| **Investments (Narrative) (Details) $ in Millions**                                                                                                                                | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------|-----------------------|-----------------------|
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Largest equity holdings to total equity portfolio                                                                                                                                  | 3.30%                 |                  |                  |
| Largest equity holdings to total portfolio                                                                                                                                         | 1.00%                 |                  |                  |
| Investments, deposit with various states                                                                                                                                           | $ 74                  | $ 75                  |                  |
| Investments in fair value, deposit with various states                                                                                                                             | $ 15,114              | $ 15,067              |                  |
| Impaired securities                                                                                                                                                                | 20                    | 6                     | 7                     |
| Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss                                                                            | $ 37                  | $ 10                  | $ 5                   |
| Fixed Maturities                                                                                                                                                                   |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Number of securities total unrealized loss in an unrealized loss position for 12 months or more                                                                                    | 69                    | 144                   | 40                    |
| Number Of Securities Continuous Unrealized Loss Position More Than Twelve Months and Below 70 Percent of Amortized Cost                                                            | 5                     |                  |                  |
| Equity Securities                                                                                                                                                                  |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Number of securities total unrealized loss in an unrealized loss position for 12 months or more                                                                                    | 0                     | 3                     | 0                     |
| Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate loss                                                                            |                  | $ 1                   |                  |
| Exxon Mobil Corporation, The Procter & Gamble Company, Honeywell International Inc, BlackRock Inc., Genuine Parts Company, RPM International, and Johnson and Johnson [Member] |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Available-for-sale securities, accumulated net gain position                                                                                                                       | $ 566                 |                  |                  |
| Seven Primary Contributors                                                                                                                                                         |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Number of securities                                                                                                                                                               | 7                     |                  |                  |
| On Deposit With Various States                                                                                                                                                     |                  |                  |                  |
| **Gain (Loss) on Investments**                                                                                                                                                     |                  |                  |                  |
| Investments in fair value, deposit with various states                                                                                                                             | $ 77                  | $ 78                  |                  |

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