Collaboration Agreements - Amounts Recognized in Statement of Operations with Bayer (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 2,936.2	$ 3,452.8	$ 8,758.5	$ 11,120.0
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	315.3	351.0	993.4	995.3
Bayer | Outside United States | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	17.5	14.0	60.3	41.6
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	21.9	0.0
Bayer | Outside United States | (R&D expense)/reduction of R&D expense | Reimbursement of R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	11.8	14.5	32.7	35.2
Bayer | Outside United States | (R&D expense)/reduction of R&D expense | Regeneron's obligation for its share of Bayer research and development expenses
Disaggregation of Revenue [Line Items]
Revenues	$ (4.7)	$ (8.0)	$ (22.4)	$ (31.4)