Commitments and Contingencies (Notes)	6 Months Ended
Mar. 31, 2016
Commitments and Contingencies [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Commitments and Contingencies Legal Proceedings From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the policy limits of the insurance. As of March 31, 2016 and September 30, 2015, the condensed consolidated balance sheets include loss contingency accruals recorded prior to these periods then ended, which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, is not likely to be material to the Company’s earnings, financial position or liquidity. Sentinel Litigation Prior to its July 1, 2015 merger into INTL FCStone Financial Inc., the Company’s subsidiary FCStone, LLC, had a portion of its excess segregated funds invested with Sentinel Management Group Inc. (“Sentinel”), a registered futures commission merchant (“FCM”) and an Illinois-based money manager that provided cash management services to other FCMs. In August 2007, Sentinel halted redemptions to customers and sold certain of the assets it managed to an unaffiliated third party at a significant discount. On August 17, 2007, subsequent to Sentinel’s sale of certain assets, Sentinel filed for bankruptcy protection. In aggregate,$15.5 million of FCStone, LLC’s $21.9 million in invested funds were returned to it before and after Sentinel’s bankruptcy petition. In August 2008, the bankruptcy trustee of Sentinel filed adversary proceedings against FCStone, LLC, and a number of other FCMs in the Bankruptcy Court for the Northern District of Illinois. The case was subsequently reassigned to the United States District Court, for the Northern District of Illinois. In the complaint, the trustee is seeking avoidance of alleged transfers or withdrawals of funds received by FCStone, LLC and other FCMs within 90 days prior to the filing of the Sentinel bankruptcy petition, as well as avoidance of post-petition distributions and disallowance of the proof of claim filed by FCStone, LLC. The trustee seeks recovery of pre- and post-petition transfers totaling approximately $15.5 million. The trial of this matter took place, as a test case, during October 2012. The trial court entered a judgment against FCStone, LLC on January 4, 2013. On January 17, 2013, the trial court entered an agreed order, staying execution and enforcement, pending an appeal of the judgment. On March 19, 2014, the appeal court ruled in favor of FCStone, LLC. On April 16, 2014, the trustee filed a petition for rehearing of the appeal. On May 19, 2014, the U.S. Court of Appeals for the Seventh Circuit denied the petition. The trustee did not file a writ for certiorari with the U.S. Supreme Court during the time allotted to do so. On February 10, 2015, based on a new theory, the trustee filed a motion for judgment against FCStone, LLC in the United States District Court, for the Northern District of Illinois, seeking to claw back the post-petition transfer of $14.5 million and to recover the funds held in reserve in the name of FCStone, LLC. FCStone, LLC filed its opposition brief and an associated motion for judgment on March 17, 2015. The trustee filed its reply briefs on April 7, 2015 and the Company filed its reply briefs on April 22, 2015. On March 28, 2016 the United States District Court for the Northern District of Illinois entered an order in favor of FCStone, LLC (now INTL FCStone Financial Inc.) and against the Trustee on the Trustee’s post-petition claim, in light of the Seventh Circuit’s opinion. The same court ruled against INTL FCStone Financial and in favor of the Trustee with respect to the funds held in reserve accounts. On April 25, 2016, INTL FCStone Financial filed a Notice of Appeal to the United States Court of Appeals for the Seventh Circuit relating to the portion of the final judgment dated March 28, 2016 of the district court and INTL FCStone Financial’s claim to funds in reserve accounts. On April 26, 2016, the Trustee filed a Notice of Appeal from the March 28, 2016 final judgment of the district court. The Company has determined that losses related to the Trustee’s appeal are neither probable nor reasonably possible. The Company believes the case is without merit and intends to defend itself vigorously. Our assessments are based on estimates and assumptions that have been deemed reasonable by management, but that may later prove to be incomplete or inaccurate, and unanticipated events and circumstances may occur that might cause us to change those estimates and assumptions. Contractual Commitments Contingent Liabilities - Acquisitions Under the terms of the purchase agreements related to the acquisitions listed below, the Company has obligations to pay additional consideration if specific conditions and earnings targets are met. In accordance with the Business Combinations Topic of the ASC, the fair value of the additional consideration is recognized as a contingent liability as of the acquisition date. The contingent liability for these estimated additional purchase price considerations of $1.5 million and $3.3 million are included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheets as of March 31, 2016 and September 30, 2015. The acquisition date fair value of additional consideration is remeasured to its fair value each reporting period, with changes in fair value recorded in current earnings. The change in fair value during the six months ended March 31, 2016 and 2015 were increases of $0.3 million and $0.2 million, respectively, and are included in ‘other’ in the condensed consolidated income statements. The Company has a contingent liability relating to the December 2012 acquisition of the accounts of Tradewire Securities, LLC, which may result in the payment of additional purchase price consideration. The present value of the estimated total purchase price, including contingent consideration, is $4.5 million as of March 31, 2016, of which $0.9 million remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheet. The Company has a contingent liability relating to the January 2015 acquisition of G.X. Clarke, which may result in the payment of additional purchase price consideration. The contingent consideration, which in no event shall exceed $1.5 million, is expected to be paid in two payments. The present value of the estimated total purchase price, including contingent consideration, is $28.5 million as of March 31, 2016, of which $0.6 million remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheet. Self-Insurance The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. As of March 31, 2016, the Company had $1.1 million accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.

Commitments and Contingencies

Legal Proceedings

From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the policy limits of the insurance.

As of March 31, 2016 and September 30, 2015, the condensed consolidated balance sheets include loss contingency accruals recorded prior to these periods then ended, which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, is not likely to be material to the Company’s earnings, financial position or liquidity.

Sentinel Litigation

Prior to its July 1, 2015 merger into INTL FCStone Financial Inc., the Company’s subsidiary FCStone, LLC, had a portion of its excess segregated funds invested with Sentinel Management Group Inc. (“Sentinel”), a registered futures commission merchant (“FCM”) and an Illinois-based money manager that provided cash management services to other FCMs. In August 2007, Sentinel halted redemptions to customers and sold certain of the assets it managed to an unaffiliated third party at a significant discount. On August 17, 2007, subsequent to Sentinel’s sale of certain assets, Sentinel filed for bankruptcy protection. In aggregate,$15.5 million of FCStone, LLC’s $21.9 million in invested funds were returned to it before and after Sentinel’s bankruptcy petition.

In August 2008, the bankruptcy trustee of Sentinel filed adversary proceedings against FCStone, LLC, and a number of other FCMs in the Bankruptcy Court for the Northern District of Illinois. The case was subsequently reassigned to the United States District Court, for the Northern District of Illinois. In the complaint, the trustee is seeking avoidance of alleged transfers or withdrawals of funds received by FCStone, LLC and other FCMs within 90 days prior to the filing of the Sentinel bankruptcy petition, as well as avoidance of post-petition distributions and disallowance of the proof of claim filed by FCStone, LLC. The trustee seeks recovery of pre- and post-petition transfers totaling approximately $15.5 million.

The trial of this matter took place, as a test case, during October 2012. The trial court entered a judgment against FCStone, LLC on January 4, 2013. On January 17, 2013, the trial court entered an agreed order, staying execution and enforcement, pending an appeal of the judgment. On March 19, 2014, the appeal court ruled in favor of FCStone, LLC. On April 16, 2014, the trustee filed a petition for rehearing of the appeal. On May 19, 2014, the U.S. Court of Appeals for the Seventh Circuit denied the petition. The trustee did not file a writ for certiorari with the U.S. Supreme Court during the time allotted to do so.

On February 10, 2015, based on a new theory, the trustee filed a motion for judgment against FCStone, LLC in the United States District Court, for the Northern District of Illinois, seeking to claw back the post-petition transfer of $14.5 million and to recover the funds held in reserve in the name of FCStone, LLC. FCStone, LLC filed its opposition brief and an associated motion for judgment on March 17, 2015. The trustee filed its reply briefs on April 7, 2015 and the Company filed its reply briefs on April 22, 2015.

On March 28, 2016 the United States District Court for the Northern District of Illinois entered an order in favor of FCStone, LLC (now INTL FCStone Financial Inc.) and against the Trustee on the Trustee’s post-petition claim, in light of the Seventh Circuit’s opinion. The same court ruled against INTL FCStone Financial and in favor of the Trustee with respect to the funds held in reserve accounts.

On April 25, 2016, INTL FCStone Financial filed a Notice of Appeal to the United States Court of Appeals for the Seventh Circuit relating to the portion of the final judgment dated March 28, 2016 of the district court and INTL FCStone Financial’s claim to funds in reserve accounts. On April 26, 2016, the Trustee filed a Notice of Appeal from the March 28, 2016 final judgment of the district court.

The Company has determined that losses related to the Trustee’s appeal are neither probable nor reasonably possible. The Company believes the case is without merit and intends to defend itself vigorously.

Our assessments are based on estimates and assumptions that have been deemed reasonable by management, but that may later prove to be incomplete or inaccurate, and unanticipated events and circumstances may occur that might cause us to change those estimates and assumptions.

Contractual Commitments

Contingent Liabilities - Acquisitions

Under the terms of the purchase agreements related to the acquisitions listed below, the Company has obligations to pay additional consideration if specific conditions and earnings targets are met. In accordance with the Business Combinations Topic of the ASC, the fair value of the additional consideration is recognized as a contingent liability as of the acquisition date. The contingent liability for these estimated additional purchase price considerations of $1.5 million and $3.3 million are included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheets as of March 31, 2016 and September 30, 2015. The acquisition date fair value of additional consideration is remeasured to its fair value each reporting period, with changes in fair value recorded in current earnings. The change in fair value during the six months ended March 31, 2016 and 2015 were increases of $0.3 million and $0.2 million, respectively, and are included in ‘other’ in the condensed consolidated income statements.

The Company has a contingent liability relating to the December 2012 acquisition of the accounts of Tradewire Securities, LLC, which may result in the payment of additional purchase price consideration. The present value of the estimated total purchase price, including contingent consideration, is $4.5 million as of March 31, 2016, of which $0.9 million remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheet.

The Company has a contingent liability relating to the January 2015 acquisition of G.X. Clarke, which may result in the payment of additional purchase price consideration. The contingent consideration, which in no event shall exceed $1.5 million, is expected to be paid in two payments. The present value of the estimated total purchase price, including contingent consideration, is $28.5 million as of March 31, 2016, of which $0.6 million remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheet.

Self-Insurance

The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. As of March 31, 2016, the Company had $1.1 million accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.