|**Reinsurance (Tables)**                               | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
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|**Reinsurance Disclosures [Abstract]**                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Property Casualty Insurance Assumed And Ceded Business | The table below summarizes our consolidated property casualty insurance net written premiums, earned premiums and incurred loss and loss expenses:(Dollars in millions)Three months ended June 30,Six months ended June 30,2024202320242023Direct written premiums$2,362$2,071$4,487$3,930Assumed written premiums236194475438Ceded written premiums(139)(115)(255)(199)Net written premiums$2,459$2,150$4,707$4,169Direct earned premiums$2,015$1,806$3,949$3,566Assumed earned premiums155134307293Ceded earned premiums(95)(77)(189)(155)Earned premiums$2,075$1,863$4,067$3,704Direct incurred loss and loss expenses$1,352$1,265$2,545$2,564Assumed incurred loss and loss expenses6358139134Ceded incurred loss and loss expenses(3)(61)(2)(119)Incurred loss and loss expenses$1,412$1,262$2,682$2,579
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|(Dollars in millions)                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Direct written premiums                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Assumed written premiums                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Ceded written premiums                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Net written premiums                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Direct earned premiums                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Assumed earned premiums                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Ceded earned premiums                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Earned premiums                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Direct incurred loss and loss expenses                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Assumed incurred loss and loss expenses                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Ceded incurred loss and loss expenses                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Incurred loss and loss expenses                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Life Insurance Assumed and Ceded Business              | The table below summarizes our consolidated life insurance earned premiums and contract holders' benefits incurred:(Dollars in millions)Three months ended June 30,Six months ended June 30,2024202320242023Direct earned premiums$101$100$200$196Ceded earned premiums(20)(20)(40)(39)Earned premiums$81$80$160$157Direct contract holders' benefits incurred$76$100$170$197Ceded contract holders' benefits incurred(8)(22)(23)(38)Contract holders' benefits incurred$68$78$147$159                                                                                                                                                                                                                                                                                                                       
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|(Dollars in millions)                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Direct earned premiums                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Ceded earned premiums                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Earned premiums                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Direct contract holders' benefits incurred             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|Ceded contract holders' benefits incurred              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Contract holders' benefits incurred                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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