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Claim and Claim Adjustment Expense Reserves - Net Prior Year Development (Detail) - CNA Financial [Member] - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development | $ (115) | $ (132) | $ (227) | $ (282)
Pretax (favorable) unfavorable premium development | (19) | (5) | (2) | (27)
Total pretax (favorable) unfavorable net prior year development | $ (134) | $ (137) | $ (229) | $ (309)

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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 Pretax (favorable) unfavorable net prior year development excluding Life Group. + References No definition available. + Details
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- Definition Pretax (favorable) unfavorable premium 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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