Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Bayer (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenues	$ 3,675.6	$ 3,547.1	$ 6,704.3	$ 6,692.1
Bayer \| Rest Of World \| Collaboration revenue \| Regeneron's share of profits
Disaggregation of Revenue [Line Items]
Revenues	383.4	353.0	700.7	686.9
Bayer \| Rest Of World \| Collaboration revenue \| Reimbursement for manufacturing of commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	31.6	22.1	58.2	44.2
Bayer \| Rest Of World \| 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	$ (5.6)	$ (14.7)	$ (15.0)	$ (23.4)

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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+ Details

- 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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+ Details