| **Investments (Fair Values And Unrealized Losses By Investment Category And By The Duration Of The Securities' Continuous Unrealized Loss Position) (Details) - USD ($) $ in Millions** | Dec. 31, 2018 | Dec. 31, 2017 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          |          | $ 809         |
| Less than 12 Months, Unrealized losses                                                                                                                                                  |          | 20            |
| 12 months or more fair value                                                                                                                                                            |          | 682           |
| 12 Months or more, unrealized losses                                                                                                                                                    |          | 18            |
| Total fair value                                                                                                                                                                        |          | 1,491         |
| Total Unrealized Losses                                                                                                                                                                 |          | 38            |
| Fixed Maturities                                                                                                                                                                        |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | $ 3,031       | 580           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 70            | 6             |
| 12 months or more fair value                                                                                                                                                            | 1,149         | 682           |
| 12 Months or more, unrealized losses                                                                                                                                                    | 58            | 18            |
| Total fair value                                                                                                                                                                        | 4,180         | 1,262         |
| Total Unrealized Losses                                                                                                                                                                 | 128           | 24            |
| Fixed Maturities | Corporate Securities                                                                                                                                                 |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 2,082         | 330           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 51            | 4             |
| 12 months or more fair value                                                                                                                                                            | 501           | 252           |
| 12 Months or more, unrealized losses                                                                                                                                                    | 36            | 9             |
| Total fair value                                                                                                                                                                        | 2,583         | 582           |
| Total Unrealized Losses                                                                                                                                                                 | 87            | 13            |
| Fixed Maturities | States, Municipalities and Political Subdivisions                                                                                                                    |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 823           | 88            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 18            | 1             |
| 12 months or more fair value                                                                                                                                                            | 340           | 264           |
| 12 Months or more, unrealized losses                                                                                                                                                    | 13            | 5             |
| Total fair value                                                                                                                                                                        | 1,163         | 352           |
| Total Unrealized Losses                                                                                                                                                                 | 31            | 6             |
| Fixed Maturities | Commercial Mortgage Backed Securities                                                                                                                                |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 77            | 33            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 0             | 0             |
| 12 months or more fair value                                                                                                                                                            | 64            | 36            |
| 12 Months or more, unrealized losses                                                                                                                                                    | 2             | 1             |
| Total fair value                                                                                                                                                                        | 141           | 69            |
| Total Unrealized Losses                                                                                                                                                                 | 2             | 1             |
| Fixed Maturities | Government-Sponsored Enterprises                                                                                                                                     |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 49            | 96            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 1             | 1             |
| 12 months or more fair value                                                                                                                                                            | 211           | 124           |
| 12 Months or more, unrealized losses                                                                                                                                                    | 6             | 3             |
| Total fair value                                                                                                                                                                        | 260           | 220           |
| Total Unrealized Losses                                                                                                                                                                 | 7             | 4             |
| Fixed Maturities | Foreign government                                                                                                                                                   |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          |          | 10            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  |          | 0             |
| 12 months or more fair value                                                                                                                                                            |          | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    |          | 0             |
| Total fair value                                                                                                                                                                        |          | 10            |
| Total Unrealized Losses                                                                                                                                                                 |          | 0             |
| Fixed Maturities | United States Government                                                                                                                                             |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 0             | 23            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 0             | 0             |
| 12 months or more fair value                                                                                                                                                            | 33            | 6             |
| 12 Months or more, unrealized losses                                                                                                                                                    | 1             | 0             |
| Total fair value                                                                                                                                                                        | 33            | 29            |
| Total Unrealized Losses                                                                                                                                                                 | $ 1           | 0             |
| Equity Securities                                                                                                                                                                       |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          |          | 229           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  |          | 14            |
| 12 months or more fair value                                                                                                                                                            |          | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    |          | 0             |
| Total fair value                                                                                                                                                                        |          | 229           |
| Total Unrealized Losses                                                                                                                                                                 |          | 14            |
| Equity Securities | Common Equities                                                                                                                                                     |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          |          | 229           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  |          | 14            |
| 12 months or more fair value                                                                                                                                                            |          | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    |          | 0             |
| Total fair value                                                                                                                                                                        |          | 229           |
| Total Unrealized Losses                                                                                                                                                                 |          | $ 14          |

| X                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Investments, Unrealized Loss Position [Line Items]
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| - Definition
Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.
+ References
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| - Definition
Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.
+ References
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| - Definition
This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.
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| - Definition
Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.
+ References
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| - Definition
This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.
+ References
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| - Definition
This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer.
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