Intangible Assets [Abstract] Intangible Assets [Abstract] Intangible Assets Disclosure [Text Block] Intangible Assets Disclosure [Text Block] Earnings Per Share [Abstract] Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Physical Commodities Inventory [Abstract] Physical Commodities Inventory [Abstract] Inventory Disclosure [Text Block] Inventory Disclosure [Text Block] Commitments and Contingencies [Abstract] Commitments and Contingencies [Abstract] Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Disclosure [Text Block] Receivables [Abstract] Statement [Table] Statement [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Commercial Hedging [Member] Commercial Hedging [Member] Commercial Hedging [Member] Securities [Member] Securities Segment [Member] Securities Segment [Member] Commercial Hedging [Member] Commodity and Risk Management [Member] Commodity and Risk Management [Member] Physical Commodities [Member] Other Segment [Member] Other Segment [Member] Statement [Line Items] Statement [Line Items] Allowance for Doubtful Accounts Receivable, Period Increase (Decrease) Allowance for Doubtful Accounts Receivable, Period Increase (Decrease) Provision for Doubtful Accounts Provision for Doubtful Accounts Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-Lived Intangible Assets [Table] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Trade Names [Member] Indefinite-lived Intangible Assets [Line Items] Indefinite-lived Intangible Assets [Line Items] Amortization of Intangible Assets Amortization of Intangible Assets Gross Finite and Indefinite-Lived Intangible Assets Gross Finite and Indefinite-Lived Intangible Assets Gross amount of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. In addition, it includes the carrying amount of assets (excluding financial assets) that lack physical substance, excluding goodwill, having a projected indefinite period of benefit. Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. In addition, it includes impairment recognized during the life of the intangible that results from the write-down of indefinite-lived intangible assets after comparing the implied fair value of reporting unit indefinite-lived intangible assets with the carrying amount of that indefinite-lived intangible assets, which are assessed at least annually for impairment. Intangible Assets, Net (Excluding Goodwill) Intangible Assets, Net (Excluding Goodwill) Assets and Liabilities, at Fair Value [Abstract] Assets and Liabilities, at Fair Value [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Asset Class [Axis] Asset Class [Axis] Fair Value by Asset Class [Domain] Asset Class [Domain] Common stock and American Depositary Receipts (ADRs) [Member] Common stock and American Depositary Receipts (ADRs) [Member] Common stock and American Depositary Receipts (ADRs) [Member] Corporate Debt Securities [Member] Corporate Debt Securities [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Contingent Consideration [Member] Contingent Consideration [Member] Contingent consideration includes remeasurement of contingent liabilities related to business combinations accounted for in accordance with the provisions of the Business Combinations Topic of the ASC. Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Rollforward of Level 3 Securities [Roll Forward] Rollforward of Level 3 Securities [Roll Forward] Rollforward of Level 3 Securities [Roll Forward] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Rollforward of Level 3 Liabilities [Roll Forward] Rollforward of Level 3 Liabilities [Roll Forward] Rollforward of Level 3 Liabilities [Roll Forward] Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Earnings Per Share, Potentially Dilutive Securities Earnings Per Share, Policy [Policy Text Block] Accumulated Other Comprehensive Income (Loss) [Abstract] Accumulated Other Comprehensive Income (Loss) [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Derivative Netting Adjustment [Axis] Derivative Netting Adjustment [Axis] Derivative Netting Axis. Derivative Netting [Domain] Derivative Netting [Domain] Derivative Netting [Domain] Counterparty And Cash Collateral Netting Adjustment [Member] Counterparty And Cash Collateral Netting Adjustment [Member] Counterparty And Cash Collateral Netting Adjustment [Member] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Certificates of Deposit [Member] Certificates of Deposit [Member] 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 [Axis] Securities and other assets segregated under federal and other regulations [Domain] Securities and other assets segregated under federal and other regulations [Domain] Securities and other assets segregated under federal and other regulations [Domain] Commodities warehouse receipts [Member] Commodities warehouse receipts [Member] Commodities warehouse receipts [Member] US Government Debt Securities [Member] US Government Debt Securities [Member] Deposits and receivables from exchange clearing organizations [Axis] Deposits and receivables from exchange clearing organizations [Axis] Deposits and receivables from exchange clearing organizations [Axis] Deposits and receivables from exchange clearing organizations [Domain] Deposits and receivables from exchange clearing organizations [Domain] Deposits and receivables from exchange clearing organizations [Domain] Money Market Funds [Member] Money Market Funds [Member] Derivative [Member] Derivative [Member] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Axis] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Axis] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Axis] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] TBA and forward settling securities [Member] TBA and forward settling securities [Member] TBA and forward settling securities [Member] Security Owned and Sold, Not yet Purchased, at Fair Value [Axis] Security Owned and Sold, Not yet Purchased, at Fair Value [Axis] Security Owned and Sold, Not yet Purchased Fair Value, Security Name [Domain] Security Owned and Sold, Not yet Purchased Fair Value, Security Name [Domain] Exchangeable foreign ordinary equities and ADRs [Member] Exchangeable foreign ordinary equities and ADRs [Member] Exchangeable foreign ordinary equities and ADRs [Member] Foreign Government Debt Securities [Member] Foreign Government Debt Securities [Member] Collateralized Mortgage Backed Securities [Member] Collateralized Mortgage Backed Securities [Member] Commodities leases [Member] Commodities leases and unpriced positions [Member] Commodities leases and unpriced positions [Member] Exchange firm common stock [Member] Exchange firm common stock [Member] Exchange firm common stock [Member] Mutual funds and other [Member] Mutual funds and other [Member] Mutual funds and other [Member] Physical commodities inventory [Axis] Physical commodities inventory [Axis] Physical commodities inventory [Axis] Physical commodities inventory [Domain] Physical commodities inventory [Domain] [Domain] for Physical commodities inventory [Axis] Physical commodities inventory - precious metals [Member] Physical commodities inventory - precious metals [Member] Physical commodities inventory - precious metals Accounts payable and other accrued liabilities (including contingent liabilities) [Axis] Accounts payable and other accrued liabilities (including contingent liabilities) [Axis] Accounts payable and other accrued liabilities (including contingent liabilities) [Axis] Accounts Payable and Other Accrued Liabilities [Domain] Accounts Payable and Other Accrued Liabilities [Domain] Accounts Payable and Other Accrued Liabilities [Domain] Payables to broker-dealers, clearing organizations and counterparties [Axis] Payables to broker-dealers, clearing organizations and counterparties [Axis] Payables to broker-dealers, clearing organizations and counterparties [Axis] Payables to broker-dealers, clearing organizations and counterparties [Domain] Payables to broker-dealers, clearing organizations and counterparties [Domain] [Domain] for Payables to broker-dealers, clearing organizations and counterparties [Axis] 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] Cash and Cash Equivalents, Fair Value Disclosure Cash and Cash Equivalents, Fair Value Disclosure Cash and Securities Segregated under Federal and Other Regulations Cash and Securities Segregated under Federal and Other Regulations Receivables from Clearing Organizations Receivables from Clearing Organizations Receivables from Brokers-Dealers and Clearing Organizations Receivables from Brokers-Dealers and Clearing Organizations Financial Instruments, Owned, at Fair Value Financial Instruments, Owned, at Fair Value Physical commodities inventory Inventory, Gross Assets, Fair Value Disclosure Assets, Fair Value Disclosure Accounts Payable and Other Accrued Liabilities Accounts Payable and Other Accrued Liabilities Payables to Broker-Dealers and Clearing Organizations Payables to Broker-Dealers and Clearing Organizations Financial Instruments Sold, Not yet Purchased, at Fair Value Financial Instruments Sold, Not yet Purchased, at Fair Value Liabilities, Fair Value Disclosure Financial and Nonfinancial Liabilities, Fair Value Disclosure Receivables from customers and notes receivable, net [Abstract] Receivables from customers and notes receivable, net [Abstract] Allowance Notes Receivable Allowance Notes Receivable A valuation allowance relating to a written agreement to receive money (at a specified future date(s), consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible. Credit Facilities [Abstract] Credit Facilities [Abstract] Schedule of Debt [Table Text Block] Schedule of Debt [Table Text Block] Commodity and Other Repurchase Agreements [Abstract] Commodity and Other Repurchase Agreements [Abstract] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] G.X. Clarke (INTL FCStone Partners) [Member] G.X. Clarke (INTL FCStone Partners) [Member] Acquisition of G.X. Clarke, which was subsequently named INTL FCStone Partners. Sterne Agee [Member] Sterne Agee [Member] Sterne Agee [Member] Fair Value of Securities Received as Collateral that Can be Resold or Repledged Fair Value of Securities Received as Collateral that Can be Resold or Repledged Fair Value of Securities Received as Collateral that Have Been Resold or Repledged Fair Value of Securities Received as Collateral that Have Been Resold or Repledged Financing Receivables, net - Sales/Repurchase Agreements Sales Repurchase Agreements Financing Receivables, net - Sales/Repurchase Agreements Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty Securities Sold under Agreements to Repurchase, Fair Value of Collateral Securities Sold under Agreements to Repurchase, Fair Value of Collateral Trading Securities Pledged as Collateral Financial Instruments Owned and Pledged as Collateral, Amount Not Eligible to be Repledged by Counterparty Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements Basis of Presentation and Consolidation [Abstract] Basis of Presentation and Consolidation [Abstract] Basis of Accounting, Policy [Policy Text Block] Basis of Accounting, Policy [Policy Text Block] Consolidation, Policy [Policy Text Block] Consolidation, Policy [Policy Text Block] Fiscal Period, Policy [Policy Text Block] Fiscal Period, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Securities Borrowed and Loaned Policy [Policy Text Block] Securities Borrowed and Loaned Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract] Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract] Derivative Instruments, Gain (Loss), by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract Type [Domain] Derivative Contract [Domain] Commodity Contract [Member] Commodity Contract [Member] Foreign Exchange Forward [Member] Foreign Exchange Forward [Member] Interest Rate Contract [Member] Interest Rate Contract [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) Recognized in Income, Net Derivative, Gain (Loss) on Derivative, Net Goodwill [Abstract] Goodwill [Abstract] Goodwill Disclosure [Text Block] Goodwill Disclosure [Text Block] Business Combinations [Abstract] Business Combination Disclosure [Text Block] Business Combination Disclosure [Text Block] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] ICAP [Member] [Member] ICAP [Member] [Member] ICAP [Member] Business Combination, Consideration Transferred Business Combination, Consideration Transferred Finite-Lived Intangible Asset, Useful Life Finite-Lived Intangible Asset, Useful Life Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract] Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Pension liabilities adjustment Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Reclassification of adjustments included in net income [Abstract] Reclassification of adjustment for gains included in net income [Abstract] Reclassification of adjustment for gains included in net income [Abstract] Periodic pension costs (included in compensation and benefits) Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax Reclassification adjustment for gains included in net income Reclassification adjustments for gains (losses) included in net income Reclassification adjustments for gains (losses) included in net income Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Other Expenses [Abstract] Other Expenses [Text Block] Other Income and Other Expense Disclosure [Text Block] Schedule of Finite and Indefinite-Lived Intangible Assets [Table Text Block] Schedule of Finite and Indefinite-Lived Intangible Assets [Table Text Block] Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance with a finite life or exist in perpetuity, by either major class or business segment. Schedule of Expected Amortization Expense [Table Text Block] Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Allowance for Doubtful Accounts Receivable Allowance for Doubtful Accounts Receivable Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Tabular disclosure of the fair value measurement of assets and liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset. Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Exchange-traded Commodity Contracts [Member] Exchange-traded Commodity Contracts [Member] Exchange-traded Commodity Contracts [Member] Over the Counter (OTC) Commodity Contracts [Member] Over the Counter (OTC) Commodity Contracts [Member] Over the Counter (OTC) Commodity Contracts [Member] Over the Counter (OTC) Foreign Exchange Contracts [Member] Over the Counter (OTC) Foreign Exchange Contracts [Member] Over the Counter (OTC) Foreign Exchange Contracts [Member] Exchange-traded interest rate contracts [Member] Exchange-traded interest rate contracts [Member] Exchange-traded interest rate contracts [Member] Equity Contract [Member] Equity Contract [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Deposits and Receivables from Exchange Clearing Organizations [Member] Deposits and Receivables from Exchange Clearing Organizations [Member] Deposits and Receivables from Exchange Clearing Organizations [Member] Deposits and receivables from broker-dealers, clearing organizations and counterparties [Member] Deposits and Receivables from Broker-dealers, clearing organizations and counterparties [Member] Deposits and Receivables from Broker-dealers, clearing organizations and counterparties [Member] Financial instruments owned [Member] Financial instruments owned [Member] Financial instruments owned [Member] Payable to broker-dealers, clearing organizations and counterparties [Member] Payable to broker-dealers, clearing organizations and counterparties [Member] Payable to broker-dealers, clearing organizations and counterparties [Member] Financial instrument sold, not yet purchased [Member] Financial instrument sold, not yet purchased [Member] Financial instrument sold, not yet purchased [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Asset, Fair Value, Gross Asset Derivative Asset, Fair Value, Gross Asset Derivative Liability, Fair Value, Gross Liability Derivative Liability, Fair Value, Gross Liability Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative, Fair Value, Net Derivative, Fair Value, Net Earnings Per Share [Text Block] Earnings Per Share [Text Block] Condensed Consolidated Balance Sheets [Abstract] Condensed Consolidated Balance Sheets [Abstract] ASSETS Assets [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash, securities and other assets segregated under federal and other regulations (including $247.6 and $618.8 at fair value at March 31, 2017 and September 30, 2016, respectively) Securities purchased under agreements to resell Securities Purchased under Agreements to Resell Securities Borrowed Securities Borrowed Deposits with and receivables from: Receivables from Brokers-Dealers and Clearing Organizations [Abstract] Exchange-clearing organizations (including $636.5 and $868.5 at fair value at March 31, 2017 and September 30, 2016, respectively) Broker-dealers, clearing organizations and counterparties (including $34.7 and $(15.2) at fair value at March 31, 2017 and September 30, 2016, respectively) Receivables from customers, net Accounts Receivable, Net Notes receivable, net Financing Receivable, Net Income taxes receivable Income Taxes Receivable Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $324.6 and $47.2 at March 31, 2017 and September 30, 2016, respectively) Physical commodities inventory, net (including $117.8 and $71.2 at fair value at March 31, 2017 and September 30, 2016, respectively) Deferred income taxes, net Deferred Tax Assets, Net Property and equipment, net Property, Plant and Equipment, Net Goodwill and intangible assets, net Goodwill and intangible assets, net Amount combines the carrying amounts for goodwill and finite- and indefinite-lived intangible assets. Goodwill represents the carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquire, adjusted for any amortization recognized prior to adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions. Indefinite-lived intangible assets represent the carrying amount of intangible assets, excluding goodwill, which have a projected indefinite period of benefit (hence are not amortized), allocated to the reportable segment. These assets, acquired either individually or as part of a group of assets, in either an asset acquisition or business combination, are assessed at least annually for impairment. Examples may include trade secrets, contractual rights, trade names, and licensing agreements. Finite-lived intangible assets are the aggregate sum of gross carrying value of a major finite-lived intangible asset class, less accumulated amortization and any impairment charges. A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company. Other assets Prepaid Expense and Other Assets Total assets Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Liabilities: Liabilities [Abstract] Accounts payable and other accrued liabilities (including $0.9 and $0.8 at fair value at March 31, 2017 and September 30, 2016, respectively) Payables to: Payables and Accruals [Abstract] Customers Payables to Customers Broker-dealers, clearing organizations and counterparties (including $9.8 and $3.5 at fair value at March 31, 2017 and September 30, 2016), respectively Lenders under loans Long-term Line of Credit Senior unsecured notes Senior Notes Income taxes payable Accrued Income Taxes Payables under repurchase agreements Securities Sold under Agreements to Repurchase Securities Loaned Securities Loaned Financial instruments sold, not yet purchased, at fair value Total liabilities Liabilities Commitments and contingencies (Note 11) Commitments and Contingencies Stockholders' Equity: Equity [Abstract] Preferred stock, $0.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding Preferred Stock, Value, Outstanding Common stock, $0.01 par value. Authorized 30,000,000 shares; 20,781,686 issued and 18,659,729 outstanding at March 31, 2017 and 20,557,175 issued and 18,435,218 outstanding at September 30, 2016 Common Stock, Value, Outstanding Common stock in treasury, at cost - 2,121,957 shares at March 31, 2017 and September 30, 2016 Treasury Stock, Value Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and stockholders' equity Liabilities and Equity Condensed Consolidated Statement of Shareholders’ Equity [Abstract] Condensed Consolidated Statement of Shareholders’ Equity [Abstract] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock [Member] Treasury Stock [Member] Treasury Stock [Member] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Accumulated Other Comprehensive Loss [Member] AOCI Attributable to Parent [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balances as of beginning of period Net income Other comprehensive loss Exercise of stock options Proceeds from Stock Options Excercised (including income tax benefit) Proceeds from Stock Options Excercised (including income tax benefit) Share-based Compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Balances as of end of period Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Business Acquisition, Contingent Consideration [Line Items] Business Acquisition, Contingent Consideration [Line Items] Business Combination, Contingent Consideration, Liability Business Combination, Contingent Consideration, Liability Change in fair value of contingent consideration for acquisitions Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Present Value of Estimated Total Purchase Price Present Value of Estimated Total Purchase Price Present Value of Estimated Total Purchase Price - The present value of the estimated total purchase price, including contingent consideration. Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Condensed Consolidated Balance Sheet Parentheticals [Abstract] Condensed Consolidated Balance Sheet Parentheticals [Abstract] Balance Sheet Parentheticals [Abstract] Securities and other assets segregated, fair value Securities and other assets segregated, fair value Securities and other assets segregated, fair value Dep and rec -exch clear org - fair value Deposits and receivables from exchange clearing orgs, fair value Deposits and receivables from exchange clearing orgs, fair value Dep and rec -b/d - fair value Deposits and receivables from bds and counterparties at fair value Deposits and receivables from b/ds and counterparties at fair value Physical commodities inventory at fair value Physical commodities inventory at fair value Physical commodities inventory at fair value - precious metals Collateral that can be sold or repledged Accounts pay and other accrued - fair value Accounts payable and other accrued liabilities - contingent consideration, fair value Accounts payable and other accrued liabilities - contingent consideration, fair value Payables to b/d - fair value Payables to b/ds and counterparties at fair value Payables to b/ds and counterparties at fair value Preferred stock - par value Preferred Stock, Par or Stated Value Per Share Preferred stock - authorized Preferred Stock, Shares Authorized Preferred stock - issued Preferred Stock, Shares Issued Preferred stock - outstanding Preferred Stock, Shares Outstanding Common stock - par value Common Stock, Par or Stated Value Per Share Common stock - authorized Common Stock, Shares Authorized Common stock - issued Common Stock, Shares, Issued Common stock - outstanding Common Stock, Shares, Outstanding Treasury stock - shares Treasury Stock, Shares Inventory, Current [Table] Inventory, Current [Table] Inventory [Line Items] Inventory [Line Items] Physical Ag & Energy(1) Agricultural Related Inventory Precious metals - held by non-broker-dealer subsidiaries(3) Finished commodities Inventory, Finished Goods, Net of Reserves Physical commodities inventory Inventory, Net Schedule of Goodwill [Table] Schedule of Goodwill [Table] Global Payments [Member] Foreign Exchange Segment [Member] Foreign Exchange Segment [Member] Goodwill [Line Items] Goodwill [Line Items] Goodwill Goodwill FCStone LLC [Member] FCStone LLC [Member] FCStone LLC [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Trade Names, Gross Finite-Lived Trade Names, Gross Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Fiscal 2016 (remaining nine months) Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Fiscal 2017 Finite-Lived Intangible Assets, Amortization Expense, Year Two Fiscal 2018 Finite-Lived Intangible Assets, Amortization Expense, Year Three Fiscal 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Four Fiscal 2020 and thereafter Finite-Lived Intangible Assets, Amortization Expense, Year Five Finite-Lived Intangible Assets, Net Finite-Lived Intangible Assets, Net Inventory Disclosure [Abstract] Schedule of Inventory, Current [Table Text Block] Schedule of Inventory, Current [Table Text Block] Debt Disclosure [Text Block] Debt Disclosure [Text Block] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Accretion Expense Accretion Expense General Insurance Expense General Insurance Expense Advertising Expense Advertising Expense Technology Services Costs Technology Services Costs Supplies and Postage Expense Supplies and Postage Expense Clearance Fees Clearance Fees Taxes, Miscellaneous Taxes, Miscellaneous Other Expenses Other Expenses Other Cost and Expense, Operating Operating Costs and Expenses Total Level 3 Assets Total Level 3 Assets Total Level 3 Assets Level 3 assets for which the company bears economic exposure Level 3 assets for which the company bears economic exposure Level 3 assets for which the company bears economic exposure Assets Total level 3 assets as a percentage of total assets Total level 3 assets as a percentage of total assets Total level 3 assets as a percentage of total assets Level 3 assets for which the company bears economic exposure as a percertange of total assets Level 3 assets for which the company bears economic exposure as a percertange of total assets Level 3 assets for which the company bears economic exposure as a percertange of total assets Total level 3 assets as a percentage of total financial assets at fair value Total level 3 assets as a percentage of total financial assets at fair value Total level 3 assets as a percentage of total financial assets at fair value Suriwongse Debt Investment Balance Suriwongse Debt Investment Balance Suriwongse Debt Investment Balance - Investment in Suriwongse hotel Segment Analysis [Abstract] Segment Analysis [Abstract] Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] Condensed Consolidated Cash Flows Statements [Abstract] Condensed Consolidated Cash Flows Statements [Abstract] Statement, Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash (used in) provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Bad debts Tangible Asset Impairment Charges Deferred income taxes Deferred Income Tax Expense (Benefit) Amortization of debt issuance costs and debt discount Amortization of Debt Issuance Costs and Discounts Amortization of stock-based compensation Share-based Compensation Loss on sale of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Changes in operating assets and liabilities, net: Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract] Cash, securities and other assets segregated under federal and other regulations Increase (Decrease) in Operating Assets Securities purchased under agreements to resell Increase (Decrease) in Receivables under Repurchase Agreements Increase (Decrease) in Securities Borrowed Increase (Decrease) in Securities Borrowed Deposits and receivables from exchange-clearing organizations Increase (Decrease) in Deposits Deposits and receivables from broker-dealers, clearing organizations, and counterparties Increase (Decrease) in Receivables from Brokers-Dealers and Clearing Organizations Receivables from customers, net Increase (Decrease) in Accounts Receivable Notes receivable, net Increase (Decrease) in Accounts and Notes Receivable Income taxes receivable Increase (Decrease) in Income Taxes Receivable Financial instruments owned, at fair value Increase (Decrease) in Financial Instruments Used in Operating Activities Physical commodities inventory Increase (Decrease) in Inventories Other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable and other accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Payables to customers Increase (Decrease) in Payables to Customers Payables to broker-dealers, clearing organizations and counterparties Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations Income taxes payable Increase (Decrease) in Income Taxes Payable Payables under repurchase agreements Increase (Decrease) in Payables under Repurchase Agreements Increase (Decrease) in Securities Loaned Transactions Increase (Decrease) in Securities Loaned Transactions Financial instruments sold, not yet purchased, at fair value Increase (Decrease) in Financial Instruments Sold, Not yet Purchased Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Cash paid for acquisitions, net Payments to Acquire Businesses, Net of Cash Acquired Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Net change in payable to lenders under loans Proceeds from (Repayments of) Debt Repayments of Unsecured Debt Repayments of Unsecured Debt Payments of note payable Repayments of Notes Payable Deferred payments on acquisitions Payments for (Proceeds from) Previous Acquisition Debt issuance costs Payments of Debt Issuance Costs Exercise of stock options Proceeds from Stock Options Exercised Share repurchases Payments for Repurchase of Common Stock Excess income tax benefit on stock options and awards Excess Tax Benefit from Share-based Compensation, Financing Activities Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rates on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents Net (decrease) increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid Income taxes paid, net of cash refunds Income Taxes Paid, Net Supplemental disclosure of non-cash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Identified intangible assets and goodwill on acquisitions Noncash or Part Noncash Acquisition, Intangible Assets Acquired Additional consideration payable related to acquisitions, net Acquisition of business: Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) [Abstract] Debt Issuance Costs, Net Debt Issuance Costs, Net Number of different types of foreign currencies Number of different types of foreign currencies Number of different types of foreign currencies the company trades Number of accounts for customers company-wide Number of accounts for customers company-wide The number of accounts for the customers the company provides services. Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Computer Software, Intangible Asset [Member] Computer Software, Intangible Asset [Member] Customer Relationships [Member] Customer Relationships [Member] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Finite-lived Intangible Assets Acquired Finite-lived Intangible Assets Acquired Finite-Lived Computer Software, Gross Capitalized Computer Software, Gross Finite-Lived Customer Lists, Gross Finite-Lived Customer Lists, Gross Finite-Lived Intangible Assets, Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Derivative Instruments and Hedging Activities Disclosure [Abstract] TBA securities purchased [Member] TBA securities purchased [Member] TBA securities purchased [Member] TBA securities sold [Member] TBA securities sold [Member] [Member] TBA securities sold [Member] Forward settling securities purchased [Member] Forward settling securities purchased [Member] Forward settling securities purchased [Member] Over the Counter (OTC) Commodity Contracts [Member] Forward settling securities sold [Member] Forward settling securities sold [Member] Derivative Liability, Notional Amount Derivative Liability, Notional Amount Derivative Asset, Notional Amount Derivative Asset, Notional Amount Income Taxes [Abstract] Income Taxes [Abstract] Deferred Tax Assets, Valuation Allowance Deferred Tax Assets, Valuation Allowance Income (Loss) from Continuing Operations before Income Taxes, Domestic Income (Loss) from Continuing Operations before Income Taxes, Domestic Deferred Tax Liabilities, Gross Deferred Tax Liabilities, Gross Deferred Tax Liabilities, Unrealized Gains on Trading Securities Deferred Tax Liabilities, Unrealized Gains on Trading Securities Income Tax Expense (Benefit) Income Tax Expense (Benefit) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Capital and Other Regulatory Requirements [Abstract] Capital and Other Regulatory Requirements [Abstract] Regulatory Capital Requirements under Banking Regulations [Text Block] Regulatory Capital Requirements under Banking Regulations [Text Block] reserve requirement [Axis] reserve requirement [Axis] reserve requirement [Axis] reserve requirement [Domain] reserve requirement [Domain] [Domain] for reserve requirement [Axis] Customer Reserve Requirement [Member] [Member] Customer Reserve Requirement [Member] [Member] Customer Reserve Requirement [Member] [Member] PAB Reserve Requirement [Member] PAB Reserve Requirement [Member] PAB Reserve Requirement [Member] Sterne Agee Clearing, Inc. [Member] Sterne Agee Clearing, Inc. [Member] Sterne Agee Clearing, Inc. [Member] Sterne Agee, and Leach, Inc [Member] Sterne Agee, and Leach, Inc [Member] Sterne Agee, and Leach, Inc [Member] Sterne Agee Financial Services, Inc. [Member] Sterne Agee Financial Services, Inc. [Member] Sterne Agee Financial Services, Inc. [Member] INTL FCStone Ltd [Member] INTL FCStone, Ltd [Member] INTL FCStone, Ltd (IFEL) [Member] INTL Netherlands BV [Member] INTL FCStone Europe [Member] INTL FCStone Europe [Member] INTL FCStone DTVM Ltda [Member] INTL FCStone DTVM Ltda [Member] INTL FCStone DTVM Ltda [Member] Gainvest S.A. Sociedad Gerente de FCI - Comision Nacional de Valores [Member] Gainvest S.A. Sociedad Gerente de FCI - Comision Nacional de Valores [Member] Gainvest S.A. Sociedad Gerente de FCI INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain] INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain] INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain] INTL Capital S.A. – General Inspector of Justice [Member] [Domain] INTL Capital S.A. – General Inspector of Justice [Member] [Domain] INTL Capital S.A. – General Inspector of Justice [Member] [Domain] INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain] INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain] INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain] Cash Reserve Deposit Required and Made Cash Reserve Deposit Required and Made Net Capital under Commodity Exchange Act Computation Required Net Capital under Commodity Exchange Act Net Capital Cash and Securities Segregated under Commodity Exchange Act Regulation Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated Secured Funds Secured Funds Secured funds Secured Funds Required Under Commodity Exchange Act Secured Funds Required Under Commodity Exchange Act Secured Funds Required Under Commodity Exchange Act Capital Required for Capital Adequacy Financing Receivables [Text Block] Financing Receivables [Text Block] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Repayments of Unsecured Debt Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Number of credit facilities Number of credit facilities Number of credit facilities available to the company. Segment Reporting Disclosure [Text Block] Segment Reporting Disclosure [Text Block] Inventory Adjustments Inventory Adjustments Fair Value Disclosures [Text Block] Fair Value Disclosures [Text Block] Exim Bank Notes Receivable [Abstract] Exim Bank Notes Receivable [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Short Term Notes Receivable Outstanding Balance Threshold, Percentage Short Term Notes Receivable Outstanding Balance Threshold, Percentage Short Term Notes Receivable Outstanding Balance Threshold, Percentage Insured short-term notes receivable Insured short-term notes receivable Insured short-term notes receivable Obligations for participation rights Obligations for participation rights The obligations the company has related to the sale of participations rights in short-term notes receivables. Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] Schedule of Derivative Instruments [Table Text Block] Schedule of Derivative Instruments [Table Text Block] Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block] Derivative Instruments, Gain (Loss) [Table Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Condensed Consolidated Income Statements [Abstract] Condensed Consolidated Income Statements [Abstract] Revenues: Revenues [Abstract] Sales of physical commodities Sales Revenue, Goods, Net Trading gains, net Trading Gain (Loss) Commission and clearing fees Fees and Commissions Consulting and management fees Asset Management Fees Interest income Interest Income, Operating Other income Other Income Total revenues Revenues Cost of sales of physical commodities Cost of Goods Sold Operating revenues Gross Profit Transaction-based clearing expenses Floor Brokerage, Exchange and Clearance Fees Introducing broker commissions Noninterest Expense Commission Expense Interest expense Interest Expense Net operating revenues Revenues, Net of Interest Expense Compensation and other expenses: Noninterest Expense [Abstract] Compensation and benefits Labor and Related Expense Communication and data services Communications and Information Technology Occupancy and equipment rental Occupancy, Net Professional fees Professional Fees Travel and business development Travel and Entertainment Expense Depreciation and amortization Depreciation, Depletion and Amortization Bad debts Provision for Doubtful Accounts and Impairment Charges Amount of the current period expense charged against operations, the offset which is generally to the allowance for doubtful accounts for the purpose of reducing receivables, including notes receivable, to an amount that approximates their net realizable value (the amount expected to be collected). In addition, it includes the charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value. Other Other Noninterest Expense Total compensation and other expenses Noninterest Expense Income before tax Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Net income Earnings per share: Earnings Per Share, Basic [Abstract] Basic Earnings Per Share, Basic Diluted Earnings Per Share, Diluted Weighted-average number of common shares outstanding: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Basic Weighted Average Number of Shares Outstanding, Basic Diluted Weighted Average Number of Shares Outstanding, Diluted Schedule of Goodwill [Table Text Block] Schedule of Goodwill [Table Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Comprehensive Income (Loss) Note [Text Block] Comprehensive Income (Loss) Note [Text Block] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Accumulated Translation Adjustment [Member] Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Line of Credit Facility [Table] Line of Credit Facility [Table] Main line of credit facilities [Member] Main line of credit facilities [Member] Main line of credit facilities [Member] HCO Syndicated line of credit facility [Member] HCO Syndicated line of credit facility [Member] HCO Syndicated line of credit facility [Member] FCS Margin line of credit facility [Member] FCS Margin line of credit facility [Member] FCS Margin line of credit facility [Member] FMS Sub-note commodity line of credit facility [Member] FMS Sub-note commodity line of credit facility [Member] FMS Sub-note commodity line of credit facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Line of Credit Facility, Current Borrowing Capacity Line of Credit Facility, Current Borrowing Capacity Short-term Debt Short-term Debt Proceeds from note payable Proceeds from Notes Payable Notes Payable to Bank Notes Payable to Bank Debt and Capital Lease Obligations Debt and Capital Lease Obligations Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Self Insurance Reserve Self Insurance Reserve Income Tax, Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Derivative, Notional Amount Derivative, Notional Amount Derivative, Average Remaining Maturity Derivative, Average Remaining Maturity Derivative, Number of Instruments Held Derivative, Number of Instruments Held Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Securities Segment [Member] Clearing and Execution Services Segment [Member] Clearing and Execution Services Segment [Member] Clearing and Execution Services Segment [Member] Corporate [Member] Corporate Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Revenues Operating revenues Net operating revenues Net Segment Contribution Net Segment Contribution Net segment contribution equals revenues less cost of sales, transaction-based clearing expenses, variable bonus compensation, introducing broker commissions and interest expense. Segment Income Segment Income Segment Income equals net contribution less non-variable direct segment costs. Costs not allocated to operating segments Costs not allocated to operating segments Costs not allocated to operating segments Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Net income Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent Less: Net income allocated to participating securities Undistributed Earnings Allocated to Participating Securities - Continuing Operations Undistributed Earnings Allocated to Participating Securities - Continuing Operations represents earnings from continuing operations allocated (not distributed) to participating securities under the two-class method to the extent that participating securities may share in earnings as if all of the earnings for the period had been distributed. Net income allocated to common shareholders Income from continuing operations allocated to common shareholders Income from continuing operations allocated to common shareholders represents income from continuing operations attributable to shareholders less allocation to participating securities plus interest on convertible debt less the allocation of the earnings from the interest on convertible debt to participating securities. Weighted average number of common shares outstanding Dilutive potential common shares outstanding: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted weighted-average shares Schedule of Other Operating Cost and Expense, by Component [Table Text Block] Schedule of Other Operating Cost and Expense, by Component [Table Text Block]