v3.26.1
Collaboration, License, and Other Agreements - Amounts Recognized In Statement of Operations with Sanofi (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disaggregation of Revenue [Line Items]    
Revenues $ 3,605.4 $ 3,028.7
Sanofi Collaboration Agreement, Antibody | Regeneron's share of profits | Collaboration revenue    
Disaggregation of Revenue [Line Items]    
Revenues 1,450.8 1,018.2
Sanofi Collaboration Agreement, Antibody | Reimbursement for manufacturing of commercial supplies | Collaboration revenue    
Disaggregation of Revenue [Line Items]    
Revenues 154.3 165.0
Sanofi Collaboration Agreement, Antibody | Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses | (R&D expense)    
Disaggregation of Revenue [Line Items]    
Revenues (16.7) (15.5)
Sanofi Collaboration Agreement, Antibody | Reimbursement of commercialization-related expenses | Reduction of SG&A expense    
Disaggregation of Revenue [Line Items]    
Revenues $ 184.1 $ 159.2