|**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) for the Combined Continental Casualty Companies are presented in the table below, determined in accordance with accounting practices prescribed or permitted by insurance and/or other regulatory authoritiesStatutory Capital and SurplusStatutory Net Income (Loss)December 31Years ended December 31(In millions)2021(1)20202021(1)20202019Combined Continental Casualty Companies$11,321$10,708$1,253$800$1,062(1) 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)                                                          | 2021(1)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Combined Continental Casualty Companies                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

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