| **Investments (Narrative) (Details) (USD $)In Millions, unless otherwise specified**                                              | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| Net unrealized gains (losses) related to changes in fair value of trading securities still held included in net investment income |       |   |    |
| Number of non-income producing fixed maturity securities                                                                          | 9               | 9 |   |
| Fair value of non income fixed maturity security                                                                                  | 1               | 3 |   |
| Number of investments that exceed ten percent of stockholders' equity                                                             |       |    |   |
| Net unrealized gains (losses) related to changes in the fair value of securities for which the fair value option has been elected | (1)             | 2 | (1) |
| Limited partnership investments                                                                                                   | 2,462           | 2,245 |   |
| Undistributed earnings of limited partnership investments                                                                         | 768             | 560 |   |
| Percentage of limited partnerships reported on a current basis                                                                    | 67.00%          |   |   |
| Percentage of limited partnerships reported on a one month lag                                                                    | 17.00%          |   |   |
| Number of active limited partnership investments held                                                                             | 79              | 79 |   |
| Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments                 | 80.00%          | 81.00% |   |
| Percentage of equity related limited partnership hedge fund strategies                                                            | 48.00%          |   |   |
| Percentage of multistrategy approach limited partnership hedge fund strategies                                                    | 27.00%          |   |   |
| Percentage of distressed investments limited partnership hedge fund strategies                                                    | 22.00%          |   |   |
| Percentage of fixed income limited partnership hedge fund strategies                                                              | 3.00%           |   |   |
| Limited partnerships invested in private equity                                                                                   | 16.00%          | 14.00% |   |
| Carrying value of ten largest limited partnerships                                                                                | 1,309           | 1,218 |   |
| Carrying value of limited partnerships as percentage of aggregate partnership equity                                              | 4.00%           | 4.00% |   |
| Income As Percentage Of Change In Partnership Equity For All Limited Partnerships                                                 | 3.00%           | 4.00% | 3.00% |
| Commercial mortgage loans past due or in non-accrual status                                                                       |       |    |   |
| Valuation allowances recorded on commercial mortgage loans                                                                        |       |    |   |
| Future capital call commitments for limited partnership investments                                                               | 202             |   |   |
| Mortgage loan commitments                                                                                                         | 22              |   |   |
| Commitments to purchase various privately placed debt securities                                                                  | 185             |   |   |
| Commitments to sell various privately placed debt securities                                                                      | 164             |   |   |
| Carrying value of securities deposited under requirements of regulatory authorities                                               | 3,600           | 3,500 |   |
| Cash and securities deposited as collateral for letters of credit                                                                 | 4               | 5 |   |
| Carrying value of assets deposited to secure reinsurance and third party obligations                                              | $ 277           | $ 288 |   |

| X                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying Value of Assets Deposited to Secure Reinsurance and Third Party Obligations
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| X                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying value Of Limited Partnerships As Percentage of Aggregate Partnership Equity
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying Value Of Securities Deposited Under Requirements Of Regulatory Authorities
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| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying Value Of Ten Largest Limited Partnerships
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| X                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Cash And Securities Deposited As Collateral For Letters Of Credit
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| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments To Purchase Various Privately Placed Debt Securities
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| X                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments To Sell Various Privately Placed Debt Securities
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No definition available.
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| X                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair Value Of Non Income Fixed Maturity Security
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| X                                                                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Future capital call commitments to limited partnerships for which we would receive an ownership interest.
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| X                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Income As Percentage Of Change In Partnership Equity For All Limited Partnerships
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the carrying amount on the entity's balance sheet of its investment in limited partnerships.
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| X                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Limited Partnerships Invested In Private Equity
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| X                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Mortgage loan commitments, representing signed loan applications received and accepted.
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| X                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of active limited partnership investments held
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| X                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of 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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No definition available.
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| X                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of Non-Income Producing Fixed Maturity Securities
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| X                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Distressed Investments Limited Partnership Hedge Fund Strategies
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| X                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Equity Related Limited Partnership Hedge Fund Strategies
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| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Fixed Income Limited Partnership Hedge Fund Strategies
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| X                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of total carrying value of limited partnerships reported on a current basis
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| X                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of total carrying value of limited partnerships reported on a one month lag.
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| X                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Multistrategy Approach Limited Partnership Hedge Fund Strategies
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A valuation allowance for financing receivables that are expected to be uncollectible.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded Investment in financing receivables that are past due at the balance sheet date.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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).
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period. Trading securities are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) and the change in net unrealized holding gain (loss) is included in earnings for the period.
+ References
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