| **Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) - USD ($) $ in Millions** | Mar. 31, 2022 | Dec. 31, 2021 |
|-----------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | $ 41,945      | $ 44,380      |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 981           | 1,035         |
| Short term and other                                                                                                  | 1,173         | 1,872         |
| Total assets                                                                                                          | 44,099        | 47,287        |
| Other liabilities                                                                                                     | (16)          | 12            |
| Total liabilities                                                                                                     | (16)          | 12            |
| Corporate and other bonds                                                                                             |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 23,475        | 24,852        |
| States, municipalities and political subdivisions                                                                     |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 11,059        | 11,943        |
| Asset-backed                                                                                                          |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 7,411         | 7,585         |
| Common Stock                                                                                                          |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 220           | 233           |
| Non-redeemable preferred stock                                                                                        |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 761           | 802           |
| Level 1                                                                                                               |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 129           | 140           |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 254           | 285           |
| Short term and other                                                                                                  | 1,146         | 1,798         |
| Total assets                                                                                                          | 1,529         | 2,223         |
| Other liabilities                                                                                                     | 0             | 0             |
| Total liabilities                                                                                                     | 0             | 0             |
| Level 1 | Corporate and other bonds                                                                                   |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 129           | 140           |
| Level 1 | States, municipalities and political subdivisions                                                           |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 0             | 0             |
| Level 1 | Asset-backed                                                                                                |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 0             | 0             |
| Level 1 | Common Stock                                                                                                |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 191           | 220           |
| Level 1 | Non-redeemable preferred stock                                                                              |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 63            | 65            |
| Level 2                                                                                                               |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 40,246        | 42,691        |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 683           | 721           |
| Short term and other                                                                                                  | 27            | 74            |
| Total assets                                                                                                          | 40,956        | 43,486        |
| Other liabilities                                                                                                     | (16)          | 12            |
| Total liabilities                                                                                                     | (16)          | 12            |
| Level 2 | Corporate and other bonds                                                                                   |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 22,431        | 23,775        |
| Level 2 | States, municipalities and political subdivisions                                                           |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 11,008        | 11,887        |
| Level 2 | Asset-backed                                                                                                |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 6,807         | 7,029         |
| Level 2 | Common Stock                                                                                                |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 0             | 0             |
| Level 2 | Non-redeemable preferred stock                                                                              |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 683           | 721           |
| Level 3                                                                                                               |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 1,570         | 1,549         |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 44            | 29            |
| Short term and other                                                                                                  | 0             | 0             |
| Total assets                                                                                                          | 1,614         | 1,578         |
| Other liabilities                                                                                                     | 0             | 0             |
| Total liabilities                                                                                                     | 0             | 0             |
| Level 3 | Corporate and other bonds                                                                                   |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 915           | 937           |
| Level 3 | States, municipalities and political subdivisions                                                           |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 51            | 56            |
| Level 3 | Asset-backed                                                                                                |          |          |
| **Fixed maturity securities:**                                                                                        |          |          |
| Fixed maturity securities                                                                                             | 604           | 556           |
| Level 3 | Common Stock                                                                                                |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | 29            | 13            |
| Level 3 | Non-redeemable preferred stock                                                                              |          |          |
| **Equity securities:**                                                                                                |          |          |
| Equity securities                                                                                                     | $ 15          | $ 16          |

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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
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Amount, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity), and investment in debt security measured at fair value with change in fair value recognized in net income (trading).
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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.
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| - Definition
Fair value of financial and nonfinancial obligations.
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Fair value portion of other liabilities.
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