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Reserve for Property and Casualty Insurance Claims and Claims Expense - Prior year reserve reestimates included in claims and claims expense (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022
Increase (decrease) in claims and claims expense |  |
Prior years | $ (15) | $ 145
Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (25) | 142
Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (20) | (7)
Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 3 | (7)
Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 24 | 19
Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 1 | (3)
Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 2 | 1
Non-catastrophe losses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 27 | 158
Non-catastrophe losses | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 3 | 151
Non-catastrophe losses | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (12) | 4
Non-catastrophe losses | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 10 | (11)
Non-catastrophe losses | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 23 | 20
Non-catastrophe losses | Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 1 | (7)
Non-catastrophe losses | Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 2 | 1
Catastrophe |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (42) | (13)
Catastrophe | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (28) | (9)
Catastrophe | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (8) | (11)
Catastrophe | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (7) | 4
Catastrophe | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 1 | (1)
Catastrophe | Other business lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 0 | 4
Catastrophe | Run-off Property-Liability |  |
Increase (decrease) in claims and claims expense |  |
Prior years | $ 0 | $ 0

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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