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Liabilities for Losses and Loss Expenses - Additional Information (Detail) - USD ($) $ in Thousands | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Increase (Decrease) in liability for losses and loss expenses of prior years | $ (21,564) | $ (10,864)
Percentage of 2010 development | 3.90% | 2.10%

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- Definition Managements assertion of adequacy of insurance reserves percentage. + 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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- 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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