v3.25.4
Financial Risk Management - Market Risk - Foreign currency risk (Details)
€ in Millions, $ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2025
CAD ($)
Dec. 31, 2025
EUR (€)
Aug. 14, 2025
CAD ($)
Dec. 31, 2024
CAD ($)
Dec. 31, 2024
EUR (€)
Hedges of net investment in Canadian subsidiaries | 4.45% due August 14, 2035 (Cdn$400.0)              
Financial Risk Management.              
Debt hedges         $ 400.0    
Hedges of net investment in Canadian subsidiaries | 5.10% due August 16, 2055 (Cdn$300.0)              
Financial Risk Management.              
Debt hedges         $ 300.0    
Foreign currency risk              
Net gains (losses) on investments:              
Investing activities $ (69.0) $ (350.4)          
Underwriting activities (128.1) 91.1          
Foreign currency contracts (242.6) 234.1          
Foreign currency net losses (439.7) (25.2)          
Foreign currency risk | Hedges of net investment in Canadian subsidiaries | Unsecured senior notes              
Financial Risk Management.              
Debt hedges     $ 3,840.0     $ 3,140.0  
Debt hedges at fair value 2,829.4 2,207.0          
Gains (losses) on hedge of net investment in Canadian subsidiaries (110.1) 173.9          
Foreign currency risk | Hedges of net investment in European operations | Unsecured senior notes              
Financial Risk Management.              
Debt hedges | €       € 750.0     € 750.0
Debt hedges at fair value 874.3 767.5          
Gains (losses) on hedge of net investment in Canadian subsidiaries $ (103.6) $ 51.5