Collaboration, License, and Other Agreements - Schedule of Collaboration Revenue Earned From Sanofi (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 12,172.9	$ 16,071.7	$ 8,497.1
Sanofi Collaboration Agreement, Antibody | Other collaboration revenue | Regeneron's share of profits in connection with commercialization of antibodies
Disaggregation of Revenue [Line Items]
Revenues	2,082.0	1,363.0	785.2
Sanofi Collaboration Agreement, Antibody | Other collaboration revenue | Sales-based milestones earned
Disaggregation of Revenue [Line Items]
Revenues	100.0	50.0	50.0
Sanofi Collaboration Agreement, Antibody | Other collaboration revenue | Reimbursement for manufacturing of commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	633.7	488.8	368.0
Sanofi Collaboration Agreement, Antibody | Other collaboration revenue | Other
Disaggregation of Revenue [Line Items]
Revenues	28.7	0.0	0.0
Sanofi Collaboration Agreement, Antibody | Reduction of R&D expense | Reimbursements of R&D expenses, net of Regeneron's obligation for its share of Sanofi R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	43.0	129.2	149.1
Sanofi Collaboration Agreement, Antibody | SG&A expense | Reimbursement of commercialization-related expenses
Disaggregation of Revenue [Line Items]
Revenues	437.4	320.5	359.4
Sanofi Collaboration Agreement, Immuno-oncology | Other collaboration revenue | Regeneron's share of profits in connection with commercialization of antibodies
Disaggregation of Revenue [Line Items]
Revenues	6.7	(13.6)	(25.7)
Sanofi Collaboration Agreement, Immuno-oncology | Other collaboration revenue | Reimbursement for manufacturing of commercial supplies
Disaggregation of Revenue [Line Items]
Revenues	4.6	14.0	8.9
Sanofi Collaboration Agreement, Immuno-oncology | Reduction of R&D expense | Reimbursement of R&D expenses
Disaggregation of Revenue [Line Items]
Revenues	42.7	85.1	166.2
Sanofi Collaboration Agreement, Immuno-oncology | SG&A expense | Reimbursement of commercialization-related expenses
Disaggregation of Revenue [Line Items]
Revenues	41.4	89.6	64.7
Sanofi Collaboration Agreement, Immuno-oncology | SG&A expense | Regeneron's obligation for its share of Sanofi commercial expenses
Disaggregation of Revenue [Line Items]
Revenues	(19.9)	(36.3)	(22.4)
Sanofi Collaboration Agreement, Immuno-oncology | Cost of goods sold | Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits
Disaggregation of Revenue [Line Items]
Revenues	(70.1)	(133.0)	(119.1)
Sanofi Collaboration Agreement, Immuno-oncology | Other operating income | Amounts recognized in connection with up-front payments received
Disaggregation of Revenue [Line Items]
Revenues	$ 35.1	$ 6.1	$ 210.6