| **Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 6 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Changes in Accumulated other comprehensive income (loss) [Roll Forward]**                                                        |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                                                   | $ 727          |           | $ 831 |   |
| Other comprehensive income (loss), before reclassifications                                                                        | (610)          |           | (706) |   |
| Amounts reclassified from accumulated other comprehensive income (loss)                                                            | (9)            |           | (1) |   |
| Other comprehensive income (loss), net of tax                                                                                      | (601)          | 103            | (705) | 387 |
| Accumulated other comprehensive income (loss), ending balance                                                                      | 126            |           | 126 |   |
| **Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]**                    |           |           |   |   |
| Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)                                   | 5              |           | 2 |   |
| Tax (expense) benefit on other comprehensive income (loss), tax                                                                    | 316            |           | 341 |   |
| Net unrealized gains (losses) on investments with OTTI losses, tax [Member]                                                        |           |           |   |   |
| **Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]**                    |           |           |   |   |
| Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)                                   |      |           |    |   |
| Tax (expense) benefit on other comprehensive income (loss), tax                                                                    | 4              |           | (3) |   |
| Net unrealized gains (losses) on other investments, tax [Member]                                                                   |           |           |   |   |
| **Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]**                    |           |           |   |   |
| Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)                                   | 3              |           | (3) |   |
| Tax (expense) benefit on other comprehensive income (loss), tax                                                                    | 314            |           | 349 |   |
| Pension and postretirement benefits member, tax [Member]                                                                           |           |           |   |   |
| **Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]**                    |           |           |   |   |
| Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)                                   | 2              |           | 5 |   |
| Tax (expense) benefit on other comprehensive income (loss), tax                                                                    | (2)            |           | (5) |   |
| Cumulative foreign currency translation adjustment, tax [Member]                                                                   |           |           |   |   |
| **Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]**                    |           |           |   |   |
| Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)                                   |      |           |    |   |
| Tax (expense) benefit on other comprehensive income (loss), tax                                                                    |      |           |    |   |
| Net unrealized gains (losses) on investments with OTTI Losses [Member]                                                             |           |           |   |   |
| **Changes in Accumulated other comprehensive income (loss) [Roll Forward]**                                                        |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                                                   | 34             |           | 20 |   |
| Other comprehensive income (loss), before reclassifications                                                                        | (8)            |           | 6 |   |
| Amounts reclassified from accumulated other comprehensive income (loss)                                                            |      |           |    |   |
| Other comprehensive income (loss), net of tax                                                                                      | (8)            |           | 6 |   |
| Accumulated other comprehensive income (loss), ending balance                                                                      | 26             |           | 26 |   |
| Net unrealized gains (losses) on other investments [Member]                                                                        |           |           |   |   |
| **Changes in Accumulated other comprehensive income (loss) [Roll Forward]**                                                        |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                                                   | 1,309          |           | 1,371 |   |
| Other comprehensive income (loss), before reclassifications                                                                        | (589)          |           | (638) |   |
| Amounts reclassified from accumulated other comprehensive income (loss)                                                            | (4)            |           | 9 |   |
| Other comprehensive income (loss), net of tax                                                                                      | (585)          |           | (647) |   |
| Accumulated other comprehensive income (loss), ending balance                                                                      | 724            |           | 724 |   |
| Pension and postretirement benefits [Member]                                                                                       |           |           |   |   |
| **Changes in Accumulated other comprehensive income (loss) [Roll Forward]**                                                        |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                                                   | (716)          |           | (721) |   |
| Other comprehensive income (loss), before reclassifications                                                                        |           |           |    |   |
| Amounts reclassified from accumulated other comprehensive income (loss)                                                            | (5)            |           | (10) |   |
| Other comprehensive income (loss), net of tax                                                                                      | 5              |           | 10 |   |
| Accumulated other comprehensive income (loss), ending balance                                                                      | (711)          |           | (711) |   |
| Cumulative foreign currency translation adjustment [Member]                                                                        |           |           |   |   |
| **Changes in Accumulated other comprehensive income (loss) [Roll Forward]**                                                        |           |           |   |   |
| Accumulated other comprehensive income (loss), beginning balance                                                                   | 100            |           | 161 |   |
| Other comprehensive income (loss), before reclassifications                                                                        | (13)           |           | (74) |   |
| Amounts reclassified from accumulated other comprehensive income (loss)                                                            |      |           |    |   |
| Other comprehensive income (loss), net of tax                                                                                      | (13)           |           | (74) |   |
| Accumulated other comprehensive income (loss), ending balance                                                                      | $ 87           |           | $ 87 |   |

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Tax (expense) benefit on reclassification from accumulated other comprehensive income, current period
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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.
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| - Definition
Net of tax amount of other comprehensive income (loss) attributable to the parent entity.
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Tax effect of other comprehensive income (loss) attributable to parent entity.
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