StoneX (SNEX) 10-Q 7 May 14 2014 Q2 Quarterly report Financial data

DEI

DEI	6 Months Ended
	Mar. 31, 2014	6-May-14
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'INTL FCSTONE INC.	'
Trading Symbol	'INTL	'
Entity Central Index Key	'0000913760	'
Current Fiscal Year End Date	'--09-30	'
Entity Filer Category	'Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	18,864,677
Entity Well-known Seasoned Issuer	'No	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
ASSETS	'	'
Cash and cash equivalents	$169.20	$156.10
Cash, securities and other assets segregated under federal and other regulations (including $31.9 and $107.6 at fair value at March 31, 2014 and September 30, 2013, respectively)	715.7	449.4
Deposits and receivables from:	'	'
Exchange-clearing organizations (including $1,185.2 and $1,371.7 at fair value at March 31, 2014 and September 30, 2013, respectively)	1,488.70	1,576.60
Broker-dealers, clearing organizations and counterparties (including $(5.2) and $(13.1) at fair value at March 31, 2014 and September 30, 2013, respectively)	128.3	168.3
Receivables from customers, net	70.3	93.3
Notes receivable, net	65	37.4
Income taxes receivable	12.8	15.5
Financial instruments owned, at fair value	156.2	158.5
Physical commodities inventory	67.9	59
Deferred income taxes, net	29	25.5
Property and equipment, net	17.4	17.5
Goodwill and intangible assets, net	58.5	59.1
Other assets	36.1	31.8
Total assets	3,015.10	2,848
Liabilities:	'	'
Accounts payable and other accrued liabilities (including $9.2 and $9.6 at fair value at March 31, 2014 and September 30, 2013, respectively)	95.6	114
Payables to:	'	'
Customers	2,268	2,091.80
Broker-dealers, clearing organizations and counterparties	4.6	17
Lenders under loans and overdrafts	40.5	61
Senior unsecured notes	45.5	45.5
Income taxes payable	5.4	3.4
Financial instruments sold, not yet purchased, at fair value	217.5	179.9
Deferred income taxes	0.1	0
Total liabilities	2,677.20	2,512.60
Commitments and contingencies (Note 11)	'	'
Stockholders' Equity:	'	'
Preferred stock, $.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding	0	0
Common stock, $.01 par value. Authorized 30,000,000 shares; 19,799,361 issued and 18,983,574 outstanding at March 31, 2014 and 19,638,330 issued and 19,209,157 outstanding at September 30, 2013	0.2	0.2
Common stock in treasury, at cost - 815,787 shares at March 31, 2014 and 429,173 shares at September 30, 2013, respectively	-15	-7.8
Additional paid-in capital	227.4	224
Retained earnings	135.4	125.4
Accumulated other comprehensive loss, net	-10.1	-6.4
Total stockholders' equity	337.9	335.4
Total liabilities and equity	$3,015.10	$2,848

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets Parentheticals (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, except Share data, unless otherwise specified
Balance Sheet Parentheticals [Abstract]	'	'
Securities and other assets segregated, fair value	$31.90	$107.60
Dep and rec -exch clear org - fair value	1,185.20	1,371.70
Dep and rec -b/d - fair value	-5.2	-13.1
Accounts pay and other accrued - fair value	$9.20	$9.60
Preferred stock - par value	$0.01	$0.01
Preferred stock - authorized	1,000,000	1,000,000
Preferred stock - issued	0	0
Preferred stock - outstanding	0	0
Common stock - par value	$0.01	$0.01
Common stock - authorized	30,000,000	30,000,000
Common stock - issued	19,799,361	19,638,330
Common stock - outstanding	18,983,574	19,209,157
Treasury stock - shares	815,787	429,173

Condensed_Consolidated_Income_

Condensed Consolidated Income Statements (USD $)	3 Months Ended		6 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Revenues:	'	'	'	'
Sales of physical commodities	$8,329.40	$11,662.10	$16,130.60	$23,675.20
Trading gains, net	64.7	53.1	116.4	126.3
Commission and clearing fees	47.3	43.4	89.5	83.4
Consulting and management fees	9.5	7.7	21.5	16
Interest income	1.9	2.8	3.3	5.6
Other income	0.1	0.2	0.3	0.3
Total revenues	8,452.90	11,769.30	16,361.60	23,906.80
Cost of sales of physical commodities	8,323.70	11,654.40	16,119.50	23,673.50
Operating revenues	129.2	114.9	242.1	233.3
Clearing and related expenses	27.7	28.6	52.9	53.2
Introducing broker commissions	12.8	9.6	24.4	18
Interest expense	2.8	1.6	5.5	3.7
Net operating revenues	85.9	75.1	159.3	158.4
Compensation and other expenses:	'	'	'	'
Compensation and benefits	52.7	51.1	99	97
Communication and data services	6.2	5.8	12.4	11
Occupancy and equipment rental	3.2	3.2	6.2	6.1
Professional fees	4.1	3.2	8.4	6.8
Travel and business development	2	2.2	4.8	5
Depreciation and amortization	1.7	2.3	3.6	4.1
Bad debts and impairments	0.4	-0.3	0.7	0.1
Other	5.3	5.9	10	12.6
Total compensation and other expenses	75.6	73.4	145.1	142.7
Income from continuing operations, before tax	10.3	1.7	14.2	15.7
Income tax expense	2.6	0	4.1	3.9
Net income from continuing operations	7.7	1.7	10.1	11.8
(Loss) income from discontinued operations, net of tax	-0.2	-0.2	-0.1	3
Net income	$7.50	$1.50	$10	$14.80
Basic earnings per share:	'	'	'	'
Income from continuing operations	$0.40	$0.09	$0.53	$0.62
(Loss) income from discontinued operations	($0.01)	($0.01)	($0.01)	$0.16
Net income per common share	$0.39	$0.08	$0.52	$0.78
Diluted earnings per share:	'	'	'	'
Income from continuing operations	$0.40	$0.09	$0.52	$0.61
(Loss) income from discontinued operations	($0.01)	($0.01)	($0.01)	$0.15
Net income per common share	$0.39	$0.08	$0.51	$0.76
Weighted-average number of common shares outstanding:	'	'	'	'
Basic	18,609,550	18,380,971	18,627,383	18,327,517
Diluted	18,955,128	18,834,592	19,274,153	18,821,799

Condensed_Consolidated_Stateme

Condensed Consolidated Statement of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]	'	'	'	'
Net income	$7.50	$1.50	$10	$14.80
Other comprehensive income (loss), net of tax:	'	'	'	'
Foreign currency translation adjustment	-2.7	-0.3	-3.9	-0.6
Pension liabilities adjustment	0.1	0	0.2	0.4
Net unrealized loss on available-for-sale securities	-0.2	0.4	0	0.2
Reclassification of adjustment for gains included in net income [Abstract]	'	'	'	'
Foreign currency transaction adjustment (included in other income)	0	-0.1	'	-0.1
Realized gain on available-for-sale securities (included in trading gains, net)	0	0	'	-8.3
Income tax expense from reclassification adjustments (included in income tax expense)	0	0	0	2
Reclassification adjustment for gains included in net income	0	-0.1	0	-6.4
Other comprehensive loss	-2.8	0	-3.7	-6.4
Comprehensive income	$4.70	$1.50	$6.30	$8.40

Condensed_Consolidated_Cash_Fl

Condensed Consolidated Cash Flows Statements (USD $)	6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:	'	'
Net income	$10	$14.80
Adjustments to reconcile net income to net cash provided by (used in) operating activities:	'	'
Depreciation and amortization	3.5	4.1
Provision for bad debts and impairments	0.7	0.1
Deferred income taxes	-3.5	-0.3
Amortization of debt issuance costs and debt discount	0.5	0.6
Amortization of stock-based compensation expense	2.2	3.5
Loss on sale of property and equipment	0.2	0
Gain on sale of exchange memberships and common stock	0	-9.2
Changes in operating assets and liabilities, net:	'	'
Cash, securities and other assets segregated under federal and other regulations	-266.3	-24.9
Deposits and receivables from exchange-clearing organizations	86.7	-52.4
Deposits and receivables from broker-dealers, clearing organizations, and counterparties	41.6	-43.4
Receivable from customers, net	22.4	-58.1
Notes receivable from customers, net	-27.6	25.2
Income taxes receivable	2.3	-1.5
Financial instruments owned, at fair value	-2.7	-12.6
Physical commodities inventory	-8.9	-20.4
Other assets	-5	3.1
Accounts payable and other accrued liabilities	-16.9	-3.2
Payable to customers	177.1	162.1
Payable to broker-dealers, clearing organizations and counterparties	-12.4	-36.8
Income taxes payable	3	1.4
Financial instruments sold, not yet purchased, at fair value	37.6	62
Net cash provided by (used in) operating activities	44.5	14.1
Cash flows from investing activities:	'	'
Sale of exchange memberships and common stock	0	10.2
Purchase of property and equipment	-3.1	-3.1
Net cash provided by (used in) investing activities	-3.1	7.1
Cash flows from financing activities:	'	'
Net change in payable to lenders under loans and overdrafts	-20.5	7.7
Payments related to earn-outs on acquisitions	-0.3	-0.3
Debt issuance costs	-0.3	-0.2
Exercise of stock options	1.2	0.5
Share repurchase	-7.2	-2.2
Tax shortfall on stock options and awards	0	-0.3
Net cash provided by financing activities	-27.1	5.2
Effect of exchange rates on cash and cash equivalents	-1.2	-0.7
Net increase (decrease) in cash and cash equivalents	13.1	25.7
Cash and cash equivalents at beginning of period	156.1	236.3
Cash and cash equivalents at end of period	169.2	262
Supplemental disclosure of cash flow information:	'	'
Cash paid for interest	5	4.7
Income taxes paid, net of cash refunds	1.6	6
Supplemental disclosure of non-cash investing and financing activities:	'	'
Identified intangible assets and goodwill on acquisitions	0	3.1
Additional consideration payable related to acquisitions	$0.30	$3.90

Condensed_Consolidated_Stateme1

Condensed Consolidated Statement of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
In Millions, unless otherwise specified
Balances as of beginning of period at Sep. 30, 2013	$335.40	$0.20	($7.80)	$224	$125.40	($6.40)
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Net income	10	'	'	'	10	'
Other comprehensive loss	-3.7	'	'	'	'	-3.7
Exercise of stock options	1.2	'	'	1.2	'	'
Share-based Compensation	2.2	'	'	2.2	'	'
Repurchase of stock	-7.2	'	-7.2	'	'	'
Balances as of end of period at Mar. 31, 2014	$337.90	$0.20	($15)	$227.40	$135.40	($10.10)

Basis_of_Presentation_and_Cons

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Notes)	6 Months Ended
	Mar. 31, 2014
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; the sale of 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; 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, 2013, 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, 2013 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.
	Immaterial Correction of an Error in Previously Reported Condensed Consolidated Financial Statements
	The prior period condensed consolidated income statements have been revised to reflect the immaterial correction of certain intercompany physical sales which were not correctly eliminated from the condensed consolidated income statements, resulting in a gross-up of sales of physical commodities and cost of sales of physical commodities. The impact of the correction of this error, before reclassifications for discontinued operations, was a decrease in total revenues of $924.6 million from $13,113.1 million to $12,188.5 million and a decrease in cost of sales of physical commodities of $924.6 million from $12,995.8 million to $12,071.2 million for the three months ended March 31, 2013 and a decrease in total revenues of $1,091.3 million from $25,832.6 million to $24,741.3 million and a decrease in cost of sales of physical commodities of $1,091.3 million from $25,589.6 million to $24,498.3 million for the six months ended March 31, 2013. These immaterial corrections did not impact operating revenues or net income.
	See discussion of total revenues and cost of sales of physical commodities from discontinued operations in Note 18 – Discontinued Operations.
	Reclassifications
	Certain amounts previously reported in the condensed consolidated income statements have been reclassified to conform to the current period presentation. The reclassifications were made to change the income statement presentation to provide the users of the financial statements additional information related to the operating results of the Company. These reclassifications include presenting transaction-based clearing expenses and introducing broker commissions separately from compensation and other expenses, and as components along with interest expense in arriving at net operating revenues. Additionally, travel and business development expenses were previously included in ‘other’ expense. The reclassifications had no effect on consolidated operating revenues or net income.
	For all periods and amounts presented, reclassifications have been made for discontinued operations. See Note 18 – Discontinued Operations.
	During the quarter ended March 31, 2014, the Company reorganized its reportable segments. All segment information has been revised to reflect the business reorganization for all periods and amounts presented. See Note 19 – Segment Analysis.
	Recent Accounting Pronouncements
	On December 16, 2011, the Financial Accounting Standards Board (“FASB”) issued new guidance on the disclosures about offsetting assets and liabilities. The amended guidance limits the scope of balance sheet offsetting to derivatives, repurchase agreements and securities lending transactions to the extent that they are offset in the financial statements or subject to an enforceable master netting arrangement or similar agreement. 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 adopted this guidance starting with the first quarter ended December 31, 2013. The adoption of this guidance did not have a material impact on the Company’s disclosures within the notes to its condensed consolidated financial statements. Refer to Note 4 and Note 10 of the notes to the condensed consolidated financial statements for disclosure of assets and liabilities regarding the Company's derivative instruments and repurchase agreements.
	In February 2013, the FASB issued Accounting Standards Update (“ASU”) No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income requiring new disclosures regarding reclassification adjustments from accumulated other comprehensive income (“AOCI”). ASU No. 2013-02 requires disclosure of amounts reclassified out of AOCI by component. In addition, the entity is required to present, either on the face of the statement where net income is presented or the notes, significant amounts reclassified out of AOCI by the respective line items of net income. The Company adopted this guidance starting with the first quarter ended December 31, 2013. The adoption of this guidance did not have a material impact on the presentation of the Company’s condensed consolidated financial statements.
	In March 2013, the FASB issued ASU No. 2013-05, Parent’s Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity, which addresses the accounting for the cumulative translation adjustment when a parent either sells part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. For public entities, the ASU is effective prospectively for fiscal years, and interim periods, within those years, beginning after December 15, 2013. Early adoption is permitted. The Company expects to adopt this guidance starting with the first quarter of fiscal year 2015. The adoption of this guidance is not expected to have a material impact on the Company’s condensed consolidated financial statements.
	In July 2013, the FASB issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This ASU provides that an unrecognized tax benefit, or a portion thereof, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except to the extent that a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date to settle any additional income taxes that would result from disallowance of a tax position, or the tax law does not require the entity to use, and the entity does not intend to use, the deferred tax asset for such purpose, then the unrecognized tax benefit should be presented as a liability. For public entities, the ASU is effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The Company expects to adopt this guidance starting with the first quarter of fiscal year 2015. The adoption of ASU 2013-11 is not expected to have a material impact on the Company’s condensed consolidated financial statements.
	In April 2014, the FASB issued updated guidance on reporting discontinued operations and disclosures of disposals of components of an entity. Under the amendment only those disposals of components of an entity that represent a strategic shift that has (or will have) a major effect on an entity’s operations and financial results will be reported as discontinued operations in the financial statements. Next, the elimination of the component's operations, cash flows and significant continuing involvement conditions have been removed. Lastly, an equity method investment could be reported as discontinued operations. The updated guidance is effective prospectively for all disposals or classifications as held for sale that occur within annual periods beginning after December 15, 2014. The Company does not expect the adoption of this guidance to have a material impact on the condensed consolidated financial statements.

Earnings_per_Share_Notes

Earnings per Share (Notes)	6 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share [Text Block]	'
	Earnings per Share
	The Company presents basic and diluted earnings per share (“EPS”) using the two-class method which requires all outstanding unvested share-based payment awards that contain rights to non-forfeitable dividends and therefore participate in undistributed earnings with common stockholders be included in computing earnings per share. Under the two-class method, net earnings are reduced by the amount of dividends declared in the period for each class of common stock and participating security. The remaining undistributed earnings are then allocated to common stock and participating securities, based on their respective rights to receive dividends. Restricted stock awards granted to certain employees and directors and shares held in trust for the Provident Group acquisition contain non-forfeitable rights to dividends at the same rate as common stock, and are considered participating securities.
	Basic EPS has been computed by dividing net income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted net income per share computations for the periods presented below.
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions, except share amounts)	2014			2013			2014			2013
	Numerator:
	Income from continuing operations	$	7.7		$	1.7		$	10.1		$	11.8
	Less: Allocation to participating securities	(0.2		)	(0.1		)	(0.3		)	(0.5		)
	Income from continuing operations allocated to common stockholders	$	7.5		$	1.6		$	9.8		$	11.3
	(Loss) income from discontinued operations	$	(0.2	)	$	(0.2	)	$	(0.1	)	$	3
	Less: Allocation to participating securities	—			—			—			(0.1		)
	(Loss) income from discontinued operations allocated to common stockholders	$	(0.2	)	$	(0.2	)	$	(0.1	)	$	2.9
	Diluted net income	$	7.5		$	1.5		$	10		$	14.8
	Less: Allocation to participating securities	(0.2		)	(0.1		)	(0.3		)	(0.6		)
	Diluted net income allocated to common stockholders	$	7.3		$	1.4		$	9.7		$	14.2
	Denominator:
	Weighted average number of:
	Common shares outstanding	18,609,550			18,380,971			18,627,383			18,327,517
	Dilutive potential common shares outstanding:
	Share-based awards	345,578			453,621			646,770			494,282
	Diluted weighted-average shares	18,955,128			18,834,592			19,274,153			18,821,799
	The dilutive effect of share-based awards is reflected in diluted net income per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense required under the Compensation – Stock Compensation Topic of the Accounting Standards Codification (“ASC”).
	Options to purchase 1,332,197 and 1,490,288 shares of common stock for the three months ended March 31, 2014 and 2013, respectively, and options to purchase 1,132,782 and 1,490,288 shares of common stock for the six months ended March 31, 2014 and 2013, respectively, were excluded from the calculation of diluted earnings per share because they would have been anti-dilutive.

Assets_and_Liabilities_at_Fair

Assets and Liabilities, at Fair Value (Notes)	6 Months Ended
	Mar. 31, 2014
Assets and Liabilities, at Fair Value [Abstract]	'
Fair Value Disclosures [Text Block]	'
	Assets and Liabilities, at Fair Value
	The Company’s financial and nonfinancial assets and liabilities reported at fair value are included in the following captions on the condensed consolidated balance sheets:
	•	Cash and cash equivalents
	•	Cash, securities and other assets segregated under federal and other regulations
	•	Deposits and receivables from exchange-clearing organizations, broker-dealers, clearing organizations and counterparties
	•	Financial instruments owned
	•	Accounts payable and other accrued liabilities
	•	Payables to customers
	•	Payables to broker-dealers, clearing organizations and counterparties
	•	Financial instruments sold, not yet purchased
	Fair Value Hierarchy
	The majority of financial assets and liabilities on the consolidated balance sheets are reported at fair value. Cash is reported at the balance held at financial institutions. Cash equivalents includes money market funds, which are valued at period-end at the net asset value provided by the fund’s administrator, and certificates of deposit, which are stated at cost plus accrued interest, which approximates fair value. Cash, securities and other assets segregated under federal and other regulations include the value of cash collateral as well as the value of other pledged investments, primarily U.S. Treasury bills and obligations issued by government sponsored entities and commodities warehouse receipts. Deposits with and receivables from exchange-clearing organizations and broker-dealers, clearing organizations and counterparties and payable to customers and broker-dealers, clearing organizations and counterparties include the value of cash collateral as well as the value of money market funds and other pledged investments, primarily U.S. Treasury bills and obligations issued by government sponsored entities and mortgage-backed securities. These balances also include the fair value of exchange-traded futures and options-on-futures and exchange-cleared swaps and options determined by prices on the applicable exchange. Financial instruments owned and sold, not yet purchased include the value of U.S. and foreign government obligations, corporate debt securities, derivative financial instruments, commodities and mutual funds. The fair value of exchange common stock is determined by quoted market prices, and the fair value of exchange memberships is determined by recent sale transactions. The carrying value of receivables from customers, net and notes receivable, net approximates fair value, given their short duration. Payables to lenders under loans carry variable rates of interest and thus approximate fair value. The fair value of the Company’s senior unsecured notes is estimated to be $48.7 million (carrying value of $45.5 million) as of March 31, 2014, based on the transaction prices at public exchanges for the same or similar issues.
	The fair value estimates presented in the condensed consolidated financial statements are based on pertinent information available to management as of March 31, 2014 and September 30, 2013. Although management is not aware of any factors that would significantly affect the estimated fair value amounts, such amounts have not been comprehensively revalued for purposes of these condensed consolidated financial statements since that date and current estimates of fair value may differ significantly from the amounts presented in the condensed consolidated financial statements.
	Cash equivalents, securities, commodities warehouse receipts, derivative financial instruments, commodities leases, exchange common stock and contingent liabilities are carried at fair value, on a recurring basis, and are classified and disclosed into three levels in the fair value hierarchy. The Company did not have any fair value adjustments for assets or liabilities measured at fair value on a non-recurring basis during the six months ended March 31, 2014. The three levels of the fair value hierarchy under the Fair Value Measurements and Disclosures Topic of the ASC are:
	Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;
	Level 2 - Quoted prices for identical or similar assets or liabilities in markets that are less active, that is, markets in which there are few transactions for the asset or liability that are observable for substantially the full term; and
	Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).
	The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of March 31, 2014 and September 30, 2013 by level in the fair value hierarchy. There were no assets or liabilities that were measured at fair value on a nonrecurring basis as of March 31, 2014 and September 30, 2013.
		March 31, 2014
	(in millions)	Level 1			Level 2			Level 3			Netting and			Total
											Collateral
											-1
	Assets:
	Unrestricted cash equivalents - certificate of deposits	$	3.3		$	—		$	—		$	—		$	3.3
	Commodities warehouse receipts	17.4			—			—			—			17.4
	U.S. government obligations	—			14.5			—			—			14.5
	Securities and other assets segregated under federal and other regulations	17.4			14.5			—			—			31.9
	Money market funds	354.2			—			—			—			354.2
	U.S. government obligations	—			833.8			—			—			833.8
	Mortgage-backed securities	—			3.3			—			—			3.3
	Derivatives	2,277.00			—			—			(2,283.1		)	(6.1		)
	Deposits and receivables from exchange-clearing organizations	2,631.20			837.1			—			(2,283.1		)	1,185.20
	Deposits and receivables from broker-dealers, clearing organizations and counterparties - derivatives	1.8			—			—			(7.0		)	(5.2		)
	Common and preferred stock and American Depositary Receipts (“ADRs”)	63.4			14.8			0.7			—			78.9
	Exchangeable foreign ordinary equities and ADRs	21.1			—			—			—			21.1
	Corporate and municipal bonds	0.2			0.7			3.4			—			4.3
	U.S. government obligations	—			0.3			—			—			0.3
	Foreign government obligations	10			—			—			—			10
	Derivatives	280.2			804.1			—			(1,058.7		)	25.6
	Commodities leases	—			58			—			(51.1		)	6.9
	Commodities warehouse receipts	0.3			—			—			—			0.3
	Exchange firm common stock	4.4			—			—			—			4.4
	Mutual funds and other	3			—			—			—			3
	Mortgage-backed securities	—			1.4			—			—			1.4
	Financial instruments owned	382.6			879.3			4.1			(1,109.8		)	156.2
	Total assets at fair value	$	3,036.30		$	1,730.90		$	4.1		$	(3,399.9	)	$	1,371.40
	Liabilities:
	Accounts payable and other accrued liabilities - contingent liabilities	$	—		$	—		$	9.2		$	—		$	9.2
	Payable to customers - derivatives	2,726.80			—			—			(2,726.8		)	—
	Common and preferred stock and ADRs	61.6			11.4			—			—			73
	Exchangeable foreign ordinary equities and ADRs	19.4			—			—			—			19.4
	Corporate and municipal bonds	0.1			0.7			—			—			0.8
	Derivatives	286.1			806.3			—			(1,027.5		)	64.9
	Commodities leases	—			123.1			—			(63.7		)	59.4
	Financial instruments sold, not yet purchased	367.2			941.5			—			(1,091.2		)	217.5
	Total liabilities at fair value	$	3,094.00		$	941.5		$	9.2		$	(3,818.0	)	$	226.7
	-1	Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.
		September 30, 2013
	(in millions)	Level 1			Level 2			Level 3			Netting and			Total
											Collateral
											-1
	Assets:
	Money market funds	$	0.1		$	—		$	—		$	—		$	0.1
Certificate of deposits	2.9			—			—			—			2.9
Unrestricted cash equivalents	3			—			—			—			3
Money market funds	75			—			—			—			75
Commodities warehouse receipts	13.1			—			—			—			13.1
U.S. government obligations	—			19.5			—			—			19.5
Securities and other assets segregated under federal and other regulations	88.1			19.5			—			—			107.6
Money market funds	841.4			—			—			—			841.4
U.S. government obligations	—			594.8			—			—			594.8
Mortgage-backed securities	—			5.3			—			—			5.3
Derivatives	2,263.20			—			—			(2,333.0		)	(69.8		)
Deposits and receivables from exchange-clearing organizations	3,104.60			600.1			—			(2,333.0		)	1,371.70
Deposits and receivables from broker-dealers, clearing organizations and counterparties - derivatives	1.8			0.2			—			(15.1		)	(13.1		)
Common and preferred stock and American Depositary Receipts (“ADRs”)	49.3			19.8			0.7			—			69.8
Exchangeable foreign ordinary equities and ADRs	36.7			—			—			—			36.7
Corporate and municipal bonds	0.1			—			3.5			—			3.6
U.S. government obligations	—			0.3			—			—			0.3
Foreign government obligations	7.7			—			—			—			7.7
Derivatives	173.6			440.6			—			(592.3		)	21.9
Commodities leases	—			56.1			—			(50.0		)	6.1
Commodities warehouse receipts	4			—			—			—			4
Exchange firm common stock	4.4			—			—			—			4.4
Mutual funds and other	4			—			—			—			4
Financial instruments owned	279.8			516.8			4.2			(642.3		)	158.5
Total assets at fair value	$	3,477.30		$	1,136.60		$	4.2		$	(2,990.4	)	$	1,627.70
Liabilities:
Accounts payable and other accrued liabilities - contingent liabilities	$	—		$	—		$	9.6		$	—		$	9.6
Payable to customers - derivatives	2,328.20			—			—			(2,328.2		)	—
Common and preferred stock and ADRs	82.9			16.6			—			—			99.5
Exchangeable foreign ordinary equities and ADRs	8.7			—			—			—			8.7
Derivatives	174			473.2			—			(616.5		)	30.7
Commodities leases	—			85.5			—			(44.5		)	41
Financial instruments sold, not yet purchased	265.6			575.3			—			(661.0		)	179.9
Total liabilities at fair value	$	2,593.80		$	575.3		$	9.6		$	(2,989.2	)	$	189.5
-1	Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.
Realized and unrealized gains and losses are included in ‘trading gains, net’ in the condensed consolidated income statements.
Information on Level 3 Financial Assets and Liabilities
The Company’s financial assets at fair value classified in level 3 of the fair value hierarchy as of March 31, 2014 and September 30, 2013 are summarized below:
(in millions)	March 31, 2014			September 30, 2013
Total level 3 assets	$	4.1		$	4.2
Level 3 assets for which the Company bears economic exposure	$	4.1		$	4.2
Total assets	$	3,015.10		$	2,848.00
Total financial assets at fair value	$	1,371.40		$	1,627.70
Total level 3 assets as a percentage of total assets	0.1		%	0.1		%
Level 3 assets for which the Company bears economic exposure as a percentage of total assets	0.1		%	0.1		%
Total level 3 assets as a percentage of total financial assets at fair value	0.3		%	0.3		%
The following tables set forth a summary of changes in the fair value of the Company’s level 3 financial assets and liabilities during the three and six months ended March 31, 2014 and 2013, including a summary of unrealized gains (losses) during the respective periods on the Company’s level 3 financial assets and liabilities still held as of March 31, 2014.
	Level 3 Financial Assets and Financial Liabilities
	For the Three Months Ended March 31, 2014
(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
	beginning of			(losses) during			gains (losses)									or (out) of		end of period
	period			period			during period									Level 3
Assets:
Common stock and ADRs	$	0.7		$	—		$	—		$	—		$	—		$	—	$	0.7
Corporate and municipal bonds	3.4			—			—			—			—			—		3.4
	$	4.1		$	—		$	—		$	—		$	—		$	—	$	4.1
Liabilities:
Contingent liabilities	$	9.1		$	—		$	0.1		$	—		$	—		$	—	$	9.2
	Level 3 Financial Assets and Financial Liabilities
	For the Six Months Ended March 31, 2014
(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
	beginning of			(losses) during			gains (losses)									or (out) of		end of period
	period			period			during period									Level 3
Assets:
Common stock and ADRs	$	0.7		$	—		$	—		$	—		$	—		$	—	$	0.7
Corporate and municipal bonds	3.5			—			(0.1		)	—			—			—		3.4
	$	4.2		$	—		$	(0.1	)	$	—		$	—		$	—	$	4.1
Liabilities:
Contingent liabilities	$	9.6		$	—		$	0.3		$	—		$	(0.7	)	$	—	$	9.2
	Level 3 Financial Assets and Financial Liabilities
	For the Three Months Ended March 31, 2013
(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
	beginning of			(losses) during			gains (losses)									or (out) of		end of period
	period			period			during period									Level 3
Assets:
Common stock and ADRs	$	0.9		$	—		$	—		$	—		$	—		$	—	$	0.9
Corporate and municipal bonds	3.6			—			0.2			—			—			—		3.8
	$	4.5		$	—		$	0.2		$	—		$	—		$	—	$	4.7
Liabilities:
Contingent liabilities	$	17.9		$	—		$	0.5		$	—		$	—		$	—	$	18.4
	Level 3 Financial Assets and Financial Liabilities
	For the Six Months Ended March 31, 2013
(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
	beginning of			(losses) during			gains (losses)									or (out) of		end of period
	period			period			during period									Level 3
Assets:
Common stock and ADRs	$	0.9		$	—		$	—		$	—		$	—		$	—	$	0.9
Corporate and municipal bonds	3.6			—			0.2			—			—			—		3.8
	$	4.5		$	—		$	0.2		$	—		$	—		$	—	$	4.7
Liabilities:
Contingent liabilities	$	14.8		$	—		$	0.8		$	3.1		$	(0.3	)	$	—	$	18.4
In accordance with the Fair Value Measurements Topic of the ASC, the Company has estimated on a recurring basis each period the fair value of debentures issued by a single asset owning company of Suriwongse Hotel located in Chiang Mai, Thailand. As of March 31, 2014, the Company’s investment in the hotel is $3.4 million, and included within the corporate and municipal bonds classification in the level 3 financial assets and financial liabilities tables. The Company has classified its investment in the hotel within level 3 of the fair value hierarchy because the fair value is determined using significant unobservable inputs, which include projected cash flows. These cash flows are discounted employing present value techniques. The Company estimates the fair value of its investment in these debentures by using a management-developed forecast, which is based on the income approach. The Company continues to monitor the hotel renovation process and evaluate the fair value of the debentures. There has been no significant change in the fair value of the debentures, and no additional loss has been recognized during the three and six months ended March 31, 2014 and 2013.
The Company is required to make additional future cash payments based on certain financial performance measures of its acquired businesses. The Company is required to remeasure the fair value of the cash earnout arrangements on a recurring basis in accordance with the guidance in the Business Combinations Topic of the ASC. The Company has classified its liabilities for the contingent earnout arrangements within level 3 of the fair value hierarchy because the fair value is determined using significant unobservable inputs, which include projected cash flows. The estimated fair value of the contingent purchase consideration is based upon management-developed forecasts, a level 3 input in the fair value hierarchy. These cash flows are discounted employing present value techniques in arriving at fair value. The discount rate was developed using market participant company data and there have been no significant changes in the discount rate environment. From the dates of acquisition to March 31, 2014, certain acquisitions have had changes in the estimates of undiscounted cash flows, based on actual performances fluctuating from estimates. The fair value of the contingent consideration increased $0.1 million and $0.5 million during the three months ended March 31, 2014 and 2013, respectively, and $0.3 million and $0.8 million during the six months ended March 31, 2014 and 2013, respectively, with the corresponding amount classified as ‘other expense’ in the condensed consolidated income statements.
The Company reports transfers in and out of levels 1, 2 and 3, as applicable, using the fair value of the securities as of the beginning of the reporting period in which the transfer occurred. The Company did not have any transfers between level 1 and level 2 fair value measurements during the three and six months ended March 31, 2014.
The Company has also classified equity investments in exchange firms’ common stock not pledged for clearing purposes as available-for-sale. The investments are recorded at fair value, with unrealized gains and losses recorded, net of taxes, as a component of other comprehensive income (“OCI”) until realized. As of March 31, 2014, the cost and fair value of all the equity investments in exchange firms was $3.7 million and $4.4 million, respectively. As of September 30, 2013, the cost and fair value of the equity investments in exchange firms was $3.7 million and $4.4 million, respectively.
In June 2012, the board of LME Holdings Limited (“LME Holdings”), the parent company of The London Metal Exchange (“LME”), entered into a framework agreement regarding the terms of a recommended cash offer for the entire issued and outstanding ordinary share capital of LME Holdings. In July 2012, the shareholders of LME Holdings approved the sale of LME Holdings to the Hong Kong Exchanges & Clearing Limited. In December 2012, the Company received proceeds of $8.6 million from the sale of its shares in the LME. The shares of the LME were previously held by the Company as available-for-sale and the unrealized gain for those shares was reflected in OCI. For the six months ended March 31, 2013, the Company reclassified the unrealized gain remaining in AOCI of approximately $6.3 million, net of income tax expense of $2.0 million, into earnings.
In December 2012, the Company sold its exchange membership seats in the Board of Trade of Kansas City, Missouri, Inc. (“KCBT”), in connection with the acquisition of the KCBT by Chicago Mercantile Exchange (“CME”). The Company was required to hold these exchange membership seats for clearing purposes and, as a result, the associated KCBT shares were being held at cost on the condensed consolidated balance sheet. The Company received proceeds of $1.5 million and recognized a gain of $0.9 million before taxes, during the six months ended March 31, 2013, in connection with the sale of these seats.
The Company recorded unrealized gains of $0.5 million, net of income tax expense of $0.3 million as of March 31, 2014, and unrealized gains of $0.5 million, net of income tax expense of $0.3 million as of September 30, 2013, in OCI related to U.S. government obligations, mortgage-backed securities and the remaining equity investments in exchange firms classified as available-for-sale securities.
The following tables summarize the amortized cost basis, the aggregate fair value and gross unrealized holding gains and losses of the Company’s investment securities classified as available-for-sale as of March 31, 2014 and September 30, 2013:
March 31, 2014
Amounts included in deposits with and receivables from exchange-clearing organizations and financial instruments owned:
	Amortized			Unrealized Holding						Estimated
(in millions)	Cost			Gains			(Losses)			Fair Value
U.S. government obligations	$	806.5		$	0.1		$	—		$	806.6
Mortgage-backed securities	4.6			0.1			—			4.7
	$	811.1		$	0.2		$	—		$	811.3
September 30, 2013
Amounts included in deposits with and receivables from exchange-clearing organizations:
	Amortized			Unrealized Holding(1)						Estimated
(in millions)	Cost			Gains			(Losses)			Fair Value
U.S. government obligations	$	568.5		$	—		$	—		$	568.5
Mortgage-backed securities	5.2			0.1			—			5.3
	$	573.7		$	0.1		$	—		$	573.8
(1) Unrealized gain/loss on U.S. government obligations as of September 30, 2013, was less than $0.1 million.
As of March 31, 2014 and September 30, 2013, investments in debt securities classified as available-for-sale (“AFS”) mature as follows:
March 31, 2014
	Due in						Estimated
(in millions)	Less than 1 year			1 year or more			Fair Value
U.S. government obligations	$	806.6		$	—		$	806.6
Mortgage-backed securities	—			4.7			4.7
	$	806.6		$	4.7		$	811.3
September 30, 2013
	Due in						Estimated
(in millions)	Less than 1 year			1 year or more			Fair Value
U.S. government obligations	$	568.5		$	—		$	568.5
Mortgage-backed securities	—			5.3			5.3
	$	568.5		$	5.3		$	573.8
Except as discussed previously, there were no other sales of AFS securities during the three months ended March 31, 2014 and 2013, and as a result, no realized gains or losses were recorded for the three months ended March 31, 2014 and 2013.
For the purposes of the maturity schedule, mortgage-backed securities, which are not due at a single maturity date, have been allocated over maturity groupings based on the expected maturity of the underlying collateral. Mortgage-backed securities may mature earlier than their stated contractual maturities because of accelerated principal repayments of the underlying loans.

Financial_Instruments_with_Off

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Notes)	6 Months Ended
	Mar. 31, 2014
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]	'
Derivative Instruments and Hedging Activities Disclosure [Text Block]	'
	Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk
	The Company is party to certain financial instruments with off-balance sheet risk in the normal course of its business. The Company has sold financial instruments that it does not currently own and will therefore be obliged to purchase such financial instruments at a future date. The Company has recorded these obligations in the condensed consolidated financial statements as of March 31, 2014 at the fair values of the related financial instruments. The Company will incur losses if the fair value of the underlying financial instruments increases subsequent to March 31, 2014. The total of $217.5 million as of March 31, 2014 includes $64.9 million for derivative contracts, which represents a liability to the Company based on their fair values as of March 31, 2014.
	Derivatives
	The Company utilizes derivative products in its trading capacity as a dealer in order to satisfy client needs and mitigate risk. The Company manages risks from both derivatives and non-derivative cash instruments on a consolidated basis. The risks of derivatives should not be viewed in isolation, but in aggregate with the Company’s other trading activities. The majority of the Company’s derivative positions are included in the consolidated balance sheets in ‘financial instruments owned, at fair value’, ‘deposits and receivables from exchange-clearing organizations’ and ‘financial instruments sold, not yet purchased, at fair value’.
	The Company employs an interest rate risk management strategy that uses derivative financial instruments in the form of interest rate swaps to manage a portion of the aggregate interest rate position. The Company’s objective is to invest the majority of customer segregated deposits in high quality, short-term investments and swap the resulting variable interest earnings into the medium-term interest stream, by using a strip of interest rate swaps that mature every quarter, in order to achieve the two year moving average of the two year swap rate. The risk mitigation of these interest rate swaps is not within the documented hedging designation requirements of the Derivatives and Hedging Topic of the ASC, and as a result they are recorded at fair value, with changes in the marked-to-market valuation of the financial instruments recorded in ‘trading gains, net’ in the consolidated income statements. The Company did not have any interest rate swaps outstanding at March 31, 2014.
	Listed below are the fair values of the Company’s derivative assets and liabilities as of March 31, 2014 and September 30, 2013. Assets represent net unrealized gains and liabilities represent net unrealized losses.
		March 31, 2014						September 30, 2013
	(in millions)	Assets (1)			Liabilities (1)			Assets (1)			Liabilities (1)
	Derivative contracts not accounted for as hedges:
	Exchange-traded commodity derivatives	$	2,121.60		$	2,535.80		$	2,036.60		$	2,046.30
	OTC commodity derivatives	844.8			849			481.4			484.9
	Exchange-traded foreign exchange derivatives	74.7			70.3			89.3			104.2
	OTC foreign exchange derivatives	238.6			243.4			132.3			162.3
	Exchange-traded interest rate derivatives	8.1			6.8			4.3			36
	Equity index derivatives	75.3			113.9			135.5			141.7
	Gross fair value of derivative contracts	3,363.10			3,819.20			2,879.40			2,975.40
	Impact of netting and collateral	(3,348.8		)	(3,754.3		)	(2,940.4		)	(2,944.7		)
	Total fair value included in ‘Deposits and receivables from exchange-clearing organizations’	$	(6.1	)				$	(69.8	)
	Total fair value included in ‘Deposits and receivables from broker-dealers, clearing organizations and counterparties’	$	(5.2	)				$	(13.1	)
	Total fair value included in ‘Financial instruments owned, at fair value’	$	25.6					$	21.9
	Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’				$	64.9					$	30.7
	-1	As of March 31, 2014 and September 30, 2013, the Company’s derivative contract volume for open positions were approximately 4.2 million and 4.1 million contracts, respectively.
	The Company’s derivative contracts are principally held in its Commercial Hedging segment. The Company assists its Commercial Hedging segment customers in protecting the value of their future production by entering into option or forward agreements with them on an OTC basis. The Company also provides its Commercial Hedging segment customers with sophisticated option products, including combinations of buying and selling puts and calls. The Company mitigates its risk by offsetting the customer’s transaction simultaneously with one of the Company’s trading counterparties or with a similar but not identical position on the exchange. The risk mitigation of these offsetting trades is not within the documented hedging designation requirements of the Derivatives and Hedging Topic of the ASC. These derivative contracts are traded along with cash transactions because of the integrated nature of the markets for these products. The Company manages the risks associated with derivatives on an aggregate basis along with the risks associated with its proprietary trading and market-making activities in cash instruments as part of its firm-wide risk management policies. In particular, the risks related to derivative positions may be partially offset by inventory, unrealized gains in inventory or cash collateral paid or received.
	The following table sets forth the Company’s gains (losses) related to derivative financial instruments for the three and six months ended March 31, 2014 and 2013, in accordance with the Derivatives and Hedging Topic of the ASC. The gains (losses) set forth below are included in ‘trading gains, net’ and ‘income (loss) from discontinued operations, net of tax’ in the condensed consolidated income statements.
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions)	2014			2013			2014			2013
	Commodities	$	21.9		$	10.8		$	30.6		$	41.4
	Foreign exchange	2.7			3.1			4.8			5.7
	Interest rate	—			—			—			0.1
	Net gains (losses) from derivative contracts	$	24.6		$	13.9		$	35.4		$	47.2
	Credit Risk
	In the normal course of business, the Company purchases and sells financial instruments, commodities and foreign currencies as either principal or agent on behalf of its customers. If either the customer or counterparty fails to perform, the Company may be required to discharge the obligations of the nonperforming party. In such circumstances, the Company may sustain a loss if the fair value of the financial instrument or foreign currency is different from the contract value of the transaction.
	The majority of the Company’s transactions and, consequently, the concentration of its credit exposure are with commodity exchanges, customers, broker-dealers and other financial institutions. These activities primarily involve collateralized and uncollateralized arrangements and may result in credit exposure in the event that a counterparty fails to meet its contractual obligations. The Company’s exposure to credit risk can be directly impacted by volatile financial markets, which may impair the ability of counterparties to satisfy their contractual obligations. The Company seeks to control its credit risk through a variety of reporting and control procedures, including establishing credit limits based upon a review of the counterparties’ financial condition and credit ratings. The Company monitors collateral levels on a daily basis for compliance with regulatory and internal guidelines and requests changes in collateral levels as appropriate.
	The Company is a party to financial instruments in the normal course of its business through customer and proprietary trading accounts in exchange-traded and OTC derivative instruments. These instruments are primarily the execution of orders for commodity futures, options on futures and forward foreign currency contracts on behalf of its customers, substantially all of which are transacted on a margin basis. Such transactions may expose the Company to significant credit risk in the event margin requirements are not sufficient to fully cover losses which customers may incur. The Company controls the risks associated with these transactions by requiring customers to maintain margin deposits in compliance with individual exchange regulations and internal guidelines. The Company monitors required margin levels daily and, therefore, may require customers to deposit additional collateral or reduce positions when necessary. The Company also establishes credit limits for customers, which are monitored daily. The Company evaluates each customer’s creditworthiness on a case by case basis. Clearing, financing, and settlement activities may require the Company to maintain funds with or pledge securities as collateral with other financial institutions. Generally, these exposures to both customers and exchanges are subject to master netting, or customer agreements, which reduce the exposure to the Company by permitting receivables and payables with such customers to be offset in the event of a customer default. Management believes that the margin deposits held as of March 31, 2014 and September 30, 2013 were adequate to minimize the risk of material loss that could be created by positions held at that time. Additionally, the Company monitors collateral fair value on a daily basis and adjusts collateral levels in the event of excess market exposure. Generally, these exposures to both customers and counterparties are subject to master netting or customer agreements which reduce the exposure to the Company.
	Derivative financial instruments involve varying degrees of off-balance sheet market risk whereby changes in the fair values of underlying financial instruments may result in changes in the fair value of the financial instruments in excess of the amounts reflected in the condensed consolidated balance sheets. Exposure to market risk is influenced by a number of factors, including the relationships between the financial instruments and the Company’s positions, as well as the volatility and liquidity in the markets in which the financial instruments are traded. The principal risk components of financial instruments include, among other things, interest rate volatility, the duration of the underlying instruments and changes in foreign exchange rates. The Company attempts to manage its exposure to market risk through various techniques. Aggregate market limits have been established and market risk measures are routinely monitored against these limits.

Receivables_From_Customers_Net

Receivables From Customers, Net and Notes Receivable, Net (Notes)	6 Months Ended
	Mar. 31, 2014
Receivables from customers and notes receivable, net [Abstract]	'
Financing Receivables [Text Block]	'
	Receivables From Customers, Net and Notes Receivable, Net
	Receivables from customers, net and notes receivable, net include an allowance for bad debts, which reflects the Company’s best estimate of probable losses inherent in the receivables from customers and notes receivable. The Company provides for an allowance for doubtful accounts based on a specific-identification basis. The Company continually reviews its allowance for bad debts. The allowance for doubtful accounts related to receivables from customers was $1.6 million and $1.1 million as of March 31, 2014 and September 30, 2013, respectively. The allowance for doubtful accounts related to notes receivable was $0.1 million as of March 31, 2014 and September 30, 2013.
	During the three months ended March 31, 2014, the Company recorded bad debt expense of $0.4 million, including provision increases of $0.1 million and direct write-offs of $0.3 million. During the three months ended March 31, 2013, the Company recorded recovery of bad debt expense of $0.1 million, representing provision decreases. During the six months ended March 31, 2014, the Company recorded bad debt expense of $0.7 million, including provision increases of $0.4 million and direct write-offs of $0.3 million. During the six months ended March 31, 2013, the Company recorded bad debt expense of $0.1 million, representing provision decreases.
	The Company originates short-term notes receivable from customers with the outstanding balances being insured 90% to 98% by a third party, including accrued interest. The total balance outstanding under insured notes receivable was $33.5 million and $21.1 million as of March 31, 2014 and September 30, 2013, respectively. The Company has sold $30.6 million and $18.7 million of the insured portion of the notes through non-recourse participation agreements with other third parties as of March 31, 2014 and September 30, 2013, respectively.
	See discussion of notes receivable related to commodity repurchase agreements in Note 10.

Physical_Commodities_Inventory

Physical Commodities Inventory (Notes)	6 Months Ended
	Mar. 31, 2014
Physical Commodities Inventory [Abstract]	'
Inventory Disclosure [Text Block]	'
	Physical Commodities Inventory
	Physical commodities inventories are stated at the lower of cost or market (“LCM”) using the weighted-average price and first-in first-out cost method. Cost includes finished commodity or raw material and processing costs related to the purchase and processing of inventories. Commodities in process include commodities in the process of being recycled. The carrying values of the Company’s inventory as of March 31, 2014 and September 30, 2013 are shown below.
	(in millions)	March 31,		September 30, 2013
		2014
	Commodities in process	$	0.3	$	—
	Finished commodities	67.6		59
	Physical commodities inventory - finished commodities	$	67.9	$	59
	As a result of declining market prices for some commodities, the Company has recorded LCM adjustments for physical commodities inventory of $0.3 million and $0.9 million as of March 31, 2014 and September 30, 2013, respectively. The adjustments are included in ‘cost of sales of physical commodities’ in the condensed consolidated income statements.

Goodwill_Notes

Goodwill (Notes)	6 Months Ended
	Mar. 31, 2014
Goodwill [Abstract]	'
Goodwill Disclosure [Text Block]	'
	Goodwill
	The carrying value of goodwill by segment is as follows:
	(in millions)	March 31,		September 30,
		2014		2013
	Commercial Hedging	$	33.1	$	33.1
	Global Payments	6.3		6.3
	Securities	8.1		8.1
	Goodwill	$	47.5	$	47.5

Intangible_Assets_Notes

Intangible Assets - (Notes)	6 Months Ended
	Mar. 31, 2014
Intangible Assets [Abstract]	'
Intangible Assets Disclosure [Text Block]	'
	Intangible Assets
	The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows:
		March 31, 2014							September 30, 2013
	(in millions)	Gross Amount		Accumulated			Net Amount		Gross Amount		Accumulated			Net Amount
				Amortization							Amortization
	Intangible assets subject to amortization
	Noncompete agreement	$	—	$	—		$	—	$	3.7	$	(3.7	)	$	—
	Trade name	—		—			—		0.7		(0.7		)	—
	Software programs/platforms	2.2		(1.7		)	0.5		2.2		(1.5		)	0.7
	Customer base	12.4		(3.0		)	9.4		12.4		(2.6		)	9.8
		14.6		(4.7		)	9.9		19		(8.5		)	10.5
	Intangible assets not subject to amortization
	Trade name	1.1		—			1.1		1.1		—			1.1
	Total intangible assets	$	15.7	$	(4.7	)	$	11	$	20.1	$	(8.5	)	$	11.6
	Amortization expense related to intangible assets was $0.6 million and $1.1 million for the six months ended March 31, 2014 and 2013, respectively.
	As of March 31, 2014, the estimated future amortization expense was as follows:
	(in millions)
	Fiscal 2014 (remaining six months)	$	0.7
	Fiscal 2015	1.1
	Fiscal 2016	0.7
	Fiscal 2017	0.7
	Fiscal 2018	0.7
	Fiscal 2019 and thereafter	6
		$	9.9

Credit_Facilities_Notes

Credit Facilities (Notes)	6 Months Ended
	Mar. 31, 2014
Credit Facilities [Abstract]	'
Debt Disclosure [Text Block]	'
	Credit Facilities
	Variable-Rate Credit Facilities
	The Company has four committed credit facilities under which the Company and its subsidiaries may borrow up to $270.0 million, subject to the terms and conditions for these facilities. The amounts outstanding under these credit facilities are short term borrowings and carry variable rates of interest, thus approximating fair value.
	The Company’s credit facilities consist of the following:
	•	$140.0 million facility available to INTL FCStone Inc. for general working capital requirements, committed until September 20, 2016. The facility is secured by a pledge of shares held in certain of the Company’s subsidiaries.
	•	$75.0 million facility available to the Company’s wholly owned subsidiary, FCStone, LLC, for short-term funding of margin to commodity exchanges, committed until April 9, 2015. The facility is subject to annual review and guaranteed by INTL FCStone Inc.
	•	$30.0 million facility available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC, for financing traditional commodity financing arrangements and commodity repurchase agreements, committed until May 1, 2015. The facility is subject to annual review, and is secured by the assets of FCStone Merchants and guaranteed by INTL FCStone Inc.
	•	$25.0 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Ltd, for short-term funding of margin to commodity exchanges, committed until November 10, 2014. The facility is subject to annual review, and the facility is guaranteed by INTL FCStone Inc.
	Senior Unsecured Notes
	In July 2013, the Company completed the offering of $45.5 million aggregate principal amount of the Company’s 8.5% Senior Notes due 2020 (the “Notes”). The net proceeds of the sale of the Notes are being used for general corporate purposes. The Notes were issued under an Indenture dated as of July 22, 2013, between the Company and The Bank of New York Mellon, as Trustee. The Notes bear interest at a rate of 8.5% per year (payable quarterly on January 30, April 30, July 30 and October 30 of each year). The Notes mature on July 30, 2020. The Company may redeem the Notes, in whole or in part, at any time on and after July 30, 2016, at a redemption price equal to 100% of the principal amount redeemed plus accrued and unpaid interest to, but not including, the redemption date. The Company incurred debt issuance costs of $1.7 million in connection with the issuance of the Notes, which are being amortized over the term of the Notes.
	The following table sets forth a listing of credit facilities, the committed amounts as of March 31, 2014 on the facilities, and outstanding borrowings on the facilities as well as indebtedness on senior notes as of March 31, 2014 and September 30, 2013:
	(in millions)
	Credit Facilities						Amounts Outstanding
		Borrower	Security	Renewal / Expiration Date	Total Commitment		March 31,		September 30,
							2014		2013
		INTL FCStone Inc.	Certain pledged shares	September 20, 2016	$	140	$	24	$	55
		FCStone, LLC	None	April 9, 2015	75		—		—
		FCStone Merchants	Certain commodities assets	May 1, 2015	30		16.5		6
		INTL FCStone, Ltd.	None	November 10, 2014	25		—		—
					$	270	$	40.5	$	61
	Senior Unsecured Notes
		8.50% senior notes, due July 30, 2020					45.5		45.5
	Total indebtedness						$	86	$	106.5
	As shown above, $25 million of the Company’s committed credit facilities are scheduled to expire during the next twelve months. The Company intends to renew or replace these facilities as they expire, and based on the Company’s liquidity position and capital structure, the Company believes it will be able to do so.
	The Company’s credit facility agreements contain financial covenants relating to financial measures on a consolidated basis, as well as on a certain stand-alone subsidiary basis, including minimum tangible net worth, minimum regulatory capital, minimum net unencumbered liquid assets, maximum net loss, minimum fixed charge coverage ratio and maximum funded debt to net worth ratio. Failure to comply with these covenants could result in the debt becoming payable on demand. As of March 31, 2014, the Company was in compliance with all of its financial covenants under its credit facilities.

Commodity_and_Other_Repurchase

Commodity and Other Repurchase Agreements (Notes)	6 Months Ended
	Mar. 31, 2014
Commodity and Other Repurchase Agreements [Abstract]	'
Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block]	'
	Commodity and Other Repurchase Agreements
	The Company’s outstanding notes receivable in connection with sale/repurchase agreements, under which customers sell certain commodity inventory and agree to repurchase the commodity inventory at a future date at either a fixed or floating rate, as of March 31, 2014 and September 30, 2013 were $24.7 million and $9.2 million, respectively.
	The obligations outstanding related to commodities sold under repurchase agreements that are recorded in ‘lenders under loans’ as of March 31, 2014 and September 30, 2013 were $16.5 million and $6.0 million, respectively.

Commitments_and_Contingencies_

Commitments and Contingencies (Notes)	6 Months Ended
	Mar. 31, 2014
Commitments and Contingencies [Abstract]	'
Commitments and Contingencies Disclosure [Text Block]	'
	Commitments and Contingencies
	Legal and Regulatory Proceedings
	Certain conditions may exist as of the date that the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. In assessing loss contingencies related to legal and regulatory proceedings that are pending against the Company or unasserted claims that may result in such proceedings, the Company’s legal counsel evaluates the perceived merits of any legal proceedings or unasserted claims as well as the perceived merits of the amount of relief sought or expected to be sought therein.
	If the assessment of a contingency indicates that it is probable that a material loss had been incurred at the date of the financial statements and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potentially material loss contingency is not probable, but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, together with an estimate of the range of possible loss if determinable and material, would be disclosed. Neither accrual nor disclosure is required for loss contingencies that are deemed remote. The Company accrues legal fees related to contingent liabilities as they are incurred.
	In addition to the matters discussed below, 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, 2014 and September 30, 2013, the condensed consolidated balance sheets include loss contingency accruals recorded prior to September 30, 2013 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, and in addition to the possible losses discussed below, is not likely to be material to the Company’s earnings, financial position or liquidity.
	The following is a summary of significant legal matters involving the Company.
	Securities Litigation and Regulatory Proceedings
	In August 2008, shareholders filed a derivative action against FCStone and certain directors of FCStone in the Circuit Court of Platte County, Missouri, alleging breaches of fiduciary duties, waste of corporate assets and unjust enrichment. Shareholders subsequently filed an amended complaint in May 2009 to add claims based upon the losses sustained by FCStone arising out of a customer energy trading account. In July 2009, the same plaintiff filed a motion for leave to amend the existing case to add a purported class action claim on behalf of the holders of FCStone common stock.
	In July 2009, plaintiffs filed a purported shareholder class action complaint against FCStone and its directors, as well as the Company in the Circuit Court of Clay County, Missouri. The complaint alleged that FCStone and its directors breached their fiduciary duties by failing to maximize stockholder value in connection with the contemplated acquisition of FCStone by the Company. This complaint was subsequently consolidated with the complaint filed in the Circuit Court of Platte County, Missouri. The plaintiffs subsequently filed an amended consolidated complaint which does not assert any claims against the Company. This complaint purports to be filed derivatively on FCStone’s and the Company’s behalf and against certain of FCStone’s current and former directors and officers and directly against the same individuals. The Company, FCStone, and the defendants filed motions to dismiss on multiple grounds. The parties to the litigation have reached an agreement in principle to settle this matter, the terms of which were finally approved on March 19, 2014, resulting in the Company’s incurring a legal cost of $265,000 after consideration of expected insurance coverage.
	In November 2011, the Commodity Futures Trading Commission (“CFTC”) Division of Enforcement Staff (“Staff”) requested the Company to voluntarily produce specified documents to the Staff in connection with its then informal investigation of the losses that occurred in 2008 and 2009 in the customer energy trading account of FCStone, LLC. In September 2012, the Staff provided the Company with a Wells notice, indicating the Staff’s intention to recommend that the CFTC bring certain charges against FCStone, LLC. The Company filed its Wells submission with the Staff in October 2012. On May 29, 2013, the Company reached a settlement with the CFTC in this matter. The CFTC’s findings, neither admitted nor denied by the Company, were that FCStone, LLC violated CFTC Regulation 166.3 in that it failed to diligently supervise its officers’ and employees’ activities relating to risks associated with its customers’ accounts, and in particular one account controlled by two of FCStone’s customers who traded in natural gas futures, swaps and option contracts.
	The settlement, with appropriate waivers and consents, required FCStone, LLC to appoint an independent third party reviewer to review and evaluate FCStone LLC’s existing policies and procedures relating to certain risks, to ensure that we have made sufficient modifications to its risk controls since 2008. An independent third party reviewer was appointed, and the review has been successfully completed.
	On January 13, 2014, a purported class action was filed in the United States District Court for the Southern District of New York against the Company and certain of its officers and directors. The complaint alleges violations of federal securities laws, and claims that the Company has issued false and misleading information concerning the Company’s business and prospects. The action seeks unspecified damages on behalf of persons who purchased the Company’s shares between February 17, 2010 and December 16, 2013. During March 2014, three motions for appointment as lead plaintiff were filed; two were subsequently withdrawn, leaving a single unopposed bid for lead plaintiff appointment, an appointment that was approved by the court on April 29, 2014. The Company believes the case is without merit and intends to vigorously defend itself.
	Sentinel Litigation
	The Company’s subsidiary, FCStone, LLC, had a portion of its excess segregated funds invested with Sentinel Management Group Inc. (“Sentinel”), a registered 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 and $15.5 million of FCStone, LLC’s $21.9 million in invested funds were returned to it.
	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 sought 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 sought recovery of pre- and post-petition transfers totaling approximately $15.5 million. In April 2009, the trustee filed an amended complaint adding a claim for unjust enrichment. FCStone, LLC answered the complaints and all parties entered into the discovery phase of the litigation. In January 2011, the trustee filed a motion for summary judgment on various counts in the adversary proceedings filed in August 2008 against FCStone, LLC and a number of other FCMs. In January 2012, FCStone, LLC filed a motion for summary judgment in its favor with respect to the transfer of approximately $1.1 million to its customer segregated account on August 17, 2007, pursuant to the “safe harbor” provisions of Section 546(e) of the U.S. Bankruptcy Code. In April 2012, FCStone, LLC filed a motion to dismiss a portion of the trustee’s claims set forth in its amended complaint. 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. By agreement, FCStone, LLC was required to post an appeal cash deposit of $8.0 million with the court, which was deposited on January 18, 2013. The oral arguments in the appeal were heard on December 10, 2013. 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. The Company believes that if the appellate decision in favor of FCStone, LLC is reversed, the resulting pre-tax loss to FCStone, LLC would be in the range of $4 million to $6 million.
	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 $9.2 million and $9.6 million are included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheets as of March 31, 2014 and September 30, 2013. 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, 2014 and 2013 were increases of $0.3 million and $0.8 million, respectively, and are included in ‘other’ in the 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 contingent liability recorded represents the fair value of the expected consideration to be paid, based on the forecasted adjusted pre-tax net earnings during three annual periods and a six month period, after the third annual period, following the closing of the acquisition, for a total of four payments, with a discount rate being applied to those future payments. The change in fair value during the six months ended March 31, 2014 was an increase of $0.2 million, included in ‘other’ in the consolidated income statement. The present value of the estimated total purchase price, including contingent consideration, is $6.5 million as of March 31, 2014, which remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the consolidated balance sheet.
	The Company has a contingent liability relating to the November 2011 acquisition of Coffee Network, LLC, subsequently reorganized as a division of FCStone, LLC, which may result in the payment of additional purchase price consideration. The contingent liability recorded represents the fair value of the expected consideration to be paid, based on the forecasted adjusted pre-tax net earnings during the three annual periods following the closing of the acquisition plus a final contingent payment. The acquisition date fair value of additional consideration was estimated to be less than $0.1 million. There was no significant change in fair value for the six months ended March 31, 2014 and 2013. The present value of the estimated total purchase price, including contingent consideration, is less than $0.1 million as of March 31, 2014, which has not been paid and is included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.
	The Company has a contingent liability relating to the October 2010 acquisition of Hencorp Becstone Futures, L.C., subsequently reorganized as a division of FCStone, LLC, which may result in the payment of additional purchase price consideration. The contingent liability recorded represents the fair value of the expected consideration to be paid, based on the forecasted adjusted pre-tax net earnings during the fourth fiscal year following the closing of the acquisition plus an additional final estimated contingent payment and a discount rate being applied to the future payments. The change in fair value during the six months ended March 31, 2014 and 2013, were increases of $0.1 million and $0.2 million, respectively, and are included in ‘other’ in the condensed consolidated income statements. The present value of the estimated total purchase price, including contingent consideration, is $7.6 million as of March 31, 2014, of which $2.6 million has not been paid and is included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.
	Exchange Member Guarantees
	The Company is a member of various exchanges that trade and clear futures and option contracts. Associated with its memberships, the Company may be required to pay a proportionate share of the financial obligations of another member who may default on its obligations to the exchanges. While the rules governing different exchange memberships vary, in general the Company’s guarantee obligations would arise only if the exchange had previously exhausted its resources. In addition, any such guarantee obligation would be apportioned among the other non-defaulting members of the exchange. Any potential contingent liability under these membership agreements cannot be estimated. The Company has not recorded any contingent liability in the condensed consolidated financial statements for these agreements and believes that any potential requirement to make payments under these agreements is remote.
	Self-Insurance
	On January 1, 2014, the Company entered into a program to self-insure 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. Liabilities are recognized based on claims filed and an estimate of claims incurred but not reported. The Company has purchased stop-loss coverage to limit its exposure on a per claim basis and in aggregate in the event that aggregated actual claims would exceed 120% of actuarially estimated claims. The Company is insured for covered costs in excess of these limits. Although the ultimate outcome of these matters may exceed the amounts recorded and additional losses may be incurred, the Company does not believe that any additional potential exposure for such liabilities will have a material adverse effect on the Company’s condensed consolidated financial position or results of operations. As of March 31, 2014, the Company had $0.5 million accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.

Capital_and_Other_Regulatory_R

Capital and Other Regulatory Requirements (Notes)	6 Months Ended
	Mar. 31, 2014
Capital and Other Regulatory Requirements [Abstract]	'
Regulatory Capital Requirements under Banking Regulations [Text Block]	'
	Capital and Other Regulatory Requirements
	The Company’s activities are subject to significant governmental regulation, both in the United States and overseas. The subsidiaries of the Company were in compliance with all of their regulatory requirements as of March 31, 2014, as follows:
	(in millions)			As of March 31, 2014
	Subsidiary	Regulatory Authority	Requirement Type	Actual		Minimum
						Requirement
	FCStone, LLC	CFTC	Net capital	$	125.6	$	86.5
	FCStone, LLC	CFTC	Segregated funds	$	1,864.80	$	1,838.20
	FCStone, LLC	CFTC	Secured funds	$	64.9	$	48.1
	INTL FCStone Ltd	FCA (United Kingdom)	Net capital	$	59.6	$	46.3
	INTL FCStone Ltd	FCA (United Kingdom)	Segregated funds	$	112.7	$	112.6
	INTL Global Currencies Limited	FCA (United Kingdom)	Net capital	$	20.5	$	0.9
	INTL FCStone Securities Inc.	SEC	Net capital	$	5	$	1
	FCC Investments, Inc.	SEC	Net capital	$	0.3	$	0.3
	FCStone Australia	Australian Securities and Investment Commission	Net capital	$	1.7	$	0.9
	FCStone Australia	Australian Securities and Investment Commission	Segregated funds	$	22.4	$	14.9
	FCStone Australia	New Zealand Clearing Ltd	Capital adequacy	$	11.6	$	4.3
	INTL FCStone DTVM Ltda.	Brazilian Central Bank and Securities and Exchange Commission of Brazil	Capital adequacy	$	0.9	$	0.6
	INTL Capital S.A.	Rosario Futures Exchange (Argentina)	Capital adequacy	$	3.9	$	0.1
	INTL Capital S.A.	General Inspector of Justice (Argentina)	Net capital	$	6.1	$	5.9
	INTL CIBSA Sociedad de Bolsa S.A.	Superintendent of Securities Markets of Buenos Aires (Argentina)	Net capital	$	4.6	$	0.2
	Certain other non-U.S. subsidiaries of the Company are also subject to capital adequacy requirements promulgated by authorities of the countries in which they operate. As of March 31, 2014, these subsidiaries were in compliance with their local capital adequacy requirements.

StockBased_Compensation_Notes

Stock-Based Compensation (Notes)	6 Months Ended
	Mar. 31, 2014
Stock-Based Compensation [Abstract]	'
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	'
	Share-Based Compensation
	Share-based compensation expense is included in ‘compensation and benefits’ in the condensed consolidated income statements and totaled $1.1 million and $2.0 million for the three months ended March 31, 2014 and 2013, respectively, and $2.2 million and $3.6 million for the six months ended March 31, 2014 and 2013, respectively.
	Stock Option Plan
	The Company sponsors a stock option plan for its directors, officers, employees and consultants. The 2013 Stock Option Plan, which was approved by the Company’s Board of Directors and shareholders, authorizes the Company to issue stock options covering up to 1.0 million shares of the Company’s common stock. As of March 31, 2014, there were 0.9 million shares available for future grant under this plan. The Company settles stock option exercises with newly issued shares of common stock.
	Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions:
		Six Months Ended March 31, 2014
	Expected stock price volatility	34%
	Expected dividend yield	—%
	Risk free interest rate	0.80%
	Average expected life (in years)	2.88
	Expected stock price volatility rates are based primarily on the historical volatility. The Company has not paid dividends in the past and does not currently expect to do so in the future. Risk free interest rates are based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option award. The average expected life represents the estimated period of time that options or awards granted are expected to be outstanding, based on the Company’s historical share option exercise experience for similar option grants. The weighted average fair value of options issued during the six months ended March 31, 2014 was $4.48.
	The following is a summary of stock option activity for the six months ended March 31, 2014:
		Shares		Number of		Weighted		Weighted				Weighted	Aggregate
		Available for		Options		Average Price		Average				Average	Intrinsic
		Grant		Outstanding				Grant Date				Remaining	Value
								Fair Value				Term	($ millions)
												(in years)
	Balances as of September 30, 2013	1,000,000		1,779,983		$	24.76	$	11.44			4.87	$	4.8
	Granted	(86,500	)	86,500		$	19.24	$	4.48
	Exercised			(140,992	)	$	8.84	$	4.02
	Forfeited	—		(80,000	)	$	25.91	$	13.63
	Expired	—		(32,647	)	$	50.64	$	14.27
	Balances as of March 31, 2014	913,500		1,612,844		$	24.27	$	11.55			4.6	$	2.4
	Exercisable as of March 31, 2014			665,031		$	26.3	$	10.73			1.6	$	2.3
	The total compensation cost not yet recognized for non-vested awards of $8.6 million as of March 31, 2014 has a weighted-average period of 5.71 years over which the compensation expense is expected to be recognized. Compensation expense is amortized on a straight-line basis over the vesting period. The total intrinsic value of options exercised during the six months ended March 31, 2014 and 2013 was $1.7 million, respectively.
	Restricted Stock Plan
	The Company sponsors a restricted stock plan for its directors, officers and employees. As of March 31, 2014, 1,110,008 shares were authorized for future grant under the 2012 Restricted Stock Plan. Awards that expire or are canceled generally become available for issuance again under the plan. The Company utilizes newly issued shares of common stock to make restricted stock grants.
	The following is a summary of restricted stock activity for the six months ended March 31, 2014:
		Shares		Number of		Weighted		Weighted		Aggregate
		Available for		Shares		Average		Average		Intrinsic
		Grant		Outstanding		Grant Date		Remaining		Value
						Fair Value		Term		($ millions)
								(in years)
	Balances as of September 30, 2013	1,154,862		363,638		$	20.53	1.74		$	7.4
	Granted	(75,699	)	75,699		$	19.69
	Vested			(134,646	)	$	20.2
	Forfeited	30,845		(54,481	)	$	21.68
	Balances as of March 31, 2014	1,110,008		250,210		$	20.2	2.11		$	4.7
	The total compensation cost not yet recognized of $3.8 million as of March 31, 2014 has a weighted-average period of 2.11 years over which the compensation expense is expected to be recognized. Compensation expense is amortized on a straight-line basis over the vesting period. Restricted stock grants are included in the Company’s total issued and outstanding common shares.

Other_Expenses_Notes

Other Expenses (Notes)	6 Months Ended
	Mar. 31, 2014
Other Expenses [Abstract]	'
Other Expenses [Text Block]	'
	Other Expenses
	Other expenses for the three and six months ended March 31, 2014 and 2013 consisted of the following:
		Three Months Ended March 31,				Six Months Ended March 31,
	(in millions)	2014		2013		2014		2013
	Contingent consideration, net(1)	$	0.1	$	0.5	$	0.3	$	1.2
	Insurance	0.4		0.4		0.8		0.9
	Advertising, meetings and conferences	1.3		0.5		1.8		1.1
	Non-trading hardware and software maintenance and software licensing	0.8		0.9		1.5		1.5
	Office supplies and printing	0.3		0.3		0.5		0.7
	Other clearing related expenses	0.2		0.5		0.6		0.9
	Other non-income taxes	0.9		1.2		2		2.2
	Other	1.3		1.6		2.5		4.1
	Total other expenses	$	5.3	$	5.9	$	10	$	12.6
	-1	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 (see Note 3).

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss) (Notes)	6 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Abstract]	'
Comprehensive Income (Loss) Note [Text Block]	'
	Accumulated Other Comprehensive Income (Loss)
	Comprehensive income consists of net income and other gains and losses affecting stockholders’ equity that, under U.S. GAAP, are excluded from net income. Other comprehensive income (loss) includes net actuarial losses from defined benefit pension plans, unrealized gains on available-for-sale securities, and gains and losses on foreign currency translations.
	The following table summarizes the changes in accumulated other comprehensive income (loss) for the six months ended March 31, 2014.
	(in millions)	Foreign Currency Translation Adjustment			Pension Benefits Adjustment			Unrealized Gain or Loss on Available-for-Sale Securities			Accumulated Other Comprehensive Loss
	Balances as of September 30, 2013	$	(4.1	)	$	(2.8	)	$	0.5		$	(6.4	)
	Other comprehensive income (loss), net of tax before reclassifications	(3.9		)	0.2			—			(3.7		)
	Amounts reclassified from AOCI, net of tax	—			—			—		(1)	—
	Net current period other comprehensive income (loss), net of tax	(3.9		)	0.2			—			(3.7		)
	Balances as of March 31, 2014	$	(8.0	)	$	(2.6	)	$	0.5		$	(10.1	)
	(1) Amounts reclassified from OCI for the six months ended March 31, 2014 were less than $0.1 million.

Income_Taxes_Notes

Income Taxes (Notes)	6 Months Ended
	Mar. 31, 2014
Income Taxes [Abstract]	'
Income Tax Disclosure [Text Block]	'
	Income Taxes
	In determining the quarterly provision for income taxes, management uses an estimated annual effective tax rate which is based on the expected annual income and statutory tax rates in the various jurisdictions in which it operates. The Company’s effective tax rate differs from the U.S. statutory rate primarily due to state and local taxes, and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no tax benefit can be recognized are excluded from the estimated annual effective income tax rate.
	The Company is required to assess its deferred tax assets and the need for a valuation allowance at each reporting period. This assessment requires judgment on the part of management with respect to benefits that may be realized. The Company will record a valuation allowance against deferred tax assets when it is considered more likely than not that all or a portion of the deferred tax assets will not be realized.
	The valuation allowance for deferred tax assets as of March 31, 2014 and September 30, 2013 was $2.3 million. The net change in the total valuation allowance for the year ended September 30, 2013 was a decrease of $1.8 million. The valuation allowances as of March 31, 2014 and September 30, 2013 were primarily related to U.S. state and local and foreign net operating loss carryforwards that, in the judgment of management, are not more likely than not to be realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some or all of the deferred tax assets will not be realized.
	The Company incurred U.S. federal, state, and local taxable (losses) income for the fiscal years ended September 30, 2013, 2012, and 2011 of $(22.2) million, $(21.2) million, and $22.7 million, respectively. There are no significant differences between actual levels of past taxable income and the results of operations, before income taxes in these jurisdictions. U.S. federal, state, and local taxable losses incurred during the years ended September 30, 2013 and 2012 were attributable to a decrease in exchange-traded and OTC derivative transactional volumes and revenue caused by consecutive droughts in the U.S., as well as losses incurred in the physical base metals business. During 2013, the Company elected to pursue an exit of its physical base metals business through an orderly liquidation of open positions. Additionally, the Company completed an acquisition of the accounts of Tradewire Securities. Although both the exit of the physical base metals business and the acquisition of the Tradewire Securities accounts are expected to positively affect future levels of taxable income, the expected impact cannot be reliably projected. When evaluating if U.S. federal, state, and local deferred tax assets are realizable, the Company considered deferred tax liabilities of $4.3 million that are scheduled to reverse from 2014 to 2018 and $1.3 million of deferred tax liabilities associated with unrealized gains in securities which the Company could sell, if necessary. Furthermore, the Company considered its ability to implement business and tax planning strategies that would allow the remaining U.S. federal, state, and local deferred tax assets, net of valuation allowances, to be realized within approximately 9 years. Based on the tax planning strategies that can be implemented, management believes that it is more likely than not that the Company will realize the tax benefit of the deferred tax assets, net of the existing valuation allowance, in the future. However, the realization of deferred income taxes is dependent on future events, and changes in estimate in future periods could result in adjustments to the valuation allowance.
	The income tax expense from continuing operations of $2.6 million and $0.0 million for the three months ended March 31, 2014 and 2013, and income tax expense from continuing operations of $4.1 million and $3.9 million for the six months ended March 31, 2014 and 2013, respectively, reflect estimated federal, foreign and state taxes.
	For the three months ended March 31, 2014, the Company’s effective tax rate was 25% compared to 0% for the three months ended March 31, 2013. During the three months ended March 31, 2013, the Company recorded a net decrease to its uncertain tax benefits of $0.4 million, attributed to favorably settled income tax audits, of which $0.3 million impacted the Company's effective tax rate. For the six months ended March 31, 2014, the Company’s effective tax rate was 29% compared to 25% for the six months ended March 31, 2013.
	The Company and its subsidiaries file income tax returns with the U.S. federal jurisdiction and various state and foreign jurisdictions. The Company has open tax years ranging from September 30, 2008 through September 30, 2013 with U.S. federal and state and local taxing authorities. In the U.K., the Company has open tax years ending September 30, 2012 to September 30, 2013. In Brazil, the Company has open tax years ranging from December 31, 2008 through December 31, 2012. In Argentina, the Company has open tax years ranging from December 31, 2006 to September 30, 2013. The Internal Revenue Service commenced an examination of the U.S. income tax return for the fiscal year ended September 30, 2010. Additionally, INTL FCStone is under state examinations for various periods, ranging from September 2009 through September 30, 2012. The Company is also under examination in Nigeria for tax years 2006 through 2013.

Acquisitions_Notes

Acquisitions (Notes)	6 Months Ended
	Mar. 31, 2014
Acquisitions [Abstract]	'
Business Combination Disclosure [Text Block]	'
	Acquisitions
	First American Capital and Trading Corp.
	On November 18, 2013, First American Capital and Trading Corp. (“FACT”) transferred its customer accounts to INTL FCStone Inc.’s broker-dealer subsidiary, INTL FCStone Securities Inc. FACT provided correspondent clearing services to institutional customers directly and through a global network of partners. FACT serviced a wide range of customers, including broker-dealers, investment advisors, and fund managers.
	The consideration to be paid for the acquisition of institutional accounts from FACT consists of contingent payments based on the pre-tax earnings of the institutional account division created following this transfer. The purchase price for the acquisition is not material to the condensed consolidated financial statements.

Discontinued_Operations_Notes

Discontinued Operations (Notes)	6 Months Ended
	Mar. 31, 2014
Discontinued Operations [Abstract]	'
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	'
	Discontinued Operations
	Exit of Physical Base Metals Business
	During the second quarter of fiscal 2013, as a result of a change in management strategy in the Company’s base metals product line, the Company elected to pursue an exit of its physical base metals business through the sale and orderly liquidation of current open positions. During the following months, the Company completed a sale of a portion of the physical base metals open contract positions, and the liquidation of the majority of the remaining physical base metals open contract positions and inventory. The exit of the physical base metals business was substantially completed by the end of fiscal 2013, including the termination of the physical base metals trading team and certain operational support personnel. The remaining open contract positions were fulfilled during the second fiscal quarter of 2014. The Company has reclassified the physical base metals activities in the financial statements as discontinued operations beginning with the quarter ended March 31, 2014. The physical base metals business was previously included in the Commodity and Risk Management Services segment (see Note 19 – Segment Analysis). The Company continues to operate the portion of its base metals business related to non-physical assets, conducted primarily through the London Metals Exchange.
	Summarized below are the components of the Company’s income/(loss) from discontinued operations for the three and six months ended March 31, 2014:
		Three Months Ended March 31,				Six Months Ended March 31,
	(in millions)	2014		2013		2014		2013
	Total revenues from discontinued operations	11.6		419.2		40.9		834.5
	Total cost of sales of physical commodities from discontinued operations	11.4		416.8		40.2		824.8
	Operating revenues	0.2		2.4		0.7		9.7
	(Loss) income from discontinued operations before income taxes	(0.2	)	(0.2	)	(0.1	)	4.5
	Income tax benefit	—		—		—		(1.5	)
	(Loss) income from discontinued operations, net of tax	(0.2	)	(0.2	)	(0.1	)	3

Segment_Analysis_Notes

Segment Analysis (Notes)	6 Months Ended
	Mar. 31, 2014
Segment Analysis [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	Segment Analysis
	The Company reports its operating segments based on services provided to customers. Commencing during the quarter ended March 31, 2014, the Company’s operating segments were reorganized into reportable segments as follows:
	•	Commercial Hedging which includes Financial Agricultural (Ag’s) & Energy (formerly discussed as the soft commodities product line) and LME metals, previously components of Commodity and Risk Management Services.
	•	Global Payments, which was previously a component, along with FX Prime Brokerage, of the Foreign Exchange segment, has been broken out as the single component of a segment named Global Payments.
	•	Securities now includes Asset Management, previously a component of Other, as an additional component along with Equity market-making, Debt Trading and Investment Banking.
	•	Physical Commodities includes physical precious metals, previously a component of Commodity and Risk Management Services along with Physical Ag’s & Energy (formerly discussed as the commodity financing and facilitation business), previously a component of Other. In addition, physical base metals, previously a component of Commodity and Risk Management Services, is now reported as discontinued operations, and is not part of the Physical Commodities segment information.
	•	Clearing and Execution Services now includes the FX Prime Brokerage component as an additional component.
	All segment information has been revised to reflect the operating segment reorganization retroactive to October 1, 2012.
	Commercial Hedging
	The Company serves its commercial clients through its team of risk management consultants, providing a high-value-added service that we believe differentiates it from its competitors and maximizes the opportunity to retain clients. The Company’s risk management consulting services are designed to quantify and monitor commercial entities’ exposure to commodity and financial risk. Upon assessing this exposure the Company develops a plan to control and hedge these risks with post-trade reporting against specific client objectives. Clients are assisted in the execution of their hedging strategies through a wide range of products from listed exchange-traded futures and options, to basic OTC instruments that offer greater flexibility, to structured OTC products designed for customized solutions.
	The Company’s services span virtually all traded commodity markets, with the largest concentrations in agricultural and energy commodities (consisting primarily of grains, energy and renewable fuels, coffee, sugar, cotton, and food service) and base metals. The Company’s base metals business includes a position as a Category One ring dealing member of the LME, providing execution, clearing and advisory services in exchange-traded futures and OTC products. The Company also provides execution of foreign currency forwards and options as well as a wide range of structured product solutions to commercial clients who are seeking cost-effective hedging strategies. Generally, clients direct their own trading activity and the Company’s risk management consultants do not have discretionary authority to transact trades on behalf of clients.
	Global Payments
	The Company provides global payment solutions to banks and commercial businesses as well as charities and non-governmental organizations and government organizations. The Company offers payments services in over 150 currencies, which it believes is more than any other payments solution provider, and provides competitive and transparent pricing. Through its technology platform, full-service electronic execution capability and commitment to customer service, the Company believes it is able to provide simple and fast execution, ensuring delivery of funds in any of these countries quickly through its global network of correspondent banks. In this business, the Company primarily acts as a principal in buying and selling foreign currencies on a spot basis. The Company derives revenue from the difference between the purchase and sale prices.
	The Company believes its clients value the Company’s ability to provide exchange rates that are significantly more competitive than those offered by large international banks, a competitive advantage that stems from our years of foreign exchange expertise focused on smaller, less liquid currencies. Additionally, as a member of SWIFT (Society for Worldwide Interbank Financial Telecommunication), the Company is able to offer its services to large money center and global banks seeking more competitive international payments services.
	Securities
	Through INTL FCStone Securities Inc., the Company provides value-added solutions that facilitate cross-border trading. The Company believes its clients value the Company’s ability to manage complex transactions, including foreign exchange, utilizing its local understanding of market convention, liquidity and settlement protocols around the world. The Company’s clients include U.S.-based regional and national broker-dealers and institutions investing or executing customer transactions in international markets and foreign institutions seeking access to the U.S. securities markets. The Company is one of the leading market makers in foreign securities, including unlisted ADRs and foreign ordinary shares. The Company makes markets in approximately 800 ADRs and foreign ordinary shares traded in the OTC market and will, on request, make prices in more than 8,000 other ADRs and foreign common shares. In addition, the Company is a broker-dealer in Argentina where it is active in providing institutional executions in the local capital markets.
	The Company provides a full range of corporate finance advisory services to its middle market clients, including capital market solutions and a wide array of advisory services across a broad spectrum of industries. The Company’s advisory services span mergers and acquisitions, liability management, restructuring opinions and valuations. The Company also originates, structures and places a wide array of debt instruments in the international and domestic capital markets. These instruments include complex asset-backed securities (primarily in Argentina), unsecured bond and loan issues, negotiable notes and other trade-related debt instruments used in cross-border trade finance. On occasion, the Company may invest its own capital in debt instruments before selling them. The Company also actively trades in a variety of international debt instruments and operates an asset management business in which it earns fees, commissions and other revenues for management of third party assets and investment gains or losses on its investments in funds and proprietary accounts managed either by its investment managers or by independent investment managers.
	Physical Commodities
	This segment consists of the Company’s physical precious metals trading and physical agricultural and energy commodity business. In precious metals, the Company provides a full range of trading and hedging capabilities, including OTC products, to select producers, consumers, and investors. In the Company’s trading activities, it acts as a principal, committing its own capital to buy and sell precious metals on a spot and forward basis.
	The Company’s physical agricultural and energy commodity business provides financing to commercial commodity-related companies against physical inventories, including grain, lumber, meats, energy products and renewable fuels. The Company uses sale and repurchase agreements to purchase commodities evidenced by warehouse receipts, subject to a simultaneous agreement to sell such commodities back to the original seller at a later date. These transactions are accounted for as product financing arrangements, and accordingly no commodity inventory, purchases or sales are recorded. Additionally, the Company engages as a principal in physical purchase and sale transactions related to inputs to the renewable fuels and feed ingredient industries.
	The Company records its physical commodities revenues on a gross basis. Operating revenues and losses from its commodities derivatives activities are included in ‘trading gains, net’ in the condensed consolidated income statements. Inventory for the commodities business is valued at the lower of cost or fair value under the provisions of the Inventory Topic of the ASC. The Company generally mitigates the price risk associated with commodities held in inventory through the use of derivatives. The Company does not elect hedge accounting under U.S. GAAP in accounting for this price risk mitigation. In such situations, unrealized gains in inventory are not recognized under U.S. GAAP, but unrealized gains and losses in related derivative positions are recognized under U.S. GAAP. As a result, reported earnings from physical commodities trading may be subject to significant volatility when calculated under U.S. GAAP.
	Clearing and Execution Services (CES)
	The Company seeks to provide competitive and efficient clearing and execution of exchange-traded futures and options for the institutional and professional trader market segments. Through its platform, customer orders are accepted and directed to the appropriate exchange for execution. The Company then facilitates the clearing of clients’ transactions. Clearing involves the matching of clients’ trades with the exchange, the collection and management of client margin deposits to support the transactions, and the accounting and reporting of the transactions to customers. The Company seeks to leverage its capabilities and capacity by offering facilities management or outsourcing solutions to other FCMs.
	In addition, the Company provides prime brokerage foreign exchange services to financial institutions and professional traders. The Company provides its customers with the full range of OTC products, including 24 hour execution of spot, forwards and options as well as non-deliverable forwards in both liquid and exotic currencies. The Company also operates a proprietary foreign exchange desk which arbitrages the exchange-traded foreign exchange markets with the cash markets.
	********
	The total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. In order to reflect the way that the Company’s management views the results, the tables below also reflect the segment contribution to ‘operating revenues’, which is shown on the face of the condensed consolidated income statements and which is calculated by deducting physical commodities cost of sales from total revenues.
	Segment data includes the profitability measure of net contribution by segment. Net contribution is one of the key measures used by management to assess the performance of each segment and for decisions regarding the allocation of the Company’s resources. Net contribution is calculated as revenue less direct cost of sales, transaction-based clearing expenses, variable compensation, introducing broker commissions, and interest expense. Variable compensation paid to risk management consultants/traders generally represents a fixed percentage of an amount equal to revenues generated, and in some cases, revenues produced less transaction-based clearing charges, base salaries and an overhead allocation.
	Segment data also includes segment income which is calculated as net contribution less non-variable direct expenses of the segment. These non-variable direct expenses include trader base compensation and benefits, operational employee compensation and benefits, communication and data services, business development, professional fees, bad debt expense and other direct expenses.
	Inter-segment revenues, charges, receivables and payables are eliminated upon consolidation, except revenues and costs related to foreign currency transactions undertaken on an arm’s length basis by the foreign exchange trading business for the securities business. The foreign exchange trading business competes for this business as it does for any other business. If its rates are not competitive, the securities businesses buy or sell their foreign currency through other market counterparties.
	On a recurring basis, the Company sweeps excess cash from certain operating segments to a centralized corporate treasury function in exchange for an intercompany receivable asset. The intercompany receivable asset is eliminated during consolidation, and therefore this practice may impact reported total assets between segments.
	Information concerning operations in these segments of business is shown in accordance with the Segment Reporting Topic of the ASC as follows:
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions)	2014			2013			2014			2013
	Total revenues:
	Commercial Hedging	$	63.8		$	51.7		$	109.4		$	101.2
	Global Payments	12.8			9.3			26.4			19.4
	Securities	17.2			18			38.6			32.7
	Physical Commodities	8,328.80			11,660.00			16,129.80			23,687.30
	Clearing and Execution Services	30.9			30.8			58.4			58
	Corporate unallocated	(0.6		)	(0.5		)	(1.0		)	8.2
	Total	$	8,452.90		$	11,769.30		$	16,361.60		$	23,906.80
	Operating revenues (loss):
	Commercial Hedging	$	63.8		$	51.7		$	109.4		$	101.2
	Global Payments	12.8			9.3			26.4			19.4
	Securities	17.2			18			38.6			32.7
	Physical Commodities	5.1			5.6			10.3			13.8
	Clearing and Execution Services	30.9			30.8			58.4			58
	Corporate unallocated	(0.6		)	(0.5		)	(1.0		)	8.2
	Total	$	129.2		$	114.9		$	242.1		$	233.3
	Net operating revenues (loss):
	Commercial Hedging	$	52.6		$	41.5		$	88.8		$	82.4
	Global Payments	11			8			22.8			17.3
	Securities	11.8			13.3			27.4			24
	Physical Commodities	4.2			4.6			8.7			11.7
	Clearing and Execution Services	8.4			8.2			15.5			15.5
	Corporate unallocated	(2.1		)	(0.5		)	(3.9		)	7.5
	Total	$	85.9		$	75.1		$	159.3		$	158.4
	Net contribution:
	(Revenues less cost of sales, transaction-based clearing expenses, variable bonus compensation, introducing broker commissions and interest expense)
	Commercial Hedging	$	38.3		$	29.5		$	65.1		$	61
	Global Payments	8.6			6.2			17.8			13.1
	Securities	8.9			10.6			20.8			18.9
	Physical Commodities	3.6			3			7.2			8.8
Clearing and Execution Services	6.5			6.3			12.2			12.2
Total	$	65.9		$	55.6		$	123.1		$	114
Segment income:
(Net contribution less non-variable direct segment costs)
Commercial Hedging	$	22.6		$	13.4		$	34.7		$	29.4
Global Payments	6.3			4.6			13.3			9.6
Securities	3.8			5.4			11			9.6
Physical Commodities	1.7			0.9			3.5			5
Clearing and Execution Services	2.1			1.7			3.4			1.7
Total	$	36.5		$	26		$	65.9		$	55.3
Reconciliation of segment income to income from continuing operations, before tax:
Segment income	$	36.5		$	26		$	65.9		$	55.3
Costs not allocated to operating segments	26.2			24.3			51.7			39.6
Income from continuing operations, before tax	$	10.3		$	1.7		$	14.2		$	15.7
(continued)
(in millions)							As of March 31, 2014			As of September 30, 2013
Total assets:
Commercial Hedging							$	1,330.40		$	1,005.10
Global Payments							44			57.2
Securities							207.2			204.2
Physical Commodities							167.5			132.5
Clearing and Execution Services							1,150.70			1,333.30
Corporate unallocated							115.3			115.7
Total							$	3,015.10		$	2,848.00

Basis_of_Presentation_and_Cons1

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Policies)	6 Months Ended
	Mar. 31, 2014
Basis of Presentation and Consolidation [Abstract]	'
Basis of Accounting, Policy [Policy Text Block]	'
	The accompanying condensed consolidated balance sheet as of September 30, 2013, 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, 2013 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]	'
	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.
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, 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.
New Accounting Pronouncements, Policy [Policy Text Block]	'
	Recent Accounting Pronouncements
	On December 16, 2011, the Financial Accounting Standards Board (“FASB”) issued new guidance on the disclosures about offsetting assets and liabilities. The amended guidance limits the scope of balance sheet offsetting to derivatives, repurchase agreements and securities lending transactions to the extent that they are offset in the financial statements or subject to an enforceable master netting arrangement or similar agreement. 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 adopted this guidance starting with the first quarter ended December 31, 2013. The adoption of this guidance did not have a material impact on the Company’s disclosures within the notes to its condensed consolidated financial statements. Refer to Note 4 and Note 10 of the notes to the condensed consolidated financial statements for disclosure of assets and liabilities regarding the Company's derivative instruments and repurchase agreements.
	In February 2013, the FASB issued Accounting Standards Update (“ASU”) No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income requiring new disclosures regarding reclassification adjustments from accumulated other comprehensive income (“AOCI”). ASU No. 2013-02 requires disclosure of amounts reclassified out of AOCI by component. In addition, the entity is required to present, either on the face of the statement where net income is presented or the notes, significant amounts reclassified out of AOCI by the respective line items of net income. The Company adopted this guidance starting with the first quarter ended December 31, 2013. The adoption of this guidance did not have a material impact on the presentation of the Company’s condensed consolidated financial statements.
	In March 2013, the FASB issued ASU No. 2013-05, Parent’s Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity, which addresses the accounting for the cumulative translation adjustment when a parent either sells part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. For public entities, the ASU is effective prospectively for fiscal years, and interim periods, within those years, beginning after December 15, 2013. Early adoption is permitted. The Company expects to adopt this guidance starting with the first quarter of fiscal year 2015. The adoption of this guidance is not expected to have a material impact on the Company’s condensed consolidated financial statements.
	In July 2013, the FASB issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This ASU provides that an unrecognized tax benefit, or a portion thereof, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except to the extent that a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date to settle any additional income taxes that would result from disallowance of a tax position, or the tax law does not require the entity to use, and the entity does not intend to use, the deferred tax asset for such purpose, then the unrecognized tax benefit should be presented as a liability. For public entities, the ASU is effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The Company expects to adopt this guidance starting with the first quarter of fiscal year 2015. The adoption of ASU 2013-11 is not expected to have a material impact on the Company’s condensed consolidated financial statements.
	In April 2014, the FASB issued updated guidance on reporting discontinued operations and disclosures of disposals of components of an entity. Under the amendment only those disposals of components of an entity that represent a strategic shift that has (or will have) a major effect on an entity’s operations and financial results will be reported as discontinued operations in the financial statements. Next, the elimination of the component's operations, cash flows and significant continuing involvement conditions have been removed. Lastly, an equity method investment could be reported as discontinued operations. The updated guidance is effective prospectively for all disposals or classifications as held for sale that occur within annual periods beginning after December 15, 2014. The Company does not expect the adoption of this guidance to have a material impact on the condensed consolidated financial statements.

Earnings_per_Share_Policies

Earnings per Share (Policies)	6 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share, Potentially Dilutive Securities	'
	The dilutive effect of share-based awards is reflected in diluted net income per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense required under the Compensation – Stock Compensation Topic of the Accounting Standards Codification (“ASC”).

Receivables_From_Customers_Net1

Receivables From Customers, Net and Notes Receivable, Net (Policies)	6 Months Ended
	Mar. 31, 2014
Receivables from customers and notes receivable, net [Abstract]	'
Allowance for Receivables from Customers and Notes Receivables [Policy Text Block]	'
	Receivables from customers, net and notes receivable, net include an allowance for bad debts, which reflects the Company’s best estimate of probable losses inherent in the receivables from customers and notes receivable. The Company provides for an allowance for doubtful accounts based on a specific-identification basis. The Company continually reviews its allowance for bad debts.

Commitments_and_Contingencies_1

Commitments and Contingencies (Policies)	6 Months Ended
	Mar. 31, 2014
Commitments and Contingencies [Abstract]	'
Commitments and Contingencies, Policy [Policy Text Block]	'
	Certain conditions may exist as of the date that the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. In assessing loss contingencies related to legal and regulatory proceedings that are pending against the Company or unasserted claims that may result in such proceedings, the Company’s legal counsel evaluates the perceived merits of any legal proceedings or unasserted claims as well as the perceived merits of the amount of relief sought or expected to be sought therein.
	If the assessment of a contingency indicates that it is probable that a material loss had been incurred at the date of the financial statements and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potentially material loss contingency is not probable, but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, together with an estimate of the range of possible loss if determinable and material, would be disclosed. Neither accrual nor disclosure is required for loss contingencies that are deemed remote. The Company accrues legal fees related to contingent liabilities as they are incurred.

Income_Taxes_Policies

Income Taxes (Policies)	6 Months Ended
	Mar. 31, 2014
Income Taxes [Abstract]	'
Income Tax, Policy [Policy Text Block]	'
	In determining the quarterly provision for income taxes, management uses an estimated annual effective tax rate which is based on the expected annual income and statutory tax rates in the various jurisdictions in which it operates. The Company’s effective tax rate differs from the U.S. statutory rate primarily due to state and local taxes, and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no tax benefit can be recognized are excluded from the estimated annual effective income tax rate.
	The Company is required to assess its deferred tax assets and the need for a valuation allowance at each reporting period. This assessment requires judgment on the part of management with respect to benefits that may be realized. The Company will record a valuation allowance against deferred tax assets when it is considered more likely than not that all or a portion of the deferred tax assets will not be realized.

Earnings_per_Share_Tables

Earnings per Share (Tables)	6 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block]	'
	Basic EPS has been computed by dividing net income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted net income per share computations for the periods presented below.
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions, except share amounts)	2014			2013			2014			2013
	Numerator:
	Income from continuing operations	$	7.7		$	1.7		$	10.1		$	11.8
	Less: Allocation to participating securities	(0.2		)	(0.1		)	(0.3		)	(0.5		)
	Income from continuing operations allocated to common stockholders	$	7.5		$	1.6		$	9.8		$	11.3
	(Loss) income from discontinued operations	$	(0.2	)	$	(0.2	)	$	(0.1	)	$	3
	Less: Allocation to participating securities	—			—			—			(0.1		)
	(Loss) income from discontinued operations allocated to common stockholders	$	(0.2	)	$	(0.2	)	$	(0.1	)	$	2.9
	Diluted net income	$	7.5		$	1.5		$	10		$	14.8
	Less: Allocation to participating securities	(0.2		)	(0.1		)	(0.3		)	(0.6		)
	Diluted net income allocated to common stockholders	$	7.3		$	1.4		$	9.7		$	14.2
	Denominator:
	Weighted average number of:
	Common shares outstanding	18,609,550			18,380,971			18,627,383			18,327,517
	Dilutive potential common shares outstanding:
	Share-based awards	345,578			453,621			646,770			494,282
	Diluted weighted-average shares	18,955,128			18,834,592			19,274,153			18,821,799

Assets_and_Liabilities_at_Fair1

Assets and Liabilities, at Fair Value (Tables)	6 Months Ended
	Mar. 31, 2014
Assets and Liabilities, at Fair Value [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	'
	The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of March 31, 2014 and September 30, 2013 by level in the fair value hierarchy. There were no assets or liabilities that were measured at fair value on a nonrecurring basis as of March 31, 2014 and September 30, 2013.
		March 31, 2014
	(in millions)	Level 1			Level 2			Level 3			Netting and			Total
											Collateral
											-1
	Assets:
	Unrestricted cash equivalents - certificate of deposits	$	3.3		$	—		$	—		$	—		$	3.3
	Commodities warehouse receipts	17.4			—			—			—			17.4
	U.S. government obligations	—			14.5			—			—			14.5
	Securities and other assets segregated under federal and other regulations	17.4			14.5			—			—			31.9
	Money market funds	354.2			—			—			—			354.2
	U.S. government obligations	—			833.8			—			—			833.8
	Mortgage-backed securities	—			3.3			—			—			3.3
	Derivatives	2,277.00			—			—			(2,283.1		)	(6.1		)
	Deposits and receivables from exchange-clearing organizations	2,631.20			837.1			—			(2,283.1		)	1,185.20
	Deposits and receivables from broker-dealers, clearing organizations and counterparties - derivatives	1.8			—			—			(7.0		)	(5.2		)
	Common and preferred stock and American Depositary Receipts (“ADRs”)	63.4			14.8			0.7			—			78.9
	Exchangeable foreign ordinary equities and ADRs	21.1			—			—			—			21.1
	Corporate and municipal bonds	0.2			0.7			3.4			—			4.3
	U.S. government obligations	—			0.3			—			—			0.3
	Foreign government obligations	10			—			—			—			10
	Derivatives	280.2			804.1			—			(1,058.7		)	25.6
	Commodities leases	—			58			—			(51.1		)	6.9
	Commodities warehouse receipts	0.3			—			—			—			0.3
	Exchange firm common stock	4.4			—			—			—			4.4
	Mutual funds and other	3			—			—			—			3
	Mortgage-backed securities	—			1.4			—			—			1.4
	Financial instruments owned	382.6			879.3			4.1			(1,109.8		)	156.2
	Total assets at fair value	$	3,036.30		$	1,730.90		$	4.1		$	(3,399.9	)	$	1,371.40
	Liabilities:
	Accounts payable and other accrued liabilities - contingent liabilities	$	—		$	—		$	9.2		$	—		$	9.2
	Payable to customers - derivatives	2,726.80			—			—			(2,726.8		)	—
	Common and preferred stock and ADRs	61.6			11.4			—			—			73
	Exchangeable foreign ordinary equities and ADRs	19.4			—			—			—			19.4
	Corporate and municipal bonds	0.1			0.7			—			—			0.8
	Derivatives	286.1			806.3			—			(1,027.5		)	64.9
	Commodities leases	—			123.1			—			(63.7		)	59.4
	Financial instruments sold, not yet purchased	367.2			941.5			—			(1,091.2		)	217.5
	Total liabilities at fair value	$	3,094.00		$	941.5		$	9.2		$	(3,818.0	)	$	226.7
	-1	Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.
		September 30, 2013
	(in millions)	Level 1			Level 2			Level 3			Netting and			Total
											Collateral
											-1
	Assets:
	Money market funds	$	0.1		$	—		$	—		$	—		$	0.1
	Certificate of deposits	2.9			—			—			—			2.9
	Unrestricted cash equivalents	3			—			—			—			3
	Money market funds	75			—			—			—			75
	Commodities warehouse receipts	13.1			—			—			—			13.1
	U.S. government obligations	—			19.5			—			—			19.5
	Securities and other assets segregated under federal and other regulations	88.1			19.5			—			—			107.6
	Money market funds	841.4			—			—			—			841.4
	U.S. government obligations	—			594.8			—			—			594.8
	Mortgage-backed securities	—			5.3			—			—			5.3
	Derivatives	2,263.20			—			—			(2,333.0		)	(69.8		)
	Deposits and receivables from exchange-clearing organizations	3,104.60			600.1			—			(2,333.0		)	1,371.70
	Deposits and receivables from broker-dealers, clearing organizations and counterparties - derivatives	1.8			0.2			—			(15.1		)	(13.1		)
	Common and preferred stock and American Depositary Receipts (“ADRs”)	49.3			19.8			0.7			—			69.8
	Exchangeable foreign ordinary equities and ADRs	36.7			—			—			—			36.7
	Corporate and municipal bonds	0.1			—			3.5			—			3.6
	U.S. government obligations	—			0.3			—			—			0.3
	Foreign government obligations	7.7			—			—			—			7.7
Derivatives	173.6			440.6			—			(592.3		)	21.9
Commodities leases	—			56.1			—			(50.0		)	6.1
Commodities warehouse receipts	4			—			—			—			4
Exchange firm common stock	4.4			—			—			—			4.4
Mutual funds and other	4			—			—			—			4
Financial instruments owned	279.8			516.8			4.2			(642.3		)	158.5
Total assets at fair value	$	3,477.30		$	1,136.60		$	4.2		$	(2,990.4	)	$	1,627.70
Liabilities:
Accounts payable and other accrued liabilities - contingent liabilities	$	—		$	—		$	9.6		$	—		$	9.6
Payable to customers - derivatives	2,328.20			—			—			(2,328.2		)	—
Common and preferred stock and ADRs	82.9			16.6			—			—			99.5
Exchangeable foreign ordinary equities and ADRs	8.7			—			—			—			8.7
Derivatives	174			473.2			—			(616.5		)	30.7
Commodities leases	—			85.5			—			(44.5		)	41
Financial instruments sold, not yet purchased	265.6			575.3			—			(661.0		)	179.9
Total liabilities at fair value	$	2,593.80		$	575.3		$	9.6		$	(2,989.2	)	$	189.5
-1	Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	'
	Information on Level 3 Financial Assets and Liabilities
	The Company’s financial assets at fair value classified in level 3 of the fair value hierarchy as of March 31, 2014 and September 30, 2013 are summarized below:
	(in millions)	March 31, 2014			September 30, 2013
	Total level 3 assets	$	4.1		$	4.2
	Level 3 assets for which the Company bears economic exposure	$	4.1		$	4.2
	Total assets	$	3,015.10		$	2,848.00
	Total financial assets at fair value	$	1,371.40		$	1,627.70
	Total level 3 assets as a percentage of total assets	0.1		%	0.1		%
	Level 3 assets for which the Company bears economic exposure as a percentage of total assets	0.1		%	0.1		%
	Total level 3 assets as a percentage of total financial assets at fair value	0.3		%	0.3		%
	The following tables set forth a summary of changes in the fair value of the Company’s level 3 financial assets and liabilities during the three and six months ended March 31, 2014 and 2013, including a summary of unrealized gains (losses) during the respective periods on the Company’s level 3 financial assets and liabilities still held as of March 31, 2014.
		Level 3 Financial Assets and Financial Liabilities
		For the Three Months Ended March 31, 2014
	(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
		beginning of			(losses) during			gains (losses)									or (out) of		end of period
		period			period			during period									Level 3
	Assets:
	Common stock and ADRs	$	0.7		$	—		$	—		$	—		$	—		$	—	$	0.7
	Corporate and municipal bonds	3.4			—			—			—			—			—		3.4
		$	4.1		$	—		$	—		$	—		$	—		$	—	$	4.1
	Liabilities:
	Contingent liabilities	$	9.1		$	—		$	0.1		$	—		$	—		$	—	$	9.2
		Level 3 Financial Assets and Financial Liabilities
		For the Six Months Ended March 31, 2014
	(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
		beginning of			(losses) during			gains (losses)									or (out) of		end of period
		period			period			during period									Level 3
	Assets:
	Common stock and ADRs	$	0.7		$	—		$	—		$	—		$	—		$	—	$	0.7
	Corporate and municipal bonds	3.5			—			(0.1		)	—			—			—		3.4
		$	4.2		$	—		$	(0.1	)	$	—		$	—		$	—	$	4.1
	Liabilities:
	Contingent liabilities	$	9.6		$	—		$	0.3		$	—		$	(0.7	)	$	—	$	9.2
		Level 3 Financial Assets and Financial Liabilities
		For the Three Months Ended March 31, 2013
	(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
		beginning of			(losses) during			gains (losses)									or (out) of		end of period
		period			period			during period									Level 3
	Assets:
	Common stock and ADRs	$	0.9		$	—		$	—		$	—		$	—		$	—	$	0.9
	Corporate and municipal bonds	3.6			—			0.2			—			—			—		3.8
		$	4.5		$	—		$	0.2		$	—		$	—		$	—	$	4.7
	Liabilities:
	Contingent liabilities	$	17.9		$	—		$	0.5		$	—		$	—		$	—	$	18.4
		Level 3 Financial Assets and Financial Liabilities
		For the Six Months Ended March 31, 2013
	(in millions)	Balances at			Realized gains			Unrealized			Purchases/issuances			Settlements			Transfers in		Balances at
		beginning of			(losses) during			gains (losses)									or (out) of		end of period
		period			period			during period									Level 3
	Assets:
	Common stock and ADRs	$	0.9		$	—		$	—		$	—		$	—		$	—	$	0.9
	Corporate and municipal bonds	3.6			—			0.2			—			—			—		3.8
		$	4.5		$	—		$	0.2		$	—		$	—		$	—	$	4.7
	Liabilities:
	Contingent liabilities	$	14.8		$	—		$	0.8		$	3.1		$	(0.3	)	$	—	$	18.4
Available-for-sale Securities [Table Text Block]	'
	The following tables summarize the amortized cost basis, the aggregate fair value and gross unrealized holding gains and losses of the Company’s investment securities classified as available-for-sale as of March 31, 2014 and September 30, 2013:
	March 31, 2014
	Amounts included in deposits with and receivables from exchange-clearing organizations and financial instruments owned:
		Amortized			Unrealized Holding						Estimated
	(in millions)	Cost			Gains			(Losses)			Fair Value
	U.S. government obligations	$	806.5		$	0.1		$	—		$	806.6
	Mortgage-backed securities	4.6			0.1			—			4.7
		$	811.1		$	0.2		$	—		$	811.3
	September 30, 2013
	Amounts included in deposits with and receivables from exchange-clearing organizations:
		Amortized			Unrealized Holding(1)						Estimated
	(in millions)	Cost			Gains			(Losses)			Fair Value
	U.S. government obligations	$	568.5		$	—		$	—		$	568.5
	Mortgage-backed securities	5.2			0.1			—			5.3
		$	573.7		$	0.1		$	—		$	573.8
	(1) Unrealized gain/loss on U.S. government obligations as of September 30, 2013, was less than $0.1 million.
	As of March 31, 2014 and September 30, 2013, investments in debt securities classified as available-for-sale (“AFS”) mature as follows:
	March 31, 2014
		Due in						Estimated
	(in millions)	Less than 1 year			1 year or more			Fair Value
	U.S. government obligations	$	806.6		$	—		$	806.6
	Mortgage-backed securities	—			4.7			4.7
		$	806.6		$	4.7		$	811.3
	September 30, 2013
		Due in						Estimated
	(in millions)	Less than 1 year			1 year or more			Fair Value
	U.S. government obligations	$	568.5		$	—		$	568.5
	Mortgage-backed securities	—			5.3			5.3
		$	568.5		$	5.3		$	573.8
	Except as discussed previously, there were no other sales of AFS securities during the three months ended March 31, 2014 and 2013, and as a result, no realized gains or losses were recorded for the three months ended March 31, 2014 and 2013.
	For the purposes of the maturity schedule, mortgage-backed securities, which are not due at a single maturity date, have been allocated over maturity groupings based on the expected maturity of the underlying collateral. Mortgage-backed securities may mature earlier than their stated contractual maturities because of accelerated principal repayments of the underlying loans.

Financial_Instruments_with_Off1

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	6 Months Ended
	Mar. 31, 2014
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]	'
Schedule of Derivative Instruments [Table Text Block]	'
	Listed below are the fair values of the Company’s derivative assets and liabilities as of March 31, 2014 and September 30, 2013. Assets represent net unrealized gains and liabilities represent net unrealized losses.
		March 31, 2014						September 30, 2013
	(in millions)	Assets (1)			Liabilities (1)			Assets (1)			Liabilities (1)
	Derivative contracts not accounted for as hedges:
	Exchange-traded commodity derivatives	$	2,121.60		$	2,535.80		$	2,036.60		$	2,046.30
	OTC commodity derivatives	844.8			849			481.4			484.9
	Exchange-traded foreign exchange derivatives	74.7			70.3			89.3			104.2
	OTC foreign exchange derivatives	238.6			243.4			132.3			162.3
	Exchange-traded interest rate derivatives	8.1			6.8			4.3			36
	Equity index derivatives	75.3			113.9			135.5			141.7
	Gross fair value of derivative contracts	3,363.10			3,819.20			2,879.40			2,975.40
	Impact of netting and collateral	(3,348.8		)	(3,754.3		)	(2,940.4		)	(2,944.7		)
	Total fair value included in ‘Deposits and receivables from exchange-clearing organizations’	$	(6.1	)				$	(69.8	)
	Total fair value included in ‘Deposits and receivables from broker-dealers, clearing organizations and counterparties’	$	(5.2	)				$	(13.1	)
	Total fair value included in ‘Financial instruments owned, at fair value’	$	25.6					$	21.9
	Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’				$	64.9					$	30.7
	-1	As of March 31, 2014 and September 30, 2013, the Company’s derivative contract volume for open positions were approximately 4.2 million and 4.1 million contracts, respectively.
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block]	'
	The following table sets forth the Company’s gains (losses) related to derivative financial instruments for the three and six months ended March 31, 2014 and 2013, in accordance with the Derivatives and Hedging Topic of the ASC. The gains (losses) set forth below are included in ‘trading gains, net’ and ‘income (loss) from discontinued operations, net of tax’ in the condensed consolidated income statements.
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions)	2014			2013			2014			2013
	Commodities	$	21.9		$	10.8		$	30.6		$	41.4
	Foreign exchange	2.7			3.1			4.8			5.7
	Interest rate	—			—			—			0.1
	Net gains (losses) from derivative contracts	$	24.6		$	13.9		$	35.4		$	47.2

Physical_Commodities_Inventory1

Physical Commodities Inventory (Tables)	6 Months Ended
	Mar. 31, 2014
Physical Commodities Inventory [Abstract]	'
Schedule of Inventory, Current [Table Text Block]	'
	The carrying values of the Company’s inventory as of March 31, 2014 and September 30, 2013 are shown below.
	(in millions)	March 31,		September 30, 2013
		2014
	Commodities in process	$	0.3	$	—
	Finished commodities	67.6		59
	Physical commodities inventory - finished commodities	$	67.9	$	59

Goodwill_Tables

Goodwill (Tables)	6 Months Ended
	Mar. 31, 2014
Goodwill [Abstract]	'
Schedule of Goodwill [Table Text Block]	'
	The carrying value of goodwill by segment is as follows:
	(in millions)	March 31,		September 30,
		2014		2013
	Commercial Hedging	$	33.1	$	33.1
	Global Payments	6.3		6.3
	Securities	8.1		8.1
	Goodwill	$	47.5	$	47.5

Intangible_Assets_Tables

Intangible Assets - (Tables)	6 Months Ended
	Mar. 31, 2014
Intangible Assets [Abstract]	'
Schedule of Finite and Indefinite-Lived Intangible Assets [Table Text Block]	'
	The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows:
		March 31, 2014							September 30, 2013
	(in millions)	Gross Amount		Accumulated			Net Amount		Gross Amount		Accumulated			Net Amount
				Amortization							Amortization
	Intangible assets subject to amortization
	Noncompete agreement	$	—	$	—		$	—	$	3.7	$	(3.7	)	$	—
	Trade name	—		—			—		0.7		(0.7		)	—
	Software programs/platforms	2.2		(1.7		)	0.5		2.2		(1.5		)	0.7
	Customer base	12.4		(3.0		)	9.4		12.4		(2.6		)	9.8
		14.6		(4.7		)	9.9		19		(8.5		)	10.5
	Intangible assets not subject to amortization
	Trade name	1.1		—			1.1		1.1		—			1.1
	Total intangible assets	$	15.7	$	(4.7	)	$	11	$	20.1	$	(8.5	)	$	11.6
Schedule of Expected Amortization Expense [Table Text Block]	'
	Amortization expense related to intangible assets was $0.6 million and $1.1 million for the six months ended March 31, 2014 and 2013, respectively.
	As of March 31, 2014, the estimated future amortization expense was as follows:
	(in millions)
	Fiscal 2014 (remaining six months)	$	0.7
	Fiscal 2015	1.1
	Fiscal 2016	0.7
	Fiscal 2017	0.7
	Fiscal 2018	0.7
	Fiscal 2019 and thereafter	6
		$	9.9

Credit_Facilities_Tables

Credit Facilities (Tables)	6 Months Ended
	Mar. 31, 2014
Credit Facilities [Abstract]	'
Schedule of Debt [Table Text Block]	'
	as of March 31, 2014 and September 30, 2013:
	(in millions)
	Credit Facilities						Amounts Outstanding
		Borrower	Security	Renewal / Expiration Date	Total Commitment		March 31,		September 30,
							2014		2013
		INTL FCStone Inc.	Certain pledged shares	September 20, 2016	$	140	$	24	$	55
		FCStone, LLC	None	April 9, 2015	75		—		—
		FCStone Merchants	Certain commodities assets	May 1, 2015	30		16.5		6
		INTL FCStone, Ltd.	None	November 10, 2014	25		—		—
					$	270	$	40.5	$	61
	Senior Unsecured Notes
		8.50% senior notes, due July 30, 2020					45.5		45.5
	Total indebtedness						$	86	$	106.5

Capital_and_Other_Regulatory_R1

Capital and Other Regulatory Requirements (Tables)	6 Months Ended
	Mar. 31, 2014
Capital and Other Regulatory Requirements [Abstract]	'
Regulatory Capital Requirements under Banking Regulations [Text Block]	'
	Capital and Other Regulatory Requirements
	The Company’s activities are subject to significant governmental regulation, both in the United States and overseas. The subsidiaries of the Company were in compliance with all of their regulatory requirements as of March 31, 2014, as follows:
	(in millions)			As of March 31, 2014
	Subsidiary	Regulatory Authority	Requirement Type	Actual		Minimum
						Requirement
	FCStone, LLC	CFTC	Net capital	$	125.6	$	86.5
	FCStone, LLC	CFTC	Segregated funds	$	1,864.80	$	1,838.20
	FCStone, LLC	CFTC	Secured funds	$	64.9	$	48.1
	INTL FCStone Ltd	FCA (United Kingdom)	Net capital	$	59.6	$	46.3
	INTL FCStone Ltd	FCA (United Kingdom)	Segregated funds	$	112.7	$	112.6
	INTL Global Currencies Limited	FCA (United Kingdom)	Net capital	$	20.5	$	0.9
	INTL FCStone Securities Inc.	SEC	Net capital	$	5	$	1
	FCC Investments, Inc.	SEC	Net capital	$	0.3	$	0.3
	FCStone Australia	Australian Securities and Investment Commission	Net capital	$	1.7	$	0.9
	FCStone Australia	Australian Securities and Investment Commission	Segregated funds	$	22.4	$	14.9
	FCStone Australia	New Zealand Clearing Ltd	Capital adequacy	$	11.6	$	4.3
	INTL FCStone DTVM Ltda.	Brazilian Central Bank and Securities and Exchange Commission of Brazil	Capital adequacy	$	0.9	$	0.6
	INTL Capital S.A.	Rosario Futures Exchange (Argentina)	Capital adequacy	$	3.9	$	0.1
	INTL Capital S.A.	General Inspector of Justice (Argentina)	Net capital	$	6.1	$	5.9
	INTL CIBSA Sociedad de Bolsa S.A.	Superintendent of Securities Markets of Buenos Aires (Argentina)	Net capital	$	4.6	$	0.2
	Certain other non-U.S. subsidiaries of the Company are also subject to capital adequacy requirements promulgated by authorities of the countries in which they operate. As of March 31, 2014, these subsidiaries were in compliance with their local capital adequacy requirements.

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	6 Months Ended
	Mar. 31, 2014
Stock-Based Compensation [Abstract]	'
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	'
	Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions:
		Six Months Ended March 31, 2014
	Expected stock price volatility	34%
	Expected dividend yield	—%
	Risk free interest rate	0.80%
	Average expected life (in years)	2.88
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	'
	The following is a summary of stock option activity for the six months ended March 31, 2014:
		Shares		Number of		Weighted		Weighted				Weighted	Aggregate
		Available for		Options		Average Price		Average				Average	Intrinsic
		Grant		Outstanding				Grant Date				Remaining	Value
								Fair Value				Term	($ millions)
												(in years)
	Balances as of September 30, 2013	1,000,000		1,779,983		$	24.76	$	11.44			4.87	$	4.8
	Granted	(86,500	)	86,500		$	19.24	$	4.48
	Exercised			(140,992	)	$	8.84	$	4.02
	Forfeited	—		(80,000	)	$	25.91	$	13.63
	Expired	—		(32,647	)	$	50.64	$	14.27
	Balances as of March 31, 2014	913,500		1,612,844		$	24.27	$	11.55			4.6	$	2.4
	Exercisable as of March 31, 2014			665,031		$	26.3	$	10.73			1.6	$	2.3
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]	'
	The following is a summary of restricted stock activity for the six months ended March 31, 2014:
		Shares		Number of		Weighted		Weighted		Aggregate
		Available for		Shares		Average		Average		Intrinsic
		Grant		Outstanding		Grant Date		Remaining		Value
						Fair Value		Term		($ millions)
								(in years)
	Balances as of September 30, 2013	1,154,862		363,638		$	20.53	1.74		$	7.4
	Granted	(75,699	)	75,699		$	19.69
	Vested			(134,646	)	$	20.2
	Forfeited	30,845		(54,481	)	$	21.68
	Balances as of March 31, 2014	1,110,008		250,210		$	20.2	2.11		$	4.7

Other_Expenses_Tables

Other Expenses (Tables)	6 Months Ended
	Mar. 31, 2014
Other Expenses [Abstract]	'
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	'
	Other expenses for the three and six months ended March 31, 2014 and 2013 consisted of the following:
		Three Months Ended March 31,				Six Months Ended March 31,
	(in millions)	2014		2013		2014		2013
	Contingent consideration, net(1)	$	0.1	$	0.5	$	0.3	$	1.2
	Insurance	0.4		0.4		0.8		0.9
	Advertising, meetings and conferences	1.3		0.5		1.8		1.1
	Non-trading hardware and software maintenance and software licensing	0.8		0.9		1.5		1.5
	Office supplies and printing	0.3		0.3		0.5		0.7
	Other clearing related expenses	0.2		0.5		0.6		0.9
	Other non-income taxes	0.9		1.2		2		2.2
	Other	1.3		1.6		2.5		4.1
	Total other expenses	$	5.3	$	5.9	$	10	$	12.6
	-1	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 (see Note 3).

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
	The following table summarizes the changes in accumulated other comprehensive income (loss) for the six months ended March 31, 2014.
	(in millions)	Foreign Currency Translation Adjustment			Pension Benefits Adjustment			Unrealized Gain or Loss on Available-for-Sale Securities			Accumulated Other Comprehensive Loss
	Balances as of September 30, 2013	$	(4.1	)	$	(2.8	)	$	0.5		$	(6.4	)
	Other comprehensive income (loss), net of tax before reclassifications	(3.9		)	0.2			—			(3.7		)
	Amounts reclassified from AOCI, net of tax	—			—			—		(1)	—
	Net current period other comprehensive income (loss), net of tax	(3.9		)	0.2			—			(3.7		)
	Balances as of March 31, 2014	$	(8.0	)	$	(2.6	)	$	0.5		$	(10.1	)
	(1) Amounts reclassified from OCI for the six months ended March 31, 2014 were less than $0.1 million.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	6 Months Ended
	Mar. 31, 2014
Discontinued Operations [Abstract]	'
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	'
	Summarized below are the components of the Company’s income/(loss) from discontinued operations for the three and six months ended March 31, 2014:
		Three Months Ended March 31,				Six Months Ended March 31,
	(in millions)	2014		2013		2014		2013
	Total revenues from discontinued operations	11.6		419.2		40.9		834.5
	Total cost of sales of physical commodities from discontinued operations	11.4		416.8		40.2		824.8
	Operating revenues	0.2		2.4		0.7		9.7
	(Loss) income from discontinued operations before income taxes	(0.2	)	(0.2	)	(0.1	)	4.5
	Income tax benefit	—		—		—		(1.5	)
	(Loss) income from discontinued operations, net of tax	(0.2	)	(0.2	)	(0.1	)	3

Segment_Analysis_Tables

Segment Analysis (Tables)	6 Months Ended
	Mar. 31, 2014
Segment Analysis [Abstract]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
	Information concerning operations in these segments of business is shown in accordance with the Segment Reporting Topic of the ASC as follows:
		Three Months Ended March 31,						Six Months Ended March 31,
	(in millions)	2014			2013			2014			2013
	Total revenues:
	Commercial Hedging	$	63.8		$	51.7		$	109.4		$	101.2
	Global Payments	12.8			9.3			26.4			19.4
	Securities	17.2			18			38.6			32.7
	Physical Commodities	8,328.80			11,660.00			16,129.80			23,687.30
	Clearing and Execution Services	30.9			30.8			58.4			58
	Corporate unallocated	(0.6		)	(0.5		)	(1.0		)	8.2
	Total	$	8,452.90		$	11,769.30		$	16,361.60		$	23,906.80
	Operating revenues (loss):
	Commercial Hedging	$	63.8		$	51.7		$	109.4		$	101.2
	Global Payments	12.8			9.3			26.4			19.4
	Securities	17.2			18			38.6			32.7
	Physical Commodities	5.1			5.6			10.3			13.8
	Clearing and Execution Services	30.9			30.8			58.4			58
	Corporate unallocated	(0.6		)	(0.5		)	(1.0		)	8.2
	Total	$	129.2		$	114.9		$	242.1		$	233.3
	Net operating revenues (loss):
	Commercial Hedging	$	52.6		$	41.5		$	88.8		$	82.4
	Global Payments	11			8			22.8			17.3
	Securities	11.8			13.3			27.4			24
	Physical Commodities	4.2			4.6			8.7			11.7
	Clearing and Execution Services	8.4			8.2			15.5			15.5
	Corporate unallocated	(2.1		)	(0.5		)	(3.9		)	7.5
	Total	$	85.9		$	75.1		$	159.3		$	158.4
	Net contribution:
	(Revenues less cost of sales, transaction-based clearing expenses, variable bonus compensation, introducing broker commissions and interest expense)
	Commercial Hedging	$	38.3		$	29.5		$	65.1		$	61
	Global Payments	8.6			6.2			17.8			13.1
	Securities	8.9			10.6			20.8			18.9
	Physical Commodities	3.6			3			7.2			8.8
	Clearing and Execution Services	6.5			6.3			12.2			12.2
	Total	$	65.9		$	55.6		$	123.1		$	114
	Segment income:
	(Net contribution less non-variable direct segment costs)
	Commercial Hedging	$	22.6		$	13.4		$	34.7		$	29.4
	Global Payments	6.3			4.6			13.3			9.6
	Securities	3.8			5.4			11			9.6
	Physical Commodities	1.7			0.9			3.5			5
	Clearing and Execution Services	2.1			1.7			3.4			1.7
	Total	$	36.5		$	26		$	65.9		$	55.3
	Reconciliation of segment income to income from continuing operations, before tax:
	Segment income	$	36.5		$	26		$	65.9		$	55.3
	Costs not allocated to operating segments	26.2			24.3			51.7			39.6
	Income from continuing operations, before tax	$	10.3		$	1.7		$	14.2		$	15.7
	(continued)
	(in millions)							As of March 31, 2014			As of September 30, 2013
	Total assets:
	Commercial Hedging							$	1,330.40		$	1,005.10
	Global Payments							44			57.2
	Securities							207.2			204.2
	Physical Commodities							167.5			132.5
	Clearing and Execution Services							1,150.70			1,333.30
	Corporate unallocated							115.3			115.7
	Total							$	3,015.10		$	2,848.00

Basis_of_Presentation_and_Cons2

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Revenues	$8,452.90	$11,769.30	$16,361.60	$23,906.80
Cost of sales of physical commodities	8,323.70	11,654.40	16,119.50	23,673.50
Number of different types of foreign currencies	'	'	150	'
Number of accounts for customers company-wide	'	'	20,000	'
Number of customers company-wide	'	'	11,000	'
Scenario, Previously Reported [Member]	'	'	'	'
Revenues	'	13,113.10	'	25,832.60
Cost of sales of physical commodities	'	12,995.80	'	25,589.60
Scenario, Adjustment [Member]	'	'	'	'
Revenues	'	-924.6	'	-1,091.30
Cost of sales of physical commodities	'	-924.6	'	-1,091.30
Restatement Adjustment [Member]	'	'	'	'
Revenues	'	12,188.50	'	24,741.30
Cost of sales of physical commodities	'	$12,071.20	'	$24,498.30

Earnings_per_Share_Antidulitiv

Earnings per Share - Antidulitive Securities (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,332,197	1,490,288	1,132,782	1,490,288

Earnings_per_Share_EPS_Reconci

Earnings per Share - EPS Reconciliation (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]	'	'	'	'
Income from continuing operations	$7.70	$1.70	$10.10	$11.80
Less: Allocation to participating securities	-0.2	-0.1	-0.3	-0.5
Income from continuing operations allocated to common stockholders	7.5	1.6	9.8	11.3
(Loss) income from discontinued operations, net of tax	-0.2	-0.2	-0.1	3
Less: Allocation to participating securities	0	0	0	-0.1
(Loss) income from discontinued operations allocated to common stockholders	-0.2	-0.2	-0.1	2.9
Diluted net income	7.5	1.5	10	14.8
Less: Allocation to participating securities	-0.2	-0.1	-0.3	-0.6
Diluted net income allocated to common stockholders	$7.30	$1.40	$9.70	$14.20
Weighted average number of common shares outstanding	18,609,550	18,380,971	18,627,383	18,327,517
Share-based awards	345,578	453,621	646,770	494,282
Diluted weighted-average shares	18,955,128	18,834,592	19,274,153	18,821,799

Assets_and_Liabilities_at_Fair2

Assets and Liabilities, at Fair Value Assets and Liabilities, at Fair Value - Financial Instruments at Fair Value Disclosure (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Assets and Liabilities, at Fair Value [Abstract]	'	'
Long-term Debt, Fair Value	$48.70	'
Senior unsecured notes	$45.50	$45.50

Assets_and_Liabilities_at_Fair3

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	$715.70	$449.40
Receivables from Clearing Organizations	1,488.70	1,576.60
Receivables from Brokers-Dealers and Clearing Organizations	128.3	168.3
Financial Instruments, Owned, at Fair Value	156.2	158.5
Assets, Fair Value Disclosure	1,371.40	1,627.70
Accounts Payable and Other Accrued Liabilities	95.6	114
Payables to Customers	2,268	2,091.80
Financial Instruments Sold, Not yet Purchased, at Fair Value	217.5	179.9
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	3.3	3
Cash and Securities Segregated under Federal and Other Regulations	31.9	107.6
Receivables from Clearing Organizations	1,185.20	1,371.70
Receivables from Brokers-Dealers and Clearing Organizations	-5.2	-13.1
Financial Instruments, Owned, at Fair Value	156.2	158.5
Assets, Fair Value Disclosure	1,371.40	'
Financial Instruments Sold, Not yet Purchased, at Fair Value	217.5	'
Liabilities, Fair Value Disclosure	226.7	189.5
Fair Value, Measurements, Recurring [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Payables to Customers	0	0
Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accounts Payable and Other Accrued Liabilities	9.2	9.6
Fair Value, Measurements, Recurring [Member] | Common stock and American Depositary Receipts (ADRs) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	78.9	69.8
Financial Instruments Sold, Not yet Purchased, at Fair Value	73	99.5
Fair Value, Measurements, Recurring [Member] | Exchangeable foreign ordinary equities and ADRs [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	21.1	36.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	19.4	8.7
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	4.3	3.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.8	'
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.3	0.3
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	10	7.7
Fair Value, Measurements, Recurring [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	25.6	21.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	64.9	30.7
Fair Value, Measurements, Recurring [Member] | Commodities leases and unpriced positions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	6.9	6.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	59.4	41
Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.3	4
Fair Value, Measurements, Recurring [Member] | Exchange firm common stock [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	4.4	4.4
Fair Value, Measurements, Recurring [Member] | Mutual funds and other [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	3	4
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	1.4	'
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	354.2	841.4
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	833.8	594.8
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	3.3	5.3
Fair Value, Measurements, Recurring [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	-6.1	-69.8
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	'	75
Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	17.4	13.1
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	14.5	19.5
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0.1
Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	2.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	3.3	3
Cash and Securities Segregated under Federal and Other Regulations	17.4	88.1
Receivables from Clearing Organizations	2,631.20	3,104.60
Receivables from Brokers-Dealers and Clearing Organizations	1.8	1.8
Financial Instruments, Owned, at Fair Value	382.6	279.8
Assets, Fair Value Disclosure	3,036.30	3,477.30
Financial Instruments Sold, Not yet Purchased, at Fair Value	367.2	265.6
Liabilities, Fair Value Disclosure	3,094	2,593.80
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Payables to Customers	2,726.80	2,328.20
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Consideration [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accounts Payable and Other Accrued Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Common stock and American Depositary Receipts (ADRs) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	63.4	49.3
Financial Instruments Sold, Not yet Purchased, at Fair Value	61.6	82.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchangeable foreign ordinary equities and ADRs [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	21.1	36.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	19.4	8.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.2	0.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.1	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	10	7.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	280.2	173.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	286.1	174
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases and unpriced positions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.3	4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange firm common stock [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	4.4	4.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual funds and other [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	3	4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	354.2	841.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	2,277	2,263.20
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	'	75
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	17.4	13.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	2.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Cash and Securities Segregated under Federal and Other Regulations	14.5	19.5
Receivables from Clearing Organizations	837.1	600.1
Receivables from Brokers-Dealers and Clearing Organizations	0	0.2
Financial Instruments, Owned, at Fair Value	879.3	516.8
Assets, Fair Value Disclosure	1,730.90	1,136.60
Financial Instruments Sold, Not yet Purchased, at Fair Value	941.5	575.3
Liabilities, Fair Value Disclosure	941.5	575.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Payables to Customers	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Consideration [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accounts Payable and Other Accrued Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Common stock and American Depositary Receipts (ADRs) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	14.8	19.8
Financial Instruments Sold, Not yet Purchased, at Fair Value	11.4	16.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchangeable foreign ordinary equities and ADRs [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.7	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.7	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.3	0.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	804.1	440.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	806.3	473.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases and unpriced positions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	58	56.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	123.1	85.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange firm common stock [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual funds and other [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	1.4	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	833.8	594.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	3.3	5.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	'	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	14.5	19.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Cash and Securities Segregated under Federal and Other Regulations	0	0
Receivables from Clearing Organizations	0	0
Receivables from Brokers-Dealers and Clearing Organizations	0	0
Financial Instruments, Owned, at Fair Value	4.1	4.2
Assets, Fair Value Disclosure	4.1	4.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Liabilities, Fair Value Disclosure	9.2	9.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Payables to Customers	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accounts Payable and Other Accrued Liabilities	9.2	9.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Common stock and American Depositary Receipts (ADRs) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0.7	0.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchangeable foreign ordinary equities and ADRs [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	3.4	3.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities leases and unpriced positions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange firm common stock [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual funds and other [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	'	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0
Fair Value, Measurements, Recurring [Member] | Netting [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Cash and Securities Segregated under Federal and Other Regulations	0	0
Receivables from Clearing Organizations	-2,283.10	-2,333
Receivables from Brokers-Dealers and Clearing Organizations	-7	-15.1
Financial Instruments, Owned, at Fair Value	-1,109.80	-642.3
Assets, Fair Value Disclosure	-3,399.90	-2,990.40
Financial Instruments Sold, Not yet Purchased, at Fair Value	-1,091.20	-661
Liabilities, Fair Value Disclosure	-3,818	-2,989.20
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Payables to Customers	-2,726.80	-2,328.20
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Contingent Consideration [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accounts Payable and Other Accrued Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Common stock and American Depositary Receipts (ADRs) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Exchangeable foreign ordinary equities and ADRs [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Corporate Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Foreign Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	-1,058.70	-592.3
Financial Instruments Sold, Not yet Purchased, at Fair Value	-1,027.50	-616.5
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Commodities leases and unpriced positions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	-51.1	-50
Financial Instruments Sold, Not yet Purchased, at Fair Value	-63.7	-44.5
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Exchange firm common stock [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Mutual funds and other [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial Instruments, Owned, at Fair Value	0	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Collateralized Mortgage Backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Receivables from Clearing Organizations	-2,283.10	-2,333
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	'	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Commodities warehouse receipts [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | US Government Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and Cash Equivalents, Fair Value Disclosure	'	$0

Assets_and_Liabilities_at_Fair4

Assets and Liabilities, at Fair Value - Details of Level 3 Assets and Liabilities (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Assets and Liabilities, at Fair Value [Abstract]	'	'
Total Level 3 Assets	$4.10	$4.20
Level 3 assets for which the company bears economic exposure	4.1	4.2
Assets	3,015.10	2,848
Assets, Fair Value Disclosure	1,371.40	1,627.70
Total level 3 assets as a percentage of total assets	0.10%	0.10%
Level 3 assets for which the company bears economic exposure as a percertange of total assets	0.10%	0.10%
Total level 3 assets as a percentage of total financial assets at fair value	0.30%	0.30%
Suriwongse Debt Investment Balance	$3.40	'

Assets_and_Liabilities_at_Fair5

Assets and Liabilities, at Fair Value - Rollforward of Level 3 (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Rollforward of Level 3 Securities [Roll Forward]	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$4.10	$4.50	$4.20	$4.50
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0.2	-0.1	0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	4.1	4.7	4.1	4.7
Contingent Consideration [Member]	'	'	'	'
Rollforward of Level 3 Liabilities [Roll Forward]	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	9.1	17.9	9.6	14.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	0.1	0.5	0.3	0.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0	0	0	3.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0	0	-0.7	-0.3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	9.2	18.4	9.2	18.4
Common stock and American Depositary Receipts (ADRs) [Member]	'	'	'	'
Rollforward of Level 3 Securities [Roll Forward]	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0.7	0.9	0.7	0.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0.7	0.9	0.7	0.9
Corporate Debt Securities [Member]	'	'	'	'
Rollforward of Level 3 Securities [Roll Forward]	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3.4	3.6	3.5	3.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0.2	-0.1	0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$3.40	$3.80	$3.40	$3.80

Assets_and_Liabilities_at_Fair6

Assets and Liabilities, at Fair Value - Contingent Consideration (Details) (Contingent Consideration [Member], USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Contingent Consideration [Member]	'	'	'	'
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	$0.10	$0.50	$0.30	$0.80

Assets_and_Liabilities_at_Fair7

Assets and Liabilities, at Fair Value - Available for Sale Securities in OCI (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2014	Sep. 30, 2013
Assets and Liabilities, at Fair Value [Abstract]	'	'	'
Equity Investments in Exchange Stock - Cost	'	$3.70	$3.70
Equity Investments in Exchange Stock - Fair Value	'	4.4	4.4
Proceeds from Sale of Available-for-sale Securities	8.6	'	'
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax - LME Shares	6.3	'	'
Deferred Tax Liabilities, Accumulated Other Comprehensive Income - LME Shares	2	'	'
Proceeds from Shares of Exchanges Sold	1.5	'	'
Gain (Loss) on Sale of Exchange Shares	0.9	'	'
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	'	0.5	0.5
Deferred Income Taxes, Accumulated Other Comprehensive Income - AFS	'	($0.30)	($0.30)

Assets_and_Liabilities_at_Fair8

Assets and Liabilities, at Fair Value - Available for Sale Securities - Dep and Rec (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Debt Securities, Amortized Cost Basis	$811.10	$573.70
Available-for-sale Securities, Gross Unrealized Gains	0.2	0.1
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Debt Securities	811.3	573.8
US Government Debt Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Debt Securities, Amortized Cost Basis	806.5	568.5
Available-for-sale Securities, Gross Unrealized Gains	0.1	0
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Debt Securities	806.6	568.5
Collateralized Mortgage Backed Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Debt Securities, Amortized Cost Basis	4.6	5.2
Available-for-sale Securities, Gross Unrealized Gains	0.1	0.1
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Debt Securities	4.7	5.3
Deposits and Receivables from Exchange Clearing Organizations [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Securities, Gross Unrealized Gain (Loss)	'	$0.10

Assets_and_Liabilities_at_Fair9

Assets and Liabilities, at Fair Value - Available for Sale Securities (Maturities) (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	$806.60	$568.50
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	4.7	5.3
Available-for-sale Securities, Debt Securities	811.3	573.8
US Government Debt Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	806.6	568.5
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	0	0
Available-for-sale Securities, Debt Securities	806.6	568.5
Collateralized Mortgage Backed Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	4.7	5.3
Available-for-sale Securities, Debt Securities	$4.70	$5.30

Financial_Instruments_with_Off2

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Obligations to Purchase Financial Instruments at a Future Date (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Financial Instruments Sold, Not yet Purchased, at Fair Value	$217.50	$179.90
Financial instrument sold, not yet purchased [Member]	'	'
Derivative, Fair Value, Net	$64.90	$30.70

Financial_Instruments_with_Off3

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Gross Derivative Assets and Liabilities by Type and Balance Sheet Location (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	$3,363.10	$2,879.40
Derivative Liability, Fair Value, Gross Liability	3,819.20	2,975.40
Derivative Asset, Fair Value, Amount Offset Against Collateral	-3,348.80	-2,940.40
Derivative Liability, Fair Value, Amount Offset Against Collateral	-3,754.30	-2,944.70
Exchange-traded Commodity Contracts [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	2,121.60	2,036.60
Derivative Liability, Fair Value, Gross Liability	2,535.80	2,046.30
Over the Counter (OTC) Commodity Contracts [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	844.8	481.4
Derivative Liability, Fair Value, Gross Liability	849	484.9
Foreign Exchange Forward [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	74.7	89.3
Derivative Liability, Fair Value, Gross Liability	70.3	104.2
Over the Counter (OTC) Foreign Exchange Contracts [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	238.6	132.3
Derivative Liability, Fair Value, Gross Liability	243.4	162.3
Exchange-traded interest rate contracts [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	8.1	4.3
Derivative Liability, Fair Value, Gross Liability	6.8	36
Equity Contract [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative Asset, Fair Value, Gross Asset	75.3	135.5
Derivative Liability, Fair Value, Gross Liability	113.9	141.7
Deposits and Receivables from Exchange Clearing Organizations [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Fair Value, Net	-6.1	-69.8
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Fair Value, Net	-5.2	-13.1
Financial instruments owned [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Fair Value, Net	25.6	21.9
Financial instrument sold, not yet purchased [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Fair Value, Net	$64.90	$30.70

Financial_Instruments_with_Off4

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details)	Mar. 31, 2014	Sep. 30, 2013
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]	'	'
Derivative, Number of Instruments Held	4,200,000	4,100,000

Financial_Instruments_with_Off5

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Commodity Contract [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$21.90	$10.80	$30.60	$41.40
Foreign Exchange Forward [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	2.7	3.1	4.8	5.7
Interest Rate Contract [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0	0	0	0.1
Derivative [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$24.60	$13.90	$35.40	$47.20

Receivables_From_Customers_Net2

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Customer Receivables (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Receivables from customers and notes receivable, net [Abstract]	'	'	'	'	'
Allowance for Doubtful Accounts Receivable	$1.60	'	$1.60	'	$1.10
Provision for Doubtful Accounts	0.4	0.1	0.7	0.1	'
Provision Increase (Decrease)	0.1	'	0.4	'	'
Allowance for Doubtful Accounts Receivable, Write-offs	$0.30	'	$0.30	'	'

Receivables_From_Customers_Net3

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Notes Receivable (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Receivables from customers and notes receivable, net [Abstract]	'	'
Allowance Notes Receivable	$0.10	$0.10

Receivables_From_Customers_Net4

Receivables From Customers, Net and Notes Receivable, Net - Exim Bank Notes Receivable (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Insured short-term notes receivable	$33.50	$21.10
Obligations for participation rights	$30.60	$18.70
Minimum [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Short Term Notes Receivable Outstanding Balance Threshold, Percentage	90.00%	'
Maximum [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Short Term Notes Receivable Outstanding Balance Threshold, Percentage	98.00%	'

Physical_Commodities_Inventory2

Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Physical Commodities Inventory [Abstract]	'	'
Commodities in process	$0.30	$0
Finished commodities	67.6	59
Physical commodities inventory	$67.90	$59

Physical_Commodities_Inventory3

Physical Commodities Inventory - LCM Adjustments (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Physical Commodities Inventory [Abstract]	'	'
Inventory Adjustments	$0.30	$0.90

Goodwill_Goodwill_by_Segment_D

Goodwill - Goodwill by Segment (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Goodwill [Line Items]	'	'
Goodwill	$47.50	$47.50
Commercial Hedging [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	33.1	33.1
Global Payments [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	6.3	6.3
Securities [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	$8.10	$8.10

Intangible_Assets_Gross_and_Ne

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Finite-Lived Intangible Assets, Gross	$14.60	$19
Finite-Lived Intangible Assets, Accumulated Amortization	-4.7	-8.5
Finite-Lived Intangible Assets, Net	9.9	10.5
Noncompete Agreements [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Finite-Lived Noncompete Agreements, Gross	0	3.7
Finite-Lived Intangible Assets, Accumulated Amortization	0	-3.7
Finite-Lived Intangible Assets, Net	0	0
Trade Names [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Finite-Lived Trade Names, Gross	0	0.7
Finite-Lived Intangible Assets, Accumulated Amortization	0	-0.7
Finite-Lived Intangible Assets, Net	0	0
Computer Software, Intangible Asset [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Finite-Lived Computer Software, Gross	2.2	2.2
Finite-Lived Intangible Assets, Accumulated Amortization	-1.7	-1.5
Finite-Lived Intangible Assets, Net	0.5	0.7
Customer Relationships [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Finite-Lived Customer Lists, Gross	12.4	12.4
Finite-Lived Intangible Assets, Accumulated Amortization	-3	-2.6
Finite-Lived Intangible Assets, Net	$9.40	$9.80

Intangible_Assets_IndefiniteLi

Intangible Assets - Indefinite-Lived Intangible Assets (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Finite and Indefinite-Lived Intangible Assets	$15.70	$20.10
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	-4.7	-8.5
Intangible Assets, Net (Excluding Goodwill)	11	11.6
Trade Names [Member]	'	'
Indefinite-lived Intangible Assets [Line Items]	'	'
Indefinite-Lived Trade Names	1.1	1.1
Indefinite-lived Intangible Assets, Impairment Losses	$0	$0

Intangible_Assets_FiniteLived_

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Intangible Assets [Abstract]	'	'	'
Amortization of Intangible Assets	$0.60	$1.10	'
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]	'	'	'
Fiscal 2014, Remainder of Fiscal Year	0.7	'	'
Fiscal 2015	1.1	'	'
Fiscal 2016	0.7	'	'
Fiscal 2017	0.7	'	'
Fiscal 2018	0.7	'	'
Fiscal 2019 and thereafter	6	'	'
Finite-Lived Intangible Assets, Net	$9.90	'	$10.50

Credit_Facilities_Number_of_Cr

Credit Facilities - Number of Credit Facilities (Details)	Mar. 31, 2014
Credit Facilities [Abstract]	'
Number of credit facilities	4

Credit_Facilities_Credit_Facil

Credit Facilities - Credit Facilities (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Amount Outstanding	$40.50	$61
Senior unsecured notes	45.5	45.5
Debt and Capital Lease Obligations	86	106.5
Debt Instrument, Interest Rate, Stated Percentage	8.50%	'
Debt Instrument, Call Feature, Redemption Price Percentage of Principal	100.00%	'
Debt Issuance Cost	1.7	'
Main line of credit facilities [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Maximum Borrowing Capacity	270	'
Line of Credit Facility, Current Borrowing Capacity	25	'
HCO Syndicated line of credit facility [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Maximum Borrowing Capacity	140	'
Line of Credit Facility, Amount Outstanding	24	55
FCS Margin line of credit facility [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Maximum Borrowing Capacity	75	'
Line of Credit Facility, Amount Outstanding	0	0
FMS Sub-note commodity line of credit facility [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Maximum Borrowing Capacity	30	'
Line of Credit Facility, Amount Outstanding	16.5	6
INTL FCStone Ltd [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Maximum Borrowing Capacity	25	'
Line of Credit Facility, Amount Outstanding	$0	$0

Commodity_and_Other_Repurchase1

Commodity and Other Repurchase Agreements Commodity and Other Repurchase Agreements (Details) (USD $)	Mar. 31, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
Commodity and Other Repurchase Agreements [Abstract]	'	'
Financing Receivables, net - Sales/Repurchase Agreements	$24.70	$9.20
Obligations outstanding related to commodities sold under repurchase agreements	$16.50	$6

Commitments_and_Contingencies_2

Commitments and Contingencies - Contingencies and Litigation (Details) (USD $)	6 Months Ended
	Mar. 31, 2014
Litigation Settlement, Amount	$265,000
Excess segregated funds returned	15,500,000
Excess segregated funds invested	21,900,000
Pre and Post Transfers of Funds related to Sentinel	15,500,000
Customer Segregated Transfers of Funds Pursuant to Safe Harbor	1,100,000
Sentinel Appeal Cash Deposit	8,000,000
Minimum [Member]	'
Excess segregated funds returned	4,000,000
Maximum [Member]	'
Excess segregated funds returned	$6,000,000

Commitments_and_Contingencies_3

Commitments and Contingencies - Contigent Consideration for Acquisitions (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Business Acquisition, Contingent Consideration [Line Items]	'	'	'	'	'
Business Combination, Contingent Consideration, Liability	$9.20	'	$9.20	'	$9.60
Change in fair value of contingent consideration for acquisitions	0.1	0.5	0.3	3.9	'
Tradewire Acquisition [Member] [Member]	'	'	'	'	'
Business Acquisition, Contingent Consideration [Line Items]	'	'	'	'	'
Business Combination, Contingent Consideration, Liability	6.5	'	6.5	'	'
Change in fair value of contingent consideration for acquisitions	'	'	0.2	'	'
Coffee Network Acquisition [Member]	'	'	'	'	'
Business Acquisition, Contingent Consideration [Line Items]	'	'	'	'	'
Business Combination, Contingent Consideration, Liability	0.1	'	0.1	'	'
Hencorp Acquisition [Member]	'	'	'	'	'
Business Acquisition, Contingent Consideration [Line Items]	'	'	'	'	'
Business Combination, Contingent Consideration, Liability	2.6	'	2.6	'	'
Change in fair value of contingent consideration for acquisitions	'	'	0.1	0.2	'
Present Value of Estimated Total Purchase Price	7.6	'	7.6	'	'
Contingent Consideration [Member]	'	'	'	'	'
Business Acquisition, Contingent Consideration [Line Items]	'	'	'	'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	$0.10	$0.50	$0.30	$0.80	'

Commitments_and_Contingencies_4

Commitments and Contingencies Commitments and Contingencies - Self Insurance (Details) (USD $)	Mar. 31, 2014
In Millions, unless otherwise specified
Commitments and Contingencies [Abstract]	'
Self Insurance Reserve	$0.50

Capital_and_Other_Regulatory_R2

Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) (USD $)	Mar. 31, 2014
In Millions, unless otherwise specified
FCStone LLC [Member]	'
Net Capital under Commodity Exchange Act Computation	$125.60
Required Net Capital under Commodity Exchange Act	86.5
Cash and Securities Segregated under Commodity Exchange Act Regulation	1,864.80
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	1,838.20
Secured Funds	64.9
Secured Funds Required Under Commodity Exchange Act	48.1
INTL FCStone Ltd [Member]	'
Net Capital under Commodity Exchange Act Computation	59.6
Required Net Capital under Commodity Exchange Act	46.3
Cash and Securities Segregated under Commodity Exchange Act Regulation	112.7
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	112.6
INTL Global Currencies [Member]	'
Net Capital under Commodity Exchange Act Computation	20.5
Required Net Capital under Commodity Exchange Act	0.9
INTL Trading [Member]	'
Net Capital	5
Minimum Net Capital Required for Entity	1
FCC Investments [Member]	'
Net Capital	0.3
Minimum Net Capital Required for Entity	0.3
FCStone Australia [Member]	'
Net Capital under Commodity Exchange Act Computation	1.7
Required Net Capital under Commodity Exchange Act	0.9
Net Capital	11.6
Cash and Securities Segregated under Commodity Exchange Act Regulation	22.4
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	14.9
Capital Required for Capital Adequacy	4.3
INTL FCStone DTVM Ltda [Member]	'
Net Capital	0.9
Capital Required for Capital Adequacy	0.6
INTL Capital S.A b Rosario Futures Exchanges [Member] [Domain]	'
Net Capital	3.9
Capital Required for Capital Adequacy	0.1
INTL Capital S.A. b General Inspector of Justice [Member] [Domain]	'
Net Capital under Commodity Exchange Act Computation	6.1
Required Net Capital under Commodity Exchange Act	5.9
INTL Capital S.A. b Superintendence of Securities Markets of Buenos Aires [Member] [Domain]	'
Net Capital under Commodity Exchange Act Computation	4.6
Required Net Capital under Commodity Exchange Act	$0.20

StockBased_Compensation_Stockb

Stock-Based Compensation - Stock-based Compensation Expense (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Stock-Based Compensation [Abstract]	'	'	'	'
Allocated Share-based Compensation Expense	$1.10	$2	$2.20	$3.60

StockBased_Compensation_Stock_

Stock-Based Compensation - Stock Option Plan (Details)	Mar. 31, 2014	Sep. 30, 2013
Stock-Based Compensation [Abstract]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,000,000	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	913,500	1,000,000

StockBased_Compensation_Stock_1

Stock-Based Compensation - Stock Option Plan Fair Value Weighted-Average Assumptions (Details)	6 Months Ended
	Mar. 31, 2014
Stock-Based Compensation [Abstract]	'
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	34.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	'2 years 321 days

StockBased_Compensation_Stock_2

Stock-Based Compensation - Stock Based Compensation Table (Details) (USD $)	6 Months Ended		12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,000,000	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,779,983	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	-86,500	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Period Increase (Decrease)	86,500	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	-140,992	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	0	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Other Increases (Decreases) in Period	-80,000	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period, Net	0	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	-32,647	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	913,500	'	1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,612,844	'	1,779,983
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	665,031	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$24.27	'	$24.76
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$19.24	'	'
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$8.84	'	'
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	$25.91	'	'
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	$50.64	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$26.30	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value	$11.55	'	$11.44
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$4.48	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Excrecises in Period, Weighted Average Grant Date Fair Value	$4.02	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeited in Period, Weighted Average Grant Date Fair Value	$13.63	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expired in Period, Weighted Average Grant Date Fair Value	$14.27	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Excercisable, Weighted Average Grant Date Fair Value	$10.73	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	'4 years 7 months 6 days	'	'4 years 10 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	'1 year 7 months 6 days	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$2.40	'	$4.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	2.3	'	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Stock Options	8.6	'	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'5 years 8 months 16 days	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	$1.70	$1.70	'

StockBased_Compensation_Restri

Stock-Based Compensation - Restricted Stock Plan (Details)	6 Months Ended	12 Months Ended
	Mar. 31, 2014	Sep. 30, 2013
Stock-Based Compensation [Abstract]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,110,008	1,154,862

StockBased_Compensation_Restri1

Stock-Based Compensation - Restricted Stock Plan Table (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,110,008	1,154,862
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	363,638	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease)	-75,699	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	75,699	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	-134,646	'
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,110,008	1,154,862
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	250,210	363,638
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	30,845	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	-54,481	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$20.20	$20.53
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$19.69	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$20.20	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$21.68	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms	'2 years 1 month 10 days	'1 year 8 months 27 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value	$4,700,000	$7,400,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$3.80	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition - Restricted Stock	'2 years 1 month 10 days	'

Other_Expenses_Other_Expenses_

Other Expenses - Other Expenses Breakout (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Other Expenses [Abstract]	'	'	'	'
Accretion Expense	$0.10	$0.50	$0.30	$1.20
General Insurance Expense	0.4	0.4	0.8	0.9
Advertising Expense	1.3	0.5	1.8	1.1
Technology Services Costs	0.8	0.9	1.5	1.5
Supplies and Postage Expense	0.3	0.3	0.5	0.7
Clearance Fees	0.2	0.5	0.6	0.9
Taxes, Miscellaneous	0.9	1.2	2	2.2
Other Expenses	1.3	1.6	2.5	4.1
Other Cost and Expense, Operating	$5.30	$5.90	$10	$12.60

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) Rollforward (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Accumulated other comprehensive loss, net	($10.10)	'	($10.10)	'	($6.40)
Other comprehensive loss	-2.8	0	-3.7	-6.4	'
Accumulated Translation Adjustment [Member]	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Accumulated other comprehensive loss, net	-8	'	-8	'	-4.1
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	'	'	-3.9	'	'
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	'	'	0	'	'
Other comprehensive loss	'	'	-3.9	'	'
Accumulated Defined Benefit Plans Adjustment [Member]	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Accumulated other comprehensive loss, net	-2.6	'	-2.6	'	-2.8
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	'	'	0.2	'	'
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	'	'	0	'	'
Other comprehensive loss	'	'	0.2	'	'
Accumulated Net Unrealized Investment Gain (Loss) [Member]	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Accumulated other comprehensive loss, net	0.5	'	0.5	'	0.5
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	'	'	0	'	'
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	'	'	0	'	'
Other comprehensive loss	'	'	0	'	'
Accumulated Other Comprehensive Loss [Member]	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Accumulated other comprehensive loss, net	-10.1	'	-10.1	'	-6.4
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	'	'	-3.7	'	'
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	'	'	0	'	'
Other comprehensive loss	'	'	($3.70)	'	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Income Taxes [Abstract]	'	'	'	'	'	'	'
Deferred Tax Assets, Valuation Allowance	$2.30	'	$2.30	'	$0	'	'
Valuation Allowance, Deferred Tax Asset, Change in Amount	'	'	'	'	1.8	'	'
Income (Loss) from Continuing Operations before Income Taxes, Domestic	'	'	'	'	-22.2	-21.2	22.7
Deferred Tax Liabilities, Gross	4.3	'	4.3	'	'	'	'
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	1.3	'	1.3	'	'	'	'
Income Tax Expense (Benefit)	2.6	0	4.1	3.9	'	'	'
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	25.00%	0.00%	29.00%	25.00%	'	'	'
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	'	0.4	'	'	'	'	'
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$0.30	'	$0.30	'	'	'	'

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Discontinued Operations [Abstract]	'	'	'	'
Disposal Group, Including Discontinued Operation, Revenue	$11.60	$419.20	$40.90	$834.50
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	11.4	416.8	40.2	824.8
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)	0.2	2.4	0.7	9.7
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	-0.2	-0.2	-0.1	4.5
Discontinued Operation, Tax Effect of Discontinued Operation	0	0	0	-1.5
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	($0.20)	($0.20)	($0.10)	$3

Segment_Analysis_Reportable_Se

Segment Analysis - Reportable Segments (Details)	6 Months Ended
	Mar. 31, 2014
Segment Analysis [Abstract]	'
Number of different types of foreign currencies	150

Segment_Analysis_Details

Segment Analysis (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	$8,452.90	$11,769.30	$16,361.60	$23,906.80	'
Gross Profit	129.2	114.9	242.1	233.3	'
Net operating revenues	85.9	75.1	159.3	158.4	'
Net Contribution	65.9	55.6	123.1	114	'
Net Segment Income	36.5	26	65.9	55.3	'
Costs not allocated	26.2	24.3	51.7	39.6	'
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	10.3	1.7	14.2	15.7	'
Assets	3,015.10	'	3,015.10	'	2,848
Commercial Hedging [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	63.8	51.7	109.4	101.2	'
Gross Profit	63.8	51.7	109.4	101.2	'
Net operating revenues	52.6	41.5	88.8	82.4	'
Net Contribution	38.3	29.5	65.1	61	'
Net Segment Income	22.6	13.4	34.7	29.4	'
Assets	1,330.40	'	1,330.40	'	1,005.10
Global Payments [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	12.8	9.3	26.4	19.4	'
Gross Profit	12.8	9.3	26.4	19.4	'
Net operating revenues	11	8	22.8	17.3	'
Net Contribution	8.6	6.2	17.8	13.1	'
Net Segment Income	6.3	4.6	13.3	9.6	'
Assets	44	'	44	'	57.2
Securities Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	17.2	18	38.6	32.7	'
Gross Profit	17.2	18	38.6	32.7	'
Net operating revenues	11.8	13.3	27.4	24	'
Net Contribution	8.9	10.6	20.8	18.9	'
Net Segment Income	3.8	5.4	11	9.6	'
Assets	207.2	'	207.2	'	204.2
Physical Commodities [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	8,328.80	11,660	16,129.80	23,687.30	'
Gross Profit	5.1	5.6	10.3	13.8	'
Net operating revenues	4.2	4.6	8.7	11.7	'
Net Contribution	3.6	3	7.2	8.8	'
Net Segment Income	1.7	0.9	3.5	5	'
Assets	167.5	'	167.5	'	132.5
Clearing and Execution Services Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	30.9	30.8	58.4	58	'
Gross Profit	30.9	30.8	58.4	58	'
Net operating revenues	8.4	8.2	15.5	15.5	'
Net Contribution	6.5	6.3	12.2	12.2	'
Net Segment Income	2.1	1.7	3.4	1.7	'
Assets	1,150.70	'	1,150.70	'	1,333.30
Corporate [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Revenues	-0.6	-0.5	-1	8.2	'
Gross Profit	-0.6	-0.5	-1	8.2	'
Net operating revenues	-2.1	-0.5	-3.9	7.5	'
Assets	$115.30	'	$115.30	'	$115.70