v3.25.2
Investments - Fair Value and Gross Unrealized Losses (Details)
$ in Millions
Jun. 30, 2025
USD ($)
Jun. 30, 2025
security
Jun. 30, 2025
Jun. 30, 2025
position
Dec. 31, 2024
USD ($)
Dec. 31, 2024
security
Dec. 31, 2024
Dec. 31, 2024
position
Fixed maturity securities, Gross Unrealized Losses                
Number of positions with a gross unrealized loss, 12 Months or Less (security) | security   511       665    
Number of positions with a gross unrealized loss, more than 12 months (security)   1,783   1,783   1,862   1,862
Number of positions with a gross unrealized loss, Total (security) | security   2,294       2,527    
Fair value as a percentage of total fixed maturities and equity securities fair value, 12 Months or Less (percent)     12.10%       15.80%  
Fair value as a percentage of total fixed maturities and equity securities fair value, more than 12 months (percent)     49.10%       51.10%  
Fair value as a percentage of total fixed maturities and equity securities fair value, Total (percent)     61.20%       66.90%  
Fixed maturity securities                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less $ 659.3       $ 849.1      
Fixed maturity securities, Fair Value, More than 12 Months 2,676.3       2,751.7      
Fixed maturity securities, Fair Value, Total 3,335.6       3,600.8      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 23.1       19.2      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 431.4       483.8      
Fixed maturity securities, Gross Unrealized Losses, Total 454.5       503.0      
Mortgage-backed securities                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 61.8       208.3      
Fixed maturity securities, Fair Value, More than 12 Months 249.4       419.3      
Fixed maturity securities, Fair Value, Total 311.2       627.6      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 1.0       3.1      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 42.5       71.7      
Fixed maturity securities, Gross Unrealized Losses, Total 43.5       74.8      
Other                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 19.8       77.1      
Fixed maturity securities, Fair Value, More than 12 Months 280.4       274.6      
Fixed maturity securities, Fair Value, Total 300.2       351.7      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 0.2       1.5      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 61.3       67.6      
Fixed maturity securities, Gross Unrealized Losses, Total 61.5       69.1      
Municipal bonds                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 255.9       193.5      
Fixed maturity securities, Fair Value, More than 12 Months 625.4       632.0      
Fixed maturity securities, Fair Value, Total 881.3       825.5      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 9.0       3.4      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 96.6       102.4      
Fixed maturity securities, Gross Unrealized Losses, Total 105.6       105.8      
Foreign government bonds                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 1.0       1.5      
Fixed maturity securities, Fair Value, More than 12 Months 11.9       11.7      
Fixed maturity securities, Fair Value, Total 12.9       13.2      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 0.0       0.0      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 0.8       0.9      
Fixed maturity securities, Gross Unrealized Losses, Total 0.8       0.9      
Corporate bonds                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 131.9       235.4      
Fixed maturity securities, Fair Value, More than 12 Months 1,064.1       1,075.8      
Fixed maturity securities, Fair Value, Total 1,196.0       1,311.2      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 11.7       10.3      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 196.8       219.8      
Fixed maturity securities, Gross Unrealized Losses, Total 208.5       230.1      
Other asset-backed securities                
Fixed maturity securities, Fair Value                
Fixed maturity securities, Fair Value, 12 Months or Less 188.9       133.3      
Fixed maturity securities, Fair Value, More than 12 Months 445.1       338.3      
Fixed maturity securities, Fair Value, Total 634.0       471.6      
Fixed maturity securities, Gross Unrealized Losses                
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less 1.2       0.9      
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months 33.4       21.4      
Fixed maturity securities, Gross Unrealized Losses, Total $ 34.6       $ 22.3