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by Share-Based Payment Award, Options, Outstanding [Roll Forward] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Earnings (loss) per common share: basic (both Class A and B) (in dollars per share) Basic (in usd per share) Earnings Per Share, Basic Interest on deposits and cash equivalents Cash and Cash Equivalents [Member] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Net income (loss) attributable to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Schedule of Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Redeemable convertible preferred stock, $0.0001 par value, 100.0 shares authorized, 14.1 shares issued and outstanding at September 30, 2024 and December 31, 2023 (redemption value of $126.5) Beginning balance Ending balance Temporary Equity, Carrying Amount, Attributable to Parent Unrecognized compensation cost, options Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Total assets Assets RSUs and PSUs Phantom Share Units PSUs and Restricted Stock Units RSU [Member] Phantom Share Units PSUs and Restricted Stock Units RSU Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period U.S. Treasury securities and agencies US Treasury and Government [Member] Purchases of fixed assets Payments to Acquire Property, Plant, and Equipment Entity Listings [Line Items] Entity Listings [Line Items] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Commitments and Contingencies (Note 11) Commitments and Contingencies Termination Date Trading Arrangement Termination Date Class of Warrant or Right [Domain] Class of Warrant or Right [Domain] NATURE OF BUSINESS Nature of Operations [Text Block] Assumed Assumed Premiums Written BBB+, BBB, BBB- Standard & Poor's, BBB Plus, BBB, BBB Minus Rating [Member] Standard & Poor's, BBB Plus, BBB, BBB Minus Rating Total revenues Revenues SHARE-BASED COMPENSATION Share-Based Payment Arrangement [Text Block] Other liabilities Other Liabilities Pennsylvania PENNSYLVANIA Schedule of Credit Ratings Fair Value, Concentration of Risk [Table Text Block] Entity Address, City or Town Entity Address, City or Town Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One 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Address, Address Line One Extinguishment of debt, amount Extinguishment of Debt, Amount Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Entity Address, Address Line Two Entity Address, Address Line Two Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Total assets at fair value Assets, Fair Value Disclosure Name Forgone Recovery, Individual Name Document Period End Date Document Period End Date Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Beginning balance (in shares) Ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Insider Trading Arrangements [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Short Term Warrant Short Term Warrant [Member] Short Term Warrant PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Adjustment to Compensation: Adjustment to Compensation [Axis] Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items] Document Transition Report Document Transition Report Document Quarterly Report Document Quarterly Report Current year Current Year Claims and Claims Adjustment Expense Due after one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Nonvested shares subject to repurchase Nonvested Shares Subject To Repurchase [Member] Nonvested Shares Subject To Repurchase Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Current Reporting Status Entity Current Reporting Status Accumulated Loss Retained Earnings [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Ohio OHIO Redeemable convertible preferred stock (as converted to common stock) Redeemable Convertible Preferred Stock [Member] Realized gain value Gross Investment Income, Operating Weighted-average common shares outstanding: basic (both Class A and B) (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Net premiums earned Net premiums earned Premiums Earned, Net 12 months or more, unrealized loss Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Restricted stock unit expense Restricted stock unit expense RSUs and PSUs Restricted Stock Units (RSUs) [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name Less than 12 months, unrealized loss Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Loss and loss adjustment expense reserves Liability For Claims And Claims Adjustment Expense, Gross Liability For Claims And Claims Adjustment Expense, Gross Entity Filer Category Entity Filer Category Restructuring liability, beginning balance Restructuring liability, ending balance Restructuring Reserve Fee income Fee Income Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Purchases of investments Payments to Acquire Debt Securities, Available-for-Sale Company Selected Measure Name Company Selected Measure Name