v3.26.1
Indebtedness - Narrative (Details) - USD ($)
$ in Millions
1 Months Ended 6 Months Ended
May 14, 2026
Aug. 31, 2024
Jun. 30, 2026
May 31, 2026
Dec. 31, 2025
May 12, 2025
Sep. 15, 2015
Revolving Credit Facility              
Debt Instrument [Line Items]              
Maximum borrowing capacity   $ 1,500.0          
Debt instrument, term   5 years          
Long-Term Line of Credit     $ 0.0   $ 0.0    
2026 Term Loan two-year tranche              
Debt Instrument [Line Items]              
Debt instrument, face amount     1,800.0 $ 2,000.0      
Proceeds from issuance of debt $ 2,000.0            
Floating Rate 364-Day Tranche              
Debt Instrument [Line Items]              
Debt instrument, face amount     800.0        
Proceeds from issuance of debt 1,000.0            
Floating Rate Two-Year Tranche              
Debt Instrument [Line Items]              
Debt instrument, face amount     $ 1,000.0        
Proceeds from issuance of debt 1,000.0            
5.050% Senior Notes due January 15, 2031              
Debt Instrument [Line Items]              
Debt instrument, interest rate, stated percentage     5.05%        
5.750% Senior Notes due May 15, 2035              
Debt Instrument [Line Items]              
Debt instrument, interest rate, stated percentage     5.75%        
6.450% Senior Notes due May 15, 2055              
Debt Instrument [Line Items]              
Debt instrument, interest rate, stated percentage     6.45%        
Deferred tax liability              
Debt Instrument [Line Items]              
Debt instrument, face amount           $ 1,750.0  
Deferred tax liability | Apellis Pharmaceuticals, Inc.              
Debt Instrument [Line Items]              
Debt instrument, face amount           395.2  
Deferred tax liability | 5.050% Senior Notes due January 15, 2031              
Debt Instrument [Line Items]              
Debt instrument, face amount           $ 400.0  
Debt instrument, interest rate, stated percentage           5.05%  
Percentage par value of senior notes           99.981%  
Deferred tax liability | 5.750% Senior Notes due May 15, 2035              
Debt Instrument [Line Items]              
Debt instrument, face amount           $ 650.0  
Debt instrument, interest rate, stated percentage           5.75%  
Percentage par value of senior notes           99.924%  
Deferred tax liability | 6.450% Senior Notes due May 15, 2055              
Debt Instrument [Line Items]              
Debt instrument, face amount           $ 700.0  
Debt instrument, interest rate, stated percentage           6.45%  
Percentage par value of senior notes           99.657%  
Deferred tax liability | 2025 Senior Notes              
Debt Instrument [Line Items]              
Debt instrument, redemption price, percentage     100.00%        
Debt instrument, make whole provision redemption price, percentage     101.00%        
Payments of financing costs     $ 13.9        
Deferred tax liability | 4.050% Senior Notes due 2025              
Debt Instrument [Line Items]              
Debt instrument, face amount             $ 1,750.0
Debt instrument, interest rate, stated percentage     4.05%        
Debt instrument, redemption price, percentage     99.764%        
Line of Credit | Secured Debt | Apellis Pharmaceuticals, Inc.              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 400.0