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Reserve for Property and Casualty Insurance Claims and Claims Expense - Schedule of Prior Year Reserve Re-Estimates Included in Claims and Claims Expense (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2024 | Mar. 31, 2023
Increase (decrease) in claims and claims expense |  |
Prior years | $ (151) | $ (15)
Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (74) | (25)
Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (189) | (20)
Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 52 | 3
Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 51 | 24
Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 5 | 1
Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 4 | 2
Catastrophe losses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (162) | (42)
Catastrophe losses | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (7) | (28)
Catastrophe losses | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (149) | (8)
Catastrophe losses | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (3) | (7)
Catastrophe losses | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (3) | 1
Catastrophe losses | Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 0 | 0
Catastrophe losses | Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 0 | 0
Non-catastrophe losses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 11 | 27
Non-catastrophe losses | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (67) | 3
Non-catastrophe losses | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (40) | (12)
Non-catastrophe losses | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 55 | 10
Non-catastrophe losses | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 54 | 23
Non-catastrophe losses | Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 5 | 1
Non-catastrophe losses | Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | $ 4 | $ 2

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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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