| **Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions**          | 3 Months Ended | 9 Months Ended |        |         |         |        |         |         |
|---------------------------------------------------------------------------------------|----------------|----------------|--------|---------|---------|--------|---------|---------|
||
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax         |           |           |   |    | $ 2,503 |   |    | $ 0     |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               | $ (4)          |           | $ (4)  |    | (4)     |   | $ 2,788 |    |   |   |
| Accumulated other comprehensive income, net of tax, end of period                     | (4)            |           | (4)    |    |    |   |    |    |   |   |
| Accumulated Net Unrealized Investment Gain (Loss)                                     |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               | 84             | $ 2,977        | 385    | $ 2,625 |    |   |    |    |   |   |
| Cumulative effect of change in accounting for equity securities, before tax           |           |           |   |    |    |   | (3,155) |    |   | $ 0 |
| Other comprehensive income before reclassification, before tax                        | (76)           | 193            | (371)  | 694     |    |   |    |    |   |   |
| Reclassification adjustment, before tax                                               | (1)            | (4)            | 7      | (153)   |    |   |    |    |   |   |
| Effect on other comprehensive income, before tax                                      | (77)           | 189            | (378)  | 541     |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, end of period                     | 7              | 3,166          | 7      | 3,166   |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      | 17             | 1,031          | 81     | 908     |    |   |    |    |   |   |
| Cumulative effect of change in accounting for equity securities, tax                  |           |           |   |    |    |   | (652)   |    |   | 0 |
| Other comprehensive income before reclassification, tax                               | (17)           | 67             | (80)   | 243     |    |   |    |    |   |   |
| Reclassification adjustment, tax                                                      | 0              | (1)            | (1)    | (54)    |    |   |    |    |   |   |
| Effect on other comprehensive income, tax                                             | (17)           | 66             | (81)   | 189     |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, end of period                            | 0              | 1,097          | 0      | 1,097   |    |   |    |    |   |   |
| Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax         |           |           |   |    |    |   | (2,503) |    |   | 0 |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               | 7              | 2,069          | 7      | 2,069   | 7       | $ 67   | 304     | 2,069   | $ 1,946 | 1,717 |
| Other comprehensive income before reclassification, net of tax                        | (59)           | 126            | (291)  | 451     |    |   |    |    |   |   |
| Reclassification adjustment, net of tax                                               | (1)            | (3)            | (6)    | (99)    |    |   |    |    |   |   |
| Effect on other comprehensive income, net of tax                                      | (60)           | 123            | (297)  | 352     |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, end of period                     | 7              | 2,069          | 7      | 2,069   |    |   |    |    |   |   |
| Accumulated Defined Benefit Plans Adjustment                                          |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               | (11)           | (25)           | (12)   | (26)    |    |   |    |    |   |   |
| Other comprehensive income before reclassification, before tax                        | 0              | 0              | 0      | 0       |    |   |    |    |   |   |
| Reclassification adjustment, before tax                                               | 0              | 1              | 1      | 2       |    |   |    |    |   |   |
| Effect on other comprehensive income, before tax                                      | 0              | 1              | 1      | 2       |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, end of period                     | (11)           | (24)           | (11)   | (24)    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      | (1)            | (8)            | (1)    | (8)     |    |   |    |    |   |   |
| Other comprehensive income before reclassification, tax                               | 0              | 0              | 0      | 0       |    |   |    |    |   |   |
| Reclassification adjustment, tax                                                      | 0              | 1              | 0      | 1       |    |   |    |    |   |   |
| Effect on other comprehensive income, tax                                             | 0              | 1              | 0      | 1       |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, end of period                            | (1)            | (7)            | (1)    | (7)     |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               | (10)           | (17)           | (10)   | (17)    | (10)    | (10)   | (11)    | (17)    | (17) | (18) |
| Other comprehensive income before reclassification, net of tax                        | 0              | 0              | 0      | 0       |    |   |    |    |   |   |
| Reclassification adjustment, net of tax                                               | 0              | 0              | 1      | 1       |    |   |    |    |   |   |
| Effect on other comprehensive income, net of tax                                      | 0              | 0              | 1      | 1       |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, end of period                     | (10)           | (17)           | (10)   | (17)    |    |   |    |    |   |   |
| Accumulated Net Unrealized Gain (Loss) on Deferred Costs, Reserves And Other          |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               | (2)            | (6)            | (10)   | (9)     |    |   |    |    |   |   |
| Other comprehensive income before reclassification, before tax                        | 0              | 1              | 6      | 4       |    |   |    |    |   |   |
| Reclassification adjustment, before tax                                               | 1              | (3)            | 3      | (3)     |    |   |    |    |   |   |
| Effect on other comprehensive income, before tax                                      | 1              | (2)            | 9      | 1       |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, end of period                     | (1)            | (8)            | (1)    | (8)     |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      | 0              | (2)            | (2)    | (3)     |    |   |    |    |   |   |
| Other comprehensive income before reclassification, tax                               | 0              | 0              | 1      | 1       |    |   |    |    |   |   |
| Reclassification adjustment, tax                                                      | 0              | (1)            | 1      | (1)     |    |   |    |    |   |   |
| Effect on other comprehensive income, tax                                             | 0              | (1)            | 2      | 0       |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, end of period                            | 0              | (3)            | 0      | (3)     |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               | (1)            | (5)            | (1)    | (5)     | (1)     | (2)    | (8)     | (5)     | (4) | (6) |
| Other comprehensive income before reclassification, net of tax                        | 0              | 1              | 5      | 3       |    |   |    |    |   |   |
| Reclassification adjustment, net of tax                                               | 1              | (2)            | 2      | (2)     |    |   |    |    |   |   |
| Effect on other comprehensive income, net of tax                                      | 1              | (1)            | 7      | 1       |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, end of period                     | (1)            | (5)            | (1)    | (5)     |    |   |    |    |   |   |
| Accumulated Other Comprehensive Income (Loss)                                         |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               | 71             | 2,946          | 363    | 2,590   |    |   |    |    |   |   |
| Cumulative effect of change in accounting for equity securities, before tax           |           |           |   |    |    |   | (3,155) |    |   | 0 |
| Change in unrealized gains, net, on investments available for sale, before tax        | (77)           | 189            | (378)  | 541     |    |   |    |    |   |   |
| Change in pension obligations, before tax                                             | 0              | 1              | 1      | 2       |    |   |    |    |   |   |
| Change in life deferred acquisition costs, life policy reserves and other, before tax | 1              | (2)            | 9      | 1       |    |   |    |    |   |   |
| Effect on other comprehensive income, before tax                                      | (76)           | 188            | (368)  | 544     |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, end of period                     | (5)            | 3,134          | (5)    | 3,134   |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      | 16             | 1,021          | 78     | 897     |    |   |    |    |   |   |
| Cumulative effect of change in accounting for equity securities, tax                  |           |           |   |    |    |   | (652)   |    |   | 0 |
| Change in unrealized gains, net, on investments available for sale, tax               | (17)           | 66             | (81)   | 189     |    |   |    |    |   |   |
| Change in pension obligations, tax                                                    | 0              | 1              | 0      | 1       |    |   |    |    |   |   |
| Change in life deferred acquisition costs, life policy reserves and other, tax        | 0              | (1)            | 2      | 0       |    |   |    |    |   |   |
| Effect on other comprehensive income, tax                                             | (17)           | 66             | (79)   | 190     |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, end of period                            | (1)            | 1,087          | (1)    | 1,087   |    |   |    |    |   |   |
| Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax         |           |           |   |    | (2,503) |   | (2,503) |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               | (4)            | 2,047          | (4)    | 2,047   | $ (4)   | $ 55   | 285     | $ 2,047 | $ 1,925 | 1,693 |
| Cumulative effect of change in accounting for equity securities, net                  |           |           |   |    |    |   |    |    |   | 0 |
| Change in unrealized gains, net, on investments available for sale, net of tax        | (60)           | 123            | (297)  | 352     |    |   |    |    |   |   |
| Change in pension obligations, net of tax                                             | 0              | 0              | 1      | 1       |    |   |    |    |   |   |
| Change in life deferred acquisition costs, life policy reserves and other, net of tax | 1              | (1)            | 7      | 1       |    |   |    |    |   |   |
| Effect on other comprehensive income, net of tax                                      | (59)           | 122            | (289)  | 354     |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, end of period                     | $ (4)          | $ 2,047        | (4)    | 2,047   |    |   |    |    |   |   |
| Previously Reported | Accumulated Net Unrealized Investment Gain (Loss)               |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               |           |           | 3,540  | 2,625   |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      |           |           | 733    | 908     |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               |           |           |   |    |    |   | 2,807   |    |   | 1,717 |
| Previously Reported | Accumulated Other Comprehensive Income (Loss)                   |           |           |   |    |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income Loss Before Tax [Abstract]**                 |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, before tax, beginning of period               |           |           | 3,518  | 2,590   |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Tax [Abstract]**                     |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, tax, beginning of period                      |           |           | $ 730  | $ 897   |    |   |    |    |   |   |
| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**              |           |           |   |    |    |   |    |    |   |   |
| Accumulated other comprehensive income, net of tax, beginning of period               |           |           |   |    |    |   | $ 2,788 |    |   | $ 1,693 |

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Other Comprehensive Income (Loss), Available-for-sale Securities and Other Assets Adjustment, before Tax
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Other Comprehensive Income (Loss), Deferred Acquisition Costs, Life Policy Reserves and Other Adjustment, before Tax
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Unrealized gains on equity securities reclassified from accumulated other comprehensive income to retained earnings, after tax upon adoption of ASU 2016-01.
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| - Definition
Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, including portion attributable to noncontrolling interest. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).
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| - Definition
Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.
+ References
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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.
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| - Definition
Amount before tax and reclassification adjustments of other comprehensive income (loss).
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| - Definition
Amount after tax, before reclassification adjustments of other comprehensive income (loss).
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| - Definition
Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss).
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