v3.25.4
Financial Risk Management - Market Risk - Foreign currency effects on the consolidated statement of earnings (Details)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Sep. 11, 2025
USD ($)
Sep. 11, 2025
CAD ($)
Financial Risk Management        
Borrowings, Principal $ 13,743.3 $ 11,874.1    
Non-insurance companies        
Financial Risk Management        
Borrowings, Principal 3,213.1 2,918.8    
Non-insurance companies | Peak Achievement credit facilities and loans        
Financial Risk Management        
Borrowings, Principal     $ 198.7 $ 275.0
Canada, Dollars        
Financial Risk Management        
Assets 4,838.1 3,366.5    
Liabilities (1,812.6) (792.3)    
Net asset (liability) exposure 3,025.5 2,574.2    
Notional long (short) amount of foreign currency forward contracts (3,480.4) (2,734.6)    
Net asset (liability) exposure after foreign currency forward contracts (454.9) (160.4)    
Hypothetical change in pre-tax earnings (loss) 45.5 16.0    
Hypothetical change in net earnings (loss) 40.8 17.0    
Euro        
Financial Risk Management        
Assets 1,694.3 1,186.9    
Liabilities (1,659.4) (1,489.0)    
Net asset (liability) exposure 34.9 (302.1)    
Notional long (short) amount of foreign currency forward contracts (3,875.8) (847.7)    
Net asset (liability) exposure after foreign currency forward contracts (3,840.9) (1,149.8)    
Hypothetical change in pre-tax earnings (loss) 384.1 115.0    
Hypothetical change in net earnings (loss) 298.1 93.8    
United Kingdom, Pounds        
Financial Risk Management        
Assets 1,861.7 1,512.9    
Liabilities (2,260.4) (2,022.6)    
Net asset (liability) exposure (398.7) (509.7)    
Notional long (short) amount of foreign currency forward contracts (101.4) (99.6)    
Net asset (liability) exposure after foreign currency forward contracts (500.1) (609.3)    
Hypothetical change in pre-tax earnings (loss) 50.0 60.9    
Hypothetical change in net earnings (loss) 39.8 48.5    
India, Rupees        
Financial Risk Management        
Assets 1,638.4 2,292.0    
Liabilities (217.8) (284.9)    
Net asset (liability) exposure 1,420.6 2,007.1    
Notional long (short) amount of foreign currency forward contracts 3.4 3.8    
Net asset (liability) exposure after foreign currency forward contracts 1,424.0 2,010.9    
Hypothetical change in pre-tax earnings (loss) (142.4) (201.1)    
Hypothetical change in net earnings (loss) $ (119.9) $ (189.7)    
Foreign currency risk        
Financial Risk Management        
Sensitivity analysis, percentage of appreciation the U.S. dollar against foreign currency 10.00%