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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
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Increase (decrease) in claims and claims expense |  |
Prior years | $ 8 | $ 12
Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 13 | (54)
Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (7) | 53
Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (6) | 7
Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 6 | 4
Discontinued Lines and Coverages |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 2 | 2
Service Businesses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 0 | 0
Non-catastrophes losses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 28 | (41)
Non-catastrophes losses | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 22 | (53)
Non-catastrophes losses | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 1 | 7
Non-catastrophes losses | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (2) | (2)
Non-catastrophes losses | Commercial lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 5 | 5
Non-catastrophes losses | Discontinued Lines and Coverages |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 2 | 2
Non-catastrophes losses | Service Businesses |  |
Increase (decrease) in claims and claims expense |  |
Prior years | 0 | 0
Catastrophe |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (20) | 53
Catastrophe | Auto |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (9) | (1)
Catastrophe | Homeowners |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (8) | 46
Reinstatement reinsurance premiums |  | 15
Catastrophe | Other personal lines |  |
Increase (decrease) in claims and claims expense |  |
Prior years | (4) | 9
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 Prior Year Claims and Claims Adjustment Expense, Reinstatement Reinsurance Premiums + References No definition available. + Details
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Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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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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