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Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | $ 43,481 | $ 42,414 |
Gross Unrealized Gains | 715 | 1,022 |
Gross Unrealized Losses | 3,040 | 2,995 |
Allowance for Credit Losses | 45 | 16 | $ 1
Estimated Fair Value | 41,111 | 40,425 |
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract] |  |  |
Total fixed maturity securities trading | 0 | 0 |
Total fixed maturity securities trading | 0 | 0 |
Debt securities, amortized cost | 43,481 | 42,414 |
Total fixed maturity securities | 41,111 | 40,425 |
Corporate and other bonds |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 25,839 | 25,020 |
Gross Unrealized Gains | 423 | 597 |
Gross Unrealized Losses | 1,305 | 1,345 |
Allowance for Credit Losses | 13 | 4 | 0
Estimated Fair Value | 24,944 | 24,268 |
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract] |  |  |
Total fixed maturity securities | 25,841 | 25,132 |
States, municipalities and political subdivisions |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 7,396 | 7,713 |
Gross Unrealized Gains | 243 | 382 |
Gross Unrealized Losses | 835 | 703 |
Allowance for Credit Losses | 0 | 0 |
Estimated Fair Value | 6,804 | 7,392 |
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract] |  |  |
Total fixed maturity securities | 6,804 | 7,392 |
Residential mortgage-backed |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 3,725 | 3,411 |
Gross Unrealized Gains | 7 | 16 |
Gross Unrealized Losses | 488 | 425 |
Allowance for Credit Losses | 0 | 0 |
Estimated Fair Value | 3,244 | 3,002 |
Commercial mortgage-backed |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 1,830 | 1,862 |
Gross Unrealized Gains | 11 | 7 |
Gross Unrealized Losses | 142 | 230 |
Allowance for Credit Losses | 18 | 8 |
Estimated Fair Value | 1,681 | 1,631 |
Other asset-backed |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 3,770 | 3,515 |
Gross Unrealized Gains | 24 | 13 |
Gross Unrealized Losses | 239 | 256 |
Allowance for Credit Losses | 14 | 4 |
Estimated Fair Value | 3,541 | 3,268 |
Asset-backed |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 9,325 | 8,788 |
Gross Unrealized Gains | 42 | 36 |
Gross Unrealized Losses | 869 | 911 |
Allowance for Credit Losses | 32 | 12 | $ 1
Estimated Fair Value | 8,466 | 7,901 |
Debt Securities, Trading, Unrealized Gain (Loss) [Abstract] |  |  |
Total fixed maturity securities | 8,466 | 7,901 |
U.S. Treasury and obligations of government-sponsored enterprises |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 220 | 152 |
Gross Unrealized Gains | 1 | 1 |
Gross Unrealized Losses | 1 | 2 |
Allowance for Credit Losses | 0 | 0 |
Estimated Fair Value | 220 | 151 |
Foreign government |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 701 | 741 |
Gross Unrealized Gains | 6 | 6 |
Gross Unrealized Losses | 30 | 34 |
Allowance for Credit Losses | 0 | 0 |
Estimated Fair Value | 677 | 713 |
Redeemable preferred stock |  |  |
Fixed maturity securities available-for-sale: |  |  |
Cost or Amortized Cost | 0 | 0 |
Gross Unrealized Gains | 0 | 0 |
Gross Unrealized Losses | 0 | 0 |
Allowance for Credit Losses | 0 | 0 |
Estimated Fair Value | $ 0 | $ 0 |

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