| **Investments (Narrative) (Details) (USD $)In Millions, unless otherwise specified**                                              | 3 Months Ended | 9 Months Ended |              |
|-----------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|--------------|
||
| Net unrealized gains (losses) related to changes in fair value of trading securities still held included in net investment income |           | $ (1)          |    | $ (1) |   |
| Payments of debt extinguishment costs                                                                                             |           |           |         | 9 |   |
| Net unrealized gains (losses) related to changes in the fair value of securities for which the fair value option has been elected |      |      |    | 1 |   |
| Reduction of net unrealized gains on investments included in AOCI due to shadow adjustment                                        | 1,277          |           | 1,277        |   | 723 |
| Pretax net unrealized gains on available for sale securities reclassified out of AOCI into earnings                               | 12             | (29)           | 59           | 12 |   |
| Investment commitment [Member]                                                                                                    |           |           |         |   |   |
| Future capital call commitments                                                                                                   | 114            |           | 114          |   |   |
| Commitments to purchase various privately placed debt securities                                                                  | 159            |           | 159          |   |   |
| Commitments to sell various privately placed debt securities                                                                      | 154            |           | 154          |   |   |
| Obligations on unfunded bank loan participations                                                                                  | $ 6            |           | $ 6          |   |   |

| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments To Purchase Various Privately Placed Debt Securities
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments To Sell Various Privately Placed Debt Securities
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Future capital call commitments to third party limited partnerships for which we would receive an ownership interest.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Obligations on Unfunded Bank Loan Participations
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Pretax Net Unrealized Gains On Available For Sale Securities Reclassified Out of AOCI Into Earnings
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents, for each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings during the period and in which line in the income statement those gains and losses are reported. This item may also include amounts of gains and losses for other items measured at fair value, but for which the fair value option has not been elected (for instance, items required to be measured at fair value).
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow for incremental, external costs directly pertaining to an early extinguishment of debt, including legal costs and prepayment penalties, and excluding interest and repayment of debt principal.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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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