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Authorized 200,000,000 shares; 23,403,960 issued and 20,796,637 outstanding at September 30, 2023 and 22,911,227 issued and 20,303,904 outstanding at September 30, 2022 Common stock, $0.01 par value. 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and counterparties Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits With And Receivables From Broker Dealers, Clearing Organizations, And Counterparties Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits With And Receivables From Broker Dealers, Clearing Organizations, And Counterparties Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Introducing Broker Commissions Commissions Expense, Policy [Policy Text Block] Termination Date Trading Arrangement Termination Date Number of commercial, institutional and global payment clients (more than) Number of Commercial, Institutional and Global Payments Clients Number of Commercial, Institutional and Global Payments Clients Common stock, authorized (in shares) Common Stock, Shares Authorized Derivative assets, net expected to be released from Other comprehensive income into earnings within the next 12 months: Derivative Assets, Hedge Gain (Loss) to be Reclassified within 12 Months Derivative Assets, Hedge Gain (Loss) to be Reclassified within 12 Months Retail customer liabilities Retail Customer Liabilities [Member] Retail Customer Liabilities Finite-lived customer base, gross amount Finite-Lived Customer Lists, Gross Indefinite-lived Intangible Assets [Axis] Indefinite-Lived Intangible Assets [Axis] Securities sold under agreements to repurchase, gross Securities sold under agreements to repurchase Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, before Offset Adjustments to reconcile net income to net cash (used in)/provided by operating activities: Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Award Timing Disclosures [Line Items] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Investment in subsidiaries for equity method accounting, earnings (loss) Adjustment to Investment in Subs Revenue for Equity Method Accounting Adjustment to Investment in Subs Revenue for Equity Method Accounting Additional paid-in-capital Additional paid-in capital Additional Paid in Capital Maximum borrowing capacity under credit facilities Maximum Borrowing Capacity Under Credit Facilities Maximum Borrowing Capacity Under Credit Facilities Pledged Status [Domain] Pledged Status [Domain] Income Taxes Income Tax, Policy [Policy Text Block] Fiscal 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Three Weighted average grant date fair value, exercised (in dollar per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercised in Period, Weighted Average Grant Date Fair Value The weighted average grant-date fair value of options exercised during the reporting period as calculated by applying the disclosed option pricing methodology. Gross amount of secured financing Collateralized Financings Insider Trading Arrangements [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Insurance General Insurance Expense Total fair value of liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tangible Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tangible Liabilities Clients Clients [Member] Clients Adjusted net capital Broker-Dealer, Minimum Net Capital Required, Broker-Dealer Subsidiary, Aggregate Indebtedness Standard Aggregate intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Security Owned and Sold, Not yet Purchased, at Fair Value [Table] Security Owned and Sold, Not yet Purchased, at Fair Value [Table] Entity Registrant Name Entity Registrant Name Award Timing Method Award Timing Method [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies Foreign earnings and losses taxed at different rates Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Fiscal 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Two Adjustment to Compensation, Amount Adjustment to Compensation Amount Contingent consideration, liability term Business Combination, Contingent Consideration, Liability Term Business Combination, Contingent Consideration, Liability Term Additional consideration payable related to acquisitions Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Foreign operating loss carryforwards, net of valuation allowances Deferred Tax Assets, Net of Valuation Allowance, Operating Loss Carryforwards, Foreign Deferred Tax Assets, Net of Valuation Allowance, Operating Loss Carryforwards, Foreign Auditor Name Auditor Name Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Trade conversion fees Trade Conversion Fees [Member] Trade Conversion Fees [Domain] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Less: accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Weighted average  exercise price, exercisable (in dollar per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Payable to broker-dealers, clearing organizations and counterparties Increase (Decrease) in Payable to Broker-Dealer and Clearing Organization Entity Central Index Key Entity Central Index Key Amortization and extinguishment of debt issuance costs Amortization and extinguishment of debt issuance costs Amortization of Debt Issuance Costs and Discounts Gain on acquisition Gain on acquisition Business Combination, Bargain Purchase, Gain Recognized, Amount Total derivatives designated as hedging instruments Derivative instruments, gain (loss) recognized in income, net Derivative, Gain (Loss) on Derivative, Net Allocated share-based compensation expense Share-Based Payment Arrangement, Expense Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Finite-lived intangible assets, gross amount Finite-Lived Intangible Assets, Gross Precious metals - held by non-broker-dealer subsidiaries Inventory, Finished Goods, Net of Reserves Non-deductible compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent Non cash equivalent segregated assets Non cash equivalent segregated assets Non cash equivalent segregated assets Revenue Benchmark Revenue Benchmark [Member] Name Trading Arrangement, Individual Name Other comprehensive income/(loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Number of global financial markets Number Of Global Financial Markets Number Of Global Financial Markets Securities and Other Assets Segregated Under Federal and Other Regulations [Axis] Securities and Other Assets Segregated Under Federal and Other Regulations [Axis] Securities and Other Assets Segregated Under Federal and Other Regulations Cash segregated and deposited with or pledged to exchange-clearing organizations and other futures commission merchants (“FCMs”) Cash Segregated And Deposited With Or Pledged To Exchange-clearing Organizations And Other Futures Commission Merchants Cash Segregated And Deposited With Or Pledged To Exchange-clearing Organizations And Other Futures Commission Merchants Entity [Domain] Entity [Domain] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Amendment Flag Amendment Flag Intangible Assets Intangible Assets Disclosure [Text Block] Legal Entity [Axis] Legal Entity [Axis] Securities purchased under agreements to resell Increase (Decrease) in Receivables under Repurchase Agreements Commodities leases Commodities Leases and Unpriced Positions [Member] Commodities Leases and Unpriced Positions [Member] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Intangible assets Deferred Tax Assets, Goodwill and Intangible Assets Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Business licenses Licensing agreements Licensing Agreements [Member] Carrying value Senior Secured Notes Senior Notes SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Cash paid for interest Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activities Customer and non-customer risk maintenance margin Customer And Non-customer Risk Maintenance Margin [Member] Customer And Non-customer Risk Maintenance Margin Commodities warehouse receipts Commodities Warehouse Receipts [Member] Commodities Warehouse Receipts [Member] Acquisitions and Contingent Consideration Business Combinations Policy [Policy Text Block] StoneX Financial Inc. StoneX Financial Inc. [Member] StoneX Financial Inc. Member Interest expense on corporate funding Interest Expense On Corporate Funding Interest Expense On Corporate Funding Goodwill Goodwill Disclosure [Text Block] Selling and Marketing Selling, General and Administrative Expenses, Policy [Policy Text Block] Diluted (in shares) Diluted shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Defined contribution plan, employers matching contribution, annual vesting percentage Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Polish Zloty Poland, Zlotych Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Axis] Finite-lived software programs/platforms, gross amount Capitalized Computer Software, Gross Indefinite-lived intangible assets acquired Indefinite-Lived Intangible Assets Acquired Purchase of property and equipment and internally developed software Payments to Acquire Property, Plant, and Equipment Company Selected Measure Amount Company Selected Measure Amount Weighted average remaining term (in years) Share-Based Payment Arrangement, Option, Exercise Price Range, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] Share-Based Payment Arrangement, Option, Exercise Price Range [Line Items] Defined benefit plan, expected future benefit payment, year four Defined Benefit Plan, Expected Future Benefit Payment, Year Four Weighted average  exercise price, expired (in dollar per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Total assets Assets Assets Name Awards Close in Time to MNPI Disclosures, Individual Name Equipment Equipment [Member] Total net assets acquired Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) Share-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Compensation and benefits Compensation and benefits Labor and Related Expense Financial instruments owned, at fair value Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets Weighted average grant date fair value, vested (in dollar 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 Notes payable to bank Notes Payable to Bank Non-NEOs Non-NEOs [Member] Gain on acquisitions and other gains, net Other Nonoperating Gains (Losses) Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] Amount outstanding Amount Outstanding on Committed Credit Facilities Amount Outstanding on Committed Credit Facilities Cash flows from financing activities: Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Non-PEO NEO Non-PEO NEO [Member] Accounts Payable and Other Accrued Liabilities (Including Contingent Liabilities) [Domain] Accounts Payable and Other Accrued Liabilities (Including Contingent Liabilities) [Domain] Accounts Payable and Other Accrued Liabilities (Including Contingent Liabilities) [Domain] Adjustment to Compensation: Adjustment to Compensation [Axis] Purchase of shareholders equity interest Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Total fair value included in Payables to clients Payables To Clients [Member] Payables To Clients Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Weighted average grant date fair value, forfeited (in dollar per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeited in Period, Weighted Average Grant Date Fair Value The weighted average grant-date fair value of options forfeited during the reporting period as calculated by applying the disclosed option pricing methodology. Debt Instrument [Line Items] Debt Instrument [Line Items] Basic (in shares) Common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Financial instruments owned, securities pledged as collateral that can be sold or repledged Securities Sold under Agreements to Repurchase, Fair Value of Collateral StoneX Financial Pte. Ltd. StoneX Financial Pte. Ltd. [Member] StoneX Financial Pte. Ltd. Member Property and equipment Deferred Tax Liabilities, Property, Plant and Equipment Common Stock Split Common Stock Split [Member] Common Stock Split Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Client account fees Client Account Fees [Member] Client Account Fees [Member] Revenues: Revenues [Abstract] Long Long [Member] Changes in operating assets and liabilities, net: Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract] Deferred payments on acquisitions Deferred payments on acquisitions Payment for Deferred Contingent Consideration Liability, Financing Activities Payment for Deferred Contingent Consideration Liability, Financing Activities Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Statement [Line Items] Statement [Line Items] Deferred taxes: Deferred Federal, State and Local, Tax Expense (Benefit) [Abstract] Bad debt expense not included in allowance SEC Schedule, 12-09, Valuation Allowances and Reserves, Credit Loss Expense (Reversal) Not Included in Allowance SEC Schedule, 12-09, Valuation Allowances and Reserves, Credit Loss Expense (Reversal) Not Included in Allowance Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Schedule of Debt Schedule of Debt [Table Text Block] Commission and clearing fees Total commission and clearing fees Commission and Clearing Fees [Member] Commission and Clearing Fees [Member] Accounting Standards Update 2016-13 [Member]