| **Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions** | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Balance, Beginning, Assets                                                                                                                                                              | $ 437           | $ 454 |
| Reported in Other comprehensive income (loss)                                                                                                                                           | 41              | (12) |
| Total realized and unrealized investment gains (losses)                                                                                                                                 | 39              | (10) |
| Purchases                                                                                                                                                                               | 306             | 279 |
| Sales                                                                                                                                                                                   | 0               | (77) |
| Settlements                                                                                                                                                                             | (27)            | (74) |
| Transfers into Level 3                                                                                                                                                                  | 45              | 77 |
| Transfers out of Level 3                                                                                                                                                                | (149)           | (212) |
| Balance, Ending, Assets                                                                                                                                                                 | 651             | 437 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Net income (loss) in the period                                                  | (2)             | (4) |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Other comprehensive income (loss) in the period                                  | 35              | (9) |
| Corporate and other bonds                                                                                                                                                               |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Balance, Beginning, Assets                                                                                                                                                              | 222             | 98 |
| Reported in Other comprehensive income (loss)                                                                                                                                           | 33              | (4) |
| Total realized and unrealized investment gains (losses)                                                                                                                                 | 33              | (5) |
| Purchases                                                                                                                                                                               | 256             | 117 |
| Sales                                                                                                                                                                                   | 0               | (5) |
| Settlements                                                                                                                                                                             | (11)            | (9) |
| Transfers into Level 3                                                                                                                                                                  | 0               | 35 |
| Transfers out of Level 3                                                                                                                                                                | (32)            | (9) |
| Balance, Ending, Assets                                                                                                                                                                 | 468             | 222 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Net income (loss) in the period                                                  | 0               | 0 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Other comprehensive income (loss) in the period                                  | 28              | (5) |
| States, municipalities and political subdivisions                                                                                                                                       |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Balance, Beginning, Assets                                                                                                                                                              | 0               | 1 |
| Reported in Other comprehensive income (loss)                                                                                                                                           | 0               | 0 |
| Total realized and unrealized investment gains (losses)                                                                                                                                 | 0               | 0 |
| Purchases                                                                                                                                                                               | 0               | 0 |
| Sales                                                                                                                                                                                   | 0               | 0 |
| Settlements                                                                                                                                                                             | 0               | (1) |
| Transfers into Level 3                                                                                                                                                                  | 0               | 0 |
| Transfers out of Level 3                                                                                                                                                                | 0               | 0 |
| Balance, Ending, Assets                                                                                                                                                                 | 0               | 0 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Net income (loss) in the period                                                  | 0               | 0 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Other comprehensive income (loss) in the period                                  | 0               | 0 |
| Asset-backed                                                                                                                                                                            |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Balance, Beginning, Assets                                                                                                                                                              | 197             | 335 |
| Reported in Other comprehensive income (loss)                                                                                                                                           | 8               | (8) |
| Total realized and unrealized investment gains (losses)                                                                                                                                 | 8               | (3) |
| Purchases                                                                                                                                                                               | 48              | 162 |
| Sales                                                                                                                                                                                   | 0               | (72) |
| Settlements                                                                                                                                                                             | (16)            | (64) |
| Transfers into Level 3                                                                                                                                                                  | 45              | 42 |
| Transfers out of Level 3                                                                                                                                                                | (117)           | (203) |
| Balance, Ending, Assets                                                                                                                                                                 | 165             | 197 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Net income (loss) in the period                                                  | 0               | (2) |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Other comprehensive income (loss) in the period                                  | 7               | (4) |
| Equity securities                                                                                                                                                                       |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Balance, Beginning, Assets                                                                                                                                                              | 18              | 20 |
| Reported in Other comprehensive income (loss)                                                                                                                                           | 0               | 0 |
| Total realized and unrealized investment gains (losses)                                                                                                                                 | (2)             | (2) |
| Purchases                                                                                                                                                                               | 2               | 0 |
| Sales                                                                                                                                                                                   | 0               | 0 |
| Settlements                                                                                                                                                                             | 0               | 0 |
| Transfers into Level 3                                                                                                                                                                  | 0               | 0 |
| Transfers out of Level 3                                                                                                                                                                | 0               | 0 |
| Balance, Ending, Assets                                                                                                                                                                 | 18              | 18 |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Net income (loss) in the period                                                  | (2)             | (2) |
| Unrealized gains (losses) on Level 3 assets and liabilities held as of December 31, 2019 recognized in Other comprehensive income (loss) in the period                                  | 0               | 0 |
| Reported in Net investment gains (losses)                                                                                                                                               |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment gains (losses)                                                                                                                                               | (2)             | 2 |
| Reported in Net investment gains (losses) | Corporate and other bonds                                                                                                                   |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment gains (losses)                                                                                                                                               | 0               | (1) |
| Reported in Net investment gains (losses) | States, municipalities and political subdivisions                                                                                           |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment gains (losses)                                                                                                                                               | 0               | 0 |
| Reported in Net investment gains (losses) | Asset-backed                                                                                                                                |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment gains (losses)                                                                                                                                               | 0               | 5 |
| Reported in Net investment gains (losses) | Equity securities                                                                                                                           |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment gains (losses)                                                                                                                                               | (2)             | (2) |
| Reported in Net investment income                                                                                                                                                       |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment income                                                                                                                                                       | 0               | 0 |
| Reported in Net investment income | Corporate and other bonds                                                                                                                           |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment income                                                                                                                                                       | 0               | 0 |
| Reported in Net investment income | States, municipalities and political subdivisions                                                                                                   |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment income                                                                                                                                                       | 0               | 0 |
| Reported in Net investment income | Asset-backed                                                                                                                                        |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment income                                                                                                                                                       | 0               | 0 |
| Reported in Net investment income | Equity securities                                                                                                                                   |            |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                       |            |   |
| Reported in Net investment income                                                                                                                                                       | $ 0             | $ 0 |

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss), Included In Earnings And Other Comprehensive Income (Loss)
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No definition available.
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Net Investment Income
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No definition available.
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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Other Comprehensive Income (Loss)
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| - Definition
Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.
+ References
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
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| - Definition
Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).
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| - Definition
Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).
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| - Definition
Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.
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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.
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