v3.25.4
Derivatives - Other derivative contracts (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Derivatives    
Net gains (losses) on investments $ 3,151.4 $ 1,067.2
Forward contracts to buy long-dated U.S. treasury bonds    
Derivatives    
Notional amount 0.0 1,330.2
Forward contracts to sell long-dated U.S. treasury bonds    
Derivatives    
Notional amount 246.6 0.0
Interest rate swap contracts    
Derivatives    
Notional amount $ 0.0 $ 1,900.0