| **Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions** | Mar. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2021 | Dec. 31, 2020 |
|-----------------------------------------------------------------------------------------------------|---------------|---------------|---------------|---------------|
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Gross Unrealized Gains                                                                              | $ 2,191       | $ 4,558       |          |          |
| Gross Unrealized Losses                                                                             | 1,157         | 112           |          |          |
| Allowance for Credit Losses                                                                         | 17            | 18            | $ 43          | $ 40          |
| Estimated Fair Value                                                                                | 41,939        | 44,373        |          |          |
| **Total fixed maturity securities trading**                                                         |          |          |          |          |
| Debt securities, amortized cost                                                                     | 40,928        | 39,952        |          |          |
| Total fixed maturity securities                                                                     | 41,945        | 44,380        |          |          |
| Corporate and other bonds                                                                           |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 22,001        | 21,444        |          |          |
| Gross Unrealized Gains                                                                              | 1,277         | 2,755         |          |          |
| Gross Unrealized Losses                                                                             | 486           | 56            |          |          |
| Allowance for Credit Losses                                                                         | 12            | 11            | 27            | 23            |
| Estimated Fair Value                                                                                | 22,780        | 24,132        |          |          |
| **Total fixed maturity securities trading**                                                         |          |          |          |          |
| Total fixed maturity securities                                                                     | 23,475        | 24,852        |          |          |
| States, municipalities and political subdivisions                                                   |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 10,516        | 10,358        |          |          |
| Gross Unrealized Gains                                                                              | 862           | 1,599         |          |          |
| Gross Unrealized Losses                                                                             | 319           | 14            |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 11,059        | 11,943        |          |          |
| **Total fixed maturity securities trading**                                                         |          |          |          |          |
| Total fixed maturity securities                                                                     | 11,059        | 11,943        |          |          |
| Asset-backed                                                                                        |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 7,701         | 7,441         |          |          |
| Gross Unrealized Gains                                                                              | 49            | 188           |          |          |
| Gross Unrealized Losses                                                                             | 334           | 37            |          |          |
| Allowance for Credit Losses                                                                         | 5             | 7             | $ 16          | $ 17          |
| Estimated Fair Value                                                                                | 7,411         | 7,585         |          |          |
| **Total fixed maturity securities trading**                                                         |          |          |          |          |
| Total fixed maturity securities                                                                     | 7,411         | 7,585         |          |          |
| Residential mortgage-backed                                                                         |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 2,983         | 2,893         |          |          |
| Gross Unrealized Gains                                                                              | 25            | 71            |          |          |
| Gross Unrealized Losses                                                                             | 160           | 8             |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 2,848         | 2,956         |          |          |
| Commercial mortgage-backed                                                                          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 2,008         | 1,987         |          |          |
| Gross Unrealized Gains                                                                              | 13            | 63            |          |          |
| Gross Unrealized Losses                                                                             | 81            | 19            |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 1,940         | 2,031         |          |          |
| Other asset-backed                                                                                  |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 2,710         | 2,561         |          |          |
| Gross Unrealized Gains                                                                              | 11            | 54            |          |          |
| Gross Unrealized Losses                                                                             | 93            | 10            |          |          |
| Allowance for Credit Losses                                                                         | 5             | 7             |          |          |
| Estimated Fair Value                                                                                | 2,623         | 2,598         |          |          |
| Fixed maturity securities                                                                           |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 40,922        | 39,945        |          |          |
| Gross Unrealized Gains                                                                              | 2,191         | 4,558         |          |          |
| Gross Unrealized Losses                                                                             | 1,157         | 112           |          |          |
| Allowance for Credit Losses                                                                         | 17            | 18            |          |          |
| Estimated Fair Value                                                                                | 41,939        | 44,373        |          |          |
| U.S. Treasury and obligations of government-sponsored enterprises                                   |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 125           | 132           |          |          |
| Gross Unrealized Gains                                                                              | 0             | 1             |          |          |
| Gross Unrealized Losses                                                                             | 5             | 3             |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 120           | 130           |          |          |
| Foreign government                                                                                  |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 559           | 570           |          |          |
| Gross Unrealized Gains                                                                              | 3             | 15            |          |          |
| Gross Unrealized Losses                                                                             | 13            | 2             |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 549           | 583           |          |          |
| Redeemable preferred stock                                                                          |          |          |          |          |
| **Fixed maturity securities available-for-sale:**                                                   |          |          |          |          |
| Cost or Amortized Cost                                                                              | 20            | 0             |          |          |
| Gross Unrealized Gains                                                                              | 0             | 0             |          |          |
| Gross Unrealized Losses                                                                             | 0             | 0             |          |          |
| Allowance for Credit Losses                                                                         | 0             | 0             |          |          |
| Estimated Fair Value                                                                                | 20            | 0             |          |          |
| Total fixed maturity securities trading                                                             |          |          |          |          |
| **Total fixed maturity securities trading**                                                         |          |          |          |          |
| Cost or amortized cost, trading securities                                                          | 6             | 7             |          |          |
| Estimated fair value, trading securities                                                            | $ 6           | $ 7           |          |          |

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