| **Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions** | Sep. 30, 2024 | Jun. 30, 2024 | Dec. 31, 2023 | Sep. 30, 2023 | Jun. 30, 2023 | Dec. 31, 2022 |
|-----------------------------------------------------------------------------------------------------|---------------|---------------|---------------|---------------|---------------|---------------|
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | $ 43,551      |          | $ 42,414      |          |          |          |
| Gross Unrealized Gains                                                                              | 1,282         |          | 1,022         |          |          |          |
| Gross Unrealized Losses                                                                             | 2,236         |          | 2,995         |          |          |          |
| Allowance for Credit Losses                                                                         | 18            | $ 17          | 16            | $ 18          | $ 22          | $ 1           |
| Estimated Fair Value                                                                                | 42,579        |          | 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                                                                     | 43,551        |          | 42,414        |          |          |          |
| Total fixed maturity securities                                                                     | 42,579        |          | 40,425        |          |          |          |
| Corporate and other bonds                                                                           |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 25,872        |          | 25,020        |          |          |          |
| Gross Unrealized Gains                                                                              | 826           |          | 597           |          |          |          |
| Gross Unrealized Losses                                                                             | 900           |          | 1,345         |          |          |          |
| Allowance for Credit Losses                                                                         | 6             | 0             | 4             | 5             | 13            | 0             |
| Estimated Fair Value                                                                                | 25,792        |          | 24,268        |          |          |          |
| **Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]**                                     |          |          |          |          |          |          |
| Total fixed maturity securities                                                                     | 26,751        |          | 25,132        |          |          |          |
| States, municipalities and political subdivisions                                                   |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 7,406         |          | 7,713         |          |          |          |
| Gross Unrealized Gains                                                                              | 359           |          | 382           |          |          |          |
| Gross Unrealized Losses                                                                             | 617           |          | 703           |          |          |          |
| Allowance for Credit Losses                                                                         | 0             |          | 0             |          |          |          |
| Estimated Fair Value                                                                                | 7,148         |          | 7,392         |          |          |          |
| **Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]**                                     |          |          |          |          |          |          |
| Total fixed maturity securities                                                                     | 7,148         |          | 7,392         |          |          |          |
| Residential mortgage-backed                                                                         |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 3,684         |          | 3,411         |          |          |          |
| Gross Unrealized Gains                                                                              | 32            |          | 16            |          |          |          |
| Gross Unrealized Losses                                                                             | 362           |          | 425           |          |          |          |
| Allowance for Credit Losses                                                                         | 0             |          | 0             |          |          |          |
| Estimated Fair Value                                                                                | 3,354         |          | 3,002         |          |          |          |
| Commercial mortgage-backed                                                                          |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 1,867         |          | 1,862         |          |          |          |
| Gross Unrealized Gains                                                                              | 15            |          | 7             |          |          |          |
| Gross Unrealized Losses                                                                             | 141           |          | 230           |          |          |          |
| Allowance for Credit Losses                                                                         | 0             |          | 8             |          |          |          |
| Estimated Fair Value                                                                                | 1,741         |          | 1,631         |          |          |          |
| Other asset-backed                                                                                  |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 3,743         |          | 3,515         |          |          |          |
| Gross Unrealized Gains                                                                              | 40            |          | 13            |          |          |          |
| Gross Unrealized Losses                                                                             | 186           |          | 256           |          |          |          |
| Allowance for Credit Losses                                                                         | 12            |          | 4             |          |          |          |
| Estimated Fair Value                                                                                | 3,585         |          | 3,268         |          |          |          |
| Asset-backed                                                                                        |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 9,294         |          | 8,788         |          |          |          |
| Gross Unrealized Gains                                                                              | 87            |          | 36            |          |          |          |
| Gross Unrealized Losses                                                                             | 689           |          | 911           |          |          |          |
| Allowance for Credit Losses                                                                         | 12            | $ 17          | 12            | $ 13          | $ 9           | $ 1           |
| Estimated Fair Value                                                                                | 8,680         |          | 7,901         |          |          |          |
| **Debt Securities, Trading, Unrealized Gain (Loss) [Abstract]**                                     |          |          |          |          |          |          |
| Total fixed maturity securities                                                                     | 8,680         |          | 7,901         |          |          |          |
| U.S. Treasury and obligations of government-sponsored enterprises                                   |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 224           |          | 152           |          |          |          |
| Gross Unrealized Gains                                                                              | 2             |          | 1             |          |          |          |
| Gross Unrealized Losses                                                                             | 4             |          | 2             |          |          |          |
| Allowance for Credit Losses                                                                         | 0             |          | 0             |          |          |          |
| Estimated Fair Value                                                                                | 222           |          | 151           |          |          |          |
| Foreign government                                                                                  |          |          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |          |          |
| Cost or Amortized Cost                                                                              | 755           |          | 741           |          |          |          |
| Gross Unrealized Gains                                                                              | 8             |          | 6             |          |          |          |
| Gross Unrealized Losses                                                                             | 26            |          | 34            |          |          |          |
| Allowance for Credit Losses                                                                         | 0             |          | 0             |          |          |          |
| Estimated Fair Value                                                                                | $ 737         |          | $ 713         |          |          |          |

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