| **Investments (Narrative) (Details) - USD ($)**                                                                   | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Non-income producing fixed maturity securities                                                                    | $ 1,000,000     | $ 1,000,000 |   |
| Investments that exceed ten percent of stockholders' equity                                                       | 0               | 0 |   |
| Mortgage loan losses due to changes in expected credit losses                                                     | (10,000,000)    | 21,000,000 | $ 0 |
| Limited partnership investments                                                                                   | 1,859,000,000   | 1,619,000,000 |   |
| Undistributed earnings of limited partnership investments                                                         | $ 266,000,000   | $ 235,000,000 |   |
| Percentage of limited partnerships reported on a current basis                                                    | 32.00%          |   |   |
| Percentage of limited partnerships reported on a one month lag                                                    | 6.00%           |   |   |
| Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments | 32.00%          | 51.00% |   |
| Limited partnerships invested in private debt and equity                                                          | 68.00%          | 49.00% |   |
| Carrying value of ten largest limited partnerships                                                                | $ 665,000,000   | $ 775,000,000 |   |
| Carrying value of limited partnerships as percentage of aggregate partnership equity                              | 1.00%           | 2.00% |   |
| Income as percentage of change in partnership equity for all limited partnerships                                 | 2.00%           | 2.00% | 2.00% |
| Obligation to return cash                                                                                         | $ 0             | $ 0 |   |
| Notional value                                                                                                    | 270,000,000     | 190,000,000 |   |
| Derivative liability, fair value, gross liability                                                                 | (12,000,000)    | (19,000,000) |   |
| Commitments to purchase or fund privately placed debt securities                                                  | 1,230,000,000   |   |   |
| Commitments to sell various privately placed debt securities                                                      | 90,000,000      |   |   |
| Carrying value of securities deposited under requirements of regulatory authorities                               | 3,000,000,000   | 3,000,000,000 |   |
| Cash and securities deposited as collateral for letters of credit                                                 | 1,200,000,000   | 1,100,000,000 |   |
| Non-Income Producing Mortgage Loans                                                                               | 7,000,000       | 0 |   |
| 5.875% face amount of $500, due August 15, 2020 | Senior Notes                                                    |            |   |   |
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Realized investment gains (losses)                                                                                |            | (20,000,000) | $ 21,000,000 |
| Face amount                                                                                                       |            | 400,000,000 | 500,000,000 |
| Common Stock                                                                                                      |            |   |   |
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Equity securities, FV-NI, gain (loss)                                                                             | 28,000,000      | 34,000,000 |   |
| Non-redeemable preferred stock                                                                                    |            |   |   |
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Equity securities, FV-NI, gain (loss)                                                                             | 2,000,000       | (3,000,000) |   |
| Fixed maturity securities                                                                                         |            |   |   |
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Debt securities, available-for-sale, accrued interest, after allowance for credit loss                            | 369,000,000     | 371,000,000 |   |
| OCI, debt securities, available-for-sale, gain (loss), after adjustment, before tax                               | (1,272,000,000) | $ 1,637,000,000 | $ 2,620,000,000 |
| Mortgage loans                                                                                                    |            |   |   |
| **Gain (Loss) on Securities [Line Items]**                                                                        |            |   |   |
| Financing receivable, accrued interest, after allowance for credit loss                                           | $ 3,000,000     |   |   |

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Carrying value Of Limited Partnerships As Percentage of Aggregate Partnership Equity
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Carrying Value Of Ten Largest Limited Partnerships
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Cash And Securities Deposited As Collateral For Letters Of Credit
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Commitments To Purchase Or Fund Additional Amounts
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Investments that Exceed Ten Percent of Stockholders' Equity, other than investments in U.S. Treasury and U.S. Government agency securities.
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Non-Income Producing Fixed Maturity Securities
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Non-Income Producing Mortgage Loans
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Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments
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Percentage of total carrying value of limited partnerships reported on a current basis
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Percentage of total carrying value of limited partnerships reported on a one month lag.
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Face (par) amount of debt instrument at time of issuance.
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Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).
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| - Definition
Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.
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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.
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Nominal or face amount used to calculate payment on derivative.
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Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).
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Amount, after allowance for credit loss, of accrued interest on financing receivable.
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Amount, before tax and after adjustment, of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.
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Amount of credit loss expense (reversal of expense) for financing receivable.
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Amount of realized gain (loss) on investment.
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Amount of consolidated retained earnings that represent undistributed (not yet received) earnings from 50% or less owned persons accounted for by the equity method (equity method investees).
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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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