Basis of Presentation and Consolidation and Recently Issued Accounting Standards Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2012
Basis of Presentation and Consolidation [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The accompanying condensed consolidated balance sheet as of September 30, 2012, 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, 2012 filed with the SEC.
Consolidation, Policy [Policy Text Block]	These condensed consolidated financial statements include the accounts of INTL FCStone Inc. and all other entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation.
Fiscal Period, Policy [Policy Text Block]	fiscal year end is September 30, and the fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to fiscal years and fiscal interim periods.
Use of Estimates, Policy [Policy Text Block]	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.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements In June 2011, the Financial Accounting Standards Board ("FASB") issued new guidance on the presentation of comprehensive income. This guidance eliminates the current option to report comprehensive income and its components in the statement of changes in equity. Under this guidance, an entity can elect to present items of net income and comprehensive income 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 accumulated other comprehensive loss 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 was effective in the Company's first quarter of fiscal year 2013. 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 loss. The deferral is intended to be temporary until the FASB has time to reconsider these changes. The other provisions of this guidance became effective as originally planned by the FASB. The Company adopted this guidance in the first quarter of fiscal year 2013, and the Company elected the two statement approach. The application of this guidance relates to presentation only and did not have a significant 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 on or 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 expects 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 its condensed consolidated financial statements. In July 2012, the FASB issued final guidance on indefinite-lived intangible assets impairment testing. Under the guidance, entities testing indefinite-lived intangibles for impairment have the option of first performing a qualitative assessment to determine whether it is more likely than not that an indefinite-lived intangible asset is impaired. If a company determines that it is more likely than not that the fair value of such an asset exceeds its carrying amount, it would not need to calculate the fair value of the asset in that year. However, if a company concludes otherwise, it must calculate the fair value of the asset, compare that value with its carrying amount and record an impairment charge, if any. The guidance does not revise the requirement to test indefinite-lived intangible assets annually for impairment. In addition, the guidance does not amend the requirement to test indefinite-lived intangible assets 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 guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012. Early adoption is permitted. The Company is currently evaluating the impact of this guidance, however, it is expected that the adoption of this guidance will not have a material impact on the Company's condensed consolidated financial statements.

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2197480

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-URI http://asc.fasb.org/subtopic&trid=2197087

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 2-6

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2196966

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 40

-Section 45

-URI http://asc.fasb.org/section&trid=2197723

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 5, 6, 16-19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 46R

-Paragraph 4

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph k

-Article 1

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=18733093&loc=d3e5614-111684

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33801-111570

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 46R

-Paragraph 14, 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 46R

-Paragraph 4

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 46

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 15: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.3A-02)

-URI http://asc.fasb.org/extlink&oid=6959686&loc=d3e355033-122828

Reference 16: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 96-16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 17: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

Reference 18: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02, 03

-Article 3A

Reference 19: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 97-2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Disclosure of accounting policy for determining an entity's fiscal year or other fiscal period. This disclosure may include identification of the fiscal period end-date, the length of the fiscal period, any reporting period lag between the entity and its subsidiaries, or equity investees. If a reporting lag exists, the closing date of the entity having a different period end is generally noted, along with an explanation of the necessity for using different closing dates. Any intervening events that materially affect the entity's financial position or results of operations are generally also disclosed.

+ References+ Details

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

+ References+ Details