v3.25.2
Investments - Narrative (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Schedule of Investments [Line Items]    
Investment grade rating 97.10%  
Reverse repurchase agreement, cash to value percentage 95.00%  
Securities sold under agreements to repurchase $ 0.0 $ 12.0
Fair Value 5,453.3 5,387.9
FHLB funding agreements 999.5 989.5
Fair Value    
Schedule of Investments [Line Items]    
Securities sold under agreements to repurchase 0.0 12.4
FHLB of Chicago    
Schedule of Investments [Line Items]    
Fair Value 1,127.7 1,072.2
Governmental Agencies as Required by Law in Various States    
Schedule of Investments [Line Items]    
Fair Value $ 25.8 $ 27.1