Collaboration, License, and Other Agreements - Amounts Recognized in Statement of Operations with Bayer (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 3,162.1	$ 2,965.1
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	331.6	338.4
Bayer | Outside United States | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	25.3	25.0
Bayer | Outside United States | Collaboration revenue | One-time payment in connection with change in Japan arrangement
Disaggregation of Revenue [Line Items]
Revenues	0.0	21.9
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	$ (13.4)	$ 0.3