|**Stockholders' Equity and Statutory Accounting Practices (Tables)**   | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|**Stockholders' Equity and Statutory Accounting Practices [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Combined statutory capital and surplus and net income (loss)           | Combined statutory capital and surplus and statutory net income (loss), determined in accordance with accounting practices prescribed or permitted by insurance and/or other regulatory authorities for the Combined Continental Casualty Companies and the life company, are presented in the table below.Statutory Capital and SurplusStatutory Net Income (Loss)December 31Years ended December 31(In millions)2015 (a)20142015 (a)20142013Combined Continental Casualty Companies$10,723$11,155$1,148$914$913Life company3748(a)Information derived from the statutory-basis financial statements to be filed with insurance regulators.
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|                                                                       | Statutory Capital and Surplus                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|                                                                       | December 31                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|(In millions)                                                          | 2015 (a)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Combined Continental Casualty Companies                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Life company                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|(a)                                                                    | Information derived from the statutory-basis financial statements to be filed with insurance regulators.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

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