| **Investments (Narrative) (Details) (USD $)In Millions, unless otherwise specified**                                              | 3 Months Ended | 6 Months Ended |              |
|-----------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|--------------|
||
| Net unrealized gains (losses) related to changes in fair value of trading securities still held included in net investment income |           |           |    |   |   |
| Net unrealized gains (losses) related to changes in the fair value of securities for which the fair value option has been elected |      |           |         | 1 |   |
| Payments of debt extinguishment costs                                                                                             |           |           |         | 9 |   |
| Reduction of net unrealized gains on investments included in AOCI due to shadow adjustment                                        | 940            |           | 940          |   | 723 |
| Fair value                                                                                                                        | 41,657         |           | 41,657       |   | 40,241 |
| Gross unrealized losses                                                                                                           | 314            |           | 314          |   | 541 |
| Pretax Net Unrealized Gains On Available For Sale Securities Reclassified Out of AOCI Into Earnings                               | 15             | 20             | 47           | 41 |   |
| Commitments to purchase various privately placed debt securities                                                                  | 145            |           | 145          |   |   |
| Commitments to sell various privately placed debt securities                                                                      | 124            |           | 124          |   |   |
| Obligations on unfunded bank loan participations                                                                                  | 12             |           | 12           |   |   |
| Mortgage loan commitments                                                                                                         | 20             |           | 20           |   |   |
| Asset-backed [Member]                                                                                                             |           |           |         |   |   |
| Fair value                                                                                                                        | 8,525          |           | 8,525        |   | 8,084 |
| Number Of Different Asset Backed Securities Comprising Total Fair Value Of Asset backed Holdings                                  | 2,034          |           | 2,034        |   |   |
| Gross unrealized losses                                                                                                           | 169            |           | 169          |   | 246 |
| Mortgage backed securities, issued by U.S. Government sponsored enterprises [Member]                                              |           |           |         |   |   |
| Gross unrealized losses                                                                                                           | 63             |           | 63           |   |   |
| Non-agency structured residential mortgage backed securities [Member]                                                             |           |           |         |   |   |
| Gross unrealized losses                                                                                                           | 78             |           | 78           |   |   |
| Number of securities with at least one trade lot in a gross unrealized loss position                                              | 94             |           | 94           |   |   |
| Severity of gross unrealized loss as percentage of amortized cost                                                                 | 9.00%          |           | 9.00%        |   |   |
| Commercial mortgage-backed [Member]                                                                                               |           |           |         |   |   |
| Fair value                                                                                                                        | 1,569          |           | 1,569        |   | 1,354 |
| Gross unrealized losses                                                                                                           | 27             |           | 27           |   | 59 |
| Number of securities with at least one trade lot in a gross unrealized loss position                                              | 44             |           | 44           |   |   |
| Severity of gross unrealized loss as percentage of amortized cost                                                                 | 8.00%          |           | 8.00%        |   |   |
| Investment commitment [Member]                                                                                                    |           |           |         |   |   |
| Future capital call commitments                                                                                                   | $ 141          |           | $ 141        |   |   |

| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments To Purchase Various Privately Placed Debt Securities
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| X                                                                                                                                                                                                                                                                                                     |
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| - Definition
Commitments To Sell Various Privately Placed Debt Securities
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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.
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| X                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Mortgage loan commitments, representing signed loan applications received and accepted.
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
Number Of Different Asset Backed Securities Comprising Total Fair Value Of Asset backed Holdings
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No definition available.
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| X                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Obligations on Unfunded Bank Loan Participations
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| X                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Pretax Net Unrealized Gains On Available For Sale Securities Reclassified Out of AOCI Into Earnings
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No definition available.
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| - Definition
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments
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| X                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Severity of Gross Unrealized Loss as Percentage of Amortized Cost
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No definition available.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the gross unrealized losses for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.
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No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure regarding factors used to determine that the impairment of securities not categorized as either held-to-maturity securities or trading securities (hence equal to available for sale securities) where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the available-for-sale investments determined to be temporarily impaired.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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).
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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.
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No definition available.
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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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