OtherThanTemporaryImpairmentLossesCreditLossesOtherInvestmentsDebtSecuritiesSaleOfSubsidiaryRecognizedInEarnings OtherThanTemporaryImpairmentLossesCreditLossesOtherInvestmentsDebtSecuritiesSaleOfSubsidiaryRecognizedInEarnings OtherThanTemporaryImpairmentLossesCreditLossesOtherInvestmentsDebtSecuritiesSaleOfSubsidiaryRecognizedInEarnings Maximum [Member] Maximum [Member] OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Statistical Measurement [Domain] Statistical Measurement [Domain] Title of 12(b) Security Title of 12(b) Security Subsequent Event Subsequent Event [Member] Debt Securities, Available-for-Sale [Table] Debt Securities, Available-for-Sale [Table] Document Fiscal Year Focus Document Fiscal Year Focus Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Debt, Weighted Average Interest Rate Debt, Weighted Average Interest Rate Net reserve increase (decrease) Net Reserve Increase (Decrease) Net Reserve Increase (Decrease) Financial Instrument [Axis] Financial Instrument [Axis] Reinsurance recoverable for loss and loss adjustment expense reserves Reinsurance recoverable for loss and loss adjustment expense reserves Reinsurance recoverable for loss and loss adjustment expense reserves Segment Reporting [Abstract] Segment Reporting [Abstract] Fair Value, Assets Measured on Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Common stock Common Stock, Value, Issued Interest - other Interest Expense, Operating and Nonoperating Schedule of Debt Schedule of Long-Term Debt Instruments [Table Text Block] Underwriting, acquisition, and other expenses Underwriting Acquisition And Other Expenses Underwriting Acquisition And Other Expenses Costs incurred during the period for underwriting, acquisition and other expenses. Other-than-Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment Other-than-Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment Other-than-Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment Accounts Receivable, Allowance for Credit Loss Accounts Receivable, Allowance for Credit Loss Current Current Income Tax Expense (Benefit) Amendment Flag Amendment Flag Consolidated Entities [Axis] Consolidated Entities [Axis] Treasury Stock Acquired, Average Cost Per Share Shares Acquired, Average Cost Per Share Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Net investment income Net Investment Income, Total Net Investment Income Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Investment Investment [Text Block] Taxes and Licenses Taxes and Licenses Investment Income, Categories [Domain] Investments [Domain] Debt Instrument, Maturity Date Debt Instrument, Maturity Date Consolidated Entities [Domain] Consolidated Entities [Domain] Increase in cash balances classified as held-for-sale Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation [Abstract] Entity Address, State or Province Entity Address, State or Province Available for sale, Unrealized Losses, Total Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Payments to Acquire Equity Securities, FV-NI Payments to Acquire Equity Securities, FV-NI Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Exchange [Domain] Exchange [Domain] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Average shares outstanding: Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Number of Reportable Segments Number of Reportable Segments Deferred policy acquisition costs Increase (Decrease) in Deferred Policy Acquisition Costs Investments: Investments [Abstract] Available for sale, Due after five years through ten years (estimated fair value) Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Entity Address, City or Town Entity Address, City or Town Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Income taxes (credits) on above Income taxes (credits) on above Income taxes (credits) on above Basis of Accounting, Policy Basis of Accounting, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Other than Securities Investment Other than Securities Investment [Member] Dividend reinvestment plan Stock Issued During Period, Value, Dividend Reinvestment Plan Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Net of Tax Segment Reporting, Reconciliation of Asset by Segment to Consolidated Segment Reporting, Reconciliation of Asset by Segment to Consolidated [Table Text Block] Senior Notes Due 2051 Senior Notes Due 2051 [Member] Senior Notes Due 2051 Realized Investment Gains Losses From Impairment Realized Investment Gains Losses From Impairment Realized Investment Gains Losses From Impairment The net realized gains or losses on impairments of investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. Loss ratio point impact from prior year unfavorable reserve development Loss ratio point impact from prior year unfavorable reserve development Loss ratio point impact from prior year unfavorable reserve development Subsequent Event Type [Axis] Subsequent Event Type [Axis] Adjustments to Additional Paid in Capital, Other Adjustments to Additional Paid in Capital, Other Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Investment expenses Investment Income, Investment Expense Treasury Stock (at cost) Treasury Stock, Value New Accounting Pronouncements, Policy New Accounting Pronouncements, Policy [Policy Text Block] Financial Indemnity - Transactional Risk Business Financial Indemnity - Transactional Risk Business [Member] Financial Indemnity - Transactional Risk Business Contract Revenue - Claims Handling and Related Ancillary Services Contract Revenue - Claims Handling and Related Ancillary Services Contract Revenue - Claims Handling and Related Ancillary Services Schedule of Segment Reporting Segment Reporting [Table Text Block] Noncontrolling Interest Noncontrolling Interest [Member] Unearned premiums and other policyholders' liabilities Increase (Decrease) in Other Policyholder Funds Senior Notes Due 2024 Senior Notes Due 2024 [Member] Senior Notes Due 2024 [Member] Available for sale, Due after one year through five years (estimated fair value) Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Document Period End Date Document Period End Date Commercial auto net premiums earned, percentage Commercial auto net premiums earned, percentage Commercial auto net premiums earned, percentage Total Cash Provided by (Used in) Investing Activity, Including Discontinued Operation RMIC and RMICNC [Member] Subsidiaries [Member] Preferred Stock, outstanding shares (in shares) Preferred Stock, Shares Outstanding Debt Debt Instrument, Face Amount Debt Instrument, Face Amount Number of major segments Number of major segments The number of regulated insurance company subsidiaries organized into major segments, namely its General Insurance (property and liability insurance), Mortgage Guaranty and Title Insurance Groups. Security Exchange Name Security Exchange Name Debt Securities, Available-for-sale, Realized Loss Debt Securities, Available-for-Sale, Realized Loss Losses, Claims and Settlement Expenses Insurance Disclosure [Text Block] Available for sale, Due after ten years (amortized cost) Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Increase (Decrease) in Debt Securities, Trading, and Equity Securities, FV-NI Increase (Decrease) in Debt Securities, Trading, and Equity Securities, FV-NI Equity securities, gross unrealized losses Equity securities, gross unrealized losses This item represents the gross unrealized losses for equity securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities. Accounting Standards Pending Adoption Accounting Standards Pending Adoption [Policy Text Block] Accounting Standards Pending Adoption Non-insurance Contract Title Services Non-insurance Contract Title Services Non-insurance Contract Title Services Common Class B [Member] Common Class B [Member] Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Common Share Data Earnings Per Share [Text Block] Net Income Per Share: Earnings Per Share [Abstract] Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Equity securities, gross realized losses Available-for-sale And Trading Securities, Gross Realized Losses Available-for-sale And Trading Securities, Gross Realized Losses Total liabilities Liabilities Trading Symbol Trading Symbol Consolidation, Variable Interest Entity, Policy Consolidation, Variable Interest Entity, Policy [Policy Text Block] Fixed income securities Payments to Acquire Debt Securities, Available-for-Sale Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Net changes in unrealized investment gains (losses) OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Other investments Payments to Acquire Other Investments Income Taxes Credits On Realized Investment Gains Losses Income tax expense (credits) on consolidated net realized investment gains (losses) Income Taxes Credits On Realized Investment Gains Losses Income taxes (credits) reflecting primarily the combination of fully taxable realized investment gains or losses during the period and judgments about the recoverability of deferred tax assets. Consolidated Statements of Preferred Stockand Common Shareholders' Equity [Abstract] Consolidated Statements of Preferred Stockand Common Shareholders' Equity [Abstract] Consolidated Statements of Preferred Stockand Common Shareholders' Equity [Abstract] Equity securities - cost Equity Securities, FV-NI, Cost ESSOP shares released Amortization of ESOP Award Fixed Income Securities [Member] Debt Securities [Member] Current year estimated coverage rescissions and claims denials Increase (Decrease) in Loss and Loss Adjustment Expense Reserve, Current Year Increase (Decrease) in Loss and Loss Adjustment Expense Reserve, Current Year Loss and loss adjustment expense reserves Gross reserves at beginning of period Gross reserves at end of period Liability for Claims and Claims Adjustment Expense SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Table] SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Table] Cash flows from operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Weighted Average Number of Shares Outstanding, Diluted, Total Weighted Average Number of Shares Outstanding, Diluted Dividends on common share (in usd per share) Common Stock, Dividends, Per Share, Cash Paid Entity Emerging Growth Company Entity Emerging Growth Company Credit Loss [Abstract] Other long-term investments [Member] Equity securities & other long-term investments [Member] This category includes information about ownership interests or the right to acquire ownership interests in corporations and other legal entities which ownership interest is represented by shares of common or preferred stock (which is neither mandatorily redeemable no redeemable at the option of the holder), convertible securities, stock rights, or stock warrants, as well as other investments. Investment Income Investment Income [Table Text Block] Specialty Insurance Group Specialty Insurance Group [Member] Segment in which the financial information pertaining to insurance coverages for general insurance provided by the entity. Entities [Table] Entities [Table] Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain (Loss), before Tax Net income excluding investment gains (losses) Net income excluding investment gains (losses) Net income excluding investment gains (losses) Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Accrued investment income Accrued Investment Income Receivable Treasury Stock, Common Treasury Stock, Common [Member] Reinsurance recoverable: Paid loss and loss adjustment expenses Reinsurance Recoverable for Paid Claims and Claims Adjustments ESSOP Debt ESSOP Debt [Member] Debt entered into to finance common stock purchases acquired by the Employees Savings and Stock Ownership Plan. The debt includes a bank loan and pre-fundings from ESSOP participating subsidiaries. Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Stock based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Loss and loss adjustment expenses Policyholder Benefits and Claims Incurred, Net Policyholder Benefits and Claims Incurred, Net Debt Debt and Lease Obligation Debt and Lease Obligation Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Net reserves at beginning of period Liability for Unpaid Claims and Claims Adjustment Expense, Net Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Available for sale Debt Securities, Available-for-Sale [Abstract] Insurance Premiums Revenue Recognition, Policy Insurance Premiums Revenue Recognition, Policy [Policy Text Block] Net reserves for claims that have been incurred but are not yet reported Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Description Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Description General Liability General Liability [Member] Noncontrolling Interests Noncontrolling Interests [Policy Text Block] Noncontrolling Interests Preferred Stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities [Axis] Scenario [Domain] Scenario [Domain] Amortized Cost and Estimated Fair Values Of Fixed Income Securities Amortized Cost and Estimated Fair Values Of Fixed Maturities [Table Text Block] Tabular disclosure of fixed maturities securities indicating amortized cost, gross unrealized gains, gross unrealized losses and estimated fair value by securitiy classification. [Table Text Block] Available for sale, Due in one year or less (amortized cost) Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Schedule of Calculation of Numerator and Denominator in Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Unallocated 401(k) plan shares (at cost) Unallocated ESSOP Shares Common shares owned by the Company's Employee Savings and Stock Ownership Plan that are as yet unallocated to participants in the plan. Investment gains (losses) - other investments Investment gains (losses) - other long-term investments Investment gains (losses) - other long-term investments Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Amount of reserves for unpaid claims and claim adjustment expenses at the end of each period, net of reinsurance losses recoverable Liability for Unpaid Claims and Claims Adjustment Expense, Net of Reinsurance Losses Recoverable Liability for Unpaid Claims and Claims Adjustment Expense, Net of Reinsurance Losses Recoverable Foreign currency translation adjustment and other Foreign currency translation adjustment and other Foreign currency translation adjustment and other Information About Segments of Business Segment Reporting [Text Block] Maturities and calls of fixed income securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Dividends to policyholders Policyholder Dividends, Expense Schedule of Investment Income, Reported Amounts, by Category [Axis] Investment Type [Axis] Dividends on common shares Payments of Ordinary Dividends, Common Stock Redemption of debentures and notes Repayments of Other Debt Reinsurance balances and funds held Reinsurance Balances And Funds Held The element represents the carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements and the amount of funds held by the ceding insurer on behalf of the reinsurer, including funds held in trust, under reinsurance treaties or contracts with the assuming insurer as security for the payment of the obligations thereunder. Liabilities and Common Shareholders' Equity Liabilities: Liabilities [Abstract] Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Balance Balance Equity, Including Portion Attributable to Noncontrolling Interest March 1, 2024 Authorization March 1, 2024 Authorization [Member] March 1, 2024 Authorization Net investment income and other income Net investment income and other income Total amount of investment income and other income. Net investments income may include income earned from investments in securities and property, equipment and other capital assets. Other income pertains to the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement. Other liabilities Other Liabilities Issuance of common shares Proceeds from Issuance of Common Stock Common Stock, authorized shares (in shares) Common Stock, Shares Authorized August 19, 2025 Authorization [Member] August 19, 2025 Authorization [Member] August 19, 2025 Authorization Antidilutive Security, Excluded EPS Calculation [Table] Antidilutive Security, Excluded EPS Calculation [Table] Debt Securities, Available-for-sale, Realized Gain Debt Securities, Available-for-Sale, Realized Gain Available for sale, Due after ten years (estimated fair value) Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Segment Reporting Segment Reporting [Line Items] Share Repurchase Program, Authorized, Amount Share Repurchase Program, Authorized, Amount Document Quarterly Report Document Quarterly Report Segments [Domain] Segments [Domain] Municipal [Member] US States and Political Subdivisions Debt Securities [Member] Income (loss) before income taxes (credits) and realized investment gains or losses Income (loss) before income taxes (credits) and realized investment gains or losses Sum of operating profit and nonoperating income or expense before income taxes (credits) and realized investment gains or losses. Proceeds from Divestiture of Interest in Consolidated Subsidiaries Proceeds from Divestiture of Interest in Consolidated Subsidiaries Fixed income securities Proceeds from Sale of Debt Securities, Available-for-Sale Debt Debt Disclosure [Text Block] Claims and claim adjustment expenses attributable to insured events of prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Sales of: Cash Flows From Investing Activities Sales [Abstract] Scenario [Axis] Scenario [Axis] Preferred Stock Convertible Preferred Stock [Member] Equity Component [Domain] Equity Component [Domain] Deferred policy acquisition costs Deferred Policy Acquisition Cost Expenses: Benefits, Losses and Expenses [Abstract] Equity securities, net realized gains (losses) Available-for-sale And Trading Securities, Net Realized Gains (Losses) Available-for-sale And Trading Securities, Net Realized Gains (Losses) Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Dividends on common stock Dividends, Common Stock, Cash Total equity Stockholders' Equity Attributable to Parent Equity, Attributable to Parent Consolidated Balance Sheet Parenthetical [Abstract] Consolidated Balance Sheet Parenthetical [Abstract] Consolidated Balance Sheet Parenthetical [Abstract] Entity Listings, Exchange [Axis] Entity Listings, Exchange [Axis] Equity securities (at fair value) (cost: $1,318.2 and $1,377.7) Equity securities Equity Securities, FV-NI, Current Business Combination, Consideration Transferred, Equity Interest, Share Issued, Number of Shares Business Combination, Consideration Transferred, Equity Interest, Share Issued, Number of Shares Commercial Automobile Commercial Automobile [Member] Commercial Automobile [Member] Other investments Other Investments Accounting Policies [Abstract] Accounting Policies [Abstract] Fixed income securities (amortized costs) Fixed income securities (amortized cost) Debt Securities, Available-for-Sale, Amortized Cost Fair Value, Debt Measured on Recurring Basis Fair Value, Debt Measured on Recurring Basis [Table Text Block] Fair Value, Debt Measured on Recurring Basis [Table Text Block] Other Miscellaneous Debt Other Miscellaneous Debt Other Miscellaneous Debt Treasury Stock Treasury Stock [Text Block] Repurchase of common stock Proceeds from (Payment for) Other Financing Activity Cumulative Effect, Period of Adoption, Adjusted Balance Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Other investments Proceeds from Sale and Maturity of Other Investments Tax Cut and Jobs Act Remeasurement Tax Cut and Jobs Act Remeasurement Amount of reasonable estimate for remeasurement of deferred tax assets from change in tax laws pursuant to the Tax Cuts and Jobs Act for which accounting for tax effect is incomplete. Deferred Deferred Income Tax Expense (Benefit) SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items] SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items] Claims and claim adjustment expenses attributable to insured events of the current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Total incurred claims and claim adjustment expenses Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Business Combination [Domain] Business Combination [Domain] Gain (Loss) on Investments, Including Marketable Securities and Investments Held at Cost, Categories of Investments [Domain] Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Commitments and Contingent Liabilities Commitments and Contingencies Disclosure [Text Block] Number of major segments Number of Operating Segments Antidilutive common stock equivalents excluded from earnings per share computations Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Entity Central Index Key Entity Central Index Key Additional paid-in capital Additional Paid in Capital, Common Stock Segment Reporting, Reconciling Item, Corporate Nonsegment Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Business Combination [Axis] Business Combination [Axis] Common Shareholders' Equity: Equity [Abstract] Total Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Title Premium And Fee Revenues Stemming From Direct Operations Title Premium And Fee Revenues Stemming From Direct Operations Title premium and fee revenues stemming from direct operations Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Change in provision for insured events of prior years Prior Year Claims and Claims Adjustment Expense Title Insurance Title Insurance Group [Member] Title Insurance Group Stockholders' Equity, Other Stockholders' Equity, Other Income Statement [Abstract] Income Statement [Abstract] Shareholders' Equity: Equity, Attributable to Parent [Abstract] Document Transition Report Document Transition Report Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Total realized and unrealized investment gains (losses) Gain (Loss) on Investments Gain (Loss) on Investments Reinsurance Accounting Policy Reinsurance Accounting Policy [Policy Text Block] Cash Provided by (Used in) Discontinued Operation Cash Provided by (Used in) Discontinued Operation Deferred Income Tax Assets, Net Deferred Income Tax Assets, Net Senior Notes Due 2036 Senior Notes Due 2036 [Member] Senior Notes Due 2036 Intersegment Elimination [Member] Intersegment Eliminations [Member] Less: Reinsurance losses recoverable Reinsurance Recoverables, Including Reinsurance Premium Paid Other miscellaneous debt Other Miscellaneous Debt [Member] Other Miscellaneous Debt Debt and Equity Securities, Realized Gain (Loss), Excluding Other-than-temporary Impairment Debt and Equity Securities, Realized Gain (Loss), Excluding Other-than-temporary Impairment City Area Code City Area Code AOCI Attributable to Parent AOCI Attributable to Parent [Member] Convertible senior notes [Member] Convertible Debt Securities [Member] Subsequent Events Subsequent Events [Text Block] Fair value Debt Instrument, Fair Value Disclosure Equity Securities Reflecting Reported Cost Equity Securities Reflecting Reported Adjusted Cost, Net Of OTTI [Table Text Block] Tabular disclosure of equity securities indicating adjusted costs, net of other-than-temporary-impairments, gross unrealized gains, gross unrealized losses and estimated fair value. [Table Text Block] Specialty Insurance Specialty Insurance Segment [Member] General Insurance Segment [Member] Statement [Line Items] Consolidated Statements of Comprehensive Income Statement [Line Items] Assets Assets Entity [Domain] Entity [Domain] Schedule of Fixed Income Securities Securities [Table] [Table] Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Table] Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Table] Total policy liabilities Total policy liabilities and accruals The total liability as of the balance sheet date of the amounts established as reserves for losses, loss adjustment expenses, unearned premiums, and other policyhholders' benefits and funds. Total Company Segments [Member] Operating Segments [Member] Amounts reclassified as realized investment gains from sales in the statements of income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Net increase in short-term investments Payments for (Proceeds from) Short-Term Investments Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale Other-than-temporary Impairment Loss, Debt Securities, Available-for-Sale Amortized Cost and Estimated Fair Values Of Fixed Income Securities By Contractual Maturities Amortized Cost and Estimated Fair Values Of Fixed Maturities By Contractual Maturities [Table Text Block] Tabular disclosure of fixed maturities securities indicating amortized cost and estimated fair value by contractual obligation. [Table Text Block] NEW YORK STOCK EXCHANGE, INC. [Member] NEW YORK STOCK EXCHANGE, INC. [Member] Credit Loss, Financial Instrument Credit Loss, Financial Instrument [Text Block] Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Total investments Investments Non-insurance Contract Revenue Non-insurance Contract Revenue Non-insurance Contract Revenue Unrealized gains (losses) on securities before reclassifications, not included in the statements of income OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment and Tax Available for sale, Due in one year or less (estimated fair value) Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings Retained Earnings [Member] Taxes Payable, Current Taxes Payable, Current Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Net unrealized gains (losses) on securities not included in the statements of income, net of tax Net unrealized gains (losses) on securities, net of tax OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Common Stock, Shares, Outstanding Common Stock, Shares, Outstanding Corporate [Member] Corporate Debt Securities [Member] Net income (loss) per share: Diluted (in dollars per share) Earnings Per Share, Diluted Entity Current Reporting Status Entity Current Reporting Status Total Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Unrealized Gain (Loss) on Investments Unrealized Gain (Loss) on Investments Preferred Stock Preferred Stock, Value, Outstanding Adjustment for interest expense incurred on assumed conversions of convertible notes Interest on Convertible Debt, Net of Tax Adjustments to reconcile net income to Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Treasury Stock Treasury Stock [Policy Text Block] Treasury Stock Premiums Written, Net Premiums Written, Net Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Financial Instruments [Domain] Financial Instruments [Domain] Unearned premium and policy reserves Unearned premium and policy reserves Unearned premium and policy reserves Other income Other Income Title, escrow, and other fees Title Escrow And Other Fees Total fees earned during the period from providing title, escrow, closing, and other real estate related services. Other Comprehensive Income (Loss), before Tax, Portion Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Equity securities, gross realized gains Available-for-sale And Trading Securities, Gross Realized Gains Available-for-sale And Trading Securities, Gross Realized Gains Cash Cash Hurricane-related claim costs Hurricane-related claim costs Hurricane-related claim costs Preferred Stock Preferred Stock [Member] Other – net Payment for (Proceeds from) Other Investing Activity Debt Conversion, Converted Instrument, Shares Issued Debt Conversion, Converted Instrument, Shares Issued Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Percentage of total contract revenue percentage of total contract revenue percentage of total contract revenue Senior Notes Due 2034 Senior Notes Due 2034 [Member] Senior Notes Due 2034 Common Share Repurchases Common Share Repurchases, Policy [Policy Text Block] Common Share Repurchases, Policy Accounts and notes receivable Premiums and Other Receivables, Net Segment Reporting [Table] Segment Reporting [Table] Pretax unrealized gains (losses) on investments not included in the statements of income Changes in unrealized investment gains (losses) on investments OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax Income Taxes (Credits): Consolidated Income Tax Expense (Credits) [Abstract] Income Tax Expense (Benefit), Continuing Operations [Abstract] Specialty Insurance Group [Member] General Insurance Group [Member] Segment in which the financial information pertaining to insurance coverages for general insurance provided by the entity. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Current Fiscal Year End Date Current Fiscal Year End Date Realized Investment Gains Losses From Sales Realized Investment Gains Losses From Sales The net realized gains or losses on sales of investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. Proceeds from Issuance of Debt Proceeds from Issuance of Debt Other Corporate & Other [Member] Corporate & Other [Member] Statement [Table] Revenue Recognition - Statement Table [Table] Revenue Recognition - Statement Table Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Entity File Number Entity File Number Net issuance of shares under stock based compensation plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Equity Securities [Member] Equity Securities [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Additional Paid-in Capital Additional Paid-in Capital [Policy Text Block] Additional Paid-in Capital Common Stock, issued shares (in shares) Common Stock, Shares, Issued Entity Information [Line Items] Entity Information [Line Items] Gross Unrealized Losses and Fair Value, Aggregated Gross Unrealized Losses and Fair Value, Aggregated [Table Text Block] Tabular disclosure fixed maturity and equity securities indicating fair value and corresponding unrealized losses by length of time that individual securities have been in an unrealized loss positions by securitiy classification. [Table Text Block] Treasury Stock, Common, Shares Treasury Stock, Common, Shares Equity Issued in Business Combination, Fair Value Disclosure Equity Issued in Business Combination, Fair Value Disclosure Net premiums earned Premiums Earned, Net Premiums Earned, Net Consolidated Income (Loss) Before Taxes (Credits) [Abstract] Consolidated Income (Loss) Before Taxes (Credits) [Abstract] Debt Securities, Available-for-sale, Allowance for Credit Loss Debt Securities, Available-for-Sale, Allowance for Credit Loss Available for sale, Unrealized Losses, 12 Months or Greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Equity Components [Axis] Equity Components [Axis] Net Unrealized Gains Losses Recognized from Changes in Fair Value of Equity Securities Held Net Unrealized Gains Losses Recognized from Changes in Fair Value of Equity Securities Held Net Unrealized Gains Losses Recognized from Changes in Fair Value of Equity Securities Held Reinsurance Premiums for Insurance Companies, by Product Segment [Domain] Product and Service [Domain] Cash paid (received) during the period for: Income taxes Income Tax Paid, after Refund Received Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Entity Interactive Data Current Entity Interactive Data Current Deferred Income Tax Liabilities, Net Deferred Income Tax Liabilities, Net Available for sale, Due after one year through five years (amortized cost) Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Entity Small Business Entity Small Business Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Parent Unearned premiums Unearned Premiums Gross investment income Gross investment income The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It does not include realized gains and losses on investments or investment expenses. ECM ECM [Member] ECM Subsequent Events [Abstract] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Net adjustment related to defined benefit pension plans, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Provisions for insured events of the current year Current Year Claims and Claims Adjustment Expense Document Type Document Type Insurance Commissions Insurance Commissions Payments to Acquire Businesses, Net of Cash Acquired Payments to Acquire Businesses, Net of Cash Acquired 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] Additional claim and related expenses Additional claim and related expenses Additional claim and related expense provisions Share Repurchase Program, Remaining Authorized, Amount Share Repurchase Program, Remaining Authorized, Amount Total premiums and fees Total premiums and fees Total Premiums And Fees Total earned premiums, title, escrow, and other real estate related fees earned during the period on the income statement. Subsequent Event [Line Items] Subsequent Event [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Short-term investments (at fair value which approximates cost) Short-term investments Other Short-Term Investments Available for sale, Unrealized Losses, Less than 12 Months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Senior Notes Due 2026 [Member] Senior Notes Due 2026 [Member] Senior Notes Due 2026 [Member] Reinsurance Recoverable, Allowance for Credit Loss Reinsurance Recoverable, Allowance for Credit Loss Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Total revenues Consolidated revenues Revenues Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Gain (Loss) on Securities [Line Items] Gain (Loss) on Securities [Line Items] Other – net Increase (Decrease) in Accounts Payable and Accrued Liabilities Unrealized gains (losses) on securities: OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment and Tax [Abstract] Total operating revenues Total Operating Revenues Total Operating Revenues Aggregate revenue from operations recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). Reinsurance balances and funds held Funds Held under Reinsurance Agreements, Asset Debt [Abstract] Debt [Abstract] Debt [Abstract] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Supplemental cash flow information: Supplemental Cash Flow Information [Abstract] Treasury Stock, Shares, Acquired Treasury Stock, Shares, Acquired Commissions, expenses, fees, and taxes Accounts Payable and Accrued Liabilities Total payments Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Other assets Other Assets Entity Tax Identification Number Entity Tax Identification Number Legal Entity [Axis] Legal Entity [Axis] Treasury Stock, Value, Acquired, Cost Method Treasury Stock, Value, Acquired, Cost Method Postemployment Benefit Plans, Policy Postemployment Benefit Plans, Policy [Policy Text Block] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Subsequent Event [Table] Subsequent Event [Table] U.S. & Canadian Governments [Member] Fixed Maturity Securities, U S Canadian Governments [Member] This category includes investments in debt securities issued by the United States Department of the Treasury, US Government Agencies and US Government-sponsored Enterprises, as well as debt securities issued by the Canadian government. Available for sale, Due after five years through ten years (amortized cost) Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Net income (loss) per share: Basic (in dollars per share) Earnings Per Share, Basic Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Payments for Repurchase of Common Stock Payments for Repurchase of Common Stock Statistical Measurement [Axis] Statistical Measurement [Axis] Segment underwriting income (loss) Segment underwriting income (loss) Segment underwriting income (loss) Other-than-temporary Impairment Loss, Debt Securities, Recognized in Earnings Other-than-temporary Impairment Loss, Debt Securities, Available-for-Sale, Recognized in Earnings Retained earnings Retained Earnings (Accumulated Deficit) Reinsurance Premiums for Insurance Companies, by Product Segment [Axis] Product and Service [Axis] Equity Securities, FV-NI Equity Securities, FV-NI Common Stock Common Stock [Member] Fixed income securities (at fair value) (amortized cost: $12,116.5 and $12,478.8) Fixed income securities (estimated fair value) Available for sale, Fixed income securities Available for sale, Fixed income securities (estimated fair value) Debt Securities, Available-for-Sale Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings Interest and other charges Interest And Other Charges The sum of interest expense incurred on borrowed funds and all other expenses otherwise not accounted for separately in the income statement during the period. Cover [Abstract] Cover [Abstract] Equity securities, gross unrealized gains Equity securities, gross unrealized gains This item represents the gross unrealized gains for equity securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities. Insurance [Abstract] Insurance [Abstract] Unallocated ESSOP Shares Unallocated ESSOP Shares [Member] Unallocated ESSOP Shares [Member] Other policyholders' benefits and funds held Other Policholders Benefits And Funds The total liability as of the balance sheet date of amounts due policy holders, excluding future claims, for unpaid policy dividends, retrospective refunds, undistributed earnings on participating business, and future policy benefits on life and health insurance policies. Reinsurance balances and funds held Increase (Decrease) in Funds Held under Reinsurance Agreements Debt Securities, Available-for-sale, Realized Gain (Loss) Debt Securities, Available-for-Sale, Realized Gain (Loss) Total liabilities and equity Liabilities and Equity Realized from actual transactions and impairments Realized from actual transactions and impairments Realized Investment Gains (Losses) Schedule of Fixed Income Securities [Table] [Line Items] Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items] [Line Items] for Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Table] Equity, Attributable to Noncontrolling Interest Equity, Attributable to Noncontrolling Interest Segments [Axis] Segments [Axis] Proceeds from Issuance of Senior Long-term Debt Proceeds from Issuance of Senior Long-Term Debt Accounts and notes receivable Increase (Decrease) in Premiums Receivable Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Short-term Investments [Member] Short-Term Investments [Member] Effect of dilutive securities - convertible notes Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities General expenses, taxes and fees General and Administrative Expense Information About Segments of Business [Abstract] Information About Segments of Business [Abstract] Information About Segments of Business [Abstract] Preferred Stock, authorized shares (in shares) Preferred Stock, Shares Authorized Schedule of Changes in Aggregate Reserves for Losses, Claims and Settlement Expenses Schedule of Changes in Aggregate Reserves for the Company's Losses, Claims and Settlement Expenses [Table Text Block] Tabular disclosure of the analysis of changes in aggregate reserves for losses, claims, and settlement expenses. Additionally, tabular disclosure for net increases/decreases in reserves by segment and year-end net iBNR reserves carried in each segment. [Table Text Block] Share Repurchase Program [Axis] Share Repurchase Program [Axis] SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Prior Year Claim and Claim Adjustment Expense SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Prior Year Claim and Claim Adjustment Expense Class of Stock [Domain] Class of Stock [Domain] Cash paid (received) during the period for: Interest Interest Paid, Excluding Capitalized Interest, Operating Activity Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Extinguishment of Debt, Amount Extinguishment of Debt, Amount Net realized gains (losses) Net realized gains (losses) Net realized gains (losses) The net realized gains or losses on investments during the period, net of income taxes, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. Gain (Loss) on Investments by Category [Axis] Debt Security Category [Axis] Investment, Policy Investment, Policy [Policy Text Block] Commissions, Insurance taxes, licenses, and fees Commissions, Insurance taxes, licenses, and fees Commissions, Insurance taxes, licenses, and fees Liability for Unpaid Claims and Claims Adjustment Expense Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Income Taxes Income Tax Disclosure [Text Block] All Other Segments [Member] Other Operating Segment [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Debt Instrument [Line Items] Debt Instrument [Line Items] Proceeds from Sale of Equity Securities, FV-NI Proceeds from Sale of Equity Securities, FV-NI Business Combination, Consideration Transferred Business Combination, Consideration Transferred Corporate Segment and Other Operating Segment Corporate Segment and Other Operating Segment [Member] Loss and loss adjustment expense reserves Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Debt Securities, Available-for-sale, Unrealized Loss Position Debt Securities, Available-for-Sale, Unrealized Loss Position Origination of Loans to Employee Stock Ownership Plans Origination of Loans to Employee Stock Ownership Plans Prior period estimated coverage rescissions and claims denials Increase (Decrease) in Loss and Loss Adjustment Expense Reserve, Prior Year Increase (Decrease) in Loss and Loss Adjustment Expense Reserve, Prior Year Assets Held-for-Sale Assets Held-for-Sale [Policy Text Block] Assets Held-for-Sale Net investment gains (losses): Realized Investment Gains (Losses) [Abstract] Loss Ratio Loss Ratio Treasury Stock, Retired, Cost Method, Amount Treasury Stock, Retired, Cost Method, Amount Equity Securities, FV-NI, Unrealized Gain (Loss) Equity Securities, FV-NI, Unrealized Gain (Loss) Federal income taxes Increase Decrease In Income Taxes Net The net change during the period in net income taxes payable or recoverable and net deferred tax assets and liabilities. Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Total of major segments Total of major segments [Member] Segment information pertaining to total revenues, income (loss) before taxes (credits), and income tax expense (credits), before the inclusion of amounts from other sources, reconciling items and eliminations. Entity Address, Address Line One Entity Address, Address Line One Combined Ratio Combined Ratio Total expenses Benefits, Losses and Expenses March 1, 2024 & August 19, 2025 Authorization March 1, 2024 & August 19, 2025 Authorization [Member] March 1, 2024 & August 19, 2025 Authorization Total income taxes Income tax expense (credits) Income Tax Expense (Benefit) Consolidation, Policy Consolidation, Policy [Policy Text Block] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Total net income Total net income Net Income (Loss) Attributable to Parent Investments [Member] Investments [Member] APIC, Share-based Payment Arrangement, Recognition and Exercise Stock based compensation Stock based compensation RFIG Run-off Business [Member] RFIG Run-off Business [Member] RFIG Run-off Business [Member] RFIG Run-off Business [Member] Purchases of: Cash Flows From Investing Activities Purchases Of Investing Activities [Abstract] Statement [Table] Statement [Table] Estimated reduction in paid losses from rescissions Insurance Rescission Insurance Rescission Stock based compensation awards [Member] Share-Based Payment Arrangement [Member] Revenues: Consolidated Revenues [Abstract] Revenues [Abstract] Key Employee Performance Recognition Plans one-time charge Key Employee Performance Recognition Plans one-time charge Key Employee Performance Recognition Plans one-time charge Unpaid Policy Claims and Claims Adjustment Expense, Policy Unpaid Policy Claims and Claims Adjustment Expense, Policy [Policy Text Block] Accounting Policies and Basis of Presentation Basis of Presentation and Significant Accounting Policies [Text Block]