| **Reinsurance (Tables)**                                                                               | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
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| **Reinsurance Disclosures [Abstract]**                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business                 | Our condensed consolidated statements of income include earned consolidated property casualty insurance premiums on assumed and ceded business: (Dollars in millions)Three months ended March 31, 2016 2015Direct earned premiums$1,119 $1,076Assumed earned premiums15 2Ceded earned premiums(38) (37)Earned premiums$1,096 $1,041                                                                     |
| Incurred Consolidated Property Casualty Insurance Loss And Loss Expenses On Assumed And Ceded Business | Our condensed consolidated statements of income include incurred consolidated property casualty insurance loss and loss expenses on assumed and ceded business:(Dollars in millions)Three months ended March 31, 2016 2015Direct incurred loss and loss expenses$648 $691Assumed incurred loss and loss expenses10 (1)Ceded incurred loss and loss expenses3 (1)Incurred loss and loss expenses$661 $689     |
| Earned Life Insurance Premiums On Ceded Business                                                       | Our condensed consolidated statements of income include earned life insurance premiums on ceded business: (Dollars in millions)Three months ended March 31, 2016 2015Direct earned premiums$71 $65Ceded earned premiums(13) (12)Earned premiums$58 $53                                                                                                                                                  |
| Life Insurance Contract Holders' Benefits Incurred On Ceded Business                                   | Our condensed consolidated statements of income include life insurance contract holders' benefits incurred on ceded business: (Dollars in millions)Three months ended March 31, 2016 2015Direct contract holders' benefits incurred$76 $72Ceded contract holders' benefits incurred(13) (12)Contract holders' benefits incurred$63 $60                                                                  |

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Life Insurance Contract Holders' Benefits Incurred On Ceded Business
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Life insurance premiums earned on assumed and ceded business.
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Property Casualty Insurance Loss And Loss Expenses Incurred On Assumed And Ceded Business
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Tabular disclosure of property casualty insurance premiums earned on assumed and ceded business.
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