StoneX (SNEX) 10-Q 7 Feb 18 2018 Q1 Quarterly report Financial data

DEI

DEI - shares	3 Months Ended
	Dec. 31, 2017	Feb. 05, 2018
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	Dec. 31, 2017
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		18,844,502
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	Dec. 31, 2017	Sep. 30, 2017
ASSETS
Cash and cash equivalents	$ 321.8	$ 314.9
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)	464.4	518.8
Collateralized transactions:
Securities purchased under agreements to resell	559.5	406.6
Securities Borrowed	95.7	86.6
Broker-dealers, clearing organizations and counterparties (including $53.7 and $204.7 at fair value at December 31, 2017 and September 30, 2017, respectively)	2,628.2	2,625.1
Receivables from customers, net	254.4	232.7
Notes receivable, net	10.6	10.6
Income taxes receivable	0.5	0.4
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $3.4 and $19.4 at December 31, 2017 and September 30, 2017, respectively)	2,055.9	1,731.8
Physical commodities inventory, net (including $142.7 and $73.2 at fair value at December 31, 2017 and September 30, 2017, respectively)	244.7	124.8
Deferred income taxes, net	22.9	42.6
Property and equipment, net	40.3	38.7
Goodwill and intangible assets, net	57.6	59.4
Other assets	52.4	50.4
Total assets	6,808.9	6,243.4
Liabilities:
Accounts payable and other accrued liabilities (including $1.0 at fair value at September 30, 2017)	111.5	135.6
Payables to:
Customers	3,063.8	3,072.9
Broker-dealers, clearing organizations and counterparties (including $1.1 and $4.8 at fair value at December 31, 2017 and September 30, 2017), respectively	197.1	125.7
Lenders under loans	422.9	230.2
Income taxes payable	7.9	7.3
Collateralized transactions:	1,759.2	1,504.2
Securities sold under agreements to repurchase	1,650.4	1,393.1
Securities Loaned	108.8	111.1
Financial instruments sold, not yet purchased, at fair value	803.3	717.6
Total liabilities	6,365.7	5,793.5
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; 20,931,720 issued and 18,809,763 outstanding at December 31, 2017 and 20,855,243 issued and 18,733,286 outstanding at September 30, 2017	0.2	0.2
Common stock in treasury, at cost - 2,121,957 shares at December 31, 2017 and September 30, 2017	(46.3)	(46.3)
Additional paid-in capital	261.4	259
Retained earnings	254.6	261.5
Accumulated other comprehensive loss, net	(26.7)	(24.5)
Total stockholders' equity	443.2	449.9
Total liabilities and stockholders' equity	$ 6,808.9	$ 6,243.4

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	$ 16.5	$ 54.5
Dep and rec -exch clear org - fair value	232.5	0
Dep and rec -b/d - fair value	53.7	204.7
Physical commodities inventory at fair value	142.7	73.2
Collateral that can be sold or repledged	3.4	19.4
Accounts pay and other accrued - fair value	0	1
Payables to b/d - fair value	$ 1.1	$ 4.8
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	20,931,720	20,855,243
Common stock - outstanding	18,809,763	18,733,286
Treasury stock - shares	2,121,957	2,121,957

Condensed Consolidated Income S

Condensed Consolidated Income Statements - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Sales of physical commodities	$ 7,714.4	$ 5,896
Trading gains, net	85.8	83
Commission and clearing fees	77.8	69.2
Consulting and management fees	16.6	15.7
Interest income	24	10.4
Other income	0	0.1
Total revenues	7,918.6	6,074.4
Cost of sales of physical commodities	7,706	5,888.9
Operating revenues	212.6	185.5
Transaction-based clearing expenses	36.9	33.6
Introducing broker commissions	31.1	28.7
Interest expense	14.3	8.9
Net operating revenues	130.3	114.3
Compensation and other expenses:
Compensation and benefits	77.2	70.6
Communication and data services	8.2	8.9
Occupancy and equipment rental	4.1	3.4
Professional fees	4.7	4.8
Travel and business development	3.5	3.6
Non-trading technology and support	3.1	2.9
Depreciation and amortization	2.7	2.4
Communications	1.4	1.2
Bad debts	1.1	2.5
Other	5.7	5.6
Total compensation and other expenses	111.7	105.9
Income before tax	18.6	8.4
Income tax expense	25.5	2.1
Net income	$ (6.9)	$ 6.3
Earnings per share:
Basic	$ (0.37)	$ 0.34
Diluted	$ (0.37)	$ 0.34
Weighted-average number of common shares outstanding:
Basic	18,419,072	18,248,244
Diluted	18,419,072	18,484,995

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ (6.9)	$ 6.3
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	(2.2)	(0.9)
Reclassification of adjustments included in net income [Abstract]
Other comprehensive income (loss)	(2.2)	(0.9)
Comprehensive income	$ (9.1)	$ 5.4

Condensed Consolidated Cash Flo

Condensed Consolidated Cash Flows Statements - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ (6.9)	$ 6.3
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	2.7	2.4
Bad debts	1.1	2.5
Deferred Income Tax Expense (Benefit)	19.7	(3.5)
Amortization of debt issuance costs and debt discount	0.3	1.2
Amortization of stock-based compensation	1.6	0.8
Loss on sale of property and equipment	0.6	0.3
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	24.2	148.3
Securities purchased under agreements to resell	(153)	(160.9)
Increase (Decrease) in Securities Borrowed	(9)	0
Deposits and receivables from exchange-clearing organizations	(14.2)	(151.4)
Receivables from customers, net	(54)	(11.4)
Notes receivable, net	0	(1.3)
Income taxes receivable	(0.4)	(1.3)
Financial instruments owned, at fair value	(292)	(129.6)
Physical commodities inventory	(121)	(88.6)
Other assets	(2.5)	(7.8)
Accounts payable and other accrued liabilities	(20.4)	(7.6)
Payables to customers	26.7	(35.3)
Payables to broker-dealers, clearing organizations and counterparties	69.6	(148.1)
Income taxes payable	0.9	4
Payables under repurchase agreements	257.4	399.1
Increase (Decrease) in Securities Loaned Transactions	(2.3)	0
Financial instruments sold, not yet purchased, at fair value	86.1	65.9
Net cash (used in) provided by operating activities	(186)	(116.6)
Cash flows from investing activities:
Cash paid for acquisitions, net	0	6
Purchase of property and equipment	3.2	3
Net cash used in investing activities	(3.2)	(9)
Cash flows from financing activities:
Net change in payable to lenders under loans	192.9	130
Repayments of Unsecured Debt	0	(45.5)
Payments of note payable	0.2	0.2
Deferred payments on acquisitions	2.3	0
Debt issuance costs	0.1	0.1
Exercise of stock options	1.5	2
Withholding taxes on stock option exercises	(0.8)	0
Excess income tax benefit on stock options and awards	0	0.6
Net cash provided by financing activities	191	86.8
Effect of exchange rates on cash and cash equivalents	5.1	1.4
Net (decrease) increase in cash and cash equivalents	6.9	(37.4)
Cash and cash equivalents at beginning of period	314.9	316.2
Cash and cash equivalents at end of period	321.8	278.8
Supplemental disclosure of cash flow information:
Cash paid for interest	11.3	7.6
Income taxes paid, net of cash refunds	5.3	2.4
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	0	$ 6
Additional consideration payable related to acquisitions, net	$ 0.1

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Stockholders' Equity - 3 months ended Dec. 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, 2017	$ 449.9	$ 0.2	$ (46.3)	$ 259	$ 261.5	$ (24.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(6.9)				(6.9)
Other comprehensive loss	(2.2)					(2.2)
Exercise of stock options	0.8			0.8
Share-based Compensation	1.6			1.6
Balances as of end of period at Dec. 31, 2017	$ 443.2	$ 0.2	$ (46.3)	$ 261.4	$ 254.6	$ (26.7)

Basis of Presentation and Conso

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Notes)	3 Months Ended
	Dec. 31, 2017
Basis of Presentation and Consolidation [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Basis of Presentation and Consolidation and Accounting Standards Adopted 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 asset 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 Company’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 unaudited condensed consolidated balance sheet as of September 30, 2017 , which has been derived from audited consolidated 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 consolidated 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, 2017 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 consolidated 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, 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. Reclassifications During the quarter ended December 31, 2017, the Company separately classified non-trading technology and support costs that were previously included within ‘Other’ on the condensed consolidated income statements. Additionally, during the quarter ended December 31, 2017, the Company separately classified communications related expenses separately from trading systems and market information related costs. In performing these reclassifications, the Company has made immaterial, retrospective adjustments to conform to our current period presentation. For the three months December 31, 2016, ‘Other’ expenses included $2.9 million of expenses that are now included within ‘Non-trading technology and support’ on the condensed consolidated income statements. For the three months ended December 31, 2016, ‘Trading systems and market information’ included $1.2 million of expenses that are now included within ‘Communications’ on the condensed consolidated income statements. Accounting Standards Adopted In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”), which simplifies several aspects of the accounting for share-based payment transactions. Under ASU 2016-09, excess tax benefits and tax deficiencies are recognized as income tax expense or benefit in the income statement instead of additional paid in capital. ASU 2016-09 also provides entities with the option to elect an accounting policy to estimate forfeitures of stock-based awards over the service period (current GAAP) or account for forfeitures when they occur. Under ASU 2016-09, previously unrecognized excess tax benefits should be recognized using a modified retrospective transition. In addition, amendments requiring recognition of excess tax benefits and tax deficiencies in the income statement, as well as changes in the computation of weighted-average diluted shares outstanding, should be applied prospectively. ASU 2016-09 is effective for and was adopted by the Company in the first quarter of 2018 and the impact of the adoption resulted in the following: • During the three months ended December 31, 2017, the Company recognized excess tax benefits from stock-based compensation of $0.2 million within income tax expense on the condensed consolidated income statement and within net income on the condensed consolidated cash flow statement. Prior to adoption, the tax effect of stock-based awards would have been recognized in additional paid-in-capital on the condensed consolidated balance sheets and separately stated in the financing activities in the condensed consolidated cash flow statements. The Company has elected to adopt this guidance prospectively. • The Company has elected to estimate forfeitures of stock-based awards as they occur. The Company elected to account for forfeitures as they occur using a modified retrospective transition method. The adoption of this guidance did not have a material impact on our condensed consolidated financial statements. • The excess tax benefits from the assumed proceeds available to repurchase shares were excluded in the computation of diluted earnings per share for the three months ended December 31, 2017. The Company has elected to adopt this guidance prospectively. • For the three months ended December 31, 2017, the Company has classified as a financing activity in the condensed consolidated cash flow statement $0.8 million of cash paid to taxing authorities for restricted stock shares withheld to satisfy statutory income tax withholding obligations. The retrospective application of this guidance had no impact on the condensed consolidated cash flow statement for the three months ended December 31, 2016. In July 2015, the FASB issued ASU No. 2015-11, “Simplifying the Measurement of Inventory (Topic 330).” Under ASU 2015-11, inventory that is measured using the first-in, first-out (FIFO), specific identification, or average cost methods should be measured at the lower of cost or net realizable value. This ASU does not impact inventory measurement under the last-in, first-out (LIFO) or retail inventory methods. For public companies, this ASU is effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. The amendments from this update are to be applied prospectively. The Company adopted this ASU prospectively on the effective date of October 1, 2017. The adoption of this ASU has not had a material impact on our condensed consolidated financial statements.

Earnings per Share (Notes)

Earnings per Share (Notes)	3 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings (loss) per Share The Company presents basic and diluted earnings (loss) 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 (loss) 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 (loss) 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 (loss) income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted earnings (loss) per share computations for the periods presented below. Three Months Ended December 31, (in millions, except share amounts) 2017 2016 Numerator: Net (loss) income $ (6.9 ) $ 6.3 Less: Allocation to participating securities — (0.1 ) Net (loss) income allocated to common stockholders $ (6.9 ) $ 6.2 Denominator: Weighted average number of: Common shares outstanding 18,419,072 18,248,244 Dilutive potential common shares outstanding: Share-based awards — 236,751 Diluted weighted-average common shares 18,419,072 18,484,995 The dilutive effect of share-based awards is reflected in diluted earnings (loss) 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 489,721 and 914,453 shares of common stock for the three months ended December 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)	3 Months Ended
	Dec. 31, 2017
Assets and Liabilities, at Fair Value [Abstract]
Fair Value Disclosures [Text Block]	Assets and Liabilities, at Fair Value Fair value is defined by U.S. GAAP as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between willing market participants on the measurement date. Fair value is a market-based measure considered from the perspective of a market participant rather than an entity-specific measure. Therefore, even when market assumptions are not readily available, the Company is required to develop a set of assumptions that reflect those that market participants would use in pricing the asset or liability at the measurement date. The Company uses prices and inputs that are current as of the measurement date, including periods of market dislocation. In periods of market dislocation, the observability of prices and inputs may be reduced for many securities. This condition could cause a security to be reclassified to a lower level within the fair value hierarchy. The Company has designed independent price verification controls and periodically performs such controls to ensure the reasonableness of such values. In accordance with FASB ASC 820, Fair Value Measurement, the Company groups its assets and liabilities measured at fair value in three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. These levels are: Level 1 - Valuation is based upon unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 1 consists of financial assets and liabilities whose fair values are estimated using quoted market prices. Level 2 - Valuation is based upon 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. Included in Level 2 are those financial assets and liabilities for which fair values are estimated using models or other valuation methodologies. These models are primarily industry-standard models that consider various observable inputs, including time value, yield curve, volatility factors, observable current market and contractual prices for the underlying financial instruments, as well as other relevant economic measures. Level 3 - Valuation is generated from prices or valuation techniques that require an input that is both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Level 3 comprises financial assets and liabilities whose fair value is estimated based on internally developed models or methodologies utilizing significant inputs that are not readily observable from objective sources. Financial and nonfinancial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). A market is active if there are sufficient transactions on an ongoing basis to provide current pricing information for the asset or liability, pricing information is released publicly, and price quotations do not vary substantially either over time or among market makers. Observable inputs reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the reporting entity. The guidance requires the Company to consider counterparty credit risk of all parties of outstanding derivative instruments that would be considered by a market participant in the transfer or settlement of such contracts (exit price). The Company’s exposure to credit risk on derivative financial instruments relates to the portfolio of OTC derivative contracts as all exchange-traded contracts held can be settled on an active market with a credit guarantee by the respective exchange. The Company requires each counterparty to deposit margin collateral for all OTC instruments and is also required to deposit margin collateral with counterparties. The Company has assessed the nature of these deposits and used its discretion to adjust each based on the underlying credit considerations for the counterparty and determined that the collateral deposits minimize the exposure to counterparty credit risk in the evaluation of the fair value of OTC instruments as determined by a market participant. Fair value of financial and nonfinancial assets and liabilities that are carried on the Condensed Consolidated Balance Sheets at fair value on a recurring basis Cash and cash equivalents reported at fair value on a recurring basis includes 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 reported at fair value on a recurring basis include the value of pledged investments, primarily U.S. Treasury obligations and commodities warehouse receipts. Deposits with and receivables from broker-dealers, clearing organizations and counterparties and payable to customers and broker-dealers, clearing organizations and counterparties include the value of pledged investments, primarily U.S. Treasury obligations and foreign government obligations. These balances also include the fair value of exchange-traded options on futures and exchange-cleared OTC swaps and options determined by quoted prices on the applicable exchange. Financial instruments owned and sold, not yet purchased include the value of common and preferred stock, American Depository Receipts (“ADRs”), and Global Depository Receipts (“GDRs”), exchangeable foreign ordinary equities, ADRs, and GDRs, corporate and municipal debt obligations, U.S. Treasury obligations, U.S. government agency obligations, foreign government obligations, agency mortgage-backed obligations, asset-backed obligations, derivative financial instruments, commodities warehouse receipts, exchange firm common stock, and mutual funds and investments in managed funds. The fair value of exchange firm common stock is determined by quoted market prices, and the fair value of exchange memberships is determined by recent sale transactions. Physical commodities inventory recorded at fair value on a recurring basis includes precious metals that are a part of the trading activities of a regulated broker-dealer subsidiary and is recorded at fair value using spot prices. Physical commodities inventory also includes agricultural commodities that are a part of the trading activities of a non-broker dealer subsidiary and are also recorded at net realizable value using spot prices. Precious metals inventory held by subsidiaries that are not broker-dealers are valued at fair value on a non-recurring basis. 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 as of December 31, 2017 and September 30, 2017 . Cash equivalents, securities, commodities warehouse receipts, physical commodities inventory, derivative financial instruments and contingent liabilities are carried at fair value, on a recurring basis, and are classified and disclosed into three levels in the fair value hierarchy. The following section describes the valuation methodologies used by the Company to measure classes of financial instruments at fair value and specifies the level within the fair value hierarchy where various financial instruments are classified. The Company uses quoted prices in active markets, where available, and classifies such instruments within Level 1 of the fair value hierarchy. Examples include U.S. Treasury obligations, commodities warehouse receipts, some common and preferred stock, ADRs, and GDRs, some exchangeable foreign ordinary equities, ADRs, and GDRs, some corporate and municipal obligations, physical precious metals, agricultural, and energy commodities, equity investments in exchange firms, mutual funds, as well as futures and options on futures contracts traded on national exchanges. The fair value of exchange memberships is determined by recent sale transactions and is included within Level 1. When instruments are traded in secondary markets and observable prices are not available for substantially the full term, the Company generally relies on internal valuation techniques or prices obtained from third-party pricing services or brokers or a combination thereof, and accordingly, classified these instruments as Level 2. Examples include U.S. government agency obligations, agency-mortgage backed obligations, asset-backed obligations, foreign government obligations, some common and preferred stock, ADRs, and GDRs, certain exchangeable foreign ordinary equities, ADRs, and GDRs, OTC commodity and foreign exchange forwards, swaps, and options, OTC firm purchase and sale commitments related to precious metals commodities, and OTC firm purchase and sale commitments related to the Company’s agricultural and energy commodities. Derivatives without a quoted price in an active market and derivatives executed OTC are valued using internal valuation techniques, including pricing models which utilize significant inputs observable to market participants. The valuation techniques and inputs depend on the type of derivative and the nature of the underlying instrument. The key inputs depend upon the type of derivative and the nature of the underlying instrument and include interest yield curves, foreign exchange rates, commodity prices, volatilities and correlation. These derivative instruments are included within Level 2 of the fair value hierarchy. With the exception of certain derivative instruments, financial instruments owned and sold are primarily valued using third party pricing sources. Third party vendors compile prices from various sources and often apply matrix pricing for similar securities when no prices are observable. The Company reviews the pricing methodologies provided by the various vendors in order to determine if observable market information is being used, versus unobservable inputs. When evaluating the propriety of an internal trader price compared with vendor prices, considerations include the range and quality of vendor prices. Trader or broker prices are used to ensure the reasonableness of a vendor price; however valuing financial instruments involves judgments acquired from knowledge of a particular market. If a trader asserts that a vendor or market price is not reflective of market value, justification for using the trader price, including recent sales activity where possible, must be provided to and approved by the appropriate levels of management. Financial instruments owned and sold that are valued using third party pricing sources are included within either Level 1 or Level 2 of the fair value hierarchy based upon the observability of the inputs used and the level of activity in the market. Level 3 comprises financial assets and liabilities whose fair value is estimated based on internally developed models or methodologies utilizing significant inputs that are not readily observable from objective sources. Included in Level 3 are some common stock and ADRs, some corporate and municipal obligations, and contingent liabilities. Level 3 assets and liabilities are valued using an income approach based upon management developed discounted cash flow projections, which are an unobservable input. The fair value estimates presented herein are based on pertinent information available to management as of December 31, 2017 and September 30, 2017 . 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 financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein. 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 December 31, 2017 by level in the fair value hierarchy. December 31, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificate of deposits $ 4.7 $ — $ — $ — $ 4.7 Commodities warehouse receipts 14.9 — — — 14.9 U.S. Treasury obligations 1.6 — — — 1.6 Securities and other assets segregated under federal and other regulations 16.5 — — — 16.5 U.S. Treasury obligations 219.1 — — — 219.1 "To be announced" (TBA) and forward settling securities — 1.7 — (0.6 ) 1.1 Foreign government obligations — 6.2 — — 6.2 Derivatives 3,068.1 188.7 — (3,429.5 ) (172.7 ) Deposits with and receivables from broker-dealers, clearing organization and counterparties 3,287.2 196.6 — (3,430.1 ) 53.7 Common and preferred stock, ADRs, and GDRs 30.5 3.4 0.1 — 34.0 Exchangeable foreign ordinary equities, ADRs, and GDRs 9.0 1.1 — — 10.1 Corporate and municipal bonds 45.1 0.6 — — 45.7 U.S. Treasury obligations 76.8 — — — 76.8 U.S. government agency obligations — 587.7 — — 587.7 Foreign government obligations — 11.3 — — 11.3 Agency mortgage-backed obligations — 1,053.4 — — 1,053.4 Asset-backed obligations — 21.6 — — 21.6 Derivatives 1.4 1,577.8 — (1,444.3 ) 134.9 Commodities leases — 178.9 — (168.5 ) 10.4 Commodities warehouse receipts 56.1 — — — 56.1 Exchange firm common stock 8.9 — — — 8.9 Mutual funds and other 5.0 — — — 5.0 Financial instruments owned 232.8 3,435.8 0.1 (1,612.8 ) 2,055.9 Physical commodities inventory, net 142.7 — — — 142.7 Total assets at fair value $ 3,683.9 $ 3,632.4 $ 0.1 $ (5,042.9 ) $ 2,273.5 Liabilities: TBA and forward settling securities — 1.7 — (0.6 ) 1.1 Derivatives 3,169.6 212.5 — (3,382.1 ) — Payable to broker-dealers, clearing organizations and counterparties 3,169.6 214.2 — (3,382.7 ) 1.1 Common and preferred stock, ADRs, and GDRs 48.6 1.2 — — 49.8 Exchangeable foreign ordinary equities, ADRs, and GDRs 10.2 — — — 10.2 Corporate and municipal bonds 0.3 — — — 0.3 U.S. Treasury obligations 404.6 — — — 404.6 U.S. government agency obligations — 35.5 — — 35.5 Agency mortgage-backed obligations — 3.9 — — 3.9 Derivatives — 1,634.6 — (1,385.3 ) 249.3 Commodities leases — 186.4 — (136.7 ) 49.7 Financial instruments sold, not yet purchased 463.7 1,861.6 — (1,522.0 ) 803.3 Total liabilities at fair value $ 3,633.3 $ 2,075.8 $ — $ (4,904.7 ) $ 804.4 (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, 2017 by level in the fair value hierarchy. September 30, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificates of deposits $ 3.8 $ — $ — $ — $ 3.8 Commodities warehouse receipts 21.0 — — — 21.0 U.S. Treasury obligations 33.5 — — — 33.5 Securities and other assets segregated under federal and other regulations 54.5 — — — 54.5 U.S. Treasury obligations 244.7 — — — 244.7 "To be announced" (TBA) and forward settling securities — 8.8 — — 8.8 Foreign government obligations — 6.4 — — 6.4 Derivatives 2,608.6 289.1 — (2,952.9 ) (55.2 ) Deposits with and receivables from broker-dealers, clearing organizations, and counterparties 2,853.3 304.3 — (2,952.9 ) 204.7 Common and preferred stock, ADRs, and GDRs 31.2 3.4 0.1 — 34.7 Exchangeable foreign ordinary equities, ADRs, and GDRs 9.2 1.2 — — 10.4 Corporate and municipal bonds 28.2 0.9 — — 29.1 U.S. Treasury obligations 60.0 — — — 60.0 U.S. government agency obligations — 368.9 — — 368.9 Foreign government obligations — 10.2 — — 10.2 Agency mortgage-backed obligations — 920.9 — — 920.9 Asset-backed obligations — 47.3 — — 47.3 Derivatives 1.3 1,413.4 — (1,252.6 ) 162.1 Commodities leases — 174.1 — (138.7 ) 35.4 Commodities warehouse receipts 38.5 — — — 38.5 Exchange firm common stock 8.3 — — — 8.3 Mutual funds and other 6.0 — — — 6.0 Financial instruments owned 182.7 2,940.3 0.1 (1,391.3 ) 1,731.8 Physical commodities inventory, net 73.2 — — — 73.2 Total assets at fair value $ 3,167.5 $ 3,244.6 $ 0.1 $ (4,344.2 ) $ 2,068.0 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.0 $ — $ 1.0 TBA and forward settling securities — 4.9 — (0.1 ) 4.8 Derivatives 2,476.2 292.8 — (2,769.0 ) — Payable to broker-dealers, clearing organizations and counterparties 2,476.2 297.7 — (2,769.1 ) 4.8 Common and preferred stock, ADRs, and GDRs 33.7 0.7 — — 34.4 Exchangeable foreign ordinary equities, ADRs, and GDRs 10.3 0.2 — — 10.5 Corporate and municipal bonds 0.3 — — — 0.3 U.S. Treasury obligations 285.9 — — — 285.9 U.S. government agency obligations — 27.9 — — 27.9 Agency mortgage-backed obligations — 0.1 — — 0.1 Derivatives — 1,427.2 — (1,110.2 ) 317.0 Commodities leases — 191.1 — (149.6 ) 41.5 Financial instruments sold, not yet purchased 330.2 1,647.2 — (1,259.8 ) 717.6 Total liabilities at fair value $ 2,806.4 $ 1,944.9 $ 1.0 $ (4,028.9 ) $ 723.4 (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 December 31, 2017 and September 30, 2017 are summarized below: (in millions) December 31, 2017 September 30, 2017 Total Level 3 assets $ 0.1 $ 0.1 Level 3 assets for which the Company bears economic exposure $ 0.1 $ 0.1 Total assets $ 6,808.9 $ 6,243.4 Total assets at fair value $ 2,273.5 $ 2,068.0 Total Level 3 assets as a percentage of total assets — % — % Level 3 assets for which the Company bears economic exposure as a percentage of total assets — % — % Total Level 3 assets as a percentage of total financial assets at fair value — % — % 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 months ended December 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 December 31, 2017 . Level 3 Financial Assets and Financial Liabilities For the Three Months Ended December 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.1 $ — $ — $ — $ — $ — $ 0.1 $ 0.1 $ — $ — $ — $ — $ — $ 0.1 Level 3 Financial Assets and Financial Liabilities For the Three Months Ended December 31, 2016 (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 $ — $ — $ — $ — $ — $ 0.8 The Company is required to make additional future cash payments based on certain financial performance measures of an acquired business. The Company was required to remeasure the fair value of contingent consideration arrangements on a recurring basis. As of September 30, 2017, the Company had classified its liability for the contingent consideration within Level 3 of the fair value hierarchy because the fair value was determined using significant unobservable inputs, which included projected cash flows. The estimated fair value of the earn-outs was based upon management-developed earnings forecasts for the remaining contingency period, which was a Level 3 input in the fair value hierarchy. The fair value of the contingent consideration increased by less than $0.1 million during the three months ended December 31, 2017 and 2016 with the corresponding amount classified as ‘other’ in the condensed consolidated income statements. The contingency period for the contingent consideration arrangements ended as of December 31, 2017. The accrued balance of $1.0 million is included within ‘accounts payable and other accrued liabilities’ on the condensed consolidated balance sheet at an amount approximating fair value with the final payment due in February 2018. 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 months ended December 31, 2017 and 2016 . Additional disclosures about the fair value of financial instruments that are not carried on the Condensed Consolidated Balance Sheets at fair value Many, but not all, of the financial instruments that the Company holds are recorded at fair value in the Condensed Consolidated Balance Sheets. The following represents financial instruments in which the ending balance at December 31, 2017 and September 30, 2017 was not carried at fair value in accordance with U.S. GAAP on our Condensed Consolidated Balance Sheets: Short-term financial instruments: The carrying value of short-term financial instruments, including cash and cash equivalents, cash segregated under federal and other regulations, securities purchased under agreements to re-sell and securities sold under agreements to re-purchase, and securities borrowed and loaned are recorded at amounts that approximate the fair value of these instruments due to their short-term nature and level of collateralization. These financial instruments generally expose us to limited credit risk and have no stated maturities or have short-term maturities and carry interest rates that approximate market rates. Under the fair value hierarchy, cash and cash equivalents and cash segregated under federal and other regulations are classified as Level 1. Securities purchased under agreements to re-sell and securities sold under agreements to re-purchase, and securities borrowed and loaned are classified as Level 2 under the fair value hierarchy as they are generally overnight and are collateralized by common stock, U.S. Treasury obligations, U.S. government agency obligations, agency mortgage-backed obligations, and asset-backed obligations. Receivables and other assets: R eceivables from broker-dealers, clearing organizations, and counterparties, receivables from customers, net, notes receivables, net and certain other assets are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Payables: P ayables to customers and payables to brokers-dealers, clearing organizations, and counterparties are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Lender under loans : Payables to lenders under loans carry variable rates of interest and thus approximate fair value and are classified as Level 2 under the fair value hierarchy.

Financial Instruments with Off-

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Notes)	3 Months Ended
	Dec. 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 December 31, 2017 and September 30, 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 December 31, 2017 . The total financial instruments sold, not yet purchased of $803.3 million and $717.6 million as of December 31, 2017 and September 30, 2017 , respectively, includes $249.3 million and $317.0 million for derivative contracts, respectively, which represented a liability to the Company based on their fair values as of December 31, 2017 and September 30, 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 broker-dealers, clearing organizations and counterparties’, ‘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. Listed below are the fair values of the Company’s derivative assets and liabilities as of December 31, 2017 and September 30, 2017 . Assets represent net unrealized gains and liabilities represent net unrealized losses. December 31, 2017 September 30, 2017 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 2,515.9 $ 2,660.1 $ 2,094.2 $ 1,975.0 OTC commodity derivatives 1,208.9 1,270.9 1,084.0 1,110.3 Exchange-traded foreign exchange derivatives 53.0 32.3 66.0 52.0 OTC foreign exchange derivatives 533.4 530.8 618.5 609.8 Exchange-traded interest rate derivatives 203.1 234.8 228.4 203.6 OTC interest rate derivatives 24.2 24.2 — — Exchange traded equity index derivatives 297.5 263.6 221.3 245.4 TBA and forward settling securities 1.7 1.7 8.8 4.9 Gross fair value of derivative contracts 4,837.7 5,018.4 4,321.2 4,201.0 Impact of netting and collateral (4,874.4 ) (4,768.0 ) (4,205.5 ) (3,879.2 ) Total fair value included in ‘Deposits with and receivables from broker-dealers, clearing organizations, and counterparties’ $ (171.6 ) $ (46.4 ) Total fair value included in ‘Financial instruments owned, at fair value’ $ 134.9 $ 162.1 Total fair value included in ‘Payables to broker-dealers, clearing organizations and counterparties $ 1.1 $ 4.8 Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’ $ 249.3 $ 317.0 (1) As of December 31, 2017 and September 30, 2017 , the Company’s derivative contract volume for open positions were approximately 6.8 million and 6.1 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 exchange-traded position. 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 institutional fixed income business. The fair value on these transactions are recorded in deposits with and receivables from 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 December 31, 2017 and September 30, 2017 , these transactions are summarized as follows: December 31, 2017 September 30, 2017 (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) $ 0.9 $ 525.4 $ — $ 51.3 Unrealized loss on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (0.1 ) $ 203.1 $ (2.9 ) $ 1,236.8 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 0.5 $ (554.8 ) $ 5.8 $ (1,881.9 ) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (1.4 ) $ (1,041.7 ) $ (0.1 ) $ (404.1 ) Unrealized gain (loss) on forward settling securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 0.3 $ 240.2 $ (2.0 ) $ 882.9 Unrealized (loss) gain on forward settling securities sold within receivables from and payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.2 ) $ (107.6 ) $ 3.0 $ (590.2 ) (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 months ended December 31, 2017 and 2016 in accordance with the Derivatives and Hedging Topic of the ASC. The net gains set forth below are included in ‘Cost of sales of physical commodities’ and ‘Trading gains, net’ in the condensed consolidated income statements. Three Months Ended December 31, (in millions) 2017 2016 Commodities $ 7.7 $ 4.9 Foreign exchange 2.3 1.2 Interest rate 0.4 (1.0 ) TBA and forward settling securities (0.4 ) 13.4 Net gains from derivative contracts $ 10.0 $ 18.5 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, OTC swaps and options and spot 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 December 31, 2017 and September 30, 2017 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)	3 Months Ended
	Dec. 31, 2017
Receivables from customers and notes receivable, net [Abstract]
Financing Receivables [Text Block]	Allowance for Doubtful Accounts The allowance for doubtful accounts related to receivables from customers was $7.6 million as of December 31, 2017 and September 30, 2017 . The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $48.1 million and $47.0 million as of December 31, 2017 and September 30, 2017 , respectively. During the three months ended December 31, 2017 , the Company recorded bad debt expense of $1.1 million , primarily related to the Company’s Physical Commodities segment. During the three months ended December 31, 2017 , the Company recorded an additional provision related to a bad debt in the physical coal business for amounts due to the Company from a coal supplier for demurrage and other charges related to contracts with delivery dates subsequent to September 30, 2017 . During the three months ended December 31, 2016, the Company recorded bad debt expense of $2.5 million . The provision for bad debts was primarily related to $2.5 million of LME Metals customer deficits in the Company’s Commercial Hedging segment.

Physical Commodities Inventory

Physical Commodities Inventory (Notes)	3 Months Ended
	Dec. 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) December 31, September 30, Physical Ag & Energy (1) $ 125.1 $ 65.1 Precious metals - held by broker-dealer subsidiary (2) 20.1 13.3 Precious metals - held by non-broker-dealer subsidiaries (3) 99.5 46.4 Physical commodities inventory $ 244.7 $ 124.8 (1) Physical Ag & Energy maintains agricultural commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, cocoa, cotton, 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. Physical Ag & Energy also maintains energy related inventory, primarily kerosene, which is valued at the lower of cost or net realizable value. (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 net realizable value. The Company has recorded lower of cost or net realizable adjustments for certain precious metals inventory of $1.3 million and $0.7 million as of December 31, 2017 and September 30, 2017 , respectively. The adjustments are included in ‘cost of sales of physical commodities’ in the condensed consolidated income statements.

Goodwill (Notes)

Goodwill (Notes)	3 Months Ended
	Dec. 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) December 31, September 30, Commercial Hedging $ 30.3 $ 30.7 Global Payments 6.3 6.3 Physical Commodities 2.4 2.4 Securities 6.9 7.7 Goodwill $ 45.9 $ 47.1 The Company recorded $1.2 million in foreign exchange revaluation adjustments on goodwill for the three months ended December 31, 2017 .

Intangible Assets - (Notes)

Intangible Assets - (Notes)	3 Months Ended
	Dec. 31, 2017
Intangible Assets [Abstract]
Intangible Assets Disclosure [Text Block]	Intangible Assets The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows (in millions): December 31, 2017 September 30, 2017 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization: Software programs/platforms 2.7 (2.5 ) 0.2 2.7 (2.5 ) 0.2 Customer base 20.0 (8.5 ) 11.5 20.0 (7.9 ) 12.1 Total intangible assets $ 22.7 $ (11.0 ) $ 11.7 $ 22.7 $ (10.4 ) $ 12.3 Amortization expense related to intangible assets was $0.6 million and $0.7 million for the three months ended December 31, 2017 and 2016 , respectively. As of December 31, 2017 , the estimated future amortization expense was as follows: (in millions) Fiscal 2018 (remaining nine months) $ 1.6 Fiscal 2019 2.2 Fiscal 2020 2.0 Fiscal 2021 1.9 Fiscal 2022 and thereafter 4.0 $ 11.7

Credit Facilities (Notes)

Credit Facilities (Notes)	3 Months Ended
	Dec. 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 $532.0 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: • $262.0 million facility available to INTL FCStone Inc. for general working capital requirements. • $75.0 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. • $170.0 million facility available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC, for financing traditional commodity financing arrangements and commodity repurchase agreements. The facility is subject to annual review and is guaranteed by INTL FCStone Inc. • $25.0 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Ltd, for short-term funding of margin to commodity exchanges. 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 Ltd may borrow up to approximately $25.0 million , collateralized by commodities 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, INTL FCStone Financial, Inc. may borrow up to $50.0 million , collateralized by commodities warehouse receipts, to facilitate U.S. commodity exchange deliveries of its customers, subject to certain terms and conditions of the credit agreement. There were $32.1 million and $23.0 million in borrowings outstanding under this credit facility at December 31, 2017, and September 30, 2017, respectively. The Company also has a secured, uncommitted loan facility, under which the Company’s wholly owned subsidiary, INTL FCStone Financial, Inc. may borrow for short term funding of firm and customer securities margin requirements, subject to certain terms and conditions of the agreement. The uncommitted amount available to be borrowed is not specified, and all requests for borrowing are subject to the sole discretion of the lender. The borrowings are secured by first liens on firm owned marketable securities or customer owned securities which have been pledged to us under a clearing arrangement. The amounts borrowed under the facilities are payable on demand. As of December 31, 2017, there were $37.0 million in borrowings outstanding under this credit facility and no borrowings outstanding as of September 30, 2017. 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 $100.0 million for short term funding of firm and customer securities margin requirements, subject to certain terms and conditions of the agreement. The borrowings are secured by first liens on firm owned marketable securities or customer owned securities which have been pledged to us under a clearing arrangement. The amounts borrowed under the facilities are payable on demand. There were $2.0 million and $11.0 million in borrowings outstanding under this credit facility at December 31, 2017, and September 30, 2017, respectively. 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%. The following table sets forth a listing of credit facilities, the current committed amounts as of the report date on the facilities, outstanding borrowings on the facilities, as well as indebtedness on a promissory note as of December 31, 2017 and September 30, 2017 : (in millions) Credit Facilities Amounts Outstanding Borrower Security Renewal / Expiration Date Total Commitment December 31, September 30, Committed Credit Facilities INTL FCStone Inc. Pledged shares of certain subsidiaries March 18, 2019 $ 262.0 $ 210.0 $ 150.0 INTL FCStone Financial, Inc. None April 5, 2018 75.0 36.5 — FCStone Merchants Services, LLC Certain commodities assets May 1, 2018 170.0 103.5 44.2 INTL FCStone Ltd. None November 7, 2018 25.0 — — $ 532.0 350.0 194.2 Uncommitted Credit Facilities INTL FCStone Financial, Inc. Commodities warehouse receipts and certain pledged securities n/a $ — $ 71.1 $ 34.0 INTL FCStone Ltd. Commodities warehouse receipts n/a $ — $ — $ — Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 1.8 2.0 Total indebtedness $ 422.9 $ 230.2 As reflected above, $270.0 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 December 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)	3 Months Ended
	Dec. 31, 2017
Commodity and Other Repurchase Agreements [Abstract]
Commodity and Other Repurchase Agreements and Collateralized Transactions	Securities and Commodity Financing Transactions The Company’s outstanding notes receivable in connection with repurchase agreements for agricultural and energy commodities, whereby the customers sell to the Company certain commodity inventory and agree to repurchase the commodity inventory at a future date at a fixed price were $1.8 million and $0.8 million as of December 31, 2017 and September 30 2017, respectively. 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 as collateralized financings at their contractual amounts plus accrued interest. The related interest is recorded in the 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. At December 31, 2017 , financial instruments owned, at fair value of $3.4 million were pledged as collateral under repurchase 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 consolidated balance sheet. The Company also has repledged securities borrowed and securities held on behalf of correspondent brokers to collateralize securities loaned agreements with a fair value of $101.9 million as of December 31, 2017 . In addition, as of December 31, 2017 , the Company pledged financial instruments owned, at fair value of $1,687.3 million as collateral for tri-party repurchase agreements. For these securities, the counterparties do not have the right to sell or repledge the collateral. At December 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 December 31, 2017 , was $819.0 million of which $472.8 million was used to cover securities sold short which are recorded in financial instruments sold, not yet purchased on the 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 December 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. The following tables provide the contractual maturities of gross obligations under repurchase and securities lending agreements as of December 31, 2017 and September 30, 2017 (in millions): December 31, 2017 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $1,121.4 $239.0 $290.0 — $1,650.4 Securities loaned 108.8 — — — 108.8 Gross amount of secured financing $1,230.2 $239.0 $290.0 $0.0 $1,759.2 September 30, 2017 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $640.2 $432.9 $320.0 — $1,393.1 Securities loaned 111.1 — — — 111.1 Gross amount of secured financing $751.3 $432.9 $320.0 — $1,504.2 The following table provides the underlying collateral types of the gross obligations under repurchase and securities lending agreements as of December 31, 2017 and September 30, 2017 (in millions): Securities sold under agreements to repurchase: December 31, 2017 September 30, 2017 U.S. Treasury obligations $ 3.2 $ 7.0 U.S. government agency obligations 358.2 332.6 Asset-backed obligations 75.0 36.4 Agency mortgage-backed obligations 1,214.0 1,017.1 Total securities sold under agreements to repurchase $ 1,650.4 $ 1,393.1 Securities loaned: Common stock 108.8 111.1 Total securities loaned 108.8 111.1 Gross amount of secured financing $ 1,759.2 $ 1,504.2

Commitments and Contingencies (

Commitments and Contingencies (Notes)	3 Months Ended
	Dec. 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 December 31, 2017 and September 30, 2017 , 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, 2017. Contractual Commitments 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 December 31, 2017 , the Company had $0.7 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)	3 Months Ended
	Dec. 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 December 31, 2017 , as follows: (in millions) As of December 31, 2017 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. SEC and Commodity Futures Trading Commission ("CFTC") United States Net capital $ 136.1 $ 74.2 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,256.9 $ 2,204.4 INTL FCStone Financial Inc. CFTC United States Secured funds $ 164.4 $ 147.8 INTL FCStone Financial Inc. SEC United States Customer reserve $ 12.0 $ — INTL FCStone Financial Inc. SEC United States PAB reserve $ 10.7 $ 10.2 INTL Custody & Clearing Soluntions Inc. SEC United States Net capital $ 1.7 $ 0.1 SA Stone Wealth Management Inc. SEC United States Net capital $ 4.2 $ 0.3 INTL FCStone Ltd (1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 191.8 $ 90.2 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 113.8 $ 113.8 INTL Netherlands BV (1) FCA United Kingdom Net capital $ 191.1 $ 90.2 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 12.6 $ 0.5 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 4.5 $ 0.2 INTL Gainvest S.A. CNV Argentina Net capital $ 3.0 $ 0.1 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.0 $ 0.9 INTL CIBSA S.A. CNV Argentina Net capital $ 1.7 $ 0.5 (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. 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 December 31, 2017 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Notes)

Other Expenses (Notes)	3 Months Ended
	Dec. 31, 2017
Other Expenses [Abstract]
Other Expenses [Text Block]	Other Expenses Other expenses for the three months ended December 31, 2017 and 2016 consisted of the following: Three Months Ended December 31, (in millions) 2017 2016 Insurance $ 0.6 $ 0.5 Advertising, meetings and conferences 0.9 0.9 Office supplies and printing 0.4 0.6 Other clearing related expenses 0.5 0.4 Other non-income taxes 1.2 1.1 Other 2.1 2.1 Total other expenses $ 5.7 $ 5.6

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) (Notes)	3 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Loss, Net 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 loss includes net actuarial losses from defined benefit pension plans and foreign currency translation adjustments. The following table summarizes the changes in accumulated other comprehensive loss, net for the three months ended December 31, 2017 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2017 $ (21.5 ) $ (3.0 ) $ (24.5 ) Other comprehensive loss, net of tax (2.2 ) — (2.2 ) Balances as of December 31, 2017 $ (23.7 ) $ (3.0 ) $ (26.7 )

Income Taxes (Notes)

Income Taxes (Notes)	3 Months Ended
	Dec. 31, 2017
Income Taxes [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes The income tax provision for interim periods is comprised of tax on ordinary income (loss) provided at the most recent estimated annual effective tax rate, adjusted for the tax effect of discrete items. Management uses an estimated annual effective tax rate based on the forecasted pretax income (loss) 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. Effects of the Tax Cuts and Jobs Act On December 22, 2017, the President of the United States signed and enacted into law H.R. 1, the Tax Cuts and Jobs Act (“the Tax Reform”). Among the significant changes to the U.S. Internal Revenue Code, the Tax Reform lowers the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. The Company will compute its income tax expense (benefit) for the September 30, 2018 tax year using a U.S. statutory tax rate of 24.5% . The 21% U.S. statutory tax rate will apply to fiscal years ending September 30, 2019 and thereafter. For the three months ended December 31, 2017, the Company recorded tax expense of $8.9 million related to the remeasurement of deferred tax assets and liabilities. The provisional remeasurement amount is anticipated to change as data becomes available allowing more accurate scheduling of certain deferred tax assets and liabilities. The Tax Reform also includes a one-time mandatory repatriation transition tax on previously untaxed accumulated and current earnings and profits (E&P) of certain of the Company’s foreign subsidiaries. To determine the amount of the transition tax, the Company must determine, in addition to other factors, the amount of post 1986 E&P of the relevant subsidiaries, as well as the amount of non-US income taxes paid on such earnings. The Company made a reasonable estimate of the transition tax and recorded a provisional transition tax obligation of $12.0 million . The Company continues to gather additional information to more precisely compute the amount of the transition tax. The SEC staff issued Staff Accounting Bulletin No. 118 (SAB 118), which provides guidance on accounting for the tax effects of the Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Reform enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Reform for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Reform is incomplete but it can determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 based on the tax laws that were in effect immediately before the enactment of the Tax Reform. While the Company can make reasonable estimates of the impact of the reduction in corporate rate and the deemed repatriation transition tax, the final impact of the Tax Reform may differ from these estimates, due to, among other things, changes in our interpretations and assumptions, additional guidance that may be issued by taxing authorities, and actions the Company may take. The Tax Reform also establishes new tax laws that will affect the fiscal year ending September 30, 2019, including, but not limited to, (1) elimination of the corporate alternative minimum tax, (2) a new provision designed to tax global intangible low-taxed income (GILTI), (3) limitations on the utilization of net operating losses generated after December 31, 2017 to 80 percent of taxable income per tax year, (4) the creation of the base erosion anti-abuse tax (BEAT), (5) a general elimination of U.S. federal income taxes on dividends from foreign subsidiaries, and (6) limitations on the deductibility of certain executive compensation. Effects of tax law changes where a reasonable estimate of the accounting effects has not yet been made include additional limitations on certain meals and entertainment expenses and the unlimited carryforward of net operating losses. The Company has also not yet determined the potential tax impact of provisions that are not yet effective, such as GILTI, BEAT, elimination of U.S. tax on dividends of future foreign earnings, and a limitation of the utilization of net operating losses generated after fiscal 2018 to 80 percent of taxable income per tax year. The Company expects to make the policy election to treat GILTI as a period expense in the fiscal year ending September 30, 2018. Current and Prior Period Tax Expense Income tax expense of $25.5 million and $2.1 million for the three months ended December 31, 2017 and 2016 , respectively, reflect estimated federal, foreign, state and local taxes. The Company recorded discrete expense of $20.9 million related to the Tax Reform. Tax expense, excluding the discrete expense related to the Tax Reform, was $4.6 million . For the three months ended December 31, 2017 and 2016 , the Company’s effective tax rate was 137% and 25% , respectively. The discrete expense of $20.9 million related to tax reform, increased the effective tax rate by 112% . The effective rate for the first quarter of 2018 was 24.5% , excluding the impacts of the Tax Reform. The Company’s effective tax rate decreased 1.2% due to excess tax benefits on share-based compensation recognized during the period related to the adoption of ASU 2016-09. See Note 1 for more information regarding the adoption of ASU 2016-09. The effective rate during the first quarter of fiscal year 2017 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 valuation allowance for deferred tax assets as of December 31, 2017 and September 30, 2017 was $4.5 million and $4.0 million , respectively. The valuation allowances as of December 31, 2017 and September 30, 2017 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, 2017, 2016, and 2015 of $(24.7) million , $(9.7) million and $16.5 million , respectively. The differences between actual levels of past taxable income (losses) and pre-tax book income (losses) are primarily attributable to temporary differences in these jurisdictions. When evaluating if U.S. federal, state, and local deferred tax assets are realizable, the Company considered deferred tax liabilities of $5.5 million that are scheduled to reverse from 2018 to 2020 and $2.3 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 5 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. The Company and its subsidiaries file income tax returns with the U.S. federal jurisdiction and various state, local and foreign jurisdictions. The Company has open tax years ranging from September 30, 2010 through September 30, 2017 with U.S. federal and state and local taxing authorities. In the U.K., the Company has open tax years ending September 30, 2016 to September 30, 2017. In Brazil, the Company has open tax years ranging from December 31, 2012 through December 31, 2017. In Argentina, the Company has open tax years ranging from September 30, 2010 to September 30, 2017. In Singapore, the Company has open tax years ranging from September 30, 2012 to September 30, 2017.

Segment Analysis (Notes)

Segment Analysis (Notes)	3 Months Ended
	Dec. 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. The foreign exchange trading business competes for this business as it does any other business. If its rates are not competitive, the securities businesses buy or sell their foreign currency through other market counterparties. On a recurring basis, the Company sweeps excess cash from certain U.S. 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 December 31, (in millions) 2017 2016 Total revenues: Commercial Hedging $ 61.5 $ 57.5 Global Payments 24.6 23.1 Securities 43.0 37.4 Physical Commodities 7,716.6 5,898.7 Clearing and Execution Services 72.2 63.6 Corporate unallocated 0.7 (5.9 ) Total $ 7,918.6 $ 6,074.4 Operating revenues (loss): Commercial Hedging $ 61.5 $ 57.5 Global Payments 24.6 23.1 Securities 43.0 37.4 Physical Commodities 10.6 9.8 Clearing and Execution Services 72.2 63.6 Corporate unallocated 0.7 (5.9 ) Total $ 212.6 $ 185.5 Net operating revenues (loss): Commercial Hedging $ 49.1 $ 45.6 Global Payments 23.0 20.6 Securities 23.5 25.1 Physical Commodities 8.4 8.1 Clearing and Execution Services 27.4 24.1 Corporate unallocated (1.1 ) (9.2 ) Total $ 130.3 $ 114.3 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 $ 36.5 $ 33.4 Global Payments 18.4 16.4 Securities 17.8 19.8 Physical Commodities 5.6 5.8 Clearing and Execution Services 20.5 18.0 Total $ 98.8 $ 93.4 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 21.1 $ 15.4 Global Payments 14.6 13.2 Securities 11.0 12.9 Physical Commodities 1.1 3.0 Clearing and Execution Services 10.5 5.7 Total $ 58.3 $ 50.2 Reconciliation of segment income to income before tax: Segment income $ 58.3 $ 50.2 Net costs not allocated to operating segments 39.7 41.8 Income before tax $ 18.6 $ 8.4 (in millions) As of December 31, 2017 As of September 30, 2017 Total assets: Commercial Hedging $ 1,533.3 $ 1,650.3 Global Payments 188.2 199.5 Securities 2,569.1 2,101.7 Physical Commodities 414.7 339.5 Clearing and Execution Services 2,005.1 1,818.9 Corporate unallocated 98.5 133.5 Total $ 6,808.9 $ 6,243.4

Basis of Presentation and Con24

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Policies)	3 Months Ended
	Dec. 31, 2017
Basis of Presentation and Consolidation [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The accompanying unaudited condensed consolidated balance sheet as of September 30, 2017 , which has been derived from audited consolidated 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 consolidated 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, 2017 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 consolidated 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, 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.
Reclassification, Policy [Policy Text Block]	Reclassifications During the quarter ended December 31, 2017, the Company separately classified non-trading technology and support costs that were previously included within ‘Other’ on the condensed consolidated income statements. Additionally, during the quarter ended December 31, 2017, the Company separately classified communications related expenses separately from trading systems and market information related costs. In performing these reclassifications, the Company has made immaterial, retrospective adjustments to conform to our current period presentation. For the three months December 31, 2016, ‘Other’ expenses included $2.9 million of expenses that are now included within ‘Non-trading technology and support’ on the condensed consolidated income statements. For the three months ended December 31, 2016, ‘Trading systems and market information’ included $1.2 million of expenses that are now included within ‘Communications’ on the condensed consolidated income statements.
New Accounting Pronouncements, Policy [Policy Text Block]	In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”), which simplifies several aspects of the accounting for share-based payment transactions. Under ASU 2016-09, excess tax benefits and tax deficiencies are recognized as income tax expense or benefit in the income statement instead of additional paid in capital. ASU 2016-09 also provides entities with the option to elect an accounting policy to estimate forfeitures of stock-based awards over the service period (current GAAP) or account for forfeitures when they occur. Under ASU 2016-09, previously unrecognized excess tax benefits should be recognized using a modified retrospective transition. In addition, amendments requiring recognition of excess tax benefits and tax deficiencies in the income statement, as well as changes in the computation of weighted-average diluted shares outstanding, should be applied prospectively. ASU 2016-09 is effective for and was adopted by the Company in the first quarter of 2018 and the impact of the adoption resulted in the following: • During the three months ended December 31, 2017, the Company recognized excess tax benefits from stock-based compensation of $0.2 million within income tax expense on the condensed consolidated income statement and within net income on the condensed consolidated cash flow statement. Prior to adoption, the tax effect of stock-based awards would have been recognized in additional paid-in-capital on the condensed consolidated balance sheets and separately stated in the financing activities in the condensed consolidated cash flow statements. The Company has elected to adopt this guidance prospectively. • The Company has elected to estimate forfeitures of stock-based awards as they occur. The Company elected to account for forfeitures as they occur using a modified retrospective transition method. The adoption of this guidance did not have a material impact on our condensed consolidated financial statements. • The excess tax benefits from the assumed proceeds available to repurchase shares were excluded in the computation of diluted earnings per share for the three months ended December 31, 2017. The Company has elected to adopt this guidance prospectively. • For the three months ended December 31, 2017, the Company has classified as a financing activity in the condensed consolidated cash flow statement $0.8 million of cash paid to taxing authorities for restricted stock shares withheld to satisfy statutory income tax withholding obligations. The retrospective application of this guidance had no impact on the condensed consolidated cash flow statement for the three months ended December 31, 2016. In July 2015, the FASB issued ASU No. 2015-11, “Simplifying the Measurement of Inventory (Topic 330).” Under ASU 2015-11, inventory that is measured using the first-in, first-out (FIFO), specific identification, or average cost methods should be measured at the lower of cost or net realizable value. This ASU does not impact inventory measurement under the last-in, first-out (LIFO) or retail inventory methods. For public companies, this ASU is effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. The amendments from this update are to be applied prospectively. The Company adopted this ASU prospectively on the effective date of October 1, 2017. The adoption of this ASU has not had a material impact on our condensed consolidated financial statements.

Earnings per Share (Policies)

Earnings per Share (Policies)	3 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share, Potentially Dilutive Securities	The Company presents basic and diluted earnings (loss) 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 (loss) 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 (loss) 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 (loss) income by the weighted-average number of common shares outstanding.

Income Taxes (Policies)

Income Taxes (Policies)	3 Months Ended
	Dec. 31, 2017
Income Taxes [Abstract]
Income Tax, Policy [Policy Text Block]	Note 15 – Income Taxes The income tax provision for interim periods is comprised of tax on ordinary income (loss) provided at the most recent estimated annual effective tax rate, adjusted for the tax effect of discrete items. Management uses an estimated annual effective tax rate based on the forecasted pretax income (loss) 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. Effects of the Tax Cuts and Jobs Act On December 22, 2017, the President of the United States signed and enacted into law H.R. 1, the Tax Cuts and Jobs Act (“the Tax Reform”). Among the significant changes to the U.S. Internal Revenue Code, the Tax Reform lowers the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. The Company will compute its income tax expense (benefit) for the September 30, 2018 tax year using a U.S. statutory tax rate of 24.5% . The 21% U.S. statutory tax rate will apply to fiscal years ending September 30, 2019 and thereafter. For the three months ended December 31, 2017, the Company recorded tax expense of $8.9 million related to the remeasurement of deferred tax assets and liabilities. The provisional remeasurement amount is anticipated to change as data becomes available allowing more accurate scheduling of certain deferred tax assets and liabilities. The Tax Reform also includes a one-time mandatory repatriation transition tax on previously untaxed accumulated and current earnings and profits (E&P) of certain of the Company’s foreign subsidiaries. To determine the amount of the transition tax, the Company must determine, in addition to other factors, the amount of post 1986 E&P of the relevant subsidiaries, as well as the amount of non-US income taxes paid on such earnings. The Company made a reasonable estimate of the transition tax and recorded a provisional transition tax obligation of $12.0 million . The Company continues to gather additional information to more precisely compute the amount of the transition tax. The SEC staff issued Staff Accounting Bulletin No. 118 (SAB 118), which provides guidance on accounting for the tax effects of the Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Reform enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Reform for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Reform is incomplete but it can determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 based on the tax laws that were in effect immediately before the enactment of the Tax Reform. While the Company can make reasonable estimates of the impact of the reduction in corporate rate and the deemed repatriation transition tax, the final impact of the Tax Reform may differ from these estimates, due to, among other things, changes in our interpretations and assumptions, additional guidance that may be issued by taxing authorities, and actions the Company may take. The Tax Reform also establishes new tax laws that will affect the fiscal year ending September 30, 2019, including, but not limited to, (1) elimination of the corporate alternative minimum tax, (2) a new provision designed to tax global intangible low-taxed income (GILTI), (3) limitations on the utilization of net operating losses generated after December 31, 2017 to 80 percent of taxable income per tax year, (4) the creation of the base erosion anti-abuse tax (BEAT), (5) a general elimination of U.S. federal income taxes on dividends from foreign subsidiaries, and (6) limitations on the deductibility of certain executive compensation. Effects of tax law changes where a reasonable estimate of the accounting effects has not yet been made include additional limitations on certain meals and entertainment expenses and the unlimited carryforward of net operating losses. The Company has also not yet determined the potential tax impact of provisions that are not yet effective, such as GILTI, BEAT, elimination of U.S. tax on dividends of future foreign earnings, and a limitation of the utilization of net operating losses generated after fiscal 2018 to 80 percent of taxable income per tax year. The Company expects to make the policy election to treat GILTI as a period expense in the fiscal year ending September 30, 2018. Current and Prior Period Tax Expense Income tax expense of $25.5 million and $2.1 million for the three months ended December 31, 2017 and 2016 , respectively, reflect estimated federal, foreign, state and local taxes. The Company recorded discrete expense of $20.9 million related to the Tax Reform. Tax expense, excluding the discrete expense related to the Tax Reform, was $4.6 million . For the three months ended December 31, 2017 and 2016 , the Company’s effective tax rate was 137% and 25% , respectively. The discrete expense of $20.9 million related to tax reform, increased the effective tax rate by 112% . The effective rate for the first quarter of 2018 was 24.5% , excluding the impacts of the Tax Reform. The Company’s effective tax rate decreased 1.2% due to excess tax benefits on share-based compensation recognized during the period related to the adoption of ASU 2016-09. See Note 1 for more information regarding the adoption of ASU 2016-09. The effective rate during the first quarter of fiscal year 2017 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 valuation allowance for deferred tax assets as of December 31, 2017 and September 30, 2017 was $4.5 million and $4.0 million , respectively. The valuation allowances as of December 31, 2017 and September 30, 2017 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, 2017, 2016, and 2015 of $(24.7) million , $(9.7) million and $16.5 million , respectively. The differences between actual levels of past taxable income (losses) and pre-tax book income (losses) are primarily attributable to temporary differences in these jurisdictions. When evaluating if U.S. federal, state, and local deferred tax assets are realizable, the Company considered deferred tax liabilities of $5.5 million that are scheduled to reverse from 2018 to 2020 and $2.3 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 5 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. The Company and its subsidiaries file income tax returns with the U.S. federal jurisdiction and various state, local and foreign jurisdictions. The Company has open tax years ranging from September 30, 2010 through September 30, 2017 with U.S. federal and state and local taxing authorities. In the U.K., the Company has open tax years ending September 30, 2016 to September 30, 2017. In Brazil, the Company has open tax years ranging from December 31, 2012 through December 31, 2017. In Argentina, the Company has open tax years ranging from September 30, 2010 to September 30, 2017. In Singapore, the Company has open tax years ranging from September 30, 2012 to September 30, 2017.

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Dec. 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 (loss) income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted earnings (loss) per share computations for the periods presented below. Three Months Ended December 31, (in millions, except share amounts) 2017 2016 Numerator: Net (loss) income $ (6.9 ) $ 6.3 Less: Allocation to participating securities — (0.1 ) Net (loss) income allocated to common stockholders $ (6.9 ) $ 6.2 Denominator: Weighted average number of: Common shares outstanding 18,419,072 18,248,244 Dilutive potential common shares outstanding: Share-based awards — 236,751 Diluted weighted-average common shares 18,419,072 18,484,995

Assets and Liabilities, at Fa28

Assets and Liabilities, at Fair Value (Tables)	3 Months Ended
	Dec. 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 December 31, 2017 by level in the fair value hierarchy. December 31, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificate of deposits $ 4.7 $ — $ — $ — $ 4.7 Commodities warehouse receipts 14.9 — — — 14.9 U.S. Treasury obligations 1.6 — — — 1.6 Securities and other assets segregated under federal and other regulations 16.5 — — — 16.5 U.S. Treasury obligations 219.1 — — — 219.1 "To be announced" (TBA) and forward settling securities — 1.7 — (0.6 ) 1.1 Foreign government obligations — 6.2 — — 6.2 Derivatives 3,068.1 188.7 — (3,429.5 ) (172.7 ) Deposits with and receivables from broker-dealers, clearing organization and counterparties 3,287.2 196.6 — (3,430.1 ) 53.7 Common and preferred stock, ADRs, and GDRs 30.5 3.4 0.1 — 34.0 Exchangeable foreign ordinary equities, ADRs, and GDRs 9.0 1.1 — — 10.1 Corporate and municipal bonds 45.1 0.6 — — 45.7 U.S. Treasury obligations 76.8 — — — 76.8 U.S. government agency obligations — 587.7 — — 587.7 Foreign government obligations — 11.3 — — 11.3 Agency mortgage-backed obligations — 1,053.4 — — 1,053.4 Asset-backed obligations — 21.6 — — 21.6 Derivatives 1.4 1,577.8 — (1,444.3 ) 134.9 Commodities leases — 178.9 — (168.5 ) 10.4 Commodities warehouse receipts 56.1 — — — 56.1 Exchange firm common stock 8.9 — — — 8.9 Mutual funds and other 5.0 — — — 5.0 Financial instruments owned 232.8 3,435.8 0.1 (1,612.8 ) 2,055.9 Physical commodities inventory, net 142.7 — — — 142.7 Total assets at fair value $ 3,683.9 $ 3,632.4 $ 0.1 $ (5,042.9 ) $ 2,273.5 Liabilities: TBA and forward settling securities — 1.7 — (0.6 ) 1.1 Derivatives 3,169.6 212.5 — (3,382.1 ) — Payable to broker-dealers, clearing organizations and counterparties 3,169.6 214.2 — (3,382.7 ) 1.1 Common and preferred stock, ADRs, and GDRs 48.6 1.2 — — 49.8 Exchangeable foreign ordinary equities, ADRs, and GDRs 10.2 — — — 10.2 Corporate and municipal bonds 0.3 — — — 0.3 U.S. Treasury obligations 404.6 — — — 404.6 U.S. government agency obligations — 35.5 — — 35.5 Agency mortgage-backed obligations — 3.9 — — 3.9 Derivatives — 1,634.6 — (1,385.3 ) 249.3 Commodities leases — 186.4 — (136.7 ) 49.7 Financial instruments sold, not yet purchased 463.7 1,861.6 — (1,522.0 ) 803.3 Total liabilities at fair value $ 3,633.3 $ 2,075.8 $ — $ (4,904.7 ) $ 804.4 (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, 2017 by level in the fair value hierarchy. September 30, 2017 (in millions) Level 1 Level 2 Level 3 Netting and Total Assets: Unrestricted cash equivalents - certificates of deposits $ 3.8 $ — $ — $ — $ 3.8 Commodities warehouse receipts 21.0 — — — 21.0 U.S. Treasury obligations 33.5 — — — 33.5 Securities and other assets segregated under federal and other regulations 54.5 — — — 54.5 U.S. Treasury obligations 244.7 — — — 244.7 "To be announced" (TBA) and forward settling securities — 8.8 — — 8.8 Foreign government obligations — 6.4 — — 6.4 Derivatives 2,608.6 289.1 — (2,952.9 ) (55.2 ) Deposits with and receivables from broker-dealers, clearing organizations, and counterparties 2,853.3 304.3 — (2,952.9 ) 204.7 Common and preferred stock, ADRs, and GDRs 31.2 3.4 0.1 — 34.7 Exchangeable foreign ordinary equities, ADRs, and GDRs 9.2 1.2 — — 10.4 Corporate and municipal bonds 28.2 0.9 — — 29.1 U.S. Treasury obligations 60.0 — — — 60.0 U.S. government agency obligations — 368.9 — — 368.9 Foreign government obligations — 10.2 — — 10.2 Agency mortgage-backed obligations — 920.9 — — 920.9 Asset-backed obligations — 47.3 — — 47.3 Derivatives 1.3 1,413.4 — (1,252.6 ) 162.1 Commodities leases — 174.1 — (138.7 ) 35.4 Commodities warehouse receipts 38.5 — — — 38.5 Exchange firm common stock 8.3 — — — 8.3 Mutual funds and other 6.0 — — — 6.0 Financial instruments owned 182.7 2,940.3 0.1 (1,391.3 ) 1,731.8 Physical commodities inventory, net 73.2 — — — 73.2 Total assets at fair value $ 3,167.5 $ 3,244.6 $ 0.1 $ (4,344.2 ) $ 2,068.0 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.0 $ — $ 1.0 TBA and forward settling securities — 4.9 — (0.1 ) 4.8 Derivatives 2,476.2 292.8 — (2,769.0 ) — Payable to broker-dealers, clearing organizations and counterparties 2,476.2 297.7 — (2,769.1 ) 4.8 Common and preferred stock, ADRs, and GDRs 33.7 0.7 — — 34.4 Exchangeable foreign ordinary equities, ADRs, and GDRs 10.3 0.2 — — 10.5 Corporate and municipal bonds 0.3 — — — 0.3 U.S. Treasury obligations 285.9 — — — 285.9 U.S. government agency obligations — 27.9 — — 27.9 Agency mortgage-backed obligations — 0.1 — — 0.1 Derivatives — 1,427.2 — (1,110.2 ) 317.0 Commodities leases — 191.1 — (149.6 ) 41.5 Financial instruments sold, not yet purchased 330.2 1,647.2 — (1,259.8 ) 717.6 Total liabilities at fair value $ 2,806.4 $ 1,944.9 $ 1.0 $ (4,028.9 ) $ 723.4 (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 December 31, 2017 and September 30, 2017 are summarized below: (in millions) December 31, 2017 September 30, 2017 Total Level 3 assets $ 0.1 $ 0.1 Level 3 assets for which the Company bears economic exposure $ 0.1 $ 0.1 Total assets $ 6,808.9 $ 6,243.4 Total assets at fair value $ 2,273.5 $ 2,068.0 Total Level 3 assets as a percentage of total assets — % — % Level 3 assets for which the Company bears economic exposure as a percentage of total assets — % — % Total Level 3 assets as a percentage of total financial assets at fair value — % — % 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 months ended December 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 December 31, 2017 . Level 3 Financial Assets and Financial Liabilities For the Three Months Ended December 31, 2017 (in millions) Balances at Realized gains Unrealized Purchases/issuances Settlements Transfers in Balances at Assets: Common stock and ADRs $ 0.1 $ — $ — $ — $ — $ — $ 0.1 $ 0.1 $ — $ — $ — $ — $ — $ 0.1 Level 3 Financial Assets and Financial Liabilities For the Three Months Ended December 31, 2016 (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 $ — $ — $ — $ — $ — $ 0.8

Financial Instruments with Of29

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	3 Months Ended
	Dec. 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 December 31, 2017 and September 30, 2017 . Assets represent net unrealized gains and liabilities represent net unrealized losses. December 31, 2017 September 30, 2017 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 2,515.9 $ 2,660.1 $ 2,094.2 $ 1,975.0 OTC commodity derivatives 1,208.9 1,270.9 1,084.0 1,110.3 Exchange-traded foreign exchange derivatives 53.0 32.3 66.0 52.0 OTC foreign exchange derivatives 533.4 530.8 618.5 609.8 Exchange-traded interest rate derivatives 203.1 234.8 228.4 203.6 OTC interest rate derivatives 24.2 24.2 — — Exchange traded equity index derivatives 297.5 263.6 221.3 245.4 TBA and forward settling securities 1.7 1.7 8.8 4.9 Gross fair value of derivative contracts 4,837.7 5,018.4 4,321.2 4,201.0 Impact of netting and collateral (4,874.4 ) (4,768.0 ) (4,205.5 ) (3,879.2 ) Total fair value included in ‘Deposits with and receivables from broker-dealers, clearing organizations, and counterparties’ $ (171.6 ) $ (46.4 ) Total fair value included in ‘Financial instruments owned, at fair value’ $ 134.9 $ 162.1 Total fair value included in ‘Payables to broker-dealers, clearing organizations and counterparties $ 1.1 $ 4.8 Fair value included in ‘Financial instruments sold, not yet purchased, at fair value’ $ 249.3 $ 317.0 (1) As of December 31, 2017 and September 30, 2017 , the Company’s derivative contract volume for open positions were approximately 6.8 million and 6.1 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 exchange-traded position. 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 institutional fixed income business. The fair value on these transactions are recorded in deposits with and receivables from 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 December 31, 2017 and September 30, 2017 , these transactions are summarized as follows: December 31, 2017 September 30, 2017 (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) $ 0.9 $ 525.4 $ — $ 51.3 Unrealized loss on TBA securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (0.1 ) $ 203.1 $ (2.9 ) $ 1,236.8 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ 0.5 $ (554.8 ) $ 5.8 $ (1,881.9 ) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts (1) $ (1.4 ) $ (1,041.7 ) $ (0.1 ) $ (404.1 ) Unrealized gain (loss) on forward settling securities purchased within receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 0.3 $ 240.2 $ (2.0 ) $ 882.9 Unrealized (loss) gain on forward settling securities sold within receivables from and payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.2 ) $ (107.6 ) $ 3.0 $ (590.2 ) (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 months ended December 31, 2017 and 2016 in accordance with the Derivatives and Hedging Topic of the ASC. The net gains set forth below are included in ‘Cost of sales of physical commodities’ and ‘Trading gains, net’ in the condensed consolidated income statements. Three Months Ended December 31, (in millions) 2017 2016 Commodities $ 7.7 $ 4.9 Foreign exchange 2.3 1.2 Interest rate 0.4 (1.0 ) TBA and forward settling securities (0.4 ) 13.4 Net gains from derivative contracts $ 10.0 $ 18.5

Physical Commodities Inventor30

Physical Commodities Inventory Physical Commodities Table (Tables)	3 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Schedule of Inventory, Current [Table Text Block]	(in millions) December 31, September 30, Physical Ag & Energy (1) $ 125.1 $ 65.1 Precious metals - held by broker-dealer subsidiary (2) 20.1 13.3 Precious metals - held by non-broker-dealer subsidiaries (3) 99.5 46.4 Physical commodities inventory $ 244.7 $ 124.8

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Dec. 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) December 31, September 30, Commercial Hedging $ 30.3 $ 30.7 Global Payments 6.3 6.3 Physical Commodities 2.4 2.4 Securities 6.9 7.7 Goodwill $ 45.9 $ 47.1

Intangible Assets - (Tables)

Intangible Assets - (Tables)	3 Months Ended
	Dec. 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 (in millions): December 31, 2017 September 30, 2017 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization: Software programs/platforms 2.7 (2.5 ) 0.2 2.7 (2.5 ) 0.2 Customer base 20.0 (8.5 ) 11.5 20.0 (7.9 ) 12.1 Total intangible assets $ 22.7 $ (11.0 ) $ 11.7 $ 22.7 $ (10.4 ) $ 12.3
Schedule of Expected Amortization Expense [Table Text Block]	Amortization expense related to intangible assets was $0.6 million and $0.7 million for the three months ended December 31, 2017 and 2016 , respectively. As of December 31, 2017 , the estimated future amortization expense was as follows: (in millions) Fiscal 2018 (remaining nine months) $ 1.6 Fiscal 2019 2.2 Fiscal 2020 2.0 Fiscal 2021 1.9 Fiscal 2022 and thereafter 4.0 $ 11.7

Credit Facilities (Tables)

Credit Facilities (Tables)	3 Months Ended
	Dec. 31, 2017
Credit Facilities [Abstract]
Schedule of Debt [Table Text Block]	The following table sets forth a listing of credit facilities, the current committed amounts as of the report date on the facilities, outstanding borrowings on the facilities, as well as indebtedness on a promissory note as of December 31, 2017 and September 30, 2017 : (in millions) Credit Facilities Amounts Outstanding Borrower Security Renewal / Expiration Date Total Commitment December 31, September 30, Committed Credit Facilities INTL FCStone Inc. Pledged shares of certain subsidiaries March 18, 2019 $ 262.0 $ 210.0 $ 150.0 INTL FCStone Financial, Inc. None April 5, 2018 75.0 36.5 — FCStone Merchants Services, LLC Certain commodities assets May 1, 2018 170.0 103.5 44.2 INTL FCStone Ltd. None November 7, 2018 25.0 — — $ 532.0 350.0 194.2 Uncommitted Credit Facilities INTL FCStone Financial, Inc. Commodities warehouse receipts and certain pledged securities n/a $ — $ 71.1 $ 34.0 INTL FCStone Ltd. Commodities warehouse receipts n/a $ — $ — $ — Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 1.8 2.0 Total indebtedness $ 422.9 $ 230.2

Commodity and Other Repurchas34

Commodity and Other Repurchase Agreements and Collateralized Transactions Schedule of Gross Collateralized Financings by Maturity (Tables)	3 Months Ended
	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Schedule of Repurchase Agreement Counterparties with Whom Repurchase Agreements Exceed 10 Percent of Stockholders' Equity [Table Text Block]	December 31, 2017 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $1,121.4 $239.0 $290.0 — $1,650.4 Securities loaned 108.8 — — — 108.8 Gross amount of secured financing $1,230.2 $239.0 $290.0 $0.0 $1,759.2 September 30, 2017 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $640.2 $432.9 $320.0 — $1,393.1 Securities loaned 111.1 — — — 111.1 Gross amount of secured financing $751.3 $432.9 $320.0 — $1,504.2

Commodity and Other Repurchas35

Commodity and Other Repurchase Agreements and Collateralized Transactions Schedule of Collateralized Financings by Collateral Type (Tables)	3 Months Ended
	Dec. 31, 2017
Financial Instruments Owned and Pledged as Collateral [Line Items]
Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block]	Securities sold under agreements to repurchase: December 31, 2017 September 30, 2017 U.S. Treasury obligations $ 3.2 $ 7.0 U.S. government agency obligations 358.2 332.6 Asset-backed obligations 75.0 36.4 Agency mortgage-backed obligations 1,214.0 1,017.1 Total securities sold under agreements to repurchase $ 1,650.4 $ 1,393.1 Securities loaned: Common stock 108.8 111.1 Total securities loaned 108.8 111.1 Gross amount of secured financing $ 1,759.2 $ 1,504.2

Capital and Other Regulatory 36

Capital and Other Regulatory Requirements (Tables)	3 Months Ended
	Dec. 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 December 31, 2017 , as follows: (in millions) As of December 31, 2017 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. SEC and Commodity Futures Trading Commission ("CFTC") United States Net capital $ 136.1 $ 74.2 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,256.9 $ 2,204.4 INTL FCStone Financial Inc. CFTC United States Secured funds $ 164.4 $ 147.8 INTL FCStone Financial Inc. SEC United States Customer reserve $ 12.0 $ — INTL FCStone Financial Inc. SEC United States PAB reserve $ 10.7 $ 10.2 INTL Custody & Clearing Soluntions Inc. SEC United States Net capital $ 1.7 $ 0.1 SA Stone Wealth Management Inc. SEC United States Net capital $ 4.2 $ 0.3 INTL FCStone Ltd (1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 191.8 $ 90.2 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 113.8 $ 113.8 INTL Netherlands BV (1) FCA United Kingdom Net capital $ 191.1 $ 90.2 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 12.6 $ 0.5 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 4.5 $ 0.2 INTL Gainvest S.A. CNV Argentina Net capital $ 3.0 $ 0.1 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.0 $ 0.9 INTL CIBSA S.A. CNV Argentina Net capital $ 1.7 $ 0.5 (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. 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 December 31, 2017 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Tables)

Other Expenses (Tables)	3 Months Ended
	Dec. 31, 2017
Other Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Other expenses for the three months ended December 31, 2017 and 2016 consisted of the following: Three Months Ended December 31, (in millions) 2017 2016 Insurance $ 0.6 $ 0.5 Advertising, meetings and conferences 0.9 0.9 Office supplies and printing 0.4 0.6 Other clearing related expenses 0.5 0.4 Other non-income taxes 1.2 1.1 Other 2.1 2.1 Total other expenses $ 5.7 $ 5.6

Accumulated Other Comprehensi38

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Dec. 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, net for the three months ended December 31, 2017 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2017 $ (21.5 ) $ (3.0 ) $ (24.5 ) Other comprehensive loss, net of tax (2.2 ) — (2.2 ) Balances as of December 31, 2017 $ (23.7 ) $ (3.0 ) $ (26.7 )

Segment Analysis (Tables)

Segment Analysis (Tables)	3 Months Ended
	Dec. 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 December 31, (in millions) 2017 2016 Total revenues: Commercial Hedging $ 61.5 $ 57.5 Global Payments 24.6 23.1 Securities 43.0 37.4 Physical Commodities 7,716.6 5,898.7 Clearing and Execution Services 72.2 63.6 Corporate unallocated 0.7 (5.9 ) Total $ 7,918.6 $ 6,074.4 Operating revenues (loss): Commercial Hedging $ 61.5 $ 57.5 Global Payments 24.6 23.1 Securities 43.0 37.4 Physical Commodities 10.6 9.8 Clearing and Execution Services 72.2 63.6 Corporate unallocated 0.7 (5.9 ) Total $ 212.6 $ 185.5 Net operating revenues (loss): Commercial Hedging $ 49.1 $ 45.6 Global Payments 23.0 20.6 Securities 23.5 25.1 Physical Commodities 8.4 8.1 Clearing and Execution Services 27.4 24.1 Corporate unallocated (1.1 ) (9.2 ) Total $ 130.3 $ 114.3 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 $ 36.5 $ 33.4 Global Payments 18.4 16.4 Securities 17.8 19.8 Physical Commodities 5.6 5.8 Clearing and Execution Services 20.5 18.0 Total $ 98.8 $ 93.4 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 21.1 $ 15.4 Global Payments 14.6 13.2 Securities 11.0 12.9 Physical Commodities 1.1 3.0 Clearing and Execution Services 10.5 5.7 Total $ 58.3 $ 50.2 Reconciliation of segment income to income before tax: Segment income $ 58.3 $ 50.2 Net costs not allocated to operating segments 39.7 41.8 Income before tax $ 18.6 $ 8.4 (in millions) As of December 31, 2017 As of September 30, 2017 Total assets: Commercial Hedging $ 1,533.3 $ 1,650.3 Global Payments 188.2 199.5 Securities 2,569.1 2,101.7 Physical Commodities 414.7 339.5 Clearing and Execution Services 2,005.1 1,818.9 Corporate unallocated 98.5 133.5 Total $ 6,808.9 $ 6,243.4

Basis of Presentation and Con40

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Details) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2017
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ 0.2
Payments Related to Tax Withholding for Share-based Compensation	$ 0.8	$ 0
Number of different types of foreign currencies			140
Number of accounts for customers company-wide			20,000
Non-Trading Technology and Support [Member]
Prior Period Reclassification Adjustment		2.9
Communications
Prior Period Reclassification Adjustment		$ 1.2

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income	$ (6.9)	$ 6.3
Less: Net income allocated to participating securities	0	(0.1)
Net income allocated to common shareholders	$ (6.9)	$ 6.2
Weighted average number of common shares outstanding	18,419,072	18,248,244
Dilutive potential common shares outstanding:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	236,751
Diluted weighted-average shares	18,419,072	18,484,995

Earnings per Share - Antiduliti

Earnings per Share - Antidulitive Securities (Details) - shares	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	489,721	914,453

Assets and Liabilities, at Fa43

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	$ 464.4	$ 518.8
Receivables from Brokers-Dealers and Clearing Organizations	2,628.2	2,625.1
Financial Instruments, Owned, at Fair Value	2,055.9	1,731.8
Physical commodities inventory	244.7	124.8
Assets, Fair Value Disclosure	2,273.5	2,068
Accounts Payable and Other Accrued Liabilities	111.5	135.6
Payables to Broker-Dealers and Clearing Organizations	(197.1)	(125.7)
Financial Instruments Sold, Not yet Purchased, at Fair Value	803.3	717.6
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	16.5	54.5
Receivables from Clearing Organizations	53.7	204.7
Financial Instruments, Owned, at Fair Value	2,055.9	1,731.8
Assets, Fair Value Disclosure	2,273.5	2,068
Financial Instruments Sold, Not yet Purchased, at Fair Value	803.3
Liabilities, Fair Value Disclosure	804.4	723.4
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	(1.1)	(4.8)
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	0
Payables to Broker-Dealers and Clearing Organizations		0
Fair Value, Measurements, Recurring [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(1.1)	(4.8)
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		1
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	142.7	73.2
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	21.6	47.3
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	587.7	368.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	35.5	27.9
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	34	34.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	49.8	34.4
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	10.1	10.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	10.2	10.5
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	45.7	29.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.3	0.3
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	76.8	60
Financial Instruments Sold, Not yet Purchased, at Fair Value	404.6	285.9
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	11.3	10.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	3.9		$ 0.1
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	1,053.4	920.9
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	134.9	162.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	249.3
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	10.4	35.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	49.7	41.5
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	56.1	38.5
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	8.9	8.3
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	5	6
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	219.1
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	6.2	6.4
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	1.1	8.8
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	(172.7)
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		244.7
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		(55.2)
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	14.9	21
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	1.6	33.5
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	4.7	3.8
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	(3,430.1)	(2,952.9)
Financial Instruments, Owned, at Fair Value	(1,612.8)	(1,391.3)
Assets, Fair Value Disclosure	(5,042.9)	(4,344.2)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(1,522)	(1,259.8)
Liabilities, Fair Value Disclosure	(4,904.7)	(4,028.9)
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	0.6	0.1
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	3,382.1	2,769
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	3,382.7	2,769.1
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
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] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | US Government Agencies 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] | 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		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
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	(1,444.3)	(1,252.6)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(1,385.3)	(1,110.2)
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	(168.5)	(138.7)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(136.7)	(149.6)
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] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	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]
Receivables from Clearing Organizations	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]
Receivables from Clearing Organizations	(0.6)
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	(3,429.5)
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]
Receivables from Clearing Organizations		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]
Receivables from Clearing Organizations		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
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		(2,952.9)
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	16.5	54.5
Receivables from Clearing Organizations	3,287.2	2,853.3
Financial Instruments, Owned, at Fair Value	232.8	182.7
Assets, Fair Value Disclosure	3,683.9	3,167.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	463.7	330.2
Liabilities, Fair Value Disclosure	3,633.3	2,806.4
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	(3,169.6)	(2,476.2)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(3,169.6)	(2,476.2)
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
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	142.7	73.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies 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] | 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	30.5	31.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	48.6	33.7
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	9	9.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	10.2	10.3
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	45.1	28.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	0.3	0.3
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]
Financial Instruments, Owned, at Fair Value	76.8	60
Financial Instruments Sold, Not yet Purchased, at Fair Value	404.6	285.9
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		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
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	1.4	1.3
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
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	56.1	38.5
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	8.9	8.3
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	5	6
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	219.1
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]
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	3,068.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		244.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		2,608.6
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	14.9	21
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	1.6	33.5
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	4.7	3.8
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	0	0
Receivables from Clearing Organizations	196.6	304.3
Financial Instruments, Owned, at Fair Value	3,435.8	2,940.3
Assets, Fair Value Disclosure	3,632.4	3,244.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	1,861.6	1,647.2
Liabilities, Fair Value Disclosure	2,075.8	1,944.9
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	(1.7)	(4.9)
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	(212.5)	(292.8)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(214.2)	(297.7)
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
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] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	21.6	47.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	587.7	368.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	35.5	27.9
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	3.4	3.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	1.2	0.7
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	1.1	1.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0.6	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	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
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	11.3	10.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	3.9		0.1
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	1,053.4	920.9
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	1,577.8	1,413.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	1,634.6	1,427.2
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	178.9	174.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	186.4	191.1
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] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
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]
Receivables from Clearing Organizations	6.2	6.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	1.7	8.8
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	188.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		289.1
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	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	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
Financial Instruments, Owned, at Fair Value	0.1	0.1
Assets, Fair Value Disclosure	0.1	0.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Liabilities, Fair Value Disclosure	0	1
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] | Payable to broker-dealers, clearing organizations and counterparties [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		1
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] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies 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] | 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	0.1	0.1
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	0
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		$ 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
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] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	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]
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
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
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
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	Dec. 31, 2017	Sep. 30, 2017
Assets and Liabilities, at Fair Value [Abstract]
Total Level 3 Assets	$ 0.1	$ 0.1
Level 3 assets for which the company bears economic exposure	0.1	0.1
Assets	6,808.9	6,243.4
Assets, Fair Value Disclosure	$ 2,273.5	$ 2,068
Total level 3 assets as a percentage of total assets	0.00%	0.00%
Level 3 assets for which the company bears economic exposure as a percertange of total assets	0.00%	0.00%
Total level 3 assets as a percentage of total financial assets at fair value	0.00%	0.00%

Assets and Liabilities, at Fa45

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

Assets and Liabilities, at Fa46

Assets and Liabilities, at Fair Value - Contingent Consideration (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Mar. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of contingent consideration for acquisitions	$ 0.1
Business Combination, Contingent Consideration, Liability	$ 1
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

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	Dec. 31, 2017	Sep. 30, 2017
Financial Instruments Sold, Not yet Purchased, at Fair Value	$ 803.3	$ 717.6
Financial instrument sold, not yet purchased [Member]
Derivative, Fair Value, Net	$ 249.3	$ 317

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	Dec. 31, 2017	Sep. 30, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4,837.7	$ 4,321.2
Derivative Liability, Fair Value, Gross Liability	5,018.4	4,201
Impact of netting and collateral	(4,874.4)	(4,205.5)
Impact of netting and collateral	(4,768)	(3,879.2)
Deposits and Receivables from Exchange Clearing Organizations [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(171.6)	(46.4)
Financial instruments owned [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	134.9	162.1
Payable to broker-dealers, clearing organizations and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	1.1	4.8
Financial instrument sold, not yet purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	249.3	317
Exchange-traded Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,515.9	2,094.2
Derivative Liability, Fair Value, Gross Liability	2,660.1	1,975
Over the Counter (OTC) Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,208.9	1,084
Derivative Liability, Fair Value, Gross Liability	1,270.9	1,110.3
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	53	66
Derivative Liability, Fair Value, Gross Liability	32.3	52
Over the Counter (OTC) Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	533.4	618.5
Derivative Liability, Fair Value, Gross Liability	530.8	609.8
Exchange-traded interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	203.1	228.4
Derivative Liability, Fair Value, Gross Liability	234.8	203.6
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	24.2	0
Derivative Liability, Fair Value, Gross Liability	24.2	0
Equity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	297.5	221.3
Derivative Liability, Fair Value, Gross Liability	263.6	245.4
TBA and forward settling securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1.7	8.8
Derivative Liability, Fair Value, Gross Liability	$ 1.7	$ 4.9

Financial Instruments with Of49

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) number in Millions	Dec. 31, 2017	Sep. 30, 2017
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative, Number of Instruments Held	6.8	6.1

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	Dec. 31, 2017	Sep. 30, 2017
Derivative Asset, Fair Value, Gross Asset	$ 4,837.7	$ 4,321.2
Derivative Liability, Fair Value, Gross Liability	5,018.4	4,201
TBA securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset	0.9	0
Derivative Liability, Notional Amount	(203.1)	(1,236.8)
Derivative Liability, Fair Value, Gross Liability	(0.1)	(2.9)
Derivative Asset, Notional Amount	525.4	51.3
TBA securities sold [Member]
Derivative Asset, Fair Value, Gross Asset	0.5	5.8
Derivative Liability, Notional Amount	(1,041.7)	(404.1)
Derivative Liability, Fair Value, Gross Liability	(1.4)	(0.1)
Derivative Asset, Notional Amount	554.8	1,881.9
Forward settling securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset	0.3	(2)
Derivative Asset, Notional Amount	240.2	882.9
Over the Counter (OTC) Commodity Contracts [Member]
Derivative Liability, Notional Amount	(107.6)	(590.2)
Derivative Liability, Fair Value, Gross Liability	$ (0.2)	$ 3

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
	Dec. 31, 2017	Dec. 31, 2016
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 7.7	$ 4.9
Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	2.3	1.2
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	0.4	(1)
TBA and forward settling securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(0.4)	13.4
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 10	$ 18.5

Receivables From Customers, N52

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Customer Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Receivables from customers and notes receivable, net [Abstract]
Allowance for Doubtful Accounts Receivable	$ 7.6
Allowance for Doubtful Accounts, Premiums and Other Receivables	$ 48.1	$ 47

Receivables From Customers, N53

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Notes Receivable (Details) $ in Millions	Sep. 30, 2016USD ($)
Receivables from customers and notes receivable, net [Abstract]
Allowance Notes Receivable	$ 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
	Dec. 31, 2017	Dec. 31, 2016
Provision for Doubtful Accounts	$ 1.1	$ 2.5
Commercial Hedging [Member]
Provision for Doubtful Accounts		$ 2.5

Physical Commodities Inventor55

Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Inventory [Line Items]
Physical Ag & Energy(1)	$ 125.1	$ 65.1
Precious metals - held by non-broker-dealer subsidiaries(3)			$ 142.7	$ 73.2
Physical commodities inventory	244.7	124.8
Physical commodities inventory - precious metals [Member]
Inventory [Line Items]
Precious metals - held by non-broker-dealer subsidiaries(3)	20.1	13.3
Finished commodities	$ 99.5	$ 46.4

Physical Commodities Inventor56

Physical Commodities Inventory - LCM Adjustments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Physical Commodities Inventory [Abstract]
Inventory Adjustments	$ 1.3	$ 0.7	$ 0.6

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Goodwill [Line Items]
Goodwill	$ 45.9	$ 47.1
Commercial Hedging [Member]
Goodwill [Line Items]
Goodwill	30.3	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	$ 6.9	$ 7.7

Goodwill Goodwill Adjustments (

Goodwill Goodwill Adjustments (Details) $ in Millions	3 Months Ended
	Dec. 31, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Translation and Purchase Accounting Adjustments	$ 1.2

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 11.7
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	(2.5)	(2.5)
Finite-Lived Intangible Assets, Net	0.2	0.2
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Customer Lists, Gross	20	20
Finite-Lived Intangible Assets, Accumulated Amortization	(8.5)	(7.9)
Finite-Lived Intangible Assets, Net	$ 11.5	$ 12.1

Intangible Assets - Indefinite-

Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Indefinite-lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 0.6	$ 0.7
Gross Finite and Indefinite-Lived Intangible Assets	22.7		$ 22.7
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	(11)		(10.4)
Intangible Assets, Net (Excluding Goodwill)	$ 11.7		$ 12.3

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Amortization of Intangible Assets	$ 0.6	$ 0.7
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2016 (remaining nine months)	1.6
Fiscal 2,017	2.2
Fiscal 2,018	2
Fiscal 2,019	1.9
Fiscal 2020 and thereafter	4
Finite-Lived Intangible Assets, Net	$ 11.7

Credit Facilities - Number of C

Credit Facilities - Number of Credit Facilities (Details) $ in Millions	3 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Repayments of Unsecured Debt	$ 0	$ 45.5
Number of credit facilities	4

Credit Facilities - Credit Faci

Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Line of Credit Facility [Line Items]
Short-term Debt	$ 350	$ 194.2
Lenders under loans	422.9	230.2
Notes Payable to Bank	1.8	2
Debt and Capital Lease Obligations	422.9	230.2
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	270
Line of Credit Facility, Maximum Borrowing Capacity	532
IFFI Uncommitted Lines of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0
Lenders under loans	71.1	34
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	262
Lenders under loans	210	150
FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75
Lenders under loans	36.5	0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	170
Lenders under loans	103.5	44.2
INTL FCStone Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	25
Lenders under loans	0	0
IFL Uncommitted Line of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0
Lenders under loans	$ 0	$ 0

Commodity and Other Repurchas64

Commodity and Other Repurchase Agreements Commodity and Other Repurchase Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	$ 819
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	472.8
Financing Receivables, net - Sales/Repurchase Agreements	1.8	$ 0.8
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	3.4
Securities Loaned, Fair Value of Collateral	101.9
Securities Sold under Agreements to Repurchase, Fair Value of Collateral			$ 3.4	$ 19.4
Trading Securities Pledged as Collateral	$ 1,687.3

Commodity and Other Repurchas65

Commodity and Other Repurchase Agreements and Collateralized Transactions Gross Financings Collateral Maturities Table (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 1,650.4	$ 1,393.1
Securities Loaned	108.8	111.1
Collateralized transactions:	1,759.2	1,504.2
Maturity Overnight and on Demand [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,121.4	640.2
Securities Loaned	108.8	111.1
Collateralized transactions:	1,230.2	751.3
Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	239	432.9
Securities Loaned	0	0
Collateralized transactions:	239	432.9
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	290	320
Securities Loaned	0	0
Collateralized transactions:	290	320
Maturity Greater than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	0	0
Securities Loaned	0	0
Collateralized transactions:	$ 0	$ 0

Commodity and Other Repurchas66

Commodity and Other Repurchase Agreements and Collateralized Transactions Gross Collateralized Financings by Collateral Type Table (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 1,650.4	$ 1,393.1
Securities Loaned	108.8	111.1
Collateralized transactions:	1,759.2	1,504.2
US Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	3.2	7
US Government Agencies Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	358.2	332.6
Asset-backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	75	36.4
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,214	1,017.1
Equity Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned	$ 108.8	$ 111.1

Commitments and Contingencies -

Commitments and Contingencies - Contigent Consideration for Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Mar. 31, 2015
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	$ 1
Change in fair value of contingent consideration for acquisitions	$ 0.1
Contingent Consideration [Member]
Business Acquisition, Contingent Consideration [Line Items]
Change in fair value of contingent consideration for acquisitions		$ 0.2

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Self Insurance (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitments and Contingencies [Abstract]
Self Insurance Reserve	$ 0.7

Capital and Other Regulatory 69

Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) $ in Millions	Dec. 31, 2017USD ($)
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 136.1
Required Net Capital under Commodity Exchange Act	74.2
Cash and Securities Segregated under Commodity Exchange Act Regulation	2,256.9
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	2,204.4
Secured Funds	164.4
Secured Funds Required Under Commodity Exchange Act	147.8
Sterne Agee Clearing, Inc. [Member]
Net Capital under Commodity Exchange Act Computation	1.7
Required Net Capital under Commodity Exchange Act	0.1
Sterne Agee, and Leach, Inc [Member]
Net Capital under Commodity Exchange Act Computation	4.2
Required Net Capital under Commodity Exchange Act	0.3
INTL FCStone Ltd [Member]
Net Capital under Commodity Exchange Act Computation	191.8
Required Net Capital under Commodity Exchange Act	90.2
Cash and Securities Segregated under Commodity Exchange Act Regulation	113.8
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	113.8
INTL Netherlands BV [Member]
Net Capital under Commodity Exchange Act Computation	191.1
Required Net Capital under Commodity Exchange Act	90.2
INTL FCStone DTVM Ltda [Member]
Net Capital	12.6
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	3
Required Net Capital under Commodity Exchange Act	0.1
Net Capital	4.5
Capital Required for Capital Adequacy	0.2
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	5
Required Net Capital under Commodity Exchange Act	0.9
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	1.7
Required Net Capital under Commodity Exchange Act	$ 0.5

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Other Expenses [Abstract]
General Insurance Expense	$ 0.6	$ 0.5
Advertising Expense	0.9	0.9
Supplies and Postage Expense	0.4	0.6
Clearance Fees	0.5	0.4
Taxes, Miscellaneous	1.2	1.1
Other Expenses	$ 2.1	$ 2.1

Accumulated Other Comprehensi71

Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (26.7)		$ (24.5)
Other comprehensive loss	(2.2)	$ (0.9)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(23.7)		(21.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2.2)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(3)		(3)
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	(26.7)		$ (24.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2.2)
Other comprehensive loss	$ (2.2)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	24.50%
Deferred Tax Assets, Valuation Allowance	$ 4.5		$ 4	$ 3.6
Income (Loss) from Continuing Operations before Income Taxes, Domestic			$ (24.7)	$ (9.7)	$ 16.5
Deferred Tax Liabilities, Net	5.5
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	2.3
Income Tax Expense (Benefit)	$ 25.5	$ 2.1
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	137.00%	25.00%
Deferred Income Tax Expense (Benefit)	$ 8.9
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 12

Segment Analysis (Details)

Segment Analysis (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 7,918.6	$ 6,074.4
Operating revenues	212.6	185.5
Net operating revenues	130.3	114.3
Net Segment Contribution	98.8	93.4
Segment Income	58.3	50.2
Costs not allocated to operating segments	39.7	41.8
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	18.6	8.4
Assets	6,808.9		$ 6,243.4
Commercial Hedging [Member]
Segment Reporting Information [Line Items]
Revenues	61.5	57.5
Operating revenues	61.5	57.5
Net operating revenues	49.1	45.6
Net Segment Contribution	36.5	33.4
Segment Income	21.1	15.4
Assets	1,533.3		1,650.3
Global Payments [Member]
Segment Reporting Information [Line Items]
Revenues	24.6	23.1
Operating revenues	24.6	23.1
Net operating revenues	23	20.6
Net Segment Contribution	18.4	16.4
Segment Income	14.6	13.2
Assets	188.2		199.5
Securities Segment [Member]
Segment Reporting Information [Line Items]
Revenues	43	37.4
Operating revenues	43	37.4
Net operating revenues	23.5	25.1
Net Segment Contribution	17.8	19.8
Segment Income	11	12.9
Assets	2,569.1		2,101.7
Physical Commodities [Member]
Segment Reporting Information [Line Items]
Revenues	7,716.6	5,898.7
Operating revenues	10.6	9.8
Net operating revenues	8.4	8.1
Net Segment Contribution	5.6	5.8
Segment Income	1.1	3
Assets	414.7		339.5
Clearing and Execution Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	72.2	63.6
Operating revenues	72.2	63.6
Net operating revenues	27.4	24.1
Net Segment Contribution	20.5	18
Segment Income	10.5	5.7
Assets	2,005.1		1,818.9
Corporate [Member]
Segment Reporting Information [Line Items]
Revenues	0.7	(5.9)
Operating revenues	0.7	(5.9)
Net operating revenues	(1.1)	$ (9.2)
Assets	$ 98.5		$ 133.5