| **Changes in Accumulated Other Comprehensive Income (Loss) by Component (Tables)**   | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| **Changes in Accumulated Other Comprehensive Income (Loss) by Component [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Changes in Accumulated Other Comprehensive Income (Loss) by Component                | Changes in Accumulated Other Comprehensive Income (Loss)(In millions)Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment TotalBalance at April 1, 2013$34 $1,309 $(716) $100 $727Other comprehensive income (loss) before reclassifications(8) (589) — (13) (610)Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit of $0, $3, $2, $0, and $5— (4) (5) — (9)Other comprehensive income (loss) after tax (expense) benefit of $4, $314, $(2), $0, and $316 (8) (585) 5 (13) (601)Balance at June 30, 2013$26 $724 $(711) $87 $126(In millions)Net unrealized gains (losses) on investments with OTTI losses Net unrealized gains (losses) on other investments Pension and postretirement benefits Cumulative foreign currency translation adjustment TotalBalance at January 1, 2013$20 $1,371 $(721) $161 $831Other comprehensive income (loss) before reclassifications6(638) — (74) (706)Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit of $0, $(3), $5, $0, and $2— 9 (10) — (1)Other comprehensive income (loss) after tax (expense) benefit of $(3), $349, $(5), $0, and $3416 (647) 10 (74) (705)Balance at June 30, 2013$26 $724 $(711) $87 $126 |

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| - Definition
Tabular disclosure of the components of accumulated other comprehensive income (loss).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669686-108580
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