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Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Commercial - General Liability - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - General Liability - Commercial $ in Millions | Dec. 31, 2022 USD ($) claim | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
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Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 7,046 |  |  |  |  |  |  |  |  |
IBNR | 2,324 |  |  |  |  |  |  |  |  |
2013 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | 629 | $ 624 | $ 623 | $ 620 | $ 623 | $ 613 | $ 655 | $ 650 | $ 655 | $ 650
IBNR | $ 32 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 33,738 |  |  |  |  |  |  |  |  |
2014 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 676 | 659 | 659 | 658 | 635 | 631 | 654 | 658 | $ 653 |
IBNR | $ 34 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 28,131 |  |  |  |  |  |  |  |  |
2015 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 625 | 617 | 602 | 600 | 589 | 574 | 576 | $ 581 |  |
IBNR | $ 33 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 24,200 |  |  |  |  |  |  |  |  |
2016 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 684 | 683 | 673 | 671 | 667 | 659 | $ 623 |  |  |
IBNR | $ 43 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 24,699 |  |  |  |  |  |  |  |  |
2017 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 652 | 630 | 634 | 632 | 632 | $ 632 |  |  |  |
IBNR | $ 32 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 22,359 |  |  |  |  |  |  |  |  |
2018 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 650 | 639 | 646 | 644 | $ 653 |  |  |  |  |
IBNR | $ 127 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 20,242 |  |  |  |  |  |  |  |  |
2019 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 691 | 682 | 682 | $ 680 |  |  |  |  |  |
IBNR | $ 227 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 19,265 |  |  |  |  |  |  |  |  |
2020 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 726 | 722 | $ 723 |  |  |  |  |  |  |
IBNR | $ 434 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 13,998 |  |  |  |  |  |  |  |  |
2021 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 784 | $ 782 |  |  |  |  |  |  |  |
IBNR | $ 527 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 13,775 |  |  |  |  |  |  |  |  |
2022 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 929 |  |  |  |  |  |  |  |  |
IBNR | $ 835 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 10,572 |  |  |  |  |  |  |  |  |

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