v3.26.1
Investments (Investments Classified by Contractual Maturity Date) (Details) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Available-for-sale Securities, Debt Maturities [Abstract]    
Due in one year or less, Amortized Cost, Net of Allowance for Credit Losses $ 113.3  
Due after one year through five years, Amortized Cost, Net of Allowance for Credit Losses 2,574.8  
Due after five years through ten years, Amortized Cost, Net of Allowance for Credit Losses 2,737.3  
Due after ten years, Amortized Cost, Net of Allowance for Credit Losses 402.3  
Gross fixed maturities, Amortized Cost, Net of Allowance for Credit Losses 5,827.7  
Mortgage-backed and other asset-backed securities, Amortized Cost, Net of Allowance for Credit Losses 4,384.1  
Amortized Cost, Net of Allowance for Credit Losses 10,211.8  
Due in one year or less, Fair Value 113.3  
Due after one year through five years, Fair Value 2,529.2  
Due after five years through ten years, Fair Value 2,665.9  
Due after ten years, Fair Value 374.5  
Gross fixed maturities, Fair Value 5,682.9  
Mortgage-backed and other asset-backed securities, Fair Value 4,293.3  
Fixed maturities, Fair Value $ 9,976.2 $ 9,536.5