Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Bayer (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 13,117.2	$ 12,172.9	$ 16,071.7
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	1,376.4	1,317.4	1,349.2
Bayer | Outside United States | Collaboration revenue | Reimbursement for manufacturing of ex-U.S. commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	111.1	91.4	60.1
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	0.0
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	$ (44.0)	$ 16.7	$ 5.2