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Property Casualty Loss And Loss Expenses (Narrative) (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | $ 8,975,000,000 | $ 8,336,000,000 | $ 7,229,000,000 | $ 6,677,000,000
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (215,000,000) | (159,000,000) | (428,000,000) |
Net loss and loss expense reserves for asbestos and environmental claims | $ 98,000,000 | $ 92,000,000 |  |
Percentage of reserves for asbestos and environmental claims | 2.00% | 2.00% |  |
Maximum |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Reinsurance retention | $ 500,000 |  |  |
Life and Health Loss Reserves |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 75,000,000 | $ 64,000,000 | 76,000,000 |
Commercial Insurance |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (123,000,000) | (76,000,000) | (353,000,000) |
Commercial Insurance | Workers' Compensation Line |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 1,036,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (66,000,000) | (63,000,000) | (66,000,000) |
Commercial Insurance | Commercial Property Line |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 525,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (55,000,000) | (44,000,000) | (97,000,000) |
Commercial Insurance | Commercial Casualty Line |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 2,927,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | 15,000,000 | 25,000,000 | (120,000,000) |
Commercial Insurance | Commercial Auto Line |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 811,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable |  | 23,000,000 | (43,000,000) |
Personal Insurance |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (64,000,000) | (61,000,000) | (50,000,000) |
Personal Insurance | Homeowner |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 348,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (53,000,000) | (54,000,000) | (14,000,000) |
Personal Insurance | Personal Auto |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 327,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | (15,000,000) |  | (31,000,000) |
Excess and Surplus Lines Insurance |  |  |  |
Property Casualty Insurance Underwriters |  |  |  |
Certain accident, life and health loss reserves | 875,000,000 |  |  |
Prior year claims and claims adjustments expense, (favorable) and unfavorable | $ (11,000,000) | $ (9,000,000) | $ 7,000,000 |

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