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Reserve for Property and Casualty Insurance Claims and Claims Expense 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 | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2020 | Sep. 30, 2019
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | $ (440) | $ (118)
Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (101) | (311)
Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (440) | 59
Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (66) | 17
Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 29 | 17
Discontinued Lines and Coverages |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 139 | 103
Service Businesses |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (1) | (3)
Non-catastrophe losses |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 62 | (171)
Non-catastrophe losses | Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (60) | (302)
Non-catastrophe losses | Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (19) | 0
Non-catastrophe losses | Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (25) | 13
Non-catastrophe losses | Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 28 | 18
Non-catastrophe losses | Discontinued Lines and Coverages |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 139 | 103
Non-catastrophe losses | Service Businesses |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (1) | (3)
Annual reserve review | Discontinued Lines and Coverages |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 132 |
Catastrophe |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years | $ (495) | (502) | 53
Catastrophe | Auto |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (41) | (9)
Catastrophe | Homeowners |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (421) | 59
Catastrophe | Other personal lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | (41) | 4
Catastrophe | Commercial lines |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 1 | (1)
Catastrophe | Discontinued Lines and Coverages |  |  |
Increase (decrease) in claims and claims expense |  |  |
Prior years |  | 0 | 0
Catastrophe | Service Businesses |  |  |
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 http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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