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Claim and Claim Adjustment Expense Reserves (Specialty - Net prior year claim and allocated claim adjustment expense reserve development) (Details) - Specialty - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Medical Professional Liability | $ 8 | $ 25 | $ 16 | $ 35
Other Professional Liability and Management Liability | 0 | 0 | 10 | (6)
Surety | (15) | (40) | (53) | (70)
Warranty | (6) | 0 | (14) | (3)
Other | (2) | (1) | 1 | (3)
Total pretax (favorable) unfavorable development | $ (15) | $ (16) | $ (40) | $ (47)

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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Medical Professional Liability + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Other + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Surety + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Warranty + References No definition available. + Details
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- Definition Net prior year claim and allocated claim adjustment expense reserve development, Other Professional Liability and Management Liability + 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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