After five years through ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Supplemental information Supplemental Cash Flow Information [Abstract] Reserve for losses and loss adjustment expenses Liability for Claims and Claims Adjustment Expense, Property Casualty Liability Number of bank loan participations transferred Number Of Bank Loan Participations Transferred Number Of Bank Loan Participations Transferred Bank loan participations: Bank Loan Participations [Abstract] Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Consolidated Entities [Axis] Consolidated Entities [Axis] Number of equity securities transferred Number Of Equity Securities Transferred Number Of Equity Securities Transferred Assumed Reinsurance Premiums Assumed Reinsurance Premiums [Policy Text Block] Represents disclosure of accounting policy for assumed Reinsurance Premiums. Effective Income Tax Rate Reconciliation, Amount [Abstract] Effective Income Tax Rate Reconciliation, Amount [Abstract] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Total Amount (thousands) Dividends, Common Stock, Cash Security Exchange Name Security Exchange Name Equity securities Equity Securities, FV-NI, Current Direct Direct Premiums Earned SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Table] SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Table] Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Premiums Receivable and Agents' Balances, Net Premiums Receivable, Basis of Accounting, Policy [Policy Text Block] Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period (Loss) Earnings Per Share Earnings Per Share Reconciliation [Abstract] Weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] Entity Address, Country Entity Address, Country Investment, Name [Axis] Investment, Name [Axis] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Number of shares available for grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Issue date Debt Instrument, Issuance Date Change in cash, cash equivalents, and restricted cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Incurred losses and loss adjustment expenses, net of reinsurance Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net Intangible assets Deferred Tax Liabilities, Intangible Assets Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Outstanding losses and loss adjustment expenses assumed from involuntary workers compensation pools Outstanding Losses And Loss Adjustment Expenses Assumed From Involuntary Workers Compensation Pools This element represents amount of outstanding losses and loss adjustment expenses assumed from involuntary workers compensation pools. Additions Amounts Charged to Expense SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense Subsequent Event Type [Domain] Subsequent Event Type [Domain] Amortization of intangible assets Amortization Amortization of intangible assets Amortization of Intangible Assets Contribution to subsidiary Payments Of Contributions To Affiliates Payments Of Contributions To Affiliates Senior debt issuances Senior debt issuance Proceeds from Issuance of Senior Long-term Debt Net deferred tax assets (liabilities) Deferred Tax Assets, Net Dividends received deduction Effective Income Tax Rate Reconciliation, Deduction, Dividends, Amount Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Common share equivalents excluded from calculations of diluted earnings per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Jrg Re Jrg Re [Member] Represents information about JRG Re. Sale of Stock [Axis] Sale of Stock [Axis] Schedule of Reserve for Losses and Loss Adjustment Expenses Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block] Subsequent Events [Abstract] Subsequent Events [Abstract] Bank Holding Company Bank Holding Company [Member] Represents information about Bank Holding Company. Cash Equivalents and Restricted Cash Equivalents Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Fronting and Programs Fronting and Programs [Member] Represents information of Fronting and Programs. Business Acquisition [Axis] Business Acquisition [Axis] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Margin above LIBOR, percentage rate Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate Total gains or losses (realized/unrealized) - Included in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Schedule of Gross Carrying Amounts for Indefinite-Lived Intangible Assets Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Award Type [Domain] Award Type [Domain] Receivables greater than 90 days past due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Local Phone Number Local Phone Number Schedule of Summary of Available-for-Sale Investments Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Non-employee directors Non-employee Directors [Member] Non-employee Directors [Member] Exercisable, end of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Condensed Income Statement [Table] Condensed Income Statement [Table] Intangible Assets, Net Goodwill and Intangible Assets, Policy [Policy Text Block] Schedule of Summary of Available-for-Sale Investments by Contractual Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Unearned premiums Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Unearned Premiums Reserve Preferred Shares – 2021 and 2020: $0.00125 par value; 20,000,000 shares authorized; no shares issued and outstanding Preferred Stock, Value, Issued Required collateral percentage Required Collateral Percentage Required Collateral Percentage Energy Energy [Member] Name of underwriting division. Retained (Deficit) Earnings Retained Earnings Retained Earnings [Member] Other Operating Expenses And Other Expenses [Abstract] Other Operating Expenses And Other Expenses [Abstract] Deferred Policy Acquisition Costs Deferred Policy Acquisition Costs [Text Block] Fixed maturity securities Fixed maturity securities Debt Securities [Member] Fee income Fee Income Represents amount of fee income . Bank loan participations, at fair value Bank loan portfolio aggregate fair value Bank loan participations Fair Value, Option, Loans Held as Assets, Aggregate Fair Value Fair Value, Option, Loans Held as Assets, Aggregate Fair Value Ceded premiums payable Ceded Premiums Payable Distributions from equity method investments Proceeds from Equity Method Investment, Distribution Losses and Loss Adjustment Expenses SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses Equity method investments Deferred Tax Liabilities, Investment in Noncontrolled Affiliates Dividend payable, record date Dividends Payable, Date of Record Fortitude Reinsurance Fortitude Reinsurance [Member] Fortitude Reinsurance Underwriting and other issue expenses Deferred Policy Acquisition Costs Underwriting And Other Issue Expenses Represents deferred policy acquisition costs underwriting and other issue expenses. Amortization of policy acquisition costs SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Amortization of Deferred Policy Acquisition Cost Credit Rating, Standard & Poor's [Axis] Credit Rating, Standard & Poor's [Axis] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Purchases Payment To Acquire Bank Loan Participations Represents payment to acquire Bank loan participations. Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Bermuda BERMUDA Individual Risk Workers' Compensation Individual Risk Workers Compensation [Member] Represents information about individual risk workers compensation. Prior years Reserves for losses and loss adjustment expenses Prior Year Claims and Claims Adjustment Expense Basic (loss) earnings per share (in dollars per share) Basic (in dollars per share) Earnings Per Share, Basic Operating lease costs Operating Lease, Expense Tax-exempt investment income Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Largest reinsurer three Credit Risk Reinsurer Three [Member] Represents information about Credit Risk Reinsurer three. Unvested, beginning of year (in shares) Unvested, end of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number After one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Accident year 2021 Short-Duration Insurance Contract, Accident Year 2021 [Member] Bank loan participations Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables Statutory Matters [Abstract] Statutory Matters [Abstract] Statutory Matters Fair Value Measurement [Domain] Fair Value Measurement [Domain] Acquired Intangible Assets [Line Items] Acquired Intangible Assets [Line Items] 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. Valuation and Qualifying Accounts SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Reinsurance recoverables Reinsurance Recoverables, Gross Net deferred tax assets (liabilities) Deferred Tax Liabilities, Net Ceded Credit Risk, Reinsurer [Axis] Ceded Credit Risk, Reinsurer [Axis] Statutory Matters Statutory Matters [Text Block] The entire disclosure represents information regarding insurance statutory matters. Allowance for credit losses Impaired Financing Receivable, Related Allowance Cash Equivalent Collateral Returned to Trust Cash Equivalent Collateral Returned to Trust Cash Equivalent Collateral Returned to Trust Percentage of Amount Assumed to Net SEC Schedule, 12-17, Insurance Companies, Reinsurance, Premium, Percentage Assumed to Net Entity Voluntary Filers Entity Voluntary Filers Plan Name [Axis] Plan Name [Axis] Statutory net (loss) income Statutory Accounting Practices, Statutory Net Income Amount Quoted Prices in Active Markets for Identical Assets Level 1 Fair Value, Inputs, Level 1 [Member] Ceded Credit Risk [Line Items] Ceded Credit Risk [Line Items] Bank loan participations Bank loan participations Bank Loan Obligations [Member] Goodwill impairment Goodwill, Impairment Loss Other liabilities Other Liabilities Direct Direct Amount Direct Premiums Written Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Entity Small Business Entity Small Business Underwriting loss Underwriting Profit (Loss) Represents the amount related to underwriting profit (loss) during the period. Cash, cash equivalents, restricted cash equivalents, and short-term investments Cash and Cash Equivalents [Member] Residential mortgage-backed Residential Mortgage Backed Fair Value Represents fair value of residential mortgage backed. Accrued compensation expenses Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Due to subsidiaries Due to Related Parties, Noncurrent Schedule of Average Annual Percentage Payouts of Incurred Claims by Age, Net of Reinsurance Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block] Percentage of dividend withholding tax Percentage Of Dividend Withholding Tax Represents percentage of dividend withholding tax. Scenario [Axis] Scenario [Axis] Additional paid-in capital Additional Paid in Capital Liabilities and shareholders’ equity Liabilities and Equity [Abstract] Investment Income [Table] Investment Income [Table] James River Group Senior Debt James River Group Senior Debt [Member] James River Group Senior Debt [Member] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] Other invested assets: Other Investments [Abstract] Equity securities Equity securities net realized and unrealized gains (losses) Equity Securities, FV-NI, Gain (Loss) Entity Interactive Data Current Entity Interactive Data Current 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Four Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Intangible Assets [Roll Forward] Finite-lived Intangible Assets [Roll Forward] Fixed maturity securities, gross realized gains Debt Securities, Available-for-sale, Realized Gain Repayments and redemptions Proceeds From Maturities And Repayments Of Other Invested Assets Represents proceeds from maturities and repayments of other invested assets. Minority interest in partnership Affiliated Entity [Member] Unearned premiums Unearned Premiums Schedule of Deferred Policy Acquisition Costs Deferred Policy Acquisition Costs [Table Text Block] Total deferred tax assets Deferred Tax Assets, Gross Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Total investments available-for-sale, Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Other Operating Expenses and Other Expenses Other Operating Income and Expense [Text Block] Other Operating Expenses SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense Amortization of policy acquisition costs Amortization of policy acquisition costs Deferred Policy Acquisition Costs, Amortization Expense Deferred tax assets, net Deferred Income Tax Assets, Net Exercisable, end of year (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Statutory Accounting Practices, Jurisdiction [Domain] Statutory Accounting Practices, Jurisdiction [Domain] Premiums receivable and agents’ balances Increase (Decrease) in Premiums Receivable Junior Subordinated Debt Junior Subordinated Debt [Member] Contingent Liabilities [Line Items] Contingent Liabilities [Line Items] 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. Equity securities Equity Securities [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] Small Business Small Business [Member] Name of underwriting division. Number of agencies Number of Agencies Number of Agencies Weighted-average remaining contractual life of options outstanding (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract] Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract] Number of issuers with impaired loans Number Of Issuers With Impaired Loans Number Of Issuers With Impaired Loans Largest reinsurer two Credit Risk Reinsurer Two [Member] Represents information about Credit Risk Reinsurer two. Lease liabilities Total operating lease liabilities Operating Lease, Liability Document Transition Report Document Transition Report Common Shares – $0.0002 par value; 200,000,000 shares authorized. 2021 and 2020: 37,373,066 and 30,649,261 shares issued and outstanding, respectively Class A common shares Common Stock, Value, Issued Claims outstanding Cumulative Number of Reported Claims Short-duration Insurance Contract, Cumulative Number of Reported Claims Weighted-average period of unrecognized share based compensation expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Bank loan participations Bank loan participations net realized and unrealized gains (losses) Bank Loan Participations, Net Gain (Loss) Bank Loan Participations, Net Gain (Loss) Unvested, beginning of year (in dollars per share) Unvested, end of year (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items] SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items] Leases Lessee, Operating Leases [Text Block] Dividends payable, per common share Dividends Payable, Amount Per Share Schedule of Carrying Value and Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Commercial mortgage and asset-backed Commercial Mortgage Backed Securities [Member] Summary of Investments - Other than Investments in Related Parties SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Text Block] LPT Trust And Loss Fund Trust LPT Trust And Loss Fund Trust [Member] LPT Trust And Loss Fund Trust Other invested assets Carrying Value Other Investments Commercial Auto Business Commercial Auto Business [Member] Commercial Auto Business Franklin Holdings II (Bermuda) Capital Trust I Franklin Holdings Ii Bermuda Capital Trust I [Member] Represents information about Franklin Holdings II Bermuda Capital Trust I. Common share equivalents (in dollars per share) Common Share Equivalents Earnings Per Share Represents amount of earnings per share of common share equivalents. ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Maturity date of Junior Subordinated Debt, unless accelerated earlier Debt Instrument, Maturity Date Associated Trust Agreement [Domain] Associated Trust Agreement [Domain] Associated Trust Agreement [Domain] Provision to return and amended tax returns Effective Income Tax Rate Reconciliation, Provision to Return And Amended Tax Returns, Amount Effective Income Tax Rate Reconciliation, Provision to Return And Amended Tax Returns, Amount Legal Entity [Axis] Legal Entity [Axis] Number of subsidiaries Number Of Subsidiaries Number Of Subsidiaries Allied Health Allied Health [Member] Name of underwriting division. Year 2 Short-duration Insurance Contracts, Historical Claims Duration, Year Two Class of Stock [Axis] Class of Stock [Axis] Fixed Maturity and Equity Securities Marketable Securities, Policy [Policy Text Block] Number of insurance companies Number Of Insurance Companies This element represents number of insurance companies owned by the entity. Sale of stock, consideration received on transaction Sale of Stock, Consideration Received on Transaction SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract] SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract] Schedule of Other Operating Expenses Schedule of Other Operating Cost and Expense, by Component [Table Text Block] Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period Net reserve for losses and loss adjustment expenses Liability for Unpaid Claims and Claims Adjustment Expense, Net Schedule of Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Entity [Domain] Entity [Domain] Dividend declared per share (in dollars per share) Dividend declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Share based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Direct Written Premiums Revenue Recognition, Premiums Earned, Policy [Policy Text Block] Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] Schedule of Cash Dividends Declared Dividends Declared [Table Text Block] Options Share-based Payment Arrangement, Option [Member] Funds held Funds Held under Reinsurance Agreements, Liability Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Property and equipment Deferred Tax Assets, Property, Plant and Equipment Fixed maturity securities, less than 12 months, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Variable Rate [Axis] Variable Rate [Axis] Segment Information Segment Reporting Disclosure [Text Block] Year 5 Short-duration Insurance Contracts, Historical Claims Duration, Year Five Amount at which shown on Balance Sheet SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Amount Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] After one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Short-term investments and other ​Short Term Investments And Other Realized Gains (Losses), Net ​Short Term Investments And Other Realized Gains (Losses), Net Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Variable Rate [Domain] Variable Rate [Domain] Purchases Payments to Acquire Other Investments Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Excluding Commercial Auto Excluding Commercial Auto [Member] Excluding Commercial Auto [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Funds held Increase (Decrease) in Funds Held under Reinsurance Agreements Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract] Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Additional borrowings Proceeds from Lines of Credit Investment interest rate Investment Interest Rate Reserve for losses and loss adjustment expenses Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Trust common stock Trust Common Stock Represents trust common stock. Excess tax benefits on share based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Amount Deferred interest payment period (in years) Debt Instrument, Deferred Interest Option, Maximum Term Debt Instrument, Deferred Interest Option, Maximum Term Rasier And Aleka Rasier And Aleka [Member] Rasier And Aleka Maximum Maximum [Member] Unaffiliated ceding company two Unaffiliated Ceding Company Two [Member] Name of party. Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Sales Proceeds From Bank Loan Participations Represents cash inflow from sales of bank loan participations. Award Type [Axis] Award Type [Axis] Summary of Lease Maturities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Total shareholders’ equity Balances Balances Shareholders' equity Stockholders' Equity Attributable to Parent City Area Code City Area Code Ceded Ceded Premiums Earned Aggregate intrinsic value of options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value James River Group, Inc. James River Group Inc [Member] Represents information regarding James River Group, Inc. Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Percentage of prepaid reinsurance premiums ceded for 3 largest reinsurers Prepaid Reinsurance Premiums Ceded Percentage Of Total Balance Represents prepaid reinsurance premiums ceded as percentage of total balance. Senior debt repayments Repayments of Senior Debt Deferred policy acquisition costs SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Deferred Policy Acquisition Cost Sports and Entertainment Sports And Entertainment [Member] Name of underwriting division. Changes in operating assets and liabilities Increase (Decrease) in Operating Capital Common share repurchases Common share repurchases Payments for Repurchase of Common Stock Property and equipment, estimated useful lives (in years) Property, Plant and Equipment, Useful Life Shareholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Maximum amount of dividends available without regulatory approval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Investment Income Investment Income, Net Adjustments for New Accounting Pronouncements [Axis] Accounting Standards Update [Axis] Principal amount of Senior Debt Principal amount of Junior Subordinated Debt Debt Instrument, Face Amount Current Current Income Tax Expense (Benefit) SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Table] SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Table] Losses and loss adjustment expenses: Policyholder Benefits and Claims Incurred, Net [Abstract] Indemnity Trust Indemnity Trust [Member] Indemnity Trust U.S. tax benefit on share based compensation expense Share-based Payment Arrangement, Expense, Tax Benefit Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Schedule of Summary of Realized Gains and Losses Realized Gain (Loss) on Investments [Table Text Block] Fair value of shares used in calculation of intrinsic values (in dollars per share) Share Price Maturities Proceeds From Maturities From Bank Loan Participations Represents cash inflow from maturities of bank loan participations. RSUs Restricted Stock Units (RSUs) [Member] Rasier Rasier [Member] Rasier Percentage of dividend distribution tax Percentage Of Dividend Distribution Tax Represents percentage of dividend distribution tax. Maximum matching employer contribution Defined Contribution Plan, Employer Matching Contribution, Percent of Match Total deferred tax liabilities Deferred Tax Liabilities, Gross Business Acquisition [Line Items] Business Acquisition [Line Items] Investment in subsidiaries Equity Method Investments Income Statement [Abstract] Income Statement [Abstract] Entity Registrant Name Entity Registrant Name Asset Class [Domain] Asset Class [Domain] General liability and professional liability treaties General Liability And Professional Liability [Member] General Liability And Professional Liability Policy acquisition costs deferred: Deferred Costs [Abstract] Deductions Amounts Written Off or Disposals SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Schedule of Premiums Written, Premiums Earned, and Losses and Loss Adjustment Expenses Effects of Reinsurance [Table Text Block] Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Contingent Liabilities [Table] Contingent Liabilities [Table] Discloses information about contingent liabilities. Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Total income tax (benefit) expense Income Tax Expense (Benefit) Unsecured Unsecured Debt [Member] Accident year 2017 Short-duration Insurance Contracts, Accident Year 2017 [Member] Net Investment Income SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income Entity Tax Identification Number Entity Tax Identification Number Investment Type [Axis] Investment Type [Axis] Document Fiscal Period Focus Document Fiscal Period Focus Total lease payments Lessee, Operating Lease, Liability, to be Paid Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Amount of credit loss expense that is reinsured Amount Of Credit Loss Expense Reinsured Amount Of Credit Loss Expense Reinsured Share Based Compensation Share-based Payment Arrangement [Policy Text Block] Other income Other Nonoperating Income Fair Value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] Chief Operating Officer Chief Operating Officer [Member] Property, Plant and Equipment, Type [Domain] Long-Lived Tangible Asset [Domain] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Other underwriting expenses of the insurance segments Other Underwriting Expense Equity Securities: Equity Securities, FV-NI [Abstract] Equity Component [Domain] Equity Component [Domain] 2014 Non-Employee Director Incentive Plan Non Employee Director Incentive Plan 2014 [Member] Represents information regarding 2014 Non Employee Director Incentive Plan. Accident years prior to 2019 Short-Duration Insurance Contract, Accident Years Prior to 2019 [Member] Short-Duration Insurance Contract, Accident Years Prior to 2019 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Supplementary Insurance Information SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Disclosure [Text Block] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Table] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Table] Changes in fair values of bank loan participations Bank Loan Participations, Changes in Fair Value Bank Loan Participations, Changes in Fair Value Other income Other Income Reinsurance recoverable on paid losses Reinsurance Recoverable for Paid Claims and Claims Adjustments Fixed maturity securities: Available-for-sale Securities, Debt Maturities [Abstract] Liabilities: Liabilities [Abstract] Vesting of RSUs Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Short-term investments Short-term Investments [Member] Counterparty Name [Domain] Counterparty Name [Domain] 2025 Lessee, Operating Lease, Liability, to be Paid, Year Four Total intangible assets, gross Intangible Assets, Gross (Excluding Goodwill) Dividend distributions to intermediate holding company Dividend Distributions To Intermediate Holding Company Represents dividend distributions to intermediate holding company. Increase to deferred tax asset for additional discount Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense1 Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense1 (Loss) income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Significant Other Observable Inputs Level 2 Fair Value, Inputs, Level 2 [Member] Total expenses Benefits, Losses and Expenses Type of Adoption [Domain] Accounting Standards Update [Domain] Auditor Location Auditor Location James River Capital Trust IV James River Capital Trust Iv [Member] Represents information about James River Capital Trust IV. Fixed maturity securities, fair value Total fair value of unrealized loss position securities Debt Securities, Available-for-sale, Unrealized Loss Position Segment Reporting [Abstract] Segment Reporting [Abstract] Accounting Policies [Table] Accounting Policies [Table] Schedule detailing information related to accounting policies. Fixed maturity securities, available-for-sale, at amortized cost (in dollars) Total fixed maturity securities, Cost or Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Intangible assets, useful life (in years) Weighted- Average Life (Years) Finite-Lived Intangible Asset, Useful Life Payable to insurance companies Increase (Decrease) in Reinsurance Payables Broker two Broker Two [Member] Name of party. Estimates and Assumptions Use of Estimates, Policy [Policy Text Block] Schedule of Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Number of impaired loans Number Of Impaired Loans Represents the number of impaired loans. Net unrealized (losses) gains, net of taxes of $(7,135) in 2021, $6,874 in 2020, and $3,358 in 2019 Other comprehensive (loss) income Other comprehensive (loss) income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Accident years 2018 and prior Short-Duration Insurance Contract, Accident Years 2018 and Prior [Member] Short-Duration Insurance Contract, Accident Years 2018 and Prior LPT Trust LPT Trust [Member] LPT Trust Earned premiums: Premiums Earned, Net [Abstract] Title of 12(b) Security Title of 12(b) Security Legacy Plan Legacy Plan [Member] Legacy Plan Investment, Name [Domain] Investment, Name [Domain] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Title of Individual [Axis] Title of Individual [Axis] Document Type Document Type Product and Service [Domain] Product and Service [Domain] Schedule of Summary of RSU Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Schedule of Reconciliation of Beginning and Ending Reserve Balances for Losses and Loss Adjustment Expenses Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Transition provision expense Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit) Gross investment income Gross Investment Income, Operating Impaired bank loans Impaired Bank Loans [Member] Impaired Bank Loans [Member] Net realized investment gains Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Prepaid reinsurance premiums Prepaid reinsurance premiums ceded Prepaid Reinsurance Premiums Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Equity securities, at cost (in dollars) Equity Securities, FV-NI, Cost Measurement Frequency [Axis] Measurement Frequency [Axis] Reclassification adjustment for investment gains realized in net income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Assumed Policyholder Benefits and Claims Incurred, Assumed Cost or Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Geographical [Axis] Geographical [Axis] Other invested assets Other Investments [Member] JRG Reinsurance Company, Ltd. JRG Reinsurance Company Ltd [Member] Represents reinsurance subsidiary of the entity. Shares issued at a public offering price (in dollars per share) Per share price (in dollars per share) Sale of Stock, Price Per Share Equity securities, gross realized gains Equity Securities, FV-NI, Realized Gain Residential mortgage-backed Residential Mortgage Backed Amortized Cost Represents Amortized Cost of Residential mortgage-backed securities. Subsequent Events Subsequent Events [Text Block] Short-Term Investments Investment, Policy [Policy Text Block] Income tax expense recognized over next six years per year Tax Cuts and Jobs Act, Income Tax Expense (Benefit) Aggregate coverage limit Reinsurance, Aggregate Coverage Limit Reinsurance, Aggregate Coverage Limit Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Other Invested Assets Other Invested Assets [Policy Text Block] Represents disclosure of accounting policy for other invested assets composition and accounting. Vesting period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Related Party Transaction [Line Items] Related Party Transaction [Line Items] Ceded written premiums Ceded Ceded to Other Companies Ceded Premiums Written Less reclassification adjustment: OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, after Tax [Abstract] Income from equity method investments Equity in net (loss) income of subsidiaries Income (Loss) from Equity Method Investments Change in net unearned premiums (Increase) Decrease in Unearned Premiums, Net Other operating expenses Total Other Cost and Expense, Operating Fair Value Measurements Fair Value Disclosures [Text Block] Reserve for Losses and Loss Adjustment Expenses Liability Reserve Estimate, Policy [Policy Text Block] 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Three Available-for-sale Securities Available-for-sale Securities [Member] Dividends payable Dividends Payable Revenues: Revenues [Abstract] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Unaffiliated ceding company three Unaffiliated Ceding Company Three [Member] Unaffiliated Ceding Company Three [Member] Document Period End Date Document Period End Date Bank loan participations, gross realized losses Bank Loan Participations, Gross Realized Loss Represents the gross realized losses on bank loan participations. Accident years 2014 through 2018 Short-duration Insurance Contracts, Accident Years 2014 Through 2018 [Member] Short-duration Insurance Contracts, Accident Years 2014 Through 2018 Direct Policyholder Benefits and Claims Incurred, Direct Consolidated Entities [Domain] Consolidated Entities [Domain] Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Investments Investment [Text Block] Investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Schedule of Property and Equipment, Net Property, Plant and Equipment [Table Text Block] Accrued investment income Accrued Investment Income Receivable Excess and Surplus Lines E&S Excess And Surplus Lines [Member] Represents information regarding excess and surplus lines segment. Net investment income Net Investment Income Net investment income Net Investment Income Environmental Environmental [Member] Name of underwriting division. Net realized gain (loss) on changes in fair value of impaired bank loans Realized Gain Loss On Changes In Fair Value Of Impaired Bank Loans This item represents the Net realized gain (loss) on changes in fair value of impaired bank loans. Percentage of available for sale securities Percentage Of Available For Sale Debt Securities Represents percentage of available for sale debt securities. Percentage of excise tax on reinsurance premiums paid Excise Tax On Reinsurance Premiums Paid Represents excise tax on reinsurance premiums paid. Property and equipment, net Property, Plant and Equipment, Net Total expenses Operating Expenses Loss Fund Trust Loss Fund Trust [Member] Loss Fund Trust Equity Awards Shareholders' Equity and Share-based Payments [Text Block] Schedule of Future Estimated Amortization Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Commitment to investment in limited partnership Commitment to Investment In Limited Partnership Represents commitment to investment in a limited partnership. Restricted cash equivalents Restricted cash equivalents at beginning of year Restricted cash equivalents at end of year Restricted Cash Equivalents Total gains or losses (realized/unrealized) - Included in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Subsidiary note repayments Repayments of Related Party Debt Property and equipment, cost basis Property, Plant and Equipment, Gross Allowance for credit losses Accounts Receivable, Allowance for Credit Loss Changes in fair values of equity securities Equity Securities, FV-NI, Unrealized Gain (Loss) Total revenues Segment revenues Revenues Trademarks Trademarks [Member] Equity method investment transfer Equity Method Investment, Transfer Equity Method Investment, Transfer Minimum required statutory capital and surplus Minimum statutory solvency margin Statutory Accounting Practices, Statutory Capital and Surplus Required Beginning of year (in dollars per share) End of year (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Increase in number of common shares authorized for issuance Share-based Compensation Arrangement by Share-based Payment Award, Increase in Number of Shares Authorized Share-based Compensation Arrangement by Share-based Payment Award, Increase in Number of Shares Authorized Number of available-for-sale securities held in an unrealized loss position Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Commercial mortgage and asset-backed Commercial Mortgage And Asset Backed Fair Value Represents fair value of commercial mortgage and asset backed. Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Public Stock Offering Public Stock Offering [Member] Public Stock Offering Entity Current Reporting Status Entity Current Reporting Status Net written premiums Premiums Written, Net Weighted- Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Agency two Agency Two [Member] Agency Two [Member] Counterparty Name [Axis] Counterparty Name [Axis] Excise taxes paid Excise Taxes Paid Represents excise taxes paid on written premiums assumed from third-party insurers with respect to risks located in the U.S. Excess tax benefits from equity incentive plan transactions Excess Tax Benefit from Share-based Compensation, Operating Activities Dividends Dividends United States United States UNITED STATES Common shares reserved for future issuance Common Stock, Capital Shares Reserved for Future Issuance Leases [Abstract] Leases [Abstract] Income Taxes Income Tax, Policy [Policy Text Block] LIBOR London Interbank Offered Rate (LIBOR) [Member] Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period Gross reserve for losses and loss adjustment expenses Liability for Claims and Claims Adjustment Expense Entity Address, Postal Zip Code Entity Address, Postal Zip Code Diluted (in shares) Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted U.S. income before Federal income taxes Income (Loss) from Continuing Operations before Income Taxes, Domestic Accident year 2019 Short-Duration Insurance Contract, Accident Year 2019 [Member] Allowance for Credit Losses on Reinsurance Balances SEC Schedule, 12-09, Allowance, Reinsurance Recoverable [Member] Junior Subordinated Debt Subordinated Borrowings Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] Commissions Deferred Policy Acquisition Cost, Capitalization Weighted-average common shares outstanding: Weighted Average Number of Shares Outstanding, Basic [Abstract] SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract] SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract] Income tax expense recognized over next six years Tax Cuts and Jobs Act, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Related Party [Domain] Related Party [Domain] Schedule of Summary of Option Activity Share-based Payment Arrangement, Option, Activity [Table Text Block] Schedule of Acquired Finite-Lived Intangible Assets Schedule of Acquired Finite-Lived Intangible Assets by Major Class [Table Text Block] Interest rate, per annum Debt Instrument, Basis Spread on Variable Rate Accident year 2018 Short-duration Insurance Contracts, Accident Year 2018 [Member] Total incurred losses and loss and adjustment expenses Incurred Losses and Loss Adj Expenses Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Loans from issuer experiencing liquidity concerns Loans from Issuer Experiencing Liquidity Concerns [Member] Loans from Issuer Experiencing Liquidity Concerns [Member] Accrued expenses Accrued Liabilities Ceded Credit Risk [Table] Ceded Credit Risk [Table] Investment expense Investment Income, Investment Expense Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Investment in variable interest entities Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Accident years 2016 and 2017 Short-duration Insurance Contracts, Accident Years 2016 and 2017 [Member] Short-duration Insurance Contracts, Accident Years 2016 and 2017 [Member] Short-term investments Other Short-term Investments Credit Facility [Axis] Credit Facility [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Entity Address, Address Line Three Entity Address, Address Line Three Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Other operating expenses of the Corporate and Other segment  Other operating expenses of the Corporate and Other segment Other Operating Expenses Of Corporate And Other Segment Represents Other operating expenses of the Corporate and Other segment. Entity Shell Company Entity Shell Company Deferred policy acquisition costs Balance at beginning of period Balance at end of period Deferred Policy Acquisition Cost James River Capital Trust II James River Capital Trust II [Member] Represents information about James River Capital Trust II. Assumed Assumed from Other Companies Assumed Premiums Written Ceded Policyholder Benefits and Claims Incurred, Ceded Number of equity securities held Number Of Equity Securities Held Number Of Equity Securities Held Investments on deposit with state insurance departments Fair Value of Investments on Deposits with State Insurance Departments Fair Value of Investments on Deposits with State Insurance Departments Average recorded investment in impaired bank loans Impaired Financing Receivable, Average Recorded Investment Sales Proceeds from Sale of Equity Securities, FV-NI Current Fiscal Year End Date Current Fiscal Year End Date Bank Loan Participations Fair Value, Option, Loans Held as Assets, Aggregate Fair Value, Policy [Policy Text Block] Fair Value, Option, Loans Held as Assets, Aggregate Fair Value, Policy Third-party Reinsureds Third-party Reinsureds [Member] Third-party Reinsureds ASU 2019-05 Accounting Standards Update 2019-05 [Member] Statement [Table] Statement [Table] Change in restricted cash equivalents Increase (Decrease) In Restricted Cash Equivalents Increase (Decrease) In Restricted Cash Equivalents Year 6 Short-duration Insurance Contracts, Historical Claims Duration, Year Six Total loss and loss adjustment expense payments Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Short-duration Insurance Contracts, Historical Claims Duration [Line Items] Short-duration Insurance Contracts, Historical Claims Duration [Line Items] Schedule of Major Categories of the Company' s Net Investment Income Investment Income [Table Text Block] Adopted Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Other Deferred Tax Assets, Other Supplementary Information Concerning Property Casualty Insurance Operations SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Text Block] Unrecognized share based compensation expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Statistical Measurement [Axis] Statistical Measurement [Axis] Medical Professionals Medical Professionals [Member] Name of underwriting division. Crediting rate on funds withheld Crediting Rate On Funds Withheld Crediting Rate On Funds Withheld Year 4 Short-duration Insurance Contracts, Historical Claims Duration, Year Four Subsequent Event Subsequent Event [Member] Total Finite-Lived Intangible Assets, Net Goodwill Segment goodwill Goodwill Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fixed maturity securities, less than 12 months, gross unrealized losses Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Operating Lease, Liability, Statement of Financial Position [Extensible List] Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration] Scenario [Domain] Scenario [Domain] Amortization of discount Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Amortization of Discount Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Amortization of Discount Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities: Adjustments to reconcile net (loss) income to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Reinsurance and Adjustable Features of Insurance and Reinsurance Contracts Reinsurance Accounting Policy [Policy Text Block] Equity in undistributed earnings of subsidiaries Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Operating costs under lease Operating Lease, Cost Other Related Party Transactions Related Party Transactions Disclosure [Text Block] Net Investment Income [Line Items] Net Investment Income [Line Items] Fixed maturity securities, 12 months or more, gross unrealized losses Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Deferred Deferred U.S. federal income tax benefit Deferred Income Tax Expense (Benefit) Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Short-term investments and other, gross realized gains Short Term Investments And Other Gross Realized Gains Represents the gross profit realized on the sale of short term investment and other. (Loss) Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Number of brokers Number of Brokers Number of Brokers Net (loss) income Net (loss) income Net (Loss) Income (Numerator) Net Income (Loss) Attributable to Parent Right-of-use assets Operating Lease, Right-of-Use Asset Net investment income SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Net Investment Income Net operating loss carryforward Deferred Tax Assets, Operating Loss Carryforwards Accident year 2015 Short-duration Insurance Contracts, Accident Year 2015 [Member] Short-term investments and other, gross realized losses Short Term Investments And Other Gross Realized Losses Represents the gross loss realized on the sale of short term investment and other. SCHEDULE II - Condensed Financial Information of Registrant Condensed Financial Information of Parent Company Only Disclosure [Text Block] Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Statistical Measurement [Domain] Statistical Measurement [Domain] BBB- or better Standard & Poor's, BBB- or Better Rating [Member] Standard & Poor's, BBB- or Better Rating Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Commercial Auto Commercial Auto [Member] Commercial Auto [Member] Issuance of common shares related to outstanding equity plan awards (in shares) Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture Impairment of intangible assets Impairment Losses Impairment of Intangible Assets (Excluding Goodwill) Number of underwriting divisions Number Of Underwriting Divisions Represents number of underwriting divisions. Net Written Premiums SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Written Segments [Axis] Segments [Axis] Deferred Policy Acquisition Costs Deferred Policy Acquisition Costs, Policy [Policy Text Block] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Entity File Number Entity File Number Debt redemption percentage Debt Instrument, Redemption Price, Percentage Specialty Admitted Insurance Specialty Admitted Insurance [Member] Represents information regarding specialty admitted insurance. Compensation expense under share incentive plans APIC, Share-based Payment Arrangement, Increase for Cost Recognition Total principal balance received Proceeds from Sale and Maturity of Other Investments Schedule of Junior Subordinated Debt Schedule of Subordinated Borrowing [Table Text Block] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Schedule of Gross Unrealized Losses and Fair Value for Available-for-Sale Securities Debt Securities, Available-for-sale [Table Text Block] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Other invested assets Other Security Investments [Member] Limited partnerships Partnership Interest [Member] Private Placement Private Placement [Member] Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Total fair value of shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Unrealized (losses) gains arising during the period, net of U.S. income taxes OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Title of Individual [Domain] Title of Individual [Domain] Maturities and calls Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Net unrealized gains (losses), taxes OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Cumulative paid losses and loss adjustment expenses, net of reinsurance Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net James River Capital Trust I James River Capital Trust I [Member] Represents information about James River Capital Trust I. Credit Facility [Domain] Credit Facility [Domain] Assets Assets Assets [Abstract] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Subsegments [Axis] Subsegments [Axis] Accumulated goodwill impairment losses Goodwill, Impaired, Accumulated Impairment Loss Ceded Credit Risk, Reinsurer [Domain] Ceded Credit Risk, Reinsurer [Domain] State and municipal US States and Political Subdivisions Debt Securities [Member] Junior Subordinated Debt [Axis] Junior Subordinated Debt [Axis] Represents information by junior subordinated debt types. Indemnity Trust And Loss Fund Trust Indemnity Trust And Loss Fund Trust [Member] Indemnity Trust And Loss Fund Trust Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Property and Equipment, Net Property, Plant and Equipment, Policy [Policy Text Block] Issuances of common shares under equity incentive plans Issuances of common shares under equity incentive plans Proceeds, Issuance of Shares, Share-based Payment Arrangement, Including Option Exercised SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] Net unrealized gains Deferred Tax Liabilities, Other Comprehensive Income Share-based compensation arrangement by share-based payment award, options, outstanding Beginning of year (in shares) End of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Deferred policy acquisition costs Deferred Tax Liabilities, Deferred Expense, Deferred Policy Acquisition Cost Reserve for losses and loss adjustment expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Loss Reserves Reinsurance Disclosures [Abstract] Reinsurance Disclosures [Abstract] Financial Asset, Period Past Due [Domain] Financial Asset, Aging [Domain] Subsidiary note issuance Proceeds from Related Party Debt Commitments and Contingent Liabilities Commitments and Contingencies Disclosure [Text Block] Related Party [Axis] Related Party [Axis] Secured Secured Debt [Member] Deferred policy acquisition costs Deferred Policy Acquisition Cost1 Represents costs related to successful acquisition of insurance that are deferred. Reinsurance Policy [Domain] Reinsurance Policy [Domain] Reinsurance Policy, Type [Axis] Reinsurance Policy, Type [Axis] Schedule of Deferred Tax Assets (Liabilities) at the Current Prevailing Corporate Income Tax Rate Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Loss before equity in net income of subsidiaries Income (Loss) From Continuing Operations Before Equity In Net Earnings Of Subsidiaries Income (Loss) From Continuing Operations Before Equity In Net Earnings Of Subsidiaries Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Equity securities, at fair value (cost: 2021 – $95,783; 2020 – $81,698) Equity securities Equity Securities, FV-NI Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] U.S. Treasury securities and obligations guaranteed by the U.S. government US Treasury and Government [Member] 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three Net Earned Premiums SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Purchases Payments to Acquire Equity Securities, FV-NI Allowance for Credit Losses on Premiums Receivable and Agents' Balances SEC Schedule, 12-09, Allowance, Credit Loss [Member] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] Broker one Broker One [Member] Name of party. Due from subsidiaries Due from Related Parties Expense associated with Savings Plans Defined Contribution Plan, Cost Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Dividend Restrictions Dividend Payment Restrictions [Text Block] Percentage of dividend withholding tax for distributions Percentage Of Dividend Withholding Tax For Distributions Represents the percentage of dividend withholding tax for distributions. Assets deposited for securing letters of credit Assets Deposited For Securing Letters Of Credit Represents amount of assets deposited for securing letters of credit. Maximum number of shares available for issuance Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized All outstanding losses and loss adjustment expenses prior to 2012, net of reinsurance Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented Preferred stock, dividend rate, percentage Preferred Stock, Dividend Rate, Percentage Unearned premiums Increase (Decrease) in Unearned Premiums Reinsurance recoverable on unpaid losses, net Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Liability for Claims and Claims Adjustment Expense [Abstract] Liability for Claims and Claims Adjustment Expense [Abstract] Statutory Accounting Practices [Line Items] Statutory Accounting Practices [Line Items] Federal income tax (benefit) expense Federal Income Tax Expense (Benefit), Continuing Operations Credit loss expense Accounts Receivable, Credit Loss Expense (Reversal) 2013 Facility 2013 Facility 2013 Facility [Member] 2013 Facility Claims Development [Line Items] Claims Development [Line Items] Reserve for Losses and Loss Adjustment Expenses SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense Accident years 2018 and 2019 Short-Duration Insurance Contract, Accident Years 2018 and 2019 [Member] Short-Duration Insurance Contract, Accident Years 2018 and 2019 Income tax (benefit) expense: Income Tax Expense (Benefit), Continuing Operations [Abstract] Liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Total liabilities and shareholders’ equity Liabilities and Equity Bank holding companies Bank Holding Companies [Member] Name of the investment category. Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Premiums receivable and agents’ balances, net Premiums and Other Receivables, Net 2026 Lessee, Operating Lease, Liability, to be Paid, Year Five Available-for-sale securities, change in gross unrealized gains (losses) OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Aleka Aleka [Member] Aleka Excess Casualty Excess Casualty [Member] Name of underwriting division. Schedule Of Acquired Intangible Assets [Table] Schedule Of Acquired Intangible Assets [Table] Represents the tabular information related to intangible assets acquired in the acquisition. Total amount deposited in trust accounts Assets Held-in-trust Operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Available-for-sale fixed maturity securities and equity securities Securities (Assets) [Member] Expenses: Operating Expenses [Abstract] Ownership percentage Equity Method Investment, Ownership Percentage Total outstanding losses and loss adjustment expenses, net of reinsurance Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net Schedule of Statutory Accounting Statutory Accounting Practices Disclosure [Table Text Block] Minimum Minimum [Member] Other Increase (Decrease) in Other Operating Assets and Liabilities, Net SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract] 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two Senior debt Amount outstanding on line of credit Long-term Line of Credit Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Preferred stock, shares authorized (in shares) Undesignated preferred stock, shares authorized Preferred Stock, Shares Authorized Losses and loss adjustment expenses Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability After ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fixed maturity securities, 12 months or more, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Percentage of outstanding shares acquired Business Acquisition, Percentage of Voting Interests Acquired Issuance of common shares Stock Issued During Period, Value, New Issues Net change Deferred Policy Acquisition Costs, Period Increase (Decrease) Manufacturers and Contractors Manufacturers And Contractors [Member] Name of underwriting division. Senior Debt Debt Disclosure [Text Block] Significant Unobservable Inputs Level 3 Fair Value, Inputs, Level 3 [Member] Leases Lessee, Leases [Policy Text Block] Issuance of common shares (in shares) Stock Issued During Period, Shares, New Issues Number of reportable segments Number of Reportable Segments Unearned premiums SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Unearned Premium Letters of credit outstanding Amount of letters of credit issued Letters of Credit Outstanding, Amount Allowance for Credit Losses on Bank Loans SEC Schedule, 12-09, Allowance, Loss on Finance Receivable [Member] Reinsurance Reinsurance [Text Block] Basis of Presentation and Principles of Consolidation Basis of Accounting, Policy [Policy Text Block] Year 1 Short-duration Insurance Contracts, Historical Claims Duration, Year One Commitments and contingent liabilities Commitments and Contingencies Subsequent Event [Table] Subsequent Event [Table] Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Emerging Growth Company Entity Emerging Growth Company Employee Benefits Compensation and Employee Benefit Plans [Text Block] Debt issue costs paid Payments of Debt Issuance Costs Restricted stock unit dividend equivalents Restricted Stock Unit Dividend Equivalents Represents amount of dividend equivalent of RSU's. Year 3 Short-duration Insurance Contracts, Historical Claims Duration, Year Three Fixed maturity securities, available-for-sale: Debt Securities [Abstract] ASU 2016-13 Accounting Standards Update 2016-13 [Member] Auditor Name Auditor Name Cover [Abstract] Cover [Abstract] Schedule of Other Invested Assets Other Invested Asset [Table Text Block] Tabular disclosure of other invested assets consisting of private debt and equity investments. Adjusted Balance Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Accident years prior to 2018 Short-Duration Insurance Contract, Accident Years Prior to 2018 [Member] Short-Duration Insurance Contract, Accident Years Prior to 2018 [Member] Letters of credit facility, amount Letter Of Credit Facility Amount Represents amount of letter of credit facility. U.S. income taxes OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Written premiums: Premiums Written, Net [Abstract] Life Sciences Life Sciences [Member] Name of underwriting division. Financial Instrument [Axis] Financial Instrument [Axis] Dividend limitations percentage of statutory surplus Dividend Limitations Percentage Of Statutory Surplus Represents dividend limitations percentage of statutory surplus. Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Dividends paid Payments of Dividends Casualty Reinsurance Casualty Reinsurance [Member] Represents information regarding casualty reinsurance. Gross written premiums percentage Gross Written Premiums Percentage Represents gross written premiums percentage. Carrying Value Reported Value Measurement [Member] Junior Subordinated Debt [Domain] Junior Subordinated Debt [Domain] Represents categorization of information by junior subordinated debt. Common Shares Common stock Common Stock [Member] Unpaid principal on impaired loans Impaired Financing Receivable, Unpaid Principal Balance Deduct: Loss and loss adjustment expense payments net of reinsurance: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Payments for reinsurance Payments for Reinsurance Professional Liability Professional Liability [Member] Name of underwriting division. Financial Asset, Period Past Due [Axis] Financial Asset, Aging [Axis] Total investments available-for-sale, Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax 2023 Finite-Lived Intangible Asset, Expected Amortization, Year Two Largest reinsurer one Credit Risk Reinsurer One [Member] Represents information about credit risk reinsurer one. Fixed maturity securities Debt Securities, Available-for-sale, Realized Gain (Loss) Number of credit facilities Number Of Letter Credit Facilities Number Of Letter Credit Facilities Share based compensation expense Share-based Payment Arrangement, Noncash Expense Cash and cash equivalents Cash and cash equivalents at beginning of year Cash and cash equivalents at end of year Cash and Cash Equivalents, at Carrying Value Related party transaction, amounts of transaction Related Party Transaction, Amounts of Transaction Combined ECR Combined Enhanced Capital Requirement Combined Enhanced Capital Requirement Purchases Payments to Acquire Debt Securities, Available-for-sale Audit Information [Abstract] Audit Information [Abstract] Schedule of Incurred But Not Reported Liabilities and Claims Frequency Schedule Of Incurred But Not Reported Liabilities And Claims Frequency [Table Text Block] Represents information of incurred but not reported Liabilities and claims frequency. Debt Security Category [Axis] Debt Security Category [Axis] Deferred Policy Acquisition Costs SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Short-duration Insurance Contracts, Accident Year [Domain] Short-duration Insurance Contracts, Accident Year [Domain] Notes payable to subsidiary Notes Payable, Related Parties, Noncurrent U.S. income taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Total liabilities Liabilities derecognized Liabilities Contractual life of option (in years) Share Based Arrangement by Share Based Award Option Contractual Life Share Based Arrangement by Share Based Award Option Contractual Life Securities receivable or payable, net Payments for (Proceeds from) Unsettled Investments, Net Payments for (Proceeds from) Unsettled Investments, Net Net written premiums SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Premium Written Deferred tax assets: Deferred Tax Assets, Net [Abstract] 2022 Finite-Lived Intangible Asset, Expected Amortization, Year One Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period Reinsurance recoverables on unpaid losses (gross of $631,000 allowance for credit losses on reinsurance recoverables) Reinsurance Recoverables on Unpaid Losses, Gross Aggregate intrinsic value of options outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Equity securities: Equity Securities, FV-NI and without Readily Determinable Fair Value [Abstract] Current year Current Year Claims and Claims Adjustment Expense Common stock, shares issued (in shares) Common Stock, Shares, Issued Investment as collateral for outstanding letters of credit Security Owned and Pledged as Collateral, Fair Value Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Letter Of Credit 30 Million Letter Of Credit 30 Million [Member] Letter Of Credit 30 Million Number of bank loan participations held Number Of Bank Loan Participations Held Number Of Bank Loan Participations Held Entity Address, City or Town Entity Address, City or Town Fixed maturity securities, gross realized losses Debt Securities, Available-for-sale, Realized Loss Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Amortization of policy acquisition costs Amortization Of Policy Acquisition Costs Represents amortization of policy acquisition costs. Subordinated Borrowings [Abstract] Subordinated Borrowings [Abstract] Other Comprehensive (Loss) Income Comprehensive Income (Loss) Note [Text Block] Measurement Frequency [Domain] Measurement Frequency [Domain] ASU 2016-02 Accounting Standards Update 2016-02 [Member] Interest expense Interest expense Interest Expense Insurance licenses and authorities Licensing Agreements [Member] Reserve for losses and loss adjustment expenses SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Reserve for Unpaid Claim and Claim Adjustment Expense Amortization of Policy Acquisition Costs SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost Fair value of awards granted Share-based Compensation Arrangement by Share-based Payment Award, Grants, Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Grants, Fair Value Cash provided by operating activities, excluding the reduction in collateral funds Net Cash Provided by (Used in) Operating Activities Excluding Change in Collateral Funds Net Cash Provided by (Used in) Operating Activities Excluding Change in Collateral Funds Retained (deficit) earnings Retained Earnings (Accumulated Deficit) Net earned premiums SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Earned Premium Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Entity Filer Category Entity Filer Category Schedule of Gross Written Premiums by Segment and Underwriting Division Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Net realized and unrealized gains (losses) on investments Net realized and unrealized (gains) losses on investments Total Net realized and unrealized gains (losses) on investments Gain (Loss) on Investments Bank loan portfolio aggregated unpaid principal balance Fair Value, Option, Loans Held as Assets, Aggregate Unpaid Principal Balance Fair Value, Option, Loans Held as Assets, Aggregate Unpaid Principal Balance Commitment to lend Commitment To Lend Represents amount commitment to lend. 2017 Facility 2017 Facility [Member] 2017 Facility Fair Value Estimate of Fair Value Measurement [Member] Principal amount of Trust Preferred Securities Face Value Of Trust Preferred Securities Represents face value of trust preferred securities. Statutory capital and surplus Actual statutory capital and surplus Statutory Accounting Practices, Statutory Capital and Surplus, Balance Year 7 Short-duration Insurance Contracts, Historical Claims Duration, Year Seven Short-term investments Short-term Investments Identifiable intangibles not subject to amortization Indefinite-lived Intangible Assets (Excluding Goodwill) Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Amendment Flag Amendment Flag Equity Components [Axis] Equity Components [Axis] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Accident years prior to 2020 Short-Duration Insurance Contract, Accident Years Prior to 2020 [Member] Short-Duration Insurance Contract, Accident Years Prior to 2020 Sale of Stock [Domain] Sale of Stock [Domain] Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Weighted-Average Common Shares (Denominator) Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Reinsurance balances Increase (Decrease) in Reinsurance Recoverable Add: Incurred losses and loss adjustment expenses net of reinsurance: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Schedule of Summary of Company's Segment Results Schedule of Segment Reporting Information, by Segment [Table Text Block] James River Capital Trust III James River Capital Trust III [Member] Represents information about James River Capital Trust III. Underwriting (loss) profit of operating segments Total underwriting (loss) profit of operating segments Underwriting Profit Loss Of Operating Segments This element represents amount of underwriting Profit (loss) of operating segments. Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Maturities, calls and paydowns Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Product and Service [Axis] Product and Service [Axis] Percentage of reinsurance recoverables on unpaid losses for 3 largest reinsurers Reinsurance Recoverables On Unpaid Losses Percentage Of Total Balance Represents reinsurance recoverables on unpaid losses percentage of total balance. Schedule of Acquired Indefinite-Lived Intangible Assets Schedule of Acquired Indefinite-lived Intangible Assets by Major Class [Table Text Block] Allowance for credit losses on reinsurance recoverables Reinsurance Recoverables on Unpaid Losses, Allowance Preferred stock par value (in dollars per share) Undesignated stock par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Entity Public Float Entity Public Float Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Deferred tax liability Tax Cuts and Jobs Act, Change in Tax Rate, Deferred Tax Liability, Income Tax Benefit General Casualty General Casualty [Member] Name of underwriting division. Reserve for Losses and Loss Adjustment Expenses Liability For Claims And Claims Adjustment Expense [Text Block] The entire disclosure for the liability for claims and claims adjustment expense. Invested assets: Investments [Abstract] Statement [Line Items] Statement [Line Items] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Weighted- Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Total invested assets Investments Unaffiliated ceding company one Unaffiliated Ceding Company One [Member] Name of party. Electronic data processing hardware and software Electronic Data Processing Hardware And Software [Member] Represents information about electronic data processing hardware and software. Payment of federal excise taxes Payment Of Federal Excise Taxes Represents payment of federal excise taxes on intercompany reinsurance transactions. Cost or Amortized Cost SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost Cash equivalent collateral held in trust arrangement Cash Equivalent Collateral Held In Trust Arrangement Cash Equivalent Collateral Held In Trust Arrangement Fixed maturity securities, available-for-sale, at fair value (amortized cost: 2021 – $1,643,865; 2020 – $1,690,890) Fair Value Total, Fair Value Fixed maturity securities, available-for-sale Debt Securities, Available-for-sale Schedule of Incurred and Cumulative Paid Losses and Loss Adjustment Expenses, Net of Reinsurance Short-duration Insurance Contracts, Claims Development [Table Text Block] Accident year 2014 Short-duration Insurance Contracts, Accident Year 2014 [Member] Short-term investments, net Payments for (Proceeds from) Short-term Investments Debt Disclosure [Abstract] Debt Disclosure [Abstract] Broker relationships Broker Relationships [Member] Represents information related to broker relationships. Loss Portfolio Transfer Loss Portfolio Transfer [Member] Loss Portfolio Transfer Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Associated Trust Agreement [Axis] Associated Trust Agreement [Axis] Associated Trust Agreement Options granted Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Asset Class [Axis] Asset Class [Axis] Document Annual Report Document Annual Report Paid losses and loss adjustment expenses, net of reinsurance SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Paid Claim and Claim Adjustment Expense Forecast Forecast [Member] Schedule of Summary of Share Based Compensation Amount of Expense and Related Tax Benefit Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] U.S. state income tax expense State and Local Income Tax Expense (Benefit), Continuing Operations Issuances of common shares - public offering Proceeds from issuance of stock Proceeds from Issuance of Common Stock Total assets Assets derecognized Segment assets Assets Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Plan Name [Domain] Plan Name [Domain] Dividends payable, date to be paid Dividends Payable, Date to be Paid Interest paid Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Geographical [Domain] Geographical [Domain] Parent Company Parent Company [Member] Equity securities, gross realized losses Equity Securities, FV-NI, Realized Loss Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Net earned premiums Premiums Earned, Net Short-duration Insurance Contracts, Accident Year [Axis] Short-duration Insurance Contracts, Accident Year [Axis] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Furniture and equipment Furniture and Fixtures [Member] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Development on prior year loss reserves Development On Prior Year Loss Reserves [Abstract] Subsequent Event [Line Items] Subsequent Event [Line Items] Net Policyholder Benefits and Claims Incurred, Net Corporate and Other Corporate and Other [Member] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (loss) earnings per share (in dollars per share) Diluted (in dollars per share) Earnings Per Share, Diluted Segments [Domain] Segments [Domain] Accident year 2016 Short-duration Insurance Contracts, Accident Year 2016 [Member] Common share equivalents (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Number of unaffiliated ceding companies Number of Unaffiliated Ceding Companies Number of Unaffiliated Ceding Companies U.S. federal income taxes (refunded) paid, net Income Taxes Paid, Net Accounting Standards Update [Extensible List] Accounting Standards Update [Extensible Enumeration] Total comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Intangible assets, net Net Carrying Value Net Carrying Value Intangible Assets, Net (Excluding Goodwill) Loan Participations and Assignments Loan Participations and Assignments [Member] Other comprehensive (losses) income: Other comprehensive (loss) income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Deferred tax liabilities, net Deferred Income Tax Liabilities, Net Schedule of Components of Comprehensive Income (Loss) Comprehensive Income (Loss) [Table Text Block] Accident year 2020 Short-Duration Insurance Contract, Accident Year 2020 [Member] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Corporate Corporate Debt Securities [Member] Schedule of Reconciliation of the Difference Between Federal Income Tax Provision (Benefit) and Expected Tax Provision (Benefit) Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Subsegments [Domain] Subsegments [Domain] Allowance for credit losses Deferred Tax Asset, Tax Deferred Expense, Reserve and Accrual, Accounts Receivable, Allowance for Credit Loss Provision for depreciation and amortization Depreciation, Depletion and Amortization Schedule of Assets Measured at Fair Value on a Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Carrying value of impaired loans Loan And Advances Carrying Value Represents the carrying value of impaired loans. Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Other assets Other Assets Convertible Preferred Stock Convertible Preferred Stock [Member] Common stock, shares outstanding (in shares) Balances (in shares) Balances (in shares) Common Stock, Shares, Outstanding Unearned Premiums SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Unearned Premium Transfers in to Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Schedule of Available-for-Sale Gross Unrealized Gains or Losses Unrealized Gain (Loss) on Investments [Table Text Block] Financial Instruments [Domain] Financial Instruments [Domain] Jurisdiction [Axis] Jurisdiction [Axis] After five years through ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Commercial mortgage and asset-backed Commercial Mortgage And Asset Backed Amortized Cost Represents amortized cost of commercial mortgage and asset-backed. Year 10 Short-duration Insurance Contracts, Historical Claims Duration, Year Ten Vesting of RSUs (in shares) Vesting of RSUs (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Income taxes receivable Income Taxes Receivable Entity Central Index Key Entity Central Index Key Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Agency one Agency One [Member] Name of party. Broker three Broker Three [Member] Broker Three [Member] Deferred Policy Acquisition Costs Disclosures [Abstract] Deferred Policy Acquisition Costs Disclosures [Abstract] Carrying amount of Junior Subordinated Debt net of repurchases Junior Subordinated Notes Changes in fair values of short-term investments and other Short Term Investments And Other, Changes in Fair Value Short Term Investments And Other, Changes in Fair Value Accident year 2012 Short-duration Insurance Contracts, Accident Year 2012 [Member] One year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Losses due to credit-related impairments Bank Loan Participations, Increase (Decrease) in Fair Value, Credit-Related Impairment Bank Loan Participations, Increase (Decrease) in Fair Value, Credit-Related Impairment Short-duration Insurance Contracts, Historical Claims Duration [Table] Short-duration Insurance Contracts, Historical Claims Duration [Table] Property and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Reinsurance premium Reinsurance Premium Reinsurance Premium Residential mortgage-backed Residential Mortgage Backed Securities [Member] Condensed Financial Information Disclosure [Abstract] Condensed Financial Information Disclosure [Abstract] Base Erosion and Anti-Abuse Tax Effective Income Tax Rate Reconciliation, Base Erosion and Anti-Abuse Tax, Amount Effective Income Tax Rate Reconciliation, Base Erosion and Anti-Abuse Tax, Amount Lender Name [Axis] Lender Name [Axis] Debt Instrument [Line Items] Debt Instrument [Line Items] Trading Symbol Trading Symbol Payables to reinsurers Reinsurance Payable SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract] SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract] Policy acquisition costs deferred Policy Acquisition Costs Deferred Represents amount of policy acquisition costs deferred during the period. Other Deferred Tax Liabilities, Other Fixed maturity securities, gross unrealized losses Gross unrealized losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Accident year 2013 Short-duration Insurance Contracts, Accident Year 2013 [Member] Current total capacity Line of Credit Facility, Current Borrowing Capacity Unamortized premium Debt Instrument, Unamortized Premium Line of Credit Facility [Table] Line of Credit Facility [Table] Sales Proceeds from Sale of Debt Securities, Available-for-sale Accident years 2011 through 2016 Short-Duration Insurance Contract, Accident Years 2011 Through 2016 [Member] Short-Duration Insurance Contract, Accident Years 2011 Through 2016 [Member] Consolidated gross written premiums percentage Consolidated Gross Written Premiums Percentage Represents consolidated gross written premiums percentage. Share based compensation expense Share-based Payment Arrangement, Expense Reinsurance Transaction [Axis] Reinsurance Transaction [Axis] Reinsurance Transaction Per share data: Earnings Per Share, Basic and Diluted [Abstract] IBNR Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount Accounting Policies [Line Items] Accounting Policies [Line Items] 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. Payment to effect a loss portfolio transfer reinsurance transaction Payment To Effect a Loss Portfolio Transfer Reinsurance Transaction Payment To Effect a Loss Portfolio Transfer Reinsurance Transaction Investments [Domain] Investments [Domain] Renewable energy LLCs Renewable Energy Llcs [Member] Name of the investment category. Cash, cash equivalents, and restricted cash equivalents at beginning of year Cash, cash equivalents, and restricted cash equivalents at end of year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Number of common shares issued during period (in shares) Sale of Stock, Number of Shares Issued in Transaction Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Year 8 Short-duration Insurance Contracts, Historical Claims Duration, Year Eight Other financing activities Proceeds from (Payments for) Other Financing Activities Gross Carrying Amount Finite-Lived Intangible Assets, Gross Identifiable intangible assets subject to amortization Finite-Lived Intangible Assets, Net [Abstract] Bank loan participations, gross realized gain Bank Loan Participations, Gross Realized Gain Represents the gross realized gains on bank loan participations. Schedule of Gross Carrying Amounts and Accumulated Amortization for Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Unrealized (losses) gains arising during the period, before U.S. income taxes OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment and Tax External Credit Rating, Standard & Poor's [Domain] External Credit Rating, Standard & Poor's [Domain] Short-duration Insurance Contracts, Claims Development [Table] Short-duration Insurance Contracts, Claims Development [Table] Exercise of stock options (in shares) Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Beginning balance Ending balance Fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Equity in other comprehensive (losses) earnings of subsidiaries Other Comprehensive Income (Loss), Net of Tax Recurring basis Fair Value, Recurring Fair Value, Recurring [Member] Maximum amount of dividends and return of capital available Statutory Accounting Practices, Statutory Amount Available for Dividend Payments Capital Stock Stockholders' Equity Note Disclosure [Text Block] Allowance for credit losses written off Accounts Receivable, Allowance for Credit Loss, Writeoff Measurement Basis [Axis] Measurement Basis [Axis] 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Five Auditor Firm ID Auditor Firm ID Year 9 Short-duration Insurance Contracts, Historical Claims Duration, Year Nine Renewable energy notes receivable Renewable Energy Bridge Financing Notes [Member] Name of the investment category. Net cash provided by (used in) investing activities Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Schedule of Underwriting Profit of Operating Segments by Individual Segment and Reconciliation to Consolidated Income Before Taxes Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Change in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Return of capital Proceeds From Other Invested Asset Return Of Capital Represents cash inflow from other invested asset return of capital. Assumed Assumed Premiums Earned Class of Stock [Domain] Class of Stock [Domain] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] Junior subordinated debt Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust Excess Property Excess Property [Member] Name of underwriting division. Total capacity Line of Credit Facility, Maximum Borrowing Capacity 2014 Long Term Incentive Plan Long Term Incentive Plan 2014 [Member] Represents information regarding Long Term Incentive Plan 2014. Gross written premiums Total gross written premiums Premiums Written, Gross Investment in LLC Investment In Llc [Member] Represents investment in LLC`s. Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Minimum liquidity ratio Minimum Liquidity Ratio Represents minimum liquidity ratio required to be maintained. Fair Value SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Fair Value Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Reinsurance SEC Schedule, 12-17, Insurance Companies, Reinsurance [Text Block] Federal income tax (benefit) expense at applicable statutory rates Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Preferred Shares Preferred stock Preferred Stock [Member] After ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Balance at Beginning of Period Balance at End of Period SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Other Income Other Income [Policy Text Block] Represents disclosure of accounting policy for other income composition and revenue recognition policy. Reinsurance Transaction [Domain] Reinsurance Transaction [Domain] Reinsurance Transaction [Domain] One year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Investment in private subordinated notes Other invested assets – notes receivable Notes Receivable Represents carrying value of notes receivable as on reporting date. Unamortized discount Debt Instrument, Unamortized Discount Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Other expenses Other expenses Other Expenses Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year