| **Investments (Narrative) (Details) $ in Millions**                                                     | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) |
|---------------------------------------------------------------------------------------------------------|-----------------------|-----------------------|-----------------------|
| **Gain (Loss) on Investments**                                                                          |                  |                  |                  |
| Largest single common stock holding                                                                     | $ 414                 |                  |                  |
| Largest equity holdings to total equity portfolio                                                       | 5.50%                 |                  |                  |
| Largest equity holdings to total portfolio                                                              | 2.10%                 |                  |                  |
| Assets Held by Insurance Regulators                                                                     | $ 117                 | $ 112                 |                  |
| Collateral at fair value                                                                                | $ 95                  | $ 75                  |                  |
| Impaired securities                                                                                     | 3                     | 1                     | 6                     |
| Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss | $ 3                   | $ 58                  | $ 18                  |
| Fixed Maturities                                                                                        |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                          |                  |                  |                  |
| Number of securities total unrealized loss in an unrealized loss position for 12 months or more         | 38                    | 400                   | 249                   |
| Number of securities below 70 percent of amortized cost                                                 | 0                     | 0                     | 0                     |
| Equity Securities                                                                                       |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                          |                  |                  |                  |
| Number of securities total unrealized loss in an unrealized loss position for 12 months or more         |                  |                  | 0                     |

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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss, Accumulated in Investments
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| X                                                                                                                                                                                                                                                                            |
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largest equity holdings to total equity portfolio
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Largest equity holdings to total portfolio
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Number of Securities Continuous Unrealized Loss Position More Than Twelve Months and Below 70 Percent of Amortized Cost
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Number of Securities, Other Than Temporary Impairment Losses
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| - Definition
Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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| - Definition
The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.
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