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Claim and Claim Adjustment Expense Reserves (Commercial - Net prior year claim and allocated claim adjustment expense reserve development) (Details) - Commercial - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Commercial Auto | $ 0 | $ 9 | $ 30 | $ 33
General Liability | 0 | 15 | 0 | 15
Workers' Compensation | 2 | (23) | (40) | (97)
Property and Other | 0 | 0 | 12 | 41
Total pretax (favorable) unfavorable development | $ 2 | $ 1 | $ 2 | $ (8)

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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Commercial Auto + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Net prior year claim and allocated claim adjustment expense reserve development, General Liability + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Property and Other + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Workers' Compensation + References No definition available. + Details
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- Definition Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group + References No definition available. + Details
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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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- Details
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Period Type: |