|**Life Policy And Investment Contract Reserves (Tables)**                                                                 | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                     
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|**Liability for Future Policy Benefits [Abstract]**                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                     
|Reserve In Addition To The Account Balance, Based on Expected No-Lapse Guarantee Benefits And Expected Policy Assessments | This table summarizes our life policy and investment contract reserves:(Dollars in millions)At December 31,20182017Life policy reserves:Ordinary/traditional life$1,149$1,080Other4847Subtotal1,1971,127Investment contract reserves:Deferred annuities787835Universal life632601Structured settlements156160Other76Subtotal1,5821,602Total life policy and investment contract reserves$2,779$2,729
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|(Dollars in millions)                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                     
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|Life policy reserves:                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                     
|Ordinary/traditional life                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                     
|Other                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                     
|Subtotal                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                     
|Investment contract reserves:                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                     
|Deferred annuities                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                     
|Universal life                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                     
|Structured settlements                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                     
|Other                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                     
|Subtotal                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                     
|Total life policy and investment contract reserves                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                     
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