Reinsurance recoverable Increase (Decrease) in Reinsurance Recoverable Due after one through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Gain from change in fair value of warrant liability Gain from change in fair value of warrant liability Gain from change in fair value of warrant liability Gain (Loss) on Change in Fair Value of Warrant Liability Gain (Loss) on Change in Fair Value of Warrant Liability Current year IBNR Current Year Claims and Claims Adjustment Expense, Incurred but Not Reported Current Year Claims and Claims Adjustment Expense, Incurred but Not Reported Insurance claims and claim expenses (benefits) Policyholder Benefits and Claims Incurred, Net Net income amount Statutory Accounting Practices, Statutory Net Income Amount Schedule of aging unrealized losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Loan-to-value ratio (less than) Loans In Pool, Loan To Value Ratio Loans In Pool, Loan To Value Ratio Prior year, IBNR Prior Year Claims and Claims Adjustment Expense, Incurred but Not Reported Prior Year Claims and Claims Adjustment Expense, Incurred but Not Reported Change in unrealized investment gains/losses, net of tax benefit/expense Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Schedule of reconciliation of liability for insurance claims and (benefits) claim expenses Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Net realized investment (losses) gains Gain (Loss) on Investments Debt Instrument [Axis] Debt Instrument [Axis] Credit facility borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Due after ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Changes in operating assets and liabilities: Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract] Additional paid-in capital Additional Paid in Capital Reserve for insurance claims and claim expenses Total gross liability for unpaid claims and claim adjustment expenses Beginning Balance Ending balance Liability for Claims and Claims Adjustment Expense Financial Instruments [Domain] Financial Instruments [Domain] Basis spread on variable rate (in percent) Debt Instrument, Basis Spread on Variable Rate Statistical Measurement [Domain] Statistical Measurement [Domain] Number of covered claims included in number of claims paid | claim Liability for Paid Claims and Claims Adjustment Expense, Number of Covered Claims Included In Number of Paid Claims Liability for Paid Claims and Claims Adjustment Expense, Number of Covered Claims Included In Number of Paid Claims Stated interest rate (in percent) Debt Instrument, Interest Rate, Stated Percentage Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] Common stock: class A shares issued related to warrant exercises Stock Issued During Period, Value, Conversion of Convertible Securities Total number of policies in-force Liability For Unpaid Claims And Claims Adjustment Expense, Incurred But Not Reported (IBNR) Claims, Total Policies In-Force Liability For Unpaid Claims And Claims Adjustment Expense, Incurred But Not Reported (IBNR) Claims, Total Policies In-Force Due in one year or less Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value Repurchase of common stock Treasury Stock, Value, Acquired, Cost Method Net income Net income Net income Net Income (Loss) Attributable to Parent Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Anti-dilutive shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Debt Secured Debt Reclassification adjustment for realized losses (gains) included in net income, net of tax (benefit) expense of $(7) and $86 for the quarters ended March 31, 2023 and 2022, respectively Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Number of states in which the entity operates Number of States in which Entity Operates Net investment income Net Investment Income Equity Component [Domain] Equity Component [Domain] Scenario [Axis] Scenario [Axis] Secured Debt Secured Debt [Member] Current first layer retained loss Current First Layer Retained Loss Current First Layer Retained Loss Redemption price (in percent) Debt Instrument, Redemption Price, Percentage Utilities Utilities, Industry Group [Member] Utilities, Industry Group [Member] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Total assets Assets, Fair Value Disclosure Investment income Investment Income, Interest and Dividend Municipal debt securities Municipal debt securities US States and Political Subdivisions Debt Securities [Member] Component of claims paid covered under QSR Transaction Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Including Amounts Covered By Insurance, Amount Under QSR Transaction Component of total amount of payments to settle insured claims and pay costs incurred in the claims settlement process, including amount covered by insurance, covered under QSR transaction. Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Treasury Stock, at cost: 3,589,283 and 2,922,863 common shares as of March 31, 2023 and December 31, 2022, respectively Treasury Stock, Common, Value Fixed maturities, available-for-sale, at fair value (amortized cost of $2,383,982 and $2,352,747 as of March 31, 2023 and December 31, 2022, respectively) Fair Value Fair Value Fair value of securities Debt Securities, Available-for-Sale Variable rate floor (in percent) Debt Instrument, Variable Interest Rate Floor Debt Instrument, Variable Interest Rate Floor Net premiums earned Premiums Earned, Net [Abstract] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Borrowings outstanding Long-Term Line of Credit Common stock - class A shares, $0.01 par value; 86,869,169 shares issued and 83,279,886 shares outstanding as of March 31, 2023 and 86,472,742 shares issued and 83,549,879 shares outstanding as of December 31, 2022 (250,000,000 shares authorized) Common Stock, Value, Outstanding Entity Address, State or Province Entity Address, State or Province Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Reinsurance coverage amount Reinsurance Retention Policy, Ceded Aggregate Premiums Reinsurance Retention Policy, Ceded Aggregate Premiums Due in one year or less Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Schedule of fair values and gross unrealized gains and losses Debt Securities, Available-for-Sale [Table Text Block] Due after five through ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value Other liabilities Other Liabilities Expenses Costs and Expenses [Abstract] Due after one through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Legal Entity [Axis] Legal Entity [Axis] Total liabilities Liabilities Unearned premiums Increase (Decrease) in Unearned Premiums Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Claims applied to pool deductible Liability for Unpaid Claims and Claims Adjustment Expense, Claims Applied to Deductible Liability for Unpaid Claims and Claims Adjustment Expense, Claims Applied to Deductible Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Revolving credit facility Revolving Credit Facility [Member] Document Type Document Type Secured overnight financing rate Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Net realized investment losses (gains) Net realized investment (losses) gains Debt Securities, Available-for-Sale, Realized Gain (Loss) Ceded Credit Risk [Line Items] Ceded Credit Risk [Line Items] Debt Debt Disclosure [Text Block] Entity Shell Company Entity Shell Company Direct Direct Premiums Earned Schedule of net investment income Investment Income [Table Text Block] Claims paid, including amounts covered by insurance Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Including Amounts Covered By Insurance Amount of payments to settle insured claims and pay costs incurred in the claims settlement process, including amount covered by insurance. Financial Instrument [Axis] Financial Instrument [Axis] Proceeds from issuance of common stock related to warrant exercises Proceeds from Warrant Exercises Document Period End Date Document Period End Date Number of excess-of-loss reinsurance agreements Number of Excess-of-Loss Reinsurance Agreements Number of Excess-of-Loss Reinsurance Agreements Premiums Receivable Premiums Receivable Note [Text Block] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Primary loans in default Liability For Unpaid Claims And Claims Adjustment Expense, Incurred But Not Reported (IBNR) Claims, Number Of Primary Loans In Default Liability For Unpaid Claims And Claims Adjustment Expense, Incurred But Not Reported (IBNR) Claims, Number Of Primary Loans In Default Total assets Assets Total claims and claim expenses paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Debt Disclosure [Abstract] Debt Disclosure [Abstract] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes Stock Issued During Period, Value, Employee Stock Purchase Plan, Net of Tax Withholdings Stock Issued During Period, Value, Employee Stock Purchase Plan, Net of Tax Withholdings Schedule of fair value measurements of financial instruments Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Change in unrealized investment gains/losses, tax expense (benefit) OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax NMIC and Re One combined NMic and Re one Combined [Member] NMic and Re one Combined [Member] Ceding commission earned Reinsurance Ceding Commission Earned Reinsurance Ceding Commission Earned Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Fair value of long term debt Long-Term Debt, Fair Value Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Asset-backed securities Asset-backed securities Asset-Backed Securities [Member] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] 2018 Term loan Senior Secured Term Loan 2018 [Member] Senior Secured Term Loan 2018 [Member] Deferred income taxes Deferred Income Taxes and Tax Credits Amortization of debt discount and debt issuance costs Amortization of Debt Issuance Costs and Discounts Earnings per Share (EPS) Earnings Per Share [Text Block] Contingency reserve Statutory Accounting Practices, Contingency Reserve Contingency reserve recorded under Statutory Accounting Principles is a liability to protect against loss during periods of extreme contraction. Unrealized gains (losses) in accumulated other comprehensive income (loss), tax benefit OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Reinsurance coverage amount amortized (as a percent) Reinsurance Agreement, Optional Termination Right, Percent Of Reinsurance Coverage Threshold Reinsurance Agreement, Optional Termination Right, Percent Of Reinsurance Coverage Threshold Short-term investments Short-Term Investments [Member] Unrealized loss position, accumulated loss Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Entity Registrant Name Entity Registrant Name Premium receivable, allowance for credit loss, uncollected Premium Receivable, Allowance for Credit Loss, Writeoff Insurance [Abstract] Insurance [Abstract] Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Entity Address, City or Town Entity Address, City or Town Asset-backed securities Debt Securities, Available-for-Sale, Maturity, without Single Maturity Date, Fair Value Minimum Minimum [Member] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Commitments and Contingencies Disclosure [Abstract] Deferred policy acquisition costs, net Deferred Policy Acquisition Cost Treasury Stock, At Cost Treasury Stock, Common [Member] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Trading Symbol Trading Symbol Entity File Number Entity File Number Percent of premiums ceded under QSR Transaction Percent of pool RIF reinsured Reinsurance, Reinsured Risk, Percentage Shares repurchased, average price per share (in dollars per share) Treasury Stock Acquired, Average Cost Per Share 2020 Revolving credit facility Secured Revolving Credit Facility 2020 [Member] Secured Revolving Credit Facility 2020 Treasury stock, common shares (in shares) Treasury Stock, Common, Shares Ceded Credit Risk, Reinsurer [Domain] Reinsurer, Name [Domain] Repurchase of common stock (in shares) Treasury Stock Shares Acquired Cost Method Treasury Stock Shares Acquired Cost Method Diluted EPS Net Income (Loss) Available to Common Stockholders, Diluted, Operations [Abstract] Purchase of short-term investments Payments to Acquire Short-Term Investments Refund of Certain Mortgage Insurance Payments Refund of Certain Mortgage Insurance Payments [Member] Refund of Certain Mortgage Insurance Payments Schedule of statutory net income (loss), surplus, contingency reserve and risk-to-capital ratio Statutory Accounting Practices Disclosure [Table Text Block] Schedule of XOL transactions Schedule Of Respective Coverages And Retentions Of The XOL Transactions [Table Text Block] Schedule Of Respective Coverages And Retentions Of The XOL Transactions Debt Securities By Industry [Axis] Debt Securities By Industry [Axis] Debt Securities By Industry [Axis] 2021 Revolving credit facility Secured Revolving Credit Facility 2021 [Member] Secured Revolving Credit Facility 2021 Effective income tax rate on pre-tax income or loss Effective Income Tax Rate Reconciliation, Percent Investment Income, Net [Abstract] Investment Income, Net [Abstract] Cash, cash equivalents and short-term investments Cash and Cash Equivalents, Fair Value Disclosure Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Anticipated payment related to annual operating expenses Anticipated Operating Expense Payments, Annual Amount of anticipated payments related to operating expenses of counterparty. Total revenues Revenues Number of securities,12 months or greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Net investment income Investment Income, Net Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Schedule of net realized investment gains (losses) Realized Gain (Loss) on Investments [Table Text Block] Income Taxes Income Tax Disclosure [Text Block] Corporate debt securities as component of total (percent) Debt Securities, Corporate, Component Of Total. Percentage Debt Securities, Corporate, Component Of Total. Percentage Credit Facility [Domain] Credit Facility [Domain] Fair value, 12 months or greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Amortized Cost Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Rolling Maturity [Abstract] Basic (in dollars per share) Basic earnings per share (in dollars per share) Earnings Per Share, Basic Regulatory Information Insurance Disclosure [Text Block] Counterparty Name [Domain] Counterparty Name [Domain] Total shareholders' equity Beginning balance Ending balance Stockholders' Equity Attributable to Parent Statutory Accounting Practices [Line Items] Statutory Accounting Practices [Line Items] Entity Interactive Data Current Entity Interactive Data Current Ceded Ceded premiums earned Ceded Premiums Earned Reinsurance recoverable Reinsurance Recoverables, Gross Debt instrument covenant, maximum debt-to-total capitalization ratio Debt Instrument, Covenant Terms, Debt to Total Capitalization Ratio, Maximum Debt Instrument, Covenant Terms, Debt to Total Capitalization Ratio, Maximum Number of reinsurance engagements terminated Number of Reinsurance Engagements Terminated Number of Reinsurance Engagements Terminated Retained Earnings Retained Earnings [Member] Proceeds from maturity of short-term investments Proceeds from Sale of Short-Term Investments Common Stock - Class A Common Stock [Member] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Premiums receivable Premiums Receivable, Net Repurchases of common stock Payments for Repurchase of Common Stock Statement [Table] Statement [Table] Cash and investments held with various state insurance departments Cash, Cash Equivalents, and Short-Term Investments Effective interest rate (in percent) Debt Instrument, Interest Rate, Effective Percentage Initial First Layer Retained Loss Initial First Layer Retained Loss Initial First Layer Retained Loss Consumer Consumer, Industry Group [Member] Consumer, Industry Group [Member] Document Quarterly Report Document Quarterly Report Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits, by Title of Individual and by Type of Deferred Compensation [Table] Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-Based Payments and Postretirement Benefits, by Title of Individual and by Type of Deferred Compensation [Table] Deductible on policy Mortgage Pool Insurance, Claim Deductible Mortgage Pool Insurance, Claim Deductible Statistical Measurement [Axis] Statistical Measurement [Axis] Repurchased shares (in shares) Treasury Stock, Shares, Acquired Risk-in-Force of loans in pool past due 60 days or more Loans In Pool, Past Due 60 Days Or More, Loan Risk in Force Loans In Pool, Past Due 60 Days Or More, Risk in Force Retained earnings Retained Earnings (Accumulated Deficit) Prior to March 1, 2025 Prior To March 1, 2025 [Member] Prior To March 1, 2025 U.S. Treasury securities and obligations of U.S. government agencies U.S. Treasury securities and obligations of U.S. government agencies U.S. Treasury securities and obligations of U.S. government agencies US Treasury and Government [Member] Equity Components [Axis] Equity Components [Axis] Scenario [Domain] Scenario [Domain] Risk premiums paid Reinsurance Retention, Risk Premiums Paid Reinsurance Retention, Risk Premiums Paid Recurring Fair Value, Recurring [Member] Litigation Case [Domain] Litigation Case [Domain] Fair value, less than 12 months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Reclassification adjustment for realized gains (losses) included in net income, tax (benefit) expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Document Fiscal Year Focus Document Fiscal Year Focus Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Statement [Line Items] Statement [Line Items] Reserve for insurance claims and claim expenses Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Variable Rate [Domain] Variable Rate [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Technology Technology, Industry Group [Member] Technology, Industry Group [Member] Net premiums written Premiums Written, Net [Abstract] Prior year case reserves Prior Year Claims and Claims Adjustment Expense, Case Reserves Prior Year Claims and Claims Adjustment Expense, Case Reserves Gross unrealized losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Due after ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost Industrial Industrial, Industry Group [Member] Industrial, Industry Group [Member] Document Transition Report Document Transition Report Local Phone Number Local Phone Number Percent of premiums earned under 2018 QSR Transaction Premiums Earned, Percent Of Risk Premiums Earned, Percent Of Risk Recent Accounting Pronouncements - Adopted and Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Underwriting and operating expenses Other Cost and Expense, Operating Other assets Increase (Decrease) in Prepaid Expense and Other Assets Weighted average common shares outstanding Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Common stock, outstanding (in shares) Common Stock, Shares, Outstanding Premiums Receivable Premiums Receivable, Basis of Accounting, Policy [Policy Text Block] 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] Reinsurance funds withheld Funds Held under Reinsurance Agreements, Liability Income tax expense Income Tax Expense (Benefit) Debt Issuance costs Debt Issuance Costs, Line of Credit Arrangements, Gross Deferred tax liability, net Deferred Income Tax Liabilities, Net Deferred policy acquisition costs, net Increase (Decrease) in Deferred Policy Acquisition Costs Income Statement [Abstract] Income Statement [Abstract] Additional Paid-in Capital Additional Paid-in Capital [Member] Document Fiscal Period Focus Document Fiscal Period Focus Diluted (in shares) Dilutive weighted average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Remaining deferred issuance costs, net of accumulated amortization Debt Issuance Costs, Line of Credit Arrangements, Net Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Base rate Base Rate [Member] Debt issuance costs Debt Issuance Costs, Gross Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Risk-to-capital Risk To Capital Ratio Regulatory Actual This concept represents an entity's ratio of net risk in force (excludes risk ceded through reinsurance contracts and risk in force on defaulted loans) to the amount of statutory capital (defined as the sum of statutory policyholders' surplus plus statutory contingency reserves). Senior debt Senior Notes [Member] Other revenues Other Income Service expenses Other Nonoperating Expense Debt Securities By Industry [Line Items] Debt Securities By Industry [Line Items] Debt Securities By Industry [Line Items] Third-party reinsurers Third-Party Reinsurers [Member] Third-Party Reinsurers [Member] Cash and cash equivalents (including restricted cash of $2,197 and $2,176 as of March 31, 2023 and December 31, 2022, respectively) Cash, cash equivalents and restricted cash, beginning of period Cash, cash equivalents and restricted cash, end of period Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Schedule of effect of reinsurance agreements on premiums written and earned Effects of Reinsurance [Table Text Block] Litigation Commitments and Contingencies Disclosure [Text Block] Common stock, issued (in shares) Common Stock, Shares, Issued Current year case reserves Current Year Claims and Claims Adjustment Expense, Case Reserves Current Year Claims and Claims Adjustment Expense, Case Reserves 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] Number of securities, total Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Amendment Flag Amendment Flag Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Debt instrument face amount Debt Instrument, Face Amount Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] Deferred Compensation Arrangement with Individual, Excluding Share-Based Payments and Postretirement Benefits [Line Items] Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Litigation Case [Axis] Litigation Case [Axis] Proceeds from issuance of common stock related to employee equity plans Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Gross unrealized gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Entity Current Reporting Status Entity Current Reporting Status Statutory capital Statutory capital Statutory Accounting Practices, Statutory Capital and Surplus Including Contingency Reserve Statutory Accounting Practices, Statutory Capital and Surplus Including Contingency Reserve Ceded claims and claim expenses (benefits) Reinsurance Ceded Claims and Claims Expenses Reinsurance Ceded Claims and Claims Expenses Claims and claim expenses paid: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Commitment fee (in percent) Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Claims and Claims Adjustment Expense [Line Items] 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Stockholders' Equity Note Disclosure [Text Block] Senior secured notes Senior Notes Revenues Revenues [Abstract] Restricted cash Restricted Cash Number of loans in pool past due 60 days or more Loans In Pool, Past Due 60 Days Or More, Number Of Loans Loans In Pool, Past Due 60 Days Or More, Number Of Loans Percentage of ceding commission received Ceded Credit Risk, Commission Earned, Percentage Ceded Credit Risk, Commission Earned, Percentage Purchase of fixed-maturity investments, available-for-sale Payments to Acquire Debt Securities, Available-for-Sale Net premiums earned Net premiums earned Premiums Earned, Net Asset-backed securities Debt Securities, Available-for-Sale, Maturity, without Single Maturity Date, Amortized Cost Title of 12(b) Security Title of 12(b) Security Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Ceded Credit Risk, Reinsurer [Axis] Reinsurer, Name [Axis] Total bonds Bonds [Member] Total expenses Costs and Expenses Threshold for loss ratio on loans to qualify for profit commission Ceded Credit Risk, Profit Commission, Loss Ratio On Loans Threshold Ceded Credit Risk, Profit Commission, Loss Ratio On Loans Threshold Previously ceded primary risk-in-force recaptured Previously Ceded Primary Risk-In-Force Recaptured Previously Ceded Primary Risk-In-Force Recaptured Ceded Credit Risk [Table] Ceded Credit Risk [Table] Debt Instrument [Line Items] Debt Instrument [Line Items] Interest payable Interest Payable Unrealized losses, less than 12 months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Primary insured portfolio, loan default rate Primary Insured Portfolio, Loan Default Rate Primary Insured Portfolio, Loan Default Rate Reinsurance recoverable on unpaid claims Less reinsurance recoverables Add reinsurance recoverables Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments Loss contingency, number of cases Loss Contingency, 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In Force, Ceded Comprehensive income: Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Schedule of investments by maturity Investments Classified by Contractual Maturity Date [Table Text Block] Entity Filer Category Entity Filer Category Basic (in shares) Basic weighted average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Percentage of population with production prior to period start date Reinsurance Coverage, Percentage Of Population With Production Prior to Period Start Date Reinsurance Coverage, Percentage Of Population With Production Prior to Period Start Date Prior years Prior Year Claims and Claims Adjustment Expense Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans, Net of Shares For Tax Withholdings Stock Issued During Period, Shares, Employee Stock Purchase Plans, Net of Shares For Tax 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Cover [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Other assets Other Assets Number of claims paid Liability for Paid Claims and Claims Adjustment Expense, Number of Paid Claims Liability for Paid Claims and Claims Adjustment Expense, Number of Paid Claims Claims and claim expenses (benefits) incurred: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Net premiums written Premiums Written, Net Forecast Forecast [Member] Due after five through ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost Taxes paid related to net share settlement of equity awards Payment, Tax Withholding, Share-Based Payment Arrangement Total liabilities and shareholders' equity Liabilities and Equity Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Current Fiscal Year End Date Current Fiscal Year End Date Gross realized investment gains Debt Securities, Available-for-Sale, Realized Gain Diluted (in dollars per share) Diluted earnings per share (in dollars per share) Earnings Per Share, Diluted Communications Communications, Industry Group [Member] Communications, Industry Group [Member] Share-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Applicable premium Debt Instrument, Covenant Terms, Applicable Premium Debt Instrument, Covenant Terms, Applicable Premium Schedule of Available-for-sale Securities [Table] Schedule of Available-for-Sale Securities [Table] Beginning balance, net of reinsurance recoverables Reserve at end of period, net of reinsurance recoverables Liability for Unpaid Claims and Claims Adjustment Expense, Net Corporate debt securities Corporate debt securities Corporate Debt Securities [Member] Investment expenses Investment Income, Investment Expense Number of quota share reinsurance treaties Number of Quota Share Reinsurance Treaties Number of Quota Share Reinsurance Treaties Entity Address, Address Line One Entity Address, Address Line One Reinsurance Reinsurance [Text Block] Fannie Mae Fannie Mae [Member] Fannie Mae [Member] Ceded Ceded Premiums Written Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Total claims and claim expenses (benefits) incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Interest expense Interest Expense Credit Facility [Axis] Credit Facility [Axis] Unrealized gains (losses) in accumulated other comprehensive income (loss), net of tax expense (benefit) of $8,633 and $(26,176) for the quarters ended March 31, 2023 and 2022, respectively OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Equity [Abstract] Entity Tax Identification Number Entity Tax Identification Number Reserves for Insurance Claims and Claim Expenses Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] Reserve for prior year insurance claims and claim expenses Liability for Prior Year Claims and Claims Adjustment Expense Liability for Prior Year Claims and Claims Adjustment Expense Debt Securities By Industry [Domain] Debt Securities By Industry [Domain] [Domain] for Debt Securities By Industry [Axis] Premiums receivable Increase (Decrease) in Premiums Receivable Reinsurance Disclosures [Abstract] Reinsurance Disclosures [Abstract] Current Reinsurance Coverage Current Reinsurance Coverage Current Reinsurance Coverage Reinsurance Policy, Type [Axis] Reinsurance Contract [Axis] Net increase in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Commitment fees in interest expense Line of Credit Facility, Commitment Fee Amount Accrued investment income Accrued Investment Income Receivable Dilutive effect of issuable shares (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Entity Central Index Key Entity Central Index Key Measurement Frequency [Axis] Measurement Frequency [Axis] Number of days to be written off Premium Receivable, Number of Days to be Written Off Premium Receivable, Number of Days to be Written Off Reinsurance balances, net Increase (Decrease) in Reinsurance Assets and Liabilities Increase (Decrease) in Reinsurance Assets and Liabilities Entity [Domain] Entity [Domain] City Area Code City Area Code Assets Assets [Abstract] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Direct Direct Premiums Written Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Fair Value Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract] Initial Reinsurance Coverage Initial Reinsurance Coverage Initial Reinsurance Coverage Financial Financial, Industry Group [Member] Financial, Industry Group [Member] Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Profit commission Reinsurance Profit Commission Reinsurance Profit Commission Share-based compensation expense Share-Based Payment Arrangement, Noncash Expense Variable Rate [Axis] Variable Rate [Axis] Software and equipment Payments to Acquire Property, Plant, and Equipment Schedule of earnings per share, basic and diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Gross realized investment losses Debt Securities, Available-for-Sale, Realized Loss Unearned premiums Unearned Premiums Organization, Basis of Presentation and Summary of Accounting Principles Business Description and Basis of Presentation [Text Block]