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Taxes, Depreciation And Amortization Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Schedule of Fixed-Maturity and Short-Term Investments by Contractual Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of Unpaid Losses and Loss Adjustment Expenses (LAE) Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Dividends paid to non-controlling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Schedule of the Activity Related to Share Option Awards Share-Based Payment Arrangement, Option, Activity [Table Text Block] Weighted-Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Repurchase Program March 2026 Repurchase Program [Member] March 2026 Repurchase Program Common stock, 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Share-Based Payment Award, Options, Exercisable, Intrinsic Value Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Stock repurchase program, remaining authorized repurchase amount Share Repurchase Program, Remaining Authorized, Amount Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents [Member] Class B convertible preference shares Preferred Class B [Member] Arrangement Duration Trading Arrangement Duration Subsequent Event [Line Items] Subsequent Event [Line Items] Statement of Stockholders' Equity [Abstract] Proceeds from issuance of surplus notes Proceeds from Issuance of Long-Term Debt Local Phone Number Local Phone Number Interest expense on funds held under reinsurance Investment Expense, Interest On Funds Held Under Reinsurance Investment Expense, Interest On Funds Held Under Reinsurance Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name 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Commitments and contingencies (Note 17) Commitments and Contingencies Total revenues Revenues Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Net realized gains on equity method investments Equity Method Investment, Realized Gain (Loss) on Disposal Earnings from equity method investments Income from equity method investments Income (Loss) from Equity Method Investments Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Credit Rating, AM Best [Domain] Credit Rating, AM Best [Domain] Executive Category: Executive Category [Axis] Schedule of Nonvested Restricted Share Units Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Other Other [Member] Other Liabilities and shareholders' equity Liabilities and Equity [Abstract] Other Commitments [Table] Other Commitments [Table] Reinsurance Reinsurance [Text Block] Options exercisable, Weighted-Average Remaining Contractual Term Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted-Average Remaining Contractual Term Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] Beginning balance Ending balance Temporary Equity, Carrying Amount, Attributable to Parent Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis by Level Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] All Award Types Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Fair value measurements Fair Value Disclosures [Text Block] Significant unobservable inputs Level 3 Fair Value, Inputs, Level 3 [Member] Asset Pledged as Collateral Asset Pledged as Collateral [Member] Non-cash loss portfolio transfer transaction Non Cash, Operating Activity, Loss Portfolio Transfer Transaction Non Cash, Operating Activity, Loss Portfolio Transfer Transaction Supplemental cash flows information Supplemental Cash Flow Information [Abstract] Options unvested, Weighted-Average Exercise Price (in usd per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Option, Nonvested, Weighted Average Exercise Price Accounts payable and other liabilities Total Accounts Payable and Accrued Liabilities PEO Name PEO Name Total paid losses and LAE Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Geographical [Axis] Geographical [Axis] Profit sharing expense Profit Sharing Expense Profit Sharing Expense Incremental facilities available to draw upon request Line Of Credit Facility, Maximum Borrowing Capacity, Accordion Feature Line Of Credit Facility, Maximum Borrowing Capacity, Accordion Feature Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Legal Entity [Axis] Legal Entity [Axis] Schedule of Reinsurance Recoverable Schedule Of Reinsurance Recoverable [Table Text Block] Schedule Of Reinsurance Recoverable Interest expenses Interest expenses Interest Expense, Debt Other assets Total Prepaid Expense and Other Assets Written premiums: Premiums Written, Gross [Abstract] Other Commitments [Line Items] Other Commitments [Line Items] Cash, cash equivalents and restricted cash Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Direct Policyholder Benefits and Claims Incurred, Direct Options unvested, Aggregate Intrinsic Value Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Unvested, Intrinsic Value Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Unvested, Intrinsic Value Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Senior unsecured debt due 2029 Senior Unsecured Notes [Member] Senior Unsecured Notes Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] 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] Nature of business and basis of presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Total comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Subsequent Event [Table] Subsequent Event [Table] Ownership % Equity Method Investment, Ownership Percentage Share-based compensation expenses Share-Based Payment Arrangement, Noncash Expense Employee compensation and benefits Labor and Related Expense Shares converted from Class B to Class A (in shares) Stock Issued During Period, Shares, Conversion of Convertible Securities Schedule of Debt Outstanding Schedule of Debt [Table Text Block] Employee share purchase plan Employee Stock [Member] Transactions with related party (benefit) expense Related Party Transaction, Amounts of Transaction UK and EU United Kingdom And European Union [Member] United Kingdom And European Union Investment, Name [Domain] Investment, Name [Domain] Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] Due after five years through ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Basic (in usd per share) Earnings Per Share, Basic Acquisition of common shares Payments for Repurchase of Common Stock Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Award Type [Axis] Award Type Award Type [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accumulated deficit Retained Earnings (Accumulated Deficit) Amortization of deferred acquisition costs Amortization of deferred acquisition costs Amortization of deferred acquisition costs Deferred Policy Acquisition Costs, Amortization Expense Ceding commission income, net increase (decrease) Deferred Income, Adjustment Due To Sliding Scale Deferred Income, Adjustment Due To Sliding Scale Options unvested as of June 30, 2026 (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested, Number of Shares Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock Common Stock [Member] Available for sale investments, at fair value Fair value Total fixed maturity and short-term investments Debt Securities, Available-for-Sale Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Insurance [Abstract] Concentration risk, percentage Concentration Risk, Percentage Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Income recorded Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount Schedule of Equity Securities without Readily Determinable Fair Value Equity Securities without Readily Determinable Fair Value [Table Text Block] Equity Awards Adjustments Equity Awards Adjustments [Member] Funds held under reinsurance Increase (Decrease) in Funds Held under Reinsurance Agreements Assumed Assumed Premiums Earned Net realized (losses) gains on fixed maturity and short-term investments Debt Securities, Available-for-Sale, Realized Gain (Loss) Total liabilities and equity Liabilities and Equity Accelerated share-based payment expense Share-Based Payment Arrangement, Accelerated Cost Net realized gains on investments Net realized gains on investments Net realized gains on investments Net realized gains (losses) on investments Net realized gains on investments Realized Investment Gains (Losses) Share options Share-Based Payment Arrangement, Option [Member] Ceded Credit Risk [Table] Ceded Credit Risk [Table] Non-controlling interests Equity, Attributable to Noncontrolling Interest Profits Interest Award Profits Interest Award [Member] Profits Interest Award Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Related Party [Domain] Related and Nonrelated Parties [Domain] Premiums receivable Increase (Decrease) in Premiums Receivable Tabular List, Table Tabular List [Table Text Block] Additional paid-in capital Additional Paid in Capital Reinsurance recoverables on unpaid losses and LAE Less: Reinsurance recoverables, beginning of year Reinsurance recoverables on unpaid losses and LAE, end of period Reinsurance recoverables on unpaid losses and LAE Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Schedule of Unrealized Gain (Loss) on Investments Unrealized Gain (Loss) on Investments [Table Text Block] Reinsurance recoverables on unpaid losses and loss adjustment expenses Increase (Decrease) in Reinsurance Recoverable Total Accelerant shareholders' equity Parent [Member] Short-term investments Short-Term Investments [Member] Schedule of Accounts Payable and Other Liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Current income tax recoverable Income Taxes Receivable, Current Ceding commission income Ceded Commission Income Ceded Commission Income Name Awards Close in Time to MNPI Disclosures, Individual Name Shareholders' equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Entity Address, Country Entity Address, Country Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Outstanding, Aggregate Intrinsic Value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Ceded Ceded Premiums Written Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period General and administrative expenses Total general and administrative expenses General and Administrative Expense Preference shares authorized (in shares) Preferred Stock, Shares Authorized Adjustment to Compensation: Adjustment to Compensation [Axis] Commercial mortgage-backed Commercial Mortgage-Backed Securities [Member] Share Repurchase Program [Axis] Share Repurchase Program [Axis] MGA Operations MGA Operations Segment [Member] MGA Operations Segment Class of Stock [Domain] Class of Stock [Domain] Schedule of Restricted Assets that have been Pledged as Collateral Schedule Of Restricted Assets That Have Been Pledged As Collateral [Table Text Block] Schedule Of Restricted Assets That Have Been Pledged As Collateral Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Interest on debt paid Interest Paid, Excluding Capitalized Interest, Operating Activity Statement of Cash Flows [Abstract] Unfunded commitments Other Commitment Commission income receivable Commission Income Receivable Commission Income Receivable Credit Facility [Axis] Credit Facility [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Maximum exposure to loss Equity Method Investment, Maximum Exposure To Loss Equity Method Investment, Maximum Exposure To Loss Name Measure Name Commission refund liabilities Commission Refund Liabilities Commission Refund Liabilities Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] MGAs and TPAs MGAs And TPAs [Member] MGAs And TPAs Income taxes Income Tax Disclosure [Text Block] Schedule of Deposits for Regulatory and Other Purposes Schedule Of Deposit Assets For Regulatory And Other Purposes [Table Text Block] Schedule Of Deposit Assets For Regulatory And Other Purposes Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Other, net Other Noncash Income (Expense) Debt Instrument [Line Items] Debt Instrument [Line Items] Proceeds from sale of TPA investment Proceeds from Sale of Equity Securities, FV-NI Net realized gains on other investments Gain (Loss) on Sale of Other Investments Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Unpaid losses and loss adjustment expenses 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 Total Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Capitalized technology development expenditures Payments to Develop Software Name Trading Arrangement, Individual Name Share-based compensation, cost not yet recognized Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Cash and cash equivalents Cash and Cash Equivalent Payments for purchases of: Payments to Acquire Investments [Abstract] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Company Selected Measure Amount Company Selected Measure Amount Dividends from equity method investees Proceeds from Equity Method Investment, Distribution Net unrealized (losses) gains on equity securities held at the reporting date Equity Securities, FV-NI, Unrealized Gain (Loss) General and administration expenses General And Administration Expense, Excluding Share-Based Compensation General And Administration Expense, Excluding Share-Based Compensation Income Tax Paying Status [Axis] Income Tax Paying Status [Axis] Income Tax Paying Status Investments, Debt and Equity Securities [Abstract] Earned premiums: Premiums Earned, Net [Abstract] Entity Address, Address Line Three Entity Address, Address Line Three Entity Address, Address Line Two Entity Address, Address Line Two Stock, Class of Stock [Table] Stock, Class of Stock [Table] Net income Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Business Combination, Price Per Share Business Combination, Price Per Share Gross investment income Gross Investment Income, Operating Non-PEO NEO Non-PEO NEO [Member] Entity Address, Address Line One Entity Address, Address Line One Total expenses Benefits, Losses and Expenses Vested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value North America North America [Member] Income tax expense Income tax expense Income Tax Expense (Benefit) Amount received Reinsurance Recoverable, Amount Received Reinsurance Recoverable, Amount Received Net foreign exchange (gains) losses Net foreign exchange (gains) losses Net foreign exchange gain (loss) Gain (Loss), Foreign Currency Transaction, before Tax Non-cash revenues, expenses, gains and losses included in net (loss) income: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Noncash Item [Abstract] Total Restricted Cash and Investments Award Timing Method Award Timing Method [Text Block] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Premiums receivable (net of allowance 2026: $5.1 and 2025: $4.6) Premiums Receivable, Net Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Statement [Table] Statement [Table] Restatement Determination Date: Restatement Determination Date [Axis] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Investment income, interest Investment Income, Interest Options exercisable, Weighted-Average Exercise Price (in usd per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Schedule of Other Assets Schedule of Other Assets [Table Text Block] Corporation tax payable Accrued Income Taxes Tax-paying entities Tax-Paying Entities [Member] Tax-Paying Entities Decrease related to recoveries Increase (Decrease) In Reinsurance Recoverable, Deposit Assets, Recoveries Increase (Decrease) In Reinsurance Recoverable, Deposit Assets, Recoveries Revenues Revenues [Abstract] Equity Temporary Equity [Abstract] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Income Tax Paying Status [Domain] Income Tax Paying Status [Domain] Income Tax Paying Status [Domain] Numerator: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract]