|**Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations**                              | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
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|**Supplemental Information for Property, Casualty Insurance Underwriters [Abstract]**                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations                                  | SCHEDULE VI.  SUPPLEMENTAL INFORMATION CONCERNING PROPERTY AND CASUALTY INSURANCE OPERATIONSAs of and for the years ended December 31Consolidated Property and Casualty Operations(In millions)201120102009Deferred acquisition costs$658$1,079Reserves for unpaid claim and claim adjustment expenses24,22825,412Discount deducted from claim and claim adjustment expense reserves above (based on interest rates ranging from 3.0% to 8.0%)1,5691,552Unearned premiums3,2503,203Net written premiums6,7986,471$6,713Net earned premiums6,6036,5146,720Net investment income1,8452,0972,110Incurred claim and claim adjustment expenses related to current year4,9014,7374,788Incurred claim and claim adjustment expenses related to prior years(429)(545)(241)Amortization of deferred acquisition costs1,4101,3871,417Paid claim and claim adjustment expenses4,4994,6674,841
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|As of and for the years ended December 31                                                                                    | Consolidated Property and Casualty Operations                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|(In millions)                                                                                                                | 2011                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Deferred acquisition costs                                                                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Reserves for unpaid claim and claim adjustment expenses                                                                      | 24,228                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Discount deducted from claim and claim adjustment expense reserves above (based on interest rates ranging from 3.0% to 8.0%) | 1,569                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Unearned premiums                                                                                                            | 3,250                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Net written premiums                                                                                                         | 6,798                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Net earned premiums                                                                                                          | 6,603                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Net investment income                                                                                                        | 1,845                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Incurred claim and claim adjustment expenses related to current year                                                         | 4,901                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Incurred claim and claim adjustment expenses related to prior years                                                          | (429                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Amortization of deferred acquisition costs                                                                                   | 1,410                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Paid claim and claim adjustment expenses                                                                                     | 4,499                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

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