|**Changes in Accumulated Other Comprehensive Income (Loss) by Component (Tables)**                                              | 9 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 lossesNet unrealized gains (losses) on other investmentsPension and postretirement benefitsCumulative foreign currency translation adjustmentTotalBalance at June 30, 2013$26$724$(711)$87$126Other comprehensive income (loss) before reclassifications(4)(68)—56(16)Amounts reclassified from accumulated other comprehensive income (loss) aftertax (expense) benefit of $0, $(2), $3, $0, and $1(1)2(4)—(3)Other comprehensive income (loss) after tax (expense) benefit of $1, $38, $(3), $0, and $36(3)(70)456(13)Balance at September 30, 2013$23$654$(707)$143$113(In millions)Net unrealized gains (losses) on investments with OTTI lossesNet unrealized gains (losses) on other investmentsPension and postretirement benefitsCumulative foreign currency translation adjustmentTotalBalance at January 1, 2013$20$1,371$(721)$161$831Other comprehensive income (loss) before reclassifications2(706)—(18)(722)Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit of $0, $(5), $8, $0, and $3(1)11(14)—(4)Other comprehensive income (loss) after tax (expense) benefit of $(2), $387, $(8), $0, and $3773(717)14(18)(718)Balance at September 30, 2013$23$654$(707)$143$113
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|(In millions)                                                                                                                   | Net unrealized gains (losses) on investments with OTTI losses                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Balance at June 30, 2013                                                                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other comprehensive income (loss) before reclassifications                                                                      | (4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Amounts reclassified from accumulated other comprehensive income (loss) aftertax (expense) benefit of $0, $(2), $3, $0, and $1  | (1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Other comprehensive income (loss) after tax (expense) benefit of $1, $38, $(3), $0, and $36                                     | (3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Balance at September 30, 2013                                                                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|(In millions)                                                                                                                   | Net unrealized gains (losses) on investments with OTTI losses                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Balance at January 1, 2013                                                                                                      | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other comprehensive income (loss) before reclassifications                                                                      | 2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit of $0, $(5), $8, $0, and $3 | (1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Other comprehensive income (loss) after tax (expense) benefit of $(2), $387, $(8), $0, and $377                                 | 3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Balance at September 30, 2013                                                                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

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