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Reserve for Property and Casualty Insurance Claims and Claims Expense - Schedule of Prior Year Reserve Reestimates Included in Claims and Claims Expense (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Increase (decrease) in claims and claims expense |  |  |
Prior years | $ (1,809) | $ (308) | $ 549
Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (1,880) | (364) | 244
Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (16) | (395) | 102
Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 128 | 217 | 19
Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (148) | 166 | 84
Other business lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (45) | 0 | 12
Run-off Property-Liability |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 151 | 68 | 89
Protection Services |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 1 | 0 | (1)
Catastrophe losses |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 0 | (370) | (24)
Catastrophe losses | Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (28) | (36) | (50)
Catastrophe losses | Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 43 | (322) | 36
Catastrophe losses | Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (14) | (7) | (18)
Catastrophe losses | Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (1) | (5) | 8
Catastrophe losses | Other business lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 0 | 0 | 0
Catastrophe losses | Run-off Property-Liability |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 0 | 0 | 0
Catastrophe losses | Protection Services |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 0 | 0 | 0
Nationwide Reinsurance Program |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 60 |  |
2021 Colorado Marshall Fire |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 54 |  |
Non-catastrophe losses |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (1,809) | 62 | 573
Non-catastrophe losses | Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (1,852) | (328) | 294
Non-catastrophe losses | Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (59) | (73) | 66
Non-catastrophe losses | Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 142 | 224 | 37
Non-catastrophe losses | Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (147) | 171 | 76
Non-catastrophe losses | Other business lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | (45) | 0 | 12
Non-catastrophe losses | Run-off Property-Liability |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 151 | 68 | 89
Non-catastrophe losses | Protection Services |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 1 | 0 | (1)
Favorable Severity Development | Personal Auto Injury Coverage |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 1,180 |  |
Favorable Severity Development | Personal Auto Physical Damage Coverage |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | 671 |  |
Annual Reserve Review | Run-off Property-Liability |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | $ 146 | $ 58 | $ 80

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