Financial Assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Share repurchase approved amount Stock Repurchase Program, Authorized Amount Amount paid for remedies (less than) Loss Contingency Accrual, Payments Supplemental Disclosure of Cash Flow Information Supplemental Cash Flow Information [Abstract] Accumulated Net Investment Gains (Losses) On Investments AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net income Net income Net Income (Loss) Attributable to Parent ILN 2015 & 2016 Radnor Re 2019-2 Ltd. [Member] Radnor Re 2019-2 Ltd. [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Entity Emerging Growth Company Entity Emerging Growth Company Maximum Exposure to Loss, Off - Balance Sheet Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Off The Balance Sheet Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Off The Balance Sheet Reserve rate Risk In Force, Reserve Percentage Risk In Force, Reserve Percentage Statistical Measurement [Domain] Statistical Measurement [Domain] Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Direct Direct Premiums Earned Other-than-temporary impairments Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Recognized in Earnings 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 Additional paid-in capital Additional Paid in Capital, Common Stock Entity Filer Category Entity Filer Category Other comprehensive income, before tax Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent Fair Value Debt Securities Available For Sale Continuous Unrealized Loss Position [Abstract] Debt Securities Available For Sale Continuous Unrealized Loss Position [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] Net (decrease) increase in cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Stockholders’ Equity Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Stock-based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Mortgage Insurance Linked Notes Mortgage Insurance Linked Notes [Member] Mortgage Insurance Linked Notes [Member] Document Fiscal Year Focus Document Fiscal Year Focus Credit Concentration Risk Credit Concentration Risk [Member] Due after 10 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Subsequent Event Type [Domain] Subsequent Event Type [Domain] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] 2021 Performance based share awards Two Thousand Twenty One Performance-Based Grants [Member] Two Thousand Twenty One Performance-Based Grants Remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Antidilutive nonvested shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Consumer, non-cyclical Consumer, Non-cyclical Sector [Member] Consumer, Non-cyclical Sector [Member] Maximum Exposure to Loss, On - Balance Sheet Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount On The Balance Sheet Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount On The Balance Sheet Investment Secondary Categorization [Axis] Investment Secondary Categorization [Axis] Other underwriting and operating expenses Other Underwriting and Operating Expenses Represents the aggregate amount of costs incurred during the period, such as those relating to general administration and policy maintenance that do not vary with, and are not primarily related to the acquisition or renewal of insurance contracts and other operating costs, that are associated with the entity's normal revenue producing operation. Number of states in which the entity is licensed to write mortgage insurance Number of States in which Entity Operates 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 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 Annual commitment fee rate Line of Credit Facility, Commitment Fee Percentage Municipal debt securities Municipal debt securities Municipal Bonds [Member] Title of Individual [Domain] Title of Individual [Domain] Proceeds from maturity of investments available for sale Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Incentive Program Bonus Award Fiscal Year Performance Incentive Program Bonus Award Fiscal Year Performance [Member] Represents an incentive program covering bonus awards based on performance for previous fiscal year. Award Type [Domain] Award Type [Domain] Credit Facility [Domain] Credit Facility [Domain] Assets Assets [Abstract] Subtotal Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value Schedule of investments available for sale Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of amortized cost and fair value of investments available for sale by contractual maturity Investments Classified by Contractual Maturity Date [Table Text Block] Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Schedule of realized gross gains and losses on sale of investments available for sale Schedule of Realized Gain (Loss) [Table Text Block] Concentration risk, percentage Concentration Risk, Percentage Reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses (LAE) Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Entity Address, City or Town Entity Address, City or Town VIE Variable Interest Entity, Not Primary Beneficiary [Member] Retained Earnings Retained Earnings [Member] Debt Instrument [Axis] Debt Instrument [Axis] Investments Investment available for sale Fair Value Debt Securities, Available-for-sale [Abstract] Reinsurance Disclosures [Abstract] Reinsurance Disclosures [Abstract] Losses and expenses: Benefits, Losses and Expenses [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Accrued investment income Increase (Decrease) in Accrued Investment Income Receivable Nonvested Shares, Share Units Nonvested Shares, Share Units [Member] Nonvested Shares, Share Units [Member] AOCI tax effect, beginning of period AOCI tax effect, end of period AOCI Tax, Attributable to Parent Related Party [Axis] Related Party [Axis] Schedule of fair value of investments in an unrealized loss position and related unrealized losses Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block] Distribution of income from other invested assets Proceeds from Equity Method Investment, Distribution Term Loan Secured Debt [Member] Accounts receivable Increase (Decrease) in Accounts Receivable Increase in contingency reserve Statutory Accounting Practices, Increase (Decrease) in Contingency Reserve Represents the amount of increase (decrease) in contingency reserve. Reinsurance Policy [Domain] Reinsurance Policy [Domain] Reinsurance Policy, Type [Axis] Reinsurance Policy, Type [Axis] Essent Guaranty Essent Guaranty Inc [Member] Represents information pertaining to Essent Guaranty, Inc. (Essent Guaranty), a regulated and licensed indirect wholly-owned subsidiary of the reporting entity. Shares tendered by employees to pay employee withholding taxes (in shares) Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Vesting (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Dilutive effect of nonvested shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Nonvested Shares with Forfeitable Dividends Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Prior years Incurred claims and claim adjustment expenses Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Weighted average interest during period Debt, Weighted Average Interest Rate Revision adjustment Revision of Prior Period, Error Correction, Adjustment [Member] Entity Interactive Data Current Entity Interactive Data Current Basic materials Basic Materials Sector [Member] Basic Materials Sector [Member] Prior years Favorable prior year development Prior Year Claims and Claims Adjustment Expense Basic (in dollars per share) Basic earnings per share (in dollars per share) Earnings Per Share, Basic Due after 5 but within 10 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Amortized Cost Remaining First Layer Retention Reinsurance Retention Policy, Amount Retained Reinsurance retention policy, debt issued to cover insurance, term Reinsurance, Debt Issued To Cover Insurance, Term Reinsurance, Debt Issued To Cover Insurance, Term Outstanding at beginning of year (in shares) Outstanding at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Document Type Document Type Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Entity Current Reporting Status Entity Current Reporting Status Dividends Restrictions Dividend Payment Restrictions [Text Block] 2020 and 2021 Vintage Year 2020 and 2021 [Member] Vintage Year 2020 and 2021 Unearned premium reserve Increase (Decrease) in Unearned Premiums Less: Reinsurance recoverables Plus: Reinsurance recoverables Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Dividends Restrictions Statutory Accounting Practices [Line Items] Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract] Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract] Amount outstanding, gross Long-term Debt, Gross Increase of margin component of reinsurance premium Risk Margin Increase After Optional Termination Date Risk Margin Increase After Optional Termination Date Plan Name [Axis] Plan Name [Axis] Statutory net income Statutory Accounting Practices, Statutory Net Income Amount Total assets at fair value Assets, Fair Value Disclosure Return of investment from other invested assets Proceeds from Equity Method Investment, Distribution, Return of Capital Quoted Prices in Active  Markets for Identical Instruments (Level 1) Fair Value, Inputs, Level 1 [Member] Document Transition Report Document Transition Report Direct Direct Premiums Written Early COVID-19 defaults Early COVID-19 Defaults [Member] Early COVID-19 Defaults Certain members of senior management Certain Senior Management [Member] Represents some, but not all, of a team of individuals at the highest level of organizational management who have the day-to-day responsibilities of managing the entity. Total liabilities and stockholders’ equity Liabilities and Equity Tax Effect AOCI Attributable To Parent, Tax [Roll Forward] AOCI Attributable To Parent, Tax Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] 6% Compounded Annual Growth Rate, Three Year Book Value Achieved, 6 Percent [Member] Compounded Annual Growth Rate, Three Year Book Value Achieved, 6 Percent First Vesting Period Share-based Payment Arrangement, Tranche One [Member] Scenario [Axis] Scenario [Axis] Due after 5 but within 10 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Fair Value U.S. agency securities US Government Agencies Debt Securities [Member] Liabilities and Stockholders’ Equity Liabilities and Equity [Abstract] Investment Income [Table] Investment Income [Table] Remaining Insurance in Force Reinsurance, Remaining Insurance In Force Reinsurance, Remaining Insurance In Force Property and equipment Property, Plant and Equipment, Net [Abstract] Fair value of the required investments on deposit in trusts Assets Held-in-trust Less: Reclassification adjustment for gains (losses) included in net income, tax effect Reclassification from AOCI, Current Period, Tax Operating Activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Earnings per Share (EPS) Earnings Per Share [Text Block] Treasury stock acquired Shares acquired and cancelled Treasury Stock, Value, Acquired, Cost Method U.S. agency mortgage-backed securities Collateralized Mortgage Backed Securities [Member] Option to increase capacity Line of Credit Facility, Accordion Feature, Increase Limit Line of Credit Facility, Accordion Feature, Increase Limit Schedule of statutory net income, statutory surplus and contingency reserve liability Statutory Accounting Practices Disclosure [Table Text Block] Mortgage Insurance Mortgage Insurance [Member] Mortgage Insurance [Member] Minimum Minimum [Member] Realized gross gains Debt Securities, Available-for-sale, Realized Gain Nature of Operations and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Ceded premiums earned related to percent of risk on all other eligible policies written Reinsurance, Ceded Premiums Earned, Percent Of Risk On All Other Eligible Policies Reinsurance, Ceded Premiums Earned, Percent Of Risk On All Other Eligible Policies Loans in default at end of period Number of Loans in Default Represents the number of loans in default. Affiliated Entity Affiliated Entity [Member] Credit facility borrowings (at carrying value, less unamortized deferred costs of $2,386 in 2021 and $3,280 in 2020) Long-term Line of Credit Unearned premium reserve Unearned Premiums Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Residential mortgage down payment percentage for which mortgage insurance is generally required (less than) Financing Receivable Consumer Mortgage Insured Down Payment Percentage Represents the percentage of the total sale price that a home buyer contributes in cash towards the purchase of a home for which mortgage insurance is generally required. Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 12 months or more Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Trading Symbol Trading Symbol Less: Reclassification adjustment for gains (losses) included in net income, net of tax Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Percentage of debt securities Percent of investments Investment Owned, Percent of Net Assets Entity Address, Country Entity Address, Country Issuance of common shares Stock Issued During Period, Value, New Issues Revision of Prior Period [Axis] Revision of Prior Period [Axis] Debt Obligations Debt Disclosure [Text Block] Due in 1 year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value Stock-Based Compensation Share-based Payment Arrangement [Text Block] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Dividends paid Payments of Ordinary Dividends, Common Stock Accounting Policies [Abstract] Accounting Policies [Abstract] Non-U.S. government securities Non-U.S. government securities: Debt Security, Government, Non-US [Member] Common shares, $0.015 par value: Authorized - 233,333; issued and outstanding - 110,915 shares in 2021 and 112,423 shares in 2020 Common Stock, Value, Issued Three-Year Book Value Per Share CAGR Compounded Annual Growth Rate, Three Year Book Value Compounded Annual Growth Rate, Three Year Book Value Amortization of premium on investment securities Investment Income, Amortization of Premium Radnor Re 2020-2 Ltd. Radnor Re 2020-2 [Member] Radnor Re 2020-2 Expected weighted average period for recognition of expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 2020 Performance-Based Grants Two Thousand Twenty Performance-Based Grants [Member] Two Thousand Twenty Performance-Based Grants [Member] Outstanding at beginning of year (in dollars per share) Outstanding at end 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 Reinsurance Reinsurance [Text Block] Performance Shares Performance Shares [Member] Maximum Exposure to Loss Variable Interest Entity, Reporting Entity Involvement, Maximum Loss (Gain) Exposure, Amount Variable Interest Entity, Reporting Entity Involvement, Maximum Loss (Gain) Exposure, Amount Commitments and contingencies (see Note 7) Commitments and Contingencies Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Without single maturity date Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Vesting percent Vesting percentile Share-based Compensation Arrangement by Share-based Payment Award, Awards Earned, Percentage Of Target Shares Granted Share-based Compensation Arrangement by Share-based Payment Award, Awards Earned, Percentage Of Target Shares Granted Essent Re Essent Reinsurance Ltd [Member] Represents information pertaining to Essent Reinsurance Ltd. (Essent Re), a wholly-owned Bermuda-domiciled Class 3A Insurer licensed pursuant to Section 4 of the Bermuda Insurance Act 1978, which offers mortgage-related insurance and reinsurance. Nonvested shares Restricted Stock [Member] Payment of issuance costs for credit facility Payments of Debt Issuance Costs Maximum percent of individual ownership Shareholder Voting Rights Ownership Percentage Threshold Shareholder Voting Rights Ownership Percentage Threshold Amortized Cost Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract] Document Period End Date Document Period End Date Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Fixed maturities available for sale, at fair value (amortized cost: 2021 — $4,462,616; 2020 — $3,677,815) Fixed maturities Fixed Maturities [Member] Effects of Reinsurance [Table] Effects of Reinsurance [Table] Entity Registrant Name Entity Registrant Name Cash Cash Contingency reserve liability Statutory Accounting Practices, Statutory Contingency Reserve Liability Represents the amount of contingency reserve liability, as of the balance sheet date, using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country. Radnor Re 2018-1 Ltd. Radnor Re 2018-1 Ltd. [Member] Radnor Re 2018-1 Ltd. Net reserve for losses and LAE at beginning of period Net reserve for losses and LAE at end of period Liability for Unpaid Claims and Claims Adjustment Expense, Net AOCI before tax, beginning of period AOCI before tax, end of period AOCI before Tax, Attributable to Parent Unrealized holding (losses) gains arising during the period, tax effect Other Comprehensive Income (Loss) before Reclassifications, Tax Net premiums written: Premiums Written, Net [Abstract] Other comprehensive income (loss): Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Financial Instrument [Axis] Financial Instrument [Axis] Quarterly cash dividends declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Due after 1 but within 5 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Statutory surplus Statutory Accounting Practices, Statutory Surplus Balance Represents the amount of statutory surplus (stockholders' equity), as of the balance sheet date, using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country. Schedule of dividends declared and paid per common share Dividends Declared [Table Text Block] Issuance costs Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Common Shares Common Stock [Member] Deduct payments for losses and LAE, net of reinsurance, occurring in: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Unrealized holding (losses) gains arising during the period, net of tax OCI, before Reclassifications, Net of Tax, Attributable to Parent Investments available for sale Debt Securities, Available-for-sale [Line Items] Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Recently Issued Accounting Standards Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Vesting Criteria [Domain] Vesting Criteria [Domain] The types of vesting specified for share-based compensation awards. Changes in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Net of Tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Vesting Criteria [Axis] Vesting Criteria [Axis] Information about the type of vesting for share-based compensation awards. Radnor Re Radnor Re [Member] Radnor Re [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Other comprehensive income, tax effect Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Quarterly cash dividends paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Other Reinsurance Other Reinsurance [Member] Other Reinsurance [Member] Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract] Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract] Treasury Stock Treasury Stock [Member] Reserve for Losses and Loss Adjustment Expenses Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] Other accrued liabilities Increase (Decrease) in Accrued Liabilities Purchase of investments available for sale Payments to Acquire Debt Securities, Available-for-sale Reinsurance percentage Reinsurance Retention Policy, Reinsured Risk, Percentage Income tax payments Income Taxes Paid Reserve for losses and LAE Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Performance -Based Vesting Based On Performance [Member] Represents a share based compensation award with vesting based on achievement of performance conditions. Accounts receivable Financing Receivable, after Allowance for Credit Loss Stock repurchased (in shares) Stock Repurchased and Retired During Period, Shares Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment Effect of percentage point decrease on liability claim and claim expense adjustment expense Liability For Claims And Claims Adjustment Expense, Effect Of Percentage Point Decrease on Liability Claim And Claim Expense Adjustment Expense Liability For Claims And Claims Adjustment Expense, Effect Of Percentage Point Decrease on Liability Claim And Claim Expense Adjustment Expense Maximum Maximum [Member] Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Total liabilities Liabilities Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Legal Entity [Axis] Legal Entity [Axis] Award Type [Axis] Award Type [Axis] Total stockholders’ equity Balance, beginning of period Balance, end of period Stockholders' equity Stockholders' Equity Attributable to Parent Current period Current Year Claims and Claims Adjustment Expense Common shares, issued (in shares) Common Stock, Shares, Issued Ceded Ceded Premiums Earned Radnor Re 2021-1 Ltd. Radnor Re 2021-1 [Member] Radnor Re 2021-1 2019 and 2020 Vintage Year 2019 and 2020 [Member] Vintage Year 2019 and 2020 Banking Regulation, Total Capital [Abstract] Banking Regulation, Total Capital [Abstract] Assets on deposit for the benefit of the sponsor Assets On Deposit For The Benefit Of The Sponsor Assets On Deposit For The Benefit Of The Sponsor ILN Radnor Entities [Member] Radnor Entities [Member] Realized gross losses Debt Securities, Available-for-sale, Realized Loss Treasury stock acquired Payments for Repurchase of Common Stock Stockholders’ equity Stockholders' Equity Attributable to Parent [Abstract] Rollforward of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reinsurance for mortgage insurance coverage in excess of 25% Excess Mortgage Insurance Coverage [Member] Represents an arrangement to assume that portion of the risk retained by an affiliate that is in excess of 25% of the balance of any mortgage loan insured by that affiliate after consideration of other reinsurance agreements at that affiliate, in accordance with certain state law requirements. Number of votes per share Common Stock Number Of Votes Per Share Common Stock Number Of Votes Per Share Due after 1 but within 5 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Credit facility borrowings Subordinated Borrowings [Abstract] Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Measurement Frequency [Domain] Measurement Frequency [Domain] COVID-19 COVID-19 [Member] COVID-19 [Member] Interest expense Interest Expense Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Income tax benefit Share-based Payment Arrangement, Expense, Tax Benefit City Area Code City Area Code Essent PA Essent Guaranty Of P A Inc [Member] Represents information pertaining to Essent Guaranty of PA, Inc. (Essent PA), a regulated and licensed indirect wholly-owned subsidiary of the reporting entity. Retained earnings Retained Earnings (Accumulated Deficit) Special revenue bonds Special Revenue Municipal Bonds [Member] A municipal bond whose debt service is payable solely from the revenues derived from operating the facilities acquired or constructed with the proceeds of the bonds. RIF ceded Risk In Force, Ceded Risk In Force, Ceded Share Units Restricted Stock Units (RSUs) [Member] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Revision of Prior Period [Domain] Revision of Prior Period [Domain] Second Vesting Period Share-based Payment Arrangement, Tranche Two [Member] Due after 10 years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost U.S. Treasury securities US Treasury Securities [Member] Other invested assets Equity Method Investments Amendment Flag Amendment Flag 2013 Plan Essent Group Limited2013 Long Term Incentive Plan [Member] Represents the Essent Group Limited 2013 Long-term Incentive Plan (2013 Plan). Prepaid federal income tax Increase (Decrease) in Mortgage Guaranty Insurer United States Mortgage Guaranty Tax and Loss Bonds Represents, for a mortgage guaranty insurer, the increase (decrease) during the reporting period in the amount of investment in United States Mortgage Guaranty Tax and Loss Bonds issued by the Treasury Department for eligibility for certain tax deductions under enacted tax laws. Remaining Risk in Force Reinsurance, Remaining Risk In Force Reinsurance, Remaining Risk In Force Statutory capital and surplus Statutory Accounting Practices, Statutory Capital and Surplus, Balance Effects of Reinsurance [Line Items] Effects of Reinsurance [Line Items] Credit facility repayments Repayments of Lines of Credit Effect of reinsurance Effects of Reinsurance [Table Text Block] Percentage of award issuable if current period end were end of contingency period Share-based Compensation Arrangement by Share-based Payment Award, Award Period to Date Vesting Rights, Percentage Percentage of vesting of share-based compensation awards if the end of the current reporting period were the end of the vesting period. Ceding commission, percent Reinsurance, Ceded Premiums Earned, Ceding Commission, Percent Reinsurance, Ceded Premiums Earned, Ceding Commission, Percent Related Party Transaction [Axis] Related Party Transaction [Axis] Income tax expense Income Tax Expense (Benefit) 14% "Target" Compounded Annual Growth Rate, Three Year Book Value Achieved, 14 Percent [Member] Compounded Annual Growth Rate, Three Year Book Value Achieved, 14 Percent Insurance [Abstract] Insurance [Abstract] Equity Components [Axis] Equity Components [Axis] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Dividends Payable [Table] Dividends Payable [Table] Time-Based Share Awards Time-Based Vesting Based On Service [Member] Represents a share based compensation award with vesting based on length of service. Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Employee Employee [Member] Employee [Member] Investment Type [Axis] Investment Type [Axis] Profit commission, percent, maximum Reinsurance, Profit Commissions, Maximum Reinsurance, Profit Commissions, Maximum Ceded premiums earned related to percent of risk on eligible single premium policies Reinsurance, Ceded Premiums Earned, Percent Of Risk On Eligible Single Premium Policies Reinsurance, Ceded Premiums Earned, Percent Of Risk On Eligible Single Premium Policies Dividends paid to parent company SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Consolidated Subsidiaries Concentration Risk Type [Domain] Concentration Risk Type [Domain] Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Assets on deposit under reinsurance agreement Assets on Deposit Under Reinsurance Agreements Assets on Deposit Under Reinsurance Agreements Communications Communications Sector [Member] Communications Sector [Member] Tax allocation bonds Tax Allocation Municipal Bonds [Member] Bonds issued in conjunction with a redevelopment project. The taxes pledged to their repayment come from the increase of assessed value over and above a pre-established base. The redevelopment creates this added value, known as the tax increment. Add provision for losses and LAE, net of reinsurance, occurring in: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Other assets, fair value Other Assets, Fair Value Disclosure Entity File Number Entity File Number Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Nonvested Shares, Share Units Or DEU Nonvested Shares, Share Units Or DEU [Member] Nonvested Shares, Share Units Or DEU [Member] Reinsurance for mortgage insurance coverage threshold (in excess of) Reinsurance Retention Policy, Reinsured Risk, Percentage Threshold Threshold percentage of risk reinsured on insurance products per entity policy. Investments by Secondary Categorization [Domain] Investments by Secondary Categorization [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] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Small Business Entity Small Business Unrecognized compensation expense Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Reserve for losses and LAE, for prior years Liability for Unpaid Claims and Claims Adjustment Expense Prior Years Liability, as of the balance sheet date, for amounts representing estimated cost of settling unpaid claims for prior years under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims. Equity Component [Domain] Equity Component [Domain] Issuance of management incentive shares Shares Issued, Value, Share-based Payment Arrangement, before Forfeiture Funding commitments Investment Company, Committed Capital Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Incremental compensation expense Share-based Payment Arrangement, Plan Modification, Incremental Cost SEC Schedule, 12-17, Insurance Companies, Reinsurance [Table] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Table] Unamortized deferred costs Debt Issuance Costs, Gross Statement Statement [Line Items] Estimated fair values and carrying amounts of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Other income Other Income Dividends Payable [Line Items] Dividends Payable [Line Items] Total investments Investments Liabilities Liabilities [Abstract] Essent PA Essent PA [Member] Essent PA [Member] Schedule of compensation expense, net of forfeitures, and related tax effects recognized in connection with nonvested shares Share-based Payment Arrangement, Cost by Plan [Table Text Block] Total investments available for sale Fair Value Fair Value Debt Securities, Available-for-sale Remaining Reinsurance in Force Reinsurance, Remaining Reinsurance In Force Reinsurance, Remaining Reinsurance In Force Short-term investments available for sale, at fair value (amortized cost: 2021 — $309,781; 2020 — $726,875) Short-term investments Short-term Investments [Member] Counterparty Name [Domain] Counterparty Name [Domain] Deferred policy acquisition costs Increase (Decrease) in Deferred Policy Acquisition Costs Cancellation of treasury stock Treasury Stock, Retired, Cost Method, Amount Released contingency reserve Statutory Accounting Practices, Release of Contingency Reserve Statutory Accounting Practices, Release of Contingency Reserve Net change in short-term investments Payments for (Proceeds from) Short-term Investments Debt Disclosure [Abstract] Debt Disclosure [Abstract] Schedule of percent of shares issuable under terms of agreement Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] 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 losses and expenses Benefits, Losses and Expenses Schedule of coverages and retentions Reinsurance Retention Policy [Table Text Block] ≥75th percentile Share-based Payment Arrangement, Greater than or Equal to 75th Percentile [Member] Share-based Payment Arrangement, Greater than or Equal to 75th Percentile Total Debt Securities, Available-for-sale, Unrealized Loss Position Entity [Domain] Entity [Domain] 2018 Performance-Based Grants Two Thousand Eighteen Performance-Based Grants [Member] Two Thousand Eighteen Performance-Based Grants Amortized cost Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Industrial Industrial Sector [Member] Industrial Sector [Member] Schedule of reconciliation of net income and weighted average common shares outstanding used in computations of basic and diluted earnings per common share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Entity Shell Company Entity Shell Company Local Phone Number Local Phone Number Securities Securities [Member] Securities [Member] Total other comprehensive (loss) income Other comprehensive (loss) income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Forecast Forecast [Member] Vesting [Axis] Vesting [Axis] Net premiums earned: Premiums Earned, Net [Abstract] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Issuance of common shares, net of costs Proceeds from Issuance of Common Stock Total assets Total VIE Assets Assets Realized investment gains, net Gain on the sale of investments, net Realized Investment Gains (Losses) Plan Name [Domain] Plan Name [Domain] Without single maturity date Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Common shares, authorized (in shares) Common Stock, Shares Authorized Interest payments Interest Paid, Excluding Capitalized Interest, Operating Activities Change in unrealized appreciation (depreciation) of investments, tax expense (benefit) Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent Title of Individual [Axis] Title of Individual [Axis] Radnor Re 2020-1 Ltd. Radnor Re 2020-1 [Member] Radnor Re 2020-1 [Member] Subtotal Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Net income Net income Net Income (Loss) Available to Common Stockholders, Basic Unassigned surplus Dividend Payments Restrictions Schedule, Statutory Capital and Surplus Schedule of reconciliation of beginning and ending reserve balances for losses and loss adjustment expenses (LAE) Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Gross investment income Gross Investment Income, Operating Net premiums earned Premiums Earned, Net Stock-based compensation Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Time and Performance- Based Share Awards Vesting Based On Service And Performance [Member] Represents a share based compensation award with vesting based on a combination of length of service and achievement of performance conditions. Asset liquidation period Investment Company, Asset Liquidation Period Investment Company, Asset Liquidation Period Revolving Credit Facility Revolving Credit Facility [Member] ≤25th percentile Share-based Payment Arrangement, Less than or Equal to 25th Percentile [Member] Share-based Payment Arrangement, Less than or Equal to 25th Percentile Measurement Frequency [Axis] Measurement Frequency [Axis] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities EPS calculation Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Residential and commercial mortgage securities Residential and commercial mortgage securities Residential And Commercial Mortgage Securities [Member] Residential And Commercial Mortgage Securities [Member] Limited Partnership Investments Limited Partnership Investments [Member] Limited Partnership Investments Basic (in shares) Basic weighted average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in dollars per share) Diluted earnings per share (in dollars per share) Earnings Per Share, Diluted Vesting [Domain] Vesting [Domain] 10% Compounded Annual Growth Rate, Three Year Book Value Achieved, 10 Percent [Member] Compounded Annual Growth Rate, Three Year Book Value Achieved, 10 Percent Radnor Re 2019-1 Ltd. Radnor Re 2019-1 Ltd. [Member] Radnor Re 2019-1 Ltd. [Member] Other accrued liabilities Other Accrued Liabilities Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Minimum number of votes per share for other shareholders under 9.5% shareholder provision Minimum Number Of Votes Per Share Other Shareholders Minimum Number Of Votes Per Share Other Shareholders Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Net deferred tax liability Deferred Income Tax Liabilities, Net Award vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Ceded Ceded Premiums Written Income (loss) from other invested assets (Income) loss from other invested assets Income (Loss) from Equity Method Investments Decrease in unearned premiums (Increase) Decrease in Unearned Premiums, Net Summary of nonvested common share and nonvested common share unit activity Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block] Corporate debt securities Corporate Debt Securities [Member] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Performance period Share Based Compensation Arrangement by Share Based Payment Award Performance Period Represents the period over which a performance condition to the award is measured, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Concentration Risk Type [Axis] Concentration Risk Type [Axis] Depreciation and amortization Depreciation, Depletion and Amortization Schedule of assets and liabilities measured at fair vale on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Amount available for dividend distribution Amount Available for Dividend Distribution without Affecting Capital Adequacy Requirements Schedule of portion of nonvested shares earned based upon achievement of compounded annual book value per share growth Schedule of Shares Earned Unvested Performance Shares [Table Text Block] Tabular disclosure of shares earned for unvested performance shares. Percent change used in calculation of expense Liability For Claims And Claims Adjustment Expense, Percent Change Used In Calculation Of Expense Liability For Claims And Claims Adjustment Expense, Percent Change Used In Calculation Of Expense Schedule of VIE assets and maximum exposure Schedule of Variable Interest Entities [Table Text Block] Credit facility borrowings Proceeds from Long-term Lines of Credit Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Other assets Other Assets Common shares, outstanding (in shares) Common Stock, Shares, Outstanding Financial Instruments [Domain] Financial Instruments [Domain] Revenues: Revenues [Abstract] 2019 Vintage Year 2019 [Member] Vintage Year 2019 [Member] Government Government Debt Sector [Member] Government Debt Sector Unusual or Infrequent Item, or Both [Domain] Unusual or Infrequent Item, or Both [Domain] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Unrealized holding (losses) gains arising during the period, before tax OCI, before Reclassifications, before Tax, Attributable to Parent Consolidated Entities [Domain] Consolidated Entities [Domain] Investing Activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Accrued investment income Accrued Investment Income Receivable Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Net investment income Net investment income Net Investment Income Loss Contingencies [Line Items] Loss Contingencies [Line Items] Property and equipment (at cost, less accumulated depreciation of $63,545 in 2021 and $60,967 in 2020) Property, Plant and Equipment, Net Radnor Re 2019-2 Ltd. Radnor Re 2019-2 [Member] Radnor Re 2019-2 [Member] Gross Unrealized Losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Other comprehensive income (loss): Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent, Parenthetical Disclosures [Abstract] Debt Instrument [Line Items] Debt Instrument [Line Items] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Related Party Transaction [Domain] Related Party Transaction [Domain] Document Quarterly Report Document Quarterly Report Total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Other assets Increase (Decrease) in Other Operating Assets Total revenues Revenues Relative Total Shareholder Return [Axis] Relative Total Shareholder Return [Axis] Relative Total Shareholder Return Third Vesting Period Share-based Payment Arrangement, Tranche Three [Member] Credit Facility [Table] Line of Credit Facility [Table] Proceeds from sales of investments available for sale Proceeds from Sale of Debt Securities, Available-for-sale Before Tax AOCI Attributable To Parent, Before Tax [Roll Forward] AOCI Attributable To Parent, Before Tax [Roll Forward] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding 2015 & 2016 Vintage Year 2015 and 2016 [Member] Vintage Year 2015 and 2016 [Member] Number of investment securities in an unrealized loss position Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Fair Value Debt Securities, Trading and Available-for-sale Compensation expense Share-based Payment Arrangement, Expense Unusual or Infrequent Item, or Both [Axis] Unusual or Infrequent Item, or Both [Axis] Certificate of participation bonds Certification Of Participation Bonds [Member] Represents a type of financing where an investor purchases a share of the lease revenues of a program rather than the bond being secured by those revenues. Earnings per share: Earnings Per Share, Basic and Diluted [Abstract] Net premiums written Net premiums written 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] Document Fiscal Period Focus Document Fiscal Period Focus Indemnifications related to contract underwriting services Indemnification Agreement [Member] Investments [Domain] Investments [Domain] 2019 Performance-Based Grants Two Thousand Nineteen Performance-Based Grants [Member] Two Thousand Nineteen Performance-Based Grants [Member] Counterparty Name [Axis] Counterparty Name [Axis] Cash at beginning of year Cash at end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Dividends and dividend equivalents declared Dividends Common shares, par value (in dollars per share) Common Stock, Par or Stated Value Per Share DEUs Dividend Equivalent Unit [Member] Dividend Equivalent Unit [Member] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Internal Investment Grade Internal Investment Grade [Member] Entity Central Index Key Entity Central Index Key Security Exchange Name Security Exchange Name Fair value of investments deposited with insurance regulatory authorities Debt Securities, Available-for-sale, Restricted Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Amortization period Amortization Period Excess of Loss Portfolio Amortization Period Excess of Loss Portfolio Utilities Utilities Sector [Member] Utilities Sector [Member] Less: Reclassification adjustment for (losses) gains included in net income, before tax Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Reserve for losses and LAE Reserve for losses and LAE at beginning of period Reserve for losses and LAE at end of period Liability for Claims and Claims Adjustment Expense Diluted (in shares) Diluted weighted average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Recurring Fair Value, Recurring [Member] Prepaid federal income tax Mortgage Guaranty Insurer United States Mortgage Guaranty Tax and Loss Bonds Represents, for a mortgage guaranty insurer, the amount of investment in United States Mortgage Guaranty Tax and Loss Bonds issued by the Treasury Department for eligibility for certain tax deductions under enacted tax laws. Related Party [Domain] Related Party [Domain] Current Fiscal Year End Date Current Fiscal Year End Date Due in 1 year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Capital Stock Stockholders' Equity Note Disclosure [Text Block] Technology Technology Debt Sector [Member] Technology Debt Sector [Member] (Benefit) provision for losses and LAE Net incurred losses and LAE during the current period Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Investment expenses Investment Income, Investment Expense Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Purchase of other invested assets Payments to Acquire Equity Method Investments Other comprehensive income (loss): Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent [Abstract] Credit Facility [Axis] Credit Facility [Axis] Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Change in: Increase (Decrease) in Operating Capital [Abstract] Energy Energy Sector [Member] Energy Sector [Member] Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Change in unrealized (depreciation) appreciation of investments, net of tax (benefit) expense of ($8,599) and $3,856 in the three months ended September 30, 2021 and 2020 and ($10,944) and $14,469 in the nine months ended September 30, 2021 and 2020 Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent 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 Quota share reinsurance Quota Share Reinsurance Transaction [Member] Represents an agreement between an insurer and a reinsurer whereby the reinsurer pays an agreed-upon percentage of all losses the insurer sustains. Deferred policy acquisition costs Deferred Policy Acquisition Cost Relative Total Shareholder Return [Domain] Relative Total Shareholder Return [Domain] Relative Total Shareholder Return Quota Share Reinsurance Quota Share Reinsurance [Member] Quota Share Reinsurance [Member] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] Panel of Reinsurers Panel Of Reinsurers [Member] Panel Of Reinsurers [Member] 12% Compounded Annual Growth Rate, Three Year Book Value Achieved, 12 Percent [Member] Compounded Annual Growth Rate, Three Year Book Value Achieved, 12 Percent Consumer, cyclical Consumer, Cyclical Sector [Member] Consumer, Cyclical Sector [Member] Credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity 2017 Vintage Year 2017 [Member] Vintage Year 2017 Money market funds Money Market Funds [Member] Loss Contingencies [Table] Loss Contingencies [Table] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Credit Facility [Line Items] Line of Credit Facility [Line Items] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Title of 12(b) Security Title of 12(b) Security Financial Financial Sector [Member] Financial Sector [Member] Statement [Table] Statement [Table] Net loss and LAE payments during the current period Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid 50th percentile "Target" Share-based Payment Arrangement, 50th Percentile [Member] Share-based Payment Arrangement, 50th Percentile Schedule of net investment income Investment Income [Table Text Block] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Asset-backed securities Asset-backed Securities [Member] Accounting Standards Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Statutory Accounting Statutory Accounting Disclosure [Text Block] Represents the entire disclosure pertaining to the statutory accounting. Statistical Measurement [Axis] Statistical Measurement [Axis] Subsequent event Subsequent Event [Member] Cover [Abstract] Cover [Abstract] 2018 Vintage Year 2018 [Member] Vintage Year 2018 Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain] 8% Compounded Annual Growth Rate, Three Year Book Value Achieved, 8 Percent [Member] Compounded Annual Growth Rate, Three Year Book Value Achieved, 8 Percent Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Scenario [Domain] Scenario [Domain] Adjustments to reconcile net income to net cash provided by 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] General obligation bonds General Obligation Municipal Bonds [Member] A bond secured by a pledge of the issuer's taxing powers (limited or unlimited). More commonly the general obligation bonds of local governments are paid from ad valorem property taxes and other general revenues. Considered the most secure of all municipal debt. Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Components of net investment income Net Investment Income [Line Items] 12 months or more Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Current period Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Insurance Premium Revenue Recognition Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Deferred income tax provision Deferred Income Tax Expense (Benefit)