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of Stock [Domain] Class of Stock [Domain] Fannie Mae Fannie Mae [Member] Fannie Mae [Member] Ceded Ceded Premiums Written Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Total claims and claim (benefits) expenses incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Interest expense Interest Expense Options vested aggregate value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value Credit Facility [Axis] Credit Facility [Axis] Unrealized (losses) gains in accumulated other comprehensive income, net of tax (benefit) expense of $(54,608), $(13,768) and $9,525 for each of the years in the three-year period ended December 31, 2022, respectively Unrealized (losses) gains in accumulated other comprehensive income, net of tax (benefit) expense of $(748), $(95), and $25 for each of the years in the three-year period ended December 31, 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 Contribution amount Defined Contribution Plan, Employer Discretionary Contribution Amount Shareholders' equity Equity [Abstract] Restricted stock units vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Entity Tax Identification Number Entity Tax Identification Number Number of shares authorized to be reserved for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Reserves for Insurance Claims and Claim Expenses Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] Dividends, restriction with regards to capital surplus (in percent) Ordinary Dividends, Restriction with Regards to Capital Surplus This concept represents the maximum percentage of surplus as of the prior year that an insurer may pay out in ordinary dividends without prior approval of the Wisconsin Office of the Commissioner of Insurance under Wisconsin law. Reserve for prior year insurance claims and claims expense Liability for Prior Year Claims and Claims Adjustment Expense Liability for Prior Year Claims and Claims Adjustment Expense Premiums receivable Increase (Decrease) in Premiums Receivable Income Tax Authority, Name [Domain] Income Tax Authority, Name [Domain] Reinsurance Disclosures [Abstract] Reinsurance Disclosures [Abstract] Current Reinsurance Coverage Current Reinsurance Coverage Current Reinsurance Coverage Total deferred tax liability Deferred Tax Liabilities, Gross Consolidated Entities [Domain] Consolidated Entities [Domain] Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information Disclosure [Abstract] Year 8 Short-Duration Insurance Contracts, Historical Claims Duration, Year Eight Reinsurance Policy, Type [Axis] Reinsurance Contract [Axis] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Schedule of effective income tax rate reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Net (decrease) 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 Year 1 Short-Duration Insurance Contracts, Historical Claims Duration, Year One Dilutive effect of issuable shares (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Entity Central Index Key Entity Central Index Key Short-duration Insurance Contracts, Accident Year [Axis] Short-Duration Insurance Contracts, Accident Year [Axis] Measurement Frequency [Axis] Measurement Frequency [Axis] Weighted Average Grant Date Fair Value per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Name of Property [Axis] Name of Property [Axis] Average annual percentage payout of incurred claims and allocated claims adjustment expenses by age, net of reinsurance Short-Duration Insurance Contracts, Historical Claims Duration [Line Items] Premium receivable, 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 Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Schedule of ILN transactions Schedule of Respective Coverages and Retentions 0f the ILN Transactions [Table Text Block] Schedule of respective coverages and retentions of the ILN transactions [Table Text Block] Reinsurance balances, net Increase (Decrease) in Reinsurance Assets and Liabilities Increase (Decrease) in Reinsurance Assets and Liabilities Measurement Input Type [Axis] Measurement Input Type [Axis] Entity [Domain] Entity [Domain] City Area Code City Area Code Assets Assets [Abstract] Mortgage insurance risk in force Mortgage Insurance Risk in Force This concept represents the risk in force (an estimate of the maximum loss exposure that an entity has at any point in time). Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Ordinary course dividend paid Payments of Ordinary Dividends Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] Short-Duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] 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] Fair Value SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Fair Value 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 (EPS) 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 Options granted (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Variable Rate [Axis] Variable Rate [Axis] Class of warrant or right, outstanding (in shares) Class of Warrant or Right, Outstanding Equity in net income of subsidiaries Income (Loss) from Equity Method Investments 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] Options forfeited (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value Gross realized investment losses Debt Securities, Available-for-Sale, Realized Loss Unearned premiums Unearned Premiums Capitalization of subsidiaries Payments to Acquire Interest in Subsidiaries and Affiliates Organization and Basis of Presentation Business Description and Basis of Presentation [Text Block]