v3.25.2
Derivative Financial Instruments - Fair Value Hedges (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Fair Value Hedges          
Carrying amount of hedged liability - Active hedging relationships $ 3,331.5   $ 3,331.5   $ 2,769.6
Hedged Liability, Statement of Financial Position [Extensible Enumeration] Contractholder Funds.   Contractholder Funds.   Contractholder Funds.
Carrying amount of hedged liability - Active or discontinued hedging relationships $ 3,331.5   $ 3,331.5   $ 2,769.6
Cumulative amount of fair value hedging basis adjustment - Active hedging relationships 29.8   29.8   (22.0)
Cumulative amount of fair value hedging basis adjustment - Active or discontinued hedging relationships 29.8   29.8   (22.0)
Gain (loss) from components excluded from assessment of fair value hedge effectiveness (2.4) $ 0.7 (1.3) $ 0.7  
Fixed maturities, available-for-sale          
Fair Value Hedges          
Carrying amount of hedged asset - Active hedging relationships $ 3,064.3   $ 3,064.3   $ 3,208.4
Hedged Asset, Statement of Financial Position [Extensible Enumeration] Debt Securities, Available-for-Sale, Excluding Accrued Interest   Debt Securities, Available-for-Sale, Excluding Accrued Interest   Debt Securities, Available-for-Sale, Excluding Accrued Interest
Carrying amount of hedged asset - Discontinued hedging relationships $ 597.8   $ 597.8   $ 528.6
Carrying amount of hedged asset - Active or discontinued hedging relationships 3,662.1   3,662.1   3,737.0
Cumulative amount of fair value hedging basis adjustment - Active hedging relationships (26.9)   (26.9)   (33.1)
Cumulative amount of fair value hedging basis adjustment - Discontinued hedging relationships (6.6)   (6.6)   (7.0)
Cumulative amount of fair value hedging basis adjustment - Active or discontinued hedging relationships (33.5)   (33.5)   (40.1)
Amortized cost basis of closed portfolio used in portfolio layer hedging relationship 2,627.3   2,627.3   2,849.3
Cumulative basis adjustments associated with portfolio layer hedging relationship (25.5)   (25.5)   (55.7)
Amount of hedged item in portfolio layer hedging relationship 1,130.0   1,130.0   1,160.0
Mortgage loans          
Fair Value Hedges          
Carrying amount of hedged asset - Active hedging relationships $ 1,594.6   $ 1,594.6   $ 1,707.1
Hedged Asset, Statement of Financial Position [Extensible Enumeration] Mortgage Loans on Real Estate, Commercial and Consumer, Net   Mortgage Loans on Real Estate, Commercial and Consumer, Net   Mortgage Loans on Real Estate, Commercial and Consumer, Net
Carrying amount of hedged asset - Active or discontinued hedging relationships $ 1,594.6   $ 1,594.6   $ 1,707.1
Cumulative amount of fair value hedging basis adjustment - Active hedging relationships (1.6)   (1.6)   (8.4)
Cumulative amount of fair value hedging basis adjustment - Active or discontinued hedging relationships (1.6)   (1.6)   (8.4)
Amortized cost basis of closed portfolio used in portfolio layer hedging relationship 1,594.6   1,594.6   1,707.1
Cumulative basis adjustments associated with portfolio layer hedging relationship (1.5)   (1.5)   (8.4)
Amount of hedged item in portfolio layer hedging relationship $ 220.0   $ 220.0   $ 220.0