Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Bayer (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 3,605.4	$ 3,028.7
Bayer \| Rest Of World \| Regeneron's share of profits \| Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues	240.0	317.3
Bayer \| Rest Of World \| Reimbursement for manufacturing of commercial supplies \| Collaboration revenue
Disaggregation of Revenue [Line Items]
Revenues	47.3	26.6
Bayer \| Rest Of World \| Reimbursement of R&D expenses, net of Regeneron's obligation for its share of Bayer R&D expenses \| Reduction of R&D expense/(R&D expense)
Disaggregation of Revenue [Line Items]
Revenues	$ 1.0	$ (9.4)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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