Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Notes)	3 Months Ended
Dec. 31, 2015
Basis of Presentation and Consolidation [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 diversified, global financial services organization providing financial products and advisory and execution services to help clients access market liquidity, maximize profits and manage risk. 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 metals and select other commodities; trading of more than 150 foreign currencies; market-making in international equities; fixed income; debt origination and asset management. The Company provides these services to a diverse group of more than 20,000 accounts, representing approximately 11,000 consolidated clients 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, 2015, 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, 2015 filed with the SEC. 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. The Company’s 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. 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, self-insurance liabilities, 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. Change in Precious Metals Accounting The Company engages in trading activities in a variety of physical commodities, including actively trading precious metals whereby the Company provides a full range of trading and hedging capabilities, including OTC products, to select producers, consumers, and investors. In the Company’s precious metals trading activities, it acts as a principal, committing its own capital to buy and sell precious metals on a spot and forward basis. On April 10, 2015 (the “transfer date”), the Company transitioned the portion of its precious metals business conducted through its unregulated domestic subsidiary, INTL Commodities Inc., to its United Kingdom based broker-dealer subsidiary, INTL FCStone Ltd. INTL FCStone Ltd is regulated by the Financial Conduct Authority (“FCA”), the regulator of the financial services industry in the United Kingdom. In anticipation of the transfer of the precious metals business, INTL Commodities Inc. liquidated all of its precious metals inventory as of the transfer date. Subsequent to the transfer, precious metals inventory held by INTL FCStone Ltd. is measured at fair value, with changes in fair value included as a component of ‘trading gains, net’ on the condensed consolidated income statement, in accordance with U.S. GAAP accounting requirements for broker-dealers. Precious metals inventory held by subsidiaries that are not broker-dealers continues to be valued at the lower of cost or market value. Prior to the transfer, INTL Commodities Inc. precious metals sales and costs of sales were recorded on a gross basis in accordance with the Revenue Recognition Topic of the ASC. Subsequent to the transfer, INTL FCStone Ltd. precious metals sales and cost of sales are presented on a net basis and included as a component of ‘trading gains, net’ on the condensed consolidated income statements, in accordance with U.S GAAP accounting requirements for broker-dealers. Precious metals sales and cost of sales for subsidiaries that are not broker-dealers continue to be recorded on a gross basis. The change has no effect on the Company’s operating revenues, income from continuing operations, or net income. Management has historically assessed the performance of the physical commodities businesses on an operating revenue basis, and continues to do so. Recent Accounting Pronouncements In January 2016, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance addressing the recognition, measurement, presentation and disclosure of financial assets and liabilities. The guidance primarily affects the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. In addition, the guidance clarifies the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. This guidance is effective for the Company in the first quarter of fiscal 2019, and early adoption is not permitted, with certain exceptions. The amendments are required to be applied by means of a cumulative-effect adjustment on the balance sheet as of the beginning of the fiscal year of adoption. The Company is currently assessing the impact, if any, the guidance may have upon adoption.

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 diversified, global financial services organization providing financial products and advisory and execution services to help clients access market liquidity, maximize profits and manage risk. 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 metals and select other commodities; trading of more than 150 foreign currencies; market-making in international equities; fixed income; debt origination and asset management.

The Company provides these services to a diverse group of more than 20,000 accounts, representing approximately 11,000 consolidated clients 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, 2015, 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, 2015 filed with the SEC.

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.

The Company’s 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.

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, self-insurance liabilities, 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.

Change in Precious Metals Accounting

The Company engages in trading activities in a variety of physical commodities, including actively trading precious metals whereby the Company provides a full range of trading and hedging capabilities, including OTC products, to select producers, consumers, and investors. In the Company’s precious metals trading activities, it acts as a principal, committing its own capital to buy and sell precious metals on a spot and forward basis.

On April 10, 2015 (the “transfer date”), the Company transitioned the portion of its precious metals business conducted through its unregulated domestic subsidiary, INTL Commodities Inc., to its United Kingdom based broker-dealer subsidiary, INTL FCStone Ltd. INTL FCStone Ltd is regulated by the Financial Conduct Authority (“FCA”), the regulator of the financial services industry in the United Kingdom.

In anticipation of the transfer of the precious metals business, INTL Commodities Inc. liquidated all of its precious metals inventory as of the transfer date. Subsequent to the transfer, precious metals inventory held by INTL FCStone Ltd. is measured at fair value, with changes in fair value included as a component of ‘trading gains, net’ on the condensed consolidated income statement, in accordance with U.S. GAAP accounting requirements for broker-dealers. Precious metals inventory held by subsidiaries that are not broker-dealers continues to be valued at the lower of cost or market value.

Prior to the transfer, INTL Commodities Inc. precious metals sales and costs of sales were recorded on a gross basis in accordance with the Revenue Recognition Topic of the ASC. Subsequent to the transfer, INTL FCStone Ltd. precious metals sales and cost of sales are presented on a net basis and included as a component of ‘trading gains, net’ on the condensed consolidated income statements, in accordance with U.S GAAP accounting requirements for broker-dealers. Precious metals sales and cost of sales for subsidiaries that are not broker-dealers continue to be recorded on a gross basis.

The change has no effect on the Company’s operating revenues, income from continuing operations, or net income. Management has historically assessed the performance of the physical commodities businesses on an operating revenue basis, and continues to do so.

Recent Accounting Pronouncements

In January 2016, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance addressing the recognition, measurement, presentation and disclosure of financial assets and liabilities. The guidance primarily affects the accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. In addition, the guidance clarifies the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. This guidance is effective for the Company in the first quarter of fiscal 2019, and early adoption is not permitted, with certain exceptions. The amendments are required to be applied by means of a cumulative-effect adjustment on the balance sheet as of the beginning of the fiscal year of adoption. The Company is currently assessing the impact, if any, the guidance may have upon adoption.