v3.26.1
Fair Value Measurements - Fair Value Hierarchy for Assets Measured at Fair Value on Recurring Basis (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value $ 18,954 $ 18,123
Fair value of asset 33,352 31,974
Separate accounts 996 981
Short-Term Investments 142 148
Top Hat savings plan mutual funds and common equity (included in Other assets) 112 102
Corporate    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 10,456 9,711
States, municipalities and political subdivisions    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 4,882 4,919
Government-sponsored enterprises    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 2,471 2,359
Asset-backed    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 808 797
United States government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 317 313
Foreign government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 20 24
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 317 313
Fair value of asset 13,554 12,971
Short-Term Investments 142 148
Top Hat savings plan mutual funds and common equity (included in Other assets) 112 102
Level 1 | Corporate    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 1 | States, municipalities and political subdivisions    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 1 | Government-sponsored enterprises    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 1 | Asset-backed    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 1 | United States government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 317 313
Level 1 | Foreign government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 18,637 17,810
Fair value of asset 19,798 19,003
Short-Term Investments 0 0
Top Hat savings plan mutual funds and common equity (included in Other assets) 0 0
Level 2 | Corporate    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 10,456 9,711
Level 2 | States, municipalities and political subdivisions    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 4,882 4,919
Level 2 | Government-sponsored enterprises    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 2,471 2,359
Level 2 | Asset-backed    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 808 797
Level 2 | United States government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 2 | Foreign government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 20 24
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Fair value of asset 0 0
Short-Term Investments 0 0
Top Hat savings plan mutual funds and common equity (included in Other assets) 0 0
Level 3 | Corporate    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 3 | States, municipalities and political subdivisions    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 3 | Government-sponsored enterprises    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 3 | Asset-backed    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 3 | United States government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Level 3 | Foreign government    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fixed maturities, at fair value 0 0
Equity securities | Common equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 12,883 12,373
Equity securities | Nonredeemable preferred equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 311 321
Equity securities | Level 1 | Common equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 12,883 12,373
Equity securities | Level 1 | Nonredeemable preferred equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 0 0
Equity securities | Level 2 | Common equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 0 0
Equity securities | Level 2 | Nonredeemable preferred equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 311 321
Equity securities | Level 3 | Common equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 0 0
Equity securities | Level 3 | Nonredeemable preferred equities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Fair value of asset 0 0
Separate accounts taxable fixed maturities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Separate accounts 950 907
Separate accounts taxable fixed maturities | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Separate accounts 100 35
Separate accounts taxable fixed maturities | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Separate accounts 850 872
Separate accounts taxable fixed maturities | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis    
Separate accounts $ 0 $ 0