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[Member] Total claims and claim expenses paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Income Tax Jurisdiction [Axis] Income Tax Jurisdiction [Axis] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Income Statement [Abstract] Income Statement [Abstract] Cash and cash equivalents (including restricted cash of $0 and $90) Cash, cash equivalents and restricted cash, beginning of period Cash, cash equivalents and restricted cash, end of period Cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Fair value, 12 months or greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Net premiums written Premiums Written, Net [Abstract] Product and Service [Domain] Product and Service [Domain] Reinsurance coverage amount amortized (in percent) Reinsurance Agreement, Optional Termination Right, Percent Of Reinsurance 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Notes Restatement Determination Date: Restatement Determination Date [Axis] 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 Name Trading Arrangement, Individual Name State licenses State Licenses [Member] State Licenses [Member] 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). 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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 Segment Reporting [Abstract] Operating lease expense Operating Lease, Expense Debt Disclosure [Abstract] Debt Disclosure [Abstract] 2027 XOL Transaction 2027 XOL Transaction [Member] 2027 XOL Transaction Scenario [Domain] Scenario [Domain] Expenses Costs and Expenses [Abstract] SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Axis] Net realized investment (gains) losses Net realized investment gains (losses) Net realized investment losses (gains) Debt Securities, Available-for-Sale, Realized Gain (Loss) Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Consolidated Entities [Axis] Consolidated Entities [Axis] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Options granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross 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 Use of Estimates Use of Estimates, Policy [Policy Text Block] Reinsurance balances, net Increase (Decrease) in Reinsurance Assets and Liabilities Increase (Decrease) in Reinsurance Assets and Liabilities Schedule of fair value measurements of financial instruments Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Insider Trading Arrangements [Line Items] Options forfeited (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price 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). Reinsurance recoverable Increase (Decrease) in Reinsurance Recoverable Investment income Interest revenue Investment Income, Interest and Dividend Total liabilities Liabilities Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Initial Reinsurance Coverage Initial Reinsurance Coverage Initial Reinsurance Coverage Net investment income Investment Income, Net Financial Financial, Industry Group [Member] Financial, Industry Group [Member] Common stock - $0.01 par value; 88,371,465 shares issued and 76,285,242 shares outstanding as of December 31, 2025 and 87,902,626 shares issued and 78,600,726 shares outstanding as of December 31, 2024 (250,000,000 shares authorized) Common Stock, Value, Outstanding Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Proceeds from maturities and redemptions of fixed-maturity investments, available-for-sale Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Asset-backed securities Asset-Backed Securities [Member] Variable Rate [Axis] Variable Rate [Axis] Counterparty Name [Axis] Counterparty Name [Axis] Schedule of restricted stock units activity Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Proceeds from maturities and redemptions of fixed-maturity investments, available-for-sale Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities Fixed maturities, available-for-sale, at fair value (amortized cost of $3,190,174 and $2,876,343) Fair Value Fair Value Amount Reflected on Balance Sheet Debt Securities, Available-for-Sale Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Corporate debt securities Corporate Debt Securities [Member]