Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Bayer (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues	$ 3,145.0	$ 3,162.1
Bayer | Rest Of World | Collaboration revenue | Regeneron's share of profits in connection with commercialization of EYLEA 8 mg and EYLEA outside the United States
Disaggregation of Revenue [Line Items]
Revenues	333.9	331.6
Bayer | Rest Of World | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	22.1	25.3
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	$ (8.7)	$ (13.4)