<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>408</ContextCount>
  <ElementCount>333</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>96</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>11</UnitCount>
  <MyReports>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>75000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>75010 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>75020 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>75030 - Statement - Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_StatementConsolidatedStatementsOfOperations</Role>
      <ShortName>Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>75040 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>75050 - Statement - Consolidated Statements of Changes in Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/StatementConsolidatedStatementsOfChangesInShareholdersEquity1</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>75060 - Statement - Consolidated Statements of Changes in Shareholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInShareholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>75070 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995455 - Disclosure - Principles of Consolidation and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosurePrinciplesOfConsolidationAndBasisOfPresentation</Role>
      <ShortName>Principles of Consolidation and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Acquisition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureAcquisition</Role>
      <ShortName>Acquisition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995505 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureInvestments</Role>
      <ShortName>Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureAllowanceForExpectedCreditLossesPremiumReceivablesAndReinsuranceReceivables</Role>
      <ShortName>Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Liability for Unpaid Losses and Loss Adjustment Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureLiabilityForUnpaidLossesAndLossAdjustmentExpenses</Role>
      <ShortName>Liability for Unpaid Losses and Loss Adjustment Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareholdersEquity</Role>
      <ShortName>Shareholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureRelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Share-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareBasedCompensationPlans</Role>
      <ShortName>Share-Based Compensation Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995645 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995665 - Disclosure - New Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureNewAccountingPronouncements</Role>
      <ShortName>New Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995685 - Disclosure - Principles of Consolidation and Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosurePrinciplesOfConsolidationAndBasisOfPresentationPolicies</Role>
      <ShortName>Principles of Consolidation and Basis of Presentation (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureNewAccountingPronouncements</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995715 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureInvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureInvestments</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995735 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureFairValueMeasurements</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureAllowanceForExpectedCreditLossesPremiumReceivablesAndReinsuranceReceivablesTables</Role>
      <ShortName>Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureAllowanceForExpectedCreditLossesPremiumReceivablesAndReinsuranceReceivables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Liability for Unpaid Losses and Loss Adjustment Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureLiabilityForUnpaidLossesAndLossAdjustmentExpensesTables</Role>
      <ShortName>Liability for Unpaid Losses and Loss Adjustment Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureLiabilityForUnpaidLossesAndLossAdjustmentExpenses</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Shareholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareholdersEquityTables</Role>
      <ShortName>Shareholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareholdersEquity</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureEarningsPerShare</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSegmentInformation</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995835 - Disclosure - Principles of Consolidation and Basis of Presentation - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosurePrinciplesOfConsolidationAndBasisOfPresentationAdditionalInformationDetail</Role>
      <ShortName>Principles of Consolidation and Basis of Presentation - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995845 - Disclosure - Acquisition - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureAcquisitionAdditionalInformationDetail</Role>
      <ShortName>Acquisition - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995895 - Disclosure - Schedule of Amortized Cost and Estimated Fair Value of Company's Fixed Maturities Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureScheduleOfAmortizedCostAndEstimatedFairValueOfCompanySFixedMaturitiesSecuritiesDetail</Role>
      <ShortName>Schedule of Amortized Cost and Estimated Fair Value of Company's Fixed Maturities Securities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995905 - Disclosure - Schedule of Investments In Equity Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureScheduleOfInvestmentsInEquitySecuritiesDetails</Role>
      <ShortName>Schedule of Investments In Equity Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995915 - Disclosure - Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureInvestmentsAdditionalInformationDetail</Role>
      <ShortName>Investments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995925 - Disclosure - Summary of Amortized Cost and Estimated Fair Value Through Fixed Maturities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummaryOfAmortizedCostAndEstimatedFairValueThroughFixedMaturitiesDetail</Role>
      <ShortName>Summary of Amortized Cost and Estimated Fair Value Through Fixed Maturities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995935 - Disclosure - Summary of Securities with Gross Unrealized Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummaryOfSecuritiesWithGrossUnrealizedLossesDetail</Role>
      <ShortName>Summary of Securities with Gross Unrealized Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995965 - Disclosure - Schedule of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureScheduleOfAccumulatedOtherComprehensiveIncomeLossNetOfTaxDetail</Role>
      <ShortName>Schedule of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995975 - Disclosure - Changes in Accumulated Other Comprehensive Income (Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureChangesInAccumulatedOtherComprehensiveIncomeLossDetail</Role>
      <ShortName>Changes in Accumulated Other Comprehensive Income (Loss) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995985 - Disclosure - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveIncomeLossDetail</Role>
      <ShortName>Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995995 - Disclosure - Components of Net Realized Investment Gains (Losses) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureComponentsOfNetRealizedInvestmentGainsLossesDetail</Role>
      <ShortName>Components of Net Realized Investment Gains (Losses) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>996015 - Disclosure - Summary of Calculation of Realized Gains and Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummaryOfCalculationOfRealizedGainsAndLossesDetail</Role>
      <ShortName>Summary of Calculation of Realized Gains and Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>996025 - Disclosure - Schedule of Proceeds From Sales and Redemptions of Available for Sale Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureScheduleOfProceedsFromSalesAndRedemptionsOfAvailableForSaleSecuritiesDetail</Role>
      <ShortName>Schedule of Proceeds From Sales and Redemptions of Available for Sale Securities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>996035 - Disclosure - Schedule of Investment Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureScheduleOfInvestmentIncomeDetail</Role>
      <ShortName>Schedule of Investment Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>996045 - Disclosure - Schedule of Total Investment Return (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureScheduleOfTotalInvestmentReturnDetail</Role>
      <ShortName>Schedule of Total Investment Return (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>996055 - Disclosure - Summary of Estimated Fair Values of Bonds Held on Deposit (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummaryOfEstimatedFairValuesOfBondsHeldOnDepositDetail</Role>
      <ShortName>Summary of Estimated Fair Values of Bonds Held on Deposit (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>996065 - Disclosure - Summary of Estimated Fair Values of Bonds Held on Deposit (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureSummaryOfEstimatedFairValuesOfBondsHeldOnDepositParentheticalDetail</Role>
      <ShortName>Summary of Estimated Fair Values of Bonds Held on Deposit (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>996105 - Disclosure - Company's Invested Assets Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureCompanysInvestedAssetsMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>Company's Invested Assets Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>996125 - Disclosure - Fair Value Measurements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureFairValueMeasurementsAdditionalInformationDetail</Role>
      <ShortName>Fair Value Measurements - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>996135 - Disclosure - Fair Value and Future Funding Commitments Related to These Investments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureFairValueAndFutureFundingCommitmentsRelatedToTheseInvestmentsDetail</Role>
      <ShortName>Fair Value and Future Funding Commitments Related to These Investments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>996145 - Disclosure - Fair Value and Future Funding Commitments Related to These Investments (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureFairValueAndFutureFundingCommitmentsRelatedToTheseInvestmentsParentheticalDetail</Role>
      <ShortName>Fair Value and Future Funding Commitments Related to These Investments (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>996155 - Disclosure - Goodwill and Intangible Assets - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureGoodwillAndIntangibleAssetsAdditionalInformationDetail</Role>
      <ShortName>Goodwill and Intangible Assets - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>996205 - Disclosure - Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables - Schedule of Allowance for Credit Losses Related to Premium Receivables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureAllowanceForExpectedCreditLossesPremiumReceivablesAndReinsuranceReceivablesScheduleOfAllowanceForCreditLossesRelatedToPremiumReceivablesDetail</Role>
      <ShortName>Allowance for Expected Credit Losses - Premium Receivables and Reinsurance Receivables - Schedule of Allowance for Credit Losses Related to Premium Receivables (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>996215 - Disclosure - Allowance for Expected Credit Losses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureAllowanceForExpectedCreditLossesAdditionalInformationDetail</Role>
      <ShortName>Allowance for Expected Credit Losses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>996225 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureIncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>996235 - Disclosure - Summarized Activity in Liability for Unpaid Losses and Loss Adjustment Expenses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummarizedActivityInLiabilityForUnpaidLossesAndLossAdjustmentExpensesDetail</Role>
      <ShortName>Summarized Activity in Liability for Unpaid Losses and Loss Adjustment Expenses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>996245 - Disclosure - Liability for Unpaid Losses and Loss Adjustment Expenses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureLiabilityForUnpaidLossesAndLossAdjustmentExpensesAdditionalInformationDetail</Role>
      <ShortName>Liability for Unpaid Losses and Loss Adjustment Expenses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>996335 - Disclosure - Shareholders' Equity - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareholdersEquityAdditionalInformationDetail</Role>
      <ShortName>Shareholders' Equity - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>996345 - Disclosure - Information with Respect to Class A Common Shares that were Surrendered or Repurchased (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureInformationWithRespectToClassACommonSharesThatWereSurrenderedOrRepurchasedDetail</Role>
      <ShortName>Information with Respect to Class A Common Shares that were Surrendered or Repurchased (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>996355 - Disclosure - Information with Respect to Class A Common Shares that were Surrendered or Repurchased (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureInformationWithRespectToClassACommonSharesThatWereSurrenderedOrRepurchasedParentheticalDetails</Role>
      <ShortName>Information with Respect to Class A Common Shares that were Surrendered or Repurchased (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>996365 - Disclosure - Schedule of Distributions Declared (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureScheduleOfDistributionsDeclaredDetail</Role>
      <ShortName>Schedule of Distributions Declared (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>996375 - Disclosure - Related Party Transactions - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureRelatedPartyTransactionsAdditionalInformationDetail</Role>
      <ShortName>Related Party Transactions - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>996385 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>996395 - Disclosure - Share-Based Compensation Plans - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureShareBasedCompensationPlansAdditionalInformationDetail</Role>
      <ShortName>Share-Based Compensation Plans - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>996405 - Disclosure - Computation of Basic and Diluted Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureComputationOfBasicAndDilutedEarningsPerShareDetail</Role>
      <ShortName>Computation of Basic and Diluted Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>996415 - Disclosure - Earning Per Share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureEarningPerShareAdditionalInformationDetail</Role>
      <ShortName>Earning Per Share - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>996425 - Disclosure - Segment Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSegmentInformationAdditionalInformationDetail</Role>
      <ShortName>Segment Information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>996435 - Disclosure - Summary of Business Segment Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/Role_DisclosureSummaryOfBusinessSegmentInformationDetail</Role>
      <ShortName>Summary of Business Segment Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>996455 - Disclosure - Supplemental Non-Cash Investing and Financing Activities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureSupplementalNoncashInvestingAndFinancingActivitiesAdditionalInformationDetails</Role>
      <ShortName>Supplemental Non-Cash Investing and Financing Activities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="gbli-20250930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>996465 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.globalindemnity.ie/20250930/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="gbli-20250930.htm">gbli-20250930.htm</File>
    <File>gbli-20250930.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="3">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="1281">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="34">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
