StoneX (SNEX) 10-Q 10 May 17 2017 Q2 Quarterly report Financial data

DEI

DEI - shares	6 Months Ended
	Mar. 31, 2017	May 08, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	INTL FCSTONE INC.
Trading Symbol	INTL
Entity Central Index Key	913,760
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		18,677,176
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
ASSETS
Cash and cash equivalents	$ 296.3	$ 316.2
Cash, securities and other assets segregated under federal and other regulations (including $247.6 and $618.8 at fair value at March 31, 2017 and September 30, 2016, respectively)	1,085.5	1,136.3
Securities purchased under agreements to resell	738.8	609.6
Securities Borrowed	73.6	0
Deposits with and receivables from:
Exchange-clearing organizations (including $636.5 and $868.5 at fair value at March 31, 2017 and September 30, 2016, respectively)	1,679.4	1,524.4
Broker-dealers, clearing organizations and counterparties (including $34.7 and $(15.2) at fair value at March 31, 2017 and September 30, 2016, respectively)	170.3	237
Receivables from customers, net	204	194.5
Notes receivable, net	11	18.9
Income taxes receivable	0.8	1.1
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $324.6 and $47.2 at March 31, 2017 and September 30, 2016, respectively)	1,906.7	1,606.1
Physical commodities inventory, net (including $117.8 and $71.2 at fair value at March 31, 2017 and September 30, 2016, respectively)	181.7	123.8
Deferred income taxes, net	38.1	34.5
Property and equipment, net	32.4	29.4
Goodwill and intangible assets, net	61.2	56.6
Other assets	48.8	61.9
Total assets	6,528.6	5,950.3
Liabilities:
Accounts payable and other accrued liabilities (including $0.9 and $0.8 at fair value at March 31, 2017 and September 30, 2016, respectively)	147.4	161.3
Payables to:
Customers	2,855.5	2,854.2
Broker-dealers, clearing organizations and counterparties (including $9.8 and $3.5 at fair value at March 31, 2017 and September 30, 2016), respectively	178.2	260.1
Lenders under loans	263.4	182.8
Senior unsecured notes	0	44.5
Income taxes payable	7.9	7.1
Payables under repurchase agreements	1,431.9	1,167.1
Securities Loaned	107.4	0
Financial instruments sold, not yet purchased, at fair value	1,081.2	839.4
Total liabilities	6,072.9	5,516.5
Commitments and contingencies (Note 11)
Stockholders' Equity:
Preferred stock, $0.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding	0	0
Common stock, $0.01 par value. Authorized 30,000,000 shares; 20,781,686 issued and 18,659,729 outstanding at March 31, 2017 and 20,557,175 issued and 18,435,218 outstanding at September 30, 2016	0.2	0.2
Common stock in treasury, at cost - 2,121,957 shares at March 31, 2017 and September 30, 2016	(46.3)	(46.3)
Additional paid-in capital	254.2	249.4
Retained earnings	272.4	255.1
Accumulated other comprehensive loss, net	(24.8)	(24.6)
Total stockholders' equity	455.7	433.8
Total liabilities and stockholders' equity	$ 6,528.6	$ 5,950.3

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets Parentheticals - USD ($) $ in Millions	Dec. 31, 2016	Sep. 30, 2016
Balance Sheet Parentheticals [Abstract]
Securities and other assets segregated, fair value	$ 247.6	$ 618.8
Dep and rec -exch clear org - fair value	636.5	868.5
Dep and rec -b/d - fair value	34.7	(15.2)
Physical commodities inventory at fair value	117.8	71.2
Collateral that can be sold or repledged	324.6	47.2
Accounts pay and other accrued - fair value	0.9	0.8
Payables to b/d - fair value	$ 9.8	$ 3.5
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	20,781,686	20,557,175
Common stock - outstanding	18,659,729	18,435,218
Treasury stock - shares	2,121,957	2,121,957

Condensed Consolidated Income S

Condensed Consolidated Income Statements - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Sales of physical commodities	$ 5,273.3	$ 3,548	$ 11,169.3	$ 6,800.6
Trading gains, net	84	80.7	167	160.4
Commission and clearing fees	70.3	52.1	139.5	101.2
Consulting and management fees	15.5	9.6	31.2	19.3
Interest income	17.7	18.5	28.1	27.2
Other income	0	0	0.1	0.1
Total revenues	5,460.8	3,708.9	11,535.2	7,108.8
Cost of sales of physical commodities	5,265	3,542.8	11,153.9	6,791.4
Operating revenues	195.8	166.1	381.3	317.4
Transaction-based clearing expenses	33.7	32.9	67.3	62.7
Introducing broker commissions	28.2	13.2	56.9	26
Interest expense	10	7.1	18.9	13.1
Net operating revenues	123.9	112.9	238.2	215.6
Compensation and other expenses:
Compensation and benefits	76.6	65.2	147.2	128.3
Communication and data services	9.7	7.3	19.8	15.2
Occupancy and equipment rental	3.8	3.2	7.2	6.5
Professional fees	3.4	2.7	8.2	5.6
Travel and business development	3	2.3	6.6	5.5
Depreciation and amortization	2.4	2.2	4.8	4.1
Bad debts	1.3	2.6	3.8	4.6
Other	9.4	7.4	17.9	13.7
Total compensation and other expenses	109.6	92.9	215.5	183.5
Income before tax	14.3	20	22.7	32.1
Income tax expense	3.3	5.5	5.4	8.8
Net income	$ 11	$ 14.5	$ 17.3	$ 23.3
Earnings per share:
Basic	$ 0.58	$ 0.77	$ 0.92	$ 1.24
Diluted	$ 0.58	$ 0.76	$ 0.92	$ 1.22
Weighted-average number of common shares outstanding:
Basic	18,404,236	18,592,643	18,325,383	18,621,337
Diluted	18,661,418	18,755,450	18,637,480	18,821,822

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ 11	$ 14.5	$ 17.3	$ 23.3
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	0.7	(1.3)	(0.2)	(6.9)
Pension liabilities adjustment	0	0	0	(0.2)
Reclassification of adjustments included in net income [Abstract]
Periodic pension costs (included in compensation and benefits)	0	0	0	0.4
Reclassification adjustment for gains included in net income	0	0	0	0.4
Other comprehensive income (loss)	0.7	(1.3)	(0.2)	(6.7)
Comprehensive income	$ 11.7	$ 13.2	$ 17.1	$ 16.6

Condensed Consolidated Cash Flo

Condensed Consolidated Cash Flows Statements - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 17.3	$ 23.3
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	4.8	3.9
Bad debts	3.8	4.6
Deferred income taxes	(3.6)	(1.8)
Amortization of debt issuance costs and debt discount	1.4	0.5
Amortization of stock-based compensation	2.6	2.5
Loss on sale of property and equipment	0.3	(0.3)
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	47.4	(174.1)
Securities purchased under agreements to resell	(129.2)	(377)
Increase (Decrease) in Securities Borrowed	(66.7)	0
Deposits and receivables from exchange-clearing organizations	(158.4)	111.7
Deposits and receivables from broker-dealers, clearing organizations, and counterparties	32.1	128.5
Receivables from customers, net	(2.5)	108.8
Notes receivable, net	7.9	12.7
Income taxes receivable	0	0.5
Financial instruments owned, at fair value	(304.8)	(454.5)
Physical commodities inventory	(58.2)	1.6
Other assets	7.8	(4.8)
Accounts payable and other accrued liabilities	(8.8)	(25.6)
Payables to customers	27.8	(144.6)
Payables to broker-dealers, clearing organizations and counterparties	(64.3)	62.3
Income taxes payable	0.9	(0.1)
Payables under repurchase agreements	264.8	108.3
Increase (Decrease) in Securities Loaned Transactions	89.9	0
Financial instruments sold, not yet purchased, at fair value	243.7	465.7
Net cash (used in) provided by operating activities	(44.6)	(147.3)
Cash flows from investing activities:
Cash paid for acquisitions, net	6	0
Purchase of property and equipment	6.1	8
Net cash used in investing activities	(12.1)	(8)
Cash flows from financing activities:
Net change in payable to lenders under loans	81	110.3
Repayments of Unsecured Debt	(45.5)	0
Payments of note payable	0.4	0.4
Deferred payments on acquisitions	0	2.7
Debt issuance costs	0.1	1.9
Exercise of stock options	2.5	1.7
Share repurchases	0	10.3
Excess income tax benefit on stock options and awards	(0.2)	0.7
Net cash provided by financing activities	37.3	97.4
Effect of exchange rates on cash and cash equivalents	(0.5)	(7)
Net (decrease) increase in cash and cash equivalents	(19.9)	(64.9)
Cash and cash equivalents at beginning of period	316.2	268.1
Cash and cash equivalents at end of period	296.3	203.2
Supplemental disclosure of cash flow information:
Cash paid for interest	17.1	11.8
Income taxes paid, net of cash refunds	8.1	9.2
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	6	0
Additional consideration payable related to acquisitions, net	$ 0	$ 0.3

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Stockholders' Equity - 6 months ended Mar. 31, 2017 - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances as of beginning of period at Sep. 30, 2016	$ 433.8	$ 0.2	$ (46.3)	$ 249.4	$ 255.1	$ (24.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17.3				17.3
Other comprehensive loss	(0.2)					(0.2)
Exercise of stock options	2.2			2.2
Share-based Compensation	2.6			2.6
Balances as of end of period at Mar. 31, 2017	$ 455.7	$ 0.2	$ (46.3)	$ 254.2	$ 272.4	$ (24.8)

Basis of Presentation and Conso

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Notes)	6 Months Ended
	Mar. 31, 2017
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”), is a diversified global financial services organization providing execution, risk management and advisory services, market intelligence, and clearing services across assets classes and markets around the world. The Company’s services include comprehensive risk management advisory services for commercial customers; execution of listed futures and options on futures contracts on all major commodity exchanges; structured over-the-counter (“OTC”) products in a wide range of commodities; physical trading and hedging of precious metals and select other commodities; trading of more than 140 foreign currencies; market-making in international equities; fixed income; debt origination and asset management. The Company provides these services to a diverse group of more than 20,000 predominantly wholesale organizations 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, 2016 , 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. 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, 2016 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 measurement 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. In the condensed consolidated income statements, the total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. The subtotal ‘operating revenues’ in the condensed consolidated income statements is calculated by deducting physical commodities cost of sales from total revenues. The subtotal ‘net operating revenues’ in the condensed consolidated income statements is calculated as operating revenues less transaction-based clearing expenses, introducing broker commissions and interest expense. Transaction-based clearing expenses represent variable expenses paid to executing brokers, exchanges, clearing organizations and banks in relation to transactional volumes. Introducing broker commissions include commission paid to non-employee third parties that have introduced customers to the Company. Net operating revenues represent revenues available to pay variable compensation to risk management consultants and traders and direct non-variable expenses, as well as variable and non-variable expenses of operational and administrative employees. During the quarter ended March 31, 2017, the Company’s Securities reportable segment established a stock lending business. Stock borrowed and stock loaned are accounted for as collateralized financings. Securities borrowed and securities loaned are recorded at the amount of cash collateral advanced or received. Stock borrowed and stock loaned is reported on a gross basis as the Company has determined that the right of offset does not exist. Interest income and interest expense are recognized over the life of the arrangements. Accounting Standards Adopted In April 2015, the FASB issued Accounting Standards Update (“ASU”) No. 2015-03, Interest – Imputation of Interest (Subtopic 835-30). ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. In June 2015, the FASB issued ASU 2015-15 as an amendment to this guidance to address the absence of authoritative guidance for debt issuance costs related to line-of-credit arrangements. The SEC staff stated that they would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. ASU 2015-03 required retrospective application to all prior periods presented in the financial statements. This new guidance was effective for the Company in the first quarter of 2017. As a result of adopting this standard on October 1, 2016, deferred financing costs of $1.0 million as of September 30, 2016, previously reported within other assets, were reclassified to senior unsecured notes in the consolidated balance sheets. As of December 31, 2016, there were no deferred financing costs as the senior unsecured notes were redeemed during the three months ended December 31, 2016, as discussed in Note 9. In January 2017, the FASB issued ASU 2017-01, Business Combinations - Clarifying the Definition of a Business, which clarifies the definition of a business for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This ASU is effective for public business entities for annual and interim periods in fiscal years beginning after December 15, 2017. The adoption of this standard should be applied prospectively on or after the effective date. Early adoption is permitted for transactions for which the acquisition date occurs before the issuance date or effective date of the amendments and only when the transaction has not been reported in financial statements that have been issued or made available for issuance. The Company has early adopted this guidance effective October 1, 2016, and applied the guidance in determining whether the acquisition discussed in Note 16 is the acquisition of an asset or of a business.

Earnings per Share (Notes)

Earnings per Share (Notes)	6 Months Ended
	Mar. 31, 2017
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 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) 2017 2016 2017 2016 Numerator: Net income $ 11.0 $ 14.5 $ 17.3 $ 23.3 Less: Allocation to participating securities (0.2 ) (0.3 ) (0.3 ) (0.4 ) Net income allocated to common stockholders $ 10.8 $ 14.2 $ 17.0 $ 22.9 Denominator: Weighted average number of: Common shares outstanding 18,404,236 18,592,643 18,325,383 18,621,337 Dilutive potential common shares outstanding: Share-based awards 257,182 162,807 312,097 200,485 Diluted weighted-average shares 18,661,418 18,755,450 18,637,480 18,821,822 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 ASC. Options to purchase 322,974 and 986,339 shares of common stock for the three months ended March 31, 2017 and 2016 , respectively, and options to purchase 242,448 and 900,665 shares of common stock for the six months ended March 31, 2017 and 2016 , respectively, were excluded from the calculation of diluted earnings per share as they would have been anti-dilutive.

Assets and Liabilities, at Fair

Assets and Liabilities, at Fair Value (Notes)	6 Months Ended
	Mar. 31, 2017
Assets and Liabilities, at Fair Value [Abstract]
Fair Value Disclosures [Text Block]	Assets and Liabilities, at Fair Value The Company’s financial and non-financial assets and liabilities reported at fair value, or at amortized cost which approximates 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 • Securities purchased under agreements to resell • Securities borrowed • Deposits with and receivables from exchange-clearing organizations, broker-dealers, clearing organizations and counterparties • Financial instruments owned and sold, not yet purchased • Physical commodities inventory • Accounts payable and other accrued liabilities • Payables to broker-dealers, clearing organizations and counterparties • Securities sold under agreements to repurchase • Securities loaned Fair Value Hierarchy The majority of financial assets and liabilities on the condensed 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, obligations issued by government sponsored entities, and commodities warehouse receipts. Deposits with and receivables from exchange-clearing organizations, broker-dealers, clearing organizations and counterparties and payables to 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, obligations issued by government sponsored entities, and mortgage-backed and asset-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 common and preferred stock and American Depository Receipts (“ADRs”), exchangeable foreign ordinary equities and ADRs, U.S. and foreign government obligations, corporate and municipal debt securities, derivative financial instruments, exchange stock, commodities warehouse receipts and leases, mutual funds and investments in managed funds. The fair value of exchange common stock is determined by quoted market prices. Physical commodities inventory includes precious metals that are a part of the trading activities of the regulated broker-dealer subsidiary and is recorded at fair value using spot prices. Physical commodities inventory also includes agricultural and energy commodities that are part of the trading activities of a non-broker dealer subsidiary and are also recorded at fair value using spot prices. The carrying value of securities purchased under agreements to resell, securities borrowed, receivables from customers, net, notes receivable, net, securities sold under agreements to repurchase, and securities loaned approximates fair value due to their short-term nature. Payables to lenders under loans carry variable rates of interest and thus approximate fair value. Deposits with and receivables from broker-dealers, clearing organizations and counterparties include amounts receivable for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled trades. Payables to broker-dealers, clearing organizations and counterparties primarily include amounts payable for securities purchased, but not yet received by the Company on settlement date (“fails-to-receive”), net payables arising from unsettled trades and bonds loaned transactions. Due to their short-term nature, deposits with and receivables from and payables to broker-dealers, clearing organizations and counterparties approximate fair value. The fair value estimates presented in the condensed consolidated financial statements are based on pertinent information available to management as of March 31, 2017 and September 30, 2016 . 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. Except as disclosed in Note 6 , the Company did not have any fair value adjustments for assets or liabilities measured at fair value on a non-recurring basis during the three and six months ended March 31, 2017 . The three levels of the fair value hierarchy under the Fair Value Measurement 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, 2017 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, 2017. March 31, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificate of deposits $ 3.4 $ — $ — $ — $ 3.4 Commodities warehouse receipts 21.9 — — — 21.9 U.S. government obligations — 225.7 — — 225.7 Securities and other assets segregated under federal and other regulations 21.9 225.7 — — 247.6 Money market funds 376.0 — — — 376.0 U.S. government obligations — 281.8 — — 281.8 Derivatives 1,799.0 — — (1,820.3 ) (21.3 ) Deposits with and receivables from exchange-clearing organizations 2,175.0 281.8 — (1,820.3 ) 636.5 "To be announced" (TBA) and forward settling securities — 6.2 — (0.9 ) 5.3 Derivatives — 89.2 — (59.8 ) 29.4 Deposits with and receivables from broker-dealers, clearing organizations and counterparties — 95.4 — (60.7 ) 34.7 Common and preferred stock and ADRs 28.5 2.0 0.2 — 30.7 Exchangeable foreign ordinary equities and ADRs 31.3 0.4 — — 31.7 Corporate and municipal bonds 4.9 1.3 — — 6.2 U.S. government obligations — 625.4 — — 625.4 Foreign government obligations — 49.4 — — 49.4 Mortgage-backed securities — 926.6 — — 926.6 Derivatives 266.4 1,419.0 — (1,487.0 ) 198.4 Commodities leases — 117.2 — (100.0 ) 17.2 Commodities warehouse receipts 8.0 — — — 8.0 Exchange firm common stock 7.1 — — — 7.1 Mutual funds and other 6.0 — — — 6.0 Financial instruments owned 352.2 3,141.3 0.2 (1,587.0 ) 1,906.7 Physical commodities inventory 117.8 — — — 117.8 Total assets at fair value $ 2,670.3 $ 3,744.2 $ 0.2 $ (3,468.0 ) $ 2,946.7 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 0.9 $ — $ 0.9 TBA and forward settling securities — 10.8 — (0.9 ) 9.9 Derivatives 1,560.8 103.0 — (1,663.9 ) (0.1 ) Payable to broker-dealers, clearing organizations and counterparties 1,560.8 113.8 — (1,664.8 ) 9.8 Common and preferred stock and ADRs 45.4 0.5 — — 45.9 Exchangeable foreign ordinary equities and ADRs 31.6 0.3 — — 31.9 Corporate and municipal bonds 1.2 — — — 1.2 U.S. government obligations — 699.9 — — 699.9 Foreign government obligations — 10.1 — — 10.1 Mortgage-backed securities — 4.7 — — 4.7 Derivatives 261.0 1,575.9 — (1,607.3 ) 229.6 Commodities leases — 164.8 — (106.9 ) 57.9 Financial instruments sold, not yet purchased 339.2 2,456.2 — (1,714.2 ) 1,081.2 Total liabilities at fair value $ 1,900.0 $ 2,570.0 $ 0.9 $ (3,379.0 ) $ 1,091.9 (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. The following table sets forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2016 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 September 30, 2016. September 30, 2016 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificates of deposits $ 7.1 $ — $ — $ — $ 7.1 Commodities warehouse receipts 23.3 — — — 23.3 U.S. government obligations — 595.5 — — 595.5 Securities and other assets segregated under federal and other regulations 23.3 595.5 — — 618.8 Money market funds 512.7 — — — 512.7 U.S. government obligations — 472.1 — — 472.1 Derivatives 2,149.9 — — (2,266.2 ) (116.3 ) Deposits with and receivables from exchange-clearing organizations 2,662.6 472.1 — (2,266.2 ) 868.5 TBA and forward settling securities — 0.3 — — 0.3 Derivatives — 8.0 — (23.5 ) (15.5 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties — 8.3 — (23.5 ) (15.2 ) Common and preferred stock and ADRs 34.6 1.7 0.2 — 36.5 Exchangeable foreign ordinary equities and ADRs 25.2 0.5 — — 25.7 Corporate and municipal bonds 36.9 0.9 3.0 — 40.8 U.S. government obligations — 514.9 — — 514.9 Foreign government obligations — 14.6 — — 14.6 Mortgage-backed securities — 747.5 — — 747.5 Derivatives 206.9 1,350.8 — (1,363.8 ) 193.9 Commodities leases — 137.2 — (129.1 ) 8.1 Commodities warehouse receipts 8.9 — — — 8.9 Exchange firm common stock 6.4 — — — 6.4 Mutual funds and other 8.8 — — — 8.8 Financial instruments owned 327.7 2,768.1 3.2 (1,492.9 ) 1,606.1 Physical commodities inventory, net - precious metals 71.2 — — — 71.2 Total assets at fair value $ 3,091.9 $ 3,844.0 $ 3.2 $ (3,782.6 ) $ 3,156.5 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 0.8 $ — $ 0.8 TBA and forward settling securities — 2.6 — 0.9 3.5 Derivatives 1,961.7 97.5 — (2,059.2 ) — Payable to broker-dealers, clearing organizations and counterparties 1,961.7 100.1 — (2,058.3 ) 3.5 Common and preferred stock and ADRs 23.5 0.4 — — 23.9 Exchangeable foreign ordinary equities and ADRs 25.3 0.5 — — 25.8 U.S. government obligations — 509.8 — — 509.8 Corporate and municipal bonds 6.9 — — — 6.9 Derivatives 199.4 1,319.3 — (1,307.8 ) 210.9 Commodities leases — 207.8 — (145.7 ) 62.1 Financial instruments sold, not yet purchased 255.1 2,037.8 — (1,453.5 ) 839.4 Total liabilities at fair value $ 2,216.8 $ 2,137.9 $ 0.8 $ (3,511.8 ) $ 843.7 (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. Realized and unrealized gains and losses are included in ‘trading gains, net’ and ‘interest income’ 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, 2017 and September 30, 2016 are summarized below: (in millions) March 31, 2017 September 30, 2016 Total level 3 assets $ 0.2 $ 3.2 Level 3 assets for which the Company bears economic exposure $ 0.2 $ 3.2 Total assets $ 6,528.6 $ 5,950.3 Total assets at fair value $ 2,946.7 $ 3,156.5 Total level 3 assets as a percentage of total assets — % 0.1 % Level 3 assets for which the Company bears economic exposure as a percentage of total assets — % 0.1 % Total level 3 assets as a percentage of total financial assets at fair value — % 0.1 % 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, 2017 and 2016 , 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, 2017 . Level 3 Financial Assets and Financial Liabilities For the Three Months Ended March 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.2 $ — $ — $ — $ — $ — $ 0.2 Corporate and municipal bonds — — — — — — — $ 0.2 $ — $ — $ — $ — $ — $ 0.2 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 0.8 $ — $ 0.1 $ — $ — $ — $ 0.9 Level 3 Financial Assets and Financial Liabilities For the Six Months Ended March 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.2 $ — $ — $ — $ — $ — $ 0.2 Corporate and municipal bonds 3.0 — — — (3.0 ) — — $ 3.2 $ — $ — $ — $ (3.0 ) $ — $ 0.2 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 0.8 $ — $ 0.1 $ — $ — $ — $ 0.9 Level 3 Financial Assets and Financial Liabilities For the Three Months Ended March 31, 2016 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.3 $ — $ — $ — $ — $ — $ 0.3 Corporate and municipal bonds 3.2 — 0.1 — — — 3.3 $ 3.5 $ — $ 0.1 $ — $ — $ — $ 3.6 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 3.5 $ — $ 0.1 $ — $ (2.1 ) $ — $ 1.5 Level 3 Financial Assets and Financial Liabilities For the Six Months Ended March 31, 2016 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.5 $ — $ (0.2 ) $ — $ — $ — $ 0.3 Corporate and municipal bonds 3.2 — 0.1 — — — 3.3 $ 3.7 $ — $ (0.1 ) $ — $ — $ — $ 3.6 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 3.3 $ — $ 0.3 $ — $ (2.1 ) $ — $ 1.5 The Company had debentures issued by a single asset owning company of Suriwongse Hotel located in Chiang Mai, Thailand. As of September 30, 2016, the Company’s investment in the hotel was $3.0 million , and was included within the corporate and municipal bonds classification in the level 3 financial assets and financial liabilities tables. In December 2016, the Company sold the debentures and collected an amount approximating their carrying value. 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 earn-out 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 earn-out 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 earn-outs 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 interest rate environment. From the dates of acquisition to March 31, 2017 , 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 by less than $0.1 million and $0.1 million during the three months ended March 31, 2017 and 2016 and by less than $0.1 million and $0.3 million during the six months ended March 31, 2017 and 2016 , respectively, with the corresponding amount classified as ‘other’ 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 in and out of levels 1, 2, and 3 during the three and six months ended March 31, 2017 and 2016 .

Financial Instruments with Off-

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Notes)	6 Months Ended
	Mar. 31, 2017
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, 2017 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, 2017 . The total financial instruments sold, not yet purchased of $1,081.2 million as of March 31, 2017 includes $229.6 million for derivative contracts, which represents a liability to the Company based on their fair values as of March 31, 2017 . Derivatives The Company utilizes derivative products in its trading capacity as a dealer in order to satisfy customer 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 condensed consolidated balance sheets in ‘deposits with and receivables from exchange-clearing organizations’, ‘financial instruments owned, at fair value’, ‘financial instruments sold, not yet purchased, at fair value’ and payables to broker-dealers, clearing organizations and counterparties’. The Company employs an interest rate risk management strategy using derivative financial instruments in the form of interest rate swaps as well as outright purchases of medium-term U.S. Treasury notes to manage a portion of the aggregate interest rate position. The Company’s objective when using interest rate swaps under the strategy, is to invest certain amounts of customer deposits in high quality, short-term investments and swap the resulting variable interest earnings into medium-term interest earnings. When used, the risk mitigation of these interest rate swaps are not within the documented hedging designation requirements of the Derivatives and Hedging Topic of the ASC, and as a result are recorded at fair value, with changes in the fair value of the interest rate swaps recorded within 'trading gains, net' in the condensed consolidated income statements. At September 30, 2016 , the Company had $375.0 million in notional principal of interest rate swaps outstanding with a weighted-average remaining life of 15 months. During the six months ended March 31, 2017 , the Company settled these interest rate swaps in advance of their original maturity date. Listed below are the fair values of the Company’s derivative assets and liabilities as of March 31, 2017 and September 30, 2016 . Assets represent net unrealized gains and liabilities represent net unrealized losses. March 31, 2017 September 30, 2016 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,617.7 $ 1,496.9 $ 2,022.1 $ 1,920.5 OTC commodity derivatives 1,336.7 1,518.4 1,217.0 1,188.9 Exchange-traded foreign exchange derivatives 22.6 21.0 12.2 7.5 OTC foreign exchange derivatives 434.8 317.8 346.5 290.2 Exchange-traded interest rate derivatives 132.9 113.9 78.7 120.5 Equity index derivatives 28.9 32.7 39.1 50.3 TBA and forward settling securities 6.2 10.8 0.3 2.6 Gross fair value of derivative contracts 3,579.8 3,511.5 3,715.9 3,580.5 Impact of netting and collateral (3,368.0 ) (3,272.1 ) (3,653.5 ) (3,366.1 ) Total fair value included in ‘Deposits with and receivables from exchange-clearing organizations’ $ (21.3 ) $ (116.3 ) Total fair value included in ‘Deposits with and receivables from broker-dealers, clearing organizations and counterparties’ $ 34.7 $ (15.2 ) Total fair value included in ‘Financial instruments owned, at fair value’ $ 198.4 $ 193.9 Total fair value included in ‘Payables to broker-dealers, clearing organizations and counterparties $ 9.8 $ 3.5 Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’ $ 229.6 $ 210.9 (1) As of March 31, 2017 and September 30, 2016 , the Company’s derivative contract volume for open positions were approximately 4.1 million and 4.0 million contracts, respectively. The Company’s derivative contracts are principally held in its Commercial Hedging and Clearing and Execution Services segments. 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 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 Company has derivative instruments, which consist of mortgage-backed TBA securities and forward settling transactions that are used to manage risk exposures in the trading inventory of the Company’s domestic fixed income institutional business. The fair value on these transactions are recorded in receivables or payables to broker-dealers, clearing organizations and counterparties. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘trading gains, net’. The Company enters into TBA securities transactions for the sole purpose of managing risk associated with the purchase of mortgage pass-through securities. TBA securities are included within deposits with and receivables from and payables to broker-dealers, clearing organizations and counterparties. Forward settling securities represent non-regular way securities and are included in financial instruments owned and sold. As of March 31, 2017 and September 30, 2016 , these transactions are summarized as follows: March 31, 2017 September 30, 2016 (in millions) Gain / (Loss) Notional Amounts Gain / (Loss) Notional Amounts Unrealized gain on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 3.2 $ 795.7 $ 0.8 $ 289.8 Unrealized loss on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (0.4 ) $ 180.4 $ (0.8 ) $ 485.5 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 0.6 $ (351.4 ) $ 1.3 $ (702.3 ) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (9.6 ) $ (1,537.9 ) $ (1.7 ) $ (754.3 ) Unrealized gain on forward settling securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 2.5 $ 595.5 $ 0.1 $ 607.9 Unrealized (loss) gain on forward settling securities sold within receivables from and payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.9 ) $ (301.4 ) $ 0.2 $ (470.4 ) (1) The notional amounts of these instruments reflect the extent of the Company's involvement in TBA and forward settling securities and do not represent risk of loss due to counterparty non-performance. The following table sets forth the Company’s gains (losses) related to derivative financial instruments for the three and six months ended March 31, 2017 and 2016 in accordance with the Derivatives and Hedging Topic of the ASC. The gains set forth below are included in ‘trading gains, net’ in the condensed consolidated income statements. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2017 2016 2017 2016 Commodities $ 13.9 $ 5.0 $ 18.8 $ 25.0 Foreign exchange 0.8 1.8 2.0 3.6 Interest rate — 2.9 (1.0 ) 1.0 TBA and forward settling securities (4.9 ) (5.7 ) 8.5 (5.0 ) Net gains from derivative contracts $ 9.8 $ 4.0 $ 28.3 $ 24.6 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 and/or position 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 result of 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, 2017 and September 30, 2016 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, 2017
Receivables from customers and notes receivable, net [Abstract]
Financing Receivables [Text Block]	Receivables From Customers, Net and Notes Receivable, Net The allowance for doubtful accounts related to receivables from customers was $10.8 million as of March 31, 2017 and $9.5 million as of September 30, 2016 . The allowance for doubtful accounts related to notes receivable was $0.0 million and $ 0.2 million as of March 31, 2017 and September 30, 2016 , respectively. During the three months ended March 31, 2017 , the Company recorded bad debt expense of $1.3 million , primarily related to LME Metals customer deficits in the Company’s Commercial Hedging segment. During the three months ended March 31, 2016, the Company recorded bad debt expense of $2.6 million , including provision increases for bad debts primarily related to $1.3 million of customer receivables in the Physical Ag & Energy component of the Physical Commodities segment, $1.1 million of customer deficits in the Commercial Hedging segment and $0.2 million related to short-term notes receivable origination in the Securities segment. During the six months ended March 31, 2017 , the Company recorded bad debt expense of $3.8 million , primarily related to LME Metals customer deficits in the Company’s Commercial Hedging segment. During the six months ended March 31, 2016, the Company recorded bad debt expense of $4.6 million , primarily related to $1.5 million of customer receivables in the Physical Ag & Energy component of the Physical Commodities segment, $2.7 million of customer deficits in the Commercial Hedging segment and $0.3 million related to short-term notes receivable origination in the Securities segment. The Company originates short-term notes receivable from customers with the outstanding balances typically being insured 90% to 98% by a third party, including accrued interest, subject to applicable deductible amounts. The total balance outstanding under insured notes receivable was $2.1 million and $5.0 million as of March 31, 2017 and September 30, 2016 , respectively. The Company has sold $2.1 million and $4.6 million of the insured portion of the notes through non-recourse participation agreements with other third parties as of March 31, 2017 and September 30, 2016 , respectively. The Company completed its exit of the majority of this activity during fiscal 2016. The Company believes the run-off of the remaining activity will have a minimal impact on the Company. 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, 2017
Physical Commodities Inventory [Abstract]
Inventory Disclosure [Text Block]	Physical Commodities Inventory The Company’s inventories consist of finished physical commodities. Inventories by component of the Company’s Physical Commodities segment are shown below. (in millions) March 31, September 30, Physical Ag & Energy (1) $ 139.5 $ 65.9 Precious metals - held by broker-dealer subsidiary (2) 17.0 5.3 Precious metals - held by non-broker-dealer subsidiaries (3) 25.2 52.6 Physical commodities inventory $ 181.7 $ 123.8 (1) Physical Ag & Energy maintains agricultural and energy commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, coal and others. The agricultural commodity inventories are carried at net realizable value, which approximates fair value less disposal costs, with changes in net realizable value included as a component of ‘cost of sales of physical commodities’ on the condensed consolidated income statements. The agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. (2) Precious metals held by the Company’s subsidiary, INTL FCStone Ltd, a United Kingdom based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘trading gains, net’ on the condensed consolidated income statements, in accordance with U.S. GAAP accounting requirements for broker-dealers. (3) Precious metals inventory held by subsidiaries that are not broker-dealers are valued at the lower of cost or market value. The Company has recorded lower of cost or market (“LCM”) adjustments for certain precious metals inventory of $0.1 million and $0.6 million as of March 31, 2017 and September 30, 2016 , 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, 2017
Goodwill [Abstract]
Goodwill Disclosure [Text Block]	Goodwill The carrying value of goodwill is allocated to the Company’s operating segments as follows: (in millions) March 31, September 30, Commercial Hedging $ 30.7 $ 30.7 Global Payments 6.3 6.3 Physical Commodities 2.4 2.4 Securities 8.1 8.1 Goodwill $ 47.5 $ 47.5

Intangible Assets - (Notes)

Intangible Assets - (Notes)	6 Months Ended
	Mar. 31, 2017
Intangible Assets [Abstract]
Intangible Assets Disclosure [Text Block]	Intangible Assets During the six months ended March 31, 2017 , the Company recorded additional intangible assets of $6.0 million as part of the ICAP acquisition. See Note 16 - Acquisitions for additional discussion. 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, 2017 September 30, 2016 (in millions) Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization Trade name $ 1.1 $ (0.8 ) $ 0.3 $ 1.1 $ (0.6 ) $ 0.5 Software programs/platforms 2.7 (2.4 ) 0.3 2.7 (2.4 ) 0.3 Customer base 20.0 (6.9 ) 13.1 14.0 (5.7 ) 8.3 Total intangible assets $ 23.8 $ (10.1 ) $ 13.7 $ 17.8 $ (8.7 ) $ 9.1 Amortization expense related to intangible assets was $1.4 million and $0.8 million for the six months ended March 31, 2017 and 2016 , respectively. As of March 31, 2017 , the estimated future amortization expense was as follows: (in millions) Fiscal 2017 (remaining six months) $ 1.4 Fiscal 2018 2.2 Fiscal 2019 2.2 Fiscal 2020 2.0 Fiscal 2021 and thereafter 5.9 $ 13.7

Credit Facilities (Notes)

Credit Facilities (Notes)	6 Months Ended
	Mar. 31, 2017
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 $447.0 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 committed credit facilities consist of the following: • $247 million facility available to INTL FCStone Inc. for general working capital requirements. • $75 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Financial Inc., for short-term funding of margin to commodity exchanges. The facility is subject to annual review and guaranteed by INTL FCStone Inc. • $100 million facility available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC, for financing traditional commodity financing arrangements and commodity repurchase agreements. The facility is subject to annual review and is guaranteed by INTL FCStone Inc. • $25 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Ltd, for short-term funding of margin to commodity exchanges. The facility is subject to annual review and is guaranteed by INTL FCStone Inc. The Company also has a secured, uncommitted loan facility, under which the Company’s wholly owned subsidiary, INTL FCStone Financial Inc. may borrow up to $50 million , collateralized by commodity warehouse receipts, to facilitate U.S. commodity exchange deliveries of its customers, subject to certain terms and conditions of the credit agreement. The Company also has a secured uncommitted loan facility under which the Company’s wholly owned subsidiary, INTL FCStone Ltd may borrow up to approximately $25 million , collateralized by commodity warehouse receipts, to facilitate financing of commodities under repurchase agreement services to its customers, subject to certain terms and conditions of the credit agreement. The Company also has a secured uncommitted loan facility under which the Company’s wholly owned subsidiary Sterne, Agee & Leach, Inc. may borrow for short term funding of firm and customer margin requirements, subject to certain terms and conditions of the agreement. The uncommitted maximum amount available to be borrowed is not specified, and all requests for borrowing are subject to the sole discretion of the lender. Sterne, Agee & Leach, Inc. also has a secured uncommitted loan facility under which it may borrow up to $100 million for short term funding of firm and customer margin requirements, subject to certain terms and conditions of the agreement. Note Payable to Bank The Company has a loan from a commercial bank, secured by equipment purchased with the proceeds. The note is payable in monthly installments, ending in March 2020. The note bears interest at a rate per annum equal to LIBOR plus 2.00%. Senior Unsecured Notes In July 2013, the Company completed an 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 were used for general corporate purposes. On September 15, 2016, the Company provided notice, through the trustee of the Notes, to the record holders of the Notes that the Company would redeem the outstanding $45.5 million aggregate principal amount of the Notes in full. On October 15, 2016, the Company redeemed the Notes at a price equal to 100% of the principal amount redeemed plus accrued and unpaid interest to, but not including, the redemption date of October 15, 2016. The following table sets forth a listing of credit facilities, the committed amounts as of March 31, 2017 on the facilities, and outstanding borrowings on the facilities as well as indebtedness on a promissory note and on senior notes as of March 31, 2017 and September 30, 2016 : (in millions) Credit Facilities Amounts Outstanding Borrower Security Renewal / Expiration Date Total Commitment March 31, September 30, INTL FCStone Inc. Pledged shares of certain subsidiaries March 18, 2019 $ 247.0 $ 175.0 $ 136.5 INTL FCStone Financial Inc. None April 5, 2018 75.0 — — INTL FCStone Financial Inc. Commodity warehouse receipts n/a — — — FCStone Merchants Services, LLC Certain commodities assets May 1, 2018 100.0 86.0 43.5 INTL FCStone Ltd None October 27, 2017 25.0 — — INTL FCStone Ltd Commodity warehouse receipts n/a — — — Sterne, Agee & Leach, Inc. Certain pledged securities n/a — — — $ 447.0 261.0 180.0 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 2.4 2.8 Senior Unsecured Notes 8.50% senior notes, due July 30, 2020 (redeemed on October 15, 2016) — 44.5 Total indebtedness $ 263.4 $ 227.3 As reflected above, $200 million of the Company’s committed credit facilities are scheduled to expire within twelve months of this filing. The Company intends to renew or replace this facility when it expires, 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, 2017 , the Company was in compliance with all of its financial covenants under its credit facilities.

Commodity and Other Repurchase

Commodity and Other Repurchase Agreements and Collateralized Transactions (Notes)	6 Months Ended
	Mar. 31, 2017
Commodity and Other Repurchase Agreements [Abstract]
Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block]	Commodity and Other Repurchase Agreements and Collateralized Transactions Commodity Repurchase Arrangements The Company’s outstanding notes receivable in connection with sale/repurchase agreements, whereby customers sell certain commodity inventory and agree to repurchase the commodity inventory at a future date at a fixed rate, as of March 31, 2017 and September 30, 2016 were $0.6 million and $1.5 million , respectively. Resale and Repurchase Agreements, Securities Lending and Borrowing Agreements, and Margin Securities The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed and securities loaned transactions to, among other things, finance financial instruments, acquire securities to cover short positions, acquire securities for settlement, and to accommodate counterparties’ needs. These agreements are recorded at their contractual amounts plus accrued interest. The related interest is recorded in the condensed consolidated income statements as interest income or interest expense, as applicable. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to adequately collateralize such agreements and transactions in accordance with general industry guidelines and practices. The value of the collateral is valued daily and the Company may require counterparties to deposit additional collateral or return collateral pledged, when appropriate. The carrying amounts of these agreements and transactions approximate fair value due to their short-term nature and the level of collateralization. The Company pledges financial instruments owned to collateralize repurchase agreements and securities loaned agreements. At March 31, 2017 , financial instruments owned of $324.6 million were pledged as collateral under repurchase agreements and securities loaned agreements. The counterparty has the right to repledge the collateral in connection with these transactions. These financial instruments owned have been pledged as collateral and have been parenthetically disclosed on the condensed consolidated balance sheet. In addition, as of March 31, 2017 , the Company pledged financial instruments owned of $1,160.0 million and securities received under reverse repurchase agreements of which $86.8 million is used to cover collateral for tri-party repurchase agreements. For these securities, the counterparty does not have the right to sell or repledge the collateral. At March 31, 2017 , the Company has accepted collateral that it is permitted by contract to sell or repledge. This collateral consists primarily of securities received in reverse repurchase agreements, securities borrowed agreements, and margin securities held on behalf of correspondent brokers. The fair value of such collateral at March 31, 2017 , was $957.7 million of which $654.5 million was used to cover securities sold short which are recorded in financial instruments sold, not yet purchased on the condensed consolidated balance sheet. In the normal course of business, this collateral is used by the Company to cover financial instruments sold, not yet purchased, to obtain financing in the form of repurchase agreements, and to meet counterparties’ needs under lending arrangements. At March 31, 2017 , substantially all of the above collateral had been delivered against financial instruments sold, not yet purchased or repledged by the Company to obtain financing.

Commitments and Contingencies (

Commitments and Contingencies (Notes)	6 Months Ended
	Mar. 31, 2017
Commitments and Contingencies [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Commitments and Contingencies Legal Proceedings From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the policy limits of the insurance. As of March 31, 2017 and September 30, 2016 , the condensed consolidated balance sheets include loss contingency accruals recorded prior to these periods then ended, which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, is not likely to be material to the Company’s earnings, financial position or liquidity. There have been no material changes to the legal actions and proceedings as compared to September 30, 2016. Contractual Commitments Contingent Liability - Acquisition Under the terms of the purchase agreement related to the acquisition listed below, the Company has an obligation 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 $0.9 million and $0.8 million are included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheets as of March 31, 2017 and September 30, 2016 . 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, 2017 and 2016 were increases of $0.1 million and $0.3 million , respectively, and are included in ‘other’ in the condensed consolidated income statements. The Company has a contingent liability relating to the January 2015 acquisition of G.X. Clarke, which may result in the payment of additional purchase price consideration. The contingent consideration in no event shall exceed $1.5 million . The estimated total purchase price, including contingent consideration, is $28.7 million as of March 31, 2017 , of which $0.9 million remains outstanding and is included in ‘accounts payable and other accrued liabilities’ in the condensed consolidated balance sheet. Self-Insurance The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. As of March 31, 2017 , the Company had $0.9 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 Re

Capital and Other Regulatory Requirements (Notes)	6 Months Ended
	Mar. 31, 2017
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, 2017 , as follows: (in millions) As of March 31, 2017 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. Securities and Exchange Commission ("SEC") and Commodity Futures Trading Commission ("CFTC") United States Net capital $ 146.7 $ 83.4 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,127.0 $ 2,075.6 INTL FCStone Financial Inc. CFTC United States Secured funds $ 145.5 $ 128.7 Sterne Agee Clearing Inc. SEC United States Net capital $ 1.3 $ 0.1 Sterne, Agee & Leach, Inc. SEC United States Net capital $ 28.0 $ 2.0 Sterne Agee Financial Services, Inc. SEC United States Net capital $ 5.9 $ 0.3 INTL FCStone Ltd (1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 159.6 $ 87.1 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 72.0 $ 69.4 INTL Netherlands BV (1) FCA United Kingdom Net capital $ 158.9 $ 87.1 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 9.6 $ 0.5 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 5.3 $ 0.2 INTL Gainvest S.A. CNV Argentina Net capital $ 0.8 $ 0.1 INTL Capital S.A. General Inspector of Justice (Argentina) Argentina Net capital $ 10.7 $ 9.2 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.5 $ 1.1 INTL CIBSA S.A. CNV Argentina Net capital $ 7.1 $ 0.6 (1) INTL Netherlands BV is a holding company that includes the ownership equity of INTL FCStone Ltd. The associated net capital amounts and minimum requirements should not be considered in aggregate. Sterne, Agee & Leach, Inc. is also subject to Rule 15c3-3 of the Securities Exchange Act of 1934, as amended (“Customer Protection Rule”) inclusive of computations for proprietary accounts of broker-dealers (“PABs”). As of March 31, 2017 , Sterne, Agee & Leach, Inc. had $7.8 million of cash in a Special Reserve Bank Account (“SRBA”) for the exclusive benefit of customers under the Customer Protection Rule pursuant to SEC Rule 15c3-3, Computation for Determination of Reserve Requirements . Also, as of March 31, 2017, Sterne, Agee & Leach, Inc. had $6.0 million of cash in a SRBA pursuant to SEC Rule 15c3-3, Computation for Determination of PAB Reserve Requirements. As of March 31, 2017 , the amount on deposit in both the customers and the PABs SRBA was less than the reserve requirement and additional funds were deposited subsequent to period-end. 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, 2017 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Notes)

Other Expenses (Notes)	6 Months Ended
	Mar. 31, 2017
Other Expenses [Abstract]
Other Expenses [Text Block]	Other Expenses Other expenses for the three and six months ended March 31, 2017 and 2016 consisted of the following: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2017 2016 2017 2016 Contingent consideration, net $ 0.1 $ 0.1 $ 0.1 $ 0.3 Insurance 0.8 0.3 1.3 0.7 Advertising, meetings and conferences 1.2 2.3 2.1 3.0 Non-trading hardware and software maintenance and software licensing 2.8 1.3 5.7 2.8 Office supplies and printing 0.5 0.3 1.1 0.6 Other clearing related expenses 0.3 0.3 0.7 0.5 Other non-income taxes 1.2 1.1 2.3 2.1 Other 2.5 1.7 4.6 3.7 Total other expenses $ 9.4 $ 7.4 $ 17.9 $ 13.7

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) (Notes)	6 Months Ended
	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive 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 and gains and losses on foreign currency translations. The following table summarizes the changes in accumulated other comprehensive loss for the six months ended March 31, 2017 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2016 $ (20.1 ) $ (4.5 ) $ (24.6 ) Other comprehensive loss, net of tax (0.2 ) — (0.2 ) Balances as of March 31, 2017 $ (20.3 ) $ (4.5 ) $ (24.8 )

Income Taxes (Notes)

Income Taxes (Notes)	6 Months Ended
	Mar. 31, 2017
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, 2017 and September 30, 2016 was $3.6 million . The valuation allowances as of March 31, 2017 and September 30, 2016 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 income (losses) for the fiscal years ended September 30, 2016, 2015, and 2014 of $(9.7) million , $16.5 million , and $(18.4) 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. When evaluating if U.S. federal, state, and local deferred tax assets are realizable, the Company considered deferred tax liabilities of $4.5 million that are scheduled to reverse from 2017 to 2019 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 11 years. Based on the tax planning strategies that are prudent and feasible, 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 estimates in future periods could result in adjustments to the valuation allowance. Income tax expense of $3.3 million and $5.5 million for the three months ended March 31, 2017 and 2016 and income tax expense of $5.4 million and $8.8 million for the six months ended March 31, 2017 and 2016 , respectively, reflect estimated federal, foreign and state taxes. For the three months ended March 31, 2017 and 2016 , the Company’s effective tax rate was 23% and 28% , respectively. For the six months ended March 31, 2017 and 2016 , the Company’s effective tax rate was 24% and 27% , respectively. The effective tax rate during both periods, after consideration for discrete items, was lower than the U.S. federal statutory rate primarily due to a higher mix of earnings taxed at lower rates in foreign jurisdictions. 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, 2016 with U.S. federal and state and local taxing authorities. In the U.K., the Company has open tax years ending September 30, 2015 to September 30, 2016. In Brazil, the Company has open tax years ranging from December 31, 2011 through December 31, 2016. In Argentina, the Company has open tax years ranging from September 30, 2009 to September 30, 2016.

Acquisitions Acquisitions (Note

Acquisitions Acquisitions (Notes)	6 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	Acquisitions ICAP’s EMEA Oils Broking Business In September 2016, the Company’s subsidiary, INTL FCStone Ltd (“IFL”), reached an agreement to acquire the London-based EMEA oils business of ICAP Plc. The acquisition was effective on October 1, 2016, after IFL received approval from the U.K. Competition and Markets Authority. The business included over 30 front office employees across the fuel, crude, middle distillates, futures and options desks with deep-rooted relationships with over 200 well known commercial and institutional customers throughout Europe, the Middle East and Africa. The terms of the agreement included cash consideration of $6.0 million paid directly to ICAP as well as incentive amounts payable to employees acquired based upon their continued employment. The cash consideration paid to ICAP was dependent upon the number of brokers who accepted IFL’s employment offer. The transaction was accounted for as an asset acquisition in accordance with FASB ASC 805-50 and FASB ASC 350. The cash consideration paid was allocated entirely to the intangible asset recognized related to the customer relationships acquired. The intangible asset was assigned to the Clearing and Execution Services segment and will be amortized over a useful life of 5 years .

Segment Analysis (Notes)

Segment Analysis (Notes)	6 Months Ended
	Mar. 31, 2017
Segment Analysis [Abstract]
Segment Reporting Disclosure [Text Block]	Segment Analysis The Company reports its operating segments based on services provided to customers. The Company’s business activities are managed as operating segments and organized into reportable segments as follows: • Commercial Hedging (includes components Financial Agricultural (Ag) & Energy and LME Metals) • Global Payments • Securities (includes components Equity Market-Making, Debt Trading, Investment Banking, and Asset Management) • Physical Commodities (includes components Precious Metals and Physical Ag & Energy) • Clearing and Execution Services (includes components Exchange-traded Futures & Options, FX Prime Brokerage, Correspondent Clearing, Independent Wealth Management and Derivative Voice Brokerage) The total revenues reported combine gross revenues for the physical commodities business for subsidiaries that are not broker-dealers and net revenues for all other businesses. In order to reflect the way that the Company’s management views the results, the table below also reflects 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. 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 for the reportable segments 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) 2017 2016 2017 2016 Total revenues: Commercial Hedging $ 62.7 $ 54.7 $ 120.2 $ 110.1 Global Payments 21.5 17.4 44.6 35.7 Securities 37.9 45.6 75.3 94.4 Physical Commodities 5,276.2 3,550.7 11,174.9 6,805.2 Clearing and Execution Services 64.2 33.3 127.8 63.1 Corporate unallocated (1.7 ) 7.2 (7.6 ) 0.3 Total $ 5,460.8 $ 3,708.9 $ 11,535.2 $ 7,108.8 Operating revenues (loss): Commercial Hedging $ 62.7 $ 54.7 $ 120.2 $ 110.1 Global Payments 21.5 17.4 44.6 35.7 Securities 37.9 45.6 75.3 94.4 Physical Commodities 11.2 7.9 21.0 13.8 Clearing and Execution Services 64.2 33.3 127.8 63.1 Corporate unallocated (1.7 ) 7.2 (7.6 ) 0.3 Total $ 195.8 $ 166.1 $ 381.3 $ 317.4 Net operating revenues (loss): Commercial Hedging $ 50.5 $ 43.6 $ 96.1 $ 87.9 Global Payments 19.1 15.5 39.7 31.8 Securities 24.1 31.8 49.2 67.8 Physical Commodities 9.0 6.8 17.1 11.5 Clearing and Execution Services 25.4 10.4 49.5 20.8 Corporate unallocated (4.2 ) 4.8 (13.4 ) (4.2 ) Total $ 123.9 $ 112.9 $ 238.2 $ 215.6 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable bonus compensation, introducing broker commissions and interest expense) Commercial Hedging $ 36.9 $ 30.5 $ 70.3 $ 62.2 Global Payments 15.3 12.4 31.7 25.4 Securities 18.9 25.0 38.7 54.5 Physical Commodities 6.5 5.3 12.3 8.7 Clearing and Execution Services 19.6 8.2 37.6 16.1 Total $ 97.2 $ 81.4 $ 190.6 $ 166.9 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 18.7 $ 13.8 $ 34.1 $ 28.8 Global Payments 11.7 9.3 24.9 19.3 Securities 11.7 18.2 24.6 40.1 Physical Commodities 3.9 1.9 6.9 2.9 Clearing and Execution Services 7.9 3.5 13.6 7.0 Total $ 53.9 $ 46.7 $ 104.1 $ 98.1 Reconciliation of segment income to income before tax: Segment income $ 53.9 $ 46.7 $ 104.1 $ 98.1 Net costs not allocated to operating segments 39.6 26.7 81.4 66.0 Income before tax $ 14.3 $ 20.0 $ 22.7 $ 32.1 (in millions) As of March 31, 2017 As of September 30, 2016 Total assets: Commercial Hedging $ 1,654.0 $ 1,637.5 Global Payments 172.4 191.4 Securities 2,611.0 2,130.7 Physical Commodities 309.1 258.0 Clearing and Execution Services 1,651.2 1,617.4 Corporate unallocated 130.9 115.3 Total $ 6,528.6 $ 5,950.3

Basis of Presentation and Con25

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Policies)	6 Months Ended
	Mar. 31, 2017
Basis of Accounting, Policy [Policy Text Block]	The accompanying condensed consolidated balance sheet as of September 30, 2016 , 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. 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, 2016 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 measurement 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.
Securities Borrowed and Loaned Policy [Policy Text Block]	During the quarter ended March 31, 2017, the Company’s Securities reportable segment established a stock lending business. Stock borrowed and stock loaned are accounted for as collateralized financings. Securities borrowed and securities loaned are recorded at the amount of cash collateral advanced or received. Stock borrowed and stock loaned is reported on a gross basis as the Company has determined that the right of offset does not exist. Interest income and interest expense are recognized over the life of the arrangements.
New Accounting Pronouncements, Policy [Policy Text Block]	In April 2015, the FASB issued Accounting Standards Update (“ASU”) No. 2015-03, Interest – Imputation of Interest (Subtopic 835-30). ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. In June 2015, the FASB issued ASU 2015-15 as an amendment to this guidance to address the absence of authoritative guidance for debt issuance costs related to line-of-credit arrangements. The SEC staff stated that they would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. ASU 2015-03 required retrospective application to all prior periods presented in the financial statements. This new guidance was effective for the Company in the first quarter of 2017. As a result of adopting this standard on October 1, 2016, deferred financing costs of $1.0 million as of September 30, 2016, previously reported within other assets, were reclassified to senior unsecured notes in the consolidated balance sheets. As of December 31, 2016, there were no deferred financing costs as the senior unsecured notes were redeemed during the three months ended December 31, 2016, as discussed in Note 9. In January 2017, the FASB issued ASU 2017-01, Business Combinations - Clarifying the Definition of a Business, which clarifies the definition of a business for determining whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This ASU is effective for public business entities for annual and interim periods in fiscal years beginning after December 15, 2017. The adoption of this standard should be applied prospectively on or after the effective date. Early adoption is permitted for transactions for which the acquisition date occurs before the issuance date or effective date of the amendments and only when the transaction has not been reported in financial statements that have been issued or made available for issuance. The Company has early adopted this guidance effective October 1, 2016, and applied the guidance in determining whether the acquisition discussed in Note 16 is the acquisition of an asset or of a business.

Earnings per Share (Policies)

Earnings per Share (Policies)	6 Months Ended
	Mar. 31, 2017
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 ASC.

Income Taxes (Policies)

Income Taxes (Policies)	6 Months Ended
	Mar. 31, 2017
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, 2017
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) 2017 2016 2017 2016 Numerator: Net income $ 11.0 $ 14.5 $ 17.3 $ 23.3 Less: Allocation to participating securities (0.2 ) (0.3 ) (0.3 ) (0.4 ) Net income allocated to common stockholders $ 10.8 $ 14.2 $ 17.0 $ 22.9 Denominator: Weighted average number of: Common shares outstanding 18,404,236 18,592,643 18,325,383 18,621,337 Dilutive potential common shares outstanding: Share-based awards 257,182 162,807 312,097 200,485 Diluted weighted-average shares 18,661,418 18,755,450 18,637,480 18,821,822

Assets and Liabilities, at Fa29

Assets and Liabilities, at Fair Value (Tables)	6 Months Ended
	Mar. 31, 2017
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, 2017 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, 2017. March 31, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificate of deposits $ 3.4 $ — $ — $ — $ 3.4 Commodities warehouse receipts 21.9 — — — 21.9 U.S. government obligations — 225.7 — — 225.7 Securities and other assets segregated under federal and other regulations 21.9 225.7 — — 247.6 Money market funds 376.0 — — — 376.0 U.S. government obligations — 281.8 — — 281.8 Derivatives 1,799.0 — — (1,820.3 ) (21.3 ) Deposits with and receivables from exchange-clearing organizations 2,175.0 281.8 — (1,820.3 ) 636.5 "To be announced" (TBA) and forward settling securities — 6.2 — (0.9 ) 5.3 Derivatives — 89.2 — (59.8 ) 29.4 Deposits with and receivables from broker-dealers, clearing organizations and counterparties — 95.4 — (60.7 ) 34.7 Common and preferred stock and ADRs 28.5 2.0 0.2 — 30.7 Exchangeable foreign ordinary equities and ADRs 31.3 0.4 — — 31.7 Corporate and municipal bonds 4.9 1.3 — — 6.2 U.S. government obligations — 625.4 — — 625.4 Foreign government obligations — 49.4 — — 49.4 Mortgage-backed securities — 926.6 — — 926.6 Derivatives 266.4 1,419.0 — (1,487.0 ) 198.4 Commodities leases — 117.2 — (100.0 ) 17.2 Commodities warehouse receipts 8.0 — — — 8.0 Exchange firm common stock 7.1 — — — 7.1 Mutual funds and other 6.0 — — — 6.0 Financial instruments owned 352.2 3,141.3 0.2 (1,587.0 ) 1,906.7 Physical commodities inventory 117.8 — — — 117.8 Total assets at fair value $ 2,670.3 $ 3,744.2 $ 0.2 $ (3,468.0 ) $ 2,946.7 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 0.9 $ — $ 0.9 TBA and forward settling securities — 10.8 — (0.9 ) 9.9 Derivatives 1,560.8 103.0 — (1,663.9 ) (0.1 ) Payable to broker-dealers, clearing organizations and counterparties 1,560.8 113.8 — (1,664.8 ) 9.8 Common and preferred stock and ADRs 45.4 0.5 — — 45.9 Exchangeable foreign ordinary equities and ADRs 31.6 0.3 — — 31.9 Corporate and municipal bonds 1.2 — — — 1.2 U.S. government obligations — 699.9 — — 699.9 Foreign government obligations — 10.1 — — 10.1 Mortgage-backed securities — 4.7 — — 4.7 Derivatives 261.0 1,575.9 — (1,607.3 ) 229.6 Commodities leases — 164.8 — (106.9 ) 57.9 Financial instruments sold, not yet purchased 339.2 2,456.2 — (1,714.2 ) 1,081.2 Total liabilities at fair value $ 1,900.0 $ 2,570.0 $ 0.9 $ (3,379.0 ) $ 1,091.9 (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. The following table sets forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2016 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 September 30, 2016. September 30, 2016 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificates of deposits $ 7.1 $ — $ — $ — $ 7.1 Commodities warehouse receipts 23.3 — — — 23.3 U.S. government obligations — 595.5 — — 595.5 Securities and other assets segregated under federal and other regulations 23.3 595.5 — — 618.8 Money market funds 512.7 — — — 512.7 U.S. government obligations — 472.1 — — 472.1 Derivatives 2,149.9 — — (2,266.2 ) (116.3 ) Deposits with and receivables from exchange-clearing organizations 2,662.6 472.1 — (2,266.2 ) 868.5 TBA and forward settling securities — 0.3 — — 0.3 Derivatives — 8.0 — (23.5 ) (15.5 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties — 8.3 — (23.5 ) (15.2 ) Common and preferred stock and ADRs 34.6 1.7 0.2 — 36.5 Exchangeable foreign ordinary equities and ADRs 25.2 0.5 — — 25.7 Corporate and municipal bonds 36.9 0.9 3.0 — 40.8 U.S. government obligations — 514.9 — — 514.9 Foreign government obligations — 14.6 — — 14.6 Mortgage-backed securities — 747.5 — — 747.5 Derivatives 206.9 1,350.8 — (1,363.8 ) 193.9 Commodities leases — 137.2 — (129.1 ) 8.1 Commodities warehouse receipts 8.9 — — — 8.9 Exchange firm common stock 6.4 — — — 6.4 Mutual funds and other 8.8 — — — 8.8 Financial instruments owned 327.7 2,768.1 3.2 (1,492.9 ) 1,606.1 Physical commodities inventory, net - precious metals 71.2 — — — 71.2 Total assets at fair value $ 3,091.9 $ 3,844.0 $ 3.2 $ (3,782.6 ) $ 3,156.5 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 0.8 $ — $ 0.8 TBA and forward settling securities — 2.6 — 0.9 3.5 Derivatives 1,961.7 97.5 — (2,059.2 ) — Payable to broker-dealers, clearing organizations and counterparties 1,961.7 100.1 — (2,058.3 ) 3.5 Common and preferred stock and ADRs 23.5 0.4 — — 23.9 Exchangeable foreign ordinary equities and ADRs 25.3 0.5 — — 25.8 U.S. government obligations — 509.8 — — 509.8 Corporate and municipal bonds 6.9 — — — 6.9 Derivatives 199.4 1,319.3 — (1,307.8 ) 210.9 Commodities leases — 207.8 — (145.7 ) 62.1 Financial instruments sold, not yet purchased 255.1 2,037.8 — (1,453.5 ) 839.4 Total liabilities at fair value $ 2,216.8 $ 2,137.9 $ 0.8 $ (3,511.8 ) $ 843.7 (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.
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, 2017 and September 30, 2016 are summarized below: (in millions) March 31, 2017 September 30, 2016 Total level 3 assets $ 0.2 $ 3.2 Level 3 assets for which the Company bears economic exposure $ 0.2 $ 3.2 Total assets $ 6,528.6 $ 5,950.3 Total assets at fair value $ 2,946.7 $ 3,156.5 Total level 3 assets as a percentage of total assets — % 0.1 % Level 3 assets for which the Company bears economic exposure as a percentage of total assets — % 0.1 % Total level 3 assets as a percentage of total financial assets at fair value — % 0.1 % 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, 2017 and 2016 , 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, 2017 . Level 3 Financial Assets and Financial Liabilities For the Three Months Ended March 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.2 $ — $ — $ — $ — $ — $ 0.2 Corporate and municipal bonds — — — — — — — $ 0.2 $ — $ — $ — $ — $ — $ 0.2 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 0.8 $ — $ 0.1 $ — $ — $ — $ 0.9 Level 3 Financial Assets and Financial Liabilities For the Six Months Ended March 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.2 $ — $ — $ — $ — $ — $ 0.2 Corporate and municipal bonds 3.0 — — — (3.0 ) — — $ 3.2 $ — $ — $ — $ (3.0 ) $ — $ 0.2 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 0.8 $ — $ 0.1 $ — $ — $ — $ 0.9 Level 3 Financial Assets and Financial Liabilities For the Three Months Ended March 31, 2016 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.3 $ — $ — $ — $ — $ — $ 0.3 Corporate and municipal bonds 3.2 — 0.1 — — — 3.3 $ 3.5 $ — $ 0.1 $ — $ — $ — $ 3.6 (in millions) Balances at Realized (gains) Unrealized Purchases/issuances Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 3.5 $ — $ 0.1 $ — $ (2.1 ) $ — $ 1.5

Financial Instruments with Of30

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	6 Months Ended
	Mar. 31, 2017
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, 2017 and September 30, 2016 . Assets represent net unrealized gains and liabilities represent net unrealized losses. March 31, 2017 September 30, 2016 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,617.7 $ 1,496.9 $ 2,022.1 $ 1,920.5 OTC commodity derivatives 1,336.7 1,518.4 1,217.0 1,188.9 Exchange-traded foreign exchange derivatives 22.6 21.0 12.2 7.5 OTC foreign exchange derivatives 434.8 317.8 346.5 290.2 Exchange-traded interest rate derivatives 132.9 113.9 78.7 120.5 Equity index derivatives 28.9 32.7 39.1 50.3 TBA and forward settling securities 6.2 10.8 0.3 2.6 Gross fair value of derivative contracts 3,579.8 3,511.5 3,715.9 3,580.5 Impact of netting and collateral (3,368.0 ) (3,272.1 ) (3,653.5 ) (3,366.1 ) Total fair value included in ‘Deposits with and receivables from exchange-clearing organizations’ $ (21.3 ) $ (116.3 ) Total fair value included in ‘Deposits with and receivables from broker-dealers, clearing organizations and counterparties’ $ 34.7 $ (15.2 ) Total fair value included in ‘Financial instruments owned, at fair value’ $ 198.4 $ 193.9 Total fair value included in ‘Payables to broker-dealers, clearing organizations and counterparties $ 9.8 $ 3.5 Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’ $ 229.6 $ 210.9 (1) As of March 31, 2017 and September 30, 2016 , the Company’s derivative contract volume for open positions were approximately 4.1 million and 4.0 million contracts, respectively. The Company’s derivative contracts are principally held in its Commercial Hedging and Clearing and Execution Services segments. 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 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 Company has derivative instruments, which consist of mortgage-backed TBA securities and forward settling transactions that are used to manage risk exposures in the trading inventory of the Company’s domestic fixed income institutional business. The fair value on these transactions are recorded in receivables or payables to broker-dealers, clearing organizations and counterparties. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘trading gains, net’. The Company enters into TBA securities transactions for the sole purpose of managing risk associated with the purchase of mortgage pass-through securities. TBA securities are included within deposits with and receivables from and payables to broker-dealers, clearing organizations and counterparties. Forward settling securities represent non-regular way securities and are included in financial instruments owned and sold. As of March 31, 2017 and September 30, 2016 , these transactions are summarized as follows: March 31, 2017 September 30, 2016 (in millions) Gain / (Loss) Notional Amounts Gain / (Loss) Notional Amounts Unrealized gain on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 3.2 $ 795.7 $ 0.8 $ 289.8 Unrealized loss on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (0.4 ) $ 180.4 $ (0.8 ) $ 485.5 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 0.6 $ (351.4 ) $ 1.3 $ (702.3 ) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (9.6 ) $ (1,537.9 ) $ (1.7 ) $ (754.3 ) Unrealized gain on forward settling securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 2.5 $ 595.5 $ 0.1 $ 607.9 Unrealized (loss) gain on forward settling securities sold within receivables from and payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.9 ) $ (301.4 ) $ 0.2 $ (470.4 ) (1) The notional amounts of these instruments reflect the extent of the Company's involvement in TBA and forward settling securities and do not represent risk of loss due to counterparty non-performance.
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, 2017 and 2016 in accordance with the Derivatives and Hedging Topic of the ASC. The gains set forth below are included in ‘trading gains, net’ in the condensed consolidated income statements. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2017 2016 2017 2016 Commodities $ 13.9 $ 5.0 $ 18.8 $ 25.0 Foreign exchange 0.8 1.8 2.0 3.6 Interest rate — 2.9 (1.0 ) 1.0 TBA and forward settling securities (4.9 ) (5.7 ) 8.5 (5.0 ) Net gains from derivative contracts $ 9.8 $ 4.0 $ 28.3 $ 24.6

Physical Commodities Inventor31

Physical Commodities Inventory Physical Commodities Table (Tables)	6 Months Ended
	Mar. 31, 2017
Inventory Disclosure [Abstract]
Schedule of Inventory, Current [Table Text Block]	(in millions) March 31, September 30, Physical Ag & Energy (1) $ 139.5 $ 65.9 Precious metals - held by broker-dealer subsidiary (2) 17.0 5.3 Precious metals - held by non-broker-dealer subsidiaries (3) 25.2 52.6 Physical commodities inventory $ 181.7 $ 123.8

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Mar. 31, 2017
Goodwill [Abstract]
Schedule of Goodwill [Table Text Block]	The carrying value of goodwill is allocated to the Company’s operating segments as follows: (in millions) March 31, September 30, Commercial Hedging $ 30.7 $ 30.7 Global Payments 6.3 6.3 Physical Commodities 2.4 2.4 Securities 8.1 8.1 Goodwill $ 47.5 $ 47.5

Intangible Assets - (Tables)

Intangible Assets - (Tables)	6 Months Ended
	Mar. 31, 2017
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, 2017 September 30, 2016 (in millions) Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization Trade name $ 1.1 $ (0.8 ) $ 0.3 $ 1.1 $ (0.6 ) $ 0.5 Software programs/platforms 2.7 (2.4 ) 0.3 2.7 (2.4 ) 0.3 Customer base 20.0 (6.9 ) 13.1 14.0 (5.7 ) 8.3 Total intangible assets $ 23.8 $ (10.1 ) $ 13.7 $ 17.8 $ (8.7 ) $ 9.1
Schedule of Expected Amortization Expense [Table Text Block]	Amortization expense related to intangible assets was $1.4 million and $0.8 million for the six months ended March 31, 2017 and 2016 , respectively. As of March 31, 2017 , the estimated future amortization expense was as follows: (in millions) Fiscal 2017 (remaining six months) $ 1.4 Fiscal 2018 2.2 Fiscal 2019 2.2 Fiscal 2020 2.0 Fiscal 2021 and thereafter 5.9 $ 13.7

Credit Facilities (Tables)

Credit Facilities (Tables)	6 Months Ended
	Mar. 31, 2017
Credit Facilities [Abstract]
Schedule of Debt [Table Text Block]	The following table sets forth a listing of credit facilities, the committed amounts as of March 31, 2017 on the facilities, and outstanding borrowings on the facilities as well as indebtedness on a promissory note and on senior notes as of March 31, 2017 and September 30, 2016 : (in millions) Credit Facilities Amounts Outstanding Borrower Security Renewal / Expiration Date Total Commitment March 31, September 30, INTL FCStone Inc. Pledged shares of certain subsidiaries March 18, 2019 $ 247.0 $ 175.0 $ 136.5 INTL FCStone Financial Inc. None April 5, 2018 75.0 — — INTL FCStone Financial Inc. Commodity warehouse receipts n/a — — — FCStone Merchants Services, LLC Certain commodities assets May 1, 2018 100.0 86.0 43.5 INTL FCStone Ltd None October 27, 2017 25.0 — — INTL FCStone Ltd Commodity warehouse receipts n/a — — — Sterne, Agee & Leach, Inc. Certain pledged securities n/a — — — $ 447.0 261.0 180.0 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 2.4 2.8 Senior Unsecured Notes 8.50% senior notes, due July 30, 2020 (redeemed on October 15, 2016) — 44.5 Total indebtedness $ 263.4 $ 227.3

Capital and Other Regulatory 35

Capital and Other Regulatory Requirements (Tables)	6 Months Ended
	Mar. 31, 2017
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, 2017 , as follows: (in millions) As of March 31, 2017 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. Securities and Exchange Commission ("SEC") and Commodity Futures Trading Commission ("CFTC") United States Net capital $ 146.7 $ 83.4 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,127.0 $ 2,075.6 INTL FCStone Financial Inc. CFTC United States Secured funds $ 145.5 $ 128.7 Sterne Agee Clearing Inc. SEC United States Net capital $ 1.3 $ 0.1 Sterne, Agee & Leach, Inc. SEC United States Net capital $ 28.0 $ 2.0 Sterne Agee Financial Services, Inc. SEC United States Net capital $ 5.9 $ 0.3 INTL FCStone Ltd (1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 159.6 $ 87.1 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 72.0 $ 69.4 INTL Netherlands BV (1) FCA United Kingdom Net capital $ 158.9 $ 87.1 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 9.6 $ 0.5 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 5.3 $ 0.2 INTL Gainvest S.A. CNV Argentina Net capital $ 0.8 $ 0.1 INTL Capital S.A. General Inspector of Justice (Argentina) Argentina Net capital $ 10.7 $ 9.2 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.5 $ 1.1 INTL CIBSA S.A. CNV Argentina Net capital $ 7.1 $ 0.6 (1) INTL Netherlands BV is a holding company that includes the ownership equity of INTL FCStone Ltd. The associated net capital amounts and minimum requirements should not be considered in aggregate. Sterne, Agee & Leach, Inc. is also subject to Rule 15c3-3 of the Securities Exchange Act of 1934, as amended (“Customer Protection Rule”) inclusive of computations for proprietary accounts of broker-dealers (“PABs”). As of March 31, 2017 , Sterne, Agee & Leach, Inc. had $7.8 million of cash in a Special Reserve Bank Account (“SRBA”) for the exclusive benefit of customers under the Customer Protection Rule pursuant to SEC Rule 15c3-3, Computation for Determination of Reserve Requirements . Also, as of March 31, 2017, Sterne, Agee & Leach, Inc. had $6.0 million of cash in a SRBA pursuant to SEC Rule 15c3-3, Computation for Determination of PAB Reserve Requirements. As of March 31, 2017 , the amount on deposit in both the customers and the PABs SRBA was less than the reserve requirement and additional funds were deposited subsequent to period-end. 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, 2017 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Tables)

Other Expenses (Tables)	6 Months Ended
	Mar. 31, 2017
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, 2017 and 2016 consisted of the following: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2017 2016 2017 2016 Contingent consideration, net $ 0.1 $ 0.1 $ 0.1 $ 0.3 Insurance 0.8 0.3 1.3 0.7 Advertising, meetings and conferences 1.2 2.3 2.1 3.0 Non-trading hardware and software maintenance and software licensing 2.8 1.3 5.7 2.8 Office supplies and printing 0.5 0.3 1.1 0.6 Other clearing related expenses 0.3 0.3 0.7 0.5 Other non-income taxes 1.2 1.1 2.3 2.1 Other 2.5 1.7 4.6 3.7 Total other expenses $ 9.4 $ 7.4 $ 17.9 $ 13.7

Accumulated Other Comprehensi37

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Mar. 31, 2017
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 loss for the six months ended March 31, 2017 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2016 $ (20.1 ) $ (4.5 ) $ (24.6 ) Other comprehensive loss, net of tax (0.2 ) — (0.2 ) Balances as of March 31, 2017 $ (20.3 ) $ (4.5 ) $ (24.8 )

Segment Analysis (Tables)

Segment Analysis (Tables)	6 Months Ended
	Mar. 31, 2017
Segment Analysis [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Information for the reportable segments 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) 2017 2016 2017 2016 Total revenues: Commercial Hedging $ 62.7 $ 54.7 $ 120.2 $ 110.1 Global Payments 21.5 17.4 44.6 35.7 Securities 37.9 45.6 75.3 94.4 Physical Commodities 5,276.2 3,550.7 11,174.9 6,805.2 Clearing and Execution Services 64.2 33.3 127.8 63.1 Corporate unallocated (1.7 ) 7.2 (7.6 ) 0.3 Total $ 5,460.8 $ 3,708.9 $ 11,535.2 $ 7,108.8 Operating revenues (loss): Commercial Hedging $ 62.7 $ 54.7 $ 120.2 $ 110.1 Global Payments 21.5 17.4 44.6 35.7 Securities 37.9 45.6 75.3 94.4 Physical Commodities 11.2 7.9 21.0 13.8 Clearing and Execution Services 64.2 33.3 127.8 63.1 Corporate unallocated (1.7 ) 7.2 (7.6 ) 0.3 Total $ 195.8 $ 166.1 $ 381.3 $ 317.4 Net operating revenues (loss): Commercial Hedging $ 50.5 $ 43.6 $ 96.1 $ 87.9 Global Payments 19.1 15.5 39.7 31.8 Securities 24.1 31.8 49.2 67.8 Physical Commodities 9.0 6.8 17.1 11.5 Clearing and Execution Services 25.4 10.4 49.5 20.8 Corporate unallocated (4.2 ) 4.8 (13.4 ) (4.2 ) Total $ 123.9 $ 112.9 $ 238.2 $ 215.6 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable bonus compensation, introducing broker commissions and interest expense) Commercial Hedging $ 36.9 $ 30.5 $ 70.3 $ 62.2 Global Payments 15.3 12.4 31.7 25.4 Securities 18.9 25.0 38.7 54.5 Physical Commodities 6.5 5.3 12.3 8.7 Clearing and Execution Services 19.6 8.2 37.6 16.1 Total $ 97.2 $ 81.4 $ 190.6 $ 166.9 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 18.7 $ 13.8 $ 34.1 $ 28.8 Global Payments 11.7 9.3 24.9 19.3 Securities 11.7 18.2 24.6 40.1 Physical Commodities 3.9 1.9 6.9 2.9 Clearing and Execution Services 7.9 3.5 13.6 7.0 Total $ 53.9 $ 46.7 $ 104.1 $ 98.1 Reconciliation of segment income to income before tax: Segment income $ 53.9 $ 46.7 $ 104.1 $ 98.1 Net costs not allocated to operating segments 39.6 26.7 81.4 66.0 Income before tax $ 14.3 $ 20.0 $ 22.7 $ 32.1 (in millions) As of March 31, 2017 As of September 30, 2016 Total assets: Commercial Hedging $ 1,654.0 $ 1,637.5 Global Payments 172.4 191.4 Securities 2,611.0 2,130.7 Physical Commodities 309.1 258.0 Clearing and Execution Services 1,651.2 1,617.4 Corporate unallocated 130.9 115.3 Total $ 6,528.6 $ 5,950.3

Basis of Presentation and Con39

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Details) $ in Millions	6 Months Ended
	Mar. 31, 2017	Sep. 30, 2016USD ($)
Basis of Presentation and Consolidation [Abstract]
Debt Issuance Costs, Net		$ 1
Number of different types of foreign currencies	140
Number of accounts for customers company-wide	20,000

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 11	$ 14.5	$ 17.3	$ 23.3
Less: Net income allocated to participating securities	(0.2)	(0.3)	(0.3)	(0.4)
Net income allocated to common shareholders	$ 10.8	$ 14.2	$ 17	$ 22.9
Weighted average number of common shares outstanding	18,404,236	18,592,643	18,325,383	18,621,337
Dilutive potential common shares outstanding:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	257,182	162,807	312,097	200,485
Diluted weighted-average shares	18,661,418	18,755,450	18,637,480	18,821,822

Earnings per Share - Antiduliti

Earnings per Share - Antidulitive Securities (Details) - shares	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	322,974	986,339	242,448	900,665

Assets and Liabilities, at Fa42

Assets and Liabilities, at Fair Value Assets and Liabilities, at Fair Value - Financial Instruments at Fair Value Disclosure (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016	Jul. 31, 2013
Assets and Liabilities, at Fair Value [Abstract]
Senior unsecured notes	$ 0	$ 44.5	$ 45.5

Assets and Liabilities, at Fa43

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	$ 1,085.5	$ 1,136.3
Receivables from Clearing Organizations	1,679.4	1,524.4
Receivables from Brokers-Dealers and Clearing Organizations	170.3	237
Financial Instruments, Owned, at Fair Value	1,906.7	1,606.1
Physical commodities inventory	181.7	123.8
Assets, Fair Value Disclosure	2,946.7	3,156.5
Accounts Payable and Other Accrued Liabilities	147.4	161.3
Payables to Broker-Dealers and Clearing Organizations	178.2	260.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	1,081.2	839.4
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	247.6	618.8
Receivables from Clearing Organizations	636.5	868.5
Receivables from Brokers-Dealers and Clearing Organizations	34.7	(15.2)
Financial Instruments, Owned, at Fair Value	1,906.7	1,606.1
Assets, Fair Value Disclosure	2,946.7	3,156.5
Payables to Broker-Dealers and Clearing Organizations	9.8	3.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	1,081.2	839.4
Liabilities, Fair Value Disclosure	1,091.9	843.7
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	9.9	3.5
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(0.1)	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	0.9	0.8
Fair Value, Measurements, Recurring [Member] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	117.8	71.2
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	30.7	36.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	45.9	23.9
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	31.7	25.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	31.9	25.8
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	6.2	40.8
Financial Instruments Sold, Not yet Purchased, at Fair Value	1.2	6.9
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	625.4	514.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	699.9	509.8
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	49.4	14.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	10.1
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	926.6	747.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	4.7
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	198.4	193.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	229.6	210.9
Fair Value, Measurements, Recurring [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	17.2	8.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	57.9	62.1
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	8	8.9
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	7.1	6.4
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	6	8.8
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and Clearing Organizations	5.3	0.3
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and Clearing Organizations	29.4	(15.5)
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	376	512.7
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	281.8	472.1
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(21.3)	(116.3)
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	21.9	23.3
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	225.7	595.5
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	3.4	7.1
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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
Receivables from Clearing Organizations	(1,820.3)	(2,266.2)
Receivables from Brokers-Dealers and Clearing Organizations	(60.7)	(23.5)
Financial Instruments, Owned, at Fair Value	(1,587)	(1,492.9)
Assets, Fair Value Disclosure	(3,468)	(3,782.6)
Payables to Broker-Dealers and Clearing Organizations	(1,664.8)	(2,058.3)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(1,714.2)	(1,453.5)
Liabilities, Fair Value Disclosure	(3,379)	(3,511.8)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(0.9)	0.9
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(1,663.9)	(2,059.2)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [Member] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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
Financial Instruments Sold, Not yet Purchased, at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	(1,487)	(1,363.8)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(1,607.3)	(1,307.8)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	(100)	(129.1)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(106.9)	(145.7)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and Clearing Organizations	(0.9)	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and Clearing Organizations	(59.8)	(23.5)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(1,820.3)	(2,266.2)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [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	0
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 Securities Segregated under Federal and Other Regulations	21.9	23.3
Receivables from Clearing Organizations	2,175	2,662.6
Receivables from Brokers-Dealers and Clearing Organizations	0	0
Financial Instruments, Owned, at Fair Value	352.2	327.7
Assets, Fair Value Disclosure	2,670.3	3,091.9
Payables to Broker-Dealers and Clearing Organizations	1,560.8	1,961.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	339.2	255.1
Liabilities, Fair Value Disclosure	1,900	2,216.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and 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]
Payables to Broker-Dealers and Clearing Organizations	1,560.8	1,961.7
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] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	117.8	71.2
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	28.5	34.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	45.4	23.5
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	31.3	25.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	31.6	25.3
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	4.9	36.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	1.2	6.9
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
Financial Instruments Sold, Not yet Purchased, 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	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	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]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	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]
Financial Instruments, Owned, at Fair Value	266.4	206.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	261	199.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases [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	8	8.9
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	7.1	6.4
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	6	8.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and 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 Brokers-Dealers and Clearing Organizations	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]
Receivables from Clearing Organizations	376	512.7
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] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	1,799	2,149.9
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	21.9	23.3
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] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	3.4	7.1
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 Securities Segregated under Federal and Other Regulations	225.7	595.5
Receivables from Clearing Organizations	281.8	472.1
Receivables from Brokers-Dealers and Clearing Organizations	95.4	8.3
Financial Instruments, Owned, at Fair Value	3,141.3	2,768.1
Assets, Fair Value Disclosure	3,744.2	3,844
Payables to Broker-Dealers and Clearing Organizations	113.8	100.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	2,456.2	2,037.8
Liabilities, Fair Value Disclosure	2,570	2,137.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	10.8	2.6
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 Broker-Dealers and Clearing Organizations	103	97.5
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] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	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	2	1.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.5	0.4
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	0.4	0.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.3	0.5
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	1.3	0.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	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]
Financial Instruments, Owned, at Fair Value	625.4	514.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	699.9	509.8
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	49.4	14.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	10.1
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	926.6	747.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	4.7
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	1,419	1,350.8
Financial Instruments Sold, Not yet Purchased, at Fair Value	1,575.9	1,319.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	117.2	137.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	164.8	207.8
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] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and Clearing Organizations	6.2	0.3
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 Brokers-Dealers and Clearing Organizations	89.2	8
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	281.8	472.1
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] | 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	225.7	595.5
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	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 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	0.2	3.2
Assets, Fair Value Disclosure	0.2	3.2
Payables to Broker-Dealers and Clearing Organizations	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Liabilities, Fair Value Disclosure	0.9	0.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and 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]
Payables to Broker-Dealers and Clearing Organizations	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	0.9	0.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
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	0.2	0.2
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	0	3
Financial Instruments Sold, Not yet Purchased, at Fair Value	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]
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] | 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
Financial Instruments Sold, Not yet Purchased, at Fair Value	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	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	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 [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] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Brokers-Dealers and 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 Brokers-Dealers and 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]
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] | 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] | 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] | 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	$ 0

Assets and Liabilities, at Fa44

Assets and Liabilities, at Fair Value - Details of Level 3 Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Assets and Liabilities, at Fair Value [Abstract]
Total Level 3 Assets	$ 0.2	$ 3.2
Level 3 assets for which the company bears economic exposure	0.2	3.2
Assets	6,528.6	5,950.3
Assets, Fair Value Disclosure	$ 2,946.7	$ 3,156.5
Total level 3 assets as a percentage of total assets	0.00%	0.10%
Level 3 assets for which the company bears economic exposure as a percertange of total assets	0.00%	0.10%
Total level 3 assets as a percentage of total financial assets at fair value	0.00%	0.10%
Suriwongse Debt Investment Balance		$ 3

Assets and Liabilities, at Fa45

Assets and Liabilities, at Fair Value - Rollforward of Level 3 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Rollforward of Level 3 Securities [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0.2		$ 0.2
Contingent Consideration [Member]
Rollforward of Level 3 Liabilities [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	0.8	$ 3.5	0.8	$ 3.3
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	0.1	0.1	0.3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0	2.1	0	2.1
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	0.9	1.5	0.9	1.5
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	0.2	0.3	0.2	0.5
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	(0.2)
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	0.2	0.3	0.2	0.3
Corporate Debt Securities [Member]
Rollforward of Level 3 Securities [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0	3.2	3	3.2
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	0.1	0	0.1
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	(3)	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	$ 3.3	$ 0	$ 3.3

Assets and Liabilities, at Fa46

Assets and Liabilities, at Fair Value - Contingent Consideration (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2015	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration for acquisitions	$ 0.1		$ 0	$ 0.3
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration for acquisitions		$ 0.2	$ 0.1	$ 0.3

Financial Instruments with Of47

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Obligations to Purchase Financial Instruments at a Future Date (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Financial Instruments Sold, Not yet Purchased, at Fair Value	$ 1,081.2	$ 839.4

Financial Instruments with Of48

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 ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 3,579.8	$ 3,715.9
Derivative Liability, Fair Value, Gross Liability	3,511.5	3,580.5
Derivative Asset, Fair Value, Amount Offset Against Collateral	(3,368)	(3,653.5)
Derivative Liability, Fair Value, Amount Offset Against Collateral	(3,272.1)	(3,366.1)
Deposits and Receivables from Exchange Clearing Organizations [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(21.3)	(116.3)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	34.7	(15.2)
Financial instruments owned [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	198.4	193.9
Payable to broker-dealers, clearing organizations and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	9.8	3.5
Financial instrument sold, not yet purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	229.6	210.9
Exchange-traded Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,617.7	2,022.1
Derivative Liability, Fair Value, Gross Liability	1,496.9	1,920.5
Over the Counter (OTC) Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,336.7	1,217
Derivative Liability, Fair Value, Gross Liability	1,518.4	1,188.9
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	22.6	12.2
Derivative Liability, Fair Value, Gross Liability	21	7.5
Over the Counter (OTC) Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	434.8	346.5
Derivative Liability, Fair Value, Gross Liability	317.8	290.2
Exchange-traded interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	132.9	78.7
Derivative Liability, Fair Value, Gross Liability	113.9	120.5
Equity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28.9	39.1
Derivative Liability, Fair Value, Gross Liability	32.7	50.3
TBA and forward settling securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6.2	0.3
Derivative Liability, Fair Value, Gross Liability	$ 10.8	$ 2.6

Financial Instruments with Of49

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) number in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2016USD ($)	Mar. 31, 2017
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative, Notional Amount	$ 375
Derivative, Average Remaining Maturity	15 months
Derivative, Number of Instruments Held	4	4.1

Financial Instruments with Of50

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - TBAs and Forward Settling Securities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Derivative Asset, Fair Value, Gross Asset	$ 3,579.8	$ 3,715.9
Derivative Liability, Fair Value, Gross Liability	3,511.5	3,580.5
TBA securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset	3.2	0.8
Derivative Liability, Notional Amount	(180.4)	(485.5)
Derivative Liability, Fair Value, Gross Liability	(0.4)	(0.8)
Derivative Asset, Notional Amount	(795.7)	(289.8)
TBA securities sold [Member]
Derivative Asset, Fair Value, Gross Asset	0.6	1.3
Derivative Liability, Notional Amount	(1,537.9)	(754.3)
Derivative Liability, Fair Value, Gross Liability	(9.6)	(1.7)
Derivative Asset, Notional Amount	(351.4)	(702.3)
Forward settling securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset	2.5	0.1
Derivative Asset, Notional Amount	(595.5)	(607.9)
Over the Counter (OTC) Commodity Contracts [Member]
Derivative Liability, Notional Amount	(301.4)	(470.4)
Derivative Liability, Fair Value, Gross Liability	$ (0.9)	$ 0.2

Financial Instruments with Of51

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 13.9	$ 5	$ 18.8	$ 25
Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0.8	1.8	2	3.6
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0	2.9	(1)	1
TBA and forward settling securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(4.9)	(5.7)	8.5	(5)
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 9.8	$ 4	$ 28.3	$ 24.6

Receivables From Customers, N52

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Customer Receivables (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Receivables from customers and notes receivable, net [Abstract]
Allowance for Doubtful Accounts Receivable	$ 10.8	$ 9.5

Receivables From Customers, N53

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Notes Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Allowance Notes Receivable	$ 0	$ 0.2

Receivables From Customers, N54

Receivables From Customers, Net and Notes Receivable, Net Receivables from Customers, Net and Notes Receivables, Net - Bad Debt Expense and Recoveries (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)		$ 1.3
Provision for Doubtful Accounts		2.6
Commercial Hedging [Member]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)		1.1	$ 2.7
Provision for Doubtful Accounts	$ 1.3		3.8
Securities [Member]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)		$ 0.2	$ 0.3

Receivables From Customers, N55

Receivables From Customers, Net and Notes Receivable, Net - Exim Bank Notes Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Insured short-term notes receivable	$ 2.1		$ 5
Obligations for participation rights	$ 2.1		$ 4.6
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 Inventor56

Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Inventory [Line Items]
Physical Ag & Energy(1)	$ 139.5		$ 65.9
Precious metals - held by non-broker-dealer subsidiaries(3)		$ 117.8	71.2
Physical commodities inventory	181.7		123.8
Physical commodities inventory - precious metals [Member]
Inventory [Line Items]
Precious metals - held by non-broker-dealer subsidiaries(3)	17		5.3
Finished commodities	$ 25.2		$ 52.6

Physical Commodities Inventor57

Physical Commodities Inventory - LCM Adjustments (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Inventory Adjustments	$ 0.1	$ 0.6

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Goodwill [Line Items]
Goodwill	$ 47.5	$ 47.5
Commercial Hedging [Member]
Goodwill [Line Items]
Goodwill	30.7	30.7
Global Payments [Member]
Goodwill [Line Items]
Goodwill	6.3	6.3
Physical Commodities [Member]
Goodwill [Line Items]
Goodwill	2.4	2.4
Securities [Member]
Goodwill [Line Items]
Goodwill	$ 8.1	$ 8.1

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 6
Finite-Lived Intangible Assets, Net	13.7
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Trade Names, Gross	1.1	$ 1.1
Finite-Lived Intangible Assets, Accumulated Amortization	(0.8)	(0.6)
Finite-Lived Intangible Assets, Net	0.3	0.5
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Computer Software, Gross	2.7	2.7
Finite-Lived Intangible Assets, Accumulated Amortization	(2.4)	(2.4)
Finite-Lived Intangible Assets, Net	0.3	0.3
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Customer Lists, Gross	20	14
Finite-Lived Intangible Assets, Accumulated Amortization	(6.9)	(5.7)
Finite-Lived Intangible Assets, Net	$ 13.1	$ 8.3

Intangible Assets - Indefinite-

Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Indefinite-lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 1.4	$ 0.8
Gross Finite and Indefinite-Lived Intangible Assets	23.8		$ 17.8
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	(10.1)		(8.7)
Intangible Assets, Net (Excluding Goodwill)	$ 13.7		$ 9.1

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Amortization of Intangible Assets	$ 1.4	$ 0.8
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2016 (remaining nine months)	1.4
Fiscal 2,017	2.2
Fiscal 2,018	2.2
Fiscal 2,019	2
Fiscal 2020 and thereafter	5.9
Finite-Lived Intangible Assets, Net	13.7
Trade Names [Member]
Finite-Lived Trade Names, Gross	1.1		$ 1.1
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Finite-Lived Intangible Assets, Net	$ 0.3		$ 0.5

Credit Facilities - Number of C

Credit Facilities - Number of Credit Facilities (Details) $ in Millions	6 Months Ended
	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)
Repayments of Unsecured Debt	$ 45.5	$ 0
Number of credit facilities	4

Credit Facilities - Credit Faci

Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	May 05, 2015	Jul. 31, 2013
Line of Credit Facility [Line Items]
Short-term Debt	$ 261		$ 180
Lenders under loans	263.4		182.8
Notes Payable to Bank	2.4		2.8
Senior unsecured notes	0		44.5		$ 45.5
Debt and Capital Lease Obligations	263.4		227.3
Debt Instrument, Interest Rate, Stated Percentage		8.50%
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	200
Line of Credit Facility, Maximum Borrowing Capacity	447
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	247
Lenders under loans	175		136.5
FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75			$ 50
Lenders under loans	0		0
FCStone LLC [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0
Lenders under loans	0		0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Lenders under loans	86		43.5
INTL FCStone Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	25
Lenders under loans	$ 0		$ 0

Commodity and Other Repurchas64

Commodity and Other Repurchase Agreements Commodity and Other Repurchase Agreements (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	$ 957.7
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	654.5
Financing Receivables, net - Sales/Repurchase Agreements	0.6		$ 1.5
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	324.6
Securities Sold under Agreements to Repurchase, Fair Value of Collateral		$ 324.6	$ 47.2
Trading Securities Pledged as Collateral	1,160
Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements	$ 86.8

Commitments and Contingencies -

Commitments and Contingencies - Contigent Consideration for Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2015	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	$ 0.9		$ 0.9		$ 0.8
Change in fair value of contingent consideration for acquisitions	0.1		0	$ 0.3
G.X. Clarke (INTL FCStone Partners) [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	0.9		0.9
Present Value of Estimated Total Purchase Price	28.7		28.7
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 1.5		1.5
Contingent Consideration [Member]
Business Acquisition, Contingent Consideration [Line Items]
Change in fair value of contingent consideration for acquisitions		$ 0.2	$ 0.1	$ 0.3

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Self Insurance (Details) $ in Millions	Mar. 31, 2017USD ($)
Commitments and Contingencies [Abstract]
Self Insurance Reserve	$ 0.9

Capital and Other Regulatory 67

Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) $ in Millions	Mar. 31, 2017USD ($)
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 146.7
Required Net Capital under Commodity Exchange Act	83.4
Cash and Securities Segregated under Commodity Exchange Act Regulation	2,127
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	2,075.6
Secured Funds	145.5
Secured Funds Required Under Commodity Exchange Act	128.7
Sterne Agee Clearing, Inc. [Member]
Net Capital under Commodity Exchange Act Computation	1.3
Required Net Capital under Commodity Exchange Act	0.1
Sterne Agee, and Leach, Inc [Member]
Net Capital under Commodity Exchange Act Computation	28
Required Net Capital under Commodity Exchange Act	2
Sterne Agee Financial Services, Inc. [Member]
Net Capital under Commodity Exchange Act Computation	5.9
Required Net Capital under Commodity Exchange Act	0.3
INTL FCStone Ltd [Member]
Net Capital under Commodity Exchange Act Computation	159.6
Required Net Capital under Commodity Exchange Act	87.1
Cash and Securities Segregated under Commodity Exchange Act Regulation	72
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	69.4
INTL Netherlands BV [Member]
Net Capital under Commodity Exchange Act Computation	158.9
Required Net Capital under Commodity Exchange Act	87.1
INTL FCStone DTVM Ltda [Member]
Net Capital	9.6
Capital Required for Capital Adequacy	0.5
Gainvest S.A. Sociedad Gerente de FCI - Comision Nacional de Valores [Member]
Net Capital under Commodity Exchange Act Computation	0.8
Required Net Capital under Commodity Exchange Act	0.1
Net Capital	5.3
Capital Required for Capital Adequacy	0.2
INTL Capital S.A – Rosario Futures Exchanges [Member] [Domain]
Net Capital	10.7
Capital Required for Capital Adequacy	9.2
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	5.5
Required Net Capital under Commodity Exchange Act	1.1
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	7.1
Required Net Capital under Commodity Exchange Act	0.6
Customer Reserve Requirement [Member] [Member]
Cash Reserve Deposit Required and Made	7.8
PAB Reserve Requirement [Member]
Cash Reserve Deposit Required and Made	$ 6

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Other Expenses [Abstract]
Accretion Expense	$ 0.1	$ 0.1	$ 0.1	$ 0.3
General Insurance Expense	0.8	0.3	1.3	0.7
Advertising Expense	1.2	2.3	2.1	3
Technology Services Costs	2.8	1.3	5.7	2.8
Supplies and Postage Expense	0.5	0.3	1.1	0.6
Clearance Fees	0.3	0.3	0.7	0.5
Taxes, Miscellaneous	1.2	1.1	2.3	2.1
Other Expenses	2.5	1.7	4.6	3.7
Other Cost and Expense, Operating	$ 9.4	$ 7.4	$ 17.9	$ 13.7

Accumulated Other Comprehensi69

Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (24.8)		$ (24.8)		$ (24.6)
Other comprehensive loss	0.7	$ (1.3)	(0.2)	$ (6.7)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(20.3)		(20.3)		(20.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(0.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(4.5)		(4.5)		(4.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (24.8)		(24.8)		$ (24.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(0.2)
Other comprehensive loss			$ (0.2)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Deferred Tax Assets, Valuation Allowance	$ 3.6		$ 3.6		$ 3.6
Income (Loss) from Continuing Operations before Income Taxes, Domestic					$ (9.7)	$ 16.5	$ (18.4)
Deferred Tax Liabilities, Gross	4.5		4.5
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	1.3		1.3
Income Tax Expense (Benefit)	$ 3.3	$ 5.5	$ 5.4	$ 8.8
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	23.00%	28.00%	24.00%	27.00%

Acquisitions Acquisitions (Deta

Acquisitions Acquisitions (Details) $ in Millions	6 Months Ended
	Mar. 31, 2017USD ($)
Finite-Lived Intangible Asset, Useful Life	5 years
ICAP [Member] [Member]
Business Combination, Consideration Transferred	$ 6

Segment Analysis (Details)

Segment Analysis (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 5,460.8	$ 3,708.9	$ 11,535.2	$ 7,108.8
Operating revenues	195.8	166.1	381.3	317.4
Net operating revenues	123.9	112.9	238.2	215.6
Net Segment Contribution	97.2	81.4	190.6	166.9
Segment Income	53.9	46.7	104.1	98.1
Costs not allocated to operating segments	39.6	26.7	81.4	66
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	14.3	20	22.7	32.1
Assets	6,528.6		6,528.6		$ 5,950.3
Commercial Hedging [Member]
Segment Reporting Information [Line Items]
Revenues	62.7	54.7	120.2	110.1
Operating revenues	62.7	54.7	120.2	110.1
Net operating revenues	50.5	43.6	96.1	87.9
Net Segment Contribution	36.9	30.5	70.3	62.2
Segment Income	18.7	13.8	34.1	28.8
Assets	1,654		1,654		1,637.5
Global Payments [Member]
Segment Reporting Information [Line Items]
Revenues	21.5	17.4	44.6	35.7
Operating revenues	21.5	17.4	44.6	35.7
Net operating revenues	19.1	15.5	39.7	31.8
Net Segment Contribution	15.3	12.4	31.7	25.4
Segment Income	11.7	9.3	24.9	19.3
Assets	172.4		172.4		191.4
Securities Segment [Member]
Segment Reporting Information [Line Items]
Revenues	37.9	45.6	75.3	94.4
Operating revenues	37.9	45.6	75.3	94.4
Net operating revenues	24.1	31.8	49.2	67.8
Net Segment Contribution	18.9	25	38.7	54.5
Segment Income	11.7	18.2	24.6	40.1
Assets	2,611		2,611		2,130.7
Physical Commodities [Member]
Segment Reporting Information [Line Items]
Revenues	5,276.2	3,550.7	11,174.9	6,805.2
Operating revenues	11.2	7.9	21	13.8
Net operating revenues	9	6.8	17.1	11.5
Net Segment Contribution	6.5	5.3	12.3	8.7
Segment Income	3.9	1.9	6.9	2.9
Assets	309.1		309.1		258
Clearing and Execution Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	64.2	33.3	127.8	63.1
Operating revenues	64.2	33.3	127.8	63.1
Net operating revenues	25.4	10.4	49.5	20.8
Net Segment Contribution	19.6	8.2	37.6	16.1
Segment Income	7.9	3.5	13.6	7
Assets	1,651.2		1,651.2		1,617.4
Corporate [Member]
Segment Reporting Information [Line Items]
Revenues	(1.7)	7.2	(7.6)	0.3
Operating revenues	(1.7)	7.2	(7.6)	0.3
Net operating revenues	(4.2)	$ 4.8	(13.4)	$ (4.2)
Assets	$ 130.9		$ 130.9		$ 115.3