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Property Casualty Loss and Loss Expenses - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Dec. 31, 2024
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Reserve for loss and loss expenses | $ 11,072 |  | $ 11,072 |  | $ 10,003
Prior accident years | (63) | $ (40) | (154) | $ (140) |
Life Insurance Segment |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Reserve for loss and loss expenses | 71 | 61 | 71 | 61 |
Commercial Insurance |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | (42) | (29) | (85) | (67) |
Commercial Insurance | Commercial Property Line |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | (40) | (21) | (75) | (44) |
Commercial Insurance | Workers' Compensation Line |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | (17) | (28) | (28) | (40) |
Commercial Insurance | Commercial Casualty Line |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years |  | 28 |  | 29 |
Commercial Insurance | Commercial Auto Line |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | 18 |  | 24 | (11) |
Personal Insurance |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | (19) | 6 | (38) | (27) |
Personal Insurance | Personal Auto |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years |  | 12 |  |  |
Personal Insurance | Homeowner |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | (25) |  | (44) | (27) |
Excess and Surplus Lines Insurance |  |  |  |  |
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters |  |  |  |  |
Prior accident years | $ (5) | $ 3 | $ (14) | $ 0 |

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