3.26.3 html 260 317 1 false 46 0 false 6 false false R1.htm 0000001 - Document - Document and Entity Information Document Sheet http://kinsalecapitalgroup.com/role/DocumentandEntityInformationDocument Document and Entity Information Document Cover 1 false false R2.htm 9952151 - Statement - Consolidated Balance Sheets (Unaudited) Sheet http://kinsalecapitalgroup.com/role/ConsolidatedBalanceSheetsUnaudited Consolidated Balance Sheets (Unaudited) Statements 2 false false R3.htm 9952152 - Statement - Consolidated Balance Sheet (Unaudited) (Parentheticals) Sheet http://kinsalecapitalgroup.com/role/ConsolidatedBalanceSheetUnauditedParentheticals Consolidated Balance Sheet (Unaudited) (Parentheticals) Statements 3 false false R4.htm 9952153 - Statement - Consolidated Statements of Income and Comprehensive Income (Unaudited) Sheet http://kinsalecapitalgroup.com/role/ConsolidatedStatementsofIncomeandComprehensiveIncomeUnaudited Consolidated Statements of Income and Comprehensive Income (Unaudited) Statements 4 false false R5.htm 9952154 - Statement - Consolidated Statements of Changes in Stockholders' Equity (Unaudited) Sheet http://kinsalecapitalgroup.com/role/ConsolidatedStatementsofChangesinStockholdersEquityUnaudited Consolidated Statements of Changes in Stockholders' Equity (Unaudited) Statements 5 false false R6.htm 9952155 - Statement - Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parentheticals) Sheet http://kinsalecapitalgroup.com/role/ConsolidatedStatementsofChangesinStockholdersEquityUnauditedParentheticals Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parentheticals) Statements 6 false false R7.htm 9952156 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) Sheet http://kinsalecapitalgroup.com/role/CondensedConsolidatedStatementsofCashFlowsUnaudited Condensed Consolidated Statements of Cash Flows (Unaudited) Statements 7 false false R8.htm 9952157 - Disclosure - Summary of Significant Accounting Policies Sheet http://kinsalecapitalgroup.com/role/SummaryofSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 8 false false R9.htm 9952158 - Disclosure - Investments Sheet http://kinsalecapitalgroup.com/role/Investments Investments Notes 9 false false R10.htm 9952159 - Disclosure - Fair Value Measurements Sheet http://kinsalecapitalgroup.com/role/FairValueMeasurements Fair Value Measurements Notes 10 false false R11.htm 9952160 - Disclosure - Credit Losses Sheet http://kinsalecapitalgroup.com/role/CreditLosses Credit Losses Notes 11 false false R12.htm 9952161 - Disclosure - Deferred Policy Acquisition Costs Sheet http://kinsalecapitalgroup.com/role/DeferredPolicyAcquisitionCosts Deferred Policy Acquisition Costs Notes 12 false false R13.htm 9952162 - Disclosure - Property and Equipment Sheet http://kinsalecapitalgroup.com/role/PropertyandEquipment Property and Equipment Notes 13 false false R14.htm 9952163 - Disclosure - Underwriting, Acquisition and Insurance Expenses Sheet http://kinsalecapitalgroup.com/role/UnderwritingAcquisitionandInsuranceExpenses Underwriting, Acquisition and Insurance Expenses Notes 14 false false R15.htm 9952164 - Disclosure - Stock-based Compensation Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensation Stock-based Compensation Notes 15 false false R16.htm 9952165 - Disclosure - Earnings Per Share Sheet http://kinsalecapitalgroup.com/role/EarningsPerShare Earnings Per Share Notes 16 false false R17.htm 9952166 - Disclosure - Income Taxes Sheet http://kinsalecapitalgroup.com/role/IncomeTaxes Income Taxes Notes 17 false false R18.htm 9952167 - Disclosure - Reserves for Unpaid Losses and Loss Adjustment Expenses Sheet http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpenses Reserves for Unpaid Losses and Loss Adjustment Expenses Notes 18 false false R19.htm 9952168 - Disclosure - Reinsurance Sheet http://kinsalecapitalgroup.com/role/Reinsurance Reinsurance Notes 19 false false R20.htm 9952169 - Disclosure - Debt Sheet http://kinsalecapitalgroup.com/role/Debt Debt Notes 20 false false R21.htm 9952170 - Disclosure - Other Comprehensive (Loss) Income Sheet http://kinsalecapitalgroup.com/role/OtherComprehensiveLossIncome Other Comprehensive (Loss) Income Notes 21 false false R22.htm 9952171 - Disclosure - Commitment and Contingencies Sheet http://kinsalecapitalgroup.com/role/CommitmentandContingencies Commitment and Contingencies Notes 22 false false R23.htm 9952172 - Disclosure - Segment Reporting Sheet http://kinsalecapitalgroup.com/role/SegmentReporting Segment Reporting Notes 23 false false R24.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 24 false false R25.htm 9955511 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://kinsalecapitalgroup.com/role/SummaryofSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://kinsalecapitalgroup.com/role/SummaryofSignificantAccountingPolicies 25 false false R26.htm 9955512 - Disclosure - Investments (Tables) Sheet http://kinsalecapitalgroup.com/role/InvestmentsTables Investments (Tables) Tables http://kinsalecapitalgroup.com/role/Investments 26 false false R27.htm 9955513 - Disclosure - Fair Value Measurements (Tables) Sheet http://kinsalecapitalgroup.com/role/FairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://kinsalecapitalgroup.com/role/FairValueMeasurements 27 false false R28.htm 9955514 - Disclosure - Credit Losses (Tables) Sheet http://kinsalecapitalgroup.com/role/CreditLossesTables Credit Losses (Tables) Tables http://kinsalecapitalgroup.com/role/CreditLosses 28 false false R29.htm 9955515 - Disclosure - Deferred Policy Acquisition Costs (Tables) Sheet http://kinsalecapitalgroup.com/role/DeferredPolicyAcquisitionCostsTables Deferred Policy Acquisition Costs (Tables) Tables http://kinsalecapitalgroup.com/role/DeferredPolicyAcquisitionCosts 29 false false R30.htm 9955516 - Disclosure - Property and Equipment (Tables) Sheet http://kinsalecapitalgroup.com/role/PropertyandEquipmentTables Property and Equipment (Tables) Tables http://kinsalecapitalgroup.com/role/PropertyandEquipment 30 false false R31.htm 9955517 - Disclosure - Underwriting, Acquisition and Insurance Expenses (Tables) Sheet http://kinsalecapitalgroup.com/role/UnderwritingAcquisitionandInsuranceExpensesTables Underwriting, Acquisition and Insurance Expenses (Tables) Tables http://kinsalecapitalgroup.com/role/UnderwritingAcquisitionandInsuranceExpenses 31 false false R32.htm 9955518 - Disclosure - Stock-based Compensation (Tables) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationTables Stock-based Compensation (Tables) Tables http://kinsalecapitalgroup.com/role/StockbasedCompensation 32 false false R33.htm 9955519 - Disclosure - Earnings Per Share (Tables) Sheet http://kinsalecapitalgroup.com/role/EarningsPerShareTables Earnings Per Share (Tables) Tables http://kinsalecapitalgroup.com/role/EarningsPerShare 33 false false R34.htm 9955520 - Disclosure - Reserves for Unpaid Losses and Loss Adjustment Expenses (Tables) Sheet http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpensesTables Reserves for Unpaid Losses and Loss Adjustment Expenses (Tables) Tables http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpenses 34 false false R35.htm 9955521 - Disclosure - Reinsurance (Tables) Sheet http://kinsalecapitalgroup.com/role/ReinsuranceTables Reinsurance (Tables) Tables http://kinsalecapitalgroup.com/role/Reinsurance 35 false false R36.htm 9955522 - Disclosure - Debt (Tables) Sheet http://kinsalecapitalgroup.com/role/DebtTables Debt (Tables) Tables http://kinsalecapitalgroup.com/role/Debt 36 false false R37.htm 9955523 - Disclosure - Other Comprehensive (Loss) Income (Tables) Sheet http://kinsalecapitalgroup.com/role/OtherComprehensiveLossIncomeTables Other Comprehensive (Loss) Income (Tables) Tables http://kinsalecapitalgroup.com/role/OtherComprehensiveLossIncome 37 false false R38.htm 9955525 - Disclosure - Segment Reporting (Tables) Sheet http://kinsalecapitalgroup.com/role/SegmentReportingTables Segment Reporting (Tables) Tables http://kinsalecapitalgroup.com/role/SegmentReporting 38 false false R39.htm 9955526 - Disclosure - Investments Investments (Available for Sale) (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsInvestmentsAvailableforSaleDetails Investments Investments (Available for Sale) (Details) Details 39 false false R40.htm 9955527 - Disclosure - Investments Available-for-Sale Securities in a Loss Position (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsAvailableforSaleSecuritiesinaLossPositionDetails Investments Available-for-Sale Securities in a Loss Position (Details) Details 40 false false R41.htm 9955528 - Disclosure - Investments Available-for-Sale Securities in a Loss Position Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsAvailableforSaleSecuritiesinaLossPositionNarrativeDetails Investments Available-for-Sale Securities in a Loss Position Narrative (Details) Details 41 false false R42.htm 9955529 - Disclosure - Investments Contractual Maturities of Available-for-Sale Fixed Maturity Securities (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsContractualMaturitiesofAvailableforSaleFixedMaturitySecuritiesDetails Investments Contractual Maturities of Available-for-Sale Fixed Maturity Securities (Details) Details 42 false false R43.htm 9955530 - Disclosure - Investments Net Investment Income (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsNetInvestmentIncomeDetails Investments Net Investment Income (Details) Details 43 false false R44.htm 9955531 - Disclosure - Investments Realized Gains (Losses) (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsRealizedGainsLossesDetails Investments Realized Gains (Losses) (Details) Details 44 false false R45.htm 9955532 - Disclosure - Investments Unrealized Gains (Losses) on Investments (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsUnrealizedGainsLossesonInvestmentsDetails Investments Unrealized Gains (Losses) on Investments (Details) Details 45 false false R46.htm 9955533 - Disclosure - Investments Investment Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/InvestmentsInvestmentNarrativeDetails Investments Investment Narrative (Details) Details 46 false false R47.htm 9955534 - Disclosure - Investments (Details), Real Estate Sheet http://kinsalecapitalgroup.com/role/InvestmentsDetailsRealEstate Investments (Details), Real Estate Details http://kinsalecapitalgroup.com/role/InvestmentsTables 47 false false R48.htm 9955535 - Disclosure - Fair Value Measurements - Fair Value Hierarchy (Details) Sheet http://kinsalecapitalgroup.com/role/FairValueMeasurementsFairValueHierarchyDetails Fair Value Measurements - Fair Value Hierarchy (Details) Details 48 false false R49.htm 9955536 - Disclosure - Fair Value Measures and Disclosures Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/FairValueMeasuresandDisclosuresNarrativeDetails Fair Value Measures and Disclosures Narrative (Details) Details 49 false false R50.htm 9955537 - Disclosure - Credit Losses (Details) Sheet http://kinsalecapitalgroup.com/role/CreditLossesDetails Credit Losses (Details) Details http://kinsalecapitalgroup.com/role/CreditLossesTables 50 false false R51.htm 9955538 - Disclosure - Deferred Policy Acquisition Costs (Details) Sheet http://kinsalecapitalgroup.com/role/DeferredPolicyAcquisitionCostsDetails Deferred Policy Acquisition Costs (Details) Details http://kinsalecapitalgroup.com/role/DeferredPolicyAcquisitionCostsTables 51 false false R52.htm 9955539 - Disclosure - Property and Equipment (Details) Sheet http://kinsalecapitalgroup.com/role/PropertyandEquipmentDetails Property and Equipment (Details) Details http://kinsalecapitalgroup.com/role/PropertyandEquipmentTables 52 false false R53.htm 9955540 - Disclosure - Underwriting, Acquisition and Insurance Expenses (Details) Sheet http://kinsalecapitalgroup.com/role/UnderwritingAcquisitionandInsuranceExpensesDetails Underwriting, Acquisition and Insurance Expenses (Details) Details http://kinsalecapitalgroup.com/role/UnderwritingAcquisitionandInsuranceExpensesTables 53 false false R54.htm 9955541 - Disclosure - Stock-based Compensation Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationNarrativeDetails Stock-based Compensation Narrative (Details) Details 54 false false R55.htm 9955542 - Disclosure - Stock-based Compensation Narrative - Restricted Stock Awards (Details) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationNarrativeRestrictedStockAwardsDetails Stock-based Compensation Narrative - Restricted Stock Awards (Details) Details 55 false false R56.htm 9955543 - Disclosure - Stock-based Compensation Restrictive Stock Awards (Details) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationRestrictiveStockAwardsDetails Stock-based Compensation Restrictive Stock Awards (Details) Details 56 false false R57.htm 9955544 - Disclosure - Stock-based Compensation Narrative - Stock Options (Details) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationNarrativeStockOptionsDetails Stock-based Compensation Narrative - Stock Options (Details) Details 57 false false R58.htm 9955545 - Disclosure - Stock-based Compensation Stock Options (Details) Sheet http://kinsalecapitalgroup.com/role/StockbasedCompensationStockOptionsDetails Stock-based Compensation Stock Options (Details) Details 58 false false R59.htm 9955546 - Disclosure - Earnings Per Share (Details) Sheet http://kinsalecapitalgroup.com/role/EarningsPerShareDetails Earnings Per Share (Details) Details http://kinsalecapitalgroup.com/role/EarningsPerShareTables 59 false false R60.htm 9955547 - Disclosure - Earnings Per Share Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/EarningsPerShareNarrativeDetails Earnings Per Share Narrative (Details) Details 60 false false R61.htm 9955548 - Disclosure - Income Taxes (Details) Sheet http://kinsalecapitalgroup.com/role/IncomeTaxesDetails Income Taxes (Details) Details http://kinsalecapitalgroup.com/role/IncomeTaxes 61 false false R62.htm 9955549 - Disclosure - Reserves for Unpaid Losses and Loss Adjustment Expenses (Details) Sheet http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpensesDetails Reserves for Unpaid Losses and Loss Adjustment Expenses (Details) Details http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpensesTables 62 false false R63.htm 9955550 - Disclosure - Reserves for Unpaid Losses and Loss Adjustment Expenses Narrative (Details) Sheet http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpensesNarrativeDetails Reserves for Unpaid Losses and Loss Adjustment Expenses Narrative (Details) Details http://kinsalecapitalgroup.com/role/ReservesforUnpaidLossesandLossAdjustmentExpensesTables 63 false false R64.htm 9955551 - Disclosure - Reinsurance (Details) Sheet http://kinsalecapitalgroup.com/role/ReinsuranceDetails Reinsurance (Details) Details http://kinsalecapitalgroup.com/role/ReinsuranceTables 64 false false R65.htm 9955552 - Disclosure - Debt (Details) Sheet http://kinsalecapitalgroup.com/role/DebtDetails Debt (Details) Details http://kinsalecapitalgroup.com/role/DebtTables 65 false false R66.htm 9955553 - Disclosure - Other Comprehensive (Loss) Income (Details) Sheet http://kinsalecapitalgroup.com/role/OtherComprehensiveLossIncomeDetails Other Comprehensive (Loss) Income (Details) Details http://kinsalecapitalgroup.com/role/OtherComprehensiveLossIncomeTables 66 false false R67.htm 9955555 - Disclosure - Segment Reporting (Details) Sheet http://kinsalecapitalgroup.com/role/SegmentReportingDetails Segment Reporting (Details) Details http://kinsalecapitalgroup.com/role/SegmentReportingTables 67 false false All Reports Book All Reports knsl-20260930.htm knsl-20260930.xsd knsl-20260930_cal.xml knsl-20260930_def.xml knsl-20260930_lab.xml knsl-20260930_pre.xml http://fasb.org/us-gaap/2026 http://xbrl.sec.gov/dei/2026 http://xbrl.sec.gov/ecd/2026 true true