 4,636.4 Maturities after one year through five years 4,414.5 5,381.4 Maturities after five years 4.6 0.4 $ 12,533.9 $ 10,018.2
Fair value and unrealized losses of marketable securities	The following table shows the fair value of the Company's available-for-sale debt securities that have unrealized losses, aggregated by investment category and length of time that the individual securities have been in a continuous loss position. Less than 12 Months 12 Months or Greater Total (In millions) As of December 31, 2023 Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 2,363.3 $ (2.4) $ 4,034.7 $ (102.5) $ 6,398.0 $ (104.9) U.S. government and government agency obligations 4,780.6 (6.0) 52.7 (2.6) 4,833.3 (8.6) Sovereign bonds 12.4 (0.1) 44.8 (0.8) 57.2 (0.9) Commercial paper 636.8 (0.2) — — 636.8 (0.2) Asset-backed securities 61.8 (0.3) 25.3 (0.9) 87.1 (1.2) $ 7,854.9 $ (9.0) $ 4,157.5 $ (106.8) $ 12,012.4 $ (115.8) As of December 31, 2022 Corporate bonds $ 2,445.4 $ (73.1) $ 4,200.4 $ (218.0) $ 6,645.8 $ (291.1) U.S. government and government agency obligations 785.2 (2.0) 71.0 (4.9) 856.2 (6.9) Sovereign bonds 18.6 (1.1) 45.6 (1.9) 64.2 (3.0) Certificates of deposit 40.2 (0.1) — — 40.2 (0.1) Asset-backed securities 11.5 (0.6) 15.2 (1.1) 26.7 (1.7) $ 3,300.9 $ (76.9) $ 4,332.2 $ (225.9) $ 7,633.1 $ (302.8)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Schedule of assets measured at fair value on a recurring basis	The table below summarizes the Company's assets and liabilities which are measured at fair value on a recurring basis. The following fair value hierarchy is used to classify assets and liabilities, based on inputs to valuation techniques utilized to measure fair value: • Level 1 - Quoted prices in active markets for identical assets or liabilities • 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 (In millions) Fair Value Measurements at Reporting Date As of December 31, 2023 Fair Value Level 1 Level 2 Level 3 Assets: Cash equivalents $ 928.1 $ 6.4 $ 921.7 $ — Available-for-sale debt securities: Corporate bonds 6,398.0 — 6,398.0 — U.S. government and government agency obligations 4,833.4 — 4,833.4 — Sovereign bonds 57.2 — 57.2 — Commercial paper 636.8 — 636.8 — Certificates of deposit 521.4 — 521.4 — Asset-backed securities 87.1 — 87.1 — Equity securities (unrestricted) 864.5 864.5 — — Equity securities (restricted) 112.9 112.9 — — Total assets $ 14,439.4 $ 983.8 $ 13,455.6 $ — Liabilities: Contingent consideration - CVRs $ 43.7 $ — $ — $ 43.7 As of December 31, 2022 Assets: Cash equivalents $ 1,662.8 $ 88.3 $ 1,574.5 $ — Available-for-sale debt securities: Corporate bonds 6,684.4 — 6,684.4 — U.S. government and government agency obligations 2,939.4 — 2,939.4 — Sovereign bonds 64.1 — 64.1 — Commercial paper 121.1 — 121.1 — Certificates of deposit 182.0 — 182.0 — Asset-backed securities 27.2 — 27.2 — Equity securities (unrestricted) 24.6 24.6 — — Equity securities (restricted) 1,185.4 1,185.4 — — Total assets $ 12,891.0 $ 1,298.3 $ 11,592.7 $ —

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Schedule of inventory	Inventories consist of the following: As of December 31, (In millions) 2023 2022 Raw materials $ 789.3 $ 818.4 Work-in-process 1,121.8 963.1 Finished goods 147.3 98.6 Deferred costs 522.1 521.8 $ 2,580.5 $ 2,401.9

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
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, net consists of the following: As of December 31, (In millions) 2023 2022 Building and improvements $ 2,423.1 $ 2,270.0 Leasehold improvements 133.9 114.3 Laboratory equipment 1,384.5 1,315.3 Computer equipment and software 389.7 337.4 Furniture, office equipment, and other 165.9 150.2 Land 283.1 264.5 Construction in progress 1,345.0 980.5 6,125.2 5,432.2 Accumulated depreciation and amortization (1,978.8) (1,669.2) $ 4,146.4 $ 3,763.0

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	Intangible assets. net consist of the following: As of December 31, 2023 2022 (In millions) Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross carrying Amount Accumulated Amortization Net Carrying Amount Acquired product rights - Libtayo 13 years $ 1,119.1 $ (126.7) $ 992.4 $ 946.3 $ (35.7) $ 910.6 Other intangibles 8 years 10.0 (6.3) 3.7 10.0 (5.1) 4.9 Acquired in-process research and development Indefinite 42.5 — 42.5 — — — $ 1,171.6 $ (133.0) $ 1,038.6 $ 956.3 $ (40.8) $ 915.5

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
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, (In millions) 2023 2022 Accrued payroll and related costs $ 618.2 $ 497.3 Accrued clinical expenses 292.2 295.0 Accrued sales-related costs 780.8 633.6 Other accrued expenses and liabilities 666.7 648.3 $ 2,357.9 $ 2,074.2

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Summary of issued senior unsecured notes	Long-term debt in connection with the Notes, net of underwriting discounts and offering expenses, consists of the following: As of December 31, (In millions) 2023 2022 1.750% Senior Notes due September 2030 $ 1,242.2 $ 1,241.0 2.800% Senior Notes due September 2050 740.7 740.4 $ 1,982.9 $ 1,981.4

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Schedule of amounts recognized in the condensed consolidated balance sheet	Amounts recognized in the Consolidated Balance Sheet related to the Company's leases are included in the table below. As of December 31, (In millions) Classification 2023 2022 Assets: Finance lease right-of-use assets Property, plant, and equipment, net (a) $ 605.7 $ 620.3 Operating lease right-of-use assets Other noncurrent assets (b) 78.0 71.2 $ 683.7 $ 691.5 Liabilities: Finance lease liabilities - noncurrent Finance lease liabilities $ 720.0 $ 720.0 Operating lease liabilities - current Accrued expenses and other current liabilities 19.0 12.4 Operating lease liabilities - noncurrent Other noncurrent liabilities 68.7 55.8 $ 807.7 $ 788.2 (a) Finance lease right-of-use assets were recorded net of accumulated amortization of $133.9 million and $119.4 million as of December 31, 2023 and 2022, respectively. (b) Operating lease right-of-use assets were recorded net of accumulated amortization of $44.6 million and $31.0 million as of December 31, 2023 and 2022, respectively.
Schedule of lease cost and other information	Lease costs consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 Operating lease costs $ 19.2 $ 12.4 $ 10.3 Finance lease costs: Amortization of finance lease right-of-use assets 14.5 14.5 14.4 Interest on finance lease liabilities 45.0 21.6 11.9 Total finance lease costs 59.5 36.1 26.3 Total lease costs $ 78.7 $ 48.5 $ 36.6 Other information related to the Company's leases includes the following: As of December 31, 2023 2022 Weighted-average remaining lease term (in years): Finance leases 3.2 4.2 Operating leases 7.4 7.2 Weighted-average discount rate: Finance leases 5.08% 4.84% Operating leases 5.38% 5.20% Supplemental cash flow information related to the Company's leases includes the following: Year Ended December 31, (In millions) 2023 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities (included within cash flows from operating activities) $ 22.5 $ 7.7 $ 10.2 Right-of-use assets obtained in exchange for operating lease liabilities $ 31.9 $ 35.1 $ 0.2
Schedule of maturities of operating lease liabilities	The following is a maturity analysis of the Company's lease liabilities as of December 31, 2023: (In millions) Finance Leases Operating Leases Total 2024 $ 44.8 $ 24.1 $ 68.9 2025 39.5 20.1 59.6 2026 30.9 15.6 46.5 2027 728.4 12.4 740.8 2028 — 11.0 11.0 Thereafter — 20.1 20.1 Total undiscounted lease payments 843.6 103.3 946.9 Imputed interest (123.6) (15.6) (139.2) Total lease liabilities $ 720.0 $ 87.7 $ 807.7
Schedule of maturities of finance lease liabilities	The following is a maturity analysis of the Company's lease liabilities as of December 31, 2023: (In millions) Finance Leases Operating Leases Total 2024 $ 44.8 $ 24.1 $ 68.9 2025 39.5 20.1 59.6 2026 30.9 15.6 46.5 2027 728.4 12.4 740.8 2028 — 11.0 11.0 Thereafter — 20.1 20.1 Total undiscounted lease payments 843.6 103.3 946.9 Imputed interest (123.6) (15.6) (139.2) Total lease liabilities $ 720.0 $ 87.7 $ 807.7

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Class of treasury stock	The table below summarizes the shares of the Company's Common Stock repurchased and the cost of the shares, which were recorded as Treasury Stock. Year Ended December 31, (In millions) 2023 2022 2021 Number of shares 2.9 3.3 3.0 Total cost of shares $ 2,214.6 $ 2,099.8 $ 1,655.0

Long-Term Incentive Plans (Tabl

Long-Term Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of transactions involving stock option awards	The table below summarizes the activity related to stock option awards under the Company's Incentive Plans during 2023. Number of Shares (In millions) Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term Intrinsic Value (In millions) Outstanding as of December 31, 2022 15.6 $ 481.62 2023: Granted 1.6 $ 835.91 Forfeited (0.2) $ 580.17 Exercised (2.8) $ 412.05 Outstanding as of December 31, 2023 14.2 $ 534.13 6.0 years $ 4,918.6 Vested and expected to vest as of December 31, 2023 13.8 $ 526.95 5.9 years $ 4,852.2 Exercisable as of December 31, 2023 9.6 $ 450.01 4.7 years $ 4,118.0
Schedule of weighted-average exercise prices and weighted-average grant-date fair values of options issued	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, 2023, 2022, and 2021. Number of Options Granted (In millions) Weighted-Average Exercise Price Weighted-Average Fair Value 2023: Exercise price equal to Market Price 1.6 $ 835.91 $ 264.37 2022: Exercise price equal to Market Price 2.0 $ 705.02 $ 220.88 2021: Exercise price equal to Market Price 2.3 $ 628.43 $ 174.20
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 2023, 2022, and 2021. 2023 2022 2021 Expected volatility 26 % 28 % 27 % Expected lives from grant date 5.1 years 5.2 years 5.5 years Expected dividend yield 0 % 0 % 0 % Risk-free interest rate 4.29 % 3.50 % 1.22 % The following table summarizes the weighted average values of the assumptions used in computing the fair value of PSUs that were granted during 2022. The Company did not grant PSUs during 2023 and 2021. 2022 Expected volatility 32% Expected dividend yield 0% Risk-free interest rate 3.3%
Schedule of activity related to restricted stock awards	A summary of the Company's activity related to restricted stock awards and time-based restricted stock units (excluding performance-based restricted stock units, which are detailed further below) (collectively, "restricted stock") during 2023 is summarized below. Number of Shares/Units (In millions) Weighted-Average Grant Unvested as of December 31, 2022 2.6 $ 571.19 2023: Granted 0.8 $ 838.11 Vested (1.0) $ 458.49 Forfeited (0.1) $ 585.23 Unvested as of December 31, 2023 2.3 $ 705.37
Schedule of activity related to performance-based awards	The table below summarizes activity related to PSUs during 2023. The number of unvested PSUs represents the maximum number of units that are eligible to be earned. Number of Shares/Units (In millions) Weighted-Average Grant Unvested as of December 31, 2022 1.5 $ 245.94 2023: Vested (0.1) $ 198.10 Unvested as of December 31, 2023 1.4 $ 247.91

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of income before income tax	Components of income before income taxes consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 United States $ (362.3) $ 839.9 $ 5,944.7 Foreign 4,561.6 4,018.9 3,381.1 $ 4,199.3 $ 4,858.8 $ 9,325.8
Schedule of components of income tax expense	Components of income tax expense consist of the following: Year Ended December 31, (In millions) 2023 2022 2021 Current: Federal $ 667.9 $ 968.5 $ 1,429.8 State 7.7 7.4 6.2 Foreign 407.9 290.9 (38.4) Total current tax expense 1,083.5 1,266.8 1,397.6 Deferred: Federal (834.5) (797.7) (423.2) State (6.5) (2.7) (0.6) Foreign 3.2 54.0 276.7 Total deferred tax benefit (837.8) (746.4) (147.1) $ 245.7 $ 520.4 $ 1,250.5
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, 2023 2022 2021 U.S. federal statutory tax rate 21.0 % 21.0 % 21.0 % Taxation of non-U.S. operations (6.6) (5.5) (2.8) Stock-based compensation (4.6) (2.9) (2.4) Income tax credits (3.2) (2.0) (1.0) Foreign-derived intangible income deduction (0.3) (1.0) (1.4) Other permanent differences (0.4) 1.1 — Effective income tax rate 5.9 % 10.7 % 13.4 %
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, (In millions) 2023 2022 Deferred tax assets: Capitalized research and development expenses $ 1,728.2 $ 845.3 Deferred compensation 413.6 416.2 Accrued expenses 214.1 235.6 Fixed assets and intangible assets 154.8 227.6 Tax attribute carryforwards 88.7 41.3 Other 26.4 15.9 Total deferred tax assets 2,625.8 1,781.9 Deferred tax liabilities: Unrealized gains on investments (50.4) (58.2) Net deferred tax assets $ 2,575.4 $ 1,723.7
Schedule of unrecognized tax benefits	The following table reconciles the beginning and ending amounts of unrecognized tax benefits: (In millions) 2023 2022 2021 Balance as of January 1 $ 542.8 $ 410.9 $ 267.0 Gross increases related to current year tax positions 153.4 136.9 182.3 Gross increases (decreases) related to prior year tax positions 3.2 (5.0) 2.9 Gross decreases due to settlements and lapse of statutes of limitations (3.0) — (41.3) Balance as of December 31 $ 696.4 $ 542.8 $ 410.9

Legal Matters (Tables)

Legal Matters (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of loss contingencies by contingency	Post-Grant Proceedings Before USPTO Company Patent(s) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status U.S. Patent Nos. 10,406,226 (the "'226 Patent") and 10,464,992 (the "'992 Patent") Anonymous parties Ex parte reexamination February 11, 2020 On September 11, 2023, the USPTO dismissed the '226 Patent reexamination proceedings following the Company's filing of a Notice of Disclaimer, disclaiming all claims of the '226 Patent. On September 8, 2023, the '992 Patent reexamination proceedings were stayed by the USPTO pending resolution of the inter partes review ("IPR") of the '992 Patent initiated by Celltrion, Inc., as discussed further below. On January 17, 2024, the Company filed a Notice of Disclaimer with the USPTO, disclaiming all claims of the '992 Patent. Company Patent(s) (continued) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status U.S. Patent Nos. 9,254,338 (the "'338 Patent") and 9,669,069 (the "'069 Patent") Mylan Pharmaceuticals Inc., joined by Apotex Inc. and Celltrion IPR petitions seeking declarations of invalidity May 5, 2021 On November 9, 2022, the USPTO issued final written decisions finding that the challenged claims of the '338 and '069 Patents are unpatentable and, therefore, invalid. On January 10, 2023, the Company filed notices of appeal of the USPTO written decisions concerning the '338 and '069 Patents with the Federal Circuit. U.S. Patent Nos. 10,130,681 (the "'681 Patent"), 10,888,601 (the "'601 Patent"), and 10,857,205 (the "'205 Patent") Mylan, joined by Celltrion ('601 and '681 Patents) and Samsung Bioepis Co., Ltd. ('601 Patent) IPR petitions seeking declarations of invalidity July 1, 2022 ('681 Patent and '601 Patent) October 28, 2022 ('205 Patent) On January 9, 2024, the USPTO issued final written decisions finding that that the challenged claims of the '681 and '601 Patents are unpatentable and, therefore, invalid. On March 1, 2023, the USPTO denied institution of Mylan's IPR petition against the '205 Patent following the Company's filing of a Notice of Disclaimer with the USPTO, disclaiming all claims of the '205 Patent. '681 Patent and '601 Patent Samsung Bioepis, joined by Biocon Biologics Inc. ('601 Patent) IPR petitions seeking declarations of invalidity January 6, 2023 ('681 Patent) March 26, 2023 ('601 Patent) On July 19, 2023 and October 20, 2023, the USPTO instituted IPR proceedings concerning the '681 Patent and the '601 Patent, respectively. U.S. Patent No. 11,253,572 (the "'572 Patent") Apotex IPR petition seeking declaration of invalidity September 9, 2022 On March 10, 2023, the USPTO declined to institute an IPR proceeding based on the Apotex IPR petition. Samsung Bioepis IPR petition seeking declaration of invalidity April 27, 2023 On November 17, 2023, the USPTO instituted IPR proceedings concerning the '572 Patent based on the Samsung IPR petition. '992 Patent and '226 Patent Celltrion, joined by Samsung Bioepis ('992 Patent) IPR petitions seeking declarations of invalidity January 17, 2023 ('992 Patent) February 28, 2023 ('226 Patent) On July 20, 2023, the USPTO instituted an IPR proceeding concerning the '992 Patent. On January 17, 2024, the Company filed a Notice of Disclaimer with the USPTO, disclaiming all claims of the '992 Patent. On September 1, 2023, the USPTO denied institution of Celltrion's IPR petition against the '226 Patent following the Company's filing of a Notice of Disclaimer with the USPTO, disclaiming all claims of the '226 Patent. Post-Grant Proceedings Authority/Court Company Patent(s) Challenger(s) Type of Challenge Date of Challenge Latest Events/Current Status EPO European Patent No. 2,944,306 (the "'306 Patent") Anonymous parties Opposition proceedings October 26 and October 27, 2021 Oral hearing to be scheduled. EPO European Patent No. 3,716,992 (the "EP '992 Patent") Amgen and three anonymous parties Opposition proceedings May 5-10, 2023 Oral hearing to be scheduled. German Federal Patent Court German designation of European Patent No. 2,364,691 (the "'691 Patent") Samsung Bioepis NL B.V. Invalidation proceedings June 22, 2023 Trial has been scheduled to begin in June 2025.

Net Income Per Share (Tables)

Net Income Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
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, (In millions, except per share data) 2023 2022 2021 Net income - basic and diluted $ 3,953.6 $ 4,338.4 $ 8,075.3 Weighted average shares - basic 106.7 107.1 105.7 Effect of dilutive securities: Stock options 4.9 4.9 5.4 Restricted stock awards and restricted stock units 2.1 1.5 1.1 Weighted average shares - diluted 113.7 113.5 112.2 Net income per share - basic $ 37.05 $ 40.51 $ 76.40 Net income per share - diluted $ 34.77 $ 38.22 $ 71.97
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) 2023 2022 2021 Stock options 1.8 2.3 2.9

Statement of Cash Flows (Tables

Statement of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2023
Cash and Cash Equivalents [Abstract]
Schedule of cash and cash equivalents	The following provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheet to the total of the same such amounts shown in the Consolidated Statement of Cash Flows: December 31, (In millions) 2023 2022 2021 Cash and cash equivalents $ 2,730.0 $ 3,105.9 $ 2,885.6 Restricted cash included in Other noncurrent assets 7.8 13.5 12.5 Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows $ 2,737.8 $ 3,119.4 $ 2,898.1
Schedule of restrictions on cash and cash equivalents	The following provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheet to the total of the same such amounts shown in the Consolidated Statement of Cash Flows: December 31, (In millions) 2023 2022 2021 Cash and cash equivalents $ 2,730.0 $ 3,105.9 $ 2,885.6 Restricted cash included in Other noncurrent assets 7.8 13.5 12.5 Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows $ 2,737.8 $ 3,119.4 $ 2,898.1
Summary of non-cash investing and financing activities	As of December 31, (In millions) 2023 2022 2021 Accrued capital expenditures $ 75.4 $ 70.8 $ 74.8 Accrued contingent consideration in connection with acquisitions $ 71.6 $ 135.5 $ —

Business Overview and Summary_4

Business Overview and Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) segment product	Dec. 31, 2022 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of products approved by the U.S. FDA | product	11
Number of business segments | segment	1
Provision for doubtful accounts	$ 0	$ 0
Allowance for doubtful accounts receivable, current	$ 0	$ 0
Two Individual Customers | Customer concentration risk | Accounts receivable
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage	83%	86%

Business Overview and Summary_5

Business Overview and Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives (Details)	Dec. 31, 2023
Building and improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	10 years
Building and improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	50 years
Laboratory equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Laboratory equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	10 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years

Product Sales - Schedule of Net

Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 13,117.2	$ 12,172.9	$ 16,071.7
Net product sales
Disaggregation of Revenue [Line Items]
Revenues	7,078	6,893.7	12,117.2
Libtayo
Disaggregation of Revenue [Line Items]
Revenues	863.1	447.5	306.3
United States | ELYEA HD And EYLEA
Disaggregation of Revenue [Line Items]
Revenues	5,885.4	6,264.6	5,792.3
United States | ELYEA HD
Disaggregation of Revenue [Line Items]
Revenues	165.8	0	0
United States | EYLEA
Disaggregation of Revenue [Line Items]
Revenues	5,719.6	6,264.6	5,792.3
United States | Libtayo
Disaggregation of Revenue [Line Items]
Revenues	538.8	374.5	306.3
United States | Praluent
Disaggregation of Revenue [Line Items]
Revenues	182.4	130	170
United States | REGEN-COV
Disaggregation of Revenue [Line Items]
Revenues	0	0	5,828
United States | Evkeeza
Disaggregation of Revenue [Line Items]
Revenues	77.3	48.6	18.4
United States | Inmazeb
Disaggregation of Revenue [Line Items]
Revenues	69.8	3	0
United States | ARCALYST
Disaggregation of Revenue [Line Items]
Revenues	0	0	2.2
Rest Of World | Libtayo
Disaggregation of Revenue [Line Items]
Revenues	$ 324.3	$ 73	$ 0

Product Sales - Narrative (Deta

Product Sales - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	$ 5,667.3	$ 5,328.7
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	$ 3,888	$ 3,586

Product Sales - Schedule of Con

Product Sales - Schedule of Concentration of Risk, by Risk Factor (Details) - Gross Product Revenue - Customer concentration risk	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Besse Medical, a subsidiary of Cencora, Inc.
Concentration Risk [Line Items]
Concentration risk, percentage	51%	55%	30%
McKesson Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	25%	28%	18%
U.S. government
Concentration Risk [Line Items]
Concentration risk, percentage			43%

Product Sales - Schedule of Sal

Product Sales - Schedule of Sales Related Deductions Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 546.8	$ 362.2	$ 324.2
Provisions	2,669	2,109.5	1,561.1
Credits/payments	(2,518.5)	(1,924.9)	(1,523.1)
Ending Balance	697.3	546.8	362.2
Rebates, Chargebacks, and Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	353.9	214.6	202.2
Provisions	2,074.5	1,537.3	1,047.1
Credits/payments	(1,972.7)	(1,398)	(1,034.7)
Ending Balance	455.7	353.9	214.6
Distribution- Related Fees
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	111.4	80	77.2
Provisions	439.2	431.1	363.6
Credits/payments	(388.3)	(399.7)	(360.8)
Ending Balance	162.3	111.4	80
Other Sales- Related Deductions
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	81.5	67.6	44.8
Provisions	155.3	141.1	150.4
Credits/payments	(157.5)	(127.2)	(127.6)
Ending Balance	$ 79.3	$ 81.5	$ 67.6

Collaboration, License, and O_3

Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 13,117.2	$ 12,172.9	$ 16,071.7
One-time payment		(56.9)
Sanofi Collaboration Agreement, Antibody | Collaboration revenue | Regeneron's share of profits in connection with commercialization of antibodies
Disaggregation of Revenue [Line Items]
Revenues	3,136.5	2,082	1,363
Sanofi Collaboration Agreement, Antibody | Collaboration revenue | Sales-based milestones earned
Disaggregation of Revenue [Line Items]
Revenues	50	100	50
Sanofi Collaboration Agreement, Antibody | Collaboration revenue | Reimbursement for manufacturing of commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	613	633.7	488.8
Sanofi Collaboration Agreement, Antibody | Collaboration revenue | Other
Disaggregation of Revenue [Line Items]
Revenues	0	28.7	0
Sanofi Collaboration Agreement, Antibody | (R&D expense)/Reduction of R&D expense | Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	(83.7)	43	129.2
Sanofi Collaboration Agreement, Antibody | SG&A expense | Reimbursement of commercialization-related expenses
Disaggregation of Revenue [Line Items]
Revenues	534.4	437.4	320.5
Sanofi Collaboration Agreement, Immuno-oncology | Collaboration revenue | Regeneron's share of profits in connection with commercialization of antibodies
Disaggregation of Revenue [Line Items]
Revenues	0	6.7	(13.6)
Sanofi Collaboration Agreement, Immuno-oncology | Collaboration revenue | Reimbursement for manufacturing of commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	0	4.6	14
Sanofi Collaboration Agreement, Immuno-oncology | (R&D expense)/Reduction of R&D expense | Reimbursement of R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	0	42.7	85.1
Sanofi Collaboration Agreement, Immuno-oncology | SG&A expense | Reimbursement of commercialization-related expenses
Disaggregation of Revenue [Line Items]
Revenues	0	41.4	89.6
Sanofi Collaboration Agreement, Immuno-oncology | SG&A expense | Regeneron's obligation for its share of Sanofi commercial expenses
Disaggregation of Revenue [Line Items]
Revenues	0	(19.9)	(36.3)
Sanofi Collaboration Agreement, Immuno-oncology | Cost of goods sold | Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits
Disaggregation of Revenue [Line Items]
Revenues	0	(70.1)	(133)
Sanofi Collaboration Agreement, Immuno-oncology | Other operating income | Amounts recognized in connection with up-front payments received
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 35.1	$ 6.1

Collaboration, License, and O_4

Collaboration, License, and Other Agreements - Sanofi, Antibody Narrative (Details) $ in Millions			12 Months Ended
	Jul. 01, 2022	Jun. 30, 2022	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) milestone	Dec. 31, 2021 USD ($)
Disaggregation of Revenue [Line Items]
Revenues			$ 13,117.2	$ 12,172.9	$ 16,071.7
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Percentage of quarterly profits require to be paid for reimbursement of development costs			10%
Percentage of share of profits used to reimburse collaborating party for trial costs	20%	10%
Contingent reimbursement obligation			$ 2,330
Starting share of profits outside the United States, based on sales, for collaborating party			65%
Starting share of profits outside the United States, based on sales, for company			35%
Ending share of profits outside the United States, based on sales, for collaborating party			55%
Ending share of profits outside the United States, based on sales, for company			45%
Number of sales-based milestones | milestone				2
Sanofi Collaboration Agreement, Antibody | Second Milestone
Disaggregation of Revenue [Line Items]
Revenues					50
Levels of twelve month sales at which sales milestone payments would be received					$ 1,500
Period for achieving sales target for milestone payment, rolling basis					12 months
Sanofi Collaboration Agreement, Antibody | Third Milestone
Disaggregation of Revenue [Line Items]
Revenues				$ 50
Levels of twelve month sales at which sales milestone payments would be received				$ 2,000
Period for achieving sales target for milestone payment, rolling basis				12 months
Sanofi Collaboration Agreement, Antibody | Sales Milestone Four
Disaggregation of Revenue [Line Items]
Revenues				$ 50
Levels of twelve month sales at which sales milestone payments would be received				$ 2,500
Period for achieving sales target for milestone payment, rolling basis				12 months
Sanofi Collaboration Agreement, Antibody | Sales Milestone Five
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, variable consideration amount			$ 50
Levels of twelve month sales at which sales milestone payments would be received			$ 3,000
Period for achieving sales target for milestone payment, rolling basis			12 months
Sanofi Collaboration Agreement, Antibody | Minimum
Disaggregation of Revenue [Line Items]
Percentage of trial costs required to be funded by collaborating party			80%
Percentage of quarterly profits require to be paid for reimbursement of development costs			30%
Sanofi Collaboration Agreement, Antibody | Maximum
Disaggregation of Revenue [Line Items]
Percentage of trial costs required to be funded by collaborating party			100%
Percentage of quarterly profits require to be paid for reimbursement of development costs			50%

Collaboration, License, and O_5

Collaboration, License, and Other Agreements - Schedule of Accounts Receivable and Deferred Revenue Information, Antibody Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 5,667.3	$ 5,328.7
Sanofi Collaboration Agreement, Antibody
Disaggregation of Revenue [Line Items]
Accounts receivable, net	1,029.1	692.3
Deferred revenue	$ 427.7	$ 415.8

Collaboration, License, and O_6

Collaboration, License, and Other Agreements - Sanofi, Immuno-Oncology Narrative (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
	Jul. 01, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2015
Disaggregation of Revenue [Line Items]
Up-front payment to be made to collaborator			$ 13,117.2	$ 12,172.9	$ 16,071.7
Sanofi
Disaggregation of Revenue [Line Items]
Up-front payment to collaborating party	$ 900	$ 900
Sanofi Collaboration Agreement, Immuno-oncology
Disaggregation of Revenue [Line Items]
Royalty payment to collaborating party, percentage of net product sales			11%
Sanofi Collaboration Agreement, Immuno-oncology | Sanofi | Sales-Based Milestones
Disaggregation of Revenue [Line Items]
Up-front payment to be made to collaborator		100
Sanofi Collaboration Agreement, Immuno-oncology | Sanofi | Regulatory Milestone
Disaggregation of Revenue [Line Items]
Up-front payment to collaborating party		100
Sanofi Collaboration Agreement, Immuno-oncology | Sanofi | Sales-Based Milestone One
Disaggregation of Revenue [Line Items]
Up-front payment to be made to collaborator		$ 65
Sanofi Collaboration Agreement, Immuno-oncology | Sanofi | Sales-Based Milestone Two
Disaggregation of Revenue [Line Items]
Up-front payment to be made to collaborator			$ 35
Sanofi Collaboration Agreement, Immuno-oncology | IO License and Collaboration Agreement
Disaggregation of Revenue [Line Items]
Up-front payment received						$ 375
Sanofi Collaboration Agreement, Immuno-oncology | Amended IO Discovery Agreement
Disaggregation of Revenue [Line Items]
Up-front payment received						$ 265
Sanofi Collaboration Agreement, Immuno-oncology | Amended IO Discovery Agreement | Other operating income
Disaggregation of Revenue [Line Items]
Cumulative catch-up adjustment to revenue, modification of contract					$ 66.9
Sanofi Collaboration Agreement, Amended and Restated Immuno-oncology License and Collaboration Agreement
Disaggregation of Revenue [Line Items]
Royalty payment to collaborating party, percentage of net product sales	0.50%
Other liabilities	$ 241
Remaining performance obligation	$ 35
Contingent reimbursement obligation			$ 28

Collaboration, License, and O_7

Collaboration, License, and Other Agreements - Bayer Narrative (Details) - Bayer - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Percentage of repayment of development balance out of profits	50%
Contingent reimbursement obligation	$ 293
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%

Collaboration, License, and O_8

Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 13,117.2	$ 12,172.9	$ 16,071.7
Bayer | Outside United States | Collaboration revenue | Regeneron's share of profits in connection with commercialization of EYLEA outside the United States
Disaggregation of Revenue [Line Items]
Revenues	1,376.4	1,317.4	1,349.2
Bayer | Outside United States | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	111.1	91.4	60.1
Bayer | Outside United States | Collaboration revenue | One-time payment in connection with change in Japan arrangement
Disaggregation of Revenue [Line Items]
Revenues	0	21.9	0
Bayer | Outside United States | (R&D expense)/Reduction of R&D expense | Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	$ (44)	$ 16.7	$ 5.2

Collaboration, License, and O_9

Collaboration, License, and Other Agreements - Schedule of Contract Balances, Bayer Collaborative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 5,667.3	$ 5,328.7
Bayer
Disaggregation of Revenue [Line Items]
Accounts receivable, net	381.7	348.2
Deferred revenue	$ 138.2	$ 131.9

Collaboration, License, and _10

Collaboration, License, and Other Agreements - Alnylam Narratives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 13,117.2	$ 12,172.9	$ 16,071.7
Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Upfront payment made				$ 400
Initial research term				5 years
Potential automatic extension of research term				7 years
Extension of research term fee				$ 300
Potential optional extension of research term				5 years
Collaborative arrangement additional payment eligible	100
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Clinical Proof-of-Principle Milestone | Alnylam
Disaggregation of Revenue [Line Items]
Revenues	$ 100
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Alnylam Pharmaceuticals, Inc. Stock Purchase Agreement
Disaggregation of Revenue [Line Items]
Cash consideration for Stock Purchase Agreement				$ 400

Collaboration, License, and _11

Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Alnylam (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (4,439)	$ (3,592.5)	$ (2,860.1)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | (R&D expense)/Reduction of R&D expense
Disaggregation of Revenue [Line Items]
Research and development expenses	(74.1)	(55.8)	(60.5)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Acquired in-process research and development
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (100)	$ 0	$ 0

Collaboration, License, and _12

Collaboration, License, and Other Agreements - Schedule of Contract Balances, Alnylam Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accrued expenses and other current liabilities	$ 2,357.9	$ 2,074.2
Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Accrued expenses and other current liabilities	$ 22.6	$ 7.4

Collaboration, License, and _13

Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Alnylam (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (4,439)	$ (3,592.5)	$ (2,860.1)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | (R&D expense)/Reduction of R&D expense
Disaggregation of Revenue [Line Items]
Research and development expenses	(74.1)	(55.8)	(60.5)
Alnylam Pharmaceuticals, Inc. Collaboration Agreement | Acquired in-process research and development
Disaggregation of Revenue [Line Items]
Research and development expenses	$ (100)	$ 0	$ 0

Collaboration, License, and _14

Collaboration, License, and Other Agreements - Schedule of Contract Balances, Alnylam Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accrued expenses and other current liabilities	$ 2,357.9	$ 2,074.2
Alnylam Pharmaceuticals, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Accrued expenses and other current liabilities	$ 22.6	$ 7.4

Collaboration, License, and _15

Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Roche (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues		$ 13,117.2	$ 12,172.9	$ 16,071.7
Roche Collaboration Agreement | Ronapreve | Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues		224.3	627.3	361.8
Roche Collaboration Agreement | Ronapreve | Cost of goods sold
Disaggregation of Revenue [Line Items]
Revenues		0	0	259.6
Roche Collaboration Agreement | Reimbursement of R&D expenses | (R&D expense)/Reduction of R&D expense
Disaggregation of Revenue [Line Items]
Revenues		(1.5)	6.8	128.1
Roche Collaboration Agreement | Other | Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues		$ (13.3)	$ 0	$ 0

Collaboration, License, and _16

Collaboration, License, and Other Agreements - Schedule of Contract Balances, Roche Collaboration (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 5,667.3	$ 5,328.7
Roche Collaboration Agreement
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 0	$ 396.6

Collaboration, License, and _17

Collaboration, License, and Other Agreements - Intellia Narrative (Details) - Intellia Collaboration Agreement - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2023	Dec. 31, 2023	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Acquired in-process research and development, up-front payment made			$ 70
Collaborative arrangement, extension period	2 years
Collaborative arrangement, extension payment		$ 30

Collaboration, License, and _18

Collaboration, License, and Other Agreements - Sonoma Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2023	Mar. 31, 2023	Dec. 31, 2023
Sonoma Biotherapeutics, Inc. Collaboration Agreement
Disaggregation of Revenue [Line Items]
Purchase of preferred stock	$ 30
Revenue			$ 45
Sonoma Biotherapeutics, Inc.
Disaggregation of Revenue [Line Items]
Up-front payment to collaborating party		$ 45

Collaboration, License, and _19

Collaboration, License, and Other Agreements - U.S. Government Narrative (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues		$ 13,117.2	$ 12,172.9	$ 16,071.7
Other Transaction Agreement
Disaggregation of Revenue [Line Items]
Percentage of trial costs required to be funded by collaborating party	70%
"Next Generation" Covid Antibodies | Other Transaction Agreement | Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues		50.4
U.S. government | "Next Generation" Covid Antibodies
Disaggregation of Revenue [Line Items]
Maximum transaction agreement payments		$ 326

Collaboration, License, and _20

Collaboration, License, and Other Agreements - Schedule of Contract Balances, U.S. Government (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 5,667.3	$ 5,328.7
Other Transaction Agreement
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 18.5

Collaboration, License, and _21

Collaboration, License, and Other Agreements - Decibel Narrative (Details) - Decibel Therapeutics, Inc. - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Sep. 30, 2023	Aug. 31, 2023
Disaggregation of Revenue [Line Items]
Payment to acquire business, cash paid	$ 101.3
Business combination, share price (in dollars per share)	$ 4
Business combination, payment for post-combination services	$ 6.6
Class of warrant or right, exercise price (in dollars per share)	$ 3.50
Business combination, fair value of CVRs	$ 43.7
Business combination, contingent consideration arrangements	$ 97
Business combination, fair value of equity interest		$ 10.3

Collaboration, License, and _22

Collaboration, License, and Other Agreements - Summary of Assets Acquired and Liabilities Assumed, Decibel (Details) - Decibel Therapeutics, Inc. $ in Millions	Sep. 25, 2023 USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 42.2
Marketable securities	12.1
Deferred tax assets, net	58.1
Indefinite-lived intangible asset related to in-process research and development	42.5
Goodwill	5.2
Other assets and liabilities, net	(11.4)
Total	$ 148.7

Collaboration, License, and _23

Collaboration, License, and Other Agreements - Checkmate Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Acquired in-process research and development in connection with asset acquisition	$ 0	$ 195	$ 0
Asset acquisition, cash and equivalents		26.4
Checkmate Pharmaceuticals, Inc.
Disaggregation of Revenue [Line Items]
Asset acquisition, consideration transferred		250
Acquired in-process research and development in connection with asset acquisition		195
Asset acquisition, assets acquired and liabilities assumed, net		$ 61.7

Collaboration, License, and _24

Collaboration, License, and Other Agreements - Other Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Agreements with Royalty Provisions
Disaggregation of Revenue [Line Items]
Royalty rate minimum	0.50%
Royalty rate maximum	12%
Royalty expense, net of reimbursements from collaborators	$ 117.6	$ 84.5	$ 66.9
Libtayo | Sanofi Collaboration Agreement, Immuno-oncology | Through December 31, 2023
Disaggregation of Revenue [Line Items]
Percentage of royalties to be paid				8%
Libtayo | Sanofi Collaboration Agreement, Immuno-oncology | January 1, 2024 Through December 31, 2026
Disaggregation of Revenue [Line Items]
Percentage of royalties to be paid				2.50%

Marketable Securities - Schedul

Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 12,636	$ 10,320.1
Unrealized Gains	13.7	0.9
Unrealized Losses	(115.8)	(302.8)
Fair Value	12,533.9	10,018.2
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	6,492.5	6,975.5
Unrealized Gains	10.4	0
Unrealized Losses	(104.9)	(291.1)
Fair Value	6,398	6,684.4
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	4,839.6	2,945.4
Unrealized Gains	2.4	0.9
Unrealized Losses	(8.6)	(6.9)
Fair Value	4,833.4	2,939.4
Sovereign bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	58.1	67.1
Unrealized Gains	0	0
Unrealized Losses	(0.9)	(3)
Fair Value	57.2	64.1
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	636.8	121.1
Unrealized Gains	0.2	0
Unrealized Losses	(0.2)	0
Fair Value	636.8	121.1
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	520.8	182.1
Unrealized Gains	0.6	0
Unrealized Losses	0	(0.1)
Fair Value	521.4	182
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	88.2	28.9
Unrealized Gains	0.1	0
Unrealized Losses	(1.2)	(1.7)
Fair Value	$ 87.1	$ 27.2

Marketable Securities - Sched_2

Marketable Securities - Schedule of Debt Securities Based on Contractual Maturity Dates (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Maturities within one year	$ 8,114.8	$ 4,636.4
Maturities after one year through five years	4,414.5	5,381.4
Maturities after five years	4.6	0.4
Total	$ 12,533.9	$ 10,018.2

Marketable Securities - Sched_3

Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 7,854.9	$ 3,300.9
Unrealized Loss - Less than 12 months	(9)	(76.9)
Fair Value - 12 Months or Greater	4,157.5	4,332.2
Unrealized Loss - 12 Months or Greater	(106.8)	(225.9)
Fair Value - Total	12,012.4	7,633.1
Unrealized Loss - Total	(115.8)	(302.8)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	2,363.3	2,445.4
Unrealized Loss - Less than 12 months	(2.4)	(73.1)
Fair Value - 12 Months or Greater	4,034.7	4,200.4
Unrealized Loss - 12 Months or Greater	(102.5)	(218)
Fair Value - Total	6,398	6,645.8
Unrealized Loss - Total	(104.9)	(291.1)
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	4,780.6	785.2
Unrealized Loss - Less than 12 months	(6)	(2)
Fair Value - 12 Months or Greater	52.7	71
Unrealized Loss - 12 Months or Greater	(2.6)	(4.9)
Fair Value - Total	4,833.3	856.2
Unrealized Loss - Total	(8.6)	(6.9)
Sovereign bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	12.4	18.6
Unrealized Loss - Less than 12 months	(0.1)	(1.1)
Fair Value - 12 Months or Greater	44.8	45.6
Unrealized Loss - 12 Months or Greater	(0.8)	(1.9)
Fair Value - Total	57.2	64.2
Unrealized Loss - Total	(0.9)	(3)
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	636.8
Unrealized Loss - Less than 12 months	(0.2)
Fair Value - 12 Months or Greater	0
Unrealized Loss - 12 Months or Greater	0
Fair Value - Total	636.8
Unrealized Loss - Total	(0.2)
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months		40.2
Unrealized Loss - Less than 12 months		(0.1)
Fair Value - 12 Months or Greater		0
Unrealized Loss - 12 Months or Greater		0
Fair Value - Total		40.2
Unrealized Loss - Total		(0.1)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	61.8	11.5
Unrealized Loss - Less than 12 months	(0.3)	(0.6)
Fair Value - 12 Months or Greater	25.3	15.2
Unrealized Loss - 12 Months or Greater	(0.9)	(1.1)
Fair Value - Total	87.1	26.7
Unrealized Loss - Total	$ (1.2)	$ (1.7)

Marketable Securities - Narrati

Marketable Securities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Interest income	$ 495.9	$ 160.1	$ 45.8

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Available-for-sale debt securities	$ 12,533.9	$ 10,018.2
Corporate bonds
Assets:
Available-for-sale debt securities	6,398	6,684.4
U.S. government and government agency obligations
Assets:
Available-for-sale debt securities	4,833.4	2,939.4
Sovereign bonds
Assets:
Available-for-sale debt securities	57.2	64.1
Commercial paper
Assets:
Available-for-sale debt securities	636.8	121.1
Certificates of deposit
Assets:
Available-for-sale debt securities	521.4	182
Asset-backed securities
Assets:
Available-for-sale debt securities	87.1	27.2
Measured on a recurring basis
Assets:
Cash equivalents	928.1	1,662.8
Total assets	14,439.4	12,891
Liabilities:
Contingent consideration - CVRs	43.7
Measured on a recurring basis | Unrestricted
Assets:
Equity securities	864.5	24.6
Measured on a recurring basis | Restricted
Assets:
Equity securities	112.9	1,185.4
Measured on a recurring basis | Corporate bonds
Assets:
Available-for-sale debt securities	6,398	6,684.4
Measured on a recurring basis | U.S. government and government agency obligations
Assets:
Available-for-sale debt securities	4,833.4	2,939.4
Measured on a recurring basis | Sovereign bonds
Assets:
Available-for-sale debt securities	57.2	64.1
Measured on a recurring basis | Commercial paper
Assets:
Available-for-sale debt securities	636.8	121.1
Measured on a recurring basis | Certificates of deposit
Assets:
Available-for-sale debt securities	521.4	182
Measured on a recurring basis | Asset-backed securities
Assets:
Available-for-sale debt securities	87.1	27.2
Measured on a recurring basis | Level 1
Assets:
Cash equivalents	6.4	88.3
Total assets	983.8	1,298.3
Liabilities:
Contingent consideration - CVRs	0
Measured on a recurring basis | Level 1 | Unrestricted
Assets:
Equity securities	864.5	24.6
Measured on a recurring basis | Level 1 | Restricted
Assets:
Equity securities	112.9	1,185.4
Measured on a recurring basis | Level 1 | Corporate bonds
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 1 | U.S. government and government agency obligations
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 1 | Sovereign bonds
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 1 | Commercial paper
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 1 | Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 1 | Asset-backed securities
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 2
Assets:
Cash equivalents	921.7	1,574.5
Total assets	13,455.6	11,592.7
Liabilities:
Contingent consideration - CVRs	0
Measured on a recurring basis | Level 2 | Unrestricted
Assets:
Equity securities	0	0
Measured on a recurring basis | Level 2 | Restricted
Assets:
Equity securities	0	0
Measured on a recurring basis | Level 2 | Corporate bonds
Assets:
Available-for-sale debt securities	6,398	6,684.4
Measured on a recurring basis | Level 2 | U.S. government and government agency obligations
Assets:
Available-for-sale debt securities	4,833.4	2,939.4
Measured on a recurring basis | Level 2 | Sovereign bonds
Assets:
Available-for-sale debt securities	57.2	64.1
Measured on a recurring basis | Level 2 | Commercial paper
Assets:
Available-for-sale debt securities	636.8	121.1
Measured on a recurring basis | Level 2 | Certificates of deposit
Assets:
Available-for-sale debt securities	521.4	182
Measured on a recurring basis | Level 2 | Asset-backed securities
Assets:
Available-for-sale debt securities	87.1	27.2
Measured on a recurring basis | Level 3
Assets:
Cash equivalents	0	0
Total assets	0	0
Liabilities:
Contingent consideration - CVRs	43.7
Measured on a recurring basis | Level 3 | Unrestricted
Assets:
Equity securities	0	0
Measured on a recurring basis | Level 3 | Restricted
Assets:
Equity securities	0	0
Measured on a recurring basis | Level 3 | Corporate bonds
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 3 | U.S. government and government agency obligations
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 3 | Sovereign bonds
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 3 | Commercial paper
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 3 | Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Measured on a recurring basis | Level 3 | Asset-backed securities
Assets:
Available-for-sale debt securities	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net unrealized gains (losses)	$ (237.8)	$ (39.8)	$ 386.1
Write-down in other income (expense)	29
Securities owned not readily marketable	74.3	48.3
Fair value adjustments of contingent consideration	0
Level 2 | Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 1,528	$ 1,443

Inventories - Schedule of Inven

Inventories - Schedule of Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 789.3	$ 818.4
Work-in-process	1,121.8	963.1
Finished goods	147.3	98.6
Deferred costs	522.1	521.8
Total Inventories	$ 2,580.5	$ 2,401.9

Inventories - Narrative (Detail

Inventories - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Inventory reserves	$ 705.9	$ 720.7
Inventory write-downs and reserves	$ 102.3	$ 258.7	$ 457.1

Property, Plant, and Equipmen_2

Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 6,125.2	$ 5,432.2
Accumulated depreciation and amortization	(1,978.8)	(1,669.2)
Property, plant, and equipment, net	4,146.4	3,763
Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	2,423.1	2,270
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	133.9	114.3
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	1,384.5	1,315.3
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	389.7	337.4
Furniture, office equipment, and other
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	165.9	150.2
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	283.1	264.5
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 1,345	$ 980.5

Property, Plant, and Equipmen_3

Property, Plant, and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 328.8	$ 303.9	$ 281.1
Property, plant, and equipment, net	4,146.4	3,763
United States
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	3,375	2,960
Rest Of World
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	$ 771.4	$ 803

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets, net	$ 1,038.6	$ 915.5
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	1,171.6	956.3
Accumulated Amortization	(133)	(40.8)
Acquired in-process research and development
Indefinite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 42.5	0
Acquired product rights - Libtayo
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	13 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 1,119.1	946.3
Accumulated Amortization	(126.7)	(35.7)
Net Carrying Amount	$ 992.4	910.6
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	8 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 10	10
Accumulated Amortization	(6.3)	(5.1)
Net Carrying Amount	$ 3.7	$ 4.9

Intangible Assets - Narrative (

Intangible Assets - Narrative (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
	Jul. 01, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense on intangible assets			$ 92.2	$ 37.6	$ 0
Finite-lived intangible asset, expected amortization, year one			85
Finite-lived intangible asset, expected amortization, year two			85
Finite-lived intangible asset, expected amortization, year three			85
Finite-lived intangible asset, expected amortization, year four			85
Finite-lived intangible asset, expected amortization, year five			$ 85
Sanofi Collaboration Agreement, Amended and Restated Immuno-oncology License and Collaboration Agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Other liabilities	$ 241
Sanofi
Acquired Finite-Lived Intangible Assets [Line Items]
Up-front payment to collaborating party	$ 900	$ 900

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued payroll and related costs	$ 618.2	$ 497.3
Accrued clinical expenses	292.2	295
Accrued sales-related costs	780.8	633.6
Other accrued expenses and liabilities	666.7	648.3
Accrued expenses and other current liabilities	$ 2,357.9	$ 2,074.2

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Line of credit | Senior unsecured revolving credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 750,000,000		$ 750,000,000
Line of credit facility, expiration period	5 years
Line of credit facility, increase limit	$ 500,000,000		500,000,000
Borrowings outstanding		$ 0
Line of credit | Letters of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000		50,000,000
Senior unsecured notes
Debt Instrument [Line Items]
Interest expense		$ 44,400,000	$ 44,400,000	$ 44,400,000
Redemption price, percentage		100%
Redemption price with change-in-control provision, percentage		101%
Senior unsecured notes | 1.750% Senior Notes due September 2030
Debt Instrument [Line Items]
Debt, principle amount					$ 1,250,000,000
Senior unsecured notes | 2.800% Senior Notes due September 2050
Debt Instrument [Line Items]
Debt, principle amount					$ 750,000,000

Debt - Summary of Issued Senior

Debt - Summary of Issued Senior Unsecured Notes (Details) - Senior unsecured notes - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt	$ 1,982.9	$ 1,981.4
1.750% Senior Notes due September 2030
Debt Instrument [Line Items]
Interest rate	1.75%
Long-term debt	$ 1,242.2	1,241
2.800% Senior Notes due September 2050
Debt Instrument [Line Items]
Interest rate	2.80%
Long-term debt	$ 740.7	$ 740.4

Leases - Leases Narrative (Deta

Leases - Leases Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Mar. 27, 2023	Mar. 31, 2017
Lessee, Lease, Description [Line Items]
Finance lease, liability	$ 720
Finance lease, renewal term		5 years
Laboratory and Office Facilities
Lessee, Lease, Description [Line Items]
Finance lease, liability			$ 720

Leases - Amounts recognized in

Leases - Amounts recognized in Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Finance lease right-of-use assets	$ 605.7	$ 620.3
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant, and equipment, net	Property, plant, and equipment, net
Operating lease right-of-use assets	$ 78	$ 71.2
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other noncurrent assets	Other noncurrent assets
Total lease assets	$ 683.7	$ 691.5
Liabilities:
Finance lease liabilities	720	720
Operating lease liabilities - current	$ 19	$ 12.4
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Operating lease liabilities - noncurrent	$ 68.7	$ 55.8
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other noncurrent liabilities	Other noncurrent liabilities
Total lease liability	$ 807.7	$ 788.2
Accumulated amortization of right-of-use assets	133.9	119.4
Operating lease, right-of-use asset, accumulated amortization	$ 44.6	$ 31

Leases - Finance lease costs (D

Leases - Finance lease costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease costs	$ 19.2	$ 12.4	$ 10.3
Amortization of finance lease right-of-use assets	14.5	14.5	14.4
Interest on finance lease liabilities	45	21.6	11.9
Total finance lease costs	59.5	36.1	26.3
Total lease cost	$ 78.7	$ 48.5	$ 36.6

Leases - Other information rela

Leases - Other information related to finance lease (Details)	Dec. 31, 2023	Dec. 31, 2022
Weighted-average remaining lease term (in years):
Finance leases	3 years 2 months 12 days	4 years 2 months 12 days
Operating leases	7 years 4 months 24 days	7 years 2 months 12 days
Weighted-average discount rate:
Finance leases	5.08%	4.84%
Operating leases	5.38%	5.20%

Leases - Supplemental cash flow

Leases - Supplemental cash flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities (included within cash flows from operating activities)	$ 22.5	$ 7.7	$ 10.2
Right-of-use assets obtained in exchange for operating lease liabilities	$ 31.9	$ 35.1	$ 0.2

Leases - Analysis of lease liab

Leases - Analysis of lease liability maturities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Finance Leases
2024	$ 44.8
2025	39.5
2026	30.9
2027	728.4
2028	0
Thereafter	0
Total undiscounted lease payments	843.6
Imputed interest	(123.6)
Total lease liabilities	720
Operating Leases
2024	24.1
2025	20.1
2026	15.6
2027	12.4
2028	11
Thereafter	20.1
Total undiscounted lease payments	103.3
Imputed interest	(15.6)
Total lease liabilities	87.7
Total
2024	68.9
2025	59.6
2026	46.5
2027	740.8
2028	11
2029	20.1
Total undiscounted lease payments	946.9
Imputed interest	(139.2)
Total lease liabilities	$ 807.7	$ 788.2

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details)	12 Months Ended		20 Months Ended
	Dec. 31, 2023 USD ($) vote $ / shares shares	Dec. 31, 2021 USD ($)	Jun. 30, 2023 USD ($)	Jan. 31, 2023 USD ($)	Dec. 31, 2022 $ / shares shares	Nov. 30, 2021 USD ($)	Jan. 31, 2021 USD ($)
Class of Stock [Line Items]
Preferred Stock, shares authorized (in shares) | shares	30,000,000				30,000,000
Remaining authorized repurchase amount	$ 1,531,000,000
January 2021 Share Repurchase Program
Class of Stock [Line Items]
Stock repurchase program, authorized amount							$ 1,500,000,000
November 2021 Share Repurchase Program
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 3,000,000,000
Cost of stock repurchased		$ 1,500,000,000	$ 3,000,000,000
Share Repurchase Program, January 2023
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 3,000,000,000
Class A Stock
Class of Stock [Line Items]
Common Stock, shares authorized (in shares) | shares	40,000,000				40,000,000
Common Stock, par value (in dollars per share) | $ / shares	$ 0.001				$ 0.001
Number of votes per share | vote	10
Common Stock
Class of Stock [Line Items]
Common Stock, shares authorized (in shares) | 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

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Repurchased Shares (Details) - Share Repurchase Programs - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity, Class of Treasury Stock [Line Items]
Number of shares (in shares)	2.9	3.3	3
Total cost of shares	$ 2,214.6	$ 2,099.8	$ 1,655

Long-Term Incentive Plans - Nar

Long-Term Incentive Plans - Narrative (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Maximum term of awards	10 years
Total intrinsic value - of stock options exercised	$ 1,096	$ 1,214	$ 1,707
Expected dividend yield	0%	0%	0%
Non-performance based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 357.1	$ 341.9	$ 328.7
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 589.6
Weighted average period for recognition of total unrecognized compensation expense (in years)	1 year 9 months 18 days
Restricted stock awards and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 475.9	331.1	221
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 1,023
Weighted average period for recognition of total unrecognized compensation expense (in years)	2 years 2 months 12 days
Performance-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 52	$ 52	$ 52
Unrecognized stock-based compensation cost, net of estimated forfeitures	$ 104.1
Weighted average period for recognition of total unrecognized compensation expense (in years)	2 years 3 months 18 days
Expected dividend yield		0%
Performance-based stock options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Performance-based stock options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	6 years
Amended & Restated Long-Term Incentive Plan 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	22.3
Number of shares available for future grants (in shares)	14.6

Long-Term Incentive Plans - Sum

Long-Term Incentive Plans - Summary of transactions involving stock option awards (Details) - Stock options - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Number of Shares (In millions)
Outstanding at beginning of period (in shares)	15.6
Granted (in shares)	1.6	2	2.3
Forfeited (in shares)	(0.2)
Exercised (in shares)	(2.8)
Outstanding at end of period (in shares)	14.2	15.6
Vested and expected to vest (in shares)	13.8
Exercisable (in shares)	9.6
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 481.62
Granted (in dollars per share)	835.91	$ 705.02	$ 628.43
Forfeited (in dollars per share)	580.17
Exercised (in dollars per share)	412.05
Outstanding at end of period (in dollars per share)	534.13	$ 481.62
Vested and expected to vest (in dollars per share)	526.95
Exercisable (in dollars per share)	$ 450.01
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years) - outstanding	6 years
Weighted average remaining contractual term - vested and expected to vest	5 years 10 months 24 days
Weighted average remaining contractual term - exercisable	4 years 8 months 12 days
Intrinsic value - outstanding	$ 4,918.6
Intrinsic value - vested and expected to vest	4,852.2
Intrinsic value - exercisable	$ 4,118

Long-Term Incentive Plans - S_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 shares in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options Granted (in shares)	1.6	2	2.3
Weighted-Average Exercise Price (in dollars per share)	$ 835.91	$ 705.02	$ 628.43
Weighted-Average Fair Value (in dollars per share)	$ 264.37	$ 220.88	$ 174.20

Long-Term Incentive Plans - S_3

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, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	26%	28%	27%
Expected lives from grant date	5 years 1 month 6 days	5 years 2 months 12 days	5 years 6 months
Expected dividend yield	0%	0%	0%
Risk-free interest rate	4.29%	3.50%	1.22%

Long-Term Incentive Plans - S_4

Long-Term Incentive Plans - Summary of activity related to restricted stock awards (Details) shares in Millions	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Weighted-Average Grant Date Fair Value
Vested (in dollars of shares)	$ 198.10
Restricted stock awards and restricted stock units
Number of Shares/Units (In millions)
Beginning balance (in shares) | shares	2.6
Granted (in shares) | shares	0.8
Vested (in shares) | shares	(1)
Forfeited (in shares) | shares	(0.1)
Ending balance (in shares) | shares	2.3
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars of shares)	$ 571.19
Granted (in dollars of shares)	838.11
Vested (in dollars of shares)	458.49
Forfeited (in dollars of shares)	585.23
Ending balance (in dollars of shares)	$ 705.37

Long-Term Incentive Plans - S_5

Long-Term Incentive Plans - Summary of activity related to performance-based awards (Details) shares in Millions	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Weighted-Average Grant Date Fair Value
Vested (in dollars of shares) | $ / shares	$ 198.10
Performance-based stock options
Number of Shares/Units (In millions)
Beginning balance (in shares) | shares	1.5
Vested (in shares) | shares	(0.1)
Ending balance (in shares) | shares	1.4
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars of shares) | $ / shares	$ 245.94
Ending balance (in dollars of shares) | $ / shares	$ 247.91

Long-Term Incentive Plans - S_6

Long-Term Incentive Plans - Summary of weighted-average values of assumptions used in computing fair value of performance-based options (Details) - Performance-based stock options	12 Months Ended
	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	32%
Expected dividend yield	0%
Risk-free interest rate	3.30%

Employee Savings Plans (Details

Employee Savings Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Employer contribution expense to 401(k) Savings Plan	$ 84.7	$ 67.6	$ 55.5

Income Taxes - Schedule of inco

Income Taxes - Schedule of income before income tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income before income taxes, United States	$ (362.3)	$ 839.9	$ 5,944.7
Income before income taxes, Foreign	4,561.6	4,018.9	3,381.1
Income before income taxes	$ 4,199.3	$ 4,858.8	$ 9,325.8

Income Taxes - Schedule of comp

Income Taxes - Schedule of components of income tax expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 667.9	$ 968.5	$ 1,429.8
State	7.7	7.4	6.2
Foreign	407.9	290.9	(38.4)
Total current tax expense	1,083.5	1,266.8	1,397.6
Deferred:
Federal	(834.5)	(797.7)	(423.2)
State	(6.5)	(2.7)	(0.6)
Foreign	3.2	54	276.7
Total deferred tax benefit	(837.8)	(746.4)	(147.1)
Total income tax expense (benefit)	$ 245.7	$ 520.4	$ 1,250.5

Income Taxes - Schedule of effe

Income Taxes - Schedule of effective income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	21%	21%	21%
Taxation of non-U.S. operations	(6.60%)	(5.50%)	(2.80%)
Stock-based compensation	(4.60%)	(2.90%)	(2.40%)
Income tax credits	(3.20%)	(2.00%)	(1.00%)
Foreign-derived intangible income deduction	(0.30%)	(1.00%)	(1.40%)
Other permanent differences	(0.40%)	1.10%	0%
Effective income tax rate	5.90%	10.70%	13.40%

Income Taxes - Schedule of defe

Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Capitalized research and development expenses	$ 1,728.2	$ 845.3
Deferred compensation	413.6	416.2
Accrued expenses	214.1	235.6
Fixed assets and intangible assets	154.8	227.6
Tax attribute carryforwards	88.7	41.3
Other	26.4	15.9
Total deferred tax assets	2,625.8	1,781.9
Deferred tax liabilities:
Unrealized gains on investments	(50.4)	(58.2)
Net deferred tax assets	$ 2,575.4	$ 1,723.7

Income Taxes - Schedule of unre

Income Taxes - Schedule of unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	$ 542.8	$ 410.9	$ 267
Gross increases related to current year tax positions	153.4	136.9	182.3
Gross decreases related to prior year tax positions		(5)
Gross increases related to prior year tax positions	3.2		2.9
Gross decreases due to settlements and lapse of statutes of limitations	(3)	0	(41.3)
Balance as of December 31	696.4	542.8	410.9
Unrecognized tax benefits that would impact effective tax rate	$ 442.5	$ 373.7	$ 321.1

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Unrecognized tax benefits that would impact effective tax rate	$ 442.5	$ 373.7	$ 321.1

Legal Matters (Details)

Legal Matters (Details)	Jul. 16, 2020 claim
'631 Patent
Loss Contingencies [Line Items]
Number of IPR filed	2

Net Income Per Share - Schedule

Net Income Per Share - Schedule of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income - basic and diluted	$ 3,953.6	$ 4,338.4	$ 8,075.3
Weighted average shares outstanding - basic (in shares)	106.7	107.1	105.7
Effect of dilutive securities:
Weighted average shares - diluted (in shares)	113.7	113.5	112.2
Net income per share - basic (in dollars per share)	$ 37.05	$ 40.51	$ 76.40
Net income per share - diluted (in dollars per share)	$ 34.77	$ 38.22	$ 71.97
Stock options
Effect of dilutive securities:
Effect of dilutive securities (in shares)	4.9	4.9	5.4
Restricted stock awards and restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (in shares)	2.1	1.5	1.1

Net Income Per Share - Schedu_2

Net Income Per Share - Schedule of Antidilutive Securities Excluded From Computation (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares (in shares)	1.8	2.3	2.9

Statement of Cash Flows - Sched

Statement of Cash Flows - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 2,730	$ 3,105.9	$ 2,885.6
Restricted cash included in Other noncurrent assets	7.8	13.5	12.5
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows	$ 2,737.8	$ 3,119.4	$ 2,898.1	$ 2,207.3

Statement of Cash Flows - Summa

Statement of Cash Flows - Summary of Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Accrued capital expenditures	$ 75.4	$ 70.8	$ 74.8
Accrued contingent consideration in connection with acquisitions	$ 71.6	$ 135.5	$ 0