StoneX (SNEX) 10-K 12 Dec 19 2019 FY Annual report Financial data

DEI Document

DEI Document - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Dec. 09, 2019	Mar. 31, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	INTL FCSTONE INC.
Entity Central Index Key	0000913760
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,110,585
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Public Float			$ 453.7

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
ASSETS
Cash and cash equivalents	$ 471.3	$ 342.3
Cash, securities and other assets segregated under federal and other regulations (including $306.0 and $643.3 at fair value at September 30, 2019 and September 30, 2018, respectively)	1,049.9	1,408.7
Securities purchased under agreements to resell	1,424.5	870.8
Securities Borrowed	1,423.2	225.5
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net (including $626.9 and $517.4 at fair value at September 30, 2019 and September 30, 2018, respectively)	2,540.5	2,234.5
Receivables from clients, net	422.3	288
Notes receivable, net	2.9	3.8
Income taxes receivable	5.2	0.3
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $478.8 and $123.0 at September 30, 2019 and September 30, 2018, respectively)	2,175.2	2,054.8
Physical commodities inventory, net (including $151.9 and $156.9 at fair value at September 30, 2019 and September 30, 2018, respectively	229.3	222.5
Deferred income taxes, net	18	19.8
Property and equipment, net	43.9	42.4
Goodwill and intangible assets, net	67.9	59.8
Other assets	62	51.5
Total assets	9,936.1	7,824.7
Liabilities:
Accounts payable and other accrued liabilities (including $1.8 and $0 at fair value at September 30, 2019 and September 30, 2018)	157.5	145.4
Payable to:
Clients	3,589.5	3,639.6
Broker-dealers, clearing organizations and counterparties (including $5.6 and $0.0 at fair value at September 30, 2019 and September 30, 2018, respectively)	266.2	89.5
Lenders under loans	202.3	355.2
Senior secured term loan, net	167.6	0
Income taxes payable	10.4	8.6
Securities sold under agreements to repurchase	2,773.7	1,936.7
Securities Loaned	1,459.9	277.9
Financial instruments sold, not yet purchased, at fair value	714.8	866.5
Total liabilities	9,341.9	7,319.4
Commitments and contingencies (Note 12)
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; 21,297,317 issued and 19,075,360 outstanding at September 30, 2019 and 21,030,497 issued and 18,908,540 outstanding at September 30, 2018	0.2	0.2
Common stock in treasury, at cost - 2,221,957 shares at September 30, 2019 and 2,121,957 shares at September 30, 2018	(50.1)	(46.3)
Additional paid-in capital	276.8	267.5
Retained earnings	402.1	317
Accumulated other comprehensive loss, net	(34.8)	(33.1)
Total stockholders' equity	594.2	505.3
Total liabilities and stockholders' equity	$ 9,936.1	$ 7,824.7

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
ASSETS
Securities and other assets segregated, fair value	$ 306	$ 643.3
Deposits and receivables from bds and counterparties at fair value	626.9	517.4
Physical commodities inventory at fair value	156.9	156.9
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	478.8	123
Accounts pay and other accrued - fair value	1.8	0
Payables to b/ds and counterparties at fair value	$ 5.6	$ 0
Preferred stock - par value		$ 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	21,297,317	21,030,497
Common stock - outstanding	19,075,360	18,908,540
Treasury stock - shares	2,221,957	2,121,957

Consolidated Income Statements

Consolidated Income Statements	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares
Revenues:
Sales of physical commodities	$ 31,830,300,000	$ 26,682,400,000	$ 28,673,300,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,451,300,000	2,287,600,000	2,659,800,000
Principal gains, net	415,800,000	354,100,000	297,000,000
Commission and clearing fees	372,400,000	391,800,000	318,600,000
Consulting, management, and account fees	79,600,000	71,100,000	65,000,000
Interest income	198,900,000	123,300,000	69,700,000
Total revenues	32,897,000,000	27,622,700,000	29,423,600,000
Cost of sales of physical commodities	31,790,900,000	26,646,900,000	28,639,600,000
Operating revenues	1,106,100,000	975,800,000	784,000,000
Transaction-based clearing expenses	183,500,000	179,700,000	136,300,000
Introducing broker commissions	114,700,000	133,800,000	113,000,000
Interest expense	154,700,000	80,700,000	42,100,000
Net operating revenues	653,200,000	581,600,000	492,600,000
Compensation and other expenses:
Compensation and benefits	393,100,000	337,700,000	295,700,000
Trade systems and market information	38,800,000	34,700,000	34,400,000
Occupancy and equipment rental	19,400,000	16,500,000	15,200,000
Professional fees	21,000,000	18,100,000	15,200,000
Travel and business development	16,200,000	13,800,000	13,300,000
Non-trading technology and support	20,100,000	13,900,000	11,600,000
Depreciation and amortization	14,000,000	11,600,000	9,800,000
Communications	6,600,000	5,400,000	5,000,000
Bad debts	2,500,000	3,100,000	4,300,000
(Recovery) bad debt on physical coal	(12,400,000)	1,000,000	47,000,000
Other	28,400,000	26,300,000	25,900,000
Total compensation and other expenses	547,700,000	482,100,000	477,400,000
Other gains	5,500,000	2,000,000	0
Income from operations, before tax	111,000,000	101,500,000	15,200,000
Income tax expense	25,900,000	46,000,000	8,800,000
Net Income	$ 85,100,000	$ 55,500,000	$ 6,400,000
Earnings per share:
Basic | $ / shares	$ 4.46	$ 2.93	$ 0.32
Diluted | $ / shares	$ 4.39	$ 2.87	$ 0.31
Weighted-average number of common shares outstanding:
Basic | shares	18,738,905	18,549,011	18,395,987
Diluted | shares	19,014,395	18,934,830	18,687,354

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 85.1	$ 55.5	$ 6.4
Other comprehensive income (loss), net of tax [Abstract]
Foreign currency translation adjustment	(0.8)	(9)	(1.4)
Pension liabilities adjustment	(0.8)	0.3	1.2
Reclassification of adjustment for losses (gains) included in net income:
Periodic pension costs (included in compensation and benefits)	0.1	0.1	0.4
Foreign currency gains realized upon dissolution of subsidiaries (included in principal gains, net)	(0.2)	0	0
Income tax expense from reclassification adjustments (included in income tax expense)	0	0	(0.1)
Reclassification adjustment for losses (gains) included in net income	(0.1)	0.1	0.3
Other comprehensive income (loss)	(1.7)	(8.6)	0.1
Comprehensive income	$ 83.4	$ 46.9	$ 6.5

Consolidated Cash Flows Stateme

Consolidated Cash Flows Statements - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 85,100,000	$ 55,500,000	$ 6,400,000
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Recovery) bad debt on physical coal	(2,400,000)	1,000,000	47,000,000
Depreciation and amortization	14,000,000	11,600,000	9,800,000
Provision for bad debts	2,500,000	3,100,000	4,300,000
Deferred income taxes	3,700,000	22,300,000	(9,800,000)
Amortization and extinguishment of debt issuance costs	1,500,000	1,000,000	1,900,000
Actuarial gain on pension and postretirement benefits	(300,000)	(300,000)	(300,000)
Amortization of share-based compensation expense	8,100,000	6,600,000	6,300,000
Gain on sale of property and equipment	0	0	(300,000)
Gain on acquisition	(5,500,000)	0	0
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	337,200,000	(626,700,000)	570,800,000
Change in securities purchased under agreements to resell	(553,700,000)	(464,900,000)	203,000,000
Securities borrowed	(1,197,700,000)	(138,800,000)	(79,700,000)
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	(241,700,000)	(292,900,000)	186,300,000
Receivable from customers, net	(134,300,000)	(24,300,000)	(116,400,000)
Notes receivable, net	900,000	6,800,000	8,300,000
Income taxes receivable	(4,200,000)	(1,300,000)	500,000
Financial instruments owned, at fair value	(113,300,000)	(308,700,000)	(125,600,000)
Physical commodities inventory	3,000,000	(98,700,000)	(1,700,000)
Other assets	(8,300,000)	(3,300,000)	(16,000,000)
Accounts payable and other accrued liabilities	6,700,000	18,600,000	(19,600,000)
Payable to clients	(46,800,000)	520,000,000	290,900,000
Payable to broker-dealers, clearing organizations and counterparties	176,400,000	(27,800,000)	(124,100,000)
Income taxes payable	1,800,000	3,200,000	200,000
Securities sold under agreements to repurchase	837,000,000	543,700,000	226,000,000
Securities loaned	1,182,000,000	166,800,000	93,600,000
Financial instruments sold, not yet purchased, at fair value	(156,100,000)	153,900,000	(124,400,000)
Net cash provided by (used in) provided by operating activities	195,600,000	(473,600,000)	1,037,400,000
Cash flows from investing activities:
Cash paid for acquisitions, net	(28,900,000)	(3,700,000)	(6,000,000)
Purchase of exchange memberships and common stock	0	0	(200,000)
Sale of exchange memberships and common stock	0	800,000	0
Purchase of property and equipment	(11,900,000)	(12,500,000)	(16,100,000)
Net cash used in investing activities	(40,800,000)	(15,400,000)	(22,300,000)
Cash flows from financing activities:
Net change in lenders under loans with maturities 90 days or less	(162,600,000)	125,800,000	48,200,000
Proceeds from lenders under loans with maturities greater than 90 days	357,200,000	0	0
Repayments of lenders under loans with maturities greater than 90 days	(346,700,000)	0	0
Proceeds from issuance of senior secured term loan	175,000,000	0	0
Repayments of senior secured term loan	(6,600,000)	0	0
Repayment of senior notes	0	0	(45,500,000)
Payments of notes payable	(800,000)	(800,000)	(800,000)
Deferred payments on acquisitions	0	(5,500,000)	0
Share repurchase	(3,800,000)	0	0
Debt issuance costs	(3,300,000)	(400,000)	(300,000)
Exercise of stock options	1,200,000	2,600,000	3,400,000
Withholding taxes on stock option exercises	0	(800,000)	0
Income tax benefit on stock options and awards	0	0	700,000
Net cash provided by financing activities	9,600,000	120,900,000	5,700,000
Effect of exchange rates on cash, segregated cash, cash equivalents, and segregated cash equivalents	(700,000)	(4,100,000)	1,400,000
Net increase (decrease) in cash, segregated cash, cash equivalents, and segregated cash equivalents	163,700,000	(372,200,000)	1,022,200,000
Cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period	2,287,600,000	2,659,800,000	1,637,600,000
Cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period	2,451,300,000	2,287,600,000	2,659,800,000
Supplemental disclosure of cash flow information:
Cash paid for interest	153,200,000	78,900,000	38,000,000
Income taxes paid, net of cash refunds	24,600,000	22,200,000	17,100,000
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	10,800,000	3,900,000	0
Additional consideration payable related to acquisitions	1,800,000	0	(200,000)
Acquisition of business:
Assets acquired	47,100,000	1,700,000	0
Liabilities acquired	(8,900,000)	(1,900,000)	0
Total net assets acquired	38,200,000	(200,000)	0
Escrow releases and deposits related to acquisitions	$ (4,200,000)	$ 0	$ (5,000,000)

Consolidated Statements of Shar

Consolidated Statements of Shareholders’ Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances at beginning of period at Sep. 30, 2016	$ 433.8	$ 0.2	$ (46.3)	$ 249.4	$ 255.1	$ (24.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6.4				6.4
Other comprehensive income (loss)	0.1					0.1
Excercise of stock options	3.3			3.3
Share-based compensation	6.3			6.3
Balances at end 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	55.5				55.5
Other comprehensive income (loss)	(8.6)					(8.6)
Excercise of stock options	1.9			1.9
Share-based compensation	6.6			6.6
Balances at end of period at Sep. 30, 2018	505.3	0.2	(46.3)	267.5	317	(33.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85.1				85.1
Other comprehensive income (loss)	(1.7)					(1.7)
Excercise of stock options	1.2			1.2
Share-based compensation	8.1			8.1
Repurchase of stock	(3.8)		3.8
Balances at end of period at Sep. 30, 2019	$ 594.2	$ 0.2	$ (50.1)	$ 276.8	$ 402.1	$ (34.8)

Description of Business and Sig

Description of Business and Significant Accounting Policies (Notes)	12 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Business Description and Accounting Policies [Text Block]	INTL FCStone Inc., a Delaware corporation, and its consolidated subsidiaries (collectively “INTL” or “the Company”), is a diversified global brokerage and financial services firm providing execution, risk management and advisory services, market intelligence and clearing services with significant asset class coverage and significant market coverage globally. The Company helps its clients to access market liquidity, maximize profits and manage risk. The Company’s revenues are derived primarily from financial products and advisory services intended to fulfill its clients’ commercial needs and provide bottom-line benefits to their businesses. The Company’s services include comprehensive risk management advisory services for commercial clients; clearing and execution of debt and equity securities, listed futures and options on futures contracts on all major securities and commodity exchanges; structured over-the-counter (“OTC”) products in a wide range of commodities; physical trading and hedging of precious and base 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 commercial and institutional clients and over 80,000 retail clients located in more than 130 countries, including commercial entities, asset managers, regional, national and introducing broker-dealers, insurance companies, brokers, institutional investors and professional traders, commercial and investment banks and government and non-governmental organizations (“NGOs”). Basis of Presentation The accompanying 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. Unless otherwise stated herein, all references to fiscal 2019 , fiscal 2018 , and fiscal 2017 refer to the Company’s fiscal years ended September 30. In the 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 consolidated income statements is calculated by deducting physical commodities cost of sales from total revenues. The subtotal ‘net operating revenues’ in the 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 clients 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. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments, revenue recognition, the provision for probable losses from bad debts, valuation of inventories, and incomes taxes and contingencies. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. The Company reviews all significant estimates affecting the financial statements on a recurring basis and records the effect of any necessary adjustments prior to their issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. Internal Subsidiaries Consolidation Effective July 1, 2017, the Company merged its wholly-owned regulated United States (“U.S.”) subsidiary, Sterne Agee & Leach, Inc., into the wholly-owned regulated U.S. subsidiary, INTL FCStone Financial Inc. (“INTL FCStone Financial”). As such, the assets, liabilities and equity of Sterne Agee & Leach, Inc. were transferred into INTL FCStone Financial. As discussed further in Note 20 , on January 14, 2019 the Company acquired 100% of the U.S.-based broker-dealer GMP Securities LLC (“GMP”). Subsequent to the acquisition date, the legal name of GMP was changed to INTL FCStone Credit Trading LLC (“IFT”). Effective May 1, 2019, the Company merged IFT into INTL FCStone Financial. As such, the assets, liabilities and equity of IFT were transferred into INTL FCStone Financial. Reclassifications During the year ended September 30, 2018, the Company separately classified non-trading technology and support costs that were previously included within ‘Other’ on the consolidated income statements. Additionally, during the year ended September 30, 2018, the Company separately classified communications related expenses from trading systems and market information related costs. In performing these reclassifications, the Company has made immaterial, retrospective adjustments to conform to the current presentation. For the year ended September 30, 2017, ‘Other’ expenses included $11.6 million of expenses that are now included within ‘Non-trading technology and support’ on the consolidated income statement. For the year ended September 30, 2017, ‘Trading systems and market information’ included $5.0 million of expenses that are now included within ‘Communications’ on the consolidated income statement. During the year ended September 30, 2019 , the Company reclassified certain brokerage related revenues for which the Company earns commissions on trading activity in the capacity of an agent. In performing this reclassification, the Company has made a retrospective adjustment to the consolidated income statements for the years ended September 30, 2018 and 2017. For the years ended September 30, 2018 and 2017, brokerage related revenues of $35.0 million and $35.2 million , respectively, were reclassified from ‘principal gains, net’ to ‘commissions and clearing fees’. Additionally, the Company has changed the name of the line item ‘trading gains, net’ to ‘principal gains, net’ on the consolidated income statements in order to reflect the fact that these revenue streams are earned from trading financial instruments in the capacity of a principal and in order to properly segregate revenues earned from contracts with clients in connection with the adoption of the new revenue standard as discussed below. Foreign Currency Translation The Company’s consolidated financial statements are reported in U.S. dollars. The Company’s foreign subsidiaries maintain their records either in U.S. dollars or in certain instances the currency of the country in which they operate. The method of translating local currency financial information into U.S. dollars depends on whether the economy in which the foreign subsidiary operates has been designated as highly inflationary or not. Economies with a three-year cumulative inflation rate of more than 100% are considered highly inflationary. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expense are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in earnings. Foreign subsidiaries that operate in highly inflationary countries use the U.S. dollar as their functional currency. Local currency monetary assets and liabilities are remeasured into U.S. dollars using rates of exchange as of each balance sheet date, with remeasurement adjustments and other transaction gains and losses recognized in earnings. Nonmonetary assets and liabilities do not fluctuate with changes in the local currency exchange rates to the dollar as the translated amounts for nonmonetary assets and liabilities at the end of the accounting period in which the economy becomes highly inflationary becomes the accounting basis for those assets and liabilities in the period of change and subsequent periods. Revenues and expenses are translated at rates of exchange in effect during the year. The Company operates asset management and debt trading businesses in Argentina through various wholly-owned subsidiaries. Operating revenues from the Argentinean subsidiaries represented approximately 2% of the consolidated operating revenues for the year ended September 30, 2019. The operating environment in Argentina continues to present business challenges, including ongoing devaluation of the Argentine peso and significant inflation. For the year ended September 30, 2018, the Argentine peso declined approximately 139% (from 17.3 to 41.3 pesos to the U.S. dollar). Based upon inflationary data published by the International Practices Task Force of the Center for Audit Quality, the economy of Argentina became highly inflationary during the three months ended June 30, 2018. Beginning July 1, 2018, the Company designated Argentina’s economy as highly inflationary for accounting purposes. As a result, the Company has accounted for the Argentinean entities using the U.S. dollar as their functional currency beginning in the quarter ending September 30, 2018. Argentine peso-denominated monetary assets and liabilities are remeasured at each balance sheet date to the currency exchange rate then in effect, with currency remeasurement gains and loses recognized in earnings. The translated balances for nonmonetary assets and liabilities as of June 30, 2018, became the accounting basis for those assets in the period of change and subsequent periods. As a result of Argentina’s highly inflationary status, the Company recorded translation losses through earnings of $3.9 million and $3.4 million for the years ended September 30, 2019 and 2018, respectively. At September 30, 2019 and 2018, the Company had net monetary assets denominated in Argentine pesos of $5.5 million and $11.6 million , respectively, including cash and cash equivalents of $0.1 million and $1.4 million , respectively. At September 30, 2019 and 2018, the Company had net nonmonetary assets denominated in Argentine pesos of $1.0 million . Cash and Cash Equivalents The Company considers cash held at banks and all highly liquid investments not held for trading purposes, with original or acquired maturities of 90 days or less, including certificates of deposit and money market mutual funds, to be cash and cash equivalents. Cash and cash equivalents consist of cash, foreign currency, certificates of deposit, and money market mutual funds not deposited with or pledged to clearing organizations, broker-dealers, clearing organizations or counterparties, or segregated under federal or other regulations. Certificates of deposit are stated at cost plus accrued interest, which approximates fair value, and may be withdrawn at any time at the discretion of the Company without penalty. Money market mutual funds are stated at their net asset value. Cash, Securities and Other Assets Segregated under Federal and other Regulations Pursuant to requirements of the Commodity Exchange Act and Commission Regulation 30.7 of the U.S. Commodity Futures Trading Commission (“CFTC”) in the U.S. and similarly in the United Kingdom (“U.K.”), pursuant to the Markets in Financial Instruments Implementing Directive 2006/73/EC underpinning the Client Asset (“CASS”) rules in the Financial Services Authority (“FSA”) handbook, funds deposited by clients relating to futures and options on futures contracts in regulated commodities must be carried in separate accounts which are designated as segregated client accounts. Additionally, in accordance with Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), the Company maintains separate accounts for the exclusive benefit of securities clients and proprietary accounts of broker dealers (“PABs”). Rule 15c3-3 requires the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. The deposits in segregated client accounts and SRBAs are not commingled with the funds of the Company. Under the FSA’s rules, certain categories of clients may choose to opt-out of segregation. As of September 30, 2019 and 2018 , cash, securities, and other assets segregated under federal and other regulations consisted of cash held at banks of approximately $743.9 million and $765.4 million , respectively, U.S. Treasury obligations of approximately $299.8 million and $600.4 million , respectively, and commodities warehouse receipts of approximately $6.2 million and $42.9 million , respectively (see fair value measurements discussion in Note 4 ). Collateralized Transactions The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed transactions, and securities loaned transactions primarily to fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, or meet counterparty needs under matched-booked trading strategies. These transactions are accounted for as collateralized financing transactions and are recorded at their contractual amounts plus accrued interest. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to collateralize such agreements and transactions in accordance with contractual arrangements. The Company monitors the fair value of the collateral on a daily basis and the Company may require counterparties, or may be required by counterparties, to deposit additional collateral or return collateral pledged. Interest income and interest expense are recognized over the life of the arrangements and are recorded in the statement of income as interest income or interest expense, as applicable. The carrying amount of these transactions approximate fair value due to their short-term nature and the level of collateralization. These transactions are reported gross, except when a right of offset exists and the other criteria for netting under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 210-20, Balance Sheet - Offsetting are met. Deposits with and Receivables from Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties As required by the regulations of the CFTC and the aforementioned FSA handbook, client funds received to margin, guarantee, and/or secure commodity futures and futures on options transactions are segregated and accounted for separately from the general assets of the Company. Deposits with broker-dealers, clearing organizations, and counterparties pertain primarily to deposits made to satisfy margin requirements on client and proprietary open futures and options on futures positions and to satisfy the requirements set by clearing exchanges for clearing membership. The Company also pledges margin deposits with various counterparties for over-the-counter (“OTC”) derivative contracts, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. The Company also deposits cash margin with various securities clearing organizations as an ongoing condition of the securities clearing relationships, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties are reported gross, except where a right of offset exists. As of September 30, 2019 and 2018 , the Company had cash and cash equivalents on deposit with or pledged to broker-dealers, clearing organizations, and counterparties of approximately $1.6 billion and $1.5 billion , respectively. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes guaranty deposits with clearing exchanges. The guaranty deposits are held by the clearing exchanges for use in potential default situations by one or more members of the clearing exchanges. The guaranty deposits may be applied to the Company’s obligations to the clearing exchange, or to the clearing exchange’s obligations to unrelated parties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include securities pledged to clearing exchanges. These securities are either pledged to the Company by its clients or represent investments of client funds. It is the Company’s practice to include client-owned securities on its consolidated balance sheets, as the rights to those securities have been transferred to the Company under the terms of the futures trading agreements. Securities pledged primarily include U.S. Treasury obligations, foreign government obligations, and certain exchange-traded funds (“ETFs”). Securities that are not client-owned, and represent an investment of client funds, are adjusted to fair value with associated changes in unrealized gains or losses recorded in ‘interest income’ in the consolidated income statements. For client-owned securities, the change in fair value is offset against the payable to clients with no impact recognized in the consolidated income statements. The fair value of these securities included within deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $603.8 million and $785.8 million as of September 30, 2019 and 2018 , respectively. Management has considered guidance required by ASC 860, Transfers and Servicing as it relates to securities pledged by clients to margin their futures and options on futures trading accounts. Based on a review of the agreements with the client, management believes the transferor surrenders control over those assets because: (a) the transferred assets have been isolated from the transferor—put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (b) each transferee has the right to pledge or exchange the assets (or beneficial interests) it received, and no condition both constrains the transferee (or holder) from taking advantage of its right to pledge or exchange and provides more than a trivial benefit to the transferor and (c) the transferor does not maintain effective control over the transferred assets through either (1) an agreement that both entitles and obligates the transferor to repurchase or redeem them before their maturity or (2) the ability to unilaterally cause the holder to return specific assets, other than through a cleanup call. Under this guidance, the Company reflects the client collateral assets and corresponding liabilities in the Company’s consolidated balance sheets as of September 30, 2019 and 2018 . Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes amounts due from clearing exchanges for unrealized gains and losses associated with clients’ options on futures contracts. See discussion in the Financial Instruments section below for additional information on the Company’s accounting policies for derivative contracts. For client-owned derivative contracts, the fair value is offset against the payable to clients with no impact recognized on the consolidated income statements. The Company maintains client omnibus and proprietary accounts with other clearing organizations, and the equity balances in those accounts along with any margin cash or securities deposited with the clearing organizations are included in deposits with and receivables from broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include amounts due from or due to clearing exchanges for daily variation settlements on open futures and options on futures positions. The variation settlements due from or due to clearing exchanges are paid in cash on the following business day. Variation settlements equal the daily settlement of futures contracts and premiums on options on futures contracts. Receivables from broker-dealers and counterparties also include amounts receivable for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payables to broker-dealers and counterparties primarily include amounts payable for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivables from broker-dealers, clearing organizations and counterparties, and payables to broker-dealers, clearing organizations and counterparties also include amounts related to the value of registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. Receivable from and Payable to Clients Receivable from clients, net of the allowance for doubtful accounts, include the total of net deficits in individual exchange-traded futures and OTC derivative trading accounts carried by the Company. Client deficits arise from realized and unrealized trading losses on client futures, options on futures, swaps and forwards and amounts due on cash and margin transactions. Client deficit accounts are reported gross of client accounts that contain net credit or positive balances, except where a right of offset exists. Net deficits in individual futures exchange-traded and OTC derivative trading accounts include both secured and unsecured deficit balances due from clients as of the balance sheet date. Secured deficit amounts are backed by U.S. Treasury obligations and commodity warehouse receipts. These U.S Treasury obligations and commodity warehouse receipts are not netted against the secured deficit amounts, as the conditions for right of setoff have not been met. Receivable from clients, net also includes the net amounts receivable from securities clients in connection with the settlement of regular-way cash securities, margin loans to clients, and client cash debits. It is the Company’s policy to report margin loans and payables that arise due to positive cash flows in the same client’s accounts on a net basis when the conditions for netting as specified in U.S. GAAP are met. Clients’ securities transactions cleared by the Company are recorded on a settlement date basis. Securities cleared by the Company and pledged to the Company as a condition of the custodial clearing arrangements are owned by the clients, including those that collateralize margin or other similar transactions, and are not reflected on the consolidated balance sheets as the Company does not have title to, or beneficial interests, in those assets. In the event of uncompleted transactions on settlement date, the Company records corresponding receivables and payables, respectively. The carrying value of the receivables and payables approximates fair value due to their short-term nature. Receivables from clients, net also include amounts receivable from non-broker-dealer clients for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payable to clients represent the total of client accounts with credit or positive balances. Client accounts are used primarily in connection with exchange-traded and OTC commodity, foreign exchange, precious metals, and securities transactions and include gains and losses on open trades as well as securities and cash margin deposits made as required by the Company, the exchange-clearing organizations or other clearing organizations. Client accounts with credit or positive balances are reported gross of client deficit accounts, except where a right of offset exists. Payables to broker-dealers and counterparties also includes amounts payable to non-broker-dealer clients for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivable from and payables to clients also include amounts related to the value of non-registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. The future collectability of receivables from clients can be impacted by the Company’s collection efforts, the financial stability of its clients, and the general economic climate in which it operates. The Company evaluates accounts that it believes may become uncollectible on a specific identification basis, through reviewing daily margin deficit reports, the historical daily aging of the receivables, and by monitoring the financial strength of its clients. The Company may unilaterally close client trading positions in certain circumstances. In addition, to evaluate client margining and collateral requirements, client positions are stress tested regularly and monitored for excessive concentration levels relative to the overall market size. Furthermore, in certain instances, the Company is indemnified, and able to charge back, introducing broker-dealers for bad debts incurred by their clients. The Company generally charges off an outstanding receivable balance when all economic means of recovery have been exhausted. That determination considers information such as the occurrence of significant changes in the client’s financial position such that the client can no longer pay the obligation, or that the proceeds from collateral will not be sufficient to pay the balance. Notes Receivable Accrual of commodity financing income on any note is discontinued when, in the opinion of management, there is reasonable doubt as to the timely collectability of interest or principal. Nonaccrual notes are returned to an accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely payment of principal and interest. The Company records a charge against earnings for notes receivable losses when management believes that the collection of outstanding principal is not probable. Physical Commodities Inventory Inventories of certain agricultural commodities are carried at net realizable value, which approximates fair value less disposal costs. The agricultural commodities inventories have reliable, readily determinable and realizable market prices, have relatively predictable and insignificant costs of disposal and are available for immediate delivery. Changes in the fair values of these agricultural commodities inventories are included as a component of ‘cost of sales of physical commodities’ in the consolidated income statements. Inventories of energy related products are valued at the lower of cost or net realizable value. Inventories of precious metals held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value, using the weighted-average price and first-in first-out costing method. Precious metals inventory held by INTL FCStone Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ in the consolidated income statements. Property and Equipment Property and equipment is stated at cost, net of accumulated depreciation and amortization and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the estimated useful life of the improvement or the term of the lease, whichever is shorter. Certain costs of software developed or obtained for internal use are capitalized and amortized over the estimated useful life of the software. Expenditures for maintenance, repairs, and minor replacements are charged against earnings, as incurred. Expenditures that increase the value or productive capacity of assets are capitalized. When property and equipment are retired, sold, or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in earnings. Goodwill and Identifiable Intangible Assets Goodwill is the cost of acquired companies in excess of the fair value of identifiable net assets at the acquisition date. Goodwill is not subject to amortization, but rather is evaluated for impairment at least annually. The Company evaluates its goodwill for impairment at the fiscal year end (or more frequently if indicators of potential impairment exist) in accordance with ASC 350, Intangibles - Goodwill and Other. Goodwill impairment is determined by comparing the estimated fair value of a reporting unit with its respective carrying value. If the estimated fair value exceeds the carrying value, goodwill at the reporting unit level is not deemed to be impaired. However, if the estimated fair value is below carrying value, further analysis is required to determine the amount of the impairment. This further analysis involves assigning tangible assets and liabilities, identified intangible assets and goodwill to reporting units and comparing the fair value of each reporting unit to its carrying amount. In the course of the evaluation of the potential impairment of goodwill, the Company may perform either a qualitative or a quantitative assessment. The Company’s qualitative assessment of potential impairment may result in the determination that a quantitative impairment analysis is not necessary. Under this elective process, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads the Company to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If after assessing the totality of events or circumstances, the Company determines it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then performing a quantitative analysis is not required. However, if the Company concludes otherwise, then the Company performs a quantitative impairment analysis. If the Company either chooses not to perform a qualitative assessment, or the Company chooses to perform a qualitative assessment but is unable to qualitatively conclude that no impairment has occurred, then the Company performs a quantitative evaluation. In the case of a quantitative assessment, the Company estimates the fair value of the reporting unit which the goodwill that is subject to the quantitative analysis is associated (generally defined as the businesses for which financial information is available and reviewed regularly by management) and compares it to the carrying value. If the estimated fair value of a reporting unit is less than its carrying value, the Company estimates the fair value of all assets and liabilities of the reporting unit, including goodwill. If the carrying value of the reporting unit’s goodwill is greater than the estimated fair value, an impairment charge is recognized for the excess. The fair value of the Company’s reporting units exceeded their respective carrying values under the first step of the quantitative assessment and no impairment charges were recorded for any of the periods presented. Identifiable intangible assets subject to amortization are amortized using the straight-line method over their estimated period of benefit, ranging from five to twenty years. Identifiable intangible assets are tested for impairment whenever events or changes in circumstances suggest that an asset’s or asset group’s carrying

Revenues from contracts with cu

Revenues from contracts with customers (Notes)	12 Months Ended
	Sep. 30, 2019
Revenues from contracts with customers [Abstract]
Revenue from Contract with Customer [Text Block]	Note 2 – Revenue from Contracts with Clients Beginning on October 1, 2018, the Company accounts for revenue earned from contracts with clients for services such as the execution, clearing, brokering, and custody of futures and options on futures contracts, OTC derivatives, and securities, investment management, and underwriting services under Topic 606. As such, revenues for these services are recognized when the performance obligations related to the underlying transaction are completed. Revenues are recognized when control of the promised goods or services are transferred to clients, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Revenues are analyzed to determine whether the Company is the principal (i.e. reports revenue on a gross basis) or agent (i.e., reports revenues on a net basis) in the contract. Principal or agent designations depend primarily on the control an entity has over the good or service before control is transferred to a client. The indicators of which party exercises control include primary responsibility over performance obligations, inventory risk before the good or service is transferred, and discretion in establishing the price. The new revenue recognition model does not apply to revenues associated with dealing, or market-making, activities in financial instruments or contracts in the capacity of a principal, including derivative sales contracts which result in physical settlement and interest income. The Company’s revenues from contracts with clients subject to Topic 606 represent approximately 1.4% , 1.7% , and 1.3% of the Company’s total revenues for the years ended September 30, 2019, 2018, and 2017 respectively. The Company’ revenues from contracts with clients subject to Topic 606 represent approximately 40.9% , 47.4% , and 48.9% of the Company’s operating revenues for the years ended September 30, 2019, 2018, and 2017 , respectively. Revenues within the scope of Topic 606 are presented within ‘Commission and clearing fees’ and ‘Consulting, management, and account fees’ on the consolidated income statements. Revenues that are not within the scope of Topic 606 are presented within ‘sales of physical commodities’, ‘principal gains, net’, and ‘interest income’ on the consolidated income statements. The following table represents a disaggregation of the Company’s total revenues separated between revenues from contracts with clients and other sources of revenue for the years ended September 30, 2019, 2018, and 2017 (in millions): Year Ended September 30, 2019 2018 2017 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 144.9 $ 163.4 $ 129.7 OTC derivative brokerage 32.1 30.3 28.3 Equities and fixed income 16.1 11.2 16.0 Mutual funds 7.5 7.2 7.9 Insurance and annuity products 7.3 5.8 6.0 Other 1.3 0.9 2.0 Total sales-based commission 209.2 218.8 189.9 Trailing: Mutual funds 12.4 13.2 13.1 Insurance and annuity products 14.4 14.6 14.2 Total trailing commission 26.8 27.8 27.3 Clearing fees 118.8 123.3 88.5 Trade conversion fees 7.5 6.8 — Other 10.1 15.1 12.9 Total commission and clearing fees: 372.4 391.8 318.6 Consulting, management, and account fees: Underwriting fees 0.7 1.7 2.3 Asset management fees 26.2 24.8 25.7 Advisory and consulting fees 20.0 19.0 17.7 Sweep program fees 16.3 11.6 6.0 Client account fees 10.6 11.1 10.8 Other 5.8 2.9 2.5 Total consulting, management, and account fees 79.6 71.1 65.0 Total revenues from contracts with clients $ 452.0 $ 462.9 $ 383.6 Method of revenue recognition: Point-in-time $ 362.7 $ 379.7 $ 306.9 Time elapsed 89.3 83.2 76.7 Total revenues from contracts with clients 452.0 462.9 383.6 Other sources of revenues Physical precious metals trading 30,694.5 25,762.9 28,018.4 Physical agricultural and energy product trading 1,135.8 919.5 654.9 Principal gains, net 415.8 354.1 297.0 Interest income 198.9 123.3 69.7 Total revenues $ 32,897.0 $ 27,622.7 $ 29,423.6 The substantial majority of the Company’s performance obligations for revenues from contracts with clients are satisfied at a point in time and are typically collected from clients by debiting their accounts with the Company. Commission and clearing fees revenue is primarily related to the Commercial Hedging and Clearing and Execution Services reportable segments. Consulting, management, and accounts fees are primarily related to the Commercial Hedging, Clearing and Execution Services, and Securities reportable segments. Principal gains, net is primarily related to the Commercial Hedging, Global Payments, and Securities reportable segments. Interest income is primarily related to the Commercial Hedging, Securities, and Clearing and Execution Services reportable segments. Precious metals trading and agricultural and energy merchandising and origination revenues are primarily related to the Physical Commodities reportable segment. Commission and Clearing Fees Commission revenue represents sales and brokerage commissions generated by internal brokers, introducing broker-dealers, or registered investment advisors of introducing-broker dealers for their clients’ trading activity in futures, options on futures, OTC derivatives, fixed income securities, equity securities, mutual funds, and annuities. The Company views the selling, distribution, and marketing, or any combination thereof, of mutual funds and insurance and annuity products to clients on the Company’s registered investment advisor (“RIA”) platform as a single performance obligation to the product sponsors. The Company is the principal for commission revenue, as it is responsible for the execution of the clients’ purchases and sales, and maintains relationships with product sponsors for trailing commission. Introducing broker dealers and registered investment advisors assist the Company in performing its obligations. Accordingly, total commission revenues are reported on a gross basis. The Company primarily generates commission revenue on exchange-traded derivatives, OTC derivatives, and securities. Exchange-traded and OTC derivative commissions are recognized at a point in time on the trade date when the client, either directly or through the use of an internal broker or introducing broker, requests the clearance and execution of a trade. Securities commissions are either sale-based commissions that are recognized at a point in time on the trade date or trailing commission that are recognized over time as earned. Sales-based securities commissions are typically a flat fee per security transaction and in certain instances are based on a percentage of the trade date transaction value. Trailing commission revenue is generally based on a percentage of the periodic fair value of clients’ investment holdings in trail-eligible assets, and is recognized over the period during which services, such as on-going support, are performed. As trailing commission revenue is based on the fair value of clients’ investment holdings in trail-eligible assets, this variable consideration is constrained until the fair value of trail-eligible assets is determinable. Clearing fees generally represent transactional based fees charged by the various exchanges and clearing organizations for which the Company or one of its clearing brokers is a member for the privilege of executing and clearing trades through them. Clearing fees are generally passed through to the clients’ accounts and are reported gross as the Company maintains control over the clearing and execution services provided, maintains relationships with the exchanges or clearing brokers, and has ultimate discretion in whether the fees are passed through to the clients and the rates at which they are passed through. As clearing fees are transactional based revenues they are recognized at a point in time on the trade date along with the related commission revenue when the client requests the clearance and execution of a trade. Trade Conversion Fees Trade conversion fees include revenue earned from converting foreign ordinary equities into an American Depository Receipt (“ADR”) or Global Depository Receipt (“GDR”) and fees earned from converting an ADR or GDR into foreign ordinary equities on behalf of clients. Trade conversion revenue is recognized at a point in time on the trade date. Underwriting Fees Revenues from investment banking consists of revenues earned from underwriting fixed income securities, primarily municipal and asset-backed securities, and are recognized in revenues upon completion of the underlying transaction, which is generally the trade date, based upon the terms of the assignment as the performance obligation is to successfully broker a specific transaction. Asset Management Fees The Company earns asset management fees on Company sponsored and managed mutual funds and on the advisory accounts of independent registered investment advisors on the Company’s platform. The Company provides ongoing investment advice and acts as a custodian, providing brokerage and execution services on transactions, and performs administrative services for these accounts. This series of performance obligations transfers control of the services to the client over time as the services are performed. This revenue is recognized ratably over time to match the continued delivery of the performance obligations to the client over the life of the contract. The asset management revenue generated is based on a percentage of the market value of the eligible assets in the clients’ accounts. As such, the consideration for this revenue is variable and this variable consideration is constrained until the market value of eligible assets in the clients’ accounts is determinable. Advisory and Consulting Fees Advisory and consulting fees are primarily related to risk management consulting fees which are billed and recognized as revenue on a monthly basis when risk management services are provided. Risk management consulting contracts are generally for a minimum term of six months and then continue from month to month, but may be terminated at any time after the original six months by either party upon providing written notice. Advisory and consulting fees are not variable based on client trading activities. This revenue is generally recognized ratably over time to match the continued delivery of the performance obligation to the client over the life of the contract. Sweep Program Fees The Company earns fees generated in lieu of interest income from a multi-bank sweep program with unaffiliated banks and money market funds. Pursuant to contractual arrangements with clients and their introducing-brokers, available cash balances in client accounts are swept into either Federal Deposit Insurance Corporation (“FDIC”) insured cash accounts at unaffiliated banks or unaffiliated money market funds for which the Company earns a portion of the interest income generated by the client balances for administration and recordkeeping. The fees generated by the Company’s multi-bank sweep program are reported net of the balances remitted to the introducing-brokers and the clients of introducing-brokers. These fees are paid and recognized over time to match the continued delivery of the administration and recordkeeping performance obligations to the life of the contract. The fees earned under this program are generally based upon the type of sweep account, prevailing interest rates, and the amount of client balances invested. Client Accounts Fees Client accounts fees represent fees earned for custodial, recordkeeping, and administrative functions performed for the securities clearing accounts of clients. These include statement delivery fees, account transfer fees, safekeeping fees, errors and omission insurance fees, platform fees, and other fees. Client account fees that are transactional based, such as account transfer fees, are recognized at a point in time when the related performance obligation is satisfied. Client account fees that are related to ongoing services, such as statement delivery fees and errors and omission insurance fees, are recognized over time. Client account fees that relate to ongoing services are typically billed to clients’ accounts on a monthly or quarterly basis. Physical Precious Metals Trading The Company principally generates revenue from trading physical precious metals on an OTC basis. Revenues from the sale of physical precious metals are recorded on a trade date basis and generally settle on an unallocated basis. Substantially all of the Company’s sales of precious metals are conducted using sales contracts that meet the definition of derivative instruments in accordance with ASC 815, Derivatives and Hedging (“Topic 815”). The contracts underlying the Company’s commitment to deliver precious metals are referred to as fixed price forward commodity contracts because the price of the commodity is fixed at the time the order is placed. Although the contracts typically are executed on a spot basis and settle on unallocated account, the client has the option to request delivery of the precious metals, the option to net settle out of the position by executing an offsetting trade, or the option to roll the transaction to a subsequent maturity date. Thus, the sales contracts contain embedded option derivatives that would be subject to the guidance in Topic 815. As the contracts are subject to the guidance in Topic 815, the fixed price derivative sales contracts are outside the scope of Topic 606. The Company recognizes revenue when control of the inventory is transferred within the meaning of Topic 606. Physical precious metals trading revenue generated by registered broker-dealer subsidiaries are presented on a net basis and included as a component of ‘Principal gains, net’ in the consolidated income statements, in accordance with U.S GAAP accounting requirements for broker-dealers. Physical precious metals trading revenue for subsidiaries that are not broker-dealers continue to be recorded on a gross basis. Physical Agricultural and Energy Product Trading The Company principally generates revenue from merchandising and originating physical agricultural and energy commodities from forward firm sales commitments accounted in accordance with Topic 815. The fixed and provisionally-priced derivative sales contracts that result in physical delivery are outside the scope of Topic 606. The Company recognizes revenue when control of the inventory is transferred within the meaning of Topic 606. Principal Gains, Net Principal gains, net includes revenues on financial transactions or contracts for which the Company acts as principal that is reported on a net basis and is primarily outside the scope of ASC 606. Principal gains, net includes margins generated from OTC derivative trades, equities, fixed income, precious metals, and foreign exchange executed with clients and other counterparties and are recognized on a trade-date basis. Principal gains, net, also includes realized and unrealized gains and losses derived principally from market making activities in OTC derivatives, equities, fixed income, and foreign exchange. Net dealer inventory and investment gains are recognized on a trade-date basis and include realized gains or losses and changes in unrealized gains or losses on investments at fair value. Principal gains, net also includes dividend income on long equity positions and dividend expense on short equity positions, which are recognized on the ex-dividend date. Interest Income Interest income is generated from client funds deposited with the Company to satisfy margin requirements which is held by third-party banks or on deposit with or pledged to exchange-clearing organizations or other FCMs. Interest income is also generated from the investment of client funds in allowable securities, primarily U.S. Treasury obligations. Interest income is also generated from trading fixed income securities that the Company holds in its market-making businesses. Interest income also includes interest generated from collateralized transactions, including securities borrowed and securities purchased under agreements to resell, and from extending margin loans to clients. Interest income is recognized on an accrual basis and is not within the scope of Topic 606. Remaining Performance Obligations Remaining performance obligations are services that the firm has committed to perform in the future in connection with its contracts with clients. The Company’s remaining performance obligations are generally related to its risk management consulting and asset management contracts with clients. Revenues associated with remaining performance obligations related to these contracts with clients are not material to the overall consolidated results of the Company. Similar to above, risk management consulting contracts are generally for a minimum term of six months and then continue from month to month, but may be terminated at any time after the original six months by either party upon providing written notice. Asset management contracts may be terminated by the client at any time. For the Company’s asset management activities, where fees are calculated based on a percentage of the market value of eligible assets in client’s accounts, future revenue associated with remaining performance obligations cannot be determined as such fees are subject to fluctuations in the market value of eligible assets in clients’ accounts. Practical Expedients The Company has applied Topic 606’s practical expedient that permits for the non-disclosure of the value of performance obligations for (i) contracts with an original expected length or one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which is has the right to invoice for services performed. The Company has also applied Topic 606’s practical expedient that allows for no adjustment to consideration due to a significant financing component if the expectation at contract inception is such that the period between payment by the client and the transfer of the promised goods or services to the client will be one year or less.

Earnings per Share (Notes)

Earnings per Share (Notes)	12 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	The Company presents basic and diluted earnings per share (“EPS”) using the two-class method which requires all outstanding unvested share-based payment awards that contain rights to non-forfeitable dividends and therefore participate in undistributed earnings with common stockholders be included in computing earnings per share. Under the two-class method, net income is reduced by the amount of dividends declared in the period for each class of common stock and participating security. The remaining undistributed earnings are then allocated to common stock and participating securities, based on their respective rights to receive dividends. Restricted stock awards granted to certain employees and directors contain non-forfeitable rights to dividends at the same rate as common stock, and are considered participating securities. Basic EPS has been computed by dividing net income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted net income per share computations for the periods presented below. Year Ended September 30, (in millions, except share amounts) 2019 2018 2017 Numerator: Net income $ 85.1 $ 55.5 $ 6.4 Less: Allocation to participating securities (1.5 ) (0.9 ) (0.1 ) Net income allocated to common stockholders $ 83.6 $ 54.6 $ 6.3 Denominator: Weighted average number of: Common shares outstanding 18,738,905 18,549,011 18,395,987 Dilutive potential common shares outstanding: Share-based awards 275,490 385,819 291,367 Diluted shares outstanding 19,014,395 18,934,830 18,687,354 The dilutive effect of share-based awards is reflected in diluted net income per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense. Options to purchase 907,089 , 92,627 and 230,135 shares of common stock for fiscal years ended September 30, 2019, 2018, and 2017 , respectively, were excluded from the calculation of diluted earnings per share because they would have been anti-dilutive.

Assets and Liabilities, at Fair

Assets and Liabilities, at Fair Value (Notes)	12 Months Ended
	Sep. 30, 2019
Assets and Liabilities, at Fair Value [Abstract]
Fair Value Disclosures [Text Block]	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 based on prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). 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. Level 3 includes contingent liabilities that have been valued using an income approach based upon management developed discounted cash flow projections, which are an unobservable input. The Company had $1.8 million and zero of contingent liabilities classified within Level 3 of the fair value hierarchy as of September 30, 2019 and 2018 , respectively. The Company had no Level 3 assets as of September 30, 2019 and 2018 . 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 from 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 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 and money market mutual funds, 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 clients and broker-dealers, clearing organizations and counterparties includes the fair 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 OTC forwards, swaps, and options. Financial instruments owned and sold, not yet purchased include the fair value of equity securities, which includes common, preferred, and foreign ordinary shares, American Depository Receipts (“ADRs”), Global Depository Receipts (“GDRs”), and exchange-traded funds (“ETFs”), corporate and municipal bonds, 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 investments in managed funds. The fair value of exchange firm common stock is determined by quoted market prices. Cash equivalents, debt and equity 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, foreign government obligations, commodities warehouse receipts, certain equity securities traded in active markets, physical precious metals inventory held by a regulated broker-dealer subsidiary, exchange firm common stock, investments in managed funds, as well as options on futures contracts traded on national exchanges. The fair value of exchange firm common stock 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 corporate and municipal bonds, U.S. government agency obligations, agency-mortgage backed obligations, asset-backed obligations, certain equity securities traded in less active markets, and OTC derivative contracts, which include purchase and sale commitments related to the Company’s agricultural and energy commodities. Certain 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. Physical commodities inventory includes precious metals that are a part of the trading activities of a regulated broker-dealer subsidiary and is recorded at fair value using exchange-quoted prices. Physical commodities inventory also includes agricultural commodities that are a part of the trading activities of a non-broker dealer subsidiary and are recorded at net realizable value using exchange-quoted prices. The fair value of precious metals physical commodities inventory is based upon unadjusted exchange-quoted prices and is, therefore, classified within Level 1 of the fair value hierarchy. The fair value of agricultural physical commodities inventory and the related OTC firm sale and purchase commitments are generally based upon exchange-quoted prices, adjusted for basis or differences in local markets, broker or dealer quotations or market transactions in either listed or OTC markets. Exchange-quoted prices are adjusted for location and quality because the exchange-quoted prices for agricultural and energy related products represent contracts that have standardized terms for commodity, quantity, future delivery period, delivery location, and commodity quality or grade. The basis or local market adjustments are observable inputs or have an insignificant impact on the measurement of fair value and, therefore, the agricultural physical commodities inventory as well as the related OTC forward firm sale and purchase commitments have been included within Level 2 of the fair value hierarchy. With the exception of certain derivative instruments where the valuation approach is disclosed above, financial instruments owned and sold are primarily valued using third-party pricing sources. Third-party pricing vendors compile prices from various sources and often apply matrix pricing for similar securities when market-observable transactions for the instruments are not observable for substantially the full term. The Company reviews the pricing methodologies used by third-party pricing vendors in order to evaluate the fair value hierarchy classification of vendor-priced financial instruments and the accuracy of vendor pricing, which typically involves the comparison of primary vendor prices to internal trader prices or secondary vendor prices. When evaluating the propriety of vendor-priced financial instruments using secondary prices, considerations include the range and quality of vendor prices, level of observable transactions for identical and similar instruments, and judgments based upon knowledge of a particular market and asset class. If a primary vendor price does not represent fair value, justification for using a secondary price, including source data used to make the determination, is subject to review and approval by authorized personnel prior to using a secondary price. Financial instruments owned and sold that are valued using third-party pricing vendors 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. The fair value estimates presented herein are based on pertinent information available to management as of September 30, 2019 and 2018 . 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 consolidated 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 September 30, 2019 and September 30, 2018 by level in the fair value hierarchy. Except as disclosed in Note 7 , there were no assets or liabilities that were measured at fair value on a nonrecurring basis as of September 30, 2019 and 2018 . September 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 4.9 $ — $ — $ — $ 4.9 Money market mutual funds 8.9 — — — 8.9 Cash and cash equivalents 13.8 — — — 13.8 Commodities warehouse receipts 6.2 — — — 6.2 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 306.0 — — — 306.0 U.S. Treasury obligations 593.9 — — — 593.9 "To be announced" (TBA) and forward settling securities — 9.8 — (1.5 ) 8.3 Foreign government obligations 9.9 — — — 9.9 Derivatives 3,131.2 43.2 — (3,159.6 ) 14.8 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,735.0 53.0 — (3,161.1 ) 626.9 Equity securities 159.5 9.0 — — 168.5 Corporate and municipal bonds — 80.0 — — 80.0 U.S. Treasury obligations 248.7 — — — 248.7 U.S. government agency obligations — 447.1 — — 447.1 Foreign government obligations 0.5 — — — 0.5 Agency mortgage-backed obligations — 1,045.0 — — 1,045.0 Asset-backed obligations — 29.1 — — 29.1 Derivatives 1.0 486.3 — (420.8 ) 66.5 Commodities leases — 28.6 — — 28.6 Commodities warehouse receipts 48.4 — — — 48.4 Exchange firm common stock 12.7 — — — 12.7 Mutual funds and other 0.1 — — — 0.1 Financial instruments owned 470.9 2,125.1 — (420.8 ) 2,175.2 Physical commodities inventory 7.1 144.8 — — 151.9 Total assets at fair value $ 4,532.8 $ 2,322.9 $ — $ (3,581.9 ) $ 3,273.8 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.8 $ — $ 1.8 TBA and forward settling securities — 6.8 — (1.5 ) 5.3 Derivatives 3,079.1 38.3 — (3,117.1 ) 0.3 Payable to broker-dealers, clearing organizations and counterparties 3,079.1 45.1 — (3,118.6 ) 5.6 Equity securities 147.3 10.8 — — 158.1 Foreign government obligations — — — — — Corporate and municipal bonds — 39.2 — — 39.2 U.S. Treasury obligations 272.3 — — — 272.3 U.S. government agency obligations — 43.8 — — 43.8 Agency mortgage-backed obligations — 29.6 — — 29.6 Derivatives 480.3 — (422.2 ) 58.1 Commodities leases $ — $ 113.7 $ — $ — $ 113.7 Financial instruments sold, not yet purchased 419.6 717.4 — (422.2 ) 714.8 Total liabilities at fair value $ 3,498.7 $ 762.5 $ 1.8 $ (3,540.8 ) $ 722.2 (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 are included in that level. September 30, 2018 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Cash and cash equivalents - certificaes of deposit $ 3.8 $ — $ — $ — $ 3.8 Commodities warehouse receipts 42.9 — — — 42.9 U.S. Treasury obligations 600.4 — — — 600.4 Securities and other assets segregated under federal and other regulations 643.3 — — — 643.3 U.S. Treasury obligations 778.4 — — — 778.4 TBA and forward settling securities — 5.0 — (2.1 ) 2.9 Foreign government obligations 7.7 — — — 7.7 Derivatives 7,495.9 19.6 — (7,787.1 ) (271.6 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 8,282.0 24.6 — (7,789.2 ) 517.4 Equity securities 71.2 3.0 — — 74.2 Corporate and municipal bonds — 79.1 — — 79.1 U.S. Treasury obligations 120.1 — — — 120.1 U.S. government agency obligations — 472.9 — — 472.9 Foreign government obligations 6.4 — — — 6.4 Agency mortgage-backed obligations — 1,022.5 — — 1,022.5 Asset-backed obligations — 42.9 — — 42.9 Derivatives 0.8 514.6 — (329.3 ) 186.1 Commodities leases — 29.5 — (11.8 ) 17.7 Commodities warehouse receipts 16.4 — — — 16.4 Exchange firm common stock 10.2 — — — 10.2 Mutual funds and other 6.3 — — — 6.3 Financial instruments owned 231.4 2,164.5 — (341.1 ) 2,054.8 Physical commodities inventory 42.1 114.8 — — 156.9 Total assets at fair value $ 9,202.6 $ 2,303.9 $ — $ (8,130.3 ) $ 3,376.2 Liabilities: TBA and forward settling securities $ — $ 2.1 $ — $ (2.1 ) $ — Derivatives 7,809.3 11.6 — (7,820.9 ) — Payable to broker-dealers, clearing organizations and counterparties 7,809.3 13.7 — (7,823.0 ) — Equity securities 51.1 0.4 — — 51.5 Corporate and municipal bonds — 20.1 — — 20.1 U.S. Treasury obligations 484.8 — — — 484.8 U.S. government agency obligations — 57.2 — — 57.2 Agency mortgage-backed obligations — 0.2 — — 0.2 Derivatives 688.0 — (494.6 ) 193.4 Commodities leases — 75.5 — (16.2 ) 59.3 Financial instruments sold, not yet purchased 535.9 841.4 — (510.8 ) 866.5 Total liabilities at fair value $ 8,345.2 $ 855.1 $ — $ (8,333.8 ) $ 866.5 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level. Realized and unrealized gains and losses are included in ‘principal gains, net’, ‘interest income’, and ‘cost of sales of physical commodities’ in the consolidated income statements. Information on Level 3 Financial Assets and Liabilities 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 years ended September 30, 2019 and 2018 , including a summary of unrealized gains (losses) during the fiscal year ended on the Company’s Level 3 financial assets and liabilities held during the periods. Level 3 Financial Liabilities (in millions) Balances at Realized (gains) Remeasurement Acquisitions Settlements Transfers in Balances at Liabilities: Contingent liabilities $ — $ — $ — $ 1.8 $ — $ — $ 1.8 Level 3 Financial Assets and Financial Liabilities (in millions) Balances at Realized gains Unrealized Purchases/ Settlements Transfers in Balances at Assets: Equity securities $ 0.1 $ — $ (0.1 ) $ — $ — $ — $ — (in millions) Balances at Realized (gains) Remeasurement Acquisitions Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 1.0 $ — $ — $ — $ (1.0 ) $ — $ — The Company was 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 the contingent consideration 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 contingency period for the contingent consideration ended as of December 31, 2017, and the accrued balance of $1.0 million was paid during the year ended September 30, 2018. The acquisition of Fillmore Advisors, LLC, as further discussed in Note 20 , included a contingent consideration arrangement as a component of the purchase price. Pursuant to the contingent consideration agreement, the Company is required to make additional future cash payments based on certain financial performance measures of the acquired business. As of September 30, 2019, the Company has 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 fair value of an exchange-traded options on futures contract is equal to the unrealized gain or loss on the contract determined by marking the contract to the current settlement price for a like contract on the valuation date of the contract. A settlement price may not be used if the market makes a limit move with respect to a particular options on futures contract or if the contract’s underlying experiences significant price fluctuations after the determination of the settlement price. When a settlement price cannot be used, options on futures contracts will be valued at their fair value as determined in good faith pursuant to procedures adopted by management of the Company. The Company has classified equity investments in exchange firms’ common stock not pledged for clearing purposes as trading securities. The investments are recorded at fair value, with unrealized gains and losses recorded, net of taxes, included in earnings. As of September 30, 2019 , the cost and fair value of the equity investments in exchange firms is $3.7 million and $12.7 million , respectively. As of September 30, 2018 , the cost and fair value of the equity investments in exchange firms was $3.7 million and $10.2 million , respectively. Additional disclosures about the fair value of financial instruments that are not carried on the 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 Consolidated Balance Sheets. The following represents financial instruments in which the ending balance at September 30, 2019 and 2018 was not carried at fair value in accordance with U.S. GAAP on our 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, or short-term in nature, 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 clients, 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 clients 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. Senior secured term loan, net : The senior secured term loan carries a variable rate of interest and thus approximates fair value and is 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)	12 Months Ended
	Sep. 30, 2019
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	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 consolidated financial statements as of September 30, 2019 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 September 30, 2019 . The total of $714.8 million as of September 30, 2019 includes $58.1 million for derivative contracts, which represent a liability to the Company based on their fair values as of September 30, 2019 . Derivatives The Company utilizes derivative products in its trading capacity as a dealer in order to satisfy client needs and mitigate risk. The Company manages risks from both derivatives and non-derivative cash instruments on a consolidated basis. The risks of derivatives should not be viewed in isolation, but in aggregate with the Company’s other trading activities. The Company’s derivative positions are included in the consolidating balance sheets in ‘deposits with and receivables from broker-dealers, clearing organizations, and counterparties’, ‘financial instruments owned and sold, not yet purchased, at fair value’ and ‘payables to broker-dealers, clearing organizations and counterparties’. Listed below are the fair values of the Company’s derivative assets and liabilities as of September 30, 2019 and 2018 . Assets represent net unrealized gains and liabilities represent net unrealized losses. September 30, 2019 September 30, 2018 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,437.1 $ 1,463.4 $ 2,455.7 $ 2,499.3 OTC commodity derivatives 84.2 106.2 207.0 369.9 Exchange-traded foreign exchange derivatives 36.9 33.5 49.8 37.2 OTC foreign exchange derivatives 403.2 368.8 302.5 303.9 Exchange-traded interest rate derivatives 900.1 882.0 449.3 478.7 OTC interest rate derivatives 42.1 43.6 24.8 25.9 Exchange-traded equity index derivatives 758.1 700.2 4,541.8 4,794.0 TBA and forward settling securities 9.8 6.8 5.0 2.1 Gross fair value of derivative contracts 3,671.5 3,604.5 8,035.9 8,511.0 Impact of netting and collateral (3,581.9 ) (3,540.8 ) (8,118.5 ) (8,317.6 ) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties' $ 23.1 $ (268.7 ) Total fair value included in 'Financial instruments owned, at fair value $ 66.5 $ 186.1 Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties $ 5.6 $ — Fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 58.1 $ 193.4 (1) As of September 30, 2019 and 2018 , the Company’s derivative contract volume for open positions was approximately 10.6 million contracts. The Company’s derivative contracts are principally held in its Commodities and Risk Management Services (“Commercial Hedging”) segment. The Company assists its Commercial Hedging segment clients 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 clients with option products, including combinations of buying and selling puts and calls. The Company mitigates its risk by generally offsetting the client’s transaction simultaneously with one of the Company’s trading counterparties or will offset that transaction with a similar but not identical position on the exchange. The risk mitigation of these offsetting trades is not within the documented hedging designation requirements of the Derivatives and Hedging Topic of the ASC. These derivative contracts are traded along with cash transactions because of the integrated nature of the markets for these products. The Company manages the risks associated with derivatives on an aggregate basis along with the risks associated with its proprietary trading and market-making activities in cash instruments as part of its firm-wide risk management policies. In particular, the risks related to derivative positions may be partially offset by inventory, unrealized gains in inventory or cash collateral paid or received. The Company transacts in derivative instruments, which consist of futures, mortgage-backed TBA securities and forward settling transactions, that are used to manage risk exposures in the Company’s fixed income portfolio. The fair value of these transactions is recorded in deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘principal 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. As of September 30, 2019 and 2018 , TBA and forward settling securities recorded within deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties are summarized as follows (in millions): September 30, 2019 September 30, 2018 Gain/(Loss) Notional Amounts Gain/(Loss) Notional Amounts Unrealized gain on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 3.7 $ 1,778.4 $ 1.2 $ 721.5 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.6 ) $ 234.5 $ (0.6 ) $ 293.2 Unrealized gain on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ 3.2 $ (1,099.5 ) Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ 0.9 $ (451.6 ) $ — $ — Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (5.9 ) $ (2,788.0 ) $ — $ — Unrealized loss on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ (1.5 ) $ (812.7 ) Unrealized gain on forward settling securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ 0.5 $ 614.3 Unrealized loss on forward settling securities purchased within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.3 ) $ 1,243.5 $ — $ — Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 5.2 $ (581.2 ) $ 0.1 $ (427.2 ) The notional amounts of these instruments reflect the extent of the Company’s involvement in TBA and forward settling securities and do not represent counterparty exposure. The following table sets forth the Company’s net gains (losses) related to derivative financial instruments for the fiscal years ended September 30, 2019, 2018, and 2017 , in accordance with the Derivatives and Hedging Topic of the ASC. The net gains (losses) set forth below are included in ‘principal gains, net’ and ‘cost of sales of physical commodities’ in the consolidated income statements. Year Ended September 30, (in millions) 2019 2018 2017 Commodities $ 100.8 $ 94.0 $ 47.3 Foreign exchange 8.1 9.2 8.7 Interest rate and equity (2.6 ) 1.0 (0.1 ) TBA and forward settling securities (35.3 ) 14.5 (2.5 ) Net gains from derivative contracts $ 71.0 $ 118.7 $ 53.4 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 clients. If either the client 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, clients, broker-dealers and other financial institutions. These activities primarily involve collateralized and uncollateralized arrangements and may result in credit exposure in the event that a counterparty fails to meet its contractual obligations. The Company’s exposure to credit risk can be directly impacted by volatile financial markets, which may impair the ability of counterparties to satisfy their contractual obligations. The Company seeks to control its credit risk through a variety of reporting and control procedures, including establishing credit limits based upon a review of the counterparties’ financial condition and credit ratings. The Company monitors collateral levels on a daily basis for compliance with regulatory and internal guidelines and requests changes in collateral levels as appropriate. The Company is a party to financial instruments in the normal course of its business through client and proprietary trading accounts in exchange-traded and OTC derivative instruments. These instruments are primarily the execution of orders for commodity futures, options on futures and forward foreign currency contracts on behalf of its clients, 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 clients may incur. The Company controls the risks associated with these transactions by requiring clients to maintain margin deposits in compliance with individual exchange regulations and internal guidelines. The Company monitors required margin levels daily and, therefore, may require clients to deposit additional collateral or reduce positions when necessary. The Company also establishes credit limits for clients, which are monitored daily. The Company evaluates each client’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 clients and counterparties are subject to master netting, or client agreements, which reduce the exposure to the Company by permitting receivables and payables with such clients to be offset in the event of a client default. Management believes that the margin deposits held as of September 30, 2019 and September 30, 2018 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. 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 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 commodity pricing and 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)	12 Months Ended
	Sep. 30, 2019
Receivables from customers and notes receivable, net [Abstract]
Receivables from Customers and Notes Receivable [Text Block]	Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net, receivables from clients, net, and notes receivable, net include an allowance for doubtful accounts, which reflects the Company’s best estimate of probable losses inherent in the accounts. The Company provides for an allowance for doubtful accounts based on a specific-identification basis. The Company continually reviews its allowance for doubtful accounts. The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $36.9 million and $48.0 million as of September 30, 2019 and 2018 , respectively. The allowance for doubtful accounts related to receivables from clients was $11.7 million and $10.2 million as of September 30, 2019 and 2018 , respectively. The Company had no allowance for doubtful accounts related to notes receivable as of September 30, 2019 and 2018 . During the year ended September 30, 2019 , the Company recorded bad debt expense, net of recoveries, of $2.5 million , including a net increase in provisions for bad debt of $2.6 million , direct write-offs of $0.3 million , and direct recoveries of $0.4 million . The net increase in provision for bad debts during fiscal 2019 primarily related to $2.7 million of OTC client account deficits in the Commercial Hedging segment, and $1.4 million in the Clearing & Execution Services segment, partially offset by a client recovery across the Commercial Hedging segment and the Physical Commodities segment. Additionally, during the year ended September 30, 2019, the Company recorded recoveries on the bad debt on physical coal of $12.4 million , reducing the allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties. See additional information in Note 18 . During the year ended September 30, 2018 , the Company recorded bad debt expense, net of recoveries, of $3.1 million , including a net increase in provision for bad debts of $2.9 million , direct write-offs of $0.3 million , and recoveries of $0.1 million . The increase in provision for bad debts during fiscal 2018 primarily related to $2.8 million of agricultural OTC client account deficits in the Commercial Hedging segment and $0.4 million of exchange-traded client account deficits in the Clearing & Execution Services segment, partially offset by a provision decrease in the Physical Commodities segment. Additionally, during the year ended September 30, 2018, the Company recorded charges to earnings of $1.0 million , to record an additional allowance for doubtful accounts related to a bad debt incurred in the physical coal business, see Note 18 . During the year ended September 30, 2017, the Company recorded bad debt expense, net of recoveries, of $4.3 million , including provision increases of $4.2 million and direct write-offs of $0.1 million . The increase in bad debts during fiscal 2017 primarily related to $3.8 million of client deficits in the Commercial Hedging segment, primarily related to account deficits from South Korean and Dubai commercial LME clients, $0.2 million of uncollectible client receivables in the Physical Commodities segment, and $0.3 million of uncollectible client receivables in the Clearing & Execution Services segment. Additionally, during the year ended September 30, 2017, the Company recorded charges to earnings of $47.0 million to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business conducted solely in INTL Asia Pte. Ltd., with a coal supplier (counterparty), as further discussed in Note 18 . Activity in the allowance for doubtful accounts for the fiscal years ended September 30, 2019, 2018, and 2017 was as follows: (in millions) 2019 2018 2017 Balance, beginning of year $ 58.2 $ 54.6 $ 9.7 (Recovery) provision for bad debts (9.8 ) 3.9 51.0 Allowance charge-offs (1.3 ) (0.3 ) (6.1 ) Other (1) 1.5 — — Balance, end of year $ 48.6 $ 58.2 $ 54.6 (1) Allowance increase is related to a recoverable amount due from an affiliated party and recorded in ‘other assets’ on the consolidated balance sheets.

Physical Commodities Inventory

Physical Commodities Inventory (Notes)	12 Months Ended
	Sep. 30, 2019
Physical Commodities Inventory [Abstract]
Inventory Disclosure [Text Block]	The Company’s inventories consist of finished physical commodities. Inventories by component of the Company’s Physical Commodities segment are shown below. (in millions) September 30, September 30, Physical Ag & Energy (1) $ 144.8 $ 114.7 Precious metals - held by broker-dealer subsidiary (2) 7.1 42.1 Precious metals - held by non-broker-dealer subsidiaries (3) 77.4 65.7 Physical commodities inventory $ 229.3 $ 222.5 (1) Physical Ag & Energy consists of 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 selling prices in the ordinary course of business, less disposal costs, with changes in net realizable value included as a component of ‘cost of sales of physical commodities’ on the 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 consists of energy related inventories, including primarily propane, gasoline, and kerosene, which are valued at the lower of cost or net realizable value. (2) Precious metals held by the Company’s subsidiary, INTL FCStone Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ on the 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 value adjustments for certain precious metals inventory of $0.5 million and $0.4 million as of September 30, 2019 and 2018 , respectively. The adjustments are included in ‘cost of sales of physical commodities’ in the consolidated income statements.

Property and Equipment, net (No

Property and Equipment, net (Notes)	12 Months Ended
	Sep. 30, 2019
Property and Equipment, net [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	Property and equipment are stated at cost, and reported net of accumulated depreciation on the consolidated balance sheets. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful lives of the assets. The estimated useful lives of property and equipment range from 3 to 10 years. During the fiscal years ended September 30, 2019, 2018, and 2017 , depreciation expense was $11.2 million , $9.4 million , and $7.0 million , respectively. A summary of property and equipment, at cost less accumulated depreciation as of September 30, 2019 and 2018 is as follows: (in millions) September 30, 2019 September 30, 2018 Property and equipment: Furniture and fixtures $ 10.6 $ 8.7 Software 33.9 30.5 Equipment 28.1 24.7 Leasehold improvements 20.3 17.0 Total property and equipment 92.9 80.9 Less accumulated depreciation (49.0 ) (38.5 ) Property and equipment, net $ 43.9 $ 42.4

Goodwill (Notes)

Goodwill (Notes)	12 Months Ended
	Sep. 30, 2019
Goodwill [Abstract]
Goodwill Disclosure [Text Block]	Goodwill allocated to the Company’s operating segments as of September 30, 2019 and 2018 is as follows: (in millions) September 30, September 30, Commerical Hedging $ 30.3 $ 30.3 Global Payments 7.6 8.9 Physical Commodities 4.6 2.4 Securities 8.7 6.8 Goodwill $ 51.2 $ 48.4 The Company recorded zero and $1.3 million in foreign exchange revaluation losses on goodwill for the years ended September 30, 2019 and 2018 , respectively. The Company recorded a reduction to goodwill of $1.3 million during the year ended September 30, 2019 within the Global Payments operating segment related to measurement period adjustments on the acquisition of INTL Technology Services, LLC (formerly PayCommerce Financial Solutions, LLC) and in connection with the joint venture transaction discussed in Note 20 . The Company recorded additional goodwill of $2.2 million during the year ended September 30, 2019 within the Physical Commodities operating segment related to the acquisition of CoinInvest GmbH and European Precious Metal Trading GmbH as discussed in Note 20 . The Company recorded additional goodwill of $1.9 million during the year ended September 30, 2019 within the Securities operating segment related to the acquisition of Fillmore Advisors, LLC as discussed in Note 20 .

Intangible Assets (Notes)

Intangible Assets (Notes)	12 Months Ended
	Sep. 30, 2019
Intangible Assets [Abstract]
Intangible Assets Disclosure [Text Block]	Intangible Assets During the year ended September 30, 2019 , the Company recorded a definite-lived intangible asset subject to amortization of $2.6 million for internally developed software acquired through the acquisition of CoinInvest GmbH and European Precious Metal Trading GmbH. The Company also recorded indefinite-lived intangible assets not subject to amortization of $2.1 million for website domains acquired through the acquisition of CoinInvest GmbH and European Precious Metal Trading GmbH. See Note 20 - Acquisitions for further discussion. During the year ended September 30, 2019 , the Company recorded a definite-lived intangible asset subject to amortization of $0.7 million for client base assets acquired through the acquisition of Fillmore Advisors, LLC. See Note 20 - Acquisitions for further discussion. During the year ended September 30, 2019 , the Company recorded an indefinite-lived intangible asset not subject to amortization of $2.7 million related to the acquisition of Akshay Financeware, Inc. See Note 20 - Acquisitions for further discussion. 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): September 30, 2019 September 30, 2018 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization: Software programs/platforms $ 5.3 $ (3.0 ) $ 2.3 $ 2.7 $ (2.6 ) $ 0.1 Client base 22.1 (12.5 ) 9.6 21.4 (10.1 ) 11.3 Total intangible assets subject to amortization 27.4 (15.5 ) 11.9 24.1 (12.7 ) 11.4 Intangible assets not subject to amortization: Website domains 2.1 — 2.1 — — — Business licenses 2.7 — 2.7 — — — Total intangible assets not subject to amortization 4.8 — 4.8 — — — Total intangible assets $ 32.2 $ (15.5 ) $ 16.7 $ 24.1 $ (12.7 ) $ 11.4 Amortization expense related to intangible assets was $2.8 million , $2.3 million , and $2.8 million for the years ended September 30, 2019, 2018, and 2017 , respectively. As of September 30, 2019 , the estimated future amortization expense was as follows: (in millions) Fiscal 2020 $ 2.9 Fiscal 2021 2.9 Fiscal 2022 1.6 Fiscal 2023 1.4 Fiscal 2024 and thereafter 3.1 $ 11.9

Credit Facilities (Notes)

Credit Facilities (Notes)	12 Months Ended
	Sep. 30, 2019
Credit Facilities [Abstract]
Debt Disclosure [Text Block]	Committed Credit Facilities The Company has four committed credit facilities, including a senior secured term loan, under which the Company and its subsidiaries may borrow up to $743.9 million , subject to the terms and conditions for these facilities. The amounts outstanding under these credit facilities carry variable rates of interest, thus approximating fair value. The Company’s committed credit facilities consist of the following: • A three-year first-lien senior secured syndicated loan facility under which $386.4 million is available to the Company for general working capital requirements and capital expenditures. On February 22, 2019, the Company amended its existing $262.0 million senior secured syndicated credit facility, to extend the maturity date through February 2022 and to increase the size of the facility to $350.0 million . Subsequent to September 30, 2019 , additional members were added to the syndication further increasing the committed amount to $393.0 million . The amended facility is comprised of a $196.5 million revolving credit facility and a $196.5 million Term Loan facility. The Company is required to make quarterly principal payments against the Term Loan equal to 1.25% of the original balance with the remaining balance due on the maturity date. During the year ended September 30, 2019 , the Company made three scheduled quarterly principal payments against the Term Loan equal to $6.6 million , reducing the amount outstanding to $168.4 million as of September 30, 2019 . Amounts repaid on the Term Loan may not be reborrowed. During the year ended September 30, 2019 , the Company paid $3.1 million in rating agency fees, arrangement fees, commitment fees, and other deferred financing costs in connection with amending the credit facility. These deferred financing costs are being amortized over the 36 month term of the amended credit facility. The credit facility is secured by a first priority lien on substantially all of the assets of the Company and those of our subsidiaries that guarantee the credit facility. Per the terms of the amended facility, the commitment fees and interest rates are subject to decrease if the Company’s consolidated leverage ratio, as defined, decreases below certain thresholds. As of September 30, 2019 , unused portions of the loan facility require a commitment fee of 0.625% on the unused commitment. Both the revolving credit facility and the Term Loan are subject to variable rates of interest. As of September 30, 2019 , borrowings under the facility bear interest at the Eurodollar Rate, as defined, plus 3.00% or the Base Rate, as defined, plus 2.00% . Borrowings under the Base Rate and Eurodollars options were subject to interest rates of 7.25% and 4.95% , respectively, as of September 30, 2019 . The agreement contains financial covenants related to consolidated tangible net worth, consolidated funded debt to net worth ratio, consolidated fixed charge coverage ratio and consolidated net unencumbered liquid assets, as defined. The agreement also contains a non-financial covenant related to the allowable annual consolidated capital expenditures permitted under the agreement. The Company was in compliance with all covenants under the loan facility as of September 30, 2019 . • An unsecured syndicated committed line of credit under which $75.0 million is available to the Company’s wholly owned subsidiary, INTL FCStone Financial to provide short term funding of margin to commodity exchanges as necessary. This line of credit is subject to annual review, and the continued availability of this line of credit is subject to INTL FCStone Financial’s financial condition and operating results continuing to be satisfactory as set forth in the agreement. Unused portions of the margin line require a commitment fee of 0.50% on the unused commitment. Borrowings under the margin line are on a demand basis and bear interest at the Base Rate, as defined, plus 2.00% , which was 7.25% as of September 30, 2019 . The agreement contains financial covenants related to INTL FCStone Financial’s tangible net worth, excess net capital and maximum net loss over a trailing twelve month period, as defined. INTL FCStone Financial was in compliance with these covenants as of September 30, 2019 . The facility is guaranteed by the Company. • A syndicated committed borrowing facility under which $232.5 million is available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC (“FCStone Merchants”) to finance commodity financing arrangements and commodity repurchase agreements. The facility is secured by the assets of FCStone Merchants, and guaranteed by the Company. Unused portions of the borrowing facility require a commitment fee of 0.38% on the unused commitment. The borrowings outstanding under the facility bear interest at a rate per annum equal to the Eurodollar Rate plus Applicable Margin, as defined, or the Base Rate plus Applicable Margin, as defined. Borrowings under the Base Rate and Eurodollar options were subject to interest rates of 5.0% and 4.5% , respectively, as of September 30, 2019 . The agreement contains financial covenants related to tangible net worth, as defined. FCStone Merchants was in compliance with this covenant as of September 30, 2019 . • An unsecured syndicated committed borrowing facility under which $50.0 million is available to the Company’s wholly owned subsidiary, INTL FCStone Ltd for short term funding of margin to commodity exchanges. The borrowings outstanding under the facility bear interest at a rate per annum equal to 2.50% plus the Federal Funds Rate, as defined. The agreement contains financial covenants related to consolidated tangible net worth, as defined. INTL FCStone Ltd was in compliance with this covenant as of September 30, 2019 . The facility is guaranteed by the Company. Uncommitted Credit Facilities The Company has a secured, uncommitted loan facility, under which INTL FCStone Financial may borrow up to $75.0 million , collateralized by commodities warehouse receipts, to facilitate U.S. commodity exchange deliveries of its clients, subject to certain terms and conditions of the credit agreement. There were no borrowings outstanding under this credit facility at September 30, 2019 and 2018 . The Company has a secured, uncommitted loan facility, under which INTL FCStone Financial Inc. may borrow for short term funding of proprietary and client 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 Company owned marketable securities or client owned securities which have been pledged to the Company. The amounts borrowed under the facilities are payable on demand. There were zero and $14.0 million in borrowings outstanding under this credit facility as of September 30, 2019 , and September 30, 2018 , respectively. The Company has secured uncommitted loan facilities under which INTL FCStone Financial may borrow up to $100.0 million for short term funding of proprietary and client securities margin requirements, subject to certain terms and conditions of the agreement. The borrowings are secured by first liens on Company owned marketable securities or client owned securities which have been pledged to the Company. The amounts borrowed under the facilities are payable on demand. There were no borrowings outstanding under this credit facility as of September 30, 2019 and September 30, 2018 . The Company has a secured, uncommitted loan facility, under which FCStone Merchant Services, LLC can borrow up to $20.0 million to facilitate the financing of inventory of commodities and other products or goods approved by the lender in its sole discretion, subject to certain terms and conditions of the loan facility agreement. The loan facility is collateralized by a first priority security interest in goods and inventory of FCStone Merchant Services, LLC that is (a) either located outside of the U.S. and Canada or in transit to a destination outside the U.S. or Canada and (b) acquired with any extension of credit (whether in the form of a loan or by the issuance of a letter of credit) under the loan facility. The amounts borrowed under the facilities are payable on demand. Loans under the facility accrue interest at a per annum rate equal to the applicable Cost of Funds Rate, as defined, plus 3.00% or at the Base Rate, as defined, plus 2.00% . Letters of credit under the facility accrue a fee at the per annum rate of 2.75% . The interest rate associated with these borrowings was approximately 5.0% . There were $3.4 million and $3.8 million in borrowings outstanding under this credit facility as of September 30, 2019 , and September 30, 2018 , respectively. Note Payable to Bank In April 2015, the Company obtained a $4.0 million loan from a commercial bank, secured by equipment purchased with the proceeds. The note is payable in monthly installments, ending in March 2020. The note bears interest at a rate per annum equal to LIBOR plus 2.00% . Senior Unsecured Notes In July 2013, the Company completed an offering of $45.5 million aggregate principal amount of the Company’s 8.5% Senior Notes due 2020 (the “Notes”). The Company incurred debt issuance costs of $1.7 million in connection with the issuance of the Notes, which were being amortized over the term of the Notes. On October 15, 2016, the Company redeemed the Notes at a price equal to 100% of the principal amount redeemed plus accrued and unpaid interest to, but not including, October 15, 2016. The remaining unamortized deferred financing costs of $1.0 million were written off in connection with the redemption of the Notes and are included in ‘interest expense’ in the consolidated income statement for the year ended September 30, 2017. The following table sets forth a listing of credit facilities, the current committed amounts as of the report date on the facilities, and outstanding borrowings on the facilities as well as indebtedness on a promissory note as of the periods indicated: (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment September 30, September 30, Committed Credit Facilities Term Loan (1) February 22, 2022 $ 189.9 $ 167.6 (2) $ — Revolving Line of Credit (1) February 22, 2022 196.5 70.0 208.2 INTL FCStone Inc. 386.4 237.6 208.2 INTL FCStone Financial, Inc. None April 3, 2020 75.0 — — FCStone Merchants Services, LLC Certain commodities assets February 1, 2020 232.5 128.5 128.0 INTL FCStone Ltd. None January 31, 2020 50.0 — — $ 743.9 $ 366.1 $ 336.2 Uncommitted Credit Facilities INTL FCStone Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a — 14.0 INTL FCStone Ltd. Commodities warehouse receipts n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a 3.4 3.8 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 0.4 1.2 Total outstanding borrowings $ 369.9 $ 355.2 (1) The INTL FCStone Inc. committed credit facility is secured by substantially all of the assets of INTL FCStone Inc. and certain subsidiaries identified in the credit facility agreement as obligors, and pledged equity of certain subsidiaries identified in the credit facility as limited guarantors. (2) Amount outstanding under the Term Loan is reported net of unamortized deferred financing costs of $0.8 million . As reflected above, $357.5 million of the Company’s committed credit facilities are scheduled to expire during the fiscal year ended September 30, 2020. The Company intends to renew or replace these facilities as they expire, and based on the Company’s liquidity position and capital structure, the Company believes it will be able to do so.

Commitments and Contingencies (

Commitments and Contingencies (Notes)	12 Months Ended
	Sep. 30, 2019
Commitments and Contingencies [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Legal and Regulatory Proceedings Certain conditions may exist as of the date the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. In assessing loss contingencies related to legal and regulatory proceedings that are pending against the Company or unasserted claims that may result in such proceedings, the Company’s legal counsel evaluates the perceived merits of any legal or regulatory proceedings or unasserted claims as well as the perceived merits of the amount of relief sought or expected to be sought therein. If the assessment of a contingency indicates that it is probable that a material loss had been incurred at the date of the financial statements and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potentially material loss contingency is not probable, but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, together with an estimate of the range of possible loss if determinable and material, would be disclosed. Neither accrual nor disclosure is required for loss contingencies that are deemed remote. The Company accrues legal fees related to contingent liabilities as they are incurred. 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 limits of the respective policy. Additionally, the Company is subject to extensive regulation and supervision by U.S. federal and international governmental agencies and various self-regulatory organizations. The Company and its advisors periodically engage with such regulatory agencies and organizations, in the context of examinations or otherwise, to respond to inquiries, informational requests, and investigations. From time to time, such engagements result in regulatory complaints or other matters, the resolution of which can include fines and other remediation. As of September 30, 2019 and 2018 , the consolidated balance sheets include loss contingency accruals, recorded during and prior to these fiscal years 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, and in addition to the possible losses discussed below, is not material to the Company’s earnings, financial position or liquidity. The following is a summary of a significant legal matter involving the Company OptionSellers During the week ended November 16, 2018, balances in approximately 300 accounts of the FCM division of the Company’s wholly owned subsidiary, INTL FCStone Financial Inc., declined below required maintenance margin levels, primarily as a result of significant and unexpected price fluctuations in the natural gas markets. All positions in these accounts, which were managed by OptionSellers.com Inc. (“OptionSellers”), an independent Commodity Trading Advisor (“CTA”), were liquidated in accordance with the INTL FCStone Financial Inc.’s client agreements and obligations under market regulation standards. A CTA is registered with the U.S. Commodity Futures Trading Commission (“CFTC”) and a member of, and subject to audit by, the National Futures Association (“NFA”). OptionSellers is registered under a CFTC Rule 4.7 exemption for “qualified eligible persons,” which requires the account holders authorizing OptionSellers to act as their CTA to meet or exceed certain minimum financial requirements. OptionSellers, in its role as a CTA, had been granted by each of its clients full discretionary authority to manage the trading in the client accounts, while INTL FCStone Financial Inc. acted solely as the clearing firm in its role as the FCM. INTL FCStone Financial Inc.’s client agreements hold account holders liable for all losses in their accounts and obligate the account holders to reimburse INTL FCStone Financial Inc. for any account deficits in their accounts. As of September 30, 2019, the aggregate receivable from these client accounts, net of collections and other allowable deductions, was $29.2 million , with no individual account receivable exceeding $1.4 million . INTL FCStone Financial Inc. continues to pursue collection of these receivables and intends both to enforce and to defend its rights aggressively, and to claim interest and costs of collection where applicable. INTL FCStone Financial Inc. has been named in arbitrations brought by clients seeking damages relating to the trading losses in these accounts. The Company believes that such cases are without merit and intend to defend them vigorously. At the same time, the Company has initiated numerous arbitration proceedings against clients to recover deficit balances in their accounts. The Company believes it has a valid claim against its clients, based on the express language of the client contracts and legal precedent, and intends to pursue collection of these claims vigorously. The Company has done an assessment of the collectability of these accounts, considered the status of arbitration proceedings, and has concluded that it does not have a sufficient basis to record an allowance against these uncollected balances. As the Company moves through the collection and arbitration processes and additional information becomes available, the Company will continue to consider the need for an allowance against the carrying value of these uncollected balances. Depending on future collections and arbitration proceedings, any provisions for bad debts and actual losses ultimately may or may not be material to the Company’s financial results. Currently, the Company does not believe that any potential losses related to this matter would impact its ability to comply with its ongoing liquidity, capital, and regulatory requirements. Contractual Commitments Operating Leases The Company is obligated under various noncancelable operating leases for the rental of office facilities, automobiles, service obligations and certain office equipment, and accounts for these lease obligations on a straight line basis. The expense associated with operating leases was $14.1 million , $12.0 million and $11.3 million , for fiscal years ended September 30, 2019, 2018, and 2017 , respectively. The expenses associated with the operating leases and service obligations are reported in the consolidated income statements in ‘occupancy and equipment rental’. Future aggregate minimum lease payments under noncancelable operating leases as of September 30, 2019 are as follows: (in millions) Year ending September 30, 2020 $ 11.2 2021 9.9 2022 7.5 2023 6.2 2024 5.8 Thereafter 2.6 $ 43.2 Purchase Commitments The Company determines an estimate of contractual purchase commitments in the ordinary course of business primarily for the purchase of precious metals and agricultural and energy commodities. Unpriced contract commitments have been estimated using September 30, 2019 fair values. The purchase commitments and other obligations as of September 30, 2019 for less than one year, one to three years and three to five years were $2,893.1 million , $16.3 million and $18.0 million , respectively. There are no purchase commitments and other obligations after five years as of September 30, 2019 . The purchase commitments for less than one year will be offset by corresponding sales commitments of $2,633.9 million . Exchange Member Guarantees The Company is a member of various exchanges that trade and clear futures and option contracts. In connection with the Sterne acquisition, the Company is also a member of and provides guarantees to securities clearinghouses and exchanges in connection with client trading activities. Associated with its memberships, the Company may be required to pay a proportionate share of the financial obligations of another member who may default on its obligations to the exchanges. While the rules governing different exchange memberships vary, in general the Company’s guarantee obligations would arise only if the exchange had previously exhausted its resources. In addition, any such guarantee obligation would be apportioned among the other non-defaulting members of the exchange. Any potential contingent liability under these arrangements is not quantifiable and could exceed the cash and securities it has posted to the clearinghouse as collateral. The Company has not recorded any contingent liability in the consolidated financial statements for these agreements and believes that any potential requirement to make payments under these agreements is remote. 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. Liabilities are recognized based on claims filed and an estimate of claims incurred but not reported. The Company has purchased stop-loss coverage to limit its exposure on a per claim basis and in aggregate in the event that aggregated actual claims would exceed 120% of actuarially estimated claims. The Company is insured for covered costs in excess of these limits. Although the ultimate outcome of these matters may exceed the amounts recorded and additional losses may be incurred, the Company does not believe that any additional potential exposure for such liabilities will have a material adverse effect on the Company’s consolidated financial position or results of operations. As of September 30, 2019 and 2018 , the Company had $0.8 million accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the consolidated balance sheets.

Regulatory Requirements and Sub

Regulatory Requirements and Subsidiary Dividend Restrictions (Notes)	12 Months Ended
	Sep. 30, 2019
Capital and Other Regulatory Requirements [Abstract]
Regulatory Capital Requirements under Banking Regulations [Text Block]	The Company’s subsidiary INTL FCStone Financial is registered as a broker dealer and member of the Financial Industry Regulatory Authority (“FINRA”) subject to the SEC Uniform Net Capital Rule 15c3-1, which requires the maintenance of minimum net capital. INTL FCStone Financial is also a futures commission merchant registered with the CFTC and subject to the net capital requirements of the CFTC Regulation 1.17. Under the more restrictive of these rules, INTL FCStone Financial is required to maintain “adjusted net capital”, equivalent to the greater of $1,000,000 or 8 percent of client and non-client risk maintenance margin requirements on all positions, as defined in such rules, regulations, and requirements. Adjusted net capital and the related net capital requirement may fluctuate on a daily basis. INTL FCStone Financial also has a restriction on dividends, which restricts the withdrawal of equity capital if the planned withdrawal would reduce net capital, subsequent to haircuts and charges, to an amount less than 120% of the greatest minimum requirement. INTL FCStone Financial as a registered securities carrying broker dealer is also subject to Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), which requires the Company to maintain separate accounts for the benefit of securities clients and proprietary accounts of broker dealers (“PABs”). These client protection rules require the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. As of September 30, 2019 , INTL FCStone Financial prepared reserve computations for the client accounts and PAB accounts in accordance with the customer reserve computation guidelines set forth in Rule 15c3-3. Based upon these computations, the customer reserve requirement was $19.4 million as of September 30, 2019 . Additional deposits of $21.4 million were made to the customer SRBA in the week subsequent to September 30, 2019 to meet the customer segregation and segregated deposit timing requirements of Rule 15c3-3. The PAB reserve requirement was $2.6 million as of September 30, 2019 . Additional deposits of $3.6 million were made to the PAB SRBA in the week subsequent to September 30, 2019 to meet the PAB segregation and segregated deposit timing requirements of Rule 15c3-3. Pursuant to the requirements of the Commodity Exchange Act, funds deposited by clients of INTL FCStone Financial relating to their trading of futures and options on futures on a U.S. commodities exchange must be carried in separate accounts which are designated as segregated clients’ accounts. Pursuant to the requirements of the CFTC, funds deposited by clients of INTL FCStone Financial relating to their trading of futures and options on futures traded on, or subject to the rules of, a foreign board of trade must be carried in separate accounts in an amount sufficient to satisfy all of INTL FCStone Financial’s current obligations to clients trading foreign futures and foreign options on foreign commodity exchanges or boards of trade, which are designated as secured clients’ accounts. As of September 30, 2019 , INTL FCStone Financial had client segregated and client secured funds of $2,288.7 million and $173.5 million , respectively, compared to a minimum regulatory requirement of $2,232.1 million and $161.0 million , respectively. The Company’s subsidiary INTL FCStone Ltd is regulated by the Financial Conduct Authority (“FCA”), the regulator of the financial services industry in the U.K., as a Financial Services Firm under part IV of the Financial Services and Markets Act 2000. The regulations impose regulatory capital, as well as conduct of business, governance, and other requirements. The conduct of business rules include those that govern the treatment of client money and other assets which under certain circumstances for certain classes of client must be segregated from the firm’s own assets. As of September 30, 2019 , INTL FCStone Ltd had client segregated funds of $207.6 million compared to a minimum regulatory requirement of $196.9 million The following table details the Company’s subsidiaries with a minimum net capital requirement in excess of $5.0 million as well as the actual regulatory capital of the subsidiary as of September 30, 2019 (in millions): Subsidiary Regulatory Authority Actual Minimum Requirement INTL FCStone Financial Inc. SEC and CFTC $ 170.1 $ 97.5 INTL FCStone Ltd FCA $ 231.7 $ 123.3 Certain other subsidiaries of the Company, each with a minimum requirement less than $5.0 million, are also subject to net capital requirements promulgated by authorities in the countries in which they operate. As of September 30, 2019 , all of the Company’s subsidiaries were in compliance with their local regulatory requirements.

Commodity and Other Repurchase

Commodity and Other Repurchase Agreements (Notes)	12 Months Ended
	Sep. 30, 2019
Commodity and Other Repurchase Agreements [Abstract]
Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block]	The Company’s outstanding notes receivable in connection with repurchase agreements for agricultural and energy commodities, whereby the clients sell to the Company certain commodity inventory and agree to repurchase the commodity inventory at a future date at a fixed price were zero and $1.9 million as of September 30, 2019 and 2018, 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, fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, and to accommodate counterparties’ needs under matched-book trading strategies. 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 contractual agreements. The collateral is valued daily and the Company may require counterparties to deposit additional collateral or return collateral pledged. The Company pledges financial instruments owned to collateralize repurchase agreements. At September 30, 2019 and 2018, financial instruments owned, at fair value of $478.8 million and $123.0 million , respectively, 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 sheets. In addition, as of September 30, 2019 and 2018, the Company pledged financial instruments owned, at fair value of $1,228.9 million and $1,481.1 million , respectively, to cover collateral requirements for tri-party repurchase agreements. These securities have not been parenthetically disclosed on the consolidated balance sheets since the counterparties do not have the right to sell or repledge the collateral. The Company also repledged securities received under reverse repurchase agreements of $1,175.1 million and $369.8 million , respectively, to cover collateral requirements for tri-party repurchase agreements. The Company also has repledged securities borrowed and client securities held under custodial clearing arrangements to collateralize securities loaned agreements with a fair value of $1,414.0 million and $267.9 million as of September 30, 2019 and 2018, respectively. Additionally, the Company had also pledged financial instruments owned of zero and $27.1 million as of September 30, 2019 and 2018, respectively, to collateralize uncommitted loan facilities with certain banks as discussed further in Note 11 . At September 30, 2019 and 2018, the Company had 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 September 30, 2019 and 2018 was $3,060.2 million and $1,294.8 million , respectively, of which $329.8 million and $473.9 million , respectively, was used to cover securities sold short which are recorded in financial instruments sold, not yet purchased on the consolidated balance sheets. 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 and matched-book trading strategies. The following tables provide the contractual maturities of gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): September 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 1,553.9 $ 565.8 $ 654.0 $ 2,773.7 Securities loaned 1459.9 — — 1,459.9 Gross amount of secured financing $ 3,013.8 $ 565.8 $ 654.0 $ 4,233.6 September 30, 2018 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 934.9 $ 661.3 $ 340.5 $ 1,936.7 Securities loaned 277.9 — — 277.9 Gross amount of secured financing $ 1,212.8 $ 661.3 $ 340.5 $ 2,214.6 The following table provides the underlying collateral types of the gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): Securities sold under agreements to repurchase September 30, 2019 September 30, 2018 U.S. Treasury obligations $ 108.8 $ 39.6 U.S. government agency obligations 359.5 461.7 Asset-backed obligations 96.7 50.0 Agency mortgage-backed obligations 2,208.7 1,385.4 Total securities sold under agreement to repurchase $ 2,773.7 $ 1,936.7 Securities loaned Equity securities 1,459.9 277.9 Total securities loaned 1,459.9 277.9 Gross amount of secured financing $ 4,233.6 $ 2,214.6 The following tables provide the netting of securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed and securities loaned as of the periods indicated (in millions): September 30, 2019 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 1,474.4 $ (49.9 ) $ 1,424.5 Securities borrowed $ 1,423.2 $ — $ 1,423.2 Securities sold under agreements to repurchase $ 2,823.6 $ (49.9 ) $ 2,773.7 Securities loaned $ 1,459.9 $ — $ 1,459.9 September 30, 2018 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 870.8 $ — $ 870.8 Securities borrowed $ 225.5 $ — $ 225.5 Securities sold under agreements to repurchase $ 1,936.7 $ — $ 1,936.7 Securities loaned $ 277.9 $ — $ 277.9

Share-Based Compensation (Notes

Share-Based Compensation (Notes)	12 Months Ended
	Sep. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	Share-based compensation expense is included in ‘compensation and benefits’ in the consolidated income statements and totaled $8.1 million , $6.6 million and $6.3 million for the fiscal years ended September 30, 2019, 2018, and 2017 , respectively. Stock Option Plans The Company sponsors a stock option plan for its directors, officers, employees and consultants. The 2013 Stock Option Plan, which was approved by the Company’s Board of Directors and shareholders, authorizes the Company to issue stock options covering up to 2.0 million shares of the Company’s common stock. As of September 30, 2019 , there were 0.7 million shares authorized for future grant under this plan. Awards that expire or are canceled generally become available for issuance again under the plan. The Company settles stock option exercises with newly issued shares of common stock. Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions: Year ended September 30, 2019 2019 2018 2017 Expected stock price volatility 27 % 30 % 31 % Expected dividend yield — % — % — % Risk free interest rate 1.86 % 1.23 % 0.99 % Average expected life (in years) 6.05 3.06 3.08 Expected stock price volatility rates are primarily based on the historical volatility. The Company has not paid dividends in the past and does not currently expect to do so in the future. Risk free interest rates are based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option or award. The average expected life represents the estimated period of time that options or awards granted are expected to be outstanding, based on the Company’s historical share option exercise experience for similar option grants. The weighted average fair value of options issued during fiscal years ended September 30, 2019, 2018, and 2017 was $10.47 , $9.79 and $8.67 , respectively. The following is a summary of stock option activity for the year ended September 30, 2019 : Shares Available for Grant Number of Options Outstanding Weighted Average Exercise Price Weighted Average Grant Date Fair Value Weighted Average Remaining Term (in years) Aggregate Intrinsic Value ($ millions) Balances at September 30, 2018 588,020 835,454 $ 29.27 $ 11.93 3.01 $ 15.9 Additional shares authorized by shareholders 1,000,000 Granted (922,000 ) 922,000 $ 44.31 $ 10.47 Exercised (46,444 ) $ 25.04 $ 5.21 Forfeited 25,048 (25,048 ) $ 31.31 $ 11.91 Expired 1,584 (1,584 ) $ 33.83 $ 7.46 Balances at September 30, 2019 692,652 1,684,378 $ 37.59 $ 11.32 4.62 $ 9.2 Exercisable at September 30, 2019 472,424 $ 28.96 $ 12.27 2.08 $ 5.8 The total compensation cost not yet recognized for non-vested awards of $9.9 million as of September 30, 2019 has a weighted-average period of 5.61 years over which the compensation expense is expected to be recognized. The total intrinsic value of options exercised during fiscal years ended September 30, 2019, 2018, and 2017 was $0.7 million , $2.1 million and $2.6 million , respectively. The options outstanding as of September 30, 2019 broken down by exercise price are as follows: Exercise Price Number of Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Term $ — - $ 5.00 — n/a n/a $ 5.00 - $ 10.00 — n/a n/a $ 10.00 - $ 15.00 — n/a n/a $ 15.00 - $ 20.00 — n/a n/a $ 20.00 - $ 25.00 — n/a n/a $ 25.00 - $ 30.00 564,000 $ 25.91 2.37 $ 30.00 - $ 35.00 32,881 $ 31.37 0.28 $ 35.00 - $ 40.00 213,830 $ 39.33 2.43 $ 40.00 - $ 45.00 871,667 $ 44.91 6.78 $ 45.00 - $ 50.00 — n/a n/a $ 50.00 - $ 55.00 — n/a n/a $ 55.00 - $ 60.00 2,000 $ 55.28 2.89 1,684,378 $ 37.59 4.62 Restricted Stock Plan The Company sponsors a restricted stock plan for its directors, officers and employees. The Company’s 2017 restricted stock plan, which was approved by the Company’s Board of Directors and shareholders, authorizes up to 1.5 million shares to be issued. As of September 30, 2019 , 1.2 million shares were authorized for future grant under the restricted stock plan. Awards that expire or are canceled generally become available for issuance again under the plan. The Company utilizes newly issued shares of common stock to make restricted stock grants. The following is a summary of restricted stock activity through September 30, 2019 : Shares Available for Grant Number of Shares Outstanding Weighted Average Grant Date Fair Value Weighted Average Remaining Term (in years) Aggregate Intrinsic Value ($ millions) Balances at September 30, 2018 1,377,278 274,628 $ 38.20 1.15 $ 13.3 Granted (223,481 ) 223,481 $ 39.57 Vested — (144,226 ) $ 35.85 Forfeited 3,105 (3,105 ) $ 35.62 Balances at September 30, 2019 1,156,902 350,778 $ 40.06 1.36 $ 14.4 The total compensation cost not yet recognized of $10.0 million as of September 30, 2019 has a weighted-average period of 1.36 years over which the compensation expense is expected to be recognized. Compensation expense is amortized on a straight-line basis over the vesting period. Restricted stock grants are included in the Company’s total issued and outstanding common shares.

Retirement Plans (Notes)

Retirement Plans (Notes)	12 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefits Disclosure [Text Block]	Note 16 – Retirement Plans Defined Benefit Retirement Plans The Company has a frozen qualified defined benefit pension plan (the “Qualified Plan”) and a nonqualified defined benefit pension plan (the “Nonqualified Plan”), and recognizes their funded status, measured as the difference between the fair value of the plan assets and the projected benefit obligation, in “other assets” or “accounts payable and other accrued liabilities” in the consolidated balance sheets, depending on the funded status of each plan. The Qualified Plan assets, which are managed in a third-party trust, primarily consist of a diversified blend of approximately 80% debt securities and 20% equity investments and had a total fair value of $38.9 million and $35.6 million as of September 30, 2019 and 2018, respectively. All Qualified Plan assets fall within Level 2 of the fair value hierarchy. The benefit obligation associated with the Qualified Plan will vary over time only as a result of changes in market interest rates, the life expectancy of the plan participants, and benefit payments, since the accrual of benefits was suspended when the Qualified Plan was frozen in 2006. The benefit obligation was $36.5 million and $32.5 million and the discount rate assumption used in the measurement of this obligation was 3.10% and 4.20% as of September 30, 2019 and 2018, respectively. Related to the Qualified Plan, the Company’s net pension obligation was in a funded status of $2.4 million and $3.1 million as of September 30, 2019 and 2018, respectively. The Nonqualified Plan assets had a total fair value of less than $0.1 million as of September 30, 2019 and 2018. The benefit obligation associated with the Nonqualified Plan will vary over time only as a result of changes in market interest rates, the life expectancy of the plan participants, and benefit payments. There are no active participants in the Nonqualified plan. The benefit obligation was $1.7 million and $1.6 million as of September 30, 2019 and 2018, respectively. Related to the Nonqualified Plan, the Company’s unfunded pension obligation was $1.6 million as of September 30, 2019 and 2018. The Company recognized a net periodic benefit of $0.1 million , $0.2 million and $0.3 million for the year ended September 30, 2019, 2018 and 2017, respectively. The expected long-term return on plan assets assumption is 4.50% for 2019. The Company made contributions of $0.1 million and $1.0 million to the plans in the years ended September 30, 2019 and 2018, respectively. The Company complies with minimum funding requirements. The estimated undiscounted future benefit payments are expected to be $2.1 million in 2020, $2.1 million in 2021, $2.0 million in 2022, $2.0 million in 2023, $2.0 million in 2024 and $9.5 million in 2025 through 2029. Defined Contribution Retirement Plans The Company offers participation in the INTL FCStone Inc. 401(k) Plan (“401(k) Plan”), a defined contribution plan providing retirement benefits to all domestic full-time non-temporary employees who have reached 21 years of age. Employees may contribute from 1% to 80% of their annual compensation to the 401(k) Plan, limited to a maximum annual amount as set periodically by the Internal Revenue Service. The Company makes matching contributions to the 401(k) Plan in an amount equal to 62.5% of each participant’s eligible elective deferral contribution to the 401(k) Plan, up to 8% of employee compensation. Matching contributions vest, by participant, based on the following years of service schedule: less than two years – none, after two years – 33% , after three years – 66% , and after four years – 100% . U.K. based employees of INTL FCStone are eligible to participate in a defined contribution pension plan. The Company contributes double the employee’s contribution up to 10% of total base salary for this plan. For this plan, employees are 100% vested in both the employee and employer contributions at all times. For fiscal years ended September 30, 2019, 2018, and 2017 , the Company’s contribution to these defined contribution plans were $7.5 million , $6.8 million and $6.1 million , respectively.

Other Expenses (Notes)

Other Expenses (Notes)	12 Months Ended
	Sep. 30, 2019
Other Expenses [Abstract]
Other Expenses [Text Block]	Other expenses for the years ended September 30, 2019, 2018, and 2017 are comprised of the following: Year Ended September 30, (in millions) 2019 2018 2017 Insurance $ 3.4 $ 2.6 $ 2.7 Advertising, meetings and conferences 5.2 6.2 4.0 Office supplies and printing 1.9 1.7 2.1 Other clearing related expenses 2.5 2.5 2.6 Other non-income taxes 4.6 4.9 4.6 Contingent consideration, net — — 0.1 Other 10.8 8.4 9.8 Total other expenses $ 28.4 $ 26.3 $ 25.9

Bad Debt on Physical Coal Bad D

Bad Debt on Physical Coal Bad Debt on Physical Coal (Notes)	12 Months Ended
	Sep. 30, 2019
Bad Debt on Physical Coal [Abstract]
Unusual or Infrequent Items, or Both, Disclosure [Text Block]	– Bad Debt on Physical Coal During the year ended September 30, 2018 and 2017, the Company recorded charges to earnings of $1.0 million and $47.0 million , respectively, to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business, conducted solely in the Company’s Singapore subsidiary, INTL Asia Pte. Ltd., with a coal supplier. Components of the bad debt on physical coal included allowances on amounts due to the Company from the supplier related to: coal paid for but not delivered to clients; reimbursement of demurrage claims, dead freight and other charges paid by INTL Asia Pte. Ltd. to its clients; reimbursement due for deficiencies in the quality of coal delivered to clients; and losses incurred related to the cancellation of open sales contracts. During fiscal 2017, the Company purchased coal delivered onto barges and paid 80% of the value against bills of lading and purchase invoices, with the remaining 20% payable following inspection upon delivery to clients’ vessels. The Company took title of the coal when it was loaded onto barges and maintained title until it was offloaded onto clients’ vessels. The logistics related to the delivery of coal to the clients’ vessels was out-sourced to the Company’s coal supplier, and the Company determined that certain purchased coal was not delivered to the clients’ vessels during the fourth quarter ended September 30, 2017. Furthermore, the Company determined that the supplier was unable to deliver such purchased coal to its clients. Demurrage claims, dead freight, and other penalty charges paid and payable by INTL Asia Pte. Ltd. to its clients were due to be reimbursed by the supplier based on transaction agreements with the supplier. The Company determined the supplier was unable to make this reimbursement. During the year ended September 30, 2018, the Company completed its exit of the physical coal business, which was part of our Physical Commodities segment. During the year ended September 30, 2019, the Company reached settlements with clients, paying $8.4 million related to demurrage, dead freight, and other penalty charges regarding coal supplied during fiscal 2018 and fiscal 2017. The settlement amounts paid were less than the accrued liability for the transactions recorded during fiscal 2018 and fiscal 2017, and accordingly the Company recorded a recovery on the bad debt on physical coal of $2.4 million . During the year ended September 30, 2019, the Company also received $10.0 million through an insurance policy claim related to the physical coal matter, and recorded the insurance proceeds as an additional recovery. The Company has presented the bad debt on physical coal and subsequent recoveries separately as a component of income before tax in the consolidated income statements.

Income Taxes (Notes)

Income Taxes (Notes)	12 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	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 lowered the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. The Company computed its income tax expense for the year ending September 30, 2019 using a U.S. statutory tax rate of 21% . The Company computed income tax expense for the year ended September 30, 2018 using a U.S. statutory tax rate of 24.5% . The Tax Reform imposed a mandatory repatriation transition tax on previously untaxed accumulated and current earnings and profits (“E&P”) of certain foreign subsidiaries for the year ended September 30, 2018. The Tax Reform also established new tax laws that affected the 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 incurred in tax years beginning after September 30, 2018 to 80% 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 interest expense and certain executive compensation. The Company made the policy election to treat GILTI as a current period expense when incurred. The estimated impact of GILTI is included in the effective tax rate and increases the effective income tax rate by approximately 2.2% for the year ended September 30, 2019. 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 provisional measurement period that should not extend beyond one year from the Tax Reform enactment date for companies to complete the accounting under ASC 740, Income Taxes. The Company’s income tax accounting provisional measurement period for the Tax Reform concluded during the three months ended December 31, 2018 with no adjustments to the provisional amounts recorded during the year ended September 30, 2018. For the year ended September 30, 2018, the Company recorded income tax expense of $8.6 million related to the remeasurement of deferred tax assets and liabilities, which increased the effective tax rate by 8.5% . The Tax Reform also included a mandatory repatriation transition tax on previously untaxed accumulated and current E&P of certain of the Company’s foreign subsidiaries. To determine the amount of the transition tax, the Company determined, in addition to other factors, the amount of post 1986 E&P of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. The Company recorded a transition tax obligation of $11.2 million during the year ended September 30, 2018, which increased the effective tax rate by 11% during the year ended September 30, 2018. Income tax expense (benefit) for the years ended September 30, 2019, 2018, and 2017 was allocated as follows: Year Ended September 30, (in millions) 2019 2018 2017 Income tax expense attributable to income from operations $ 25.9 $ 46.0 $ 8.8 Taxes allocated to stockholders’ equity, related to pension liabilities (0.2 ) 0.1 1.0 Taxes allocated to additional paid-in capital, related to share-based compensation — — 0.1 Total income tax expense $ 25.7 $ 46.1 $ 9.9 The components of income tax expense (benefit) attributable to income from operations were as follows: Year Ended September 30, (in millions) 2019 2018 2017 Current taxes: U.S. federal $ (1.9 ) $ 0.8 $ 0.7 U.S. State and local (0.8 ) 0.5 1.2 International 24.9 22.4 16.7 Total current taxes 22.2 23.7 18.6 Deferred taxes 3.7 22.3 (9.8 ) Income tax expense $ 25.9 $ 46.0 $ 8.8 U.S. and international components of (loss) income from operations, before tax, was as follows: Year Ended September 30, (in millions) 2019 2018 2017 U.S. $ (2.6 ) $ 9.9 $ (13.9 ) International 113.6 91.6 29.1 Income from operations, before tax $ 111.0 $ 101.5 $ 15.2 Items accounting for the difference between income taxes computed at the federal statutory rate and income tax expense were as follows: Year Ended September 30, 2019 2018 2017 Federal statutory rate effect of: 21.0 % 24.5 % 35.0 % U.S. State and local income taxes (1.5 )% 0.8 % (2.6 )% Foreign earnings and losses taxed at different rates 0.7 % (0.8 )% 11.5 % Change in foreign valuation allowance 1.0 % (0.8 )% (1.4 )% Change in state valuation allowance 0.5 % — % 4.1 % U.S. permanent items 0.1 % (0.2 )% 3.6 % Foreign permanent items 0.7 % 2.1 % 8.1 % U.S. bargain purchase gain (1.0 )% — % — % Remeasurement of deferred tax — % 8.5 % — % Repatriation Transition tax — % 11.0 % — % GILTI 2.2 % — % — % Other reconciling items (0.4 )% 0.2 % (0.6 )% Effective rate 23.3 % 45.3 % 57.7 % The components of deferred income tax assets and liabilities were as follows: (in millions) September 30, 2019 September 30, 2018 Deferred tax assets: Share-based compensation $ 3.3 $ 2.8 Deferred compensation 3.6 1.4 Foreign net operating loss carryforwards 2.6 4.2 U.S. State and local net operating loss carryforwards 9.2 8.7 U.S. federal net operating loss carryforwards 1.1 — Intangible assets 4.8 1.8 Bad debt reserve 1.3 1.5 Tax credit carryforwards 0.5 — Foreign tax credit carryforwards 5.0 6.5 Other compensation 2.2 3.4 Other 1.1 0.9 Total gross deferred tax assets 34.7 31.2 Less valuation allowance (8.5 ) (3.5 ) Deferred tax assets 26.2 27.7 Deferred income tax liabilities: Unrealized gain on securities 3.2 2.6 Prepaid expenses 2.2 1.8 Property and equipment 2.6 3.1 Pension liability 0.2 0.4 Deferred income tax liabilities 8.2 7.9 Deferred income taxes, net $ 18.0 $ 19.8 Deferred income tax balances reflect the effects of temporary differences between the carrying amounts of assets and liabilities and their tax bases and are stated at enacted tax rates expected to be in effect when taxes are actually paid or recovered. As of September 30, 2019 and 2018 , the Company has net operating loss carryforwards for U.S. federal, state, local, and foreign income tax purposes of $7.1 million and $9.4 million , net of valuation allowances, respectively, which are available to offset future taxable income in these jurisdictions. During the year ended September 30, 2018, the Company utilized $21.9 million of U.S. federal net operating losses against the mandatory repatriation transition tax. The state and local net operating loss carryforwards of $5.6 million , net of valuation allowance, begin to expire after September 2020. The Company also has $0.6 million , net of valuation allowances, of federal net operating loss carryforwards due to the acquisition of GMP Securities LLC, as discussed in Note 20. These federal net operating loss carryforwards consist of a portion that will expire in tax years ending 2032 through 2037. The remaining portion of the federal net operating loss carryforwards do not expire, but cannot be utilized until after 2038 and are limited by Internal Revenue Code (“IRC”) Section 382. As of September 30, 2019 and 2018 , INTL Asia Pte. Ltd. has a net operating loss carryforward of $0.2 million and $2.9 million , respectively. This Singapore net operating loss has an indefinite carryforward and, in the judgment of management, is more likely than not to be realized. As a result of Tax Reform, the AMT credit carryforward deferred tax asset was reclassified to income taxes receivable during the year ended September 30, 2018. The Company can continue to utilize AMT credits to offset regular income tax liability in fiscal years 2020 through 2021. Any remaining amount is fully refundable by fiscal year 2022. During the year ended September 30, 2018, the Company generated $5.1 million in foreign tax credit carryforwards as part of the mandatory repatriation transition tax. These credits expire in fiscal year 2028. In the judgment of management, the Company believes that sufficient taxable income will be earned to utilize the foreign tax credit carryforwards within 10 years. The valuation allowance for deferred tax assets as of September 30, 2019 was $8.5 million . The net change in the total valuation allowance for the year ended September 30, 2019 was an increase of $5.0 million . Of this amount, $3.3 million is related to federal net operating losses and net unrealized built-in losses acquired through the GMP Securities, LLC acquisition, which are limited by the provisions of IRC Section 382, as further discussed in Note 20 . The remaining increase is related to foreign and state net operating loss carryforwards. The valuation allowances as of September 30, 2019 and 2018 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. The total amount of undistributed earnings in the Company’s foreign subsidiaries, for income tax purposes, was $383.5 million and $354.7 million as of September 30, 2019 and 2018 , respectively. The Company recognized the mandatory repatriation tax related to these undistributed earnings as part of Tax Reform during the year ended September 30, 2018 and, as a result, repatriation of these amounts would not be subject to additional U.S. federal income tax but may be subject to applicable withholding and state taxes in the relevant jurisdictions. T he Company does not intend to distribute earnings in a taxable manner, and therefore intends to limit distributions to earnings previously taxed in the U.S., or earnings that would qualify for the 100 percent dividends received deduction provided for in the Tax Reform, and earnings that would not result in any significant foreign taxes. During the year ended September 30, 2019, the Company repatriated $13.0 million of earnings previously taxed in the U.S. resulting in no significant incremental taxes upon repatriation. Therefore, the Company has not recognized a deferred tax liability on its investment in foreign subsidiaries. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Year Ended September 30, (in millions) 2019 2018 2017 Balance, beginning of year $ 0.1 $ 0.1 $ 0.1 Gross decreases for tax positions of prior years (0.1 ) — — Balance, end of year $ — $ 0.1 $ 0.1 The Company has a minimal balance of unrecognized tax benefits as of September 30, 2019 , that, if recognized, would affect the effective tax rate. Accrued interest and penalties are included in the related tax liability line in the consolidated balance sheets. The Company had no accrued interest and penalties included in the consolidated balance sheets as of September 30, 2019 and 2018 . The Company recognizes accrued interest and penalties related to income taxes as a component of income tax expense. The Company had no amount of interest, net of federal benefit, and penalties recognized as a component of income tax expense during the years ended September 30, 2019, 2018, and 2017 . The Company and its subsidiaries file income tax returns with the U.S. federal jurisdiction and various U.S. state and local and foreign jurisdictions. The Company has open tax years ranging from September 30, 2012 through September 30, 2019 with U.S. federal and state and local taxing authorities. In the U.K., the Company has open tax years ending September 30, 2017 to September 30, 2019. In Brazil, the Company has open tax years ranging from December 31, 2014 through December 31, 2018. In Argentina, the Company has open tax years ranging from September 30, 2012 to September 30, 2019. In Singapore, the Company has open tax years ranging from September 30, 2015 to September 30, 2019.

Acquisitions (Notes)

Acquisitions (Notes)	12 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	The Company’s consolidated financial statements include the operating results of the acquired businesses from the dates of acquisition. Acquisitions in Fiscal 2019 Carl Kliem S.A. On November 30, 2018, the Company acquired the entire issued and outstanding share capital of Carl Kliem S.A., an independent interdealer broker based in Luxembourg, which provides foreign exchange, interest rate and fixed income products to institutional clients across the European Union (“E.U.”). Carl Kliem S.A. employs approximately 40 people and has more than 400 active institutional clients. This acquisition provides the Company with access to additional European institutional clients that can benefit from the Company’s full suite of financial services and a E.U.-based entity in anticipation of the U.K.’s planned exit from the E.U. The purchase price was $2.1 million of cash consideration, and was equal to the net tangible book value on the closing date less restructuring costs. The Company subsequently renamed Carl Kliem S.A. to INTL FCStone Europe S.A. The final purchase price allocation resulted in cash and cash equivalents of $1.7 million , receivables from clients of $1.1 million , property and equipment of $0.1 million , income tax receivables of $0.1 million , accounts payable and other accrued liabilities of $0.6 million , and payable to broker-dealers, clearing organizations, and counterparties of $0.2 million . The net fair value of the assets acquired exceeded the aggregate cash purchase price; accordingly, the Company recorded a bargain purchase gain of $0.1 million during the year ended September 30, 2019 , which is presented within ‘other gains’ in the consolidated income statement. The business activities of INTL FCStone Europe S.A. have been included within the Company’s Securities and Clearing and Execution Services reportable segments. The Company’s consolidated income statement for the year ended September 30, 2019 includes operating revenues and a net loss of $4.2 million and $2.3 million , respectively, for the post-acquisition results of the acquired business. GMP Securities LLC On January 14, 2019 the Company acquired 100% of the U.S.-based broker-dealer GMP Securities LLC (“GMP”), formerly known as Miller Tabak Securities, LLC, an independent, SEC-registered broker-dealer and Financial Industry Regulatory Authority, Inc. (“FINRA”) member. GMP has an institutional fixed-income trading business which deals in high yield, convertible and emerging market debt and makes markets in certain equity securities. This transaction also involved the purchase of GMP’s U.S.-based parent. This acquisition allows the Company to expand its fixed income product offerings to clients and adds new institutional clients who can benefit from the Company’s full suite of financial services. The purchase price was $8.2 million of cash consideration was equal to the final net tangible book value determined as of the acquisition date less $2.0 million . The net fair value of the assets acquired exceeded the aggregate cash purchase price, and accordingly the Company recorded a bargain purchase gain of $5.4 million during the year ended September 30, 2019 , which is presented within ‘other gains’ in the consolidated income statement. The Company believes the transaction resulted in a bargain purchase gain due to the Company’s ability to incorporate GMP’s business activities into its existing business structure, and its ability to utilize certain deferred tax assets, including net operating loss carryforwards, and other assets while operating the business that may not have been likely to be realized by the seller nor was contemplated in the purchase price. On May 1, 2019, GMP was merged into the Company’s wholly owned regulated U.S. subsidiary, INTL FCStone Financial. The Company’s consolidated income statement includes the post-acquisition results, which include operating revenues and a net loss before tax of $8.2 million and $2.1 million , respectively, for the year ended September 30, 2019 . The acquired businesses are included within the Company’s Securities reportable segment. The following represents the final allocation of the purchase price to the fair value of identifiable assets acquired and liabilities assumed as of the acquisition date: (in millions) Fair Value Cash and cash equivalents $ 1.1 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties (1) 7.7 Financial instruments owned, at fair value (2) 7.1 Deferred income taxes 2.7 Property and equipment 0.7 Other assets 0.7 Total fair value of assets acquired 20.0 Accounts payable and other accrued liabilities 1.9 Payable to broker-dealers, clearing organizations, and counterparties 0.1 Financial instruments sold, not yet purchased, at fair value (2) 4.4 Total fair value of liabilities assumed 6.4 Fair value of net assets acquired 13.6 Purchase price 8.2 Bargain purchase gain $ 5.4 (1) Amount represents the contractual amount of deposits and receivables due from the clearing organization for trading activity as of the acquisition date. (2) Financial instruments owned and sold, not yet purchased, at fair value primarily includes equity securities and high yield, convertible and emerging market fixed income securities. Equity securities have been included within Level 1 of the fair value hierarchy and fixed income securities have been included in Level 2 of the fair value hierarchy as disclosed in Note 4 . CoinInvest GmbH and European Precious Metal Trading GmbH On April 1, 2019, the Company’s subsidiary INTL FCStone (Netherlands) B.V. acquired 100% of the outstanding shares of CoinInvest GmbH and European Precious Metal Trading GmbH. Through the websites coininvest.com and silver-to-go.com, CoinInvest GmbH and European Precious Metal Trading GmbH are leading European online providers of gold, silver, platinum, and palladium products to retail investors, institutional investors, and financial advisors. The addition of CoinInvest GmbH and European Precious Metal Trading GmbH to the Company’s global product suite expands its offering, providing clients the ability to purchase physical gold and other precious metals, in multiple forms, and in denominations of their choice, to add to their investment portfolios. The purchase price consisted of cash consideration of $22.0 million , including $11.2 million for the purchase of shareholders loans outstanding with the acquired entities. The cash consideration transferred exceeded the preliminary fair value of the tangible net assets acquired on the closing date by $6.8 million . The Company acquired certain identifiable intangible assets, including website domain names and internally developed software. The Company has engaged a third-party valuation specialist to assist with the valuation of these acquired intangible assets. Based upon the preliminary valuation analysis, the Company has allocated $2.1 million and $2.5 million of the excess consideration over the preliminary fair value of tangible net assets acquired on the closing date to the identifiable domain names and internally developed software, respectively. The remaining excess of $2.2 million was allocated to goodwill. The goodwill represents the synergies expected to be achieved by combining the acquired business with the Company’s existing precious metals offering and the acquired assembled workforce. The internally developed software was assigned to the Physical Commodities reportable segment and will be amortized over a useful life of 5 years. The useful life of the domain names was determined to be indefinite. The Company’s consolidated income statement includes the post-acquisition results, including operating revenues and a net loss before tax of $0.6 million and $0.3 million , respectively, for the year ended September 30, 2019 . Operating revenues during the year ended September 30, 2019 include unrealized losses on derivatives held to manage the downside price risk of physical commodities inventory, which is valued at the lower of cost or net realizable value; therefore, inventory was not recorded above its cost basis. The acquired businesses are included within the Company’s Physical Commodities reportable segment. The following represents a preliminary allocation of the purchase price to the fair value of identifiable assets acquired and liabilities assumed as of the acquisition date: (in millions) Fair Value Cash and cash equivalents $ 2.0 Receivables from clients (1) 1.2 Receivable from affiliate 1.1 Income tax receivable 0.1 Physical commodities inventory 9.8 Deferred tax assets, net 0.2 Other assets 1.2 Total fair value of tangible assets acquired 15.6 Accounts payable and other accrued liabilities 0.2 Payables to clients 0.2 Total fair value of tangible liabilities assumed 0.4 Fair value of net tangible assets acquired 15.2 Purchase price 22.0 Excess purchase price over fair value of tangible net assets acquired $ 6.8 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Domain names $ 2.1 Internally developed software 2.5 Total excess purchase price allocated to identifiable intangible assets 4.6 Remaining excess allocated to goodwill $ 2.2 (1) Amount represents the contractual amount of receivables due from clients for trading activity, all of which the Company expects to be collectible as of the closing date. Fillmore Advisors, LLC On September 1, 2019, the Company acquired 100% of the U.S.-based trading firm Fillmore Advisors, LLC (“Fillmore”). Fillmore is an independent, SEC-registered broker-dealer firm and FINRA member firm and a leading provider of outsourced trading solutions and operational consulting to institutional asset managers. The firm, headquartered in Park City, Utah, is composed of traders that specialize in global buy-side and sell-side experience. Institutional clients can benefit from Fillmore’s comprehensive product coverage offering for equities, equity-linked, foreign exchange, credit, rates, and commodities. Fillmore will become an extension of the newly established prime brokerage division of the Company’s Securities reportable segment. The purchase price consists of $1.4 million of cash consideration and also includes a contingent earn-out with payments over the eight quarters following the acquisition. The contingent earn-out payments are variable in nature and equal to 50% of Segment Income, as defined in the SPA, for each quarterly period. The fair value of the contingent consideration was estimated at $1.8 million as of the closing date. See Note 4 for fair value measurement considerations. The Company acquired certain identifiable intangible assets related to Fillmore’s client base. Based upon the preliminary valuation analysis, the Company has allocated $0.7 million of the excess consideration over the preliminary fair value of tangible net assets acquired on the closing date to this intangible asset. The remaining excess of $1.9 million was allocated to goodwill. The goodwill represents the synergies expected to be achieved by combining the acquired business with the Company’s existing prime brokerage offering and the acquired assembled workforce. The client base intangible asset and goodwill were assigned to the Securities reportable segment. The client base intangible asset will be amortized over a useful life of 5 years. The following represents a preliminary allocation of the purchase price to the fair value of identifiable assets acquired and liabilities assumed as of the acquisition date: (in millions) Fair Value Cash and cash equivalents $ 0.2 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties 0.3 Receivables from clients, net (1) 0.2 Other assets 0.4 Total fair value of tangible assets acquired 1.1 Accounts payable and other accrued liabilities 0.5 Total fair value of tangible liabilities assumed 0.5 Fair value of net tangible assets acquired 0.6 Purchase price (2) 3.2 Excess purchase price over fair value of tangible net assets acquired $ 2.6 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Client relationships $ 0.7 Total excess purchase price allocated to identifiable intangible assets 0.7 Remaining excess allocated to goodwill $ 1.9 (1) Amount represents the contractual amount of receivables due from clients for trading activity, all of which the Company expects to be collectible as of the closing date. (2) Includes the fair value of contingent consideration of $1.8 million . Subsequent Acquisition UOB Bullion and Futures Limited On March 19, 2019, the Company’s subsidiary INTL FCStone Pte Ltd executed an asset purchase agreement to acquire the futures and options brokerage and clearing business of UOB Bullion and Futures Limited, a subsidiary of United Overseas Bank Limited. Closing was conditional upon receiving regulatory approval by the Monetary Authority of Singapore (“MAS”). This acquisition provides the Company access to an established institutional client base and also augments the Company’s global service capabilities in Singapore. The purchase price for the acquired assets is $5.0 million of which $2.5 million was due upon the execution of the asset purchase agreement and is included in ‘other assets’ on the consolidated balance sheet as of September 30, 2019 . The remaining $2.5 million was paid to the seller at closing of the acquisition, which occurred on October 7, 2019. The Company will account for this transaction as the acquisition of a business. The initial purchase price allocation for this acquisition is not yet complete. Acquisitions in Fiscal 2018 PayCommerce Financial Solutions, LLC On September 5, 2018, the Company acquired all of the outstanding membership interests of PayCommerce Financial Solutions, LLC (“PCFS”). Subsequent to the acquisition, the Company renamed PCFS to INTL Technology Services, LLC (“ITS”). ITS is a fully accredited Society for Worldwide Interbank Financial Telecommunication (“SWIFT”) Service Bureau provider. This acquisition enables the Company to act as a SWIFT Service Bureau for its 300-plus correspondent banking network, thus providing another important service for delivering local currency, cross-border payments to the developing world. The purchase price was approximately $3.8 million of cash consideration. The initial purchase price allocation resulted in $0.7 million in receivables, $0.8 million in property, plant, and equipment, a $0.5 million equity investment related to a minority interest in the joint venture entity Akshay Financeware, Inc., and $2.2 million in liabilities assumed. Additionally, the Company acquired identifiable, definite-lived client relationship and client list assets that have been assigned a fair value of $1.3 million and a useful life of 5 years. The fair value of the consideration transferred exceeded the initial fair value of identifiable assets acquired and liabilities assumed. The excess of the purchase consideration over the initial fair value of net tangible and identifiable intangible assets acquired of $2.6 million was recorded as goodwill as of September 30, 2018. On February 13, 2019, the Company paid $0.2 million to acquire the majority interest in Akshay Financeware, Inc. The acquisition of the majority interest in Akshay Financeware, Inc. was accounted for as a step acquisition. As a result, the Company changed the classification and measurement of the $0.5 million previously held equity interest and recognized all identifiable assets and liabilities of the wholly-owned entity at fair value. The Company recorded $2.7 million of indefinite-lived intangible assets related to SWIFT licenses held by the acquired entity and an associated deferred tax liability of $0.7 million . Additionally, the Company recorded a measurement period adjustment to goodwill of $1.3 million . As of September 30, 2019, the Company had recorded goodwill of $1.3 million related to the acquisition of PCFS and the step acquisition of Akshay Financeware, Inc. Management believes that the goodwill represents the synergies expected from the incremental revenue that can be realized from combining the technologies acquired with the Company’s pre-existing correspondent banking network. This business has been included within the Company’s Global Payments Segment. The Company’s consolidated income statement for the year ended September 30, 2018 includes the post-acquisition results of ITS, which was immaterial in relation to the Company’s consolidated results. Acquisition in Fiscal 2017 ICAP’s EMEA Oils Broking Business Effective October 1, 2016, the Company’s subsidiary, INTL FCStone Ltd acquired the London-based EMEA oils voice brokerage business of ICAP Plc. The business provides brokerage services across the fuel, crude, and middle distillates markets to commercial and institutional clients throughout EMEA. The terms of the agreement included cash consideration of $6.0 million paid directly to ICAP as well as incentive amounts payable to employees acquired based upon their continued employment. The cash consideration paid to ICAP was dependent upon the number of brokers who accepted INTL FCStone Ltd.’s employment offer. The transaction was accounted for as an asset acquisition in accordance with FASB ASC 805-50 and FASB ASC 350. The cash consideration paid was allocated entirely to the intangible asset recognized related to the client base acquired. The intangible asset was assigned to the Clearing and Execution Services segment and is being amortized over a useful life of 5 years.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) (Notes)	12 Months Ended
	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Abstract]
Comprehensive Income (Loss) Note [Text Block]	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) income includes net actuarial gains from defined benefit pension plans and losses on foreign currency translations. The following table summarizes the changes in accumulated other comprehensive (loss) income for the year ended September 30, 2019 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2018 $ (30.5 ) $ (2.6 ) $ (33.1 ) Other comprehensive (loss) income, net of tax before reclassifications (0.8 ) (0.8 ) (1.6 ) Amounts reclassified from AOCI, net of tax (0.2 ) 0.1 (0.1 ) Other comprehensive (loss) income, net of tax (1.0 ) (0.7 ) (1.7 ) Balances as of September 30, 2019 $ (31.5 ) $ (3.3 ) $ (34.8 )

Quarterly Financial Information

Quarterly Financial Information (Unaudited) (Notes)	12 Months Ended
	Sep. 30, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	The Company has set forth certain quarterly unaudited financial data for the past two years in the tables below: For the 2019 Fiscal Quarter Ended (in millions, except per share amounts) September 30 (1) June 30 March 31 December 31 Total revenues $ 11,279.6 $ 7,873.0 $ 7,192.2 $ 6,552.2 Cost of sales of physical commodities 10,992.7 7,589.6 6,921.1 6,287.5 Operating revenues 286.9 283.4 271.1 264.7 Transaction-based clearing expenses 45.0 45.7 42.7 50.1 Introducing broker commissions 27.7 29.6 24.8 32.6 Interest expense 40.8 42.5 38.4 33.0 Net operating revenues 173.4 165.6 165.2 149.0 Compensation and benefits 105.2 100.9 97.9 89.1 Bad debts 1.0 0.5 0.7 0.3 Bad debt on physical coal (1) (10.0 ) — — (2.4 ) Other expenses 43.2 42.6 41.1 37.6 Total compensation and other expenses 139.4 144.0 139.7 124.6 Other gains (2) 0.1 — 5.4 — Income before tax 34.1 21.6 30.9 24.4 Income tax expense 6.9 5.3 7.5 6.2 Net income $ 27.2 $ 16.3 $ 23.4 $ 18.2 Net basic earnings per share $ 1.42 $ 0.85 $ 1.23 $ 0.96 Net diluted earnings per share $ 1.40 $ 0.84 $ 1.21 $ 0.94 For the 2018 Fiscal Quarter Ended (in millions, except per share amounts) September 30, June 30, March 31, December 31, Total revenues $ 6,078.8 $ 7,118.3 $ 6,507.0 $ 7,918.6 Cost of sales of physical commodities 5,835.6 6,858.5 6,246.8 7,706.0 Operating revenues 243.2 259.8 260.2 212.6 Transaction-based clearing expenses 43.1 49.0 50.7 36.9 Introducing broker commissions 32.4 34.1 36.2 31.1 Interest expense 25.3 22.1 19.0 14.3 Net operating revenues 142.4 154.6 154.3 130.3 Compensation and benefits 85.4 86.9 88.2 77.2 Bad debts 1.2 1.6 0.2 0.1 Bad debt on physical coal (1) — — — 1.0 Other expenses 35.3 35.2 36.4 33.4 Total compensation and other expenses 121.9 123.7 124.8 111.7 Other gains (2) — 2.0 — — Income before tax 20.5 32.9 29.5 18.6 Income tax expense 4.8 8.9 6.8 25.5 Net income (loss) $ 15.7 $ 24.0 $ 22.7 $ (6.9 ) Net basic (loss) earnings per share $ 0.83 $ 1.27 $ 1.20 $ (0.37 ) Net diluted (loss) earnings per share $ 0.81 $ 1.25 $ 1.18 $ (0.37 ) (1) During the fourth quarter ended September 30, 2019, the Company recorded a recovery on the bad debt on physical coal received through an insurance policy claim related to the matter. During the first quarter ended December 31, 2018, the Company recorded recoveries on the bad debt on physical coal realized through settlements with clients, paying less than the accrued liability for the transactions recorded during fiscal 2017 and fiscal 2018. During the first quarter of fiscal 2018, the Company recorded charges to earnings of $1.0 million to record an allowance for doubtful accounts related to the bad debt on physical coal. See Note 18 for additional information. (2) During the second quarter ended March 31, 2019, the Company recorded a bargain purchase gain of $5.4 million related to the acquisition of INTL FCStone Credit Trading, LLC (formerly GMP Securities LLC). During the third quarter ended June 30, 2018, the Company recorded a gain of $2.0 million related to a judgment received in final settlement of our claim in the Sentinel Management Group Inc. bankruptcy proceeding.

Segment and Geographic Informat

Segment and Geographic Information (Notes)	12 Months Ended
	Sep. 30, 2019
Segment Analysis [Abstract]
Segment Reporting Disclosure [Text Block]	The Company reports its operating segments based on services provided to clients. 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 Capital Markets, Debt Capital Markets 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) Commercial Hedging The Company serves its commercial clients through its team of risk management consultants, providing a high-value-added service that it believes differentiates the Company from its competitors and maximizes the opportunity to retain clients. The Company’s risk management consulting services are designed to quantify and monitor commercial entities’ exposure to commodity and financial risk. Upon assessing this exposure, the Company develops a plan to control and hedge these risks with post-trade reporting against specific client objectives. Clients are assisted in the execution of their hedging strategies through a wide range of products from listed exchange-traded futures and options, to basic OTC instruments that offer greater flexibility, to structured OTC products designed for customized solutions. The Company’s services span virtually all traded commodity markets, with the largest concentrations in agricultural and energy commodities (consisting primarily of grains, energy and renewable fuels, coffee, sugar, cotton, and food service) and base metals products listed on the LME. The Company’s base metals business includes a position as a Category One ring dealing member of the LME, providing execution, clearing and advisory services in exchange-traded futures and OTC products. The Company also provides execution of foreign currency forwards and options and interest rate swaps as well as a wide range of structured product solutions to commercial clients who are seeking cost-effective hedging strategies. Generally, clients direct their own trading activity and the Company’s risk management consultants do not have discretionary authority to transact trades on behalf of clients. Global Payments The Company provides customized foreign exchange and treasury services to banks and commercial businesses as well as charities and non-governmental organizations and government organizations. The Company provides transparent pricing and offers payments services in more than 170 countries and 140 currencies, which it believes is more than any other payments solution provider. Its proprietary FXecute global payments platform is integrated with a financial information exchange (“FIX”) protocol. This FIX protocol is an electronic communication method for the real-time exchange of information, and the Company believes it represents one of the first FIX offerings for cross-border payments in exotic currencies. FIX functionality allows clients to view real time market rates for various currencies, execute and manage orders in real-time, and view the status of their payments through the easy-to-use portal. Additionally, as a member of SWIFT, the Company is able to offer its services to large money center and global banks seeking more competitive international payments services. In addition, the Company operates a fully accredited SWIFT Service Bureau which facilitates cross-border payments and acceptance transactions for financial institutions, trade networks and corporations. Through this single comprehensive platform and our commitment to client service, the Company believes it is able to provide simple and fast execution, ensuring delivery of funds in local currency to any of these countries quickly through its global network of approximately 325 correspondent banks. In this business, the Company primarily acts as a principal in buying and selling foreign currencies on a spot basis. The Company derives revenue from the difference between the purchase and sale prices. The Company believes its clients value its ability to provide exchange rates that are significantly more competitive than those offered by large international banks, a competitive advantage that stems from its years of foreign exchange expertise focused on smaller, less liquid currencies. Securities The Company provides value-added solutions that facilitate cross-border trading and believes its clients value the Company’s ability to manage complex transactions, including foreign exchange, utilizing its local understanding of market convention, liquidity and settlement protocols around the world. The Company’s clients include U.S.-based regional and national broker-dealers and institutions investing or executing client transactions in international markets and foreign institutions seeking access to the U.S. securities markets. The Company is one of the leading market makers in foreign securities, making markets in over 5,000 ADRs, GDRs and foreign ordinary shares, of which over 3,600 trade in the OTC market. In addition, it will, on request, make prices in more than 10,000 unlisted foreign securities. The Company is also a broker-dealer in Argentina and Brazil where we are active in providing institutional executions in the local capital markets. The Company acts as an institutional dealer in fixed income securities, including U.S. Treasury, U.S. government agency, agency mortgage-backed and asset-backed securities as well as investment grade, high yield, convertible and emerging market debt to a client base including asset managers, commercial bank trust and investment departments, broker-dealers and insurance companies. The Company also originates, structures and places debt instruments in the international and domestic capital markets. These instruments include complex asset-backed securities (primarily in Argentina) and domestic municipal securities. On occasion, the Company may invest its own capital in debt instruments before selling them. The Company also actively trades in a variety of international debt instruments and operates an asset management business in which it earns fees, commissions and other revenues for management of third party assets and investment gains or losses on its investments in funds and proprietary accounts managed either by its investment managers or by independent investment managers. Physical Commodities The Physical Commodities segment consists of the Company’s Precious Metals trading and Physical Agricultural and Energy commodity businesses. In Precious Metals, the Company provides a full range of trading and hedging capabilities, including OTC products, to select producers, consumers, and investors. Through our websites, we provide clients the ability to purchase physical gold and other precious metals, in multiple forms, and in denominations of their choice. In the Company’s trading activities, it acts as a principal, committing its own capital to buy and sell precious metals on a spot and forward basis. In the Company’s Physical Ag & Energy commodity business, it acts as a principal to facilitate financing, structured pricing and logistics services to clients across the commodity complex, including energy commodities, grains, oil seeds, cotton, coffee, cocoa, edible oils and feed products. The Company provides financing to commercial commodity-related companies against physical inventories. The Company uses sale and repurchase agreements to purchase commodities evidenced by warehouse receipts, subject to a simultaneous agreement to sell such commodities back to the original seller at a later date. Transactions where the sale and repurchase price are fixed upon execution, and meet additional required conditions, are accounted for as product financing arrangements, and accordingly no commodity inventory, purchases or sales are recorded. Transactions where the repurchase price is not fixed at execution do not meet all the criteria to be accounted for as product financing arrangements, and therefore are recorded as commodity inventory, purchases and sales. INTL FCStone Ltd precious metals sales and cost of sales are presented on a net basis and included as a component of ‘principal gains, net’ in the consolidated income statements, in accordance with U.S GAAP accounting requirements for broker-dealers. Precious metals sales and cost of sales for subsidiaries that are not broker-dealers continue to be recorded on a gross basis. Precious metals inventory held by subsidiaries that are not broker-dealers continues to be valued at the lower of cost or market value. Precious metals sales and cost of sales for subsidiaries that are not broker-dealers continue to be recorded on a gross basis. The agricultural commodity inventories are carried at net realizable value, which approximates fair value less disposal costs. The agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. The Company records its Physical Ag & Energy commodities revenues on a gross basis. Operating revenues and losses from its precious metals commodities derivatives activities are included in ‘principal gains, net’ in the consolidated income statements. Operating revenues and losses from our Physical Ag and Energy commodity business are included in ‘cost of sales of physical commodities’ in the consolidated income statements The Company generally mitigates the price risk associated with commodities held in inventory through the use of derivatives. The Company does not elect hedge accounting under U.S. GAAP in accounting for this price risk mitigation. The Company’s management continues to evaluate performance and allocated resources on an operating revenue basis. Clearing and Execution Services (CES) The Company provides competitive and efficient clearing and execution in all major futures and securities exchanges globally as well as prime brokerage in equities and major foreign currency pairs and swap transactions. Through its platform, client orders are accepted and directed to the appropriate exchange for execution. The Company then facilitates the clearing of clients’ transactions. Clearing involves the matching of clients’ trades with the exchange, the collection and management of client margin deposits to support the transactions, and the accounting and reporting of the transactions to clients. As of September 30, 2019 , the Company’s U.S. FCM held $2.2 billion in required client segregated assets, which the Company believes makes it the third largest independent, non-bank FCM in the U.S. , as measured by required client segregated assets. The Company seeks to leverage its capabilities and capacity by offering facilities management or outsourcing solutions to other FCM’s. The Company is an independent full-service provider to introducing broker-dealers (“IBD’s”) of clearing, custody, research, syndicated and security-based lending products and services, including a proprietary technology platform which offers seamless connectivity to ensure a positive client experience through the clearing and settlement process. The Company’s independent wealth management business, which offers a comprehensive product suite to retail clients nationwide, clears through this platform. The Company believes it is one of the leading mid-market clearer’s in the securities industry, with approximately 70 correspondent clearing relationships with over $16 billion in assets under management or administration as of September 30, 2019 . The Company provides prime brokerage foreign exchange (“FX”) services to financial institutions and professional traders. The Company provides its clients with the full range of OTC products, including 24-hour a day execution of spot, forwards and options as well as non-deliverable forwards in both liquid and exotic currencies. The Company also operates a proprietary foreign exchange desk that arbitrages the exchange-traded foreign exchange markets with the cash markets. Through its London-based Europe, Middle East and Africa (“EMEA”) oil voice brokerage business, the Company provides brokerage services across the fuel, crude and middle distillates markets with well known commercial and institutional clients throughout EMEA. ******** 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 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 revenues generated, and in some cases, revenues generated less transaction-based clearing expenses, 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, expenses, receivables and payables are eliminated upon consolidation, except revenues and expenses 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 participants. 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 Year Ended September 30, (in millions) 2019 2018 2017 Total revenues: Commercial Hedging $ 302.4 $ 286.7 $ 244.6 Global Payments 112.8 99.2 89.2 Securities 295.3 196.2 151.7 Physical Commodities 31,864.7 26,703.8 28,684.4 Clearing and Execution Services 326.1 332.4 259.8 Corporate Unallocated 20.8 23.9 4.7 Eliminations (25.1 ) (19.5 ) (10.8 ) Total $ 32,897.0 $ 27,622.7 $ 29,423.6 Operating revenues: Commercial Hedging $ 302.4 $ 286.7 $ 244.6 Global Payments 112.8 99.2 89.2 Securities 295.3 196.2 151.7 Physical Commodities 73.8 56.9 44.8 Clearing and Execution Services 326.1 332.4 259.8 Corporate Unallocated 20.8 23.9 4.7 Eliminations (25.1 ) (19.5 ) (10.8 ) Total $ 1,106.1 $ 975.8 $ 784.0 Net operating revenues (loss): Commercial Hedging $ 236.5 $ 226.4 $ 194.3 Global Payments 107.0 93.5 80.6 Securities 131.0 94.6 94.6 Physical Commodities 56.3 44.8 37.3 Clearing and Execution Services 133.2 122.6 102.2 Corporate Unallocated (10.8 ) (0.3 ) (16.4 ) Total $ 653.2 $ 581.6 $ 492.6 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial Hedging $ 170.4 $ 164.7 $ 141.8 Global Payments 86.6 75.0 64.4 Securities 81.9 69.1 75.6 Physical Commodities 40.5 31.8 27.2 Clearing and Execution Services 103.4 91.8 78.0 Total $ 482.8 $ 432.4 $ 387.0 Segment income (loss): (Net contribution less non-variable direct segment costs) Commercial Hedging $ 100.1 $ 96.4 $ 72.8 Global Payments 66.1 59.8 50.6 Securities 47.4 40.8 46.6 Physical Commodities 38.0 16.6 (31.4 ) Clearing and Execution Services 54.1 48.3 30.4 Total $ 305.7 $ 261.9 $ 169.0 Reconciliation of segment income to income before tax: Segment income $ 305.7 $ 261.9 $ 169.0 Net costs not allocated to operating segments 200.2 162.4 153.8 Other gains 5.5 2.0 — Income before tax $ 111.0 $ 101.5 $ 15.2 (1) During fiscal 2019, the Company recorded recoveries on the bad debt on physical coal of $12.4 million. During fiscal 2018 and fiscal 2017, the Company recorded charges to earnings of $1.0 million and $47.0 million, respectively, to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business conducted solely in INTL Asia Pte. Ltd., with a coal supplier, as further discussed in Note 18 . (2) The costs not allocated to operating segments include certain shared services such as information technology, accounting and treasury, credit and risk, legal and compliance, and human resources and other activities. (in millions) As of September 30, 2019 As of September 30, 2018 As of September 30, 2017 Total assets: Commercial Hedging $ 2,041.0 $ 1,935.7 $ 1,650.3 Global Payments 278.3 206.6 199.5 Securities 5,219.1 3,058.2 2,101.7 Physical Commodities 357.8 413.7 339.5 Clearing and Execution Services 1,892.1 2,109.9 1,818.9 Corporate unallocated 147.8 100.6 133.5 Total $ 9,936.1 $ 7,824.7 $ 6,243.4 Information regarding revenues and operating revenues for the years ended September 30, 2019, 2018, and 2017 , and information regarding long-lived assets (defined as property, equipment, leasehold improvements and software) as of September 30, 2019, 2018, and 2017 in geographic areas were as follows: Year Ended September 30, (in millions) 2019 2018 2017 Total revenues: United States $ 1,947.6 $ 1,587.6 $ 1,168.0 Europe 280.2 189.6 166.9 South America 56.5 59.5 53.9 Middle East and Asia 30,606.9 25,781.4 28,030.3 Other 5.8 4.6 4.5 Total $ 32,897.0 $ 27,622.7 $ 29,423.6 Operating revenues: United States $ 799.4 $ 695.3 $ 529.4 Europe 209.6 189.0 166.9 South America 56.5 58.0 54.0 Middle East and Asia 34.8 28.9 29.2 Other 5.8 4.6 4.5 Total $ 1,106.1 $ 975.8 $ 784.0 (in millions) As of September 30, 2019 As of September 30, 2018 As of September 30, 2017 Long-lived assets, as defined: United States $ 33.9 $ 33.0 $ 29.7 Europe 6.6 6.8 7.3 South America 2.1 1.4 1.5 Middle East and Asia 1.0 1.2 0.2 Other 0.3 — — Total $ 43.9 $ 42.4 $ 38.7

Condensed Parent Only Financial

Condensed Parent Only Financial Statements (Notes)	12 Months Ended
	Sep. 30, 2019
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure [Text Block]	Schedule I INTL FCStone Inc. Condensed Balance Sheets Parent Company Only (in millions) September 30, September 30, ASSETS Cash and cash equivalents $ 2.0 $ 1.8 Receivable from subsidiaries, net 17.6 23.3 Receivable from clients 0.5 — Notes receivable, net 2.8 1.8 Income taxes receivable 15.7 14.9 Investment in subsidiaries (1) 399.4 318.0 Financial instruments owned, at fair value 0.0 4.4 Deferred income taxes, net 8.2 8.8 Property and equipment, net 26.9 25.9 Other assets 13.0 7.6 Total assets $ 486.1 $ 406.5 LIABILITIES AND EQUITY Liabilities: Accounts payable and other accrued liabilities $ 29.4 $ 23.0 Payable to clients 0.3 1.7 Payable to lenders under loans 70.4 209.4 Senior term loan 167.6 — Financial instruments sold, not yet purchased, at fair value 84.5 59.3 Total liabilities 352.2 293.4 Equity: INTL FCStone Inc. (Parent Company Only) stockholders’ equity: Preferred stock, $0.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding — — Common stock, $0.01 par value. Authorized 30,000,000 shares; 21,297,317 issued and 19,075,360 outstanding at September 30, 2019 and 21,030,497 issued and 18,908,540 outstanding at September 30, 2018 0.2 0.2 Common stock in treasury, at cost - 2,221,957 shares at September 30, 2019 and 2,121,957 shares at September 30, 2018 (50.1 ) (46.3 ) Additional paid-in capital 276.8 267.5 Retained earnings (1) (93.0 ) (108.3 ) Total INTL FCStone Inc. (Parent Company Only) stockholders’ equity 133.9 113.1 Total liabilities and equity $ 486.1 $ 406.5 (1) Within the Condensed Balance Sheets and Condensed Statements of Operations of INTL FCStone Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, investment in subsidiaries and retained earnings would each increase by $495.1 million as of September 30, 2019, respectively, and $425.3 million , as of September 30, 2018, respectively. Schedule I INTL FCStone Inc. Condensed Statements of Operations Parent Company Only Year Ended September 30, (in millions) 2019 2018 2017 Revenues: Management fees from affiliates $ 43.2 $ 40.4 $ 39.1 Trading losses, net — — (1.0 ) Consulting fees 0.1 — — Interest income 1.5 2.3 1.2 Dividend income from subsidiaries (2) 85.7 41.9 52.7 Total revenues 130.5 84.6 92.0 Interest expense 19.7 15.7 14.4 Net revenues 110.8 68.9 77.6 Non-interest expenses: Compensation and benefits 79.7 73.0 60.3 Clearing and related expenses 0.9 1.1 1.2 Trade systems and market information (3) 6.4 5.8 6.4 Occupancy and equipment rental 3.4 2.6 2.5 Professional fees 7.3 6.7 3.7 Travel and business development 2.9 2.6 2.7 Non-trading technology and support (3) 12.5 9.1 7.4 Depreciation and amortization 5.2 4.8 3.3 Communications (3) 0.8 0.9 0.9 Management services fees to affiliates 0.5 — — Other (3) 5.8 6.9 5.6 Total non-interest expenses 125.4 113.5 94.0 Other gains 5.3 — — Loss from operations, before tax (9.3 ) (44.6 ) (16.4 ) Income tax benefit 24.6 7.4 26.8 Net (loss) income $ 15.3 $ (37.2 ) $ 10.4 (2) W ithin the Condensed Balance Sheets and Condensed Statements of Operations of INTL FCStone Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, revenues would include income from investment in subsidiaries of $69.8 million and $92.7 million for the years ended September 30, 2019 and 2018, respectively, and a loss from investment in subsidiaries of $4.0 million for the year ended September 30, 2017. (3) During the year ended September 30, 2018, the Company separately classified non-trading technology and support costs that were previously included within ‘Other’ on the Condensed Statements of Operations of INTL FCStone Inc. - Parent Company Only. Additionally, during the year ended September 30, 2018, 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 the current period presentation. For the year ended September 30, 2017, ‘Other’ expenses included $7.4 million of expenses that are now included within ‘Non-trading technology and support’ on the Condensed Statements of Operations of INTL FCStone Inc. - Parent Company Only. For the year ended September 30, 2017, ‘Trading systems and market information’ included $0.9 million of expenses that are now included within ‘Communications’ on the Condensed Statements of Operations of INTL FCStone Inc. - Parent Company Only. Schedule I INTL FCStone Inc. Condensed Statements of Cash Flows Parent Company Only Year Ended September 30, (in millions) 2019 2018 2017 Cash flows from operating activities: Net income (loss) $ 15.3 $ (37.2 ) $ 10.4 Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Depreciation and amortization 5.2 4.8 3.3 Deferred income taxes 0.6 18.0 (10.7 ) Amortization and extinguishment of debt issuance costs 1.2 0.7 1.7 Amortization of share-based compensation expense 7.1 6.1 5.5 Gain on acquisition (5.4 ) — — Changes in operating assets and liabilities: Deposits with and receivables from broker-dealers, clearing organizations, and counterparties — — 2.9 Receivables from subsidiaries, net — (0.8 ) (0.3 ) Due to/from subsidiaries 8.3 (68.6 ) 27.0 Receivables from clients, net (0.5 ) — — Notes receivable, net (1.0 ) 2.9 2.1 Income taxes receivable (0.8 ) (6.6 ) 5.4 Financial instruments owned, at fair value 4.4 (4.4 ) 1.3 Other assets (4.4 ) (0.7 ) 7.8 Accounts payable and other accrued liabilities 4.6 8.6 (7.8 ) Payable to clients (1.4 ) (0.3 ) (2.5 ) Financial instruments sold, not yet purchased, at fair value 25.2 34.0 (10.6 ) Net cash provided by (used in) operating activities 58.4 (43.5 ) 35.5 Cash flows from investing activities: Capital contribution in affiliates (75.8 ) (4.5 ) — Purchase of property and equipment (6.2 ) (5.9 ) (6.1 ) Net cash used in investing activities (82.0 ) (10.4 ) (6.1 ) Cash flows from financing activities: Net change in lenders under loans (138.2 ) 58.2 13.5 Payments of notes payable (0.8 ) (0.8 ) (0.8 ) Repayment of senior unsecured notes — — (45.5 ) Proceeds from issuance of senior secured term loan 175.0 — — Repayments of senior secured term loan (6.6 ) — — Deferred payments on acquisitions — (5.5 ) — Share repurchase (3.8 ) — — Debt issuance costs (3.0 ) — — Exercise of stock options 1.2 2.6 3.4 Withholding taxes on stock option exercises — (0.8 ) — Income tax benefit on stock options and awards — — 0.7 Net cash provided by (used in) financing activities 23.8 53.7 (28.7 ) Net increase (decrease) in cash and cash equivalents 0.2 (0.2 ) 0.7 Cash and cash equivalents at beginning of period 1.8 2.0 1.3 Cash and cash equivalents at end of period $ 2.0 $ 1.8 $ 2.0 Supplemental disclosure of cash flow information: Cash paid for interest $ 18.9 $ 15.0 $ 8.2 Income taxes (received) paid, net of cash refunds $ (23.9 ) $ (18.4 ) $ (22.3 ) Supplemental disclosure of non-cash investing and financing activities: Additional consideration payable related to acquisitions $ 1.8 $ — $ (0.2 )

Description of Business and S_2

Description of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Product Financing Arrangements [Policy Text Block]	In the normal course of operations the Company executes notes receivable under repurchase agreements with clients whereby the clients sell certain commodity inventory or other investments to the Company and agree to repurchase the commodity inventory or investment at a future date at a fixed price. These transactions are short-term in nature, and in accordance with the guidance contained in ASC 860, Transfer and Servicing, are treated as secured borrowings rather than commodity inventory and purchases and sales in the Company’s consolidated financial statements. These transactions are reflected as ‘notes receivable’ in the consolidated balance sheet. Commodities or investments sold under repurchase agreements are reflected at the amount of cash received in connection with the transactions. The Company may be required to provide additional collateral based on the fair value of the underlying asset. The Company also participates in commodity repurchase transactions that are accounted for as commodity inventory and purchases and sales of physical commodities as opposed to secured borrowings. The repurchase price under these arrangements is not fixed at the time of execution and, therefore, do not meet all the criteria to be accounted for as product financing arrangements.
Basis of Presentation, Policy [Policy Text Block]	Basis of Presentation The accompanying 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. Unless otherwise stated herein, all references to fiscal 2019 , fiscal 2018 , and fiscal 2017 refer to the Company’s fiscal years ended September 30. In the 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 consolidated income statements is calculated by deducting physical commodities cost of sales from total revenues. The subtotal ‘net operating revenues’ in the 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 clients 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.
Consolidation, Policy [Policy Text Block]	The accompanying 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]	Unless otherwise stated herein, all references to fiscal 2019 , fiscal 2018 , and fiscal 2017 refer to the Company’s fiscal years ended September 30.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments, revenue recognition, the provision for probable losses from bad debts, valuation of inventories, and incomes taxes and contingencies. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. The Company reviews all significant estimates affecting the financial statements on a recurring basis and records the effect of any necessary adjustments prior to their issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates.
Foreign Currency Translations Policy [Policy Text Block]	Foreign Currency Translation The Company’s consolidated financial statements are reported in U.S. dollars. The Company’s foreign subsidiaries maintain their records either in U.S. dollars or in certain instances the currency of the country in which they operate. The method of translating local currency financial information into U.S. dollars depends on whether the economy in which the foreign subsidiary operates has been designated as highly inflationary or not. Economies with a three-year cumulative inflation rate of more than 100% are considered highly inflationary. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expense are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in earnings. Foreign subsidiaries that operate in highly inflationary countries use the U.S. dollar as their functional currency. Local currency monetary assets and liabilities are remeasured into U.S. dollars using rates of exchange as of each balance sheet date, with remeasurement adjustments and other transaction gains and losses recognized in earnings. Nonmonetary assets and liabilities do not fluctuate with changes in the local currency exchange rates to the dollar as the translated amounts for nonmonetary assets and liabilities at the end of the accounting period in which the economy becomes highly inflationary becomes the accounting basis for those assets and liabilities in the period of change and subsequent periods. Revenues and expenses are translated at rates of exchange in effect during the year. The Company operates asset management and debt trading businesses in Argentina through various wholly-owned subsidiaries. Operating revenues from the Argentinean subsidiaries represented approximately 2% of the consolidated operating revenues for the year ended September 30, 2019. The operating environment in Argentina continues to present business challenges, including ongoing devaluation of the Argentine peso and significant inflation. For the year ended September 30, 2018, the Argentine peso declined approximately 139% (from 17.3 to 41.3 pesos to the U.S. dollar). Based upon inflationary data published by the International Practices Task Force of the Center for Audit Quality, the economy of Argentina became highly inflationary during the three months ended June 30, 2018. Beginning July 1, 2018, the Company designated Argentina’s economy as highly inflationary for accounting purposes. As a result, the Company has accounted for the Argentinean entities using the U.S. dollar as their functional currency beginning in the quarter ending September 30, 2018. Argentine peso-denominated monetary assets and liabilities are remeasured at each balance sheet date to the currency exchange rate then in effect, with currency remeasurement gains and loses recognized in earnings. The translated balances for nonmonetary assets and liabilities as of June 30, 2018, became the accounting basis for those assets in the period of change and subsequent periods. As a result of Argentina’s highly inflationary status, the Company recorded translation losses through earnings of $3.9 million and $3.4 million for the years ended September 30, 2019 and 2018, respectively. At September 30, 2019 and 2018, the Company had net monetary assets denominated in Argentine pesos of $5.5 million and $11.6 million , respectively, including cash and cash equivalents of $0.1 million and $1.4 million , respectively. At September 30, 2019 and 2018, the Company had net nonmonetary assets denominated in Argentine pesos of $1.0 million .
Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents The Company considers cash held at banks and all highly liquid investments not held for trading purposes, with original or acquired maturities of 90 days or less, including certificates of deposit and money market mutual funds, to be cash and cash equivalents. Cash and cash equivalents consist of cash, foreign currency, certificates of deposit, and money market mutual funds not deposited with or pledged to clearing organizations, broker-dealers, clearing organizations or counterparties, or segregated under federal or other regulations. Certificates of deposit are stated at cost plus accrued interest, which approximates fair value, and may be withdrawn at any time at the discretion of the Company without penalty. Money market mutual funds are stated at their net asset value.
Cash, Securities and Other Assets Segregated, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Cash, Securities and Other Assets Segregated under Federal and other Regulations Pursuant to requirements of the Commodity Exchange Act and Commission Regulation 30.7 of the U.S. Commodity Futures Trading Commission (“CFTC”) in the U.S. and similarly in the United Kingdom (“U.K.”), pursuant to the Markets in Financial Instruments Implementing Directive 2006/73/EC underpinning the Client Asset (“CASS”) rules in the Financial Services Authority (“FSA”) handbook, funds deposited by clients relating to futures and options on futures contracts in regulated commodities must be carried in separate accounts which are designated as segregated client accounts. Additionally, in accordance with Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), the Company maintains separate accounts for the exclusive benefit of securities clients and proprietary accounts of broker dealers (“PABs”). Rule 15c3-3 requires the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. The deposits in segregated client accounts and SRBAs are not commingled with the funds of the Company. Under the FSA’s rules, certain categories of clients may choose to opt-out of segregation. As of September 30, 2019 and 2018 , cash, securities, and other assets segregated under federal and other regulations consisted of cash held at banks of approximately $743.9 million and $765.4 million , respectively, U.S. Treasury obligations of approximately $299.8 million and $600.4 million , respectively, and commodities warehouse receipts of approximately $6.2 million and $42.9 million , respectively (see fair value measurements discussion in Note 4 ).
Commodity Repurchase and Other Repurchase Agreements Policy [Policy Text Block]	The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed transactions, and securities loaned transactions primarily to fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, or meet counterparty needs under matched-booked trading strategies. These transactions are accounted for as collateralized financing transactions and are recorded at their contractual amounts plus accrued interest. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to collateralize such agreements and transactions in accordance with contractual arrangements. The Company monitors the fair value of the collateral on a daily basis and the Company may require counterparties, or may be required by counterparties, to deposit additional collateral or return collateral pledged. Interest income and interest expense are recognized over the life of the arrangements and are recorded in the statement of income as interest income or interest expense, as applicable. The carrying amount of these transactions approximate fair value due to their short-term nature and the level of collateralization. These transactions are reported gross, except when a right of offset exists and the other criteria for netting under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 210-20, Balance Sheet - Offsetting are met.
Deposits and Receivables from Exchange-Clearing Organizations, Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties Disclosure [Text Block]	Deposits with and Receivables from Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties As required by the regulations of the CFTC and the aforementioned FSA handbook, client funds received to margin, guarantee, and/or secure commodity futures and futures on options transactions are segregated and accounted for separately from the general assets of the Company. Deposits with broker-dealers, clearing organizations, and counterparties pertain primarily to deposits made to satisfy margin requirements on client and proprietary open futures and options on futures positions and to satisfy the requirements set by clearing exchanges for clearing membership. The Company also pledges margin deposits with various counterparties for over-the-counter (“OTC”) derivative contracts, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. The Company also deposits cash margin with various securities clearing organizations as an ongoing condition of the securities clearing relationships, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties are reported gross, except where a right of offset exists. As of September 30, 2019 and 2018 , the Company had cash and cash equivalents on deposit with or pledged to broker-dealers, clearing organizations, and counterparties of approximately $1.6 billion and $1.5 billion , respectively. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes guaranty deposits with clearing exchanges. The guaranty deposits are held by the clearing exchanges for use in potential default situations by one or more members of the clearing exchanges. The guaranty deposits may be applied to the Company’s obligations to the clearing exchange, or to the clearing exchange’s obligations to unrelated parties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include securities pledged to clearing exchanges. These securities are either pledged to the Company by its clients or represent investments of client funds. It is the Company’s practice to include client-owned securities on its consolidated balance sheets, as the rights to those securities have been transferred to the Company under the terms of the futures trading agreements. Securities pledged primarily include U.S. Treasury obligations, foreign government obligations, and certain exchange-traded funds (“ETFs”). Securities that are not client-owned, and represent an investment of client funds, are adjusted to fair value with associated changes in unrealized gains or losses recorded in ‘interest income’ in the consolidated income statements. For client-owned securities, the change in fair value is offset against the payable to clients with no impact recognized in the consolidated income statements. The fair value of these securities included within deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $603.8 million and $785.8 million as of September 30, 2019 and 2018 , respectively. Management has considered guidance required by ASC 860, Transfers and Servicing as it relates to securities pledged by clients to margin their futures and options on futures trading accounts. Based on a review of the agreements with the client, management believes the transferor surrenders control over those assets because: (a) the transferred assets have been isolated from the transferor—put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (b) each transferee has the right to pledge or exchange the assets (or beneficial interests) it received, and no condition both constrains the transferee (or holder) from taking advantage of its right to pledge or exchange and provides more than a trivial benefit to the transferor and (c) the transferor does not maintain effective control over the transferred assets through either (1) an agreement that both entitles and obligates the transferor to repurchase or redeem them before their maturity or (2) the ability to unilaterally cause the holder to return specific assets, other than through a cleanup call. Under this guidance, the Company reflects the client collateral assets and corresponding liabilities in the Company’s consolidated balance sheets as of September 30, 2019 and 2018 . Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes amounts due from clearing exchanges for unrealized gains and losses associated with clients’ options on futures contracts. See discussion in the Financial Instruments section below for additional information on the Company’s accounting policies for derivative contracts. For client-owned derivative contracts, the fair value is offset against the payable to clients with no impact recognized on the consolidated income statements. The Company maintains client omnibus and proprietary accounts with other clearing organizations, and the equity balances in those accounts along with any margin cash or securities deposited with the clearing organizations are included in deposits with and receivables from broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include amounts due from or due to clearing exchanges for daily variation settlements on open futures and options on futures positions. The variation settlements due from or due to clearing exchanges are paid in cash on the following business day. Variation settlements equal the daily settlement of futures contracts and premiums on options on futures contracts. Receivables from broker-dealers and counterparties also include amounts receivable for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payables to broker-dealers and counterparties primarily include amounts payable for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivables from broker-dealers, clearing organizations and counterparties, and payables to broker-dealers, clearing organizations and counterparties also include amounts related to the value of registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days.
Receivable from and Payable to Customers, Policy [Policy Text Block]	Receivable from and Payable to Clients Receivable from clients, net of the allowance for doubtful accounts, include the total of net deficits in individual exchange-traded futures and OTC derivative trading accounts carried by the Company. Client deficits arise from realized and unrealized trading losses on client futures, options on futures, swaps and forwards and amounts due on cash and margin transactions. Client deficit accounts are reported gross of client accounts that contain net credit or positive balances, except where a right of offset exists. Net deficits in individual futures exchange-traded and OTC derivative trading accounts include both secured and unsecured deficit balances due from clients as of the balance sheet date. Secured deficit amounts are backed by U.S. Treasury obligations and commodity warehouse receipts. These U.S Treasury obligations and commodity warehouse receipts are not netted against the secured deficit amounts, as the conditions for right of setoff have not been met. Receivable from clients, net also includes the net amounts receivable from securities clients in connection with the settlement of regular-way cash securities, margin loans to clients, and client cash debits. It is the Company’s policy to report margin loans and payables that arise due to positive cash flows in the same client’s accounts on a net basis when the conditions for netting as specified in U.S. GAAP are met. Clients’ securities transactions cleared by the Company are recorded on a settlement date basis. Securities cleared by the Company and pledged to the Company as a condition of the custodial clearing arrangements are owned by the clients, including those that collateralize margin or other similar transactions, and are not reflected on the consolidated balance sheets as the Company does not have title to, or beneficial interests, in those assets. In the event of uncompleted transactions on settlement date, the Company records corresponding receivables and payables, respectively. The carrying value of the receivables and payables approximates fair value due to their short-term nature. Receivables from clients, net also include amounts receivable from non-broker-dealer clients for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payable to clients represent the total of client accounts with credit or positive balances. Client accounts are used primarily in connection with exchange-traded and OTC commodity, foreign exchange, precious metals, and securities transactions and include gains and losses on open trades as well as securities and cash margin deposits made as required by the Company, the exchange-clearing organizations or other clearing organizations. Client accounts with credit or positive balances are reported gross of client deficit accounts, except where a right of offset exists. Payables to broker-dealers and counterparties also includes amounts payable to non-broker-dealer clients for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivable from and payables to clients also include amounts related to the value of non-registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. The future collectability of receivables from clients can be impacted by the Company’s collection efforts, the financial stability of its clients, and the general economic climate in which it operates. The Company evaluates accounts that it believes may become uncollectible on a specific identification basis, through reviewing daily margin deficit reports, the historical daily aging of the receivables, and by monitoring the financial strength of its clients. The Company may unilaterally close client trading positions in certain circumstances. In addition, to evaluate client margining and collateral requirements, client positions are stress tested regularly and monitored for excessive concentration levels relative to the overall market size. Furthermore, in certain instances, the Company is indemnified, and able to charge back, introducing broker-dealers for bad debts incurred by their clients. The Company generally charges off an outstanding receivable balance when all economic means of recovery have been exhausted. That determination considers information such as the occurrence of significant changes in the client’s financial position such that the client can no longer pay the obligation, or that the proceeds from collateral will not be sufficient to pay the balance.
Notes Receivable, Policy [Policy Text Block]	Notes Receivable Accrual of commodity financing income on any note is discontinued when, in the opinion of management, there is reasonable doubt as to the timely collectability of interest or principal. Nonaccrual notes are returned to an accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely payment of principal and interest. The Company records a charge against earnings for notes receivable losses when management believes that the collection of outstanding principal is not probable.
Physcial Commodities Inventory, Policy [Policy Text Block]	Physical Commodities Inventory Inventories of certain agricultural commodities are carried at net realizable value, which approximates fair value less disposal costs. The agricultural commodities inventories have reliable, readily determinable and realizable market prices, have relatively predictable and insignificant costs of disposal and are available for immediate delivery. Changes in the fair values of these agricultural commodities inventories are included as a component of ‘cost of sales of physical commodities’ in the consolidated income statements. Inventories of energy related products are valued at the lower of cost or net realizable value. Inventories of precious metals held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value, using the weighted-average price and first-in first-out costing method. Precious metals inventory held by INTL FCStone Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ in the consolidated income statements.
Property and Equipment, Policy [Policy Text Block]	Property and Equipment Property and equipment is stated at cost, net of accumulated depreciation and amortization and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the estimated useful life of the improvement or the term of the lease, whichever is shorter. Certain costs of software developed or obtained for internal use are capitalized and amortized over the estimated useful life of the software. Expenditures for maintenance, repairs, and minor replacements are charged against earnings, as incurred. Expenditures that increase the value or productive capacity of assets are capitalized. When property and equipment are retired, sold, or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in earnings.
Goodwill and Intangible Assets, Policy [Policy Text Block]	Goodwill and Identifiable Intangible Assets Goodwill is the cost of acquired companies in excess of the fair value of identifiable net assets at the acquisition date. Goodwill is not subject to amortization, but rather is evaluated for impairment at least annually. The Company evaluates its goodwill for impairment at the fiscal year end (or more frequently if indicators of potential impairment exist) in accordance with ASC 350, Intangibles - Goodwill and Other. Goodwill impairment is determined by comparing the estimated fair value of a reporting unit with its respective carrying value. If the estimated fair value exceeds the carrying value, goodwill at the reporting unit level is not deemed to be impaired. However, if the estimated fair value is below carrying value, further analysis is required to determine the amount of the impairment. This further analysis involves assigning tangible assets and liabilities, identified intangible assets and goodwill to reporting units and comparing the fair value of each reporting unit to its carrying amount. In the course of the evaluation of the potential impairment of goodwill, the Company may perform either a qualitative or a quantitative assessment. The Company’s qualitative assessment of potential impairment may result in the determination that a quantitative impairment analysis is not necessary. Under this elective process, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads the Company to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If after assessing the totality of events or circumstances, the Company determines it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then performing a quantitative analysis is not required. However, if the Company concludes otherwise, then the Company performs a quantitative impairment analysis. If the Company either chooses not to perform a qualitative assessment, or the Company chooses to perform a qualitative assessment but is unable to qualitatively conclude that no impairment has occurred, then the Company performs a quantitative evaluation. In the case of a quantitative assessment, the Company estimates the fair value of the reporting unit which the goodwill that is subject to the quantitative analysis is associated (generally defined as the businesses for which financial information is available and reviewed regularly by management) and compares it to the carrying value. If the estimated fair value of a reporting unit is less than its carrying value, the Company estimates the fair value of all assets and liabilities of the reporting unit, including goodwill. If the carrying value of the reporting unit’s goodwill is greater than the estimated fair value, an impairment charge is recognized for the excess. The fair value of the Company’s reporting units exceeded their respective carrying values under the first step of the quantitative assessment and no impairment charges were recorded for any of the periods presented. Identifiable intangible assets subject to amortization are amortized using the straight-line method over their estimated period of benefit, ranging from five to twenty years. Identifiable intangible assets are tested for impairment whenever events or changes in circumstances suggest that an asset’s or asset group’s carrying value may not be fully recoverable. Residual value is presumed to be zero for all identifiable intangible assets.
Financial Instruments and Derivatives, Policy [Policy Text Block]	Financial Instruments Owned and Sold, Not Yet Purchased Financial instruments owned and sold, not yet purchased, at fair value consist of financial instruments carried at fair value on a recurring basis or amounts that approximate fair value, with related realized and unrealized gains and losses recognized in current period earnings. Realized and unrealized gains and losses on financial instruments owned and sold, not yet purchased, are included in ‘principal gains, net’, ‘interest income’, ‘interest expense’, and ‘cost of sales of physical commodities’ in the consolidated income statements. The fair value of a financial instrument is the amount at which the instrument could be exchanged in a current transaction between willing parties, other than in a forced or liquidation sale. Financial instruments owned and sold, not yet purchased are comprised primarily of the financial instruments held by the Company’s broker-dealer subsidiaries and the Company’s OTC derivative swap dealer. Financial instruments owned and financial instruments sold, not yet purchased, includes trading securities that the Company holds as a principal. The Company has not classified any financial instruments owned or sold, not yet purchased, as available-for-sale or held-to-maturity. Financial instruments owned and sold, not yet purchased includes derivative instruments that the Company holds as a principal which are primarily transacted on an OTC basis. As a derivatives dealer, the Company utilizes derivative instruments to manage exposures to foreign currency, commodity price and interest rate risks for the Company and its clients. The Company’s objectives for holding derivatives include reducing, eliminating, and efficiently managing the economic impact of these exposures as effectively as possible. The Company’s derivative instruments also include forward purchase and sale commitments for the physical delivery of agricultural and energy related commodities in a future period. Contracts to purchase agricultural and energy commodities generally relate to the current or future crop year. Contracts for the sale of agricultural and energy commodities generally do not extend beyond one year. Derivative instruments are recognized as either assets or liabilities and are measured at fair value on a recurring basis. As the Company does not elect hedge accounting for any derivative instruments, realized and unrealized gains and losses from the change in fair value of derivative instruments are recognized immediately in current period earnings. Realized and unrealized gains and losses from the derivative instruments in which the Company acts as a dealer are included within ‘principal gains, net’ on the consolidated income statements. Realized and unrealized gains and losses on firm purchase and sale commitments are included within ‘cost of sales of physical commodities’ on the consolidated income statements. To reduce credit exposure on the derivative instruments for which the Company acts as a dealer, the Company may enter into a master netting arrangement that allows for settlement of all derivative transactions with each counterparty. In addition, the credit support annex that accompanies master netting arrangements allows parties to the master netting agreement to mitigate their credit risk by requiring the party which is out of the money to post collateral. The Company accepts collateral in the form of cash or other marketable securities. Where permitted, the Company elects to net-by-counterparty certain derivative instruments entered into under a legally enforceable master netting agreement and, therefore, the fair value of those derivative instruments are netted by counterparty in the consolidated balance sheets. As the Company elects to net-by-counterparty the fair value of such derivative instruments, the Company also nets-by-counterparty cash collateral exchanged as part of those derivative instruments. The Company also brokers foreign exchange forwards, options and cash, or spot, transactions between clients and external counterparties. A portion of the contracts are arranged on an offsetting basis, limiting the Company’s risk to performance of the two offsetting parties. The offsetting nature of the contracts eliminates the effects of market fluctuations on the Company’s operating results. Due to the Company’s role as a principal participating in both sides of these contracts, the amounts are presented gross on the consolidated balance sheets at their respective fair values, net of offsetting assets and liabilities. The Company holds proprietary positions in its foreign exchange line of business. On a limited basis, the Company’s foreign exchange trade desk will accept a client transaction and will offset that transaction with a similar but not identical position with a counterparty. These unmatched transactions are intended to be short-term in nature and are often conducted to facilitate the most effective transaction for the Company’s client. These spot and forward contracts are accounted for as free-standing derivatives and reported in the consolidated balance sheets at their fair values. The Company may lease commodities to or from clients or counterparties. These commodity leases, which primarily involve precious metals, are recorded at fair value utilizing the fair value option based on guidance in ASC 825-10, Financial Instruments - Fair Value Option. These commodities leases represent hybrid financial instruments which contain both a dollar denominated loan host contract and an embedded forward derivative contract on the underlying commodities, which can be settled in either cash or metals. As permitted by the fair value option election, the entire instrument is recorded at fair value as either an asset or liability in the consolidated balance sheets. The corresponding change in the fair value of the instrument is recognized in the consolidated income statements as a component of ‘principal gains, net’ for the fiscal years ended September 30, 2019, 2018, and 2017 . The Company does elect to value all of their commodities lease agreements at fair value using the fair value option.
Exchange Memberships and Stock, Policy [Policy Text Block]	Exchange and Clearing Organization Memberships The Company is required to hold certain exchange and clearing organization memberships and pledges them for clearing purposes, in order to provide the Company the right to process trades directly with the respective venues. Exchange memberships include seats on the Chicago Board of Trade (“CBOT”), the Minneapolis Grain Exchange, the New York Mercantile Exchange (“NYMEX”), the Commodity Exchange, Inc. (“COMEX”) Division of the New York Mercantile Exchange, Mercado de Valores de Buenos Aires S.A. (“MERVAL”), the Chicago Mercantile Exchange (“CME”) Growth and Emerging Markets, InterContinental Exchange, Inc. (“ICE”) Futures US, ICE Europe Ltd and London Metal Exchange (“LME”). Exchange firm and clearing organization common stock include shares of CME Group, Inc., ICE, LME, and the Depository Trust & Clearing Corporation (“DTCC”). Exchange and clearing organization memberships required in order to conduct business through the respective venues are recorded at cost and are included in ‘other assets’ on the consolidated balance sheets. Equity investments in exchange firm common stock not required in order to conduct business on the exchanges are classified as trading securities included within ‘financial instruments owned’ on the consolidated balance sheets and recorded at fair value, with unrealized gains and losses recorded as a component of ‘principal gains, net’ on the consolidated income statements. The fair value of exchange firm common stock not required in order to conduct business on the exchanges is determined from quoted market prices. Exchange memberships that represent (a) both an ownership interest and the right to conduct business in the respective venues and are held for operating purposes, or (b) an ownership interest, which must be held by the Company to conduct business in the respective venues are accounted for as an ownership interest at cost with appropriate consideration for other-than-temporary impairment. The cost of exchange and clearing organization memberships that represent an ownership interest and are required in order to conduct business in the respective venues was $5.6 million as of September 30, 2019 and 2018 compared to a fair value of $6.0 million and $6.4 million as of September 30, 2019 and 2018 , respectively. Fair value was determined using quoted market prices and recent transactions. Alternatively, exchange memberships, or seats, that only represent the right to conduct business on an exchange, but not an ownership interest in the exchange, are accounted for as intangible assets at cost with potential impairment determined under Accounting Standards Codification 350-30- Intangibles - Goodwill and Other . The cost of exchange memberships required in order to conduct business on the exchange, but that do not represent an ownership interest in the exchange, was $5.8 million as of September 30, 2019 and 2018 . As of September 30, 2019, there were no indicators of impairment that would suggest that the carrying value of exchange memberships that don’t represent an ownership interest are impaired, primarily based upon projections of future cash flows and earnings attributable to access these respective venues.
Debt, Policy [Policy Text Block]	Lenders Under Loans Lenders under loans are accounted for at amortized cost, which approximates fair value due to their variable rates of interest. Senior Secured Term Loan The senior secured term loan is accounted for at amortized cost, which approximates fair value due to its variable rate of interest.
Business Combinations and Contingent Consideration Policy [Policy Text Block]	When acquiring companies, the Company recognizes separately from goodwill most of the identifiable assets acquired and the liabilities assumed at their acquisition date fair values. Certain contingent liabilities acquired require remeasurement at fair value in each subsequent reporting period. Goodwill as of the acquisition date is measured as the excess of consideration transferred and the net of the acquisition fair values of the assets acquired and liabilities assumed. While the Company used its best estimates and assumptions as a part of the purchase price allocation to accurately value assets acquired and liabilities assumed at the acquisition date, these estimates are inherently uncertain and subject to refinement. As a result, during the remeasurement period, which may up to one year from the acquisition date, the Company records adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon conclusion of the measurement period or final determination of the values of assets acquired and liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the consolidated income statements rather than adjusted through goodwill. Acquisition related costs, such as fees for attorneys, accountants, and investment bankers, are expensed as incurred and are not capitalized as part of the purchase price. Determining the fair value of certain identifiable assets acquired and liabilities assumed is subjective in nature and often involves the use of significant estimates and assumptions. Estimating the fair value of the assets and liabilities acquired requires significant judgment. These estimates and assumptions are based in part on historical experience, market data, and information obtained from the management of the acquired companies. Among the significant estimates used to value certain identifiable intangible assets acquired in acquisitions include, but are not limited to future expected cash flows from customer relationships and discount rates. Contingent Consideration The Company estimates and records the acquisition date estimated fair value of contingent consideration as part of purchase price consideration for acquisitions. Additionally, each reporting period, the Company estimates changes in the fair value of contingent consideration, and any change in fair value is recognized in the consolidated income statements. An increase in the contingent consideration expected to be paid will result in a charge to operations in the period that the anticipated fair value of contingent consideration increases, while a decrease in the earn-out expected to be paid will result in a credit to operations in the period that the anticipated fair value of contingent consideration decreases. The estimate of the fair value of contingent consideration requires subjective assumptions to be made of future operating results, discount rates, and probabilities assigned to various potential operating result scenarios.
Additional Paid-In Capital, Policy [Policy Text Block]	Additional Paid-In Capital The Company’s additional paid-in capital (“APIC”) consists of stockholder contributions that are in excess of par value of common stock. Included in APIC are amounts related to the exercise of stock options and amortization of share-based compensation.
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition Refer to Note 2 for a discussion of the Company’s significant accounting policies related to revenue recognition.
Cost of of Sales Physical Commodities, Policy [Policy Text Block]	Cost of Sales of Physical Commodities Cost of sales of physical commodities include finished commodity or raw material and processing costs along with operating costs relating to the receipt, storage and delivery of the physical commodities. Cost of sales of physical commodities also includes changes in the fair value of agricultural commodity inventories held for sale, and related forward purchase and sale commitments and exchange-traded futures and options contracts.
Interest Expense, Policy [Policy Text Block]	Interest Expense Interest expense is recognized on an accrual basis. Interest expense is incurred on outstanding balances on the Company’s credit facilities. Interest expense is also incurred on fixed income securities sold, not yet purchased, that the Company holds in its market-marking businesses. Interest expense is also incurred from collateralized transactions, including securities loaned and securities sold under agreements to repurchase
Compensation and Benefits, Policy [Policy Text Block]	Compensation and Benefits Compensation and benefits consists primarily of salaries, incentive compensation, variable compensation, including commissions, related payroll taxes and employee benefits. The Company classifies employees as either risk management consultants / traders, operational or administrative personnel, which includes the executive officers. Variable compensation paid to risk management consultants and traders generally represents a fixed percentage of revenues generated, and in some cases, revenues produced less direct costs and an overhead allocation. The Company accrues commission expense on a trade-date basis.
Share-based Compensation Policy [Policy Text Block]	Share-Based Compensation The Company accounts for share-based compensation in accordance with the guidance in ASC 718-10, Compensation - Stock Compensation. The cost of employee services received in exchange for a share-based award is generally measured based on the grant-date fair value of the award. Share-based employee awards that require future service are amortized over the relevant service period. Forfeitures are accounted for as they occur in determining share-based employee compensation expense. For option awards granted, compensation cost is recognized on a straight-line basis over the vesting period for the entire award.
Transaction-Based Clearing Expenses, Policy [Policy Text Block]	Transaction-Based Clearing Expenses Clearing fees and related expenses include primarily variable expenses for clearing and settlement services, including fees the Company pays to executing brokers, exchanges, clearing organizations and banks. These fees are based on transaction volume, and recorded as expense on the trade date. Clearing fees are passed on to clients and are presented gross in the consolidated statements of income as the Company acts as a principal for these transactions.
Introducing Broker Commissions, Policy [Policy Text Block]	Introducing Broker Commissions Introducing broker commissions include commissions paid to non-employee third parties that have introduced clients to the Company. Introducing brokers are individuals or organizations that maintain relationships with clients and accept futures and options orders from those clients. The Company directly provides all account, transaction and margining services to introducing brokers, including accepting money, securities and property from the clients. The commissions are determined and settled monthly.
Income Tax, Policy [Policy Text Block]	Income Taxes Income tax expense includes U.S. federal, state and local and foreign income taxes. Certain items of income and expense are not reported in tax returns and financial statements in the same year. The objectives of accounting for income taxes are to recognize the amount of taxes payable or refundable for the current year. The Company utilizes the asset and liability method to provide income taxes on all transactions recorded in the consolidated financial statements. This method requires that income taxes reflect the expected future tax consequences of temporary differences between the carrying amounts of assets or liabilities for book and tax purposes. Accordingly, a deferred tax asset or liability for each temporary difference is determined based on the tax rates that the Company expects to be in effect when the underlying items of income and expense are realized. Judgment is required in assessing the future tax consequences of events that have been recognized in the Company’s financial statements or tax returns, including the repatriation of undistributed earnings of foreign subsidiaries. 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 recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authority, based upon the technical merits of the position. The tax benefit recognized in the consolidated financial statements from such a position is measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. See Note 19 for further information on the Company’s income taxes.
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income Comprehensive income consists of net income and other gains and losses affecting stockholders’ equity that, under U.S. GAAP, are excluded from net income. Other comprehensive income (loss) includes net actuarial gains and losses from defined benefit pension plans and gains and losses on foreign currency translations.
Preferred Stock [Text Block]	Preferred Stock The Company is authorized to issue one million shares of preferred stock, par value of $0.01 per share, in one or more classes or series to be established by the Company’s board of directors. As of September 30, 2019 and 2018 , no preferred shares were outstanding and the Company’s board of directors had not yet established any class or series of shares.
Recent Accounting Pronouncements, Policy [Policy Text Block]	Accounting Standards Adopted On October 1, 2018, the Company adopted FASB ASC 606, Revenue from Contracts with Customers (“Topic 606”) using the modified retrospective transition method applied to those contracts which were not completed as of October 1, 2018. Results for reporting periods beginning after October 1, 2018, are presented under Topic 606, and amounts prior to October 1, 2018 are not adjusted and continue to be reported in accordance with historical accounting standard, FASB ASC 605, Revenue Recognition (“Topic 605”). The adoption of Topic 606 had no impact to retained earnings as of October 1, 2018, or to revenue for the year ended September 30, 2019 . The Company’s accounting for revenues within the scope of Topic 606 are materially consistent with those accounting principles and practices applied to accounting for revenues under Topic 605. The new revenue recognition model does not apply to revenues associated with financial instruments or contracts, including derivatives and interest income. For further information refer to Note 2 . In August 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-15, Statements of Cash Flows: Classification of Certain Cash Receipts and Cash Payments, which clarifies how companies present and classify certain cash receipts and cash payments in the statement of cash flows. The Company adopted ASU 2016-15 on October 1, 2018 and the adoption of this ASU had no impact on its consolidated financial statements and related disclosures. On October 1, 2018, the Company adopted FASB ASU 2016-18, Statements of Cash Flows: Classification and Presentation of Restricted Cash in the Statements of Cash Flows, using the retrospective transition method. In accordance with the provisions of ASU 2016-18, the Company changed its consolidated statements of cash flows presentation convention to explain the changes in cash and cash equivalents, as well as cash and cash equivalents segregated for regulatory purposes. U.S. Treasury obligations with original or acquired maturities of 90 days or less held with third-party banks or pledged to clearing-exchanges representing investments of segregated client funds, or which are held for particular clients in lieu of cash margin, are included in segregated cash equivalents. Purchases, sales, as well as client pledges and redemptions in lieu of cash margin, of U.S. Treasury obligations with original or acquired maturities of greater than 90 days representing investments of segregated client funds are presented as operating uses and sources of cash, respectively, within the operating section of the consolidated statements of cash flows. In May 2017, the FASB issued ASU No. 2017- 09, Scope of Modification Accounting, which amends the scope of modification accounting for share- based payment arrangements. ASU 2017- 09 provides guidance on the types of changes to the terms or conditions of share- based payment awards to which an entity would be required to apply modification accounting under ASC 718. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. The Company adopted ASU 2017- 09 on October 1, 2018. The adoption of the ASU had no impact on the Company's consolidated financial statements and related disclosures.

Revenues from contracts with _2

Revenues from contracts with customers (Tables)	12 Months Ended
	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue [Table Text Block]	Year Ended September 30, 2019 2018 2017 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 144.9 $ 163.4 $ 129.7 OTC derivative brokerage 32.1 30.3 28.3 Equities and fixed income 16.1 11.2 16.0 Mutual funds 7.5 7.2 7.9 Insurance and annuity products 7.3 5.8 6.0 Other 1.3 0.9 2.0 Total sales-based commission 209.2 218.8 189.9 Trailing: Mutual funds 12.4 13.2 13.1 Insurance and annuity products 14.4 14.6 14.2 Total trailing commission 26.8 27.8 27.3 Clearing fees 118.8 123.3 88.5 Trade conversion fees 7.5 6.8 — Other 10.1 15.1 12.9 Total commission and clearing fees: 372.4 391.8 318.6 Consulting, management, and account fees: Underwriting fees 0.7 1.7 2.3 Asset management fees 26.2 24.8 25.7 Advisory and consulting fees 20.0 19.0 17.7 Sweep program fees 16.3 11.6 6.0 Client account fees 10.6 11.1 10.8 Other 5.8 2.9 2.5 Total consulting, management, and account fees 79.6 71.1 65.0 Total revenues from contracts with clients $ 452.0 $ 462.9 $ 383.6 Method of revenue recognition: Point-in-time $ 362.7 $ 379.7 $ 306.9 Time elapsed 89.3 83.2 76.7 Total revenues from contracts with clients 452.0 462.9 383.6 Other sources of revenues Physical precious metals trading 30,694.5 25,762.9 28,018.4 Physical agricultural and energy product trading 1,135.8 919.5 654.9 Principal gains, net 415.8 354.1 297.0 Interest income 198.9 123.3 69.7 Total revenues $ 32,897.0 $ 27,622.7 $ 29,423.6

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block]	The following is a reconciliation of the numerator and denominator of the diluted net income per share computations for the periods presented below. Year Ended September 30, (in millions, except share amounts) 2019 2018 2017 Numerator: Net income $ 85.1 $ 55.5 $ 6.4 Less: Allocation to participating securities (1.5 ) (0.9 ) (0.1 ) Net income allocated to common stockholders $ 83.6 $ 54.6 $ 6.3 Denominator: Weighted average number of: Common shares outstanding 18,738,905 18,549,011 18,395,987 Dilutive potential common shares outstanding: Share-based awards 275,490 385,819 291,367 Diluted shares outstanding 19,014,395 18,934,830 18,687,354

Assets and Liabilities, at Fa_2

Assets and Liabilities, at Fair Value (Tables)	12 Months Ended
	Sep. 30, 2019
Assets and Liabilities, at Fair Value [Abstract]
Fair Value, Assets 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 September 30, 2019 and September 30, 2018 by level in the fair value hierarchy. Except as disclosed in Note 7 , there were no assets or liabilities that were measured at fair value on a nonrecurring basis as of September 30, 2019 and 2018 . September 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 4.9 $ — $ — $ — $ 4.9 Money market mutual funds 8.9 — — — 8.9 Cash and cash equivalents 13.8 — — — 13.8 Commodities warehouse receipts 6.2 — — — 6.2 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 306.0 — — — 306.0 U.S. Treasury obligations 593.9 — — — 593.9 "To be announced" (TBA) and forward settling securities — 9.8 — (1.5 ) 8.3 Foreign government obligations 9.9 — — — 9.9 Derivatives 3,131.2 43.2 — (3,159.6 ) 14.8 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,735.0 53.0 — (3,161.1 ) 626.9 Equity securities 159.5 9.0 — — 168.5 Corporate and municipal bonds — 80.0 — — 80.0 U.S. Treasury obligations 248.7 — — — 248.7 U.S. government agency obligations — 447.1 — — 447.1 Foreign government obligations 0.5 — — — 0.5 Agency mortgage-backed obligations — 1,045.0 — — 1,045.0 Asset-backed obligations — 29.1 — — 29.1 Derivatives 1.0 486.3 — (420.8 ) 66.5 Commodities leases — 28.6 — — 28.6 Commodities warehouse receipts 48.4 — — — 48.4 Exchange firm common stock 12.7 — — — 12.7 Mutual funds and other 0.1 — — — 0.1 Financial instruments owned 470.9 2,125.1 — (420.8 ) 2,175.2 Physical commodities inventory 7.1 144.8 — — 151.9 Total assets at fair value $ 4,532.8 $ 2,322.9 $ — $ (3,581.9 ) $ 3,273.8 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.8 $ — $ 1.8 TBA and forward settling securities — 6.8 — (1.5 ) 5.3 Derivatives 3,079.1 38.3 — (3,117.1 ) 0.3 Payable to broker-dealers, clearing organizations and counterparties 3,079.1 45.1 — (3,118.6 ) 5.6 Equity securities 147.3 10.8 — — 158.1 Foreign government obligations — — — — — Corporate and municipal bonds — 39.2 — — 39.2 U.S. Treasury obligations 272.3 — — — 272.3 U.S. government agency obligations — 43.8 — — 43.8 Agency mortgage-backed obligations — 29.6 — — 29.6 Derivatives 480.3 — (422.2 ) 58.1 Commodities leases $ — $ 113.7 $ — $ — $ 113.7 Financial instruments sold, not yet purchased 419.6 717.4 — (422.2 ) 714.8 Total liabilities at fair value $ 3,498.7 $ 762.5 $ 1.8 $ (3,540.8 ) $ 722.2 (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 are included in that level. September 30, 2018 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Cash and cash equivalents - certificaes of deposit $ 3.8 $ — $ — $ — $ 3.8 Commodities warehouse receipts 42.9 — — — 42.9 U.S. Treasury obligations 600.4 — — — 600.4 Securities and other assets segregated under federal and other regulations 643.3 — — — 643.3 U.S. Treasury obligations 778.4 — — — 778.4 TBA and forward settling securities — 5.0 — (2.1 ) 2.9 Foreign government obligations 7.7 — — — 7.7 Derivatives 7,495.9 19.6 — (7,787.1 ) (271.6 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 8,282.0 24.6 — (7,789.2 ) 517.4 Equity securities 71.2 3.0 — — 74.2 Corporate and municipal bonds — 79.1 — — 79.1 U.S. Treasury obligations 120.1 — — — 120.1 U.S. government agency obligations — 472.9 — — 472.9 Foreign government obligations 6.4 — — — 6.4 Agency mortgage-backed obligations — 1,022.5 — — 1,022.5 Asset-backed obligations — 42.9 — — 42.9 Derivatives 0.8 514.6 — (329.3 ) 186.1 Commodities leases — 29.5 — (11.8 ) 17.7 Commodities warehouse receipts 16.4 — — — 16.4 Exchange firm common stock 10.2 — — — 10.2 Mutual funds and other 6.3 — — — 6.3 Financial instruments owned 231.4 2,164.5 — (341.1 ) 2,054.8 Physical commodities inventory 42.1 114.8 — — 156.9 Total assets at fair value $ 9,202.6 $ 2,303.9 $ — $ (8,130.3 ) $ 3,376.2 Liabilities: TBA and forward settling securities $ — $ 2.1 $ — $ (2.1 ) $ — Derivatives 7,809.3 11.6 — (7,820.9 ) — Payable to broker-dealers, clearing organizations and counterparties 7,809.3 13.7 — (7,823.0 ) — Equity securities 51.1 0.4 — — 51.5 Corporate and municipal bonds — 20.1 — — 20.1 U.S. Treasury obligations 484.8 — — — 484.8 U.S. government agency obligations — 57.2 — — 57.2 Agency mortgage-backed obligations — 0.2 — — 0.2 Derivatives 688.0 — (494.6 ) 193.4 Commodities leases — 75.5 — (16.2 ) 59.3 Financial instruments sold, not yet purchased 535.9 841.4 — (510.8 ) 866.5 Total liabilities at fair value $ 8,345.2 $ 855.1 $ — $ (8,333.8 ) $ 866.5 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	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 years ended September 30, 2019 and 2018 , including a summary of unrealized gains (losses) during the fiscal year ended on the Company’s Level 3 financial assets and liabilities held during the periods. Level 3 Financial Liabilities (in millions) Balances at Realized (gains) Remeasurement Acquisitions Settlements Transfers in Balances at Liabilities: Contingent liabilities $ — $ — $ — $ 1.8 $ — $ — $ 1.8 Level 3 Financial Assets and Financial Liabilities (in millions) Balances at Realized gains Unrealized Purchases/ Settlements Transfers in Balances at Assets: Equity securities $ 0.1 $ — $ (0.1 ) $ — $ — $ — $ — (in millions) Balances at Realized (gains) Remeasurement Acquisitions Settlements Transfers in Balances at Liabilities: Contingent liabilities $ 1.0 $ — $ — $ — $ (1.0 ) $ — $ —

Financial Instruments with Of_2

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	12 Months Ended
	Sep. 30, 2019
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Schedule of Derivative Instruments Included in Trading Activities [Table Text Block]	As of September 30, 2019 and 2018 , TBA and forward settling securities recorded within deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties are summarized as follows (in millions): September 30, 2019 September 30, 2018 Gain/(Loss) Notional Amounts Gain/(Loss) Notional Amounts Unrealized gain on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 3.7 $ 1,778.4 $ 1.2 $ 721.5 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.6 ) $ 234.5 $ (0.6 ) $ 293.2 Unrealized gain on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ 3.2 $ (1,099.5 ) Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ 0.9 $ (451.6 ) $ — $ — Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (5.9 ) $ (2,788.0 ) $ — $ — Unrealized loss on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ (1.5 ) $ (812.7 ) Unrealized gain on forward settling securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ 0.5 $ 614.3 Unrealized loss on forward settling securities purchased within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (0.3 ) $ 1,243.5 $ — $ — Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties and related notional amounts $ 5.2 $ (581.2 ) $ 0.1 $ (427.2 ) The notional amounts of these instruments reflect the extent of the Company’s involvement in TBA and forward settling securities and do not represent counterparty exposure.
Schedule of Derivative Instruments [Table Text Block]	Listed below are the fair values of the Company’s derivative assets and liabilities as of September 30, 2019 and 2018 . Assets represent net unrealized gains and liabilities represent net unrealized losses. September 30, 2019 September 30, 2018 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,437.1 $ 1,463.4 $ 2,455.7 $ 2,499.3 OTC commodity derivatives 84.2 106.2 207.0 369.9 Exchange-traded foreign exchange derivatives 36.9 33.5 49.8 37.2 OTC foreign exchange derivatives 403.2 368.8 302.5 303.9 Exchange-traded interest rate derivatives 900.1 882.0 449.3 478.7 OTC interest rate derivatives 42.1 43.6 24.8 25.9 Exchange-traded equity index derivatives 758.1 700.2 4,541.8 4,794.0 TBA and forward settling securities 9.8 6.8 5.0 2.1 Gross fair value of derivative contracts 3,671.5 3,604.5 8,035.9 8,511.0 Impact of netting and collateral (3,581.9 ) (3,540.8 ) (8,118.5 ) (8,317.6 ) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties' $ 23.1 $ (268.7 ) Total fair value included in 'Financial instruments owned, at fair value $ 66.5 $ 186.1 Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties $ 5.6 $ — Fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 58.1 $ 193.4 (1) As of September 30, 2019 and 2018 , the Company’s derivative contract volume for open positions was approximately 10.6 million contracts
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block]	The following table sets forth the Company’s net gains (losses) related to derivative financial instruments for the fiscal years ended September 30, 2019, 2018, and 2017 , in accordance with the Derivatives and Hedging Topic of the ASC. The net gains (losses) set forth below are included in ‘principal gains, net’ and ‘cost of sales of physical commodities’ in the consolidated income statements. Year Ended September 30, (in millions) 2019 2018 2017 Commodities $ 100.8 $ 94.0 $ 47.3 Foreign exchange 8.1 9.2 8.7 Interest rate and equity (2.6 ) 1.0 (0.1 ) TBA and forward settling securities (35.3 ) 14.5 (2.5 ) Net gains from derivative contracts $ 71.0 $ 118.7 $ 53.4

Receivables from customers, n_2

Receivables from customers, net and notes receivable, net (Tables)	12 Months Ended
	Sep. 30, 2019
Receivables from customers and notes receivable, net [Abstract]
Allowance for Doubtful Accounts and Notes Receivables [Table Text Block]	Activity in the allowance for doubtful accounts for the fiscal years ended September 30, 2019, 2018, and 2017 was as follows: (in millions) 2019 2018 2017 Balance, beginning of year $ 58.2 $ 54.6 $ 9.7 (Recovery) provision for bad debts (9.8 ) 3.9 51.0 Allowance charge-offs (1.3 ) (0.3 ) (6.1 ) Other (1) 1.5 — — Balance, end of year $ 48.6 $ 58.2 $ 54.6 (1) Allowance increase is related to a recoverable amount due from an affiliated party and recorded in ‘other assets’ on the consolidated balance sheets.

Physical Commodities Inventor_2

Physical Commodities Inventory Physical Commodities Inventory (Tables)	12 Months Ended
	Sep. 30, 2019
Inventory [Line Items]
Schedule of Inventory, Current [Table Text Block]	(in millions) September 30, September 30, Physical Ag & Energy (1) $ 144.8 $ 114.7 Precious metals - held by broker-dealer subsidiary (2) 7.1 42.1 Precious metals - held by non-broker-dealer subsidiaries (3) 77.4 65.7 Physical commodities inventory $ 229.3 $ 222.5

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Sep. 30, 2019
Property and Equipment, net [Abstract]
Property, Plant and Equipment [Table Text Block]	A summary of property and equipment, at cost less accumulated depreciation as of September 30, 2019 and 2018 is as follows: (in millions) September 30, 2019 September 30, 2018 Property and equipment: Furniture and fixtures $ 10.6 $ 8.7 Software 33.9 30.5 Equipment 28.1 24.7 Leasehold improvements 20.3 17.0 Total property and equipment 92.9 80.9 Less accumulated depreciation (49.0 ) (38.5 ) Property and equipment, net $ 43.9 $ 42.4

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Sep. 30, 2019
Goodwill [Abstract]
Schedule of Goodwill [Table Text Block]	Goodwill allocated to the Company’s operating segments as of September 30, 2019 and 2018 is as follows: (in millions) September 30, September 30, Commerical Hedging $ 30.3 $ 30.3 Global Payments 7.6 8.9 Physical Commodities 4.6 2.4 Securities 8.7 6.8 Goodwill $ 51.2 $ 48.4

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2019
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): September 30, 2019 September 30, 2018 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Intangible assets subject to amortization: Software programs/platforms $ 5.3 $ (3.0 ) $ 2.3 $ 2.7 $ (2.6 ) $ 0.1 Client base 22.1 (12.5 ) 9.6 21.4 (10.1 ) 11.3 Total intangible assets subject to amortization 27.4 (15.5 ) 11.9 24.1 (12.7 ) 11.4 Intangible assets not subject to amortization: Website domains 2.1 — 2.1 — — — Business licenses 2.7 — 2.7 — — — Total intangible assets not subject to amortization 4.8 — 4.8 — — — Total intangible assets $ 32.2 $ (15.5 ) $ 16.7 $ 24.1 $ (12.7 ) $ 11.4
Schedule of Expected Amortization Expense [Table Text Block]	(in millions) Fiscal 2020 $ 2.9 Fiscal 2021 2.9 Fiscal 2022 1.6 Fiscal 2023 1.4 Fiscal 2024 and thereafter 3.1 $ 11.9

Credit Facilities (Tables)

Credit Facilities (Tables)	12 Months Ended
	Sep. 30, 2019
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, and outstanding borrowings on the facilities as well as indebtedness on a promissory note as of the periods indicated: (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment September 30, September 30, Committed Credit Facilities Term Loan (1) February 22, 2022 $ 189.9 $ 167.6 (2) $ — Revolving Line of Credit (1) February 22, 2022 196.5 70.0 208.2 INTL FCStone Inc. 386.4 237.6 208.2 INTL FCStone Financial, Inc. None April 3, 2020 75.0 — — FCStone Merchants Services, LLC Certain commodities assets February 1, 2020 232.5 128.5 128.0 INTL FCStone Ltd. None January 31, 2020 50.0 — — $ 743.9 $ 366.1 $ 336.2 Uncommitted Credit Facilities INTL FCStone Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a — 14.0 INTL FCStone Ltd. Commodities warehouse receipts n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a 3.4 3.8 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 0.4 1.2 Total outstanding borrowings $ 369.9 $ 355.2 (1) The INTL FCStone Inc. committed credit facility is secured by substantially all of the assets of INTL FCStone Inc. and certain subsidiaries identified in the credit facility agreement as obligors, and pledged equity of certain subsidiaries identified in the credit facility as limited guarantors.

Commitments and Contingencies F

Commitments and Contingencies Future Minimum Lease Commitments (Tables)	12 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Future aggregate minimum lease payments under noncancelable operating leases as of September 30, 2019 are as follows: (in millions) Year ending September 30, 2020 $ 11.2 2021 9.9 2022 7.5 2023 6.2 2024 5.8 Thereafter 2.6 $ 43.2

Regulatory Requirements and S_2

Regulatory Requirements and Subsidiary Dividend Restrictions (Tables)	12 Months Ended
	Sep. 30, 2019
Capital and Other Regulatory Requirements [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]	with a minimum net capital requirement in excess of $5.0 million as well as the actual regulatory capital of the subsidiary as of September 30, 2019 (in millions): Subsidiary Regulatory Authority Actual Minimum Requirement INTL FCStone Financial Inc. SEC and CFTC $ 170.1 $ 97.5 INTL FCStone Ltd FCA $ 231.7 $ 123.3

Commodity and Other Repurchas_2

Commodity and Other Repurchase Agreements Gross Obligations Contractual Maturities (Tables)	12 Months Ended
	Sep. 30, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets [Table Text Block]	September 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 1,553.9 $ 565.8 $ 654.0 $ 2,773.7 Securities loaned 1459.9 — — 1,459.9 Gross amount of secured financing $ 3,013.8 $ 565.8 $ 654.0 $ 4,233.6 September 30, 2018 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 934.9 $ 661.3 $ 340.5 $ 1,936.7 Securities loaned 277.9 — — 277.9 Gross amount of secured financing $ 1,212.8 $ 661.3 $ 340.5 $ 2,214.6

Commodity and Other Repurchas_3

Commodity and Other Repurchase Agreements Gross Obligations Collateral Types (Tables)	12 Months Ended
	Sep. 30, 2019
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 September 30, 2019 September 30, 2018 U.S. Treasury obligations $ 108.8 $ 39.6 U.S. government agency obligations 359.5 461.7 Asset-backed obligations 96.7 50.0 Agency mortgage-backed obligations 2,208.7 1,385.4 Total securities sold under agreement to repurchase $ 2,773.7 $ 1,936.7 Securities loaned Equity securities 1,459.9 277.9 Total securities loaned 1,459.9 277.9 Gross amount of secured financing $ 4,233.6 $ 2,214.6

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions: Year ended September 30, 2019 2019 2018 2017 Expected stock price volatility 27 % 30 % 31 % Expected dividend yield — % — % — % Risk free interest rate 1.86 % 1.23 % 0.99 % Average expected life (in years) 6.05 3.06 3.08
Share-based Compensation, Stock Options, Activity [Table Text Block]	The following is a summary of stock option activity for the year ended September 30, 2019 : Shares Available for Grant Number of Options Outstanding Weighted Average Exercise Price Weighted Average Grant Date Fair Value Weighted Average Remaining Term (in years) Aggregate Intrinsic Value ($ millions) Balances at September 30, 2018 588,020 835,454 $ 29.27 $ 11.93 3.01 $ 15.9 Additional shares authorized by shareholders 1,000,000 Granted (922,000 ) 922,000 $ 44.31 $ 10.47 Exercised (46,444 ) $ 25.04 $ 5.21 Forfeited 25,048 (25,048 ) $ 31.31 $ 11.91 Expired 1,584 (1,584 ) $ 33.83 $ 7.46 Balances at September 30, 2019 692,652 1,684,378 $ 37.59 $ 11.32 4.62 $ 9.2 Exercisable at September 30, 2019 472,424 $ 28.96 $ 12.27 2.08 $ 5.8
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]	The options outstanding as of September 30, 2019 broken down by exercise price are as follows: Exercise Price Number of Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Term $ — - $ 5.00 — n/a n/a $ 5.00 - $ 10.00 — n/a n/a $ 10.00 - $ 15.00 — n/a n/a $ 15.00 - $ 20.00 — n/a n/a $ 20.00 - $ 25.00 — n/a n/a $ 25.00 - $ 30.00 564,000 $ 25.91 2.37 $ 30.00 - $ 35.00 32,881 $ 31.37 0.28 $ 35.00 - $ 40.00 213,830 $ 39.33 2.43 $ 40.00 - $ 45.00 871,667 $ 44.91 6.78 $ 45.00 - $ 50.00 — n/a n/a $ 50.00 - $ 55.00 — n/a n/a $ 55.00 - $ 60.00 2,000 $ 55.28 2.89 1,684,378 $ 37.59 4.62
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]	The following is a summary of restricted stock activity through September 30, 2019 : Shares Available for Grant Number of Shares Outstanding Weighted Average Grant Date Fair Value Weighted Average Remaining Term (in years) Aggregate Intrinsic Value ($ millions) Balances at September 30, 2018 1,377,278 274,628 $ 38.20 1.15 $ 13.3 Granted (223,481 ) 223,481 $ 39.57 Vested — (144,226 ) $ 35.85 Forfeited 3,105 (3,105 ) $ 35.62 Balances at September 30, 2019 1,156,902 350,778 $ 40.06 1.36 $ 14.4

Other Expenses (Tables)

Other Expenses (Tables)	12 Months Ended
	Sep. 30, 2019
Other Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Other expenses for the years ended September 30, 2019, 2018, and 2017 are comprised of the following: Year Ended September 30, (in millions) 2019 2018 2017 Insurance $ 3.4 $ 2.6 $ 2.7 Advertising, meetings and conferences 5.2 6.2 4.0 Office supplies and printing 1.9 1.7 2.1 Other clearing related expenses 2.5 2.5 2.6 Other non-income taxes 4.6 4.9 4.6 Contingent consideration, net — — 0.1 Other 10.8 8.4 9.8 Total other expenses $ 28.4 $ 26.3 $ 25.9

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Income tax expense (benefit) for the years ended September 30, 2019, 2018, and 2017 was allocated as follows: Year Ended September 30, (in millions) 2019 2018 2017 Income tax expense attributable to income from operations $ 25.9 $ 46.0 $ 8.8 Taxes allocated to stockholders’ equity, related to pension liabilities (0.2 ) 0.1 1.0 Taxes allocated to additional paid-in capital, related to share-based compensation — — 0.1 Total income tax expense $ 25.7 $ 46.1 $ 9.9 The components of income tax expense (benefit) attributable to income from operations were as follows: Year Ended September 30, (in millions) 2019 2018 2017 Current taxes: U.S. federal $ (1.9 ) $ 0.8 $ 0.7 U.S. State and local (0.8 ) 0.5 1.2 International 24.9 22.4 16.7 Total current taxes 22.2 23.7 18.6 Deferred taxes 3.7 22.3 (9.8 ) Income tax expense $ 25.9 $ 46.0 $ 8.8
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	U.S. and international components of (loss) income from operations, before tax, was as follows: Year Ended September 30, (in millions) 2019 2018 2017 U.S. $ (2.6 ) $ 9.9 $ (13.9 ) International 113.6 91.6 29.1 Income from operations, before tax $ 111.0 $ 101.5 $ 15.2
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Items accounting for the difference between income taxes computed at the federal statutory rate and income tax expense were as follows: Year Ended September 30, 2019 2018 2017 Federal statutory rate effect of: 21.0 % 24.5 % 35.0 % U.S. State and local income taxes (1.5 )% 0.8 % (2.6 )% Foreign earnings and losses taxed at different rates 0.7 % (0.8 )% 11.5 % Change in foreign valuation allowance 1.0 % (0.8 )% (1.4 )% Change in state valuation allowance 0.5 % — % 4.1 % U.S. permanent items 0.1 % (0.2 )% 3.6 % Foreign permanent items 0.7 % 2.1 % 8.1 % U.S. bargain purchase gain (1.0 )% — % — % Remeasurement of deferred tax — % 8.5 % — % Repatriation Transition tax — % 11.0 % — % GILTI 2.2 % — % — % Other reconciling items (0.4 )% 0.2 % (0.6 )% Effective rate 23.3 % 45.3 % 57.7 %
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The components of deferred income tax assets and liabilities were as follows: (in millions) September 30, 2019 September 30, 2018 Deferred tax assets: Share-based compensation $ 3.3 $ 2.8 Deferred compensation 3.6 1.4 Foreign net operating loss carryforwards 2.6 4.2 U.S. State and local net operating loss carryforwards 9.2 8.7 U.S. federal net operating loss carryforwards 1.1 — Intangible assets 4.8 1.8 Bad debt reserve 1.3 1.5 Tax credit carryforwards 0.5 — Foreign tax credit carryforwards 5.0 6.5 Other compensation 2.2 3.4 Other 1.1 0.9 Total gross deferred tax assets 34.7 31.2 Less valuation allowance (8.5 ) (3.5 ) Deferred tax assets 26.2 27.7 Deferred income tax liabilities: Unrealized gain on securities 3.2 2.6 Prepaid expenses 2.2 1.8 Property and equipment 2.6 3.1 Pension liability 0.2 0.4 Deferred income tax liabilities 8.2 7.9 Deferred income taxes, net $ 18.0 $ 19.8
Summary of Income Tax Contingencies [Table Text Block]	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: Year Ended September 30, (in millions) 2019 2018 2017 Balance, beginning of year $ 0.1 $ 0.1 $ 0.1 Gross decreases for tax positions of prior years (0.1 ) — — Balance, end of year $ — $ 0.1 $ 0.1

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Sep. 30, 2019
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) income for the year ended September 30, 2019 . (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2018 $ (30.5 ) $ (2.6 ) $ (33.1 ) Other comprehensive (loss) income, net of tax before reclassifications (0.8 ) (0.8 ) (1.6 ) Amounts reclassified from AOCI, net of tax (0.2 ) 0.1 (0.1 ) Other comprehensive (loss) income, net of tax (1.0 ) (0.7 ) (1.7 ) Balances as of September 30, 2019 $ (31.5 ) $ (3.3 ) $ (34.8 )

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Sep. 30, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Table Text Block]	The Company has set forth certain quarterly unaudited financial data for the past two years in the tables below: For the 2019 Fiscal Quarter Ended (in millions, except per share amounts) September 30 (1) June 30 March 31 December 31 Total revenues $ 11,279.6 $ 7,873.0 $ 7,192.2 $ 6,552.2 Cost of sales of physical commodities 10,992.7 7,589.6 6,921.1 6,287.5 Operating revenues 286.9 283.4 271.1 264.7 Transaction-based clearing expenses 45.0 45.7 42.7 50.1 Introducing broker commissions 27.7 29.6 24.8 32.6 Interest expense 40.8 42.5 38.4 33.0 Net operating revenues 173.4 165.6 165.2 149.0 Compensation and benefits 105.2 100.9 97.9 89.1 Bad debts 1.0 0.5 0.7 0.3 Bad debt on physical coal (1) (10.0 ) — — (2.4 ) Other expenses 43.2 42.6 41.1 37.6 Total compensation and other expenses 139.4 144.0 139.7 124.6 Other gains (2) 0.1 — 5.4 — Income before tax 34.1 21.6 30.9 24.4 Income tax expense 6.9 5.3 7.5 6.2 Net income $ 27.2 $ 16.3 $ 23.4 $ 18.2 Net basic earnings per share $ 1.42 $ 0.85 $ 1.23 $ 0.96 Net diluted earnings per share $ 1.40 $ 0.84 $ 1.21 $ 0.94 For the 2018 Fiscal Quarter Ended (in millions, except per share amounts) September 30, June 30, March 31, December 31, Total revenues $ 6,078.8 $ 7,118.3 $ 6,507.0 $ 7,918.6 Cost of sales of physical commodities 5,835.6 6,858.5 6,246.8 7,706.0 Operating revenues 243.2 259.8 260.2 212.6 Transaction-based clearing expenses 43.1 49.0 50.7 36.9 Introducing broker commissions 32.4 34.1 36.2 31.1 Interest expense 25.3 22.1 19.0 14.3 Net operating revenues 142.4 154.6 154.3 130.3 Compensation and benefits 85.4 86.9 88.2 77.2 Bad debts 1.2 1.6 0.2 0.1 Bad debt on physical coal (1) — — — 1.0 Other expenses 35.3 35.2 36.4 33.4 Total compensation and other expenses 121.9 123.7 124.8 111.7 Other gains (2) — 2.0 — — Income before tax 20.5 32.9 29.5 18.6 Income tax expense 4.8 8.9 6.8 25.5 Net income (loss) $ 15.7 $ 24.0 $ 22.7 $ (6.9 ) Net basic (loss) earnings per share $ 0.83 $ 1.27 $ 1.20 $ (0.37 ) Net diluted (loss) earnings per share $ 0.81 $ 1.25 $ 1.18 $ (0.37 )

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	12 Months Ended
	Sep. 30, 2019
Segment Analysis [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	(in millions) As of September 30, 2019 As of September 30, 2018 As of September 30, 2017 Total assets: Commercial Hedging $ 2,041.0 $ 1,935.7 $ 1,650.3 Global Payments 278.3 206.6 199.5 Securities 5,219.1 3,058.2 2,101.7 Physical Commodities 357.8 413.7 339.5 Clearing and Execution Services 1,892.1 2,109.9 1,818.9 Corporate unallocated 147.8 100.6 133.5 Total $ 9,936.1 $ 7,824.7 $ 6,243.4
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	Information regarding revenues and operating revenues for the years ended September 30, 2019, 2018, and 2017 , and information regarding long-lived assets (defined as property, equipment, leasehold improvements and software) as of September 30, 2019, 2018, and 2017 in geographic areas were as follows: Year Ended September 30, (in millions) 2019 2018 2017 Total revenues: United States $ 1,947.6 $ 1,587.6 $ 1,168.0 Europe 280.2 189.6 166.9 South America 56.5 59.5 53.9 Middle East and Asia 30,606.9 25,781.4 28,030.3 Other 5.8 4.6 4.5 Total $ 32,897.0 $ 27,622.7 $ 29,423.6 Operating revenues: United States $ 799.4 $ 695.3 $ 529.4 Europe 209.6 189.0 166.9 South America 56.5 58.0 54.0 Middle East and Asia 34.8 28.9 29.2 Other 5.8 4.6 4.5 Total $ 1,106.1 $ 975.8 $ 784.0 (in millions) As of September 30, 2019 As of September 30, 2018 As of September 30, 2017 Long-lived assets, as defined: United States $ 33.9 $ 33.0 $ 29.7 Europe 6.6 6.8 7.3 South America 2.1 1.4 1.5 Middle East and Asia 1.0 1.2 0.2 Other 0.3 — — Total $ 43.9 $ 42.4 $ 38.7

Reconciliation of Cash, Segrega

Reconciliation of Cash, Segregated Cash, Cash Equivalents, and Segregated Cash Equivalents (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Cash and cash equivalents	$ 471.3	$ 342.3
Cash, segregated cash, cash equivalents, and segregated cash equivalents shown in the consolidated statements of cash flows	2,451.3	2,287.6	$ 2,659.8	$ 1,637.6
Cash and Cash Equivalents [Member]
Cash and cash equivalents	471.3	342.3	314.9
Cash segregated under federal and other regulations [Member]
Cash segregated under federal and other regulations (1)	743.9	765.5	463.4
Deposits with and receivables from broker dealers, clearing organizations, and counterparties [Member]
Cash segregated and deposited with or pledged to exchange-clearing organizations and other futures commission merchants (“FCMs”)(2)	947.4	711.9	1,870.9
Securities segregated and pledged to exchange-clearing organizations(2)	$ 288.7	$ 467.9	$ 10.6

Description of Business and S_3

Description of Business and Significant Accounting Policies - Accounts, Customers and Other Facts (Details) $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Number of different types of foreign currencies	140
Number of commercial and institutional clients	20,000
Number retail clients	80,000
Number of Countries in which Entity Operates	130
Non-Trading Technology and Support [Member]
Prior Period Reclassification Adjustment			$ 11.6
communications [Member]
Prior Period Reclassification Adjustment			5
Commission and Clearing Fees
Prior Period Reclassification Adjustment		$ 35	$ 35.2
Exchange memberships not representing an ownership interest [Member]
Memberships in Exchanges Owned	$ 5.8
Exchange memberships representing an ownership interest [Member]
Memberships in Exchanges Owned	$ 5.6

Description of Business and S_4

Description of Business and Significant Accounting Policies - Cash, Cash Equivalents, Securities (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Accounting Policies [Abstract]
Cash Held at Banks and Money Market Funds - Segregated	$ 743,900,000	$ 765,400,000
US Government Obligations and other securities	299,800,000	600,400,000
Commodities Warehouse Receipts	6,200,000	42,900,000
Cash and Cash Equivalents - Deposits and Receivables	1,600,000,000	1,500,000,000
US Government Securities and Other Securities - Deposits and Receivables	$ 603,814,800	$ 800,000,000

Description of Business and S_5

Description of Business and Significant Accounting Policies - Basis of Presentation and Consolidation (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Amount Recognized in Income Due to Inflationary Accounting	$ 3,900,000	$ 3,400,000
Net assets denominated in Argentine Pesos	5,500,000	11,600,000
Cash denominated in Argentine Pesos	100,000	1,400,000
Fair Value of Exchange Memberships	$ 6,000,000	$ 6,400,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Preferred Stock, Shares Outstanding	0	0	0
US Government Securities and Other Securities - Deposits and Receivables	$ 603,814,800	$ 800,000,000
Non-Trading Technology and Support [Member]
Prior Period Reclassification Adjustment			$ 11,600,000
communications [Member]
Prior Period Reclassification Adjustment			$ 5,000,000
Exchange memberships not representing an ownership interest [Member]
Memberships in Exchanges Owned	5,800,000
Exchange memberships representing an ownership interest [Member]
Memberships in Exchanges Owned	$ 5,600,000

Revenues from contracts with _3

Revenues from contracts with customers (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 11,279,600,000	$ 7,873,000,000	$ 7,192,200,000	$ 6,552,200,000	$ 6,078,800,000	$ 7,118,300,000	$ 6,507,000,000	$ 7,918,600,000	$ 32,897,000,000	$ 27,622,700,000	$ 29,423,600,000
Commission and clearing fees									372,400,000	391,800,000	318,600,000
Consulting, management, and account fees									79,600,000	71,100,000	65,000,000
Revenue from Contract with Customer, Including Assessed Tax									452,000,000	462,900,000	383,600,000
Sales of physical commodities									31,830,300,000	26,682,400,000	28,673,300,000
Principal gains, net									415,800,000	354,100,000	297,000,000
Interest income									198,900,000	123,300,000	69,700,000
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									362,700,000	379,700,000	306,900,000
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									89,300,000	83,200,000	76,700,000
Commission and Clearing Fees
Disaggregation of Revenue [Line Items]
Commission and clearing fees									372,400,000	391,800,000	318,600,000
Trailing Commissions [Domain]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									26,800,000	27,800,000	27,300,000
Trailing Commissions [Domain] | Variable Annuity [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									14,400,000	14,600,000	14,200,000
Trailing Commissions [Domain] | Mutual Fund Trailing Commissions [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									12,400,000	13,200,000	13,100,000
Clearing Fees [Domain]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									118,800,000	123,300,000	88,500,000
Trade Conversion Fees [Domain]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									7,500,000	6,800,000	0
Other Commissions [Domain]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									10,100,000	15,100,000	12,900,000
Consulting, management, and account fees [Domain] | Underwriting Fees [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									700,000	1,700,000	2,300,000
Consulting, management, and account fees [Domain] | Asset Management [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									26,200,000	24,800,000	25,700,000
Consulting, management, and account fees [Domain] | Advisory and Consulting Fees [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									20,000,000	19,000,000	17,700,000
Consulting, management, and account fees [Domain] | Sweep Program Fees [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									16,300,000	11,600,000	6,000,000
Consulting, management, and account fees [Domain] | Client Account Fees [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									10,600,000	11,100,000	10,800,000
Consulting, management, and account fees [Domain] | Other Consulting, Management, and Account Fees [Member]
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									5,800,000	2,900,000	2,500,000
Consulting, management, and account fees
Disaggregation of Revenue [Line Items]
Consulting, management, and account fees									79,600,000	71,100,000	65,000,000
Sales [Member] | Precious Metals Trading Revenues [Member]
Disaggregation of Revenue [Line Items]
Sales of physical commodities									30,694,500,000	25,762,900,000	28,018,400,000
Sales [Member] | Physical Commodity Origination and Merchandising [Member]
Disaggregation of Revenue [Line Items]
Sales of physical commodities									1,135,800,000	919,500,000	654,900,000
Principal gains, net
Disaggregation of Revenue [Line Items]
Principal gains, net									415,800,000	354,100,000	297,000,000
Interest Income
Disaggregation of Revenue [Line Items]
Interest income									198,900,000	123,300,000	69,700,000
Sales Based Commissions [Domain]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									209,200,000	218,800,000	189,900,000
Sales Based Commissions [Domain] | Exhange-Traded Futures and Options [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									144,900,000	163,400,000	129,700,000
Sales Based Commissions [Domain] | OTC Derivative Brokerage [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									32,100,000	30,300,000	28,300,000
Sales Based Commissions [Domain] | Equities and Fixed Income Commissions [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									16,100,000	11,200,000	16,000,000
Sales Based Commissions [Domain] | Mutual Fund Sales Based Commissions [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									7,500,000	7,200,000	7,900,000
Sales Based Commissions [Domain] | Variable Annuity [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									7,300,000	5,800,000	6,000,000
Sales Based Commissions [Domain] | Other Sales Based Commissions [Member]
Disaggregation of Revenue [Line Items]
Commission and clearing fees									$ 1,300,000	$ 900,000	$ 2,000,000

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Income from Continuing Operations	$ 85.1	$ 55.5	$ 6.4
Undistributed Earnings Allocated to Participating Securities - Continuing Operations	(1.5)	(0.9)	(0.1)
Income from continuing operations allocated to common shareholders	$ 83.6	$ 54.6	$ 6.3
Weighted Average Number of Shares Outstanding, Basic	18,738,905	18,549,011	18,395,987
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Share-based Awards For Diluted Earnings Per Share Calculation	275,490	385,819	291,367
Diluted weighted-average shares	19,014,395	18,934,830	18,687,354

Earnings per Share - Antiduliti

Earnings per Share - Antidulitive Securities (Details)	12 Months Ended
	Sep. 30, 2017shares
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	230,135

Assets and Liabilities, at Fa_3

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	$ 1,049.9		$ 1,408.7
Receivables from Brokers-Dealers and Clearing Organizations	2,540.5		2,234.5
Financial Instruments, Owned, at Fair Value	2,175.2		2,054.8
Physical Commodities Inventory	229.3		222.5
Accounts payable and other accrued liabilities	157.5		145.4
Payables to Broker-Dealers and Clearing Organizations	(266.2)		(89.5)
Financial Instruments Sold, Not yet Purchased, at Fair Value	714.8		866.5
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	306		643.3
Receivables from Clearing Organizations	626.9		517.4
Financial Instruments, Owned, at Fair Value	2,175.2		2,054.8
Assets, Fair Value Disclosure	3,273.8		3,376.2
Financial Instruments Sold, Not yet Purchased, at Fair Value		$ 714.8
Liabilities, Fair Value Disclosure	722.2		866.5
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	(5.6)		0
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	(5.3)		0
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(0.3)		0
Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	1.8
Fair Value, Measurements, Recurring [Member] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical Commodities Inventory	151.9		156.9
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	168.5		74.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	158.1		51.5
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	29.1		42.9
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	447.1		472.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	43.8		57.2
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	248.7		120.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	272.3		484.8
Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0.5		6.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0.2
Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	1,045		1,022.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	29.6
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	66.5		186.1
Fair Value, Measurements, Recurring [Member] | Commodities leases and unpriced positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	28.6		17.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	113.7		59.3
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	48.4		16.4
Fair Value, Measurements, Recurring [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	12.7		10.2
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	0.1		6.3
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	80		79.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	39.2		20.1
Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	9.9		7.7
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	593.9
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	8.3		2.9
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	14.8
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			778.4
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			(271.6)
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	6.2		42.9
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	299.8		600.4
Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	4.9
Cash and Cash Equivalents, Fair Value Disclosure	13.8		3.8
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	8.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	306		643.3
Receivables from Clearing Organizations	3,735		8,282
Financial Instruments, Owned, at Fair Value	470.9		231.4
Assets, Fair Value Disclosure	4,532.8		9,202.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	419.6		535.9
Liabilities, Fair Value Disclosure	3,498.7		8,345.2
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	(3,079.1)		(7,809.3)
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	(3,079.1)		(7,809.3)
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	7.1		42.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	159.5		71.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	147.3		51.1
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] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	248.7		120.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	272.3		484.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0.5		6.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	1		0.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases and unpriced positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	48.4		16.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	12.7		10.2
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	0.1		6.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | 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] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	9.9		7.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	593.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from 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	3,131.2
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			778.4
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			7,495.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	6.2		42.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	299.8		600.4
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	4.9
Cash and Cash Equivalents, Fair Value Disclosure	13.8		3.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	8.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0		0
Receivables from Clearing Organizations	53		24.6
Financial Instruments, Owned, at Fair Value	2,125.1		2,164.5
Assets, Fair Value Disclosure	2,322.9		2,303.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	717.4		841.4
Liabilities, Fair Value Disclosure	762.5		855.1
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	(45.1)		(13.7)
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	(6.8)		(2.1)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(38.3)		(11.6)
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	144.8		114.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	9		3
Financial Instruments Sold, Not yet Purchased, at Fair Value	10.8		0.4
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	29.1		42.9
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	447.1		472.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	43.8		57.2
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] | Debt Security, Government, Non-US [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		0.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	1,045		1,022.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	29.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	486.3		514.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	480.3		688
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases and unpriced positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	28.6		29.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	113.7		75.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	80		79.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	39.2		20.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	9.8		5
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	43.2
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			19.6
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	0
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	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		0
Assets, Fair Value Disclosure	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Liabilities, Fair Value Disclosure	1.8		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] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	1.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Physical commodities inventory - precious metals [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical Commodities Inventory	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity 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] | 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] | 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] | Debt Security, Government, Non-US [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] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities leases and unpriced positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | 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] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from 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	0
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Receivables from Clearing Organizations	(3,161.1)		(7,789.2)
Financial Instruments, Owned, at Fair Value	(420.8)		(341.1)
Assets, Fair Value Disclosure	(3,581.9)		(8,130.3)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(422.2)		(510.8)
Liabilities, Fair Value Disclosure	(3,540.8)		(8,333.8)
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	3,118.6		7,823
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	1.5		2.1
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	3,117.1		7,820.9
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Equity 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
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [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
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	(420.8)		(329.3)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(422.2)		(494.6)
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Commodities leases and unpriced positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		(11.8)
Financial Instruments Sold, Not yet Purchased, at Fair Value	0		(16.2)
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | 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
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(1.5)
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(3,159.6)
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations			0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations			(2.1)
Counterparty And Cash Collateral Netting Adjustment [Member] | 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			0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations			(7,787.1)
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | 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	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	0
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	0
Financial instrument sold, not yet purchased [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Fair Value, Net	$ 58.1		$ 193.4

Assets and Liabilities, at Fa_4

Assets and Liabilities, at Fair Value - Rollforward of Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings, Description	0	0
Rollforward of Level 3 Assets [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	$ 0	$ 0
Rollforward of Level 3 Liabilities [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	0	1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	1.8	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0	1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	1.8	0
Equity Securities [Member]
Rollforward of Level 3 Assets [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 0	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)		(0.1)
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

Assets and Liabilities, at Fa_5

Assets and Liabilities, at Fair Value - Contingent Consideration (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 0	$ 0	$ 0.1
Payment for Contingent Consideration Liability, Financing Activities		$ 1

Assets and Liabilities, at Fa_6

Assets and Liabilities, at Fair Value - Available for Sale Securities in OCI (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Assets and Liabilities, at Fair Value [Abstract]
Equity Investments in Exchange Stock - Cost	$ 3.7	$ 3.7

Assets and Liabilities, at Fa_7

Assets and Liabilities, at Fair Value Assets and Liabilities, at Fair Value - Exchange Firm Common Stock (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Equity Investments in Exchange Stock - Cost	$ 3.7	$ 3.7
Financial Instruments, Owned, at Fair Value	$ 2,175.2	$ 2,054.8

Financial Instruments with Of_3

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	Sep. 30, 2019	Sep. 30, 2018
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Financial Instruments Sold, Not yet Purchased, at Fair Value	$ 714.8	$ 866.5

Financial Instruments with Of_4

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	Sep. 30, 2019	Sep. 30, 2018
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 3,671.5	$ 8,035.9
Derivative Liability, Fair Value, Gross Liability	3,604.5	8,511
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(3,581.9)	(8,118.5)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	(3,540.8)	(8,317.6)
Exchange-traded Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,437.1	2,455.7
Derivative Liability, Fair Value, Gross Liability	1,463.4	2,499.3
Over the Counter (OTC) Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	84.2	207
Derivative Liability, Fair Value, Gross Liability	106.2	369.9
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	36.9	49.8
Derivative Liability, Fair Value, Gross Liability	33.5	37.2
Over the Counter (OTC) Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	403.2	302.5
Derivative Liability, Fair Value, Gross Liability	368.8	303.9
Exchange-traded interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	900.1	449.3
Derivative Liability, Fair Value, Gross Liability	882	478.7
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	42.1	24.8
Derivative Liability, Fair Value, Gross Liability	43.6	25.9
Equity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	758.1	4,541.8
Derivative Liability, Fair Value, Gross Liability	700.2	4,794
TBA and forward settling securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	9.8	5
Derivative Liability, Fair Value, Gross Liability	6.8	2.1
Deposits and receivables from exchange clearing organizations [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	23.1	(268.7)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | TBA securities purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	3.7	1.2
Derivative Liability, Fair Value, Gross Liability	(0.6)	(0.6)
Derivative Asset, Notional Amount	(1,778.4)	(721.5)
Derivative Liability, Notional Amount	(234.5)	(293.2)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | TBA securities sold [Member] [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	3.2
Derivative Liability, Fair Value, Gross Liability	0	(1.5)
Derivative Asset, Notional Amount	0	(1,099.5)
Derivative Liability, Notional Amount	0	(812.7)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | Forward settling securities purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0.5
Derivative Asset, Notional Amount	0	(614.3)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | Forward settling securities sold [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	5.2	0.1
Derivative Asset, Notional Amount	(581.2)	(427.2)
Financial instruments owned [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	66.5	186.1
Payable to broker-dealers, clearing organizations and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	5.6	0
Payable to broker-dealers, clearing organizations and counterparties [Member] | TBA securities sold [Member] [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.9	0
Derivative Liability, Fair Value, Gross Liability	(5.9)	0
Derivative Asset, Notional Amount	(451.6)	0
Derivative Liability, Notional Amount	(2,788)	0
Payable to broker-dealers, clearing organizations and counterparties [Member] | Forward settling securities sold [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(0.3)	0
Derivative Liability, Notional Amount	(1,243.5)	0
Financial instrument sold, not yet purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	$ 58.1	$ 193.4

Financial Instruments with Of_5

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) number in Millions	Sep. 30, 2019
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative, Number of Instruments Held	10.6

Financial Instruments with Of_6

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 100.8	$ 94	$ 47.3
Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	8.1	9.2	8.7
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2.6)	1	(0.1)
TBA and forward settling securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(35.3)	14.5	(2.5)
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 71	$ 118.7	$ 53.4

Receivables from customers, n_3

Receivables from customers, net and notes receivable, net - Allowance for Customer Receivables (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Receivables from customers and notes receivable, net [Abstract]
Allowance For Doubtful Accounts - Deposits with and Receivables from Broker-Dealers, Clearings Organizations, and Counterparties	$ 36.9	$ 48
Allowance for Doubtful Accounts Receivable	$ 11.7	$ 10.2

Receivables from customers, n_4

Receivables from customers, net and notes receivable, net - Bad Debt Expense and Recoveries (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for bad debts									$ (2,500,000)	$ (3,100,000)	$ (4,300,000)
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)									2,600,000	2,900,000	4,200,000
Insurance Recoveries									10,000,000
Gain (Loss) Related to Litigation Settlement									2,400,000
(Recovery) bad debt on physical coal	$ (10,000,000)	$ 0	$ 0	$ (2,400,000)	$ 0	$ 0	$ 0	$ 1,000,000	(12,400,000)	1,000,000	47,000,000
Allowance for Doubtful Accounts Receivable, Charge-offs									300,000	300,000	100,000
Allowance for Doubtful Accounts Receivable, Recoveries									400,000	100,000
Commercial Hedging [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)									2,700,000	2,800,000	3,800,000
Clearing and Execution Services Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)									1,400,000	$ 400,000	300,000
Physical Commodities Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)											$ 200,000
Allowance for Doubtful Accounts Receivable, Recoveries									$ 12,400,000

Receivables from customers, n_5

Receivables from customers, net and notes receivable, net - Allowance for Bad Debts Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Receivables from customers and notes receivable, net [Abstract]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 48.6	$ 58.2	$ 54.6	$ 9.7
Allowance for Doubtful Accounts Receivable [Roll Forward]
Provision for bad debts	(9.8)	3.9	51
Allowance for Doubtful Accounts Receivable, Charge-offs	1.3	0.3	6.1
Allowance for Doubtful Accounts Receivable, Recoveries	0.4	0.1
SEC Schedule, 12-09, Valuation Allowances and Reserves, Increase (Decrease) Adjustment	$ 1.5	$ 0	$ 0

Physical Commodities Inventor_3

Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Inventory [Line Items]
Agricultural Related Inventory	$ 144.8	$ 114.7
Inventory, Net	229.3	222.5
Physical commodities inventory at fair value		156.9	$ 156.9
Physical commodities inventory - precious metals [Member]
Inventory [Line Items]
Physical commodities inventory at fair value	7.1	42.1
Inventory, Finished Goods, Net of Reserves	$ 77.4	$ 65.7

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Depreciation	$ 11.2	$ 9.4	$ 7
Furniture and Fixtures, Gross	10.6	8.7
Capitalized Computer Software, Gross	33.9	30.5
Machinery and Equipment, Gross	28.1	24.7
Leasehold Improvements, Gross	20.3	17
Property, Plant and Equipment, Gross	92.9	80.9
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(49)	(38.5)
Property, Plant and Equipment, Net	$ 43.9	$ 42.4
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	10 years

Property and Equipment, net Dep

Property and Equipment, net Depreciation Details (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation	$ 11.2	$ 9.4	$ 7

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Goodwill	$ 51.2	$ 48.4
Commercial Hedging [Member]
Goodwill [Line Items]
Goodwill	30.3	30.3
Global Payments [Member]
Goodwill [Line Items]
Goodwill	7.6	8.9
Physical Commodities Segment [Member]
Goodwill [Line Items]
Goodwill	4.6	2.4
Securities Segment [Member]
Goodwill [Line Items]
Goodwill	$ 8.7	$ 6.8

Goodwill Goodwill Reconciliatio

Goodwill Goodwill Reconciliation (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Goodwill, Purchase Accounting Adjustments	$ 1,300,000
Goodwill, Translation and Purchase Accounting Adjustments	0	$ (1,300,000)
Coininvest and European Precious Metals Trading [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period	2,200,000
Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period	$ 1,900,000

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Computer Software, Gross	$ 33.9	$ 30.5
Finite-Lived Intangible Assets, Gross	27.4	24.1
Finite-Lived Intangible Assets, Accumulated Amortization	15.5	12.7
Intangible Assets, Net (Excluding Goodwill)	16.7	11.4
Finite-Lived Intangible Assets, Net	11.9	11.4
Indefinite-Lived License Agreements	2.1	0
Indefinite-lived Intangible Assets (Excluding Goodwill)	4.8	0
Intangible Assets, Gross (Excluding Goodwill)	32.2	24.1
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Computer Software, Gross	5.3	2.7
Finite-Lived Intangible Assets, Accumulated Amortization	(3)	(2.6)
Finite-Lived Intangible Assets, Net	2.3	0.1
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Customer Lists, Gross	22.1	21.4
Finite-Lived Intangible Assets, Accumulated Amortization	(12.5)	(10.1)
Finite-Lived Intangible Assets, Net	9.6	11.3
Licensing Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)	$ 2.7	$ 0

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Intangible Assets [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 2.9
Amortization of Intangible Assets	2.8	$ 2.3	$ 2.8
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2020	2.9
Fiscal 2021	1.6
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1.4
Fiscal 2022	3.1
Finite-Lived Intangible Assets, Net	$ 11.9	$ 11.4

Intangible Assets Intangible As

Intangible Assets Intangible Asset Additions (Details) $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)
Business Acquisition [Line Items]
Indefinite-lived Intangible Assets Acquired	$ 2.7
Coininvest and European Precious Metals Trading [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	2.6
Indefinite-lived Intangible Assets Acquired	2.1
Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	0.7
Akshay Financeware, Inc. Acquisition [Member]
Business Acquisition [Line Items]
Indefinite-lived Intangible Assets Acquired	$ 2.7

Intangible Assets Intangible _2

Intangible Assets Intangible Assets - Finite-Lived Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of Intangible Assets	$ 2.8	$ 2.3	$ 2.8

Credit Facilities - Number of C

Credit Facilities - Number of Credit Facilities (Details)	12 Months Ended
	Sep. 30, 2019USD ($)Rate	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2013USD ($)	Dec. 11, 2019USD ($)
Line of Credit Facility [Line Items]
Long-term Debt, Gross	$ 168,400,000
Payments of Debt Issuance Costs	$ 3,300,000	$ 400,000	$ 300,000	$ 1,700,000
Number of credit facilities	4
Line of Credit Facility, Maximum Borrowing Capacity	$ 100
Maximum Borrowing Capacity Under Credit Facilities	$ 743,900,000
Term loan periodic principal payment percentage | Rate	1.30%
Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End | Rate	5.00%
Line of Credit Facility, Maximum Borrowing Capacity	$ 20,000,000
Rabobank Uncommited Line of Credit [Domain] | Base Rate [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Payments of Debt Issuance Costs	$ 3,100,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate	0.625%
Maximum Borrowing Capacity Under Credit Facilities	$ 350,000,000	$ 262,000,000
INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50,000,000
INTL FCStone Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate	0.50%
Line of Credit Facility, Interest Rate at Period End | Rate	7.25%
Line of Credit Facility, Maximum Borrowing Capacity	$ 75,000,000
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate	0.38%
Line of Credit Facility, Maximum Borrowing Capacity	$ 232,500,000
Subsequent Event [Member] | INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 196,500,000
Debt Instrument, Face Amount					196,500,000
Maximum Borrowing Capacity Under Credit Facilities					$ 386,400,000
Cost of Funds Rate [Domain] | Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.00%
Base Rate [Member] | INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Line of Credit Facility, Interest Rate at Period End | Rate	7.25%
Base Rate [Member] | INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.50%
Base Rate [Member] | INTL FCStone Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Base Rate [Member] | FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End | Rate	5.00%
Eurodollar [Member] | INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		3.00%
Line of Credit Facility, Interest Rate at Period End | Rate	4.95%
Eurodollar [Member] | FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End | Rate	4.50%

Credit Facilities (Details)

Credit Facilities (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2013	Dec. 11, 2019	Sep. 30, 2015	Apr. 15, 2015
Line of Credit Facility [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 800,000
Repayments of Long-term Debt	6,600,000	$ 0	$ 0
Line of Credit Facility, Maximum Borrowing Capacity	100
Maximum Borrowing Capacity Under Credit Facilities	743,900,000
Notes Payable to Bank	400,000	$ 1,200,000					$ 4,000,000
Debt Instrument, Interest Rate, Stated Percentage		8.50%
Payments of Debt Issuance Costs	3,300,000	$ 400,000	300,000	$ 1,700,000
Senior secured term loan, net	$ 167,600,000	0				$ 45,500,000
Write off of Deferred Debt Issuance Cost			$ 1,000,000
Debt, Weighted Average Interest Rate	2.00%
INTL FCStone Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End	7.25%
Line of Credit Facility, Maximum Borrowing Capacity	$ 75,000,000
Line of Credit, Current	$ 0	0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.50%
Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End	5.00%
Line of Credit Facility, Maximum Borrowing Capacity	$ 20,000,000
Short-term Debt	$ 3,400,000	3,800,000
Letter of Credit Interest Rate	2.75%
INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Long-term Debt	$ 167,600,000	0
Line of Credit, Current	70,000,000	208,200,000
Maximum Borrowing Capacity Under Credit Facilities	$ 350,000,000	262,000,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.625%
Payments of Debt Issuance Costs	$ 3,100,000
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	232,500,000
Line of Credit, Current	$ 128,500,000	128,000,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.38%
INTL FCStone, Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50,000,000
Line of Credit, Current	0	0
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	358,000,000
IFFI Uncommitted Lines of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Short-term Debt	0	14,000,000
IFL Uncommitted Line of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Short-term Debt	$ 0	$ 0
Base Rate [Member] | Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Eurodollar [Member] | INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End	4.95%
Debt Instrument, Basis Spread on Variable Rate		3.00%
Eurodollar [Member] | FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate at Period End	4.50%
Subsequent Event [Member] | INTL FCStone Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 196,500,000
Long-term Debt					189,900,000
Maximum Borrowing Capacity Under Credit Facilities					$ 386,400,000

Commitments and Contingencies -

Commitments and Contingencies - Contingencies and Litigation (Details) $ in Millions	Sep. 30, 2019USD ($)
Commitments and Contingencies [Abstract]
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 29.2

Commitments and Contingencies_2

Commitments and Contingencies - Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Operating Leases [Abstract]
Operating Leases, Rent Expense	$ 14.1	$ 12	$ 11.3
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	11.2
Operating Leases, Future Minimum Payments, Due in Two Years	9.9
Operating Leases, Future Minimum Payments, Due in Three Years	7.5
Operating Leases, Future Minimum Payments, Due in Four Years	6.2
Operating Leases, Future Minimum Payments, Due in Five Years	5.8
Operating Leases, Future Minimum Payments, Due Thereafter	2.6
Operating Leases, Future Minimum Payments Due	$ 43.2

Commitments and Contingencies_3

Commitments and Contingencies - Purchase Obligations (Details) $ in Millions	Sep. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase Obligation, Due in Next Twelve Months	$ 2,893.1
Purchase Obligation, Due in Second and Third Year	16.3
Purchase Obligation, Due in Fourth and Fifth Year	18
Other Commitment, Due in Next Twelve Months	$ 2,633.9

Commitments and Contingencies_4

Commitments and Contingencies - Self-Insurance (Details) $ in Millions	Sep. 30, 2019USD ($)
Commitments and Contingencies [Abstract]
Self Insurance Reserve	$ 0.8

Regulatory Requirements and S_3

Regulatory Requirements and Subsidiary Dividend Restrictions - Minimum net capital (Details)	Sep. 30, 2019USD ($)
Minimum Net Capital Required for Broker-Dealer Subsidiary	$ 1,000,000
Minimum Net Capital Required for Entity	0.08
INTL FCStone Financial [Member]
Net Capital under Commodity Exchange Act Computation	170,100,000
Required Net Capital under Commodity Exchange Act	97,500,000
INTL FCStone, Ltd [Member]
Net Capital under Commodity Exchange Act Computation	231,700,000
Required Net Capital under Commodity Exchange Act	$ 123,300,000

Regulatory Requirements and S_4

Regulatory Requirements and Subsidiary Dividend Restrictions - Regulatory Capital Requirements (Details)	Sep. 30, 2019USD ($)
Minimum Net Capital Required for Entity	$ 0.08
INTL FCStone Financial [Member]
Cash and Securities Segregated under Commodity Exchange Act Regulation	2,288,700,000
Secured funds	173,500,000
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	2,232,100,000
Secured Funds Required Under Commodity Exchange Act	(161,000,000)
INTL FCStone, Ltd [Member]
Cash and Securities Segregated under Commodity Exchange Act Regulation	207,600,000
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	$ 196,900,000

Regulatory Requirements and S_5

Regulatory Requirements and Subsidiary Dividend Restrictions Regulatory Requirements and Subsidiary Dividend Restrictions - Customer Reserve Requirements (Details) $ in Millions	Sep. 30, 2019USD ($)
Customer Reserve Requirement [Member] [Member]
Cash Reserve Deposit Required	$ 19.4
Cash Reserve Deposit Required and Made	21.4
PAB Reserve Requirement [Member]
Cash Reserve Deposit Required	2.6
Cash Reserve Deposit Required and Made	$ 3.6

Commodity and Other Repurchas_4

Commodity and Other Repurchase Agreements (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Securities Borrowed, Gross	$ 1,423,200,000	$ 225,500,000
Securities Purchased under Agreements to Resell, Gross	1,474,400,000	870,800,000
Securities sold under agreements to repurchase	2,773,700,000	1,936,700,000
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	3,060,200,000
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	329,800,000
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	478,800,000
Securities Loaned, Fair Value of Collateral	1,414,000,000
Financial Instruments Owned and Pledged as Collateral, Amount Not Eligible to be Repledged by Counterparty	1,228,900,000
Securities Loaned	1,459,900,000	277,900,000
Collateralized Financings	4,233,600,000	2,214,600,000
Securities Purchased under Agreements to Resell, Liability	(49,900,000)	0
Securities purchased under agreements to resell	1,424,500,000	870,800,000
Securities Borrowed, Liability	0	0
Securities Borrowed	1,423,200,000	225,500,000
Securities Sold under Agreements to Repurchase, Gross	2,823,600,000	1,936,700,000
Securities Sold under Agreements to Repurchase, Asset	(49,900,000)	0
Securities Loaned, Gross	1,459,900,000	277,900,000
Securities Loaned, Asset	0	0
Sales Repurchase Agreements	0	1,900,000
Securities Sold under Agreements to Repurchase, Fair Value of Collateral		478,800,000	$ 123,000,000
Maturity Overnight [Member]
Securities sold under agreements to repurchase	1,553,900,000	934,900,000
Securities Loaned	1,459,900,000	277,900,000
Collateralized Financings	3,013,800,000	1,212,800,000
Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	565,800,000	661,300,000
Securities Loaned	0	0
Collateralized Financings	565,800,000	661,300,000
Maturity 30 to 90 Days [Member]
Securities sold under agreements to repurchase	654,000,000	340,500,000
Securities Loaned	0	0
Collateralized Financings	654,000,000	340,500,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities sold under agreements to repurchase	2,208,700,000	1,385,400,000
Asset-backed Securities [Member]
Securities sold under agreements to repurchase	96,700,000	50,000,000
US Government Debt Securities [Member]
Securities sold under agreements to repurchase	108,800,000	39,600,000
US Government Agencies Debt Securities [Member]
Securities sold under agreements to repurchase	359,500,000	461,700,000
Equity Securities [Member]
Securities Loaned	$ 1,459,900,000	$ 277,900,000

Commodity and Other Repurchas_5

Commodity and Other Repurchase Agreements Fair Value of Securities Accepted or Pledged as Collateral (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Revenues from contracts with customers [Abstract]
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	$ 3,060,200,000
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	478,800,000
Financial Instruments Owned and Pledged as Collateral, Amount Not Eligible to be Repledged by Counterparty	1,228,900,000
Pledged Assets Separately Reported, Securities Pledged for Repurchase Agreements, at Fair Value	1,175,100,000
Securities Loaned, Fair Value of Collateral	1,414,000,000
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	329,800,000
Pledged Financial Instruments, Not Separately Reported, Securities	$ 0	$ 27,100,000

Share-Based Compensation - Shar

Share-Based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 0.7	$ 2.1	$ 2.6
Allocated Share-based Compensation Expense	$ 8.1	$ 6.6	$ 6.3

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Plan (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	2,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	692,652	588,020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 10.47	$ 9.79	$ 8.67
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Stock Options	$ 9,900,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	5 years 7 months 10 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	$ 700,000	$ 2,100,000	$ 2,600,000

Share-Based Compensation - St_2

Share-Based Compensation - Stock Option Plan Fair Value Weighted-Average Assumptions (Details)	12 Months Ended
	Sep. 30, 2019Rate	Sep. 30, 2018Rate	Sep. 30, 2017Rate
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	27.00%	30.00%	31.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.00%	1.00%	1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	6 years 18 days	3 years 22 days	3 years 29 days

Share-Based Compensation - Sh_2

Share-Based Compensation - Share-Based Compensation Table (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	2,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	588,020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	835,454
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	(922,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	25,048
Share-based Compensation Arrangement by Share-based Payment Award, Options, Other Increases (Decreases) in Period	(46,444)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	(1,584)
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	692,652	588,020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,684,378	835,454
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	472,424
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 37.59	$ 29.27
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	44.31
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	25.04
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	31.31
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	33.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	28.96
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value	11.32	11.93
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	10.47	$ 9.79	$ 8.67
Share-based Compensation Arrangement by Share-based Payment Award, Options, Excrecises in Period, Weighted Average Grant Date Fair Value	5.21
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeited in Period, Weighted Average Grant Date Fair Value	11.91
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expired in Period, Weighted Average Grant Date Fair Value	7.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Excercisable, Weighted Average Grant Date Fair Value	$ 12.27
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	4 years 7 months 13 days	3 years 4 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	2 years 29 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 9,200,000	$ 15,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 5,800,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Stock Options	$ 9,900,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	5 years 7 months 10 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 700,000	$ 2,100,000	$ 2,600,000

Share-Based Compensation - Opti

Share-Based Compensation - Options by Exercise Price (Details)	12 Months Ended
	Sep. 30, 2019$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options | shares	1,684,378
Weighted Average Exercise Price	$ 37.59
Weighted Average Remaining Term (in years)	4 years 7 months 13 days
$0 - $5,00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 0
Exercise Price Range, Upper Range Limit	$ 5
Number of Outstanding Options | shares	0
$5.00 - $10.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 5
Exercise Price Range, Upper Range Limit	$ 10
Number of Outstanding Options | shares	0
$10.00 - $15.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 10
Exercise Price Range, Upper Range Limit	$ 15
Number of Outstanding Options | shares	0
$15.00 - $20.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 15
Exercise Price Range, Upper Range Limit	$ 20
Number of Outstanding Options | shares	0
$20.00 - $25.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 20
Exercise Price Range, Upper Range Limit	$ 25
Number of Outstanding Options | shares	0
$25.00 - $30.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 25
Exercise Price Range, Upper Range Limit	$ 30
Number of Outstanding Options | shares	564,000
Weighted Average Exercise Price	$ 25.91
Weighted Average Remaining Term (in years)	2 years 4 months 13 days
$30.00 - $35.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 30
Exercise Price Range, Upper Range Limit	$ 35
Number of Outstanding Options | shares	32,881
Weighted Average Exercise Price	$ 31.37
Weighted Average Remaining Term (in years)	3 months 11 days
$35.00 - $40.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 35
Exercise Price Range, Upper Range Limit	$ 40
Number of Outstanding Options | shares	213,830
Weighted Average Exercise Price	$ 39.33
Weighted Average Remaining Term (in years)	2 years 5 months 5 days
$40.00 - $45.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 40
Exercise Price Range, Upper Range Limit	$ 45
Number of Outstanding Options | shares	871,667
Weighted Average Exercise Price	$ 44.91
Weighted Average Remaining Term (in years)	6 years 9 months 11 days
$45.00 - $50.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 45
Exercise Price Range, Upper Range Limit	$ 50
Number of Outstanding Options | shares	0
$50.00 - $55.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 50
Exercise Price Range, Upper Range Limit	$ 55
Number of Outstanding Options | shares	0

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Plan (Details) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	1.5
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1.2
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized | $	$ 10
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition - Restricted Stock	1 year 4 months 10 days

Share-Based Compensation - Re_2

Share-Based Compensation - Restricted Stock Plan Table (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	1,377,278
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease)	223,481
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	3,105
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	1,156,902	1,377,278
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	274,628
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	223,481
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(144,226)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(3,105)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	350,778	274,628
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 38.20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	39.57
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	35.85
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	35.62
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 40.06	$ 38.20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms	1 year 4 months 10 days	1 year 1 month 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	$ 14.4	$ 13.3
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 10
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition - Restricted Stock	1 year 4 months 10 days

Retirement Plans Retirement Pla

Retirement Plans Retirement Plans - Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 7.5	$ 6.8	$ 6.1
UK Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	100.00%
UK Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	10.00%
401k Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	62.50%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	8.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, Two to Three Years	33.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, Three to Four Years	66.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, All Years	100.00%
401k Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	80.00%
401k Plan [Member] | Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	1.00%

Retirement Plans Retirement P_2

Retirement Plans Retirement Plans - Defined Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0.1	$ 0.2	$ 0.3
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.00%
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	$ 2
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	2
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	2
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	9.5
Defined Benefit Plan, Plan Assets, Contributions by Employer	0.1	1
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	2.1
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	$ 2.1
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	20.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	80.00%
Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 0.1
Defined Benefit Plan, Benefit Obligation	1.7	1.6
Defined Benefit Plan, Funded (Unfunded) Status of Plan	1.6
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	38.9	35.6
Defined Benefit Plan, Benefit Obligation	$ 36.5	$ 32.5
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.10%	4.20%
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (2.4)	$ (3.1)

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Other Expenses [Abstract]
Accretion Expense									$ 0	$ 0	$ 0.1
General Insurance Expense									3.4	2.6	2.7
Advertising Expense									5.2	6.2	4
Supplies and Postage Expense									1.9	1.7	2.1
Clearance Fees									2.5	2.5	2.6
Taxes, Miscellaneous									4.6	4.9	4.6
Other Expenses									10.8	8.4	9.8
Other	$ 43.2	$ 42.6	$ 41.1	$ 37.6	$ 35.3	$ 35.2	$ 36.4	$ 33.4	$ 28.4	$ 26.3	$ 25.9

Bad Debt on Physical Coal (Deta

Bad Debt on Physical Coal (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Bad Debt on Physical Coal [Abstract]
(Recovery) bad debt on physical coal	$ (10,000,000)	$ 0	$ 0	$ (2,400,000)	$ 0	$ 0	$ 0	$ 1,000,000	$ (12,400,000)	$ 1,000,000	$ 47,000,000
Payments for Legal Settlements									8,400,000
Gain (Loss) Related to Litigation Settlement									2,400,000
Insurance Recoveries									$ 10,000,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Other	$ 0.2				$ 0.4				$ 0.2	$ 0.4
Income tax expense	6.9	$ 5.3	$ 7.5	$ 6.2	4.8	$ 8.9	$ 6.8	$ 25.5	25.9	46	$ 8.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized (Gain) Loss Arising During Period, Tax									(0.2)	0.1	1
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation									0	0	0.1
Other Comprehensive Income (Loss), Tax									25.7	46.1	9.9
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense									0
Operating Loss Carryforwards	7.1				9.4				7.1	9.4
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	1.1				0				1.1	0	$ 21.9
Deferred Tax Assets, Net of Valuation Allowance, Operating Loss Carryforwards, State and Local	5.6								5.6
Deferred Tax Assets, Valuation Allowance	8.5				3.5				8.5	3.5
Valuation Allowance, Deferred Tax Asset, Change in Amount									5
Undistributed Earnings of Foreign Subsidiaries	$ 383.5				$ 354.7				$ 383.5	$ 354.7

Income Taxes - Current and Defe

Income Taxes - Current and Deferred Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)									$ (1.9)	$ 0.8	$ 0.7
Current State and Local Tax Expense (Benefit)									(0.8)	0.5	1.2
Current Foreign Tax Expense (Benefit)									24.9	22.4	16.7
Current Income Tax Expense (Benefit)									22.2	23.7	18.6
Deferred Income Tax Expense (Benefit)									3.7	22.3	(9.8)
Income tax expense	$ 6.9	$ 5.3	$ 7.5	$ 6.2	$ 4.8	$ 8.9	$ 6.8	$ 25.5	$ 25.9	$ 46	$ 8.8

Income Taxes - US and Internati

Income Taxes - US and International Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ (2.6)	$ 9.9	$ (13.9)
Income (Loss) from Continuing Operations before Income Taxes, Foreign	113.6	91.6	29.1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 111	$ 101.5	$ 15.2

Income Taxes - Effective Rate R

Income Taxes - Effective Rate Reconciliation (Details)	12 Months Ended
	Sep. 30, 2019Rate	Sep. 30, 2018Rate	Sep. 30, 2017Rate
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	21.00%	25.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes	(1.50%)	0.80%	(2.60%)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential	0.70%	(0.80%)	11.50%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment	(0.10%)	(0.20%)	(3.60%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other	0.70%	2.10%	8.10%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	(1.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	2.20%	0.00%	0.00%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(0.40%)	0.20%	(0.60%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	0.00%	8.50%	0.00%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent	0.00%	11.00%	0.00%
Effective Income Tax Rate, Continuing Operations	23.30%	45.30%	57.70%
Foreign Tax Authority [Member]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance	1.00%	(0.80%)	(1.40%)
State and Local Jurisdiction [Member]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance	0.50%	0.00%	4.10%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilites (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Operating Loss Carryforwards [Line Items]
Federal operating loss carryforwards, net of valuation allowances	$ 0.6
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	2.6	$ 4.2
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	5	6.5
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	3.3	2.8
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation	3.6	1.4
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	9.2	8.7
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	1.1	0	$ 21.9
Deferred Tax Assets, Intangible Assets	4.8	1.8
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	1.3	1.5
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	0.5	0
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits	2.2	3.4
Deferred Tax Assets, Other	1.1	0.9
Deferred Tax Assets, Gross	34.7	31.2
Deferred Tax Assets, Valuation Allowance	(8.5)	(3.5)
Deferred Tax Assets, Net of Valuation Allowance	26.2	27.7
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	3.2	2.6
Deferred Tax Liabilities, Prepaid Expenses	2.2	1.8
Deferred Tax Liabilities, Property, Plant and Equipment	2.6	3.1
Deferred Tax Liabilities, Pension Liability	0.2	0.4
Deferred Tax Liabilities, Gross	8.2	7.9
Deferred tax assets, Net	$ 18	19.8
SINGAPORE
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign		2.9
Tax Period [Domain]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		$ 5.1

Income Taxes - FIN 48 Analysis

Income Taxes - FIN 48 Analysis (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	$ 0.1
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance beginning of year	0.1	$ 0.1	$ 0.1
Gross increases for tax positions related to prior years		0	0
Balance end of year	$ 0	$ 0.1	$ 0.1

Income Taxes Income Taxes - Tax

Income Taxes Income Taxes - Tax Reform (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure - Tax Reform [Abstract]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 8.6
Foreign Earnings Repatriated	$ 13
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount		11.2
Undistributed Earnings of Foreign Subsidiaries	$ 383.5	$ 354.7
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	21.00%	25.00%	35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	2.20%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	0.00%	8.50%	0.00%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Percent	0.00%	11.00%	0.00%

Income Taxes Income Taxes - Rep

Income Taxes Income Taxes - Repatriation of Foreign Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Undistributed Earnings of Foreign Subsidiaries	$ 383.5	$ 354.7
Foreign Earnings Repatriated	$ 13

Acquisitions PayCommerce Financ

Acquisitions PayCommerce Financial Solutions Acquisition (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2018
PayCommerce [Member] [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 3.8
Business Combination, Acquired Receivable, Fair Value		0.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		0.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets		0.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		2.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		$ 1.3
Finite-Lived Intangible Asset, Useful Life		5 years
Goodwill, Acquired During Period		$ 2.6
Akshay Financeware, Inc. Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 0.2

Acquisitions ICAP (Details)

Acquisitions ICAP (Details) $ in Millions	12 Months Ended
	Sep. 30, 2018USD ($)
ICAP [Member] [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 6

Sterne Agee (Details)

Sterne Agee (Details) $ in Millions	9 Months Ended
	Jun. 30, 2019USD ($)
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ 5.4

Acquisitions Carl Kliem S.A. (D

Acquisitions Carl Kliem S.A. (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Nov. 30, 2018
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ 5.4
Carl Kliem S.A. [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 2.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 1.7
Business Combination, Acquired Receivables, Gross Contractual Amount			1.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			0.1
Business Combination, Acquired Receivable, Fair Value			0.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable			0.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities			$ 0.2
Business Combination, Bargain Purchase, Gain Recognized, Amount		0.1
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		4.2
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 2.3

Acquisitions GMP Securities, LL

Acquisitions GMP Securities, LLC (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Jan. 14, 2019
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ 5.4
GMP Securities Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 1.1
Business Combination, Acquired Receivables, Gross Contractual Amount			7.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets			7.1
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets			2.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			0.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets			0.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			20
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable			1.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other			0.1
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 8.2
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		2.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities			4.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			6.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			$ 13.6
Business Combination, Consideration Transferred	$ 8.2
Business Combination, Bargain Purchase, Gain Recognized, Amount		$ 5.4

Acquisitions Coininvest and Eur

Acquisitions Coininvest and European Precious Metals Trading Acquisitions (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Apr. 01, 2019
Coininvest and EPMT Acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 2
Business Combination, Acquired Receivables, Gross Contractual Amount		1.2
Business Combination, Acquired Receivable, Fair Value		0.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory		9.8
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		0.2
Business Combination, Consideration Transferred	$ 22
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets		1.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		15.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable		0.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		0.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		15.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		2.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		2.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 4.6
Coininvest and European Precious Metals Trading [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period	$ 2.2

Acquisitions Fillmore Advisors,

Acquisitions Fillmore Advisors, LLC Acquisition (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 01, 2019	Apr. 01, 2019
Coininvest and EPMT Acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets			1.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			15.6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable			0.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			0.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			15.2
Business Combination, Consideration Transferred	$ 22
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			2.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			$ 4.6
Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 0.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets		0.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		1.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable		0.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		0.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		0.6
Goodwill, Acquired During Period	1.9
Business Combination, Consideration Transferred	3.2
Payments to Acquire Businesses, Gross	$ 1.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		0.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		0.7
Business Combination, Contingent Consideration, Liability		1.8
Cash [Member] | Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability		$ 1.8

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net		$ (34.8)	$ (33.1)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		(0.8)	(9)	$ (1.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax		0.8	(0.3)	(1.2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		0.1	0.1	0.4
Other Comprehensive Income (Loss), Net of Tax		(1.7)	(8.6)	0.1
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net		(31.5)	(30.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ (0.8)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax		0.2
Other Comprehensive Income (Loss), Net of Tax		(1)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net		(3.3)	(2.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ (0.8)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		0.1
Other Comprehensive Income (Loss), Net of Tax		(0.7)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net		(34.8)	(33.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(1.6)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(0.1)
Other Comprehensive Income (Loss), Net of Tax		$ (1.7)	$ (8.6)	$ 0.1

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 11,279,600,000	$ 7,873,000,000	$ 7,192,200,000	$ 6,552,200,000	$ 6,078,800,000	$ 7,118,300,000	$ 6,507,000,000	$ 7,918,600,000	$ 32,897,000,000	$ 27,622,700,000	$ 29,423,600,000
Cost of sales of physical commodities	10,992,700,000	7,589,600,000	6,921,100,000	6,287,500,000	5,835,600,000	6,858,500,000	6,246,800,000	7,706,000,000	31,790,900,000	26,646,900,000	28,639,600,000
Operating revenues	286,900,000	283,400,000	271,100,000	264,700,000	243,200,000	259,800,000	260,200,000	212,600,000	1,106,100,000	975,800,000	784,000,000
Transaction-based clearing expenses	45,000,000	45,700,000	42,700,000	50,100,000	43,100,000	49,000,000	50,700,000	36,900,000	183,500,000	179,700,000	136,300,000
Introducing broker commissions	27,700,000	29,600,000	24,800,000	32,600,000	32,400,000	34,100,000	36,200,000	31,100,000	114,700,000	133,800,000	113,000,000
Interest expense	40,800,000	42,500,000	38,400,000	33,000,000	25,300,000	22,100,000	19,000,000	14,300,000	154,700,000	80,700,000	42,100,000
Net operating revenues	173,400,000	165,600,000	165,200,000	149,000,000	142,400,000	154,600,000	154,300,000	130,300,000	653,200,000	581,600,000	492,600,000
Compensation and benefits	105,200,000	100,900,000	97,900,000	89,100,000	85,400,000	86,900,000	88,200,000	77,200,000	393,100,000	337,700,000	295,700,000
Bad debts	1,000,000	500,000	700,000	300,000	1,200,000	1,600,000	200,000	100,000
(Recovery) bad debt on physical coal	(10,000,000)	0	0	(2,400,000)	0	0	0	1,000,000	(12,400,000)	1,000,000	47,000,000
Other	43,200,000	42,600,000	41,100,000	37,600,000	35,300,000	35,200,000	36,400,000	33,400,000	28,400,000	26,300,000	25,900,000
Total compensation and other expenses	139,400,000	144,000,000	139,700,000	124,600,000	121,900,000	123,700,000	124,800,000	111,700,000	547,700,000	482,100,000	477,400,000
Other gains	100,000	0	5,400,000	0	0	2,000,000	0	0	5,500,000	2,000,000	0
Income before tax	34,100,000	21,600,000	30,900,000	24,400,000	20,500,000	32,900,000	29,500,000	18,600,000	111,000,000	101,500,000	15,200,000
Income tax expense	6,900,000	5,300,000	7,500,000	6,200,000	4,800,000	8,900,000	6,800,000	25,500,000	25,900,000	46,000,000	8,800,000
Net income	$ 27,200,000	$ 16,300,000	$ 23,400,000	$ 18,200,000	$ 15,700,000	$ 24,000,000	$ 22,700,000	$ (6,900,000)	$ 85,100,000	$ 55,500,000	$ 6,400,000
Basic	$ 1.42	$ 0.85	$ 1.23	$ 0.96	$ 0.83	$ 1.27	$ 1.20	$ (0.37)	$ 4.46	$ 2.93	$ 0.32
Diluted	$ 1.40	$ 0.84	$ 1.21	$ 0.94	$ 0.81	$ 1.25	$ 1.18	$ (0.37)	$ 4.39	$ 2.87	$ 0.31

Segment and Geographic Inform_3

Segment and Geographic Information (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 11,279,600,000	$ 7,873,000,000	$ 7,192,200,000	$ 6,552,200,000	$ 6,078,800,000	$ 7,118,300,000	$ 6,507,000,000	$ 7,918,600,000	$ 32,897,000,000	$ 27,622,700,000	$ 29,423,600,000
Operating revenues	286,900,000	283,400,000	271,100,000	264,700,000	243,200,000	259,800,000	260,200,000	212,600,000	1,106,100,000	975,800,000	784,000,000
Net operating revenues	173,400,000	165,600,000	165,200,000	149,000,000	142,400,000	154,600,000	154,300,000	130,300,000	653,200,000	581,600,000	492,600,000
Net Segment Contribution									482,800,000	432,400,000	387,000,000
Segment Income									305,700,000	261,900,000	169,000,000
Costs not allocated to operating segments									200,200,000	162,400,000	153,800,000
Other gains	100,000	0	5,400,000	0	0	2,000,000	0	0	5,500,000	2,000,000	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	34,100,000	21,600,000	$ 30,900,000	$ 24,400,000	20,500,000	$ 32,900,000	$ 29,500,000	$ 18,600,000	111,000,000	101,500,000	15,200,000
Assets	$ 9,936,100,000				7,824,700,000				9,936,100,000	7,824,700,000	6,243,400,000
Commercial Hedging [Member]
Segment Reporting Information [Line Items]
Total revenues									302,400,000	286,700,000	244,600,000
Operating revenues									302,400,000	286,700,000	244,600,000
Net operating revenues									236,500,000	226,400,000	194,300,000
Net Segment Contribution									170,400,000	164,700,000	141,800,000
Segment Income									100,100,000	96,400,000	72,800,000
Assets		2,041,000,000			1,935,700,000					1,935,700,000	1,650,300,000
Global Payments [Member]
Segment Reporting Information [Line Items]
Total revenues									112,800,000	99,200,000	89,200,000
Operating revenues									112,800,000	99,200,000	89,200,000
Net operating revenues									107,000,000	93,500,000	80,600,000
Net Segment Contribution									86,600,000	75,000,000	64,400,000
Segment Income									66,100,000	59,800,000	50,600,000
Assets		278,300,000			206,600,000					206,600,000	199,500,000
Securities Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									295,300,000	196,200,000	151,700,000
Operating revenues									295,300,000	196,200,000	151,700,000
Net operating revenues									131,000,000	94,600,000	94,600,000
Net Segment Contribution									81,900,000	69,100,000	75,600,000
Segment Income									47,400,000	40,800,000	46,600,000
Assets		5,219,100,000			3,058,200,000					3,058,200,000	2,101,700,000
Physical Commodities Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									31,864,700,000	26,703,800,000	28,684,400,000
Operating revenues									73,800,000	56,900,000	44,800,000
Net operating revenues									56,300,000	44,800,000	37,300,000
Net Segment Contribution									40,500,000	31,800,000	27,200,000
Segment Income									38,000,000	16,600,000	(31,400,000)
Assets		357,800,000			413,700,000					413,700,000	339,500,000
Clearing and Execution Services Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									326,100,000	332,400,000	259,800,000
Operating revenues									326,100,000	332,400,000	259,800,000
Net operating revenues									133,200,000	122,600,000	102,200,000
Net Segment Contribution									103,400,000	91,800,000	78,000,000
Segment Income									54,100,000	48,300,000	30,400,000
Assets		1,892,100,000			2,109,900,000					2,109,900,000	1,818,900,000
Corporate [Member]
Segment Reporting Information [Line Items]
Total revenues									20,800,000	23,900,000	4,700,000
Operating revenues									20,800,000	23,900,000	4,700,000
Net operating revenues									$ (10,800,000)	(300,000)	(16,400,000)
Assets		$ 147,800,000			$ 100,600,000					$ 100,600,000	$ 133,500,000

Segment and Geographic Inform_4

Segment and Geographic Information - Total Revenues by Geographic Location (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Total revenues	$ 11,279,600,000	$ 7,873,000,000	$ 7,192,200,000	$ 6,552,200,000	$ 6,078,800,000	$ 7,118,300,000	$ 6,507,000,000	$ 7,918,600,000	$ 32,897,000,000	$ 27,622,700,000	$ 29,423,600,000
Operating revenues	286,900,000	$ 283,400,000	$ 271,100,000	$ 264,700,000	243,200,000	$ 259,800,000	$ 260,200,000	$ 212,600,000	1,106,100,000	975,800,000	784,000,000
Long-Lived Assets	43,900,000				42,400,000				43,900,000	42,400,000	38,700,000
UNITED STATES
Total revenues									1,947,600,000	1,587,600,000	1,168,000,000
Operating revenues									799,400,000	695,300,000	529,400,000
Long-Lived Assets	33,900,000				33,000,000				33,900,000	33,000,000	29,700,000
Europe [Member]
Total revenues									280,200,000	189,600,000	166,900,000
Operating revenues									209,600,000	189,000,000	166,900,000
Long-Lived Assets	6,600,000				6,800,000				6,600,000	6,800,000	7,300,000
South America [Member]
Total revenues									56,500,000	59,500,000	53,900,000
Operating revenues									56,500,000	58,000,000	54,000,000
Long-Lived Assets	2,100,000				1,400,000				2,100,000	1,400,000	1,500,000
Asia [Member]
Total revenues									30,606,900,000	25,781,400,000	28,030,300,000
Operating revenues									34,800,000	28,900,000	29,200,000
Long-Lived Assets	1,000,000				1,200,000				1,000,000	1,200,000	200,000
Other (geographic location) [Member]
Total revenues									5,800,000	4,600,000	4,500,000
Operating revenues									5,800,000	4,600,000	4,500,000
Long-Lived Assets	$ 300,000				$ 0				$ 300,000	$ 0	$ 0

Condensed Parent Only Financi_2

Condensed Parent Only Financial Statements - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Cash and cash equivalents	$ 471.3	$ 342.3
Income taxes receivable	5.2	0.3
Financial Instruments, Owned, at Fair Value	2,175.2	2,054.8
Deferred tax assets, Net	18	19.8
Property and equipment, net	43.9	42.4
Total assets	9,936.1	7,824.7	$ 6,243.4
Liabilities:
Accounts payable and other accrued liabilities	157.5	145.4
Payables to Customers	3,589.5	3,639.6
Senior secured term loan, net	167.6	0			$ 45.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	714.8	866.5
Total liabilities	9,341.9	7,319.4
INTL FCStone Inc. (Parent Company Only) stockholders’ equity:
Common stock, $0.01 par value. Authorized 30,000,000 shares; 21,297,317 issued and 19,075,360 outstanding at September 30, 2019 and 21,030,497 issued and 18,908,540 outstanding at September 30, 2018	0.2	0.2
Common stock in treasury, at cost - 2,221,957 shares at September 30, 2019 and 2,121,957 shares at September 30, 2018	(50.1)	(46.3)
Additional Paid in Capital	276.8	267.5
Retained earnings	402.1	317
Total INTL FCStone Inc. (Parent Company Only) stockholders’ equity	594.2	505.3
Total liabilities and stockholders' equity	9,936.1	7,824.7
Parent Company [Member]
Cash and cash equivalents	2	1.8	$ 2	$ 1.3
Receivables from subsidiaries	17.6	23.3
Notes receivable, net	2.8	1.8
Income taxes receivable	15.7	14.9
Investment in subsidiaries	399.4	318
Financial Instruments, Owned, at Fair Value	0	4.4
Deferred tax assets, Net	8.2	8.8
Property and equipment, net	26.9	25.9
Other assets	13	7.6
Total assets	486.1	406.5
Liabilities:
Accounts payable and other accrued liabilities	29.4	23
Payables to Customers	0.3	1.7
Payables to lenders under loans	70.4	209.4
Senior secured term loan, net	167.6	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	84.5	59.3
Total liabilities	352.2	293.4
INTL FCStone Inc. (Parent Company Only) stockholders’ equity:
Preferred stock, $.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; 21,297,317 issued and 19,075,360 outstanding at September 30, 2019 and 21,030,497 issued and 18,908,540 outstanding at September 30, 2018	0.2	0.2
Common stock in treasury, at cost - 2,221,957 shares at September 30, 2019 and 2,121,957 shares at September 30, 2018	50.1	46.3
Additional Paid in Capital	276.8	267.5
Retained earnings	(93)	(108.3)
Total INTL FCStone Inc. (Parent Company Only) stockholders’ equity	133.9	113.1
Total liabilities and stockholders' equity	486.1	406.5
Adjustment to Investment in Subs for Equity Method Accounting	$ 495.1	$ 425.3

Condensed Parent Only Financi_3

Condensed Parent Only Financial Statements - Balance Sheet (Parentheticals) (Details) - $ / shares	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Condensed Financial Information Disclosure [Abstract]
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	0
Common stock - par value		$ 0.01	$ 0.01
Common stock - authorized		30,000,000	30,000,000
Common stock - issued		21,297,317	21,030,497
Common stock - outstanding		19,075,360	18,908,540
Treasury stock - shares		2,221,957	2,121,957

Condensed Parent Only Financi_4

Condensed Parent Only Financial Statements - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Condensed Financial Statements, Captions [Line Items]
Interest income									$ 198.9	$ 123.3	$ 69.7
Dividend income from subsidiaries									85.7	41.9	52.7
Operating revenues	$ 286.9	$ 283.4	$ 271.1	$ 264.7	$ 243.2	$ 259.8	$ 260.2	$ 212.6	1,106.1	975.8	784
Interest expense	40.8	42.5	38.4	33	25.3	22.1	19	14.3	154.7	80.7	42.1
Net operating revenues	173.4	165.6	165.2	149	142.4	154.6	154.3	130.3	653.2	581.6	492.6
Non-interest expenses:
Compensation and benefits	105.2	100.9	97.9	89.1	85.4	86.9	88.2	77.2	393.1	337.7	295.7
Clearing and related expenses	45	45.7	42.7	50.1	43.1	49	50.7	36.9	183.5	179.7	136.3
Introducing broker commissions	27.7	29.6	24.8	32.6	32.4	34.1	36.2	31.1	114.7	133.8	113
Trade systems and market information									38.8	34.7	34.4
Occupancy and equipment rental									19.4	16.5	15.2
Professional fees									21	18.1	15.2
Travel and business development									16.2	13.8	13.3
Depreciation and amortization									14	11.6	9.8
Communications									6.6	5.4	5
Bad debts	1	0.5	0.7	0.3	1.2	1.6	0.2	0.1
Other	43.2	42.6	41.1	37.6	35.3	35.2	36.4	33.4	28.4	26.3	25.9
Total non-interest expenses	139.4	144	139.7	124.6	121.9	123.7	124.8	111.7	547.7	482.1	477.4
Other gains	0.1	0	5.4	0	0	2	0	0	5.5	2	0
Loss from continuing operations, before tax	(34.1)	(21.6)	(30.9)	(24.4)	(20.5)	(32.9)	(29.5)	(18.6)	(111)	(101.5)	(15.2)
Income tax benefit	$ (6.9)	$ (5.3)	$ (7.5)	$ (6.2)	$ (4.8)	$ (8.9)	$ (6.8)	$ (25.5)	(25.9)	(46)	(8.8)
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Management fees from affiliates									43.2	40.4	39.1
Trading gains, net									0	0	(1)
Fees and Commissions (Deprecated 2018-01-31)									0.1	0	0
Interest income									1.5	2.3	1.2
Operating revenues									130.5	84.6	92
Interest expense									19.7	15.7	14.4
Net operating revenues									110.8	68.9	77.6
Non-interest expenses:
Compensation and benefits									79.7	73	60.3
Clearing and related expenses									0.9	1.1	1.2
Trade systems and market information									6.4	5.8	6.4
Occupancy and equipment rental									3.4	2.6	2.5
Professional fees									7.3	6.7	3.7
Travel and business development									2.9	2.6	2.7
Non-trading technology and support									12.5	9.1	7.4
Depreciation and amortization									5.2	4.8	3.3
Communications									0.8	0.9	0.9
Management services fee to affiliates									0.5	0	0
Other									5.8	6.9	5.6
Total non-interest expenses									125.4	113.5	94
Other gains									5.3	0	0
Loss from continuing operations, before tax									9.3	44.6	16.4
Income tax benefit									(24.6)	(7.4)	(26.8)
Net loss									15.3	(37.2)	10.4
Adjustment to Investment in Subs for Equity Method Accounting									$ 69.8	$ 92.7	$ (4)

Condensed Parent Only Financi_5

Condensed Parent Only Financial Statements - Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2013	Sep. 30, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Cash paid for interest		$ 153.2	$ 78.9	$ 38
Depreciation and amortization		14	11.6	9.8
Deferred income taxes		(3.7)	(22.3)	9.8
Amortization and extinguishment of debt issuance costs		1.5	1	1.9
Amortization of share-based compensation expense		8.1	6.6	6.3
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ (5.4)
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties		(241.7)	(292.9)	186.3
Notes receivable, net		0.9	6.8	8.3
Income taxes receivable		(4.2)	(1.3)	0.5
Financial instruments owned, at fair value		(113.3)	(308.7)	(125.6)
Other assets		(8.3)	(3.3)	(16)
Accounts payable and other accrued liabilities		6.7	18.6	(19.6)
Payable to clients		(46.8)	520	290.9
Financial instruments sold, not yet purchased, at fair value		(156.1)	153.9	(124.4)
Net cash (used in) provided by operating activities		195.6	(473.6)	1,037.4
Purchase of property and equipment		(11.9)	(12.5)	(16.1)
Net cash used in investing activities		(40.8)	(15.4)	(22.3)
Payments of notes payable		(0.8)	(0.8)	(0.8)
Deferred payments on acquisitions		0	(5.5)	0
Share repurchase		(3.8)	0	0
Debt issuance costs		(3.3)	(0.4)	(0.3)	$ (1.7)
Exercise of stock options		1.2	2.6	3.4
Withholding taxes on stock option exercises		0	(0.8)	0
Income tax benefit on stock options and awards		0	0	0.7
Net cash provided by (used in) financing activities		9.6	120.9	5.7
Cash and cash equivalents at end of period		(471.3)	(342.3)
Income taxes (received) paid, net of cash refunds		24.6	22.2	17.1
Additional consideration payable related to acquisitions		1.8	0	(0.2)
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash paid for interest		18.9	15	8.2
Net loss		15.3	(37.2)	10.4
Depreciation and amortization		5.2	4.8	3.3
Deferred income taxes		(0.6)	(18)	10.7
Amortization and extinguishment of debt issuance costs		1.2	0.7	1.7
Amortization of share-based compensation expense		7.1	6.1	5.5
Business Combination, Bargain Purchase, Gain Recognized, Amount		(5.4)	0	0
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties		0	0	(2.9)
Receivables from subsidiaries, net		0	(0.8)	(0.3)
Due to/from subsidiaries		8.3	(68.6)	27
Notes receivable, net		(1)	2.9	2.1
Income taxes receivable		(0.8)	(6.6)	5.4
Financial instruments owned, at fair value		4.4	(4.4)	1.3
Other assets		(4.4)	(0.7)	7.8
Accounts payable and other accrued liabilities		4.6	8.6	(7.8)
Payable to clients		(1.4)	(0.3)	(2.5)
Financial instruments sold, not yet purchased, at fair value		25.2	34	(10.6)
Net cash (used in) provided by operating activities		58.4	(43.5)	35.5
Capital contribution in affiliates		(75.8)	(4.5)	0
Purchase of property and equipment		(6.2)	(5.9)	(6.1)
Net cash used in investing activities		(82)	(10.4)	(6.1)
Payable to lenders under loans		(138.2)	58.2	13.5
Proceeds from Issuance of Senior Long-term Debt		0	0	(45.5)
Deferred payments on acquisitions		0	(5.5)	0
Share repurchase		(3.8)	0	0
Debt issuance costs		(3)	0	0
Exercise of stock options		1.2	2.6	3.4
Withholding taxes on stock option exercises		0	0.8	0
Income tax benefit on stock options and awards		0	0	0.7
Net cash provided by (used in) financing activities		23.8	53.7	(28.7)
Net (decrease) increase in cash and cash equivalents		0.2	(0.2)	0.7
Cash and cash equivalents at end of period		(2)	(1.8)	(2)		$ (1.3)
Income taxes (received) paid, net of cash refunds		(23.9)	(18.4)	(22.3)
Additional consideration payable related to acquisitions		$ 1.8	$ 0	$ (0.2)