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Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Jun. 30, 2025 | Dec. 31, 2024 | Jun. 30, 2024 | Dec. 31, 2023
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | $ 93,598 |  |  | $ 88,277 |  |
Allowance for expected credit losses | 4 |  |  | 2 |  |
Gross unrealized gains | 883 |  |  | 223 |  |
Gross unrealized losses | 3,364 |  |  | 4,832 |  |
Fixed maturities, at fair value | 91,113 |  |  | 83,666 |  |
Proceeds from sales of fixed maturities classified as available for sale | 779 | $ 1,475 |  |  |  |
Gross realized gains | 1 | 2 |  |  |  |
Gross realized losses on sales of fixed maturities | 29 | 57 |  |  |  |
Realized losses resulting from the early redemption of fixed maturities by the issuer prior to the bonds' maturity date | 20 | 34 |  |  |  |
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 4,084 |  |  | 5,735 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 15 |  |  | 4 |  |
Gross unrealized losses | 86 |  |  | 169 |  |
Fixed maturities, at fair value | 4,013 |  |  | 5,570 |  |
Obligations of U.S. states, municipalities and political subdivisions [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 32,191 |  |  | 29,526 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 153 |  |  | 43 |  |
Gross unrealized losses | 2,040 |  |  | 2,384 |  |
Fixed maturities, at fair value | 30,304 |  |  | 27,185 |  |
Obligations of U.S. states, municipalities and political subdivisions, local general obligation [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 21,171 |  |  | 18,604 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 103 |  |  | 23 |  |
Gross unrealized losses | 1,342 |  |  | 1,604 |  |
Fixed maturities, at fair value | 19,932 |  |  | 17,023 |  |
Obligations of U.S. states, municipalities and political subdivisions, revenue [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 9,677 |  |  | 9,268 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 42 |  |  | 16 |  |
Gross unrealized losses | 642 |  |  | 704 |  |
Fixed maturities, at fair value | 9,077 |  |  | 8,580 |  |
Obligations of U.S. states, municipalities and political subdivisions, state general obligation [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 1,019 |  |  | 1,081 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 5 |  |  | 2 |  |
Gross unrealized losses | 55 |  |  | 73 |  |
Fixed maturities, at fair value | 969 |  |  | 1,010 |  |
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 324 |  |  | 573 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 3 |  |  | 2 |  |
Gross unrealized losses | 1 |  |  | 3 |  |
Fixed maturities, at fair value | 326 |  |  | 572 |  |
Debt securities issued by foreign governments [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 984 |  |  | 917 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 10 |  |  | 5 |  |
Gross unrealized losses | 6 |  |  | 13 |  |
Fixed maturities, at fair value | 988 |  |  | 909 |  |
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 13,287 |  |  | 12,888 |  |
Allowance for expected credit losses | 0 |  |  | 0 |  |
Gross unrealized gains | 225 |  |  | 53 |  |
Gross unrealized losses | 151 |  |  | 336 |  |
Fixed maturities, at fair value | 13,361 |  |  | 12,605 |  |
Corporate and all other bonds [Member] |  |  |  |  |  |
Investment disclosure details |  |  |  |  |  |
Fixed maturities, amortized cost | 43,052 |  |  | 39,211 |  |
Allowance for expected credit losses | 4 | $ 0 | $ 4 | 2 | $ 1 | $ 5
Gross unrealized gains | 480 |  |  | 118 |  |
Gross unrealized losses | 1,081 |  |  | 1,930 |  |
Fixed maturities, at fair value | $ 42,447 |  |  | $ 37,397 |  |

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