| **Supplementary Insurance Information (Details) - USD ($) $ in Millions** | 12 Months Ended |
|---------------------------------------------------------------------------|-----------------|
||
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | $ 905           | $ 805 | $ 774 |
| Gross future policy benefits, losses, claims and expense losses           | 10,266          | 9,615 | 8,947 |
| Gross unearned premium                                                    | 3,271           | 2,960 | 2,788 |
| Other policy claims and benefits payable                                  | 53              | 46 | 35 |
| Earned premiums                                                           | 6,482           | 5,980 | 5,604 |
| Investment income, net of expenses                                        | 623             | 589 | 571 |
| Benefits, claims losses and settlement expense                            | 3,936           | 4,134 | 3,638 |
| Amortization of deferred policy acquisition costs                         | 1,197           | 1,106 | 1,034 |
| Underwriting, acquisition and insurance expenses                          | 754             | 723 | 704 |
| Net written premiums                                                      | 6,481           | 5,866 | 5,518 |
| Commercial Insurance                                                      |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 345             | 317 | 311 |
| Gross future policy benefits, losses, claims and expense losses           | 5,007           | 4,881 | 4,569 |
| Gross unearned premium                                                    | 1,857           | 1,714 | 1,665 |
| Earned premiums                                                           | 3,674           | 3,476 | 3,319 |
| Benefits, claims losses and settlement expense                            | 1,940           | 2,336 | 2,030 |
| Amortization of deferred policy acquisition costs                         | 703             | 664 | 631 |
| Underwriting, acquisition and insurance expenses                          | 437             | 415 | 422 |
| Net written premiums                                                      | 3,811           | 3,534 | 3,410 |
| Personal Insurance                                                        |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 145             | 136 | 130 |
| Gross future policy benefits, losses, claims and expense losses           | 814             | 739 | 687 |
| Gross unearned premium                                                    | 850             | 797 | 757 |
| Earned premiums                                                           | 1,542           | 1,463 | 1,404 |
| Benefits, claims losses and settlement expense                            | 992             | 977 | 985 |
| Amortization of deferred policy acquisition costs                         | 276             | 256 | 251 |
| Underwriting, acquisition and insurance expenses                          | 181             | 187 | 164 |
| Net written premiums                                                      | 1,594           | 1,503 | 1,435 |
| Excess and Surplus Lines Insurance                                        |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 33              | 28 | 25 |
| Gross future policy benefits, losses, claims and expense losses           | 577             | 446 | 351 |
| Gross unearned premium                                                    | 207             | 175 | 152 |
| Earned premiums                                                           | 398             | 325 | 278 |
| Benefits, claims losses and settlement expense                            | 250             | 199 | 142 |
| Amortization of deferred policy acquisition costs                         | 63              | 51 | 47 |
| Underwriting, acquisition and insurance expenses                          | 43              | 43 | 38 |
| Net written premiums                                                      | 426             | 348 | 303 |
| Reinsurance assumed and other non segment                                 |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 79              | 61 | 46 |
| Gross future policy benefits, losses, claims and expense losses           | 831             | 611 | 481 |
| Gross unearned premium                                                    | 356             | 273 | 213 |
| Earned premiums                                                           | 570             | 427 | 333 |
| Benefits, claims losses and settlement expense                            | 414             | 325 | 195 |
| Amortization of deferred policy acquisition costs                         | 109             | 86 | 57 |
| Underwriting, acquisition and insurance expenses                          | 55              | 42 | 42 |
| Net written premiums                                                      | 648             | 479 | 368 |
| Property, Liability and Casualty Insurance                                |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 602             | 542 | 512 |
| Gross future policy benefits, losses, claims and expense losses           | 7,229           | 6,677 | 6,088 |
| Gross unearned premium                                                    | 3,270           | 2,959 | 2,787 |
| Earned premiums                                                           | 6,184           | 5,691 | 5,334 |
| Investment income, net of expenses                                        | 457             | 431 | 419 |
| Benefits, claims losses and settlement expense                            | 3,596           | 3,837 | 3,352 |
| Amortization of deferred policy acquisition costs                         | 1,151           | 1,057 | 986 |
| Underwriting, acquisition and insurance expenses                          | 716             | 687 | 666 |
| Net written premiums                                                      | 6,479           | 5,864 | 5,516 |
| Accident and Health Insurance                                             |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Net written premiums                                                      | 2               | 2 | 2 |
| Life Insurance Segment                                                    |            |   |   |
| **Supplementary Insurance Information, by Segment**                       |            |   |   |
| Deferred policy acquisition costs                                         | 303             | 263 | 262 |
| Gross future policy benefits, losses, claims and expense losses           | 3,037           | 2,938 | 2,859 |
| Gross unearned premium                                                    | 1               | 1 | 1 |
| Other policy claims and benefits payable                                  | 53              | 46 | 35 |
| Earned premiums                                                           | 298             | 289 | 270 |
| Investment income, net of expenses                                        | 166             | 158 | 152 |
| Benefits, claims losses and settlement expense                            | 340             | 297 | 286 |
| Amortization of deferred policy acquisition costs                         | 46              | 49 | 48 |
| Underwriting, acquisition and insurance expenses                          | $ 38            | $ 36 | $ 38 |

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Amount of amortization of deferred policy acquisition cost recognized, as disclosed in supplementary insurance information.
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Amount of insurance benefit, claim, loss and settlement expenses incurred, as disclosed in supplementary insurance information.
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Amount of deferred policy acquisition cost capitalized on contract remaining in force, as disclosed in supplementary insurance information.
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Amount of reserve for future policy claim payable and loss expense to be incurred, disclosed in supplementary insurance information.
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| - Definition
Amount of net investment income earned, disclosed in supplementary insurance information.
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Amount of operating expense classified as other, disclosed in supplementary insurance information.
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Amount of claim and benefit payable classified as other, disclosed in supplementary insurance information.
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Amount of premium revenue earned, disclosed in supplementary insurance information.
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Amount, after premiums ceded and assumed, of premium written, disclosed in supplementary insurance information.
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Amount of premium not yet earned, disclosed in supplementary insurance information.
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