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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 | 6 Months Ended
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Jun. 30, 2020 | Jun. 30, 2019
Increase (decrease) in claims and claims expense |  |
Prior years | $ (3) | $ (74)
Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (41) | (158)
Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 16 | 57
Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (8) | 8
Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 27 | 17
Discontinued Lines and Coverages |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 4 | 5
Service Businesses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (1) | (3)
Non-catastrophes losses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (8) | (130)
Non-catastrophes losses | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (26) | (151)
Non-catastrophes losses | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (3) | 0
Non-catastrophes losses | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (6) | 2
Non-catastrophes losses | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 24 | 17
Non-catastrophes losses | Discontinued Lines and Coverages |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 4 | 5
Non-catastrophes losses | Service Businesses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (1) | (3)
Catastrophe |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 5 | 56
Catastrophe | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (15) | (7)
Catastrophe | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 19 | 57
Catastrophe | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (2) | 6
Catastrophe | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 3 | 0
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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