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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 3,158.1	$ 2,857.2	$ 6,320.2	$ 5,822.3
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	349.5	339.7	681.1	678.1
Bayer | Outside United States | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	27.2	17.8	52.5	42.8
Bayer | Outside United States | Collaboration revenue | One-time payment in connection with change in Japan arrangement
Disaggregation of Revenue [Line Items]
Revenues	0.0	0.0	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	$ (12.0)	$ 2.9	$ (25.4)	$ 3.2