Investments [Abstract] Schedule of summary of available-for-sale investments Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of summary of available-for-sale investments by contractual maturity Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of gross unrealized losses and fair value for available-for-sale securities Debt Securities, Available-for-sale [Table Text Block] Schedule of summary of realized gains and losses Realized Gain (Loss) on Investments [Table Text Block] Schedule of other invested assets Other Invested Asset [Table Text Block] Tabular disclosure of other invested assets consisting of private debt and equity investments. Accounting Policies [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Estimates and Assumptions Use of Estimates, Policy [Policy Text Block] Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Income Tax Expense Income Tax, Policy [Policy Text Block] Adopted and Prospective Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Earnings Per Share [Abstract] 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] Other Comprehensive Income (Loss), Net of Tax [Abstract] Other Comprehensive (Loss) Income Comprehensive Income (Loss) Note [Text Block] Other Operating Expenses [Abstract] Other Operating Expenses [Abstract] Amortization of policy acquisition costs Deferred Policy Acquisition Costs, Amortization Expense Other underwriting expenses of the operating segments Other Underwriting Expense 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. Total Other Cost and Expense, Operating Liability for Claims and Claims Adjustment Expense [Abstract] Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract] Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) [Abstract] Reserve for losses and loss adjustment expenses net of reinsurance recoverables at beginning of period Liability for Unpaid Claims and Claims Adjustment Expense, Net Add: Incurred losses and loss adjustment expenses net of reinsurance: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Current year Current Year Claims and Claims Adjustment Expense Prior years Prior Year Claims and Claims Adjustment Expense Total incurred losses and loss and adjustment expenses Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Deduct: Loss and loss adjustment expense payments net of reinsurance: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Total loss and loss adjustment expense payments Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Reserve for losses and loss adjustment expenses net of reinsurance recoverables at end of period Add: Reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Reserve for losses and loss adjustment expenses gross of reinsurance recoverables on unpaid losses and loss adjustment expenses at end of period Liability for Claims and Claims Adjustment Expense Segment Reporting [Abstract] Number of reportable segments Number of Reportable Segments Fee income in Excess and Surplus Lines segment Fee Income Represents amount of fee income . Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Excess and Surplus Lines Excess And Surplus Lines [Member] Represents information regarding excess and surplus lines segment. Specialty Admitted Insurance Specialty Admitted Insurance [Member] Represents information regarding specialty admitted insurance. Casualty Reinsurance Casualty Reinsurance [Member] Represents information regarding casualty reinsurance. Corporate and Other Corporate and Other [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Gross written premiums Premiums Written, Gross Net earned premiums Premiums Earned, Net Underwriting profit of insurance segments Underwriting Profit Loss Of Operating Segments This element represents amount of underwriting Profit (loss) of operating segments. Net investment income Net Investment Income Interest expense Interest Expense Segment revenues Revenues Segment goodwill Goodwill Segment assets Assets Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2016-02 Accounting Standards Update 2016-02 [Member] ASU 2019-05 Accounting Standards Update 2019-05 [Member] Accounting Standards Update 2019-05 [Member] ASU 2016-13 Accounting Standards Update 2016-13 [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Shares Common Stock [Member] Preferred Shares Preferred Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance (in shares) Common Stock, Shares, Outstanding Balance Stockholders' Equity Attributable to Parent Net (loss) income Net Income (Loss) Attributable to Parent Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Dividends Dividends Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Vesting of RSUs (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Vesting of RSUs Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Compensation expense under share incentive plans APIC, Share-based Payment Arrangement, Increase for Cost Recognition Cumulative effect of adoption of ASU Cumulative Effect of New Accounting Principle in Period of Adoption Balance (in shares) Balance Fair Value Disclosures [Abstract] Schedule of assets measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Reconciliation of securities measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of assets measured at fair value on a nonrecurring basis Fair Value Measurements, Nonrecurring [Table Text Block] Schedule of carrying value and fair value Fair Value, by Balance Sheet Grouping [Table Text Block] Stockholders' Equity Note [Abstract] Share based compensation expense Share-based Payment Arrangement, Expense U.S. tax benefit on share based compensation expense Share-based Payment Arrangement, Expense, Tax Benefit Total underwriting profit of insurance segments Other operating expenses of the Corporate and Other segment Underwriting (loss) profit Underwriting Profit (Loss) Represents the amount related to underwriting profit (loss) during the period. Net investment income Net realized and unrealized (losses) gains on investments Gain (Loss) on Investments Amortization of intangible assets Amortization of Intangible Assets Other income and expenses Other Income And Expenses Represents other income and expenses. Interest expense (Loss) income before taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Bank holding companies Bank Holding Companies [Member] Name of the investment category. Bank Loan Participations Loan Participations and Assignments [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Bank Holding Company Bank Holding Company [Member] Represents information about Bank Holding Company. Retained Earnings Credit Rating, Standard & Poor's [Axis] Credit Rating, Standard & Poor's [Axis] External Credit Rating, Standard & Poor's [Domain] External Credit Rating, Standard & Poor's [Domain] BBB- or better Standard & Poor's, BBB- or Better Rating [Member] Standard & Poor's, BBB- or Better Rating [Member] Below BBB- Standard & Poor's, Below BBB- Rating [Member] Standard & Poor's, Below BBB- Rating [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Fixed maturity securities Debt Securities [Member] Bank Loan Portfolio Bank Loan Portfolio [Member] Bank Loan Portfolio [Member] Loans from Issuer Experiencing Liquidity Concerns Loans from Issuer Experiencing Liquidity Concerns [Member] Loans from Issuer Experiencing Liquidity Concerns [Member] Gain (Loss) on Securities [Line Items] Gain (Loss) on Securities [Line Items] Number of issuers Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Total fair value Debt Securities, Available-for-sale, Unrealized Loss Position Gross unrealized losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Percentage of available for sale securities Percentage Of Available For Sale Debt Securities Represents percentage of available for sale debt securities. Fixed maturity securities, available-for-sale Debt Securities, Available-for-sale Aggregate net unrealized gain (loss) Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Number of impaired fixed maturities Number of Impaired Fixed Maturity Securities Number of Impaired Fixed Maturity Securities Impairment losses Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale Bank loan participations Financing Receivable, after Allowance for Credit Loss Cumulative effect of adoption of ASU Bank loan participations Fair Value, Option, Loans Held as Assets, Aggregate Fair Value Fair Value, Option, Loans Held as Assets, Aggregate Fair Value 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 Net realized and unrealized losses on investments 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 Number of impaired loans Number Of Impaired Loans Represents the number of impaired loans. Number of issuers with impaired loans Number Of Issuers With Impaired Loans Number Of Issuers With Impaired Loans Carrying value of impaired loans Impaired Financing Receivable, with Related Allowance, Recorded Investment Unpaid principal on impaired loans Impaired Financing Receivable, Unpaid Principal Balance Allowance for credit losses on impaired loans Impaired Financing Receivable, Related Allowance Average recorded investment in impaired bank loans Impaired Financing Receivable, Average Recorded Investment 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. Carrying value of collateralized loan obligation held Carrying Value Of Collateralized Loan Obligation Held Represents carrying value of carrying value of collateralized loan obligation held. Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Capital Stock and Equity Awards Stockholders' Equity Note Disclosure [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Nonrecurring basis Fair Value, Nonrecurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Quoted Prices in Active Markets for Identical Assets Level 1 Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs Level 2 Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs Level 3 Fair Value, Inputs, Level 3 [Member] 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] Bank loan participations held-for-investment Impaired Bank Loan Participations Held For Investment Represents impaired bank loan participations held for investment. Debt Disclosure [Abstract] Senior Debt Debt Disclosure [Text Block] Schedule of dividends Dividends Declared [Table Text Block] Schedule of summary of option activity Share-based Payment Arrangement, Option, Activity [Table Text Block] Schedule of summary of RSU activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Schedule of summary of amount of expense and related tax benefit Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Recurring basis Fair Value, Recurring [Member] State and municipal US States and Political Subdivisions Debt Securities [Member] Residential mortgage-backed Residential Mortgage Backed Securities [Member] Corporate Corporate Debt Securities [Member] Commercial mortgage and asset-backed Commercial Mortgage Backed Securities [Member] U.S. Treasury securities and obligations guaranteed by the U.S. government US Treasury and Government [Member] Redeemable preferred stock Redeemable Preferred Stock [Member] Equity securities Equity Securities [Member] Preferred stock Common stock Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fixed maturity securities, available-for-sale: Debt Securities, Available-for-sale [Abstract] Total fixed maturity securities, available-for-sale Equity securities: Short-term Investments [Abstract] Total equity securities Equity Securities, FV-NI Short-term investments Short-term Investments Equity [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] RSUs Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Unrecognized share based compensation expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Weighted-average period of unrecognized share based compensation expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Other Operating Expenses Other Operating Income and Expense [Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Recurring Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Available-for-sale fixed maturity securities and equity securities Securities (Assets) [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] 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] Beginning balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Transfers in to Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Maturities, calls and paydowns Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 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 Total gains or losses (realized/unrealized)-Included in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings 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) Ending balance Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Fixed maturity securities, less than 12 months, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months 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 Fixed maturity securities, 12 months or more, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 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 Fixed maturity securities, fair value Fixed maturity securities, gross unrealized losses Income Statement [Abstract] Revenues Revenues [Abstract] Ceded written premiums Ceded Premiums Written Net written premiums Premiums Written, Net Change in net unearned premiums (Increase) Decrease in Unearned Premiums, Net Net earned premiums Other income Other Income Total revenues Expenses Operating Expenses [Abstract] Losses and loss adjustment expenses Other operating expenses Amortization of intangible assets Total expenses Operating Expenses Income tax (benefit) expense Income Tax Expense (Benefit) Net (loss) income Other comprehensive (loss) income: Net unrealized (losses) gains, net of taxes of $(1,391) in 2020 and $1,446 in 2019 Total comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Per share data: Earnings Per Share, Basic and Diluted [Abstract] Basic (loss) earnings per share (in dollars per share) Earnings Per Share, Basic Diluted (loss) earnings per share (in dollars per share) Earnings Per Share, Diluted Dividend declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Weighted-average common shares outstanding: Weighted Average Number of Shares Outstanding, Basic [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Statement of Cash Flows [Abstract] Operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Operating Activities Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Securities available-for-sale: Purchases – fixed maturity securities Payments to Acquire Debt Securities, Available-for-sale Sales – fixed maturity securities Proceeds from Sale of Debt Securities, Available-for-sale Maturities and calls – fixed maturity securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Purchases – equity securities Payments to Acquire Equity Securities FV-NI Payments to Acquire Equity Securities FV-NI Sales – equity securities Proceeds from Sale of Equity Securities FV-NI Proceeds from Sale of Equity Securities FV-NI Bank loan participations: Bank Loan Participations [Abstract] Purchases Payment To Acquire Bank Loan Participations Represents payment to acquire Bank loan participations. Sales Proceeds From Bank Loan Participations Represents cash inflow from sales of bank loan participations. Maturities Proceeds From Maturities From Bank Loan Participations Represents cash inflow from maturities of bank loan participations. Other invested assets: Other Investments [Abstract] Purchases Payments to Acquire Other Investments Return of capital Proceeds From Other Invested Asset Return Of Capital Represents cash inflow from other invested asset return of capital. Redemptions Proceeds From Maturities And Repayments Of Other Invested Assets Represents proceeds from maturities and repayments of other invested assets. Short-term investments, net Payments for (Proceeds from) Short-term Investments Securities receivable or payable, net Payments for (Proceeds from) Unsettled Investments, Net Payments for (Proceeds from) Unsettled Investments, Net Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Senior debt issuances Proceeds from Issuance of Senior Long-term Debt Senior debt repayments Repayments of Senior Debt Dividends paid Payments of Dividends Issuance of common shares under equity incentive plans Proceeds, Issuance of Shares, Share-based Payment Arrangement, Including Option Exercised Common share repurchases Payments for Repurchase of Common Stock Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities 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 Cash, cash equivalents, and restricted cash equivalents at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash equivalents at end of period Supplemental information Supplemental Cash Flow Information [Abstract] Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Commitments and Contingencies Disclosure [Abstract] Contingent Liabilities [Table] Contingent Liabilities [Table] Discloses information about contingent liabilities. Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Raiser Raiser [Member] Raiser [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Third-party Reinsureds Third-party Reinsureds [Member] Third-party Reinsureds [Member] JRG Reinsurance Company, Ltd. Jrg Reinsurance Company Ltd [Member] Represents reinsurance subsidiary of the entity. Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Letter of credit 75 Million Letter Of Credit 75 Million [Member] Letter Of Credit 75 Million [Member] Letter of credit 102.5 Million 2013 Facility [Member] 2013 Facility Letter of credit 100 Million 2017 Facility [Member] 2017 Facility 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. Number of credit facilities Number of Credit Facilities Number of Credit Facilities Letters of credit facility, amount Letter Of Credit Facility Amount Represents amount of letter of credit facility. Amount of letters of credit issued Letters of Credit Outstanding, Amount Assets deposited for securing letters of credit Assets Deposited For Securing Letters Of Credit Represents amount of assets deposited for securing letters of credit. Line of credit (up to) Line of Credit Facility, Maximum Borrowing Capacity Collateral trust arrangement amount Assets Held-in-trust Amount of collateral held Restricted Cash Equivalents Total Amount (thousands) Dividends, Common Stock, Cash Cost or Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] One year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost After one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost After five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost After ten years Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Residential mortgage-backed Residential Mortgage Backed Amortized Cost Represents Amortized Cost of Residential mortgage-backed securities. Commercial mortgage and asset-backed Commercial Mortgage And Asset Backed Amortized Cost Represents amortized cost of commercial mortgage and asset-backed. Redeemable preferred stock Redeemable Preferred Stock Amortized Cost Represents amortized cost of redeemable preferred stock. Total fixed maturity securities, Cost or Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Fair Value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] One year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value After one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value After five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value After ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Residential mortgage-backed Residential Mortgage Backed Fair Value Represents fair value of residential mortgage backed. Commercial mortgage and asset-backed Commercial Mortgage And Asset Backed Fair Value Represents fair value of commercial mortgage and asset backed. Redeemable preferred stock Redeemable Preferred Stock Fair Value Represents fair value of Redeemable preferred stock. Total investments available-for-sale, Fair Value Schedule of components of comprehensive income (loss) Comprehensive Income (Loss) [Table Text Block] Net (loss) income to shareholders Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Common share equivalents (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Diluted (in shares) (Loss) earnings per share: Earnings Per Share Reconciliation [Abstract] Basic (in dollars per share) Common share equivalents (in dollars per share) Common Share Equivalents Earnings Per Share Represents amount of earnings per share of common share equivalents. Diluted (in dollars per share) Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Unsecured Debt Unsecured Debt [Member] Line of Credit Line of Credit [Member] 2013 Facility 2017 Facility Debt Instrument [Line Items] Debt Instrument [Line Items] Amount drawn Proceeds from Lines of Credit Drawn balance outstanding Long-term Line of Credit Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Title of Individual [Axis] Title of Individual [Axis] Title of Individual [Domain] Title of Individual [Domain] Non-employee directors Non-employee Directors [Member] Non-employee Directors [Member] Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Unvested, beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Unvested, end of period (in shares) 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] Unvested, beginning of period (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 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 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 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 Unvested, end of period (in dollars per share) Vesting period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Statement of Financial Position [Abstract] Fixed maturity securities, available-for-sale, at amortized cost Equity securities, at cost Equity Securities, FV-NI, Cost Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] James River Group, Inc. James River Group Inc [Member] Represents information regarding James River Group, Inc. Business Acquisition [Line Items] Business Acquisition [Line Items] Percentage of outstanding shares Business Acquisition, Percentage of Voting Interests Acquired Goodwill Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2014 LTIP Long Term Incentive Plan 2014 [Member] Represents information regarding Long Term Incentive Plan 2014. 2014 Director Plan Non Employee Director Incentive Plan 2014 [Member] Represents information regarding 2014 Non Employee Director Incentive Plan. Non-qualified stock options Share-based Payment Arrangement, Option [Member] Maximum number of shares available for issuance Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Number of shares available for grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Increase in number of shares authorized for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized Fixed maturity securities Debt Securities, Available-for-sale, Realized Gain (Loss) Bank loan participations Bank Loan Participations, Net Gain (Loss) Bank Loan Participations, Net Gain (Loss) Net realized and unrealized gains (losses) on investments in equity securities Equity Securities, FV-NI, Gain (Loss) Schedule Of Acquired Intangible Assets [Table] Schedule Of Acquired Intangible Assets [Table] Represents the tabular information related to intangible assets acquired in the acquisition. Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trademarks Trademarks [Member] Insurance licenses and authorities Licensing Agreements [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Broker relationships Broker Relationships [Member] Represents information related to broker relationships. 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. Identifiable intangibles not subject to amortization Indefinite-lived Intangible Assets (Excluding Goodwill) Identifiable intangible assets subject to amortization Finite-Lived Intangible Assets, Net [Abstract] Gross Carrying Amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Total Intangible Assets, Gross Intangible Assets, Gross (Excluding Goodwill) Life Finite-Lived Intangible Asset, Useful Life Tax on net unrealized gains (losses) Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax Total investments available-for-sale, Gross Unrealized Gains Total investments available-for-sale, Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Market approach Valuation, Market Approach [Member] Level 3 Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Equity securities Impaired bank loan participations held for investment Assets Assets [Abstract] Invested assets: Fixed maturity securities, available-for-sale, at fair value (amortized cost: 2020 – $1,540,822; 2019 – $1,398,533) Equity securities, at fair value (cost: 2020 – $77,218; 2019 – $73,244) Bank loan participations (2020: at fair value; 2019: held-for-investment, at amortized cost, net of allowance) Bank loan participations (2020: at fair value; 2019: held-for-investment, at amortized cost, net of allowance) Short-term investments Other Short-term Investments Other invested assets Other Investments Total invested assets Investments Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash equivalents Accrued investment income Accrued Investment Income Receivable Premiums receivable and agents’ balances, net Premiums and Other Receivables, Net Reinsurance recoverable on unpaid losses, net Reinsurance recoverable on paid losses Reinsurance Recoverable for Paid Claims and Claims Adjustments Prepaid reinsurance premiums Prepaid Reinsurance Premiums Deferred policy acquisition costs Deferred Policy Acquisition Cost Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Other assets Other Assets Total assets Liabilities and Shareholders’ Equity Liabilities and Equity [Abstract] Liabilities: Liabilities [Abstract] Reserve for losses and loss adjustment expenses Unearned premiums Unearned Premiums Payables to reinsurers Reinsurance Payable Funds held Funds Held under Reinsurance Agreements, Liability Senior debt Junior subordinated debt Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust Accrued expenses Accrued Liabilities Other liabilities Other Liabilities Total liabilities Liabilities Commitments and contingent liabilities Commitments and Contingencies Shareholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Common Shares – 2020 and 2019: $0.0002 par value; 200,000,000 shares authorized; 30,520,428 and 30,424,391 shares issued and outstanding, respectively Common Stock, Value, Issued Preferred Shares – 2020 and 2019: $0.00125 par value; 20,000,000 shares authorized; no shares issued and outstanding Preferred Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders’ equity Total liabilities and shareholders’ equity Liabilities and Equity Reserve For Losses And Loss Adjustment Expenses [Table] Reserve For Losses And Loss Adjustment Expenses [Table] A table or schedule providing information pertaining to reserve for losses and Loss adjustment expenses. Reserve For Losses And Loss Adjustment Expenses [Line Items] Reserve For Losses And Loss Adjustment Expenses [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. Favorable development on prior year loss reserves Development On Prior Year Loss Reserves [Abstract] Reserve for losses and loss adjustment expenses New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] VIE, not primary beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] UNITED STATES UNITED STATES BERMUDA BERMUDA New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Number of insurance companies Number Of Insurance Companies This element represents number of insurance companies owned by the entity. Investment in variable interest entities Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Pre-tax loss Income tax benefit Effective U.S. federal income tax expense rate Effective Income Tax Rate Reconciliation, Percent Bank loan participations Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables Segment Information Segment Reporting Disclosure [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] Schedule of summary of company's segment results Schedule of Segment Reporting Information, by Segment [Table Text Block] 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] Schedule of gross carrying amounts and accumulated amortization Schedule of Intangible Assets and Goodwill [Table Text Block] Fixed maturity securities, gross realized gains Debt Securities, Available-for-sale, Realized Gain Fixed maturity securities, gross realized losses Debt Securities, Available-for-sale, Realized Loss Fixed maturity securities Bank loan participations, gross realized gains Bank Loan Participations, Gross Realized Gain Represents the gross realized gains on bank loan participations. Bank loan participations, gross realized losses Bank Loan Participations, Gross Realized Loss Represents the gross realized losses on bank loan participations. Changes in fair values of bank loan participations Bank Loan Participations, Changes in Fair Value Bank Loan Participations, Changes in Fair Value Bank loan participations Equity securities, gross realized gain Equity Securities, FV-NI, Realized Gain Equity securities, gross realized losses Equity Securities, FV-NI, Realized Loss Equity securities, changes in fair values of equity securities Equity Securities, Changes in Fair Value Equity Securities, Changes in Fair Value Equity securities Equity Securities, FV-NI, Realized Gain (Loss) 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. 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. Short-term investments and other Short Term Investments And Other Gross Realized Gains (Losses) Short Term Investments And Other Gross Realized Gains (Losses) Total Options Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period End of period (in shares) Exercisable, end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted- Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price End of period (in dollars per share) Exercisable, end of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Contractual life (in years) Share Based Arrangement by Share Based Award Option Contractual Life Share Based Arrangement by Share Based Award Option Contractual Life Weighted-average remaining contractual life of options outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted-average remaining contractual life of options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Contingent Liabilities Commitments and Contingencies Disclosure [Text Block] Earnings Per Share Earnings Per Share [Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Unrealized (losses) gains arising during the period, before U.S. income taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax U.S. income taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Unrealized (losses) gains arising during the period, net of U.S. income taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Less reclassification adjustment: Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax [Abstract] Net realized investment gains (losses) Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax U.S. income taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Reclassification adjustment for investment gains (losses) realized in net income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Other comprehensive (loss) income Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options and restricted share units ("RSU's") Stock Options And Restricted Stock Units Rsu [Member] Stock options and share instrument which is convertible to stock or an equivalent amount of cash, after a specified period of time or when specified performance conditions are met. Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Number of securities excluded from the calculations of diluted earnings per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Investments Investment [Text Block] 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. Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Cash dividend declared (in dollars per share) Dividends Payable, Amount Per Share Dividends payable, date to be paid Dividends Payable, Date to be Paid Dividend payable, record date Dividends Payable, Date of Record RSUs Number of common shares issued during period (in shares) Stock Issued During Period, Shares, New Issues Restricted stock unit dividend equivalents Restricted Stock Unit Dividend Equivalents Represents amount of dividend equivalent of RSU's. Dividends payable Dividends Payable Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Investment Income [Table] Investment Income [Table] Investment in LLC Investment In Llc [Member] Represents investment in LLC`s. Bank Holding Company Investment In Bank Holding Company [Member] Represents information about Investment in bank holding company. Renewable energy LLCs Renewable Energy Llcs [Member] Name of the investment category. Renewable energy notes receivable Renewable Energy Bridge Financing Notes [Member] Name of the investment category. Limited partnerships Partnership Interest [Member] Net Investment Income [Line Items] Net Investment Income [Line Items] Total other invested assets Investment income Investment Income, Net Ownership percentage Equity Method Investment, Ownership Percentage Cash distributions from LLCs Proceeds from Equity Method Investment, Distribution Repayment received Proceeds from Other Investments Maturities and Repayments Proceeds from of Other Investments Maturities and Repayments Rate of interest Investment Interest Rate Carrying values of limited partnerships held Carrying Values Of Limited Partnerships Held Represents carrying values of limited partnerships held across segments. Investment income (loss) Income (Loss) from Equity Method Investments Investment in private subordinated notes Notes Receivable Represents carrying value of notes receivable as on reporting date. Interest income Investment Income, Interest Cover [Abstract] Document Type Document Type Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number 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 Entity Address, City or Town Entity Address, City or Town Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Address, Country Entity Address, Country City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Shell Company Entity Shell Company Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Schedule of other operating expenses Schedule of Other Operating Cost and Expense, by Component [Table Text Block] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Bank loan participations Other invested assets – notes receivable Liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Junior subordinated debt