|**Income Taxes (Tables)**                                                                                                                                                               | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
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|**Income Taxes [Abstract]**                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Reconcilliation between the Company's federal income tax (expense) benefit at statutory rates and the recorded income tax (expense) benefit, excluding taxes on discontinued operations | Tax ReconciliationYears ended December 31(In millions)201120102009Income tax expense at statutory rates$(307)$(389)$(189)Tax benefit from tax exempt income7484119Foreign taxes and credits(3)(25)19Taxes related to domestic affiliate(21)(1)(2)Prior year tax adjustment20——Other tax expense(9)(2)(4)Income tax expense$(246)$(333)$(57)                                                                                                                                                                                                                                                         
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|Years ended December 31                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|(In millions)                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Income tax expense at statutory rates                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Tax benefit from tax exempt income                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Foreign taxes and credits                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Taxes related to domestic affiliate                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Prior year tax adjustment                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Other tax expense                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Income tax expense                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Current and deferred components of the Company's income tax (expense) benefit, excluding taxes on discontinued operations                                                               | Current and Deferred TaxesYears ended December 31(In millions)201120102009Current tax (expense) benefit$(54)$(6)$120Deferred tax expense(192)(327)(177)Total income tax expense$(246)$(333)$(57)                                                                                                                                                                                                                                                                                                                                                                                                    
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|Years ended December 31                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|(In millions)                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Current tax (expense) benefit                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Deferred tax expense                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Total income tax expense                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Significant components of the Company's deferred tax assets and liabilities                                                                                                             | Components of Net Deferred Tax AssetDecember 31(In millions)20112010Deferred Tax Assets:Insurance reserves:Property and casualty claim and claim adjustment expense reserves$419$525Unearned premium reserves142127Receivables7495Employee benefits323258Life settlement contracts6164Investment valuation differences370Net loss and tax credits carried forward2584Other assets159124Gross deferred tax assets1,2061,347Deferred Tax Liabilities:Deferred acquisition costs283284Net unrealized gains508314Other liabilities3782Gross deferred tax liabilities828680Net deferred tax asset$378$667
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|December 31                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|(In millions)                                                                                                                                                                           | 2011                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Deferred Tax Assets:                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Insurance reserves:                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Property and casualty claim and claim adjustment expense reserves                                                                                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Unearned premium reserves                                                                                                                                                               | 142                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Receivables                                                                                                                                                                             | 74                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Employee benefits                                                                                                                                                                       | 323                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Life settlement contracts                                                                                                                                                               | 61                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Investment valuation differences                                                                                                                                                        | 3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Net loss and tax credits carried forward                                                                                                                                                | 25                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Other assets                                                                                                                                                                            | 159                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Gross deferred tax assets                                                                                                                                                               | 1,206                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Deferred Tax Liabilities:                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Deferred acquisition costs                                                                                                                                                              | 283                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Net unrealized gains                                                                                                                                                                    | 508                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Other liabilities                                                                                                                                                                       | 37                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Gross deferred tax liabilities                                                                                                                                                          | 828                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Net deferred tax asset                                                                                                                                                                  | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

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