| **Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions**    | 3 Months Ended | 9 Months Ended |
|-----------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                      |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                    | $ 210          | $ 143          | $ (315) | $ 400 |
| Other comprehensive income (loss), before reclassifications                                         | 52             | (118)          | 566 | (385) |
| Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit | 25             | (35)           | 14 | (45) |
| Other comprehensive income (loss) after tax (expense) benefit                                       | 27             | (83)           | 552 | (340) |
| Accumulated other comprehensive income (loss), ending balance                                       | 237            | 60             | 237 | 60 |
| Reclassification from AOCI, Current Period, Tax                                                     | (12)           | 19             | (4) | 31 |
| Tax (expense) benefit on other comprehensive income (loss)                                          | (24)           | 18             | (305) | 113 |
| Net unrealized gains (losses) on investments with OTTI losses [Member]                              |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                      |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                    | 31             | 31             | 27 | 36 |
| Other comprehensive income (loss), before reclassifications                                         | 7              | 2              | 9 | (3) |
| Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit | 4              | 0              | 2 | 0 |
| Other comprehensive income (loss) after tax (expense) benefit                                       | 3              | 2              | 7 | (3) |
| Accumulated other comprehensive income (loss), ending balance                                       | 34             | 33             | 34 | 33 |
| Reclassification from AOCI, Current Period, Tax                                                     | (2)            | 0              | (1) | 0 |
| Tax (expense) benefit on other comprehensive income (loss)                                          | (2)            | (1)            | (4) | 1 |
| Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]                              |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                      |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                    | 934            | 689            | 390 | 942 |
| Other comprehensive income (loss), before reclassifications                                         | 69             | (67)           | 615 | (318) |
| Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit | 27             | (31)           | 29 | (29) |
| Other comprehensive income (loss) after tax (expense) benefit                                       | 42             | (36)           | 586 | (289) |
| Accumulated other comprehensive income (loss), ending balance                                       | 976            | 653            | 976 | 653 |
| Reclassification from AOCI, Current Period, Tax                                                     | (13)           | 17             | (12) | 22 |
| Tax (expense) benefit on other comprehensive income (loss)                                          | (19)           | 21             | (292) | 140 |
| Pension and postretirement benefits [Member]                                                        |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                      |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                    | (637)          | (585)          | (648) | (633) |
| Other comprehensive income (loss), before reclassifications                                         | 0              | 0              | 0 | 36 |
| Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit | (6)            | (4)            | (17) | (16) |
| Other comprehensive income (loss) after tax (expense) benefit                                       | 6              | 4              | 17 | 52 |
| Accumulated other comprehensive income (loss), ending balance                                       | (631)          | (581)          | (631) | (581) |
| Reclassification from AOCI, Current Period, Tax                                                     | 3              | 2              | 9 | 9 |
| Tax (expense) benefit on other comprehensive income (loss)                                          | (3)            | (2)            | (9) | (28) |
| Cumulative foreign currency translation adjustment [Member]                                         |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                      |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                    | (118)          | 8              | (84) | 55 |
| Other comprehensive income (loss), before reclassifications                                         | (24)           | (53)           | (58) | (100) |
| Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit | 0              | 0              | 0 | 0 |
| Other comprehensive income (loss) after tax (expense) benefit                                       | (24)           | (53)           | (58) | (100) |
| Accumulated other comprehensive income (loss), ending balance                                       | (142)          | (45)           | (142) | (45) |
| Reclassification from AOCI, Current Period, Tax                                                     | 0              | 0              | 0 | 0 |
| Tax (expense) benefit on other comprehensive income (loss)                                          | $ 0            | $ 0            | $ 0 | $ 0 |

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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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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.
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Amount after tax, before reclassification adjustments of other comprehensive income (loss).
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Amount after tax of other comprehensive income (loss) attributable to parent entity.
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