v3.25.1
Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale    
Fixed Maturity Securities $ 35,751.4 $ 35,629.9
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 796.1  
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax $ 2,901.1  
Fixed maturity securities in unrealized loss position percent of total 100.00%  
External Credit Rating, Investment Grade    
Debt Securities, Available-for-sale    
Fixed Maturity Securities $ 34,297.5  
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 781.7  
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax $ 2,833.3  
Fixed maturity securities in unrealized loss position percent of total 97.70%  
External Credit Rating, Below-Investment-Grade    
Debt Securities, Available-for-sale    
Fixed Maturity Securities $ 1,453.9  
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 14.4  
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax $ 67.8  
Fixed maturity securities in unrealized loss position percent of total 2.30%