v3.25.1
Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses, Fiscal Year Maturity    
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One, Net $ 1,574.7 $ 1,484.1
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five, Net 7,703.6 7,688.2
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10, Net 8,069.3 8,404.6
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10, Net 19,528.7 19,740.8
Available for sale Securities Debt Maturities Amortized Cost Gross Subtotal, Net 36,876.3 37,317.7
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost, Net [1] 980.1 949.4
Debt Securities, Available-for-sale, Amortized Cost, Net of Allowance for Credit Losses 37,856.4 38,267.1
Available for Sale Securities Unrealized Gain Position Gross Gain    
Available For Sale Securities Debt Maturities Within One Year Unrealized Gain Position Gross Gain 5.9 4.1
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Gain Position Gross Gain 152.3 123.5
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Gain Position Gross Gain 257.7 236.4
Available For Sale Securities Debt Maturities After Ten Years Unrealized Gain Position Gross Gain 374.7 307.8
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Gain Gross Subtotal 790.6 671.8
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Gain Position Gross Gain [1] 5.5 5.0
Available for sale Securities, Debt Maturities Unrealized Gain Position Gross Gain 796.1 676.8
Available for Sale Securities Unrealized Loss Position Gross Loss    
Available For Sale Securities Debt Maturities Within One Year Unrealized Loss Position Gross Loss 5.6 6.2
Available For Sale Securities Debt Maturities After One Through Five Years Unrealized Loss Position Gross Loss 164.5 196.6
Available For Sale Securities Debt Maturities After Five Through Ten Years Unrealized Loss Position Gross Loss 478.5 565.5
Available For Sale Securities Debt Maturities After Ten Years Unrealized Loss Position Gross Loss 2,227.7 2,508.5
Available For Sale Securities Debt Maturities Unrealized Gain Position Gross Loss Gross Subtotal 2,876.3 3,276.8
Available For Sale Securities Debt Maturities Without Single Maturity Date Unrealized Loss Position Gross Loss [1] 24.8 37.2
Available For Sale Securities Unrealized Loss Position Gross Loss Subtotal 2,901.1 3,314.0
Fair Value Maturity Distribution [Abstract]    
Debt Securities, Available-for-sale, Total 35,751.4 35,629.9
Available for Sale Securities Unrealized Gain Position Fair Value    
Fair Value Maturity Distribution [Abstract]    
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value 559.5 432.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value 3,233.8 2,840.8
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value 3,799.4 3,486.1
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value 6,505.7 4,965.7
Available for sale Securities Debt Maturities Fair Value Gross Subtotal 14,098.4 11,725.0
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value [1] 441.7 431.4
Debt Securities, Available-for-sale, Total 14,540.1 12,156.4
Available for Sale Securities Unrealized Loss Position Fair Value    
Fair Value Maturity Distribution [Abstract]    
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value 1,015.5 1,049.6
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value 4,457.6 4,774.3
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value 4,049.1 4,589.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value 11,170.0 12,574.4
Available for sale Securities Debt Maturities Fair Value Gross Subtotal 20,692.2 22,987.7
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value [1] 519.1 485.8
Debt Securities, Available-for-sale, Total $ 21,211.3 $ 23,473.5
[1]
1Includes credit-tranched securities collateralized by loan obligations, auto loans, and other asset types