v3.26.1
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, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Revenues $ 4,290.7 $ 3,675.6 $ 7,896.1 $ 6,704.3
Bayer | Rest Of World | Regeneron's share of profits | Income Statement Location [Axis]: us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax        
Disaggregation of Revenue [Line Items]        
Revenues 227.3 383.4 467.3 700.7
Bayer | Rest Of World | Reimbursement for manufacturing of commercial supplies | Income Statement Location [Axis]: us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax        
Disaggregation of Revenue [Line Items]        
Revenues 48.9 31.6 96.2 58.2
Bayer | Rest Of World | Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of R&D expenses | Income Statement Location [Axis]: us-gaap:ResearchAndDevelopmentExpense        
Disaggregation of Revenue [Line Items]        
Revenues $ (0.6) $ (5.6) $ 0.4 $ (15.0)