Basis of Presentation and Consolidation	3 Months Ended
Dec. 31, 2011
Basis of Presentation and Consolidation and Recently Issued Accounting Standards [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Basis of Presentation and Consolidation and Recently Issued Accounting Standards INTL FCStone Inc., a Delaware corporation, and its consolidated subsidiaries (collectively “INTL” or “the Company”), form a financial services group focused on domestic and select international markets. The Company’s services include comprehensive risk management advisory services for commercial customers; execution of listed futures and options on futures contracts on all major commodity exchanges; structured over-the-counter (“OTC”) products in a wide range of commodities; physical trading and hedging of precious and base metals and select other commodities; trading of more than 130 foreign currencies; market-making in international equities; debt origination and asset management. The Company provides these services to a diverse group of more than 20,000 customers located throughout the world, including producers, processors and end-users of nearly all widely-traded physical commodities to manage their risks and enhance margins; to commercial counterparties who are end-users of the firm’s products and services; to governmental and non-governmental organizations; and to commercial banks, brokers, institutional investors and major investment banks. Basis of Presentation and Consolidation The accompanying condensed consolidated balance sheet as of September 30, 2011, which has been derived from audited financial statements, and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and note disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to those rules and regulations. The Company believes that the disclosures made are adequate to make the information presented not misleading. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X. Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. It is suggested that these interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Form 10-K for the fiscal year ended September 30, 2011 filed with the SEC. These condensed consolidated financial statements include the accounts of INTL FCStone Inc. and its subsidiaries. Intercompany transactions and balances have been eliminated in consolidation. In accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"), the Company consolidates any variable interest entities for which it is the primary beneficiary, as defined. The Company applies the equity method of accounting when the Company does not have a controlling interest in an entity, but exerts significant influence over the entity. The Company had a majority interest in and was the general partner of the Blackthorn Multi-Advisor Fund, LP (the “Blackthorn Fund”), whose assets, liabilities, income and expenses were included within the Company's consolidated financial statements as of and for the year ended September 30, 2011. During the three months ended December 31, 2011, the Company requested and received approval for the full redemption of its remaining investment in the Blackthorn Fund effective December 31, 2011. As a result of the final redemption, the Company no longer retains any ownership interests in the Blackthorn Fund, has transferred its rights as general partner and deconsolidated its interest in the Blackthorn Fund as of December 31, 2011. The aggregate of the redemption amount and remaining noncontrolling interest less the carrying amount of the net assets of the Blackthorn Fund resulted in a nominal gain and was recorded as a component of trading gains on the consolidated condensed income statement for the three months ended December 31, 2011, as a result of the deconsolidation. Our fiscal year end is September 30, and our fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to our fiscal years and fiscal interim periods. The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments and investments, revenue recognition, the provision for potential losses from bad debts, valuation of inventories, valuation of goodwill and intangible assets, incomes taxes and contingencies. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. Reclassifications During the quarter ended March 31, 2011, the Company reclassified give-up fee revenue within the condensed consolidated income statement from 'consulting and management fees' to 'commission and clearing fees'. Reclassification in the amount of $0.9 million has been made to the three month period ended December 30, 2010, to conform to the current period presentation. This reclassification had no effect on previously reported total or net revenues. To conform to the current presentation of the information concerning the Company's operating segments, the Company has reclassified $1.1 million, for the three months ended December 31, 2010, of costs not allocated to operating segments as non-variable direct segment costs, impacting reported net segment income, see Note 16. Recent Accounting Pronouncements In January 2010, new guidance was issued to require new disclosures and clarify existing disclosure requirements about fair value measurements as set forth in the Fair Value Measurements and Disclosures Topic in the ASC. The guidance requires that a reporting entity should disclose separately the amounts of transfers in and out of Level 1 and Level 2 fair value measurements and describe the reasons for the transfers; and in the reconciliation for fair value measurements using significant unobservable inputs, a reporting entity should present separately information about purchases, sales, issuances, and settlements. In addition, the guidance clarifies that for purposes of reporting fair value measurement for each class of assets and liabilities, a reporting entity needs to use judgment in determining the appropriate classes of assets and liabilities; and a reporting entity should provide disclosures about the valuation techniques and inputs used to measure fair value for both recurring and nonrecurring fair value measurements. This guidance was effective for the Company as of the first interim period beginning after December 15, 2009, except for the detailed level 3 roll forward disclosure, which is effective for fiscal years beginning after December 15, 2010. The Company adopted the requirements of the disclosures during the quarter ended March 31, 2010, except for the detailed level 3 roll forward disclosures. The Company adopted the detailed level 3 roll forward disclosures beginning with the first quarter ended December 31, 2011. The adoption of this guidance did not have a material impact on the Company's disclosures in its condensed consolidated financial statements. In May 2011, the Financial Accounting Standards Board ("FASB") issued an update to the fair value measurement guidance to achieve common fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards ("IFRS"). The amendments in the update change the wording used to describe many of the requirements in U.S. GAAP for measuring fair value and for disclosing information about fair value measurements. The amendment is not intended to result in a change in the application of the requirements in the Fair Value Measurements Topic in the ASC. This guidance is effective for interim and annual periods beginning after December 15, 2011. Early application is permitted. The Company adopted this guidance as of the first quarter of fiscal year 2012. The adoption of this guidance did not have a significant impact on the Company's condensed consolidated financial statements. In June 2011, the FASB issued new guidance on the presentation of comprehensive income. This guidance eliminates the current option to report OCI and its components in the statement of changes in equity. Under this guidance, an entity can elect to present items of net income and OCI in one continuous statement or in two separate, but consecutive, statements. In addition, the guidance requires entities to show the effects of items reclassified from OCI to net income on the face of the financial statements. This guidance is effective for fiscal years beginning after December 15, 2011 and interim and annual periods thereafter. Early adoption is permitted, but full retrospective application is required. This guidance is effective for the Company's fiscal year beginning October 1, 2012 and all interim periods within that fiscal year. In December 2011, the FASB issued guidance that deferred the portion of the original guidance that required a company to separately present within net income reclassification adjustments of items out of accumulated other comprehensive income. The deferral is intended to be temporary until the FASB has time to reconsider these changes. The other provisions of the guidance will become effective as originally planned by the FASB. The Company is expecting to adopt this guidance in the first quarter of fiscal year 2013. As the Company reports comprehensive income within its condensed consolidated statements of stockholders' equity, the adoption of this guidance will result in a change in the presentation of comprehensive income in the Company's condensed consolidated financial statements. In September 2011, the FASB issued amended guidance on goodwill impairment testing. Under the revised guidance, entities testing goodwill for impairment have the option of performing a qualitative assessment, whether it is more likely than not (a likelihood of more than 50%) that the fair value of a reporting unit is less than its carrying amount, before calculating the fair value of the reporting unit. Because the qualitative assessment is optional, entities may bypass it for any reporting unit in any period and begin their impairment analysis with the quantitative calculation in step 1. The guidance does not change how goodwill is calculated or assigned to reporting units, nor does it revise the requirement to test goodwill annually for impairment. In addition, the guidance does not amend the requirement to test goodwill for impairment between annual tests if events or circumstances warrant, however, it does revise the examples of events and circumstances that an entity should consider. The amended guidance is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011. Early adoption is permitted. The Company adopted this guidance at the beginning of fiscal year 2012.The adoption of this guidance will not have a material impact on the Company's condensed consolidated financial statements. On December 16, 2011, the FASB issued new guidance on the disclosures about offsetting assets and liabilities. While the FASB retained the existing offsetting models under U.S. GAAP, the new standard requires disclosures to allow investors to better compare and understand significant quantitative differences in financial statements prepared under U.S. GAAP. The new standard is effective for annual periods beginning after January 1, 2013, and interim periods within those annual periods. Retrospective application is required. This guidance is effective for the Company's fiscal year beginning October 1, 2013. The Company is expecting to adopt this guidance starting with the first quarter of fiscal year 2014. The adoption of this guidance is expected to change some of the Company's disclosures within the notes to the condensed consolidated financial statements.

Basis of Presentation and Consolidation and Recently Issued Accounting Standards

INTL FCStone Inc., a Delaware corporation, and its consolidated subsidiaries (collectively “INTL” or “the Company”), form a financial services group focused on domestic and select international markets. The Company’s services include comprehensive risk management advisory services for commercial customers; execution of listed futures and options on futures contracts on all major commodity exchanges; structured over-the-counter (“OTC”) products in a wide range of commodities; physical trading and hedging of precious and base metals and select other commodities; trading of more than 130 foreign currencies; market-making in international equities; debt origination and asset management.

The Company provides these services to a diverse group of more than 20,000 customers located throughout the world, including producers, processors and end-users of nearly all widely-traded physical commodities to manage their risks and enhance margins; to commercial counterparties who are end-users of the firm’s products and services; to governmental and non-governmental organizations; and to commercial banks, brokers, institutional investors and major investment banks.

Basis of Presentation and Consolidation

The accompanying condensed consolidated balance sheet as of September 30, 2011, which has been derived from audited financial statements, and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and note disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to those rules and regulations. The Company believes that the disclosures made are adequate to make the information presented not misleading. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X.

Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. It is suggested that these interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Form 10-K for the fiscal year ended September 30, 2011 filed with the SEC.

These condensed consolidated financial statements include the accounts of INTL FCStone Inc. and its subsidiaries. Intercompany transactions and balances have been eliminated in consolidation. In accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"), the Company consolidates any variable interest entities for which it is the primary beneficiary, as defined.

The Company applies the equity method of accounting when the Company does not have a controlling interest in an entity, but exerts significant influence over the entity.

The Company had a majority interest in and was the general partner of the Blackthorn Multi-Advisor Fund, LP (the “Blackthorn Fund”), whose assets, liabilities, income and expenses were included within the Company's consolidated financial statements as of and for the year ended September 30, 2011. During the three months ended December 31, 2011, the Company requested and received approval for the full redemption of its remaining investment in the Blackthorn Fund effective December 31, 2011. As a result of the final redemption, the Company no longer retains any ownership interests in the Blackthorn Fund, has transferred its rights as general partner and deconsolidated its interest in the Blackthorn Fund as of December 31, 2011. The aggregate of the redemption amount and remaining noncontrolling interest less the carrying amount of the net assets of the Blackthorn Fund resulted in a nominal gain and was recorded as a component of trading gains on the consolidated condensed income statement for the three months ended December 31, 2011, as a result of the deconsolidation.

Our fiscal year end is September 30, and our fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to our fiscal years and fiscal interim periods.

The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments and investments, revenue recognition, the provision for potential losses from bad debts, valuation of inventories, valuation of goodwill and intangible assets, incomes taxes and contingencies. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates.

Reclassifications

During the quarter ended March 31, 2011, the Company reclassified give-up fee revenue within the condensed consolidated income statement from 'consulting and management fees' to 'commission and clearing fees'. Reclassification in the amount of $0.9 million has been made to the three month period ended December 30, 2010, to conform to the current period presentation. This reclassification had no effect on previously reported total or net revenues.

To conform to the current presentation of the information concerning the Company's operating segments, the Company has reclassified $1.1 million, for the three months ended December 31, 2010, of costs not allocated to operating segments as non-variable direct segment costs, impacting reported net segment income, see Note 16.

Recent Accounting Pronouncements

In January 2010, new guidance was issued to require new disclosures and clarify existing disclosure requirements about fair value measurements as set forth in the Fair Value Measurements and Disclosures Topic in the ASC. The guidance requires that a reporting entity should disclose separately the amounts of transfers in and out of Level 1 and Level 2 fair value measurements and describe the reasons for the transfers; and in the reconciliation for fair value measurements using significant unobservable inputs, a reporting entity should present separately information about purchases, sales, issuances, and settlements. In addition, the guidance clarifies that for purposes of reporting fair value measurement for each class of assets and liabilities, a reporting entity needs to use judgment in determining the appropriate classes of assets and liabilities; and a reporting entity should provide disclosures about the valuation techniques and inputs used to measure fair value for both recurring and nonrecurring fair value measurements. This guidance was effective for the Company as of the first interim period beginning after December 15, 2009, except for the detailed level 3 roll forward disclosure, which is effective for fiscal years beginning after December 15, 2010. The Company adopted the requirements of the disclosures during the quarter ended March 31, 2010, except for the detailed level 3 roll forward disclosures. The Company adopted the detailed level 3 roll forward disclosures beginning with the first quarter ended December 31, 2011. The adoption of this guidance did not have a material impact on the Company's disclosures in its condensed consolidated financial statements.

In May 2011, the Financial Accounting Standards Board ("FASB") issued an update to the fair value measurement guidance to achieve common fair value measurement and disclosure requirements in U.S. GAAP and International Financial Reporting Standards ("IFRS"). The amendments in the update change the wording used to describe many of the requirements in U.S. GAAP for measuring fair value and for disclosing information about fair value measurements. The amendment is not intended to result in a change in the application of the requirements in the Fair Value Measurements Topic in the ASC. This guidance is effective for interim and annual periods beginning after December 15, 2011. Early application is permitted. The Company adopted this guidance as of the first quarter of fiscal year 2012. The adoption of this guidance did not have a significant impact on the Company's condensed consolidated financial statements.

In June 2011, the FASB issued new guidance on the presentation of comprehensive income. This guidance eliminates the current option to report OCI and its components in the statement of changes in equity. Under this guidance, an entity can elect to present items of net income and OCI in one continuous statement or in two separate, but consecutive, statements. In addition, the guidance requires entities to show the effects of items reclassified from OCI to net income on the face of the financial statements. This guidance is effective for fiscal years beginning after December 15, 2011 and interim and annual periods thereafter. Early adoption is permitted, but full retrospective application is required. This guidance is effective for the Company's fiscal year beginning October 1, 2012 and all interim periods within that fiscal year. In December 2011, the FASB issued guidance that deferred the portion of the original guidance that required a company to separately present within net income reclassification adjustments of items out of accumulated other comprehensive income. The deferral is intended to be temporary until the FASB has time to reconsider these changes. The other provisions of the guidance will become effective as originally planned by the FASB. The Company is expecting to adopt this guidance in the first quarter of fiscal year 2013. As the Company reports comprehensive income within its condensed consolidated statements of stockholders' equity, the adoption of this guidance will result in a change in the presentation of comprehensive income in the Company's condensed consolidated financial statements.

In September 2011, the FASB issued amended guidance on goodwill impairment testing. Under the revised guidance, entities testing goodwill for impairment have the option of performing a qualitative assessment, whether it is more likely than not (a likelihood of more than 50%) that the fair value of a reporting unit is less than its carrying amount, before calculating the fair value of the reporting unit. Because the qualitative assessment is optional, entities may bypass it for any reporting unit in any period and begin their impairment analysis with the quantitative calculation in step 1. The guidance does not change how goodwill is calculated or assigned to reporting units, nor does it revise the requirement to test goodwill annually for impairment. In addition, the guidance does not amend the requirement to test goodwill for impairment between annual tests if events or circumstances warrant, however, it does revise the examples of events and circumstances that an entity should consider. The amended guidance is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011. Early adoption is permitted. The Company adopted this guidance at the beginning of fiscal year 2012.The adoption of this guidance will not have a material impact on the Company's condensed consolidated financial statements.

On December 16, 2011, the FASB issued new guidance on the disclosures about offsetting assets and liabilities. While the FASB retained the existing offsetting models under U.S. GAAP, the new standard requires disclosures to allow investors to better compare and understand significant quantitative differences in financial statements prepared under U.S. GAAP. The new standard is effective for annual periods beginning after January 1, 2013, and interim periods within those annual periods. Retrospective application is required. This guidance is effective for the Company's fiscal year beginning October 1, 2013. The Company is expecting to adopt this guidance starting with the first quarter of fiscal year 2014. The adoption of this guidance is expected to change some of the Company's disclosures within the notes to the condensed consolidated financial statements.