StoneX (SNEX) 10-Q 9 Aug 19 2019 Q3 Quarterly report Financial data

DEI

DEI - shares	9 Months Ended
	Jun. 30, 2019	Aug. 06, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	INTL FCSTONE INC.
Trading Symbol	INTL
Entity Central Index Key	0000913760
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,163,763
Entity Small Business Submission type	false
Entity Emerging Growth Company submission type	false
Entity Current Reporting Status	Yes

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
ASSETS
Cash and cash equivalents	$ 345	$ 342.3
Cash, securities and other assets segregated under federal and other regulations (including $358.4 and $643.3 at fair value at June 30, 2019 and September 30, 2018, respectively)	1,079.4	1,408.7
Collateralized transactions:
Securities purchased under agreements to resell	1,533	870.8
Securities borrowed	1,174.1	225.5
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net (including $380.4 and $517.4 at fair value at June 30, 2019 and September 30, 2018, respectively)	2,661.6	2,234.5
Receivables from customers, net	282.9	288
Notes receivable	4.4	3.8
Income taxes receivable	0.9	0.3
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $370.9 and $123 at June 30, 2019 and September 30, 2018, respectively)	2,429.9	2,054.8
Physical commodities inventory, net (including $169.9 and $156.9 at fair value at June 30, 2019 and September 30, 2018, respectively)	347.8	222.5
Deferred income taxes, net	22.2	19.8
Property and equipment, net	45.7	42.4
Goodwill and intangible assets, net	65.9	59.8
Other assets	62.1	51.5
Total assets	10,054.9	7,824.7
Liabilities:
Accounts payable and other accrued liabilities	144.1	145.4
Payables to:
Customers	3,629	3,639.6
Broker-dealers, clearing organizations and counterparties (including $14.0 and $0 at fair value at June 30, 2019 and September 30, 2018), respectively	190.7	89.5
Debt, Long-term and Short-term, Combined Amount	337.7	355.2
Senior secured term loan, net	169.7	0
Income taxes payable	10.4	8.6
Collateralized transactions:
Securities sold under agreements to repurchase	2,900.7	1,936.7
Securities loaned	1,240.9	277.9
Financial instruments sold, not yet purchased, at fair value	861.2	866.5
Total liabilities	9,484.4	7,319.4
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; 21,251,227 issued and 19,129,270 outstanding at June 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 - 2,121,957 shares at June 30, 2019 and September 30, 2018	(46.3)	(46.3)
Additional paid-in capital	274.2	267.5
Retained earnings	374.9	317
Accumulated other comprehensive loss, net	(32.5)	(33.1)
Total stockholders' equity	570.5	505.3
Total liabilities and stockholders' equity	$ 10,054.9	$ 7,824.7

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parentheticals - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Balance Sheet Parentheticals [Abstract]
Securities and other assets segregated, fair value	$ 235.8	$ 643.3
Dep and rec -b/d - fair value	422.7	517.4
Physical commodities inventory at fair value	202.9	156.9
Collateral that can be sold or repledged	285.5	123
Accounts pay and other accrued - fair value	0	0
Payables to b/d - fair value	$ 15.8	$ 0
Preferred stock - par value	$ 0.01	$ 0.01
Preferred stock - authorized	1,000,000	1,000,000
Preferred stock - issued	0	0
Preferred stock - outstanding	0	0
Common stock - par value	$ 0.01	$ 0.01
Common stock - authorized	30,000,000	30,000,000
Common stock - issued	21,218,132	21,030,497
Common stock - outstanding	19,096,175	18,908,540
Treasury stock - shares	2,121,957	2,121,957

Condensed Consolidated Income S

Condensed Consolidated Income Statements - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Revenues	$ 7,873,000,000	$ 7,118,300,000	$ 21,617,400,000	$ 21,543,900,000
Cost of sales of physical commodities	7,589,600,000	6,858,500,000	20,798,200,000	20,811,300,000
Operating revenues	283,400,000	259,800,000	819,200,000	732,600,000
Transaction-based clearing expenses	45,700,000	49,000,000	138,500,000	136,600,000
Introducing broker commissions	29,600,000	34,100,000	87,000,000	101,400,000
Interest expense	42,500,000	22,100,000	113,900,000	55,400,000
Net operating revenues	165,600,000	154,600,000	479,800,000	439,200,000
Compensation and other expenses:
Compensation and benefits	100,900,000	86,900,000	287,900,000	252,300,000
Trading systems and market information	9,800,000	8,600,000	28,500,000	25,700,000
Occupancy and equipment rental	5,000,000	4,200,000	14,400,000	12,500,000
Professional fees	5,800,000	4,800,000	16,100,000	13,400,000
Travel and business development	4,000,000	3,700,000	11,800,000	10,200,000
Non-trading technology and support	5,800,000	3,800,000	15,000,000	10,300,000
Depreciation and amortization	3,500,000	2,800,000	9,600,000	8,400,000
Communications	1,600,000	1,300,000	4,900,000	4,100,000
Provision for Doubtful Accounts	500,000	1,600,000	1,500,000	1,900,000
(Recovery) bad debt on physical coal	0	0	(2,400,000)	1,000,000
Other	7,100,000	6,000,000	21,000,000	20,400,000
Total compensation and other expenses	144,000,000	123,700,000	408,300,000	360,200,000
Other gain	0	2,000,000	5,400,000	2,000,000
Income before tax	21,600,000	32,900,000	76,900,000	81,000,000
Income tax expense	5,300,000	8,900,000	19,000,000	41,200,000
Net income	$ 16,300,000	$ 24,000,000	$ 57,900,000	$ 39,800,000
Earnings per share:
Basic	$ 0.85	$ 1.27	$ 3.04	$ 2.10
Diluted	$ 0.84	$ 1.25	$ 2.99	$ 2.06
Weighted-average number of common shares outstanding:
Basic	18,781,401	18,597,165	18,731,203	18,524,846
Diluted	19,011,526	18,976,898	19,003,720	18,876,259
Interest Income [Member]
Revenues:
Revenues	$ 53,200,000	$ 33,700,000	$ 146,400,000	$ 85,600,000
Other Income [Member]
Revenues:
Revenues	20,700,000	18,400,000	58,900,000	53,400,000
Commission and Clearing Fees [Member]
Revenues:
Revenues	97,500,000	105,100,000	282,100,000	298,000,000
Principal or Proprietary Transactions [Member]
Revenues:
Revenues	102,300,000	94,900,000	305,400,000	270,500,000
Sales [Member]
Revenues:
Revenues	$ 7,599,300,000	$ 6,866,200,000	$ 20,824,600,000	$ 20,836,400,000

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ 16.3	$ 24	$ 57.9	$ 39.8
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustment	0.3	(4.9)	0.6	(8.7)
Other comprehensive (loss) income	0.3	(4.9)	0.6	(8.7)
Comprehensive income	$ 16.6	$ 19.1	$ 58.5	$ 31.1

Condensed Consolidated Cash Flo

Condensed Consolidated Cash Flows Statements - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Assets acquired	$ 40.9	$ 0
Escrow deposits related to acquisitions	2.5	0
Liabilities assumed	(7.7)	0
Cash flows from operating activities:
Net income	57.9	39.8
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	9.6	8.4
Bad debts	1.5	1.9
(Recovery) bad debt on physical coal	(2.4)	1
Deferred income taxes	0.3	19.7
Amortization of debt issuance costs	1.2	0.8
Amortization of stock-based compensation	5.9	4.9
Bargain purchase gain on acquisition	(5.4)	0
Changes in operating assets and liabilities, net:
Securities and other assets segregated under federal and other regulations	584.4	(657)
Securities purchased under agreements to resell	(662.2)	(363.4)
Securities borrowed	(948.6)	(89.7)
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	(238.7)	(622)
Receivables from clients, net	5.9	22.5
Notes receivable, net	(0.6)	(0.4)
Income taxes receivable	(0.6)	(0.8)
Financial instruments owned, at fair value	(368)	(254)
Physical commodities inventory, net	(115.5)	(89)
Other assets	(7.8)	1.5
Accounts payable and other accrued liabilities	(4)	1.5
Payables to customers	(7.3)	319.7
Payables to broker-dealers, clearing organizations and counterparties	100.9	10
Income taxes payable	1.8	6.4
Securities sold under agreements to repurchase	964	206
Securities loaned	963	93.2
Financial instruments sold, not yet purchased, at fair value	(9.7)	294.2
Net cash used in operating activities	325.6	(1,044.8)
Cash flows from investing activities:
Cash paid for acquisitions, net	(28)	0
Purchase of property and equipment	(10.3)	(9.3)
Net cash used in investing activities	(38.3)	(9.3)
Cash flows from financing activities:
Net change in payable to lenders under loans	(16.9)	131
Proceeds from issuance of senior secured term loan	175	0
Repayment of senior unsecured notes	(4.4)	0
Payments of note payable	(0.6)	(0.6)
Deferred payments on acquisitions	0	(5.5)
Debt issuance costs	(3.3)	(0.4)
Proceeds from Stock Options Exercised	0.8	2.6
Withholding taxes on stock option exercises	0	(0.8)
Net cash provided by financing activities	150.6	126.3
Effect of exchange rates on cash and cash equivalents	0.6	3
Net (decrease) increase in cash and cash equivalents	438.5	(924.8)
Cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period	2,628.6	1,676.6
Supplemental disclosure of cash flow information:
Cash paid for interest	110.1	54.2
Income taxes paid, net of cash refunds	17.5	15.8
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	2.7	0
Total net assets acquired	$ 33.2	$ 0

Condensed Consolidated Cash F_2

Condensed Consolidated Cash Flows Statements Reconciliation of Cash, Segregated Cash, Cash Equivalents, and Segregated Cash Equivalents - USD ($) $ in Millions	Jun. 30, 2019	Jun. 30, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 345	$ 347.8
Cash segregated under federal and other regulations(1)	721	537.2
Securities segregated under federal and other regulations(1)	300	0
Cash segregated and deposited with or pledged to exchange-clearing organizations and other futures commissions merchants	1,223.8	738.1
Securities segregated and pledged to exchange-clearing organizations(2)	39.2	53.5
Cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period	$ 2,628.6	$ 1,676.6

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Stockholders' 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 as of beginning of period at Sep. 30, 2017	$ 449.9	$ 0.2	$ 46.3	$ 259	$ 261.5	$ (24.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39.8				39.8
Other comprehensive loss	(8.7)					(8.7)
Stock Issued During Period, Value, Stock Options Exercised	1.8			1.8
Share-based Compensation	4.9			4.9
Balances as of end of period at Jun. 30, 2018	487.7	0.2	46.3	265.7	301.3	(33.2)
Balances as of beginning of period at Mar. 31, 2018	466.6	0.2	46.3	263.7	277.3	(28.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24				24
Other comprehensive loss	(4.9)					(4.9)
Stock Issued During Period, Value, Stock Options Exercised	0.3			0.3
Share-based Compensation	1.7			1.7
Balances as of end of period at Jun. 30, 2018	487.7	0.2	46.3	265.7	301.3	(33.2)
Balances as of beginning 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	57.9				57.9
Other comprehensive loss	0.6					0.6
Stock Issued During Period, Value, Stock Options Exercised	0.8			0.8
Share-based Compensation	5.9			5.9
Balances as of end of period at Jun. 30, 2019	570.5	0.2	(46.3)	274.2	374.9	(32.5)
Balances as of beginning of period at Mar. 31, 2019	551.8	0.2	46.3	272.1	358.6	(32.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16.3				16.3
Other comprehensive loss	0.3					0.3
Share-based Compensation	2.1			2.1
Balances as of end of period at Jun. 30, 2019	$ 570.5	$ 0.2	$ (46.3)	$ 274.2	$ 374.9	$ (32.5)

Basis of Presentation and Conso

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Notes)	9 Months Ended
	Jun. 30, 2019
Basis of Presentation and Consolidation [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Basis of Presentation and Consolidation and Accounting Standards Adopted INTL FCStone Inc. , a Delaware corporation, and its consolidated subsidiaries (collectively “INTL” or “the Company”), is a diversified global financial services organization providing execution, risk management and advisory services, market intelligence, and clearing services across asset classes and markets around the world. The Company’s services include comprehensive risk management advisory services for commercial clients; execution of listed futures and options on futures contracts on all major commodity exchanges; structured over-the-counter (“OTC”) products in a wide range of commodities; physical trading and hedging of precious metals and select other commodities; trading of more than 140 foreign currencies; market-making in international equities; fixed income; debt origination and asset management. The Company provides these services to a diverse group of more than 20,000 predominantly wholesale organizations located throughout the world, including producers, processors and end-users of nearly all widely-traded physical commodities to manage their risks and enhance margins; to commercial counterparties who are end-users of the Company’s products and services; to governmental and non-governmental organizations; and to commercial banks, brokers, institutional investors and major investment banks. Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated balance sheet as of September 30, 2018 , which has been derived from the audited consolidated balance sheet of September 30, 2018 , and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to those rules and regulations. The Company believes that the disclosures made are adequate to make the information presented not misleading. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X. Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Form 10-K for the fiscal year ended September 30, 2018 filed with the SEC. These condensed consolidated financial statements include the accounts of INTL FCStone Inc. and all other entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. The Company’s fiscal year end is September 30, and the fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to fiscal years and fiscal interim periods. The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurement for financial instruments and investments, revenue recognition, the provision for bad debts, valuation of inventories, valuation of goodwill and intangible assets, incomes taxes, and contingencies. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. In the condensed consolidated income statements, the total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. The subtotal ‘operating revenues’ in the condensed consolidated income statements is calculated by deducting cost of sales of physical commodities from total revenues. The subtotal ‘net operating revenues’ in the condensed consolidated income statements is calculated as operating revenues less transaction-based clearing expenses, introducing broker commissions and interest expense. Transaction-based clearing expenses represent variable expenses paid to executing brokers, exchanges, clearing organizations and banks in relation to transactional volumes. Introducing broker commissions include commission paid to non-employee third parties that have introduced 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. Reclassifications During the three and nine months ended June 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 condensed consolidated income statements for the three and nine months ended June 30, 2018. For the three and nine months ended June 30, 2018, brokerage related revenues of $8.5 million and $26.4 million , respectively, were reclassified from ‘trading 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 condensed 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. Accounting Standards Adopted On October 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“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 three or nine months ended June 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 ASU 2016-15, Statements of Cash Flows (“Topic 230”): 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 condensed consolidated financial statements and related disclosures. On October 1, 2018, the Company adopted FASB Accounting Standards Update (“ASU”) 2016-18, Statements of Cash Flows (“Topic 230”): 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 condensed 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 exchange-clearing organizations 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 condensed consolidated statements of cash flows. In May 2017, the FASB issued ASU No. 2017- 09, Scope of Modification Accounting (“Topic 718”), 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 condensed consolidated financial statements and related disclosures.

Revenue from Contracts with Cli

Revenue from Contracts with Clients (Notes)	9 Months Ended
	Jun. 30, 2019
Revenue from Contract with Clients [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 1.5% and 1.7% of the Company’s total revenues for the three months ended June 30, 2019 and 2018 , respectively, and approximately 1.6% of the Company’s total revenues for the nine months ended June 30, 2019 and 2018 . The Company’ revenues from contracts with clients subject to Topic 606 represent approximately 41.7% and 47.6% of the Company’s operating revenues for the three months ended June 30, 2019 and 2018 , respectively, and approximately 41.6% and 48.0% of the Company’s operating revenues for the nine months ended June 30, 2019 and 2018 , respectively. This includes all of the Company’s commission and clearing fees and consulting, management, and account fees revenues. Revenues within the scope of Topic 606 are presented within ‘Commission and clearing fees’ and ‘Consulting, management, and account fees’ on the condensed 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 condensed 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 three and nine months ended June 30, 2019 and 2018 (in millions): Three Months Ended June 30, Nine Months Ended June 30, 2019 2018 2019 2018 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 40.4 $ 45.0 $ 110.7 $ 123.6 OTC derivative brokerage 7.7 7.3 23.9 23.1 Equities and fixed income 4.3 2.7 11.1 8.3 Mutual funds 1.6 1.5 6.1 5.6 Insurance and annuity products 2.1 1.5 5.1 4.5 Other 0.3 0.6 1.0 1.2 Total sales-based commission 56.4 58.6 157.9 166.3 Trailing: Mutual funds 3.1 3.2 9.3 9.8 Insurance and annuity products 3.6 3.7 10.7 11.0 Total trailing commission 6.7 6.9 20.0 20.8 Clearing fees 30.3 34.2 89.7 93.7 Trade conversion fees 1.3 1.6 6.2 5.4 Other 2.8 3.8 8.3 11.8 Total commission and clearing fees: 97.5 105.1 282.1 298.0 Consulting, management, and account fees: Underwriting fees 0.2 0.2 0.7 1.5 Asset management fees 7.2 6.4 19.4 18.9 Advisory and consulting fees 5.1 4.9 14.8 14.3 Sweep program fees 4.2 3.3 12.1 8.2 Client account fees 2.6 2.9 7.8 8.6 Other 1.4 0.7 4.1 1.9 Total consulting, management, and account fees 20.7 18.4 58.9 53.4 Total revenues from contracts with clients $ 118.2 $ 123.5 $ 341.0 $ 351.4 Method of revenue recognition: Point-in-time $ 95.0 $ 102.0 $ 274.7 $ 289.2 Time elapsed 23.2 21.5 66.3 62.2 Total revenues from contracts with clients 118.2 123.5 341.0 351.4 Other sources of revenues Physical precious metals trading 7,327.8 6,613.0 19,944.2 20,176.5 Physical agricultural and energy product trading 271.5 253.2 880.4 659.9 Principal gains, net 102.3 94.9 305.4 270.5 Interest income 53.2 33.7 146.4 85.6 Total revenues $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9 Primary geographic region: United States $ 474.8 $ 431.9 $ 1,458.4 $ 1,159.9 Europe 77.8 48.5 184.9 141.5 South America 15.3 16.7 39.2 48.4 Middle East and Asia 7,303.8 6,620.0 19,929.7 20,191.0 Other 1.3 1.2 5.2 3.1 Total revenues $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9 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. Such agreements are generally for one year periods, but are generally cancelable by either party upon providing thirty days’ written notice to the other party and the amounts 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 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, 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. 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)	9 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings per Share The Company presents basic and diluted earnings per share (“EPS”) using the two-class method which requires all outstanding unvested share-based payment awards that contain rights to non-forfeitable dividends and therefore participate in undistributed earnings with common stockholders be included in computing earnings per share. Under the two-class method, net 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 earnings per share computations for the periods presented below. Three Months Ended June 30, Nine Months Ended June 30, (in millions, except share amounts) 2019 2018 2019 2018 Numerator: Net income $ 16.3 $ 24.0 $ 57.9 $ 39.8 Less: Allocation to participating securities (0.3 ) (0.3 ) (1.0 ) (0.6 ) Net income allocated to common stockholders $ 16.0 $ 23.7 $ 56.9 $ 39.2 Denominator: Weighted average number of: Common shares outstanding 18,781,401 18,597,165 18,731,203 18,524,846 Dilutive potential common shares outstanding: Share-based awards 230,125 379,733 272,517 351,413 Diluted weighted-average common shares 19,011,526 18,976,898 19,003,720 18,876,259 The dilutive effect of share-based awards is reflected in diluted earnings per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense required under the Compensation – Stock Compensation Topic of the ASC. Options to purchase 1,209,943 and 76,587 shares of common stock for the three months ended June 30, 2019 and 2018 , respectively, and options to purchase 835,441 and 147,640 shares of common stock for the nine months ended June 30, 2019 and 2018 , respectively, were excluded from the calculation of diluted earnings per share as they would have been anti-dilutive

Assets and Liabilities, at Fair

Assets and Liabilities, at Fair Value (Notes)	9 Months Ended
	Jun. 30, 2019
Assets and Liabilities, at Fair Value [Abstract]
Fair Value Disclosures [Text Block]	Assets and Liabilities, at Fair Value Fair value is defined by U.S. GAAP as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between willing market participants on the measurement date. Fair value is a market-based measure considered from the perspective of a market participant rather than an entity-specific measure. Therefore, even when market assumptions are not readily available, the Company is required to develop a set of assumptions that reflect those that market participants would use in pricing the asset or liability at the measurement date. The Company uses prices and inputs that are current as of the measurement date, including periods of market dislocation. In periods of market dislocation, the observability of prices and inputs may be reduced for many securities. This condition could cause a security to be reclassified to a lower level within the fair value hierarchy. The Company has designed independent price verification controls and periodically performs such controls to ensure the reasonableness of such values. In accordance with FASB ASC 820, Fair Value Measurement, the Company groups its assets and liabilities measured at fair value in three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. These levels are: Level 1 - Valuation is based upon unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 1 consists of financial assets and liabilities whose fair values are estimated using quoted market prices. Level 2 - Valuation is based upon quoted prices for identical or similar assets or liabilities in markets that are less active, that is, markets in which there are few transactions for the asset or liability that are observable for substantially the full term. Included in Level 2 are those financial assets and liabilities for which fair values are estimated using models or other valuation methodologies. These models are primarily industry-standard models that consider various observable inputs, including time value, yield curve, volatility factors, observable current market and contractual prices for the underlying financial instruments, as well as other relevant economic measures. Level 3 - Valuation is based on prices or valuation techniques that require an input that is both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Level 3 comprises financial assets and liabilities whose fair value is estimated based on internally developed models or methodologies utilizing significant inputs that are not readily observable from objective sources. The Company had no assets or liabilities classified within Level 3 of the fair value hierarchy as of June 30, 2019 and September 30, 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 participants. 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 principally 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 to these trades. The Company has assessed the nature of these deposits and used its discretion to adjust each based on the underlying credit considerations for the counterparty and determined that the collateral deposits minimize the exposure to counterparty credit risk in the evaluation of the fair value of OTC instruments as determined by a market participant. Fair value of financial and nonfinancial assets and liabilities that are carried on the Condensed Consolidated Balance Sheets at fair value on a recurring basis Cash and cash equivalents reported at fair value on a recurring basis includes certificates of deposit and demand deposits, 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 include the value of pledged investments, primarily U.S. Treasury obligations and foreign government obligations. These balances also include the fair value of exchange-traded options on futures and OTC derivative financial instruments. Financial instruments owned and sold, not yet purchased include the fair value of equity securities, which includes common, preferred, and foreign ordinary shares, ADRs, 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, OTC derivative financial instruments, commodities warehouse receipts, exchange firm common stock, and mutual funds and investments in managed funds. Cash equivalents, debt and equity securities, commodities warehouse receipts, physical commodities inventory, and derivative financial instruments are carried at fair value, on a recurring basis, and are classified and disclosed into three levels in the fair value hierarchy. Except as disclosed in Note 7 , the Company did not have any fair value adjustments for assets or liabilities measured at fair value on a non-recurring basis as of June 30, 2019 and September 30, 2018 . The following section describes the valuation methodologies used by the Company to measure classes of financial and non-financial assets and liabilities at fair value and specifies the level within the fair value hierarchy where various financial and non-financial assets and liabilities 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 held by a regulated broker-dealer subsidiary, exchange firm common stock, mutual funds and investments in managed funds, as well as exchange traded options on futures contracts. 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 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 vendors. 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 the 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 sources are included within either Level 1 or Level 2 of the fair value hierarchy based upon the observability of the inputs used and the level of activity in the market. The fair value estimates presented herein are based on pertinent information available to management as of June 30, 2019 and September 30, 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 condensed 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 June 30, 2019 by level in the fair value hierarchy. June 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting and Collateral (1) Total Assets: Unrestricted cash equivalents - certificates of deposit $ 6.5 $ — $ — $ — $ 6.5 Commodities warehouse receipts 58.6 — — — 58.6 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 358.4 — — — 358.4 U.S. Treasury obligations 484.2 — — — 484.2 "To be announced" (TBA) and forward settling securities — 6.1 — (0.5 ) 5.6 Foreign government obligations 10.5 — — — 10.5 Derivatives 3,809.1 8.6 — (3,937.6 ) (119.9 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 4,303.8 14.7 — (3,938.1 ) 380.4 Equity securities 79.8 8.0 — — 87.8 Corporate and municipal bonds — 111.6 — — 111.6 U.S. Treasury obligations 248.0 — — — 248.0 U.S. government agency obligations — 465.1 — — 465.1 Foreign government obligations 4.5 — — — 4.5 Agency mortgage-backed obligations — 1,148.7 — — 1,148.7 Asset-backed obligations — 30.4 — — 30.4 Derivatives 2.0 587.9 — (343.7 ) 246.2 Commodities leases — 38.1 — (11.3 ) 26.8 Commodities warehouse receipts 39.6 — — — 39.6 Exchange firm common stock 11.7 — — — 11.7 Mutual funds and other 9.5 — — — 9.5 Financial instruments owned 395.1 2,389.8 — (355.0 ) 2,429.9 Physical commodities inventory 22.3 147.6 — — 169.9 Total assets at fair value $ 5,086.1 $ 2,552.1 $ — $ (4,293.1 ) $ 3,345.1 Liabilities: TBA and forward settling securities — 8.4 — (0.5 ) 7.9 Derivatives 4,005.3 26.7 — (4,025.9 ) 6.1 Payables to broker-dealers, clearing organizations and counterparties 4,005.3 35.1 — (4,026.4 ) 14.0 Equity securities 50.7 1.1 — — 51.8 Foreign government obligations 2.7 — — — 2.7 Corporate and municipal bonds — 29.2 — — 29.2 U.S. Treasury obligations 479.9 — — — 479.9 U.S. government agency obligations — 53.0 — — 53.0 Derivatives — 685.3 — (486.3 ) 199.0 Commodities leases — 55.4 — (9.8 ) 45.6 Financial instruments sold, not yet purchased 533.3 824.0 — (496.1 ) 861.2 Total liabilities at fair value $ 4,538.6 $ 859.1 $ — $ (4,522.5 ) $ 875.2 (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 is included in that level. The following table sets forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2018 by level in the fair value hierarchy. September 30, 2018 (in millions) Level 1 Level 2 Level 3 Netting and Collateral (1) Total Assets: Unrestricted cash equivalents - certificates 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 ) — Payables 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 is 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 condensed consolidated income statements. Additional disclosures about the fair value of financial instruments that are not carried on the Condensed Consolidated Balance Sheets at fair value Many, but not all, of the financial instruments that the Company holds are recorded at fair value in the Condensed Consolidated Balance Sheets. The following represents financial instruments in which the ending balance at June 30, 2019 and September 30, 2018 was not carried at fair value in accordance with U.S. GAAP on the Condensed Consolidated Balance Sheets: Short-term financial instruments : The carrying value of short-term financial instruments, including cash and cash equivalents, cash segregated under federal and other regulations, securities purchased under agreements to re-sell and securities sold under agreements to re-purchase, and securities borrowed and loaned are recorded at amounts that approximate the fair value of these instruments due to their short-term nature and level of collateralization. These financial instruments generally expose the Company 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 equity securities, U.S. Treasury obligations, U.S. government agency obligations, agency mortgage-backed obligations, and asset-backed obligations. Receivables and other assets : Receivables from broker-dealers, clearing organizations, and counterparties, receivables from clients, net, notes receivables, 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 : Payables 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. Lenders under loans : Payables to lenders under loans carry variable rates of interest and are relatively short-term in duration and, thus, approximate fair value and are classified as Level 2 under the fair value hierarchy. Senior secured term loan : 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)	9 Months Ended
	Jun. 30, 2019
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk The Company is party to certain financial instruments with off-balance sheet risk in the normal course of its business. The Company has sold financial instruments that it does not currently own and will therefore be obliged to purchase such financial instruments at a future date. The Company has recorded these obligations in the condensed consolidated financial statements as of June 30, 2019 and September 30, 2018 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 June 30, 2019 . The total financial instruments sold, not yet purchased of $861.2 million and $866.5 million as of June 30, 2019 and September 30, 2018 , respectively, includes $199.0 million and $193.4 million for derivative contracts, respectively, which represented a liability to the Company based on their fair values as of June 30, 2019 and September 30, 2018 . Derivatives The Company utilizes derivative products in its trading capacity as a dealer in order to satisfy client needs and mitigate risk. The Company manages risks from both derivatives and non-derivative cash instruments on a consolidated basis. The risks of derivatives should not be viewed in isolation, but in aggregate with the Company’s other trading activities. The majority of the Company’s derivative positions are included in the condensed consolidated balance sheets in ‘Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net’, ‘Financial instruments owned, at fair value’, ‘Financial instruments 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 June 30, 2019 and September 30, 2018 . Assets represent net unrealized gains and liabilities represent net unrealized losses. June 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 $ 1,577.7 $ 1,610.4 $ 2,455.7 $ 2,499.3 OTC commodity derivatives 241.9 380.8 207.0 369.9 Exchange-traded foreign exchange derivatives 76.9 73.1 49.8 37.2 OTC foreign exchange derivatives 334.2 308.7 302.5 303.9 Exchange-traded interest rate derivatives 1,200.7 1,417.6 449.3 478.7 OTC interest rate derivatives 20.4 22.5 24.8 25.9 Exchange-traded equity index derivatives 955.8 904.2 4,541.8 4,794.0 TBA and forward settling securities 6.1 8.4 5.0 2.1 Gross fair value of derivative contracts 4,413.7 4,725.7 8,035.9 8,511.0 Impact of netting and collateral (4,281.8 ) (4,512.7 ) (8,118.5 ) (8,317.6 ) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net' $ (114.3 ) $ (268.7 ) Total fair value included in 'Financial instruments owned, at fair value' $ 246.2 $ 186.1 Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties' $ 14.0 $ — Fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 199.0 $ 193.4 (1) As of June 30, 2019 and September 30, 2018 , the Company’s derivative contract volume for open positions were approximately 12.9 million and 10.6 million contracts, respectively. The Company’s derivative contracts are principally held in its Commercial Hedging and Clearing and Execution Services segments. The Company assists its Commercial Hedging segment 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 offsetting the client’s transaction simultaneously with one of the Company’s trading counterparties or with a similar but not identical exchange-traded position. The risk mitigation of these offsetting trades is not within the documented hedging designation requirements of Topic 815. These derivative contracts are traded along with cash transactions because of the integrated nature of the markets for these products. The Company manages the risks associated with derivatives on an aggregate basis along with the risks associated with its proprietary trading and market-making activities in cash instruments as part of its firm-wide risk management policies. In particular, the risks related to derivative positions may be partially offset by inventory, unrealized gains in inventory or cash collateral paid or received. The Company has derivative instruments, which consist of TBA securities and forward settling transactions that are used to manage risk exposures in the trading inventory of the Company’s domestic institutional fixed income business. The fair value on these transactions are recorded in ‘deposits with and receivables from or payables to broker-dealers, clearing organizations and counterparties, net’. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘principal gains, net’. As of June 30, 2019 and September 30, 2018 , these transactions are summarized as follows: June 30, 2019 September 30, 2018 (in millions) 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, net and related notional amounts $ 3.6 $ 1,256.6 $ 1.2 $ 721.5 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (0.2 ) $ 254.5 $ (0.6 ) $ 293.2 Unrealized gain on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 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 $ 0.3 $ (290.6 ) $ — $ — Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (6.9 ) $ (2,132.1 ) $ — $ — Unrealized loss on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 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, net 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 $ (1.3 ) $ 492.7 $ — $ — Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ 2.2 $ (345.7 ) $ 0.1 $ (427.2 ) (1) The notional amounts of these instruments reflect the extent of the Company's involvement in TBA and forward settling securities and do not represent risk of loss due to counterparty non-performance. The following table sets forth the Company’s net gains from derivative contracts for the three and nine months ended June 30, 2019 and 2018 in accordance with Topic 815. The net gains set forth below are included in ‘Cost of sales of physical commodities’ and ‘principal gains, net’ in the condensed consolidated income statements. Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Commodities $ 19.5 $ 38.1 $ 63.6 $ 71.9 Foreign exchange 1.6 2.9 5.3 7.7 Interest rate and equity (0.6 ) 0.5 (3.2 ) 1.1 TBA and forward settling securities (8.0 ) — (6.7 ) 10.3 Net gains from derivative contracts $ 12.5 $ 41.5 $ 59.0 $ 91.0 Credit Risk In the normal course of business, the Company purchases and sells financial instruments, commodities and foreign currencies as either a 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, commodity, 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 and/or position limits based upon a review of the counterparties’ financial condition and credit ratings. The Company monitors collateral levels on a daily basis for compliance with regulatory and internal guidelines and requests changes in collateral levels as appropriate. The Company is a party to financial instruments in the normal course of its business through client and proprietary trading accounts in exchange-traded and OTC derivative instruments. These instruments are primarily the result of the execution of orders for commodity futures, options on futures, OTC swaps and options and spot and forward foreign currency contracts on behalf of its 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 exchanges 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 June 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. Generally, these exposures to both clients and counterparties are subject to master netting or client agreements which reduce the exposure to the Company. Derivative financial instruments involve varying degrees of off-balance sheet market risk whereby changes in the fair values of underlying financial instruments may result in changes in the fair value of the financial instruments in excess of the amounts reflected in the condensed consolidated balance sheets. Exposure to market risk is influenced by a number of factors, including the relationships between the financial instruments and the Company’s positions, as well as the volatility and liquidity in the markets in which the financial instruments are traded. The principal risk components of financial instruments include, among other things, interest rate volatility, the duration of the underlying instruments and changes in foreign exchange rates. The Company attempts to manage its exposure to market risk through various techniques. Aggregate market limits have been established and market risk measures are routinely monitored against these limits.

Receivables From Customers, Net

Receivables From Customers, Net and Notes Receivable, Net (Notes)	9 Months Ended
	Jun. 30, 2019
Receivables from customers and notes receivable, net [Abstract]
Financing Receivables [Text Block]	Allowance for Doubtful Accounts The allowance for doubtful accounts related to receivables from clients was $11.2 million and $10.2 million as of June 30, 2019 and September 30, 2018 , respectively. The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $45.6 million and $48.0 million as of June 30, 2019 and September 30, 2018 , respectively. During the three months ended June 30, 2019 , the Company recorded bad debt expense of $0.5 million . The bad debt expense was primarily related to agricultural and metals OTC client trading account deficits in the Company’s Commercial Hedging segment. During the three months ended June 30, 2018, the Company recorded bad debt expense of $1.6 million . The bad debt expense was primarily related to agricultural OTC client trading account deficits in the Company’s Commercial Hedging segment partially offset by the recovery of a precious metals client trading account deficit in the Company’s Physical Commodities segment. During the nine months ended June 30, 2019 , the Company recorded bad debt expense of $1.5 million . The bad debt expense was primarily related to agricultural and metals OTC client trading account deficits in the Company’s Commercial Hedging. Additionally, during the nine months ended June 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 2017. The settlement amount paid was less than the accrued liability for the transactions recorded during fiscal 2017 and fiscal 2018, and accordingly the Company recorded a recovery on the bad debt on physical coal of $2.4 million in the nine months ended June 30, 2019 . During the nine months ended June 30, 2018, the Company recorded bad debt expense of $1.9 million primarily related to agricultural OTC client trading account deficits in the Company’s Commercial Hedging segment. Additionally, within the Company’s Physical Commodities segment, the Company recorded an additional provision of $1.0 million related to the bad debt on physical coal for amounts due to the Company from a coal supplier for demurrage and other charges related to contracts with delivery dates subsequent to September 30, 2017.

Physical Commodities Inventory

Physical Commodities Inventory (Notes)	9 Months Ended
	Jun. 30, 2019
Physical Commodities Inventory [Abstract]
Inventory Disclosure [Text Block]	Physical Commodities Inventory The Company’s inventories consist of finished physical commodities. Inventories by component of the Company’s Physical Commodities segment are shown below. (in millions) June 30, September 30, Physical Ag & Energy (1) $ 147.6 $ 114.7 Precious metals - held by broker-dealer subsidiary (2) 22.3 42.1 Precious metals - held by non-broker-dealer subsidiaries (3) 177.9 65.7 Physical commodities inventory $ 347.8 $ 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 condensed consolidated income statements. The agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. Physical Ag & Energy also maintains energy related inventory which is valued at the lower of cost or net realizable value. (2) Precious metals held by the Company’s subsidiary, INTL FCStone Ltd, a United Kingdom based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ on the condensed consolidated income statements, in accordance with U.S. GAAP accounting requirements for broker-dealers. (3) Precious metals inventory held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value. The Company has recorded lower of cost or net realizable adjustments for certain precious metals inventory of $2.6 million and $0.4 million as of June 30, 2019 and September 30, 2018, respectively. The adjustments are included in ‘cost of sales of physical commodities’ in the condensed consolidated income statements.

Goodwill (Notes)

Goodwill (Notes)	9 Months Ended
	Jun. 30, 2019
Goodwill [Abstract]
Goodwill Disclosure [Text Block]	Goodwill The carrying value of goodwill is allocated to the Company’s operating segments as follows: (in millions) June 30, September 30, Commercial Hedging $ 30.3 $ 30.3 Global Payments 6.9 8.9 Physical Commodities 9.5 2.4 Securities 7.0 6.8 Goodwill $ 53.7 $ 48.4 The Company recorded zero and $1.3 million in foreign exchange revaluation adjustments on goodwill for the nine months ended June 30, 2019 and 2018 , respectively. The Company recorded additional goodwill of $0.2 million during the nine months ended June 30, 2019 within the Securities operating segment related to the acquisition of Carl Kliem S.A. The Company also recorded a reduction to goodwill of $2.0 million during the nine months ended June 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 17 . The Company also recorded additional goodwill of $7.1 million during the nine months ended June 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 17 .

Intangible Assets - (Notes)

Intangible Assets - (Notes)	9 Months Ended
	Jun. 30, 2019
Intangible Assets [Abstract]
Intangible Assets Disclosure [Text Block]	Intangible Assets During the nine months ended June 30, 2019, the Company recorded indefinite-lived intangible assets not subject to amortization of $2.7 million related to the joint venture transaction discussed in Note 17 . 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): June 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 $ 2.7 $ (2.6 ) $ 0.1 $ 2.7 $ (2.6 ) $ 0.1 Client base 21.4 (12.0 ) 9.4 21.4 (10.1 ) 11.3 Total intangible assets subject to amortization: $ 24.1 $ (14.6 ) $ 9.5 $ 24.1 $ (12.7 ) $ 11.4 Intangible assets not subject to amortization: Business licenses $ 2.7 $ — $ 2.7 $ — $ — $ — Total intangible assets not subject to amortization: $ 2.7 $ — $ 2.7 $ — $ — $ — Total intangible assets $ 26.8 $ (14.6 ) $ 12.2 $ 24.1 $ (12.7 ) $ 11.4 Amortization expense related to intangible assets was $1.9 million and $1.7 million for the nine months ended June 30, 2019 and 2018 , respectively. Amortization expense related to intangible assets was $0.6 million for the three months ended June 30, 2019 and 2018 . As of June 30, 2019 , the estimated future amortization expense was as follows: (in millions) Fiscal 2019 (remaining three months) $ 0.7 Fiscal 2020 2.2 Fiscal 2021 2.2 Fiscal 2022 1.0 Fiscal 2023 and thereafter 3.4 $ 9.5

Credit Facilities (Notes)

Credit Facilities (Notes)	9 Months Ended
	Jun. 30, 2019
Credit Facilities [Abstract]
Debt Disclosure [Text Block]	Credit Facilities 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 $703.1 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: • $345.6 million facility available to INTL FCStone Inc. for general working capital requirements. 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 . The amended facility is comprised of a $175.0 million revolving credit facility and a $175.0 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. Amounts repaid on the Term Loan may not be reborrowed. Both the revolving credit facility and the Term Loan are subject to variable rates of interest equal to the Eurodollar Rate, as defined, or the Base Rate, as defined. Unused portions of the revolving loan facility will continue to require a commitment fee on unused borrowings, as defined in the agreement. In connection with the amendment, the Company paid $3.1 million in rating agency fees, arrangement fees, commitment fees, and other deferred financing costs. These deferred financing costs are being amortized over the 36 month term of the amended credit facility. • $75.0 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Financial Inc., for short-term funding of margin to exchange-clearing organizations. The facility is subject to annual review and guaranteed by INTL FCStone Inc. • $232.5 million facility available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC, for financing traditional commodity financing arrangements and commodity repurchase agreements. The facility is guaranteed by INTL FCStone Inc. • $50.0 million facility available to the Company’s wholly owned subsidiary, INTL FCStone Ltd, for short-term funding of margin to exchange-clearing organizations. The facility is subject to annual review and is guaranteed by INTL FCStone Inc. The facility was amended on May 8, 2019 to increase the committed amount from $25.0 million to $50.0 million . Uncommitted Credit Facilities The Company has a secured, uncommitted loan facility, under which INTL FCStone Ltd may borrow up to approximately £20.0 million , collateralized by commodities warehouse receipts, to facilitate financing of commodities under repurchase agreement services to its clients, subject to certain terms and conditions of the credit agreement. There were no borrowings outstanding under this credit facility as of June 30, 2019 and September 30, 2018 . The Company has a secured, uncommitted loan facility, under which INTL FCStone Financial Inc. 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 as of June 30, 2019 , and September 30, 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 $30.5 million and $14.0 million in borrowings outstanding under this credit facility as of June 30, 2019 , and September 30, 2018 , respectively. The Company has a secured, uncommitted loan facility, under which INTL FCStone Financial Inc. 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 June 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. There were $5.5 million and $3.8 million in borrowings outstanding under this credit facility as of June 30, 2019 , and September 30, 2018 , respectively. Note Payable to Bank The Company has a loan from a commercial bank, secured by equipment purchased with the proceeds. The note is payable in monthly installments, ending in March 2020. The note bears interest at a rate per annum equal to LIBOR plus 2.00% . The following table sets forth a listing of credit facilities, the current committed amounts as of the report date on the facilities, and outstanding borrowings on the facilities, as well as indebtedness on a promissory note as of June 30, 2019 and September 30, 2018 : (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment June 30, September 30, Committed Credit Facilities Term Loan (1) February 22, 2022 $ 170.6 $ 169.7 $ — Revolving Line of Credit (1) February 22, 2022 175.0 137.0 208.2 INTL FCStone Inc. 345.6 306.7 208.2 INTL FCStone Financial Inc. None April 3, 2020 75.0 — — FCStone Merchants Services, LLC Certain commodities assets November 1, 2019 232.5 164.1 128.0 INTL FCStone Ltd. None January 31, 2020 50.0 — — $ 703.1 $ 470.8 $ 336.2 Uncommitted Credit Facilities INTL FCStone Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a 30.5 14.0 INTL FCStone Ltd. Commodities warehouse receipts n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a 5.5 3.8 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 0.6 1.2 Total outstanding borrowings $ 507.4 $ 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. As reflected above, $357.5 million of the Company’s committed credit facilities are scheduled to expire within twelve months of this filing. The Company intends to renew or replace the facilities when they expire, and based on the Company’s liquidity position and capital structure, the Company believes it will be able to do so. The Company’s credit facility agreements contain financial covenants relating to financial measures on a consolidated basis, as well as on a certain stand-alone subsidiary basis, including minimum tangible net worth, minimum regulatory capital, minimum net unencumbered liquid assets, maximum net loss, minimum fixed charge coverage ratio and maximum funded debt to net worth ratio. Failure to comply with these covenants could result in the debt becoming payable on demand. As of June 30, 2019 , the Company was in compliance with all of its financial covenants under its credit facilities.

Commodity and Other Repurchase

Commodity and Other Repurchase Agreements and Collateralized Transactions (Notes)	9 Months Ended
	Jun. 30, 2019
Commodity and Other Repurchase Agreements [Abstract]
Commodity and Other Repurchase Agreements and Collateralized Transactions	Securities and Commodity Financing Transactions The Company’s outstanding notes receivable in connection with repurchase agreements for agricultural and energy commodities, whereby the clients sell to the Company certain commodity inventory and agree to repurchase the commodity inventory at a future date at a fixed price were $1.3 million and $1.9 million as of June 30, 2019 and September 30, 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, finance financial instruments, acquire securities to cover short positions, acquire securities for settlement, and to accommodate counterparties’ needs. These agreements are recorded as collateralized financings at their contractual amounts plus accrued interest. The related interest is recorded in the condensed consolidated income statements as interest income or interest expense, as applicable. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to adequately collateralize such agreements and transactions in accordance with general industry guidelines and practices. The value of the collateral is valued daily and the Company may require counterparties to deposit additional collateral or return collateral pledged, when appropriate. The carrying amounts of these agreements and transactions approximate fair value due to their short-term nature and the level of collateralization. The Company pledges financial instruments owned to collateralize repurchase agreements. At June 30, 2019 and September 30, 2018 , financial instruments owned, at fair value of $370.9 million and $123.0 million , respectively, were pledged as collateral under repurchase agreements. The counterparty has the right to sell or repledge the collateral in connection with these transactions. These financial instruments owned have been pledged as collateral and have been parenthetically disclosed on the condensed consolidated balance sheet. In addition, as of June 30, 2019 and September 30, 2018 , the Company pledged financial instruments owned, at fair value of $1,450.8 million and $1,481.1 million , respectively, and repledged securities received under reverse repurchase agreements of $1,134.5 million and $369.8 million , respectively, to meet collateral requirements for tri-party repurchase agreements. For these securities, the counterparties do not have the right to sell or repledge the collateral and, therefore, they have not been parenthetically disclosed on the condensed consolidated balance sheet. 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 $1,213.3 million and $267.9 million as of June 30, 2019 , and September 30, 2018 , respectively. Additionally, the Company has also pledged financial instruments owned with a fair value of $18.9 million and $27.1 million as of June 30, 2019 , and September 30, 2018 , respectively, to collateralize uncommitted loan facilities with certain banks as discussed further in Note 10 . At June 30, 2019 and September 30, 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 June 30, 2019 and September 30, 2018 , was $2,904.8 and $1,294.8 million , respectively, of which $427.1 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 condensed consolidated balance sheet. In the normal course of business, this collateral is used by the Company to cover financial instruments sold, not yet purchased, to obtain financing in the form of repurchase agreements or bank loans, and to meet counterparties’ needs under lending arrangements. The following tables provide the contractual maturities of gross obligations under repurchase and securities lending agreements as of June 30, 2019 and September 30, 2018 (in millions): June 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 1,816.4 $ 585.3 $ 499.0 $ 2,900.7 Securities loaned 1,240.9 — — 1,240.9 Gross amount of secured financing $ 3,057.3 $ 585.3 $ 499.0 $ 4,141.6 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 June 30, 2019 and September 30, 2018 (in millions): Securities sold under agreements to repurchase June 30, 2019 September 30, 2018 U.S. Treasury obligations $ 57.1 $ 39.6 U.S. government agency obligations 259.8 461.7 Asset-backed obligations 94.5 50.0 Agency mortgage-backed obligations 2,489.3 1,385.4 Total securities sold under agreement to repurchase 2,900.7 1,936.7 Securities loaned Equity securities 1,240.9 277.9 Total securities loaned 1,240.9 277.9 Gross amount of secured financing $ 4,141.6 $ 2,214.6

Commitments and Contingencies (

Commitments and Contingencies (Notes)	9 Months Ended
	Jun. 30, 2019
Commitments and Contingencies [Abstract]
Commitments and Contingencies Disclosure [Text Block]	Commitments and Contingencies Contingencies 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 June 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. Legal Proceedings From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the policy limits of the insurance. As of June 30, 2019 and September 30, 2018 , the condensed consolidated balance sheets include loss contingency accruals which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, is not likely to be material to the Company’s earnings, financial position or liquidity. There have been no material changes to the legal actions and proceedings compared to September 30, 2018. Contractual Commitments Self-Insurance The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. As of June 30, 2019 , the Company had $0.7 million accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the condensed consolidated balance sheet.

Capital and Other Regulatory Re

Capital and Other Regulatory Requirements (Notes)	9 Months Ended
	Jun. 30, 2019
Capital and Other Regulatory Requirements [Abstract]
Regulatory Capital Requirements under Banking Regulations [Text Block]	Capital and Other Regulatory Requirements The Company’s activities are subject to significant governmental regulation, both in the United States and in the international jurisdictions in which it operates. The subsidiaries of the Company were in compliance with all of their regulatory requirements, as follows: (in millions) As of June 30, 2019 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. SEC and CFTC United States Net capital $ 174.4 $ 92.0 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,407.4 $ 2,349.8 INTL FCStone Financial Inc. CFTC United States Secured funds $ 141.1 $ 125.0 INTL FCStone Financial Inc. SEC United States Customer reserve $ 15.2 $ 9.4 INTL FCStone Financial Inc. SEC United States PAB reserve $ — $ — SA Stone Wealth Management Inc. SEC United States Net capital $ 4.7 $ 0.4 INTL FCStone Ltd(1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 236.3 $ 115.6 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 210.9 $ 206.3 INTL Netherlands BV(1) FCA United Kingdom Net capital $ 238.4 $ 116.6 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 13.2 $ 2.2 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 4.5 $ 0.1 INTL Gainvest S.A. CNV Argentina Net capital $ 0.5 $ 0.1 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.4 $ 0.5 INTL CIBSA S.A. CNV Argentina Net capital $ 0.7 $ 0.2 INTL FCStone Financial (Canada) Inc. Investment Industry Regulatory Organization of Canada ("IIROC") Canada Net capital $ 1.8 $ 0.2 INTL FCStone Financial (Canada) Inc. IIROC Canada Segregated funds $ — $ — (1) INTL Netherlands BV is a holding company that includes the ownership equity of INTL FCStone Ltd. The associated net capital amounts and minimum requirements should not be considered in aggregate. Certain other non-U.S. subsidiaries of the Company are also subject to capital adequacy requirements promulgated by authorities of the countries in which they operate. As of June 30, 2019 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Notes)

Other Expenses (Notes)	9 Months Ended
	Jun. 30, 2019
Other Expenses [Abstract]
Other Expenses [Text Block]	Other Expenses Other expenses for the three and nine months ended June 30, 2019 and 2018 consisted of the following: Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Insurance 0.9 0.7 2.6 1.9 Advertising, meetings and conferences 1.2 1.0 4.1 5.3 Office supplies and printing 0.5 0.5 1.5 1.3 Other clearing related expenses 0.7 0.8 1.8 1.8 Other non-income taxes 1.1 1.3 3.2 3.8 Other 2.7 1.7 7.8 6.3 Total other expenses $ 7.1 $ 6.0 $ 21.0 $ 20.4

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) (Notes)	9 Months Ended
	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Loss, Net Comprehensive income consists of net income and other gains and losses affecting stockholders’ equity that, under U.S. GAAP, are excluded from net income. Other comprehensive loss includes net actuarial losses from defined benefit pension plans and foreign currency translation adjustments. The following table summarizes the changes in accumulated other comprehensive loss, net for the nine months ended June 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 income 0.6 — 0.6 Balances as of June 30, 2019 $ (29.9 ) $ (2.6 ) $ (32.5 )

Income Taxes (Notes)

Income Taxes (Notes)	9 Months Ended
	Jun. 30, 2019
Income Taxes [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes The income tax provision for interim periods is comprised of income tax on jurisdiction-level income (loss) figures provided at the most recent estimated annual effective income tax rate, adjusted for the income tax effect of discrete items. Management uses an estimated annual effective income tax rate based on the forecasted pretax income (loss) and statutory tax rates in the various jurisdictions in which it operates. The Company’s effective income tax rate differs from the U.S. statutory income tax rate primarily due to state and local taxes, global intangible low taxed income, a bargain purchase gain, and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no income tax benefit can be recognized are excluded from the estimated annual effective income tax rate. The Company is required to assess its deferred tax assets and the need for a valuation allowance at each reporting period. This assessment requires judgment on the part of management with respect to benefits that may be realized. The Company will record a valuation allowance against deferred tax assets when it is considered more likely than not that all or a portion of the deferred tax assets will not be realized. Effects of the Tax Cuts and Jobs Act On December 22, 2017, the President of the United States signed and enacted into law H.R. 1, the Tax Cuts and Jobs Act (“the Tax Reform”). Among the significant changes to the U.S. Internal Revenue Code, the Tax Reform lowered the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. The Company will compute its income tax expense (benefit) for the 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. The Tax Reform also establishes new tax laws that will affect 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 forecasted effective tax rate and increases the effective income tax rate by approximately 1% . 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 previously recorded. For the three months ended December 31, 2017, the Company recorded income tax expense of $8.9 million related to the remeasurement of deferred tax assets and liabilities based on the information available. As a result of additional information becoming available after December 31, 2017, the Company recorded an income tax benefit of $0.3 million during the remainder of fiscal 2018 related to the remeasurement of deferred tax assets and liabilities, and as of September 30, 2018, the accounting for the remeasurement of the deferred tax assets and liabilities was complete. 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 made a reasonable estimate of the transition tax and recorded a provisional transition tax obligation of $12.0 million in the three months ended December 31, 2017. The Company recorded income tax benefits of $0.7 million and $0.1 million during the three months ended March 31, 2018, and nothing for the remainder of fiscal 2018, respectively, due to revised E&P computations, refinement of the net operating loss carryforward available, and revised non-U.S. income taxes paid. As of December 31, 2018, the accounting for the mandatory repatriation transition tax on previously untaxed accumulated and current E&P of certain of the Company’s foreign subsidiaries was complete. Current and Prior Period Tax Expense Income tax expense of $5.3 million and $8.9 million for the three months ended June 30, 2019 and 2018 , respectively, and income tax expense of $19.0 million and $41.2 million for the nine months ended June 30, 2019 and 2018 , respectively, reflect estimated federal, foreign, state and local taxes. Due to the Tax Reform, the Company recorded discrete expense of $20.1 million during the nine months ended June 30, 2018. This consists of expense of $20.9 million in the three months ended December 31, 2017, and benefit of $0.8 million in the three months ended March 31, 2018. There were no adjustments recorded in the three months ended June 30, 2018. Tax expense, excluding the discrete expense related to the Tax Reform, was $8.9 million for the three months ended June 30, 2018, and $21.1 million for the nine months ended June 30, 2018. For the three months ended June 30, 2019 and 2018 , the Company’s effective tax rate was 25% and 27% , respectively. For the three months ended June 30, 2019, the effective rate was higher than the U.S. federal statutory rate of 21% due to U.S. state and local taxes, GILTI, and U.S. and foreign permanent differences. A portion of the decrease in the effective tax rate from fiscal year 2018 to fiscal year 2019 is attributed to a decrease in the U.S. federal statutory rate from 24.5% to 21%. The Company’s effective tax rate decreased 0.1% and 0.2% for the three months ended June 30, 2019 and 2018 , respectively, due to excess tax benefits on share-based compensation. The Company recognized a $0.7 million discrete benefit from amended state tax returns and it decreased the effective tax rate 3.0% for the three months ended June 30, 2019. For the nine months ended June 30, 2019 and 2018 , the Company’s effective tax rate was 25% and 51% , respectively. For the nine months ended June 30, 2018, the discrete expense of $20.1 million related to Tax Reform, increased the effective tax rate by 25% . The effective rate for the nine months ended June 30, 2018 was 26% , excluding the impacts of Tax Reform. A portion of the decrease in the effective tax rate from fiscal year 2018 to fiscal year 2019 is attributed to a decrease in the U.S. federal statutory rate from 24.5% to 21% . The Company’s effective tax rate decreased 0.1% and 0.4% for the nine months ended June 30, 2019 and 2018 , respectively, due to excess tax benefits on share-based compensation. The Company recognized a $0.7 million discrete benefit from amended state tax returns and it decreased the effective tax rate 0.8% for the nine months ended June 30, 2019. 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 June 30, 2019 and September 30, 2018 , the Company has net operating loss carryforwards for U.S. federal, state, local, and foreign income tax purposes of $9.4 million , net of valuation allowances, which are available to offset future taxable income in these jurisdictions. The state and local net operating loss carryforwards of $5.7 million , net of valuation allowance, begin to expire after September 2020. INTL Asia Pte. Ltd. has a Singapore net operating loss carryforward of $2.9 million . 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 the Tax Reform, the alternative minimum tax (“AMT”) credit carryforward deferred tax asset has been reclassified to income taxes receivable. The Company can continue to utilize AMT credits to offset regular income tax liability in fiscal years 2019 through 2021. Any remaining amount is fully refundable by fiscal year 2022. In fiscal 2018, the Company generated $6.5 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, it is more likely than not 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 June 30, 2019 and September 30, 2018 was $3.5 million . The valuation allowances as of June 30, 2019 and September 30, 2018 were primarily related to U.S., state and local net operating loss carryforwards and foreign net operating loss carryforwards that, in the judgment of management, are not more likely than not to be realized. When evaluating if U.S. federal, state, and local deferred taxes are realizable, the Company considers when deferred tax liabilities are scheduled to reverse as well as deferred tax liabilities associated with unrealized gains in securities which the Company could sell, if necessary. Furthermore, the Company considers its ability to implement business and tax planning strategies that would allow the remaining U.S. federal, state, and local deferred tax assets, net of valuation allowances, to be realized in less than 10 years. Based on the current and projected profitability of the Company, as well as tax planning strategies that can be implemented, management believes that it is more likely than not that the Company will realize the tax benefit of the U.S. federal, state, and local deferred tax assets, net of the existing valuation allowances, in the future. As of June 30, 2019 and September 30, 2018 , the Company has accumulated undistributed earnings generated by its foreign subsidiaries of approximately $351.6 million and $354.7 million , respectively. The Company recognized the mandatory repatriation tax related to these undistributed earnings as part of the Tax Reform 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 foreign 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. The Company has repatriated $13 million during fiscal 2019 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. The Company and its subsidiaries file income tax returns with the U.S. federal and various U.S. state and local, as well as foreign jurisdictions. The Company has open tax years ranging from September 30, 2010 through September 30, 2018 with U.S. federal and state and local taxing authorities. The Company is currently under examination by the U.S. Internal Revenue Service for the 2016 tax year; however, no additional tax liability is expected. In the United Kingdom (“U.K.”), the Company has open tax years ending September 30, 2017 to September 30, 2018. The Company is currently under examination by HM Revenue and Customs in the UK for the 2017 tax year; however, no additional tax liability is expected. In Brazil, the Company has open tax years ranging from December 31, 2013 through December 31, 2018. In Argentina, the Company has open tax years ranging from September 30, 2011 to September 30, 2018. In Singapore, the Company has open tax years ranging from September 30, 2014 to September 30, 2018.

Acquisitions Acquisitions (Note

Acquisitions Acquisitions (Notes)	9 Months Ended
	Jun. 30, 2019
Acquisitions (Notes) [Abstract]
Business Combination Disclosure [Text Block]	Note 17 - Acquisitions 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 aggregate cash purchase price of $8.2 million for all of the outstanding shares of GMP and its U.S.-based parent 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; therefore, the Company recorded a bargain purchase gain of $5.4 million during the nine months ended June 30, 2019, which is presented within ‘other gain’ in the condensed consolidated income statements. 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. The legal name of GMP was changed to INTL FCStone Credit Trading, LLC (“IFT”) subsequent to the closing date. During the three months ended June 30, 2019, IFT was merged into the Company’s wholly owned regulated U.S. subsidiary, INTL FCStone Financial Inc. The Company’s condensed consolidated income statements include the post-acquisition results, which include operating revenues and a net loss before tax of $2.9 million and $0.6 million , respectively, for the three months ended June 30, 2019, and operating revenues and a net loss before tax of $5.4 million and $1.8 million , respectively, for the nine months ended June 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 . Akshay Financeware, Inc. On February 13, 2019, the Company paid $0.2 million to purchase the remaining interest of a joint venture originally acquired in connection with the acquisition of INTL Technology Services, LLC in September 2018. As a result of this transaction, the Company recorded $2.7 million of indefinite life intangibles for Society for Worldwide Interbank Financial Telecommunications (“SWIFT”) licenses held by the joint venture. CoinInvest GmbH and European Precious Metal Trading GmbH On April 1, 2019 (“the Closing Date”), 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. On the closing date, the Company paid preliminary cash consideration for the acquisition of $22.0 million , including $11.2 million for the purchase of shareholders loans outstanding with the acquired entities. The preliminary purchase price is subject to adjustment based upon the final purchase price calculations, as defined in the purchase agreement, which are subject to any adjustments noted through the course of an audit of the year ended December 31, 2018 financial statements of the acquired entities and for operating results from December 31, 2018 through the Closing Date. The preliminary cash consideration transferred exceeds the preliminary fair value of the tangible net assets acquired on the Closing Date by $7.1 million . The Company acquired certain identifiable intangible assets, including website domain names, non-compete agreements, and internally developed software. The Company has engaged a third-party valuation specialist to assist with the valuation of these acquired intangible assets. As of June 30, 2019, the valuation of these identifiable intangible assets was not yet complete as the Company continues to acquire the information necessary to complete the valuation analysis. As of June 30, 2019, given the status of the valuation analysis, the $7.1 million of excess preliminary consideration over the preliminary fair value of tangible net assets acquired on the Closing Date was recorded as goodwill. Once the valuation analysis is complete, the Company will record reclassification entries to reclassify acquired identifiable intangible assets. The Company’s condensed consolidated income statements include the post-acquisition results, including operating revenues and a net loss before tax of ($0.3) million and $0.6 million , respectively, for the three and nine months ended June 30, 2019. Operating revenues during the three months ended June 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 Physical commodities inventory 9.8 Other assets 1.3 Total fair value of assets acquired 15.4 Accounts payable and other accrued liabilities 0.2 Payables to clients 0.2 Income taxes payable 0.1 Total fair value of liabilities assumed 0.5 Fair value of net assets acquired 14.9 Purchase price 22.0 Goodwill $ 7.1 (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. 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 is 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 condensed consolidated balance sheet as of June 30, 2019. The remaining $2.5 million is due to the seller upon closing of the acquisition, which is expected to occur during the 2019 calendar year upon receiving approval from the MAS.

Segment Analysis (Notes)

Segment Analysis (Notes)	9 Months Ended
	Jun. 30, 2019
Segment Analysis [Abstract]
Segment Reporting Disclosure [Text Block]	Segment Analysis 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) The total revenues reported combine gross revenues for the physical commodities business for subsidiaries that are not broker-dealers and net revenues for all other businesses. In order to reflect the way that the Company’s management views the results, the table below also reflects the segment contribution to ‘operating revenues’, which is shown on the face of the condensed consolidated income statements and which is calculated by deducting physical commodities cost of sales from total revenues. Segment data includes the profitability measure of net contribution by segment. Net contribution is one of the key measures used by management to assess the performance of each segment and for decisions regarding the allocation of the Company’s resources. Net contribution is calculated as revenue less direct cost of sales, transaction-based clearing expenses, variable compensation, introducing broker commissions, and interest expense. Variable compensation paid to risk management consultants/traders generally represents a fixed percentage of 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 Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Total revenues: Commercial Hedging $ 86.4 $ 77.9 $ 226.8 $ 217.7 Global Payments 28.9 26.0 86.0 74.0 Securities 74.2 49.9 215.8 148.4 Physical Commodities 7,604.3 6,873.4 20,847.0 20,852.3 Clearing and Execution Services 78.9 88.9 247.7 249.1 Corporate Unallocated 6.5 7.4 13.5 16.5 Eliminations (6.2 ) (5.2 ) (19.4 ) (14.1 ) Total $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9 Operating revenues: Commercial Hedging $ 86.4 $ 77.9 $ 226.8 $ 217.7 Global Payments 28.9 26.0 86.0 74.0 Securities 74.2 49.9 215.8 148.4 Physical Commodities 14.7 14.9 48.8 41.0 Clearing and Execution Services 78.9 88.9 247.7 249.1 Corporate Unallocated 6.5 7.4 13.5 16.5 Eliminations (6.2 ) (5.2 ) (19.4 ) (14.1 ) Total $ 283.4 $ 259.8 $ 819.2 $ 732.6 Net operating revenues (loss): Commercial Hedging $ 66.9 $ 61.0 $ 178.0 $ 172.0 Global Payments 27.5 24.7 81.7 69.6 Securities 30.3 23.6 94.4 74.7 Physical Commodities 9.7 11.4 35.2 32.3 Clearing and Execution Services 32.5 32.7 101.0 91.9 Corporate Unallocated (1.3 ) 1.2 (10.5 ) (1.3 ) Total $ 165.6 $ 154.6 $ 479.8 $ 439.2 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial Hedging $ 48.0 $ 44.3 $ 127.9 $ 125.5 Global Payments 22.3 19.9 66.4 55.9 Securities 17.9 17.5 59.8 55.6 Physical Commodities 6.4 8.1 25.0 23.1 Clearing and Execution Services 25.0 24.4 78.1 68.8 Total $ 119.6 $ 114.2 $ 357.2 $ 328.9 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 29.7 $ 25.3 $ 73.2 $ 74.0 Global Payments 17.0 16.0 51.4 44.1 Securities 8.2 10.3 36.0 34.1 Physical Commodities 2.8 5.1 16.5 11.8 Clearing and Execution Services 11.9 13.7 41.2 36.9 Total $ 69.6 $ 70.4 $ 218.3 $ 200.9 Reconciliation of segment income to income before tax: Segment income $ 69.6 $ 70.4 $ 218.3 $ 200.9 Net costs not allocated to operating segments 48.0 39.5 146.8 121.9 Other gain — 2.0 5.4 2.0 Income before tax $ 21.6 $ 32.9 $ 76.9 $ 81.0 (in millions) As of June 30, 2019 As of September 30, 2018 Total assets: Commercial Hedging $ 2,084.4 $ 1,935.7 Global Payments 262.7 206.6 Securities 5,178.1 3,058.2 Physical Commodities 488.0 413.7 Clearing and Execution Services 1,914.0 2,109.9 Corporate Unallocated 127.7 100.6 Total $ 10,054.9 $ 7,824.7

Subsequent Events Subsequent Ev

Subsequent Events Subsequent Events (Notes) - USD ($) $ in Millions	Apr. 01, 2019	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]		Note 19 – Subsequent Event s On July 3, 2019, the Company executed a stock purchase agreement (“SPA”) to acquire 100% of the trading firm Fillmore Advisors, LLC (“FAC”). FAC 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 will benefit from FAC’s comprehensive product coverage offering for equities, equity-linked, foreign exchange, credit, rates, and commodities. FAC will become an extension of the newly established prime brokerage division of the Company’s Securities reportable segment. The transaction, which is subject to regulatory approval, is effective on closing. Regulatory approval is expected within the Company’s 4th fiscal quarter with the closing occurring on the 1st day of the month following the receipt of regulatory approval. The consideration due to the seller is equal to a base amount of cash consideration equal to $1.4 million and potential earn out payments over the eight quarters following the closing date. 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 consideration due to the sellers is not material to the Company.
Business Combination, Consideration Transferred	$ 1.4

Basis of Presentation and Con_2

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Policies)	9 Months Ended
	Jun. 30, 2019
Basis of Presentation and Consolidation [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The accompanying unaudited condensed consolidated balance sheet as of September 30, 2018 , which has been derived from the audited consolidated balance sheet of September 30, 2018 , and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to those rules and regulations. The Company believes that the disclosures made are adequate to make the information presented not misleading. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X. Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Form 10-K for the fiscal year ended September 30, 2018 filed with the SEC.
Consolidation, Policy [Policy Text Block]	These condensed consolidated financial statements include the accounts of INTL FCStone Inc. and all other entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation.
Fiscal Period, Policy [Policy Text Block]	The Company’s fiscal year end is September 30, and the fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to fiscal years and fiscal interim periods.
Use of Estimates, Policy [Policy Text Block]	The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurement for financial instruments and investments, revenue recognition, the provision for bad debts, valuation of inventories, valuation of goodwill and intangible assets, incomes taxes, and contingencies. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates.
Reclassification, Policy [Policy Text Block]	Reclassifications During the three and nine months ended June 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 condensed consolidated income statements for the three and nine months ended June 30, 2018. For the three and nine months ended June 30, 2018, brokerage related revenues of $8.5 million and $26.4 million , respectively, were reclassified from ‘trading 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 condensed 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.
New Accounting Pronouncement or Change in Accounting Principle, Description	Accounting Standards Adopted On October 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“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 three or nine months ended June 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 ASU 2016-15, Statements of Cash Flows (“Topic 230”): 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 condensed consolidated financial statements and related disclosures. On October 1, 2018, the Company adopted FASB Accounting Standards Update (“ASU”) 2016-18, Statements of Cash Flows (“Topic 230”): 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 condensed 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 exchange-clearing organizations 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 condensed consolidated statements of cash flows. In May 2017, the FASB issued ASU No. 2017- 09, Scope of Modification Accounting (“Topic 718”), 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 condensed consolidated financial statements and related disclosures.

Earnings per Share (Policies)

Earnings per Share (Policies)	9 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share, Potentially Dilutive Securities	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.

Income Taxes (Policies)

Income Taxes (Policies)	9 Months Ended
	Jun. 30, 2019
Income Taxes [Abstract]
Income Tax, Policy [Policy Text Block]	Note 16 – Income Taxes The income tax provision for interim periods is comprised of income tax on jurisdiction-level income (loss) figures provided at the most recent estimated annual effective income tax rate, adjusted for the income tax effect of discrete items. Management uses an estimated annual effective income tax rate based on the forecasted pretax income (loss) and statutory tax rates in the various jurisdictions in which it operates. The Company’s effective income tax rate differs from the U.S. statutory income tax rate primarily due to state and local taxes, global intangible low taxed income, a bargain purchase gain, and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no income tax benefit can be recognized are excluded from the estimated annual effective income tax rate. The Company is required to assess its deferred tax assets and the need for a valuation allowance at each reporting period. This assessment requires judgment on the part of management with respect to benefits that may be realized. The Company will record a valuation allowance against deferred tax assets when it is considered more likely than not that all or a portion of the deferred tax assets will not be realized. Effects of the Tax Cuts and Jobs Act On December 22, 2017, the President of the United States signed and enacted into law H.R. 1, the Tax Cuts and Jobs Act (“the Tax Reform”). Among the significant changes to the U.S. Internal Revenue Code, the Tax Reform lowered the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. The Company will compute its income tax expense (benefit) for the 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. The Tax Reform also establishes new tax laws that will affect 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 forecasted effective tax rate and increases the effective income tax rate by approximately 1% . 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 previously recorded. For the three months ended December 31, 2017, the Company recorded income tax expense of $8.9 million related to the remeasurement of deferred tax assets and liabilities based on the information available. As a result of additional information becoming available after December 31, 2017, the Company recorded an income tax benefit of $0.3 million during the remainder of fiscal 2018 related to the remeasurement of deferred tax assets and liabilities, and as of September 30, 2018, the accounting for the remeasurement of the deferred tax assets and liabilities was complete. 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 made a reasonable estimate of the transition tax and recorded a provisional transition tax obligation of $12.0 million in the three months ended December 31, 2017. The Company recorded income tax benefits of $0.7 million and $0.1 million during the three months ended March 31, 2018, and nothing for the remainder of fiscal 2018, respectively, due to revised E&P computations, refinement of the net operating loss carryforward available, and revised non-U.S. income taxes paid. As of December 31, 2018, the accounting for the mandatory repatriation transition tax on previously untaxed accumulated and current E&P of certain of the Company’s foreign subsidiaries was complete. Current and Prior Period Tax Expense Income tax expense of $5.3 million and $8.9 million for the three months ended June 30, 2019 and 2018 , respectively, and income tax expense of $19.0 million and $41.2 million for the nine months ended June 30, 2019 and 2018 , respectively, reflect estimated federal, foreign, state and local taxes. Due to the Tax Reform, the Company recorded discrete expense of $20.1 million during the nine months ended June 30, 2018. This consists of expense of $20.9 million in the three months ended December 31, 2017, and benefit of $0.8 million in the three months ended March 31, 2018. There were no adjustments recorded in the three months ended June 30, 2018. Tax expense, excluding the discrete expense related to the Tax Reform, was $8.9 million for the three months ended June 30, 2018, and $21.1 million for the nine months ended June 30, 2018. For the three months ended June 30, 2019 and 2018 , the Company’s effective tax rate was 25% and 27% , respectively. For the three months ended June 30, 2019, the effective rate was higher than the U.S. federal statutory rate of 21% due to U.S. state and local taxes, GILTI, and U.S. and foreign permanent differences. A portion of the decrease in the effective tax rate from fiscal year 2018 to fiscal year 2019 is attributed to a decrease in the U.S. federal statutory rate from 24.5% to 21%. The Company’s effective tax rate decreased 0.1% and 0.2% for the three months ended June 30, 2019 and 2018 , respectively, due to excess tax benefits on share-based compensation. The Company recognized a $0.7 million discrete benefit from amended state tax returns and it decreased the effective tax rate 3.0% for the three months ended June 30, 2019. For the nine months ended June 30, 2019 and 2018 , the Company’s effective tax rate was 25% and 51% , respectively. For the nine months ended June 30, 2018, the discrete expense of $20.1 million related to Tax Reform, increased the effective tax rate by 25% . The effective rate for the nine months ended June 30, 2018 was 26% , excluding the impacts of Tax Reform. A portion of the decrease in the effective tax rate from fiscal year 2018 to fiscal year 2019 is attributed to a decrease in the U.S. federal statutory rate from 24.5% to 21% . The Company’s effective tax rate decreased 0.1% and 0.4% for the nine months ended June 30, 2019 and 2018 , respectively, due to excess tax benefits on share-based compensation. The Company recognized a $0.7 million discrete benefit from amended state tax returns and it decreased the effective tax rate 0.8% for the nine months ended June 30, 2019. 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 June 30, 2019 and September 30, 2018 , the Company has net operating loss carryforwards for U.S. federal, state, local, and foreign income tax purposes of $9.4 million , net of valuation allowances, which are available to offset future taxable income in these jurisdictions. The state and local net operating loss carryforwards of $5.7 million , net of valuation allowance, begin to expire after September 2020. INTL Asia Pte. Ltd. has a Singapore net operating loss carryforward of $2.9 million . 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 the Tax Reform, the alternative minimum tax (“AMT”) credit carryforward deferred tax asset has been reclassified to income taxes receivable. The Company can continue to utilize AMT credits to offset regular income tax liability in fiscal years 2019 through 2021. Any remaining amount is fully refundable by fiscal year 2022. In fiscal 2018, the Company generated $6.5 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, it is more likely than not 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 June 30, 2019 and September 30, 2018 was $3.5 million . The valuation allowances as of June 30, 2019 and September 30, 2018 were primarily related to U.S., state and local net operating loss carryforwards and foreign net operating loss carryforwards that, in the judgment of management, are not more likely than not to be realized. When evaluating if U.S. federal, state, and local deferred taxes are realizable, the Company considers when deferred tax liabilities are scheduled to reverse as well as deferred tax liabilities associated with unrealized gains in securities which the Company could sell, if necessary. Furthermore, the Company considers its ability to implement business and tax planning strategies that would allow the remaining U.S. federal, state, and local deferred tax assets, net of valuation allowances, to be realized in less than 10 years. Based on the current and projected profitability of the Company, as well as tax planning strategies that can be implemented, management believes that it is more likely than not that the Company will realize the tax benefit of the U.S. federal, state, and local deferred tax assets, net of the existing valuation allowances, in the future. As of June 30, 2019 and September 30, 2018 , the Company has accumulated undistributed earnings generated by its foreign subsidiaries of approximately $351.6 million and $354.7 million , respectively. The Company recognized the mandatory repatriation tax related to these undistributed earnings as part of the Tax Reform 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 foreign 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. The Company has repatriated $13 million during fiscal 2019 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. The Company and its subsidiaries file income tax returns with the U.S. federal and various U.S. state and local, as well as foreign jurisdictions. The Company has open tax years ranging from September 30, 2010 through September 30, 2018 with U.S. federal and state and local taxing authorities. The Company is currently under examination by the U.S. Internal Revenue Service for the 2016 tax year; however, no additional tax liability is expected. In the United Kingdom (“U.K.”), the Company has open tax years ending September 30, 2017 to September 30, 2018. The Company is currently under examination by HM Revenue and Customs in the UK for the 2017 tax year; however, no additional tax liability is expected. In Brazil, the Company has open tax years ranging from December 31, 2013 through December 31, 2018. In Argentina, the Company has open tax years ranging from September 30, 2011 to September 30, 2018. In Singapore, the Company has open tax years ranging from September 30, 2014 to September 30, 2018.

Revenue from Contracts with C_2

Revenue from Contracts with Clients Disaggregation of Revenues Table (Tables)	9 Months Ended
	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue [Table Text Block]	Three Months Ended June 30, Nine Months Ended June 30, 2019 2018 2019 2018 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 40.4 $ 45.0 $ 110.7 $ 123.6 OTC derivative brokerage 7.7 7.3 23.9 23.1 Equities and fixed income 4.3 2.7 11.1 8.3 Mutual funds 1.6 1.5 6.1 5.6 Insurance and annuity products 2.1 1.5 5.1 4.5 Other 0.3 0.6 1.0 1.2 Total sales-based commission 56.4 58.6 157.9 166.3 Trailing: Mutual funds 3.1 3.2 9.3 9.8 Insurance and annuity products 3.6 3.7 10.7 11.0 Total trailing commission 6.7 6.9 20.0 20.8 Clearing fees 30.3 34.2 89.7 93.7 Trade conversion fees 1.3 1.6 6.2 5.4 Other 2.8 3.8 8.3 11.8 Total commission and clearing fees: 97.5 105.1 282.1 298.0 Consulting, management, and account fees: Underwriting fees 0.2 0.2 0.7 1.5 Asset management fees 7.2 6.4 19.4 18.9 Advisory and consulting fees 5.1 4.9 14.8 14.3 Sweep program fees 4.2 3.3 12.1 8.2 Client account fees 2.6 2.9 7.8 8.6 Other 1.4 0.7 4.1 1.9 Total consulting, management, and account fees 20.7 18.4 58.9 53.4 Total revenues from contracts with clients $ 118.2 $ 123.5 $ 341.0 $ 351.4 Method of revenue recognition: Point-in-time $ 95.0 $ 102.0 $ 274.7 $ 289.2 Time elapsed 23.2 21.5 66.3 62.2 Total revenues from contracts with clients 118.2 123.5 341.0 351.4 Other sources of revenues Physical precious metals trading 7,327.8 6,613.0 19,944.2 20,176.5 Physical agricultural and energy product trading 271.5 253.2 880.4 659.9 Principal gains, net 102.3 94.9 305.4 270.5 Interest income 53.2 33.7 146.4 85.6 Total revenues $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9 Primary geographic region: United States $ 474.8 $ 431.9 $ 1,458.4 $ 1,159.9 Europe 77.8 48.5 184.9 141.5 South America 15.3 16.7 39.2 48.4 Middle East and Asia 7,303.8 6,620.0 19,929.7 20,191.0 Other 1.3 1.2 5.2 3.1 Total revenues $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share [Table Text Block]	Basic EPS has been computed by dividing net income by the weighted-average number of common shares outstanding. The following is a reconciliation of the numerator and denominator of the diluted earnings per share computations for the periods presented below. Three Months Ended June 30, Nine Months Ended June 30, (in millions, except share amounts) 2019 2018 2019 2018 Numerator: Net income $ 16.3 $ 24.0 $ 57.9 $ 39.8 Less: Allocation to participating securities (0.3 ) (0.3 ) (1.0 ) (0.6 ) Net income allocated to common stockholders $ 16.0 $ 23.7 $ 56.9 $ 39.2 Denominator: Weighted average number of: Common shares outstanding 18,781,401 18,597,165 18,731,203 18,524,846 Dilutive potential common shares outstanding: Share-based awards 230,125 379,733 272,517 351,413 Diluted weighted-average common shares 19,011,526 18,976,898 19,003,720 18,876,259

Assets and Liabilities, at Fa_2

Assets and Liabilities, at Fair Value (Tables)	9 Months Ended
	Jun. 30, 2019
Assets and Liabilities, at Fair Value [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of June 30, 2019 by level in the fair value hierarchy. June 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting and Collateral (1) Total Assets: Unrestricted cash equivalents - certificates of deposit $ 6.5 $ — $ — $ — $ 6.5 Commodities warehouse receipts 58.6 — — — 58.6 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 358.4 — — — 358.4 U.S. Treasury obligations 484.2 — — — 484.2 "To be announced" (TBA) and forward settling securities — 6.1 — (0.5 ) 5.6 Foreign government obligations 10.5 — — — 10.5 Derivatives 3,809.1 8.6 — (3,937.6 ) (119.9 ) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 4,303.8 14.7 — (3,938.1 ) 380.4 Equity securities 79.8 8.0 — — 87.8 Corporate and municipal bonds — 111.6 — — 111.6 U.S. Treasury obligations 248.0 — — — 248.0 U.S. government agency obligations — 465.1 — — 465.1 Foreign government obligations 4.5 — — — 4.5 Agency mortgage-backed obligations — 1,148.7 — — 1,148.7 Asset-backed obligations — 30.4 — — 30.4 Derivatives 2.0 587.9 — (343.7 ) 246.2 Commodities leases — 38.1 — (11.3 ) 26.8 Commodities warehouse receipts 39.6 — — — 39.6 Exchange firm common stock 11.7 — — — 11.7 Mutual funds and other 9.5 — — — 9.5 Financial instruments owned 395.1 2,389.8 — (355.0 ) 2,429.9 Physical commodities inventory 22.3 147.6 — — 169.9 Total assets at fair value $ 5,086.1 $ 2,552.1 $ — $ (4,293.1 ) $ 3,345.1 Liabilities: TBA and forward settling securities — 8.4 — (0.5 ) 7.9 Derivatives 4,005.3 26.7 — (4,025.9 ) 6.1 Payables to broker-dealers, clearing organizations and counterparties 4,005.3 35.1 — (4,026.4 ) 14.0 Equity securities 50.7 1.1 — — 51.8 Foreign government obligations 2.7 — — — 2.7 Corporate and municipal bonds — 29.2 — — 29.2 U.S. Treasury obligations 479.9 — — — 479.9 U.S. government agency obligations — 53.0 — — 53.0 Derivatives — 685.3 — (486.3 ) 199.0 Commodities leases — 55.4 — (9.8 ) 45.6 Financial instruments sold, not yet purchased 533.3 824.0 — (496.1 ) 861.2 Total liabilities at fair value $ 4,538.6 $ 859.1 $ — $ (4,522.5 ) $ 875.2 (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 is included in that level. The following table sets forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2018 by level in the fair value hierarchy. September 30, 2018 (in millions) Level 1 Level 2 Level 3 Netting and Collateral (1) Total Assets: Unrestricted cash equivalents - certificates 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 ) — Payables 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 is included in that level.

Financial Instruments with Of_2

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	9 Months Ended
	Jun. 30, 2019
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Schedule of Derivative Instruments [Table Text Block]	Listed below are the fair values of the Company’s derivative assets and liabilities as of June 30, 2019 and September 30, 2018 . Assets represent net unrealized gains and liabilities represent net unrealized losses. June 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 $ 1,577.7 $ 1,610.4 $ 2,455.7 $ 2,499.3 OTC commodity derivatives 241.9 380.8 207.0 369.9 Exchange-traded foreign exchange derivatives 76.9 73.1 49.8 37.2 OTC foreign exchange derivatives 334.2 308.7 302.5 303.9 Exchange-traded interest rate derivatives 1,200.7 1,417.6 449.3 478.7 OTC interest rate derivatives 20.4 22.5 24.8 25.9 Exchange-traded equity index derivatives 955.8 904.2 4,541.8 4,794.0 TBA and forward settling securities 6.1 8.4 5.0 2.1 Gross fair value of derivative contracts 4,413.7 4,725.7 8,035.9 8,511.0 Impact of netting and collateral (4,281.8 ) (4,512.7 ) (8,118.5 ) (8,317.6 ) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net' $ (114.3 ) $ (268.7 ) Total fair value included in 'Financial instruments owned, at fair value' $ 246.2 $ 186.1 Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties' $ 14.0 $ — Fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 199.0 $ 193.4 (1) As of June 30, 2019 and September 30, 2018 , the Company’s derivative contract volume for open positions were approximately 12.9 million and 10.6 million contracts, respectively. The Company’s derivative contracts are principally held in its Commercial Hedging and Clearing and Execution Services segments. The Company assists its Commercial Hedging segment 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 offsetting the client’s transaction simultaneously with one of the Company’s trading counterparties or with a similar but not identical exchange-traded position. The risk mitigation of these offsetting trades is not within the documented hedging designation requirements of Topic 815. These derivative contracts are traded along with cash transactions because of the integrated nature of the markets for these products. The Company manages the risks associated with derivatives on an aggregate basis along with the risks associated with its proprietary trading and market-making activities in cash instruments as part of its firm-wide risk management policies. In particular, the risks related to derivative positions may be partially offset by inventory, unrealized gains in inventory or cash collateral paid or received. The Company has derivative instruments, which consist of TBA securities and forward settling transactions that are used to manage risk exposures in the trading inventory of the Company’s domestic institutional fixed income business. The fair value on these transactions are recorded in ‘deposits with and receivables from or payables to broker-dealers, clearing organizations and counterparties, net’. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘principal gains, net’. As of June 30, 2019 and September 30, 2018 , these transactions are summarized as follows: June 30, 2019 September 30, 2018 (in millions) 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, net and related notional amounts $ 3.6 $ 1,256.6 $ 1.2 $ 721.5 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (0.2 ) $ 254.5 $ (0.6 ) $ 293.2 Unrealized gain on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 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 $ 0.3 $ (290.6 ) $ — $ — Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (6.9 ) $ (2,132.1 ) $ — $ — Unrealized loss on TBA securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 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, net 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 $ (1.3 ) $ 492.7 $ — $ — Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ 2.2 $ (345.7 ) $ 0.1 $ (427.2 ) (1) The notional amounts of these instruments reflect the extent of the Company's involvement in TBA and forward settling securities and do not represent risk of loss due to counterparty non-performance.
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block]	The following table sets forth the Company’s net gains from derivative contracts for the three and nine months ended June 30, 2019 and 2018 in accordance with Topic 815. The net gains set forth below are included in ‘Cost of sales of physical commodities’ and ‘principal gains, net’ in the condensed consolidated income statements. Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Commodities $ 19.5 $ 38.1 $ 63.6 $ 71.9 Foreign exchange 1.6 2.9 5.3 7.7 Interest rate and equity (0.6 ) 0.5 (3.2 ) 1.1 TBA and forward settling securities (8.0 ) — (6.7 ) 10.3 Net gains from derivative contracts $ 12.5 $ 41.5 $ 59.0 $ 91.0

Physical Commodities Inventor_2

Physical Commodities Inventory Physical Commodities Table (Tables)	9 Months Ended
	Jun. 30, 2019
Inventory Disclosure [Abstract]
Schedule of Inventory, Current [Table Text Block]	(in millions) June 30, September 30, Physical Ag & Energy (1) $ 147.6 $ 114.7 Precious metals - held by broker-dealer subsidiary (2) 22.3 42.1 Precious metals - held by non-broker-dealer subsidiaries (3) 177.9 65.7 Physical commodities inventory $ 347.8 $ 222.5

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Jun. 30, 2019
Goodwill [Abstract]
Schedule of Goodwill [Table Text Block]	The carrying value of goodwill is allocated to the Company’s operating segments as follows: (in millions) June 30, September 30, Commercial Hedging $ 30.3 $ 30.3 Global Payments 6.9 8.9 Physical Commodities 9.5 2.4 Securities 7.0 6.8 Goodwill $ 53.7 $ 48.4

Intangible Assets - (Tables)

Intangible Assets - (Tables)	9 Months Ended
	Jun. 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): June 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 $ 2.7 $ (2.6 ) $ 0.1 $ 2.7 $ (2.6 ) $ 0.1 Client base 21.4 (12.0 ) 9.4 21.4 (10.1 ) 11.3 Total intangible assets subject to amortization: $ 24.1 $ (14.6 ) $ 9.5 $ 24.1 $ (12.7 ) $ 11.4 Intangible assets not subject to amortization: Business licenses $ 2.7 $ — $ 2.7 $ — $ — $ — Total intangible assets not subject to amortization: $ 2.7 $ — $ 2.7 $ — $ — $ — Total intangible assets $ 26.8 $ (14.6 ) $ 12.2 $ 24.1 $ (12.7 ) $ 11.4
Schedule of Expected Amortization Expense [Table Text Block]	Amortization expense related to intangible assets was $1.9 million and $1.7 million for the nine months ended June 30, 2019 and 2018 , respectively. Amortization expense related to intangible assets was $0.6 million for the three months ended June 30, 2019 and 2018 . As of June 30, 2019 , the estimated future amortization expense was as follows: (in millions) Fiscal 2019 (remaining three months) $ 0.7 Fiscal 2020 2.2 Fiscal 2021 2.2 Fiscal 2022 1.0 Fiscal 2023 and thereafter 3.4 $ 9.5

Credit Facilities (Tables)

Credit Facilities (Tables)	9 Months Ended
	Jun. 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 June 30, 2019 and September 30, 2018 : (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment June 30, September 30, Committed Credit Facilities Term Loan (1) February 22, 2022 $ 170.6 $ 169.7 $ — Revolving Line of Credit (1) February 22, 2022 175.0 137.0 208.2 INTL FCStone Inc. 345.6 306.7 208.2 INTL FCStone Financial Inc. None April 3, 2020 75.0 — — FCStone Merchants Services, LLC Certain commodities assets November 1, 2019 232.5 164.1 128.0 INTL FCStone Ltd. None January 31, 2020 50.0 — — $ 703.1 $ 470.8 $ 336.2 Uncommitted Credit Facilities INTL FCStone Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a 30.5 14.0 INTL FCStone Ltd. Commodities warehouse receipts n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a 5.5 3.8 Note Payable to Bank Monthly installments, due March 2020 and secured by certain equipment 0.6 1.2 Total outstanding borrowings $ 507.4 $ 355.2

Commodity and Other Repurchas_2

Commodity and Other Repurchase Agreements and Collateralized Transactions Schedule of Gross Collateralized Financings by Maturity (Tables)	9 Months Ended
	Jun. 30, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Schedule of Repurchase Agreement Counterparties with Whom Repurchase Agreements Exceed 10 Percent of Stockholders' Equity [Table Text Block]	June 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Total Securities sold under agreements to repurchase $ 1,816.4 $ 585.3 $ 499.0 $ 2,900.7 Securities loaned 1,240.9 — — 1,240.9 Gross amount of secured financing $ 3,057.3 $ 585.3 $ 499.0 $ 4,141.6 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 and Collateralized Transactions Schedule of Collateralized Financings by Collateral Type (Tables)	9 Months Ended
	Jun. 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 June 30, 2019 September 30, 2018 U.S. Treasury obligations $ 57.1 $ 39.6 U.S. government agency obligations 259.8 461.7 Asset-backed obligations 94.5 50.0 Agency mortgage-backed obligations 2,489.3 1,385.4 Total securities sold under agreement to repurchase 2,900.7 1,936.7 Securities loaned Equity securities 1,240.9 277.9 Total securities loaned 1,240.9 277.9 Gross amount of secured financing $ 4,141.6 $ 2,214.6

Capital and Other Regulatory _2

Capital and Other Regulatory Requirements (Tables)	9 Months Ended
	Jun. 30, 2019
Capital and Other Regulatory Requirements [Abstract]
Regulatory Capital Requirements under Banking Regulations [Text Block]	Capital and Other Regulatory Requirements The Company’s activities are subject to significant governmental regulation, both in the United States and in the international jurisdictions in which it operates. The subsidiaries of the Company were in compliance with all of their regulatory requirements, as follows: (in millions) As of June 30, 2019 Subsidiary Regulatory Authority Jurisdiction Requirement Type Actual Minimum Requirement INTL FCStone Financial Inc. SEC and CFTC United States Net capital $ 174.4 $ 92.0 INTL FCStone Financial Inc. CFTC United States Segregated funds $ 2,407.4 $ 2,349.8 INTL FCStone Financial Inc. CFTC United States Secured funds $ 141.1 $ 125.0 INTL FCStone Financial Inc. SEC United States Customer reserve $ 15.2 $ 9.4 INTL FCStone Financial Inc. SEC United States PAB reserve $ — $ — SA Stone Wealth Management Inc. SEC United States Net capital $ 4.7 $ 0.4 INTL FCStone Ltd(1) Financial Conduct Authority ("FCA") United Kingdom Net capital $ 236.3 $ 115.6 INTL FCStone Ltd FCA United Kingdom Segregated funds $ 210.9 $ 206.3 INTL Netherlands BV(1) FCA United Kingdom Net capital $ 238.4 $ 116.6 INTL FCStone DTVM Ltda. Brazilian Central Bank and Securities and Exchange Commission of Brazil Brazil Capital adequacy $ 13.2 $ 2.2 INTL Gainvest S.A. National Securities Commission ("CNV") Argentina Capital adequacy $ 4.5 $ 0.1 INTL Gainvest S.A. CNV Argentina Net capital $ 0.5 $ 0.1 INTL CIBSA S.A. CNV Argentina Capital adequacy $ 5.4 $ 0.5 INTL CIBSA S.A. CNV Argentina Net capital $ 0.7 $ 0.2 INTL FCStone Financial (Canada) Inc. Investment Industry Regulatory Organization of Canada ("IIROC") Canada Net capital $ 1.8 $ 0.2 INTL FCStone Financial (Canada) Inc. IIROC Canada Segregated funds $ — $ — (1) INTL Netherlands BV is a holding company that includes the ownership equity of INTL FCStone Ltd. The associated net capital amounts and minimum requirements should not be considered in aggregate. Certain other non-U.S. subsidiaries of the Company are also subject to capital adequacy requirements promulgated by authorities of the countries in which they operate. As of June 30, 2019 , these subsidiaries were in compliance with their local capital adequacy requirements.

Other Expenses (Tables)

Other Expenses (Tables)	9 Months Ended
	Jun. 30, 2019
Other Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Other expenses for the three and nine months ended June 30, 2019 and 2018 consisted of the following: Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Insurance 0.9 0.7 2.6 1.9 Advertising, meetings and conferences 1.2 1.0 4.1 5.3 Office supplies and printing 0.5 0.5 1.5 1.3 Other clearing related expenses 0.7 0.8 1.8 1.8 Other non-income taxes 1.1 1.3 3.2 3.8 Other 2.7 1.7 7.8 6.3 Total other expenses $ 7.1 $ 6.0 $ 21.0 $ 20.4

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Jun. 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, net for the nine months ended June 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 income 0.6 — 0.6 Balances as of June 30, 2019 $ (29.9 ) $ (2.6 ) $ (32.5 )

Acquisitions Purchase Price All

Acquisitions Purchase Price Allocation (Tables)	9 Months Ended
	Jun. 30, 2019
Purchase Price Allocation [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	(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

Segment Analysis (Tables)

Segment Analysis (Tables)	9 Months Ended
	Jun. 30, 2019
Segment Analysis [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Information for the reportable segments is shown in accordance with the Segment Reporting Topic of the ASC as follows Three Months Ended June 30, Nine Months Ended June 30, (in millions) 2019 2018 2019 2018 Total revenues: Commercial Hedging $ 86.4 $ 77.9 $ 226.8 $ 217.7 Global Payments 28.9 26.0 86.0 74.0 Securities 74.2 49.9 215.8 148.4 Physical Commodities 7,604.3 6,873.4 20,847.0 20,852.3 Clearing and Execution Services 78.9 88.9 247.7 249.1 Corporate Unallocated 6.5 7.4 13.5 16.5 Eliminations (6.2 ) (5.2 ) (19.4 ) (14.1 ) Total $ 7,873.0 $ 7,118.3 $ 21,617.4 $ 21,543.9 Operating revenues: Commercial Hedging $ 86.4 $ 77.9 $ 226.8 $ 217.7 Global Payments 28.9 26.0 86.0 74.0 Securities 74.2 49.9 215.8 148.4 Physical Commodities 14.7 14.9 48.8 41.0 Clearing and Execution Services 78.9 88.9 247.7 249.1 Corporate Unallocated 6.5 7.4 13.5 16.5 Eliminations (6.2 ) (5.2 ) (19.4 ) (14.1 ) Total $ 283.4 $ 259.8 $ 819.2 $ 732.6 Net operating revenues (loss): Commercial Hedging $ 66.9 $ 61.0 $ 178.0 $ 172.0 Global Payments 27.5 24.7 81.7 69.6 Securities 30.3 23.6 94.4 74.7 Physical Commodities 9.7 11.4 35.2 32.3 Clearing and Execution Services 32.5 32.7 101.0 91.9 Corporate Unallocated (1.3 ) 1.2 (10.5 ) (1.3 ) Total $ 165.6 $ 154.6 $ 479.8 $ 439.2 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial Hedging $ 48.0 $ 44.3 $ 127.9 $ 125.5 Global Payments 22.3 19.9 66.4 55.9 Securities 17.9 17.5 59.8 55.6 Physical Commodities 6.4 8.1 25.0 23.1 Clearing and Execution Services 25.0 24.4 78.1 68.8 Total $ 119.6 $ 114.2 $ 357.2 $ 328.9 Segment income: (Net contribution less non-variable direct segment costs) Commercial Hedging $ 29.7 $ 25.3 $ 73.2 $ 74.0 Global Payments 17.0 16.0 51.4 44.1 Securities 8.2 10.3 36.0 34.1 Physical Commodities 2.8 5.1 16.5 11.8 Clearing and Execution Services 11.9 13.7 41.2 36.9 Total $ 69.6 $ 70.4 $ 218.3 $ 200.9 Reconciliation of segment income to income before tax: Segment income $ 69.6 $ 70.4 $ 218.3 $ 200.9 Net costs not allocated to operating segments 48.0 39.5 146.8 121.9 Other gain — 2.0 5.4 2.0 Income before tax $ 21.6 $ 32.9 $ 76.9 $ 81.0 (in millions) As of June 30, 2019 As of September 30, 2018 Total assets: Commercial Hedging $ 2,084.4 $ 1,935.7 Global Payments 262.7 206.6 Securities 5,178.1 3,058.2 Physical Commodities 488.0 413.7 Clearing and Execution Services 1,914.0 2,109.9 Corporate Unallocated 127.7 100.6 Total $ 10,054.9 $ 7,824.7

Basis of Presentation and Con_3

Basis of Presentation and Consolidation and Recently Issued Accounting Standards (Details) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2019	Jun. 30, 2018USD ($)
Prior Period Reclassification Adjustment	$ 8.5		$ 26.4
Number of different types of foreign currencies		140
Number of accounts for customers company-wide		20,000

Revenue from Contracts with C_3

Revenue from Contracts with Clients Disaggregation of Revenues Table (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 118,200,000	$ 123,500,000	$ 341,000,000	$ 351,400,000
Revenues	7,873,000,000	7,118,300,000	21,617,400,000	21,543,900,000
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	95,000,000	102,000,000	274,700,000	289,200,000
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23,200,000	21,500,000	66,300,000	62,200,000
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues	474,800,000	431,900,000	1,458,400,000	1,159,900,000
Europe [Member]
Disaggregation of Revenue [Line Items]
Revenues	77,800,000	48,500,000	184,900,000	141,500,000
South America [Member]
Disaggregation of Revenue [Line Items]
Revenues	15,300,000	16,700,000	39,200,000	48,400,000
Middle East and Asia [Domain]
Disaggregation of Revenue [Line Items]
Revenues	7,303,800,000	6,620,000,000	19,929,700,000	20,191,000,000
Other (geographic location) [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,300,000	1,200,000	5,200,000	3,100,000
Commission and Clearing Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	97,500,000	105,100,000	282,100,000	298,000,000
Interest Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	53,200,000	33,700,000	146,400,000	85,600,000
Sales Based Commissions [Domain]
Disaggregation of Revenue [Line Items]
Sales Commissions and Fees	56,400,000	58,600,000	157,900,000	166,300,000
Sales Based Commissions [Domain] | Exhange-Traded Futures and Options [Member]
Disaggregation of Revenue [Line Items]
Revenues	40,400,000	45,000,000	110,700,000	123,600,000
Sales Based Commissions [Domain] | OTC Derivative Brokerage [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,700,000	7,300,000	23,900,000	23,100,000
Sales Based Commissions [Domain] | Equities and Fixed Income Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,300,000	2,700,000	11,100,000	8,300,000
Sales Based Commissions [Domain] | Mutual Fund Sales Based Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,600,000	1,500,000	6,100,000	5,600,000
Sales Based Commissions [Domain] | Variable Annuity [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,100,000	1,500,000	5,100,000	4,500,000
Sales Based Commissions [Domain] | Other Sales Based Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenues	300,000	600,000	1,000,000	1,200,000
Trailing Commissions [Domain]
Disaggregation of Revenue [Line Items]
Revenues	6,700,000	6,900,000	20,000,000	20,800,000
Trailing Commissions [Domain] | Variable Annuity [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,600,000	3,700,000	10,700,000	11,000,000
Trailing Commissions [Domain] | Mutual Fund Trailing Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,100,000	3,200,000	9,300,000	9,800,000
Clearing Fees [Domain]
Disaggregation of Revenue [Line Items]
Revenues	30,300,000	34,200,000	89,700,000	93,700,000
Trade Conversion Fees [Domain]
Disaggregation of Revenue [Line Items]
Revenues	1,300,000	1,600,000	6,200,000	5,400,000
Other Commissions [Domain]
Disaggregation of Revenue [Line Items]
Revenues	2,800,000	3,800,000	8,300,000	11,800,000
Consulting, management, and account fees [Domain] | Sweep Program Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,200,000	3,300,000	12,100,000	8,200,000
Consulting, management, and account fees [Domain] | Advisory and Consulting Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,100,000	4,900,000	14,800,000	14,300,000
Consulting, management, and account fees [Domain] | Asset Management [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,200,000	6,400,000	19,400,000	18,900,000
Consulting, management, and account fees [Domain] | Underwriting Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	200,000	200,000	700,000	1,500,000
Consulting, management, and account fees [Domain] | Client Account Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,600,000	2,900,000	7,800,000	8,600,000
Consulting, management, and account fees [Domain] | Other Consulting, Management, and Account Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,400,000	700,000	4,100,000	1,900,000
Other Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	20,700,000	18,400,000	58,900,000	53,400,000
Principal or Proprietary Transactions [Member]
Disaggregation of Revenue [Line Items]
Revenues	102,300,000	94,900,000	305,400,000	270,500,000
Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,599,300,000	6,866,200,000	20,824,600,000	20,836,400,000
Sales [Member] | Precious Metals Trading Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues	7,327,800,000	6,613,000,000	19,944,200,000	20,176,500,000
Sales [Member] | Physical Commodity Origination and Merchandising [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 271,500,000	$ 253,200,000	$ 880,400,000	$ 659,900,000

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 16,300,000	$ 24,000,000	$ 57,900,000	$ 39,800,000
Less: Net income allocated to participating securities	(300,000)	(300,000)	(1,000,000)	(600,000)
Net income allocated to common shareholders	$ 16,000,000	$ 23,700,000	$ 56,900,000	$ 39,200,000
Weighted average number of common shares outstanding	18,781,401	18,597,165	18,731,203	18,524,846
Dilutive potential common shares outstanding:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	230,125	379,733	272,517	351,413
Diluted weighted-average shares	19,011,526	18,976,898	19,003,720	18,876,259

Earnings per Share - Antiduliti

Earnings per Share - Antidulitive Securities (Details) - shares	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,209,943	76,587	835,441	147,640

Assets and Liabilities, at Fa_3

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	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	$ 1,079.4	$ 1,408.7
Financial Instruments, Owned, at Fair Value	2,429.9	2,054.8
Physical commodities inventory	347.8	222.5
Accounts Payable and Other Accrued Liabilities	144.1	145.4
Payables to Broker-Dealers and Clearing Organizations	(190.7)	(89.5)
Financial Instruments Sold, Not yet Purchased, at Fair Value	861.2	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	358.4	643.3
Receivables from Clearing Organizations	380.4	517.4
Financial Instruments, Owned, at Fair Value	2,429.9	2,054.8
Assets, Fair Value Disclosure	3,345.1	3,376.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	861.2
Liabilities, Fair Value Disclosure	875.2	866.5
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	(7.9)	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	(6.1)	0
Fair Value, Measurements, Recurring [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	(14)	0
Fair Value, Measurements, Recurring [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	169.9	156.9
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	30.4	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	465.1	472.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	53	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	120.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	479.9	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	4.5	6.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	2.7	0.2
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	1,148.7	1,022.5
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	246.2	186.1
Fair Value, Measurements, Recurring [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	26.8	17.7
Financial Instruments Sold, Not yet Purchased, at Fair Value	45.6	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	39.6	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	11.7	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	9.5	6.3
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	87.8	74.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	51.8	51.5
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	111.6	79.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	29.2	20.1
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	484.2
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	10.5	7.7
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	5.6	2.9
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	(119.9)
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	58.6	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 and Cash Equivalents, Fair Value Disclosure	6.5	3.8
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Receivables from Clearing Organizations	(3,938.1)	(7,789.2)
Financial Instruments, Owned, at Fair Value	(355)	(341.1)
Assets, Fair Value Disclosure	(4,293.1)	(8,130.3)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(496.1)	(510.8)
Liabilities, Fair Value Disclosure	(4,522.5)	(8,333.8)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	0.5	2.1
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	4,025.9	7,820.9
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Payable to broker-dealers, clearing organizations and counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations	4,026.4	7,823
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | 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] | Counterparty And Cash Collateral Netting Adjustment [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	(343.7)	(329.3)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(486.3)	(494.6)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	(11.3)	(11.8)
Financial Instruments Sold, Not yet Purchased, at Fair Value	(9.8)	(16.2)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Mutual funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | 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] | Counterparty And Cash Collateral Netting Adjustment [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] | Counterparty And Cash Collateral Netting Adjustment [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(0.5)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	(3,937.6)
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	358.4	643.3
Receivables from Clearing Organizations	4,303.8	8,282
Financial Instruments, Owned, at Fair Value	395.1	231.4
Assets, Fair Value Disclosure	5,086.1	9,202.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	533.3	535.9
Liabilities, Fair Value Disclosure	4,538.6	8,345.2
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	(4,005.3)	(7,809.3)
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	(4,005.3)	(7,809.3)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	22.3	42.1
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	120.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	479.9	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	4.5	6.4
Financial Instruments Sold, Not yet Purchased, at Fair Value	2.7	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	2	0.8
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	39.6	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	11.7	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	9.5	6.3
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	79.8	71.2
Financial Instruments Sold, Not yet Purchased, at Fair Value	50.7	51.1
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] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	484.2
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	10.5	7.7
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	3,809.1
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	58.6	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 and Cash Equivalents, Fair Value Disclosure	6.5	3.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Receivables from Clearing Organizations	14.7	24.6
Financial Instruments, Owned, at Fair Value	2,389.8	2,164.5
Assets, Fair Value Disclosure	2,552.1	2,303.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	824	841.4
Liabilities, Fair Value Disclosure	859.1	855.1
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	(8.4)	(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	(26.7)	(11.6)
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	(35.1)	(13.7)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	147.6	114.8
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	30.4	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	465.1	472.9
Financial Instruments Sold, Not yet Purchased, at Fair Value	53	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] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	1,148.7	1,022.5
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]
Financial Instruments, Owned, at Fair Value	587.9	514.6
Financial Instruments Sold, Not yet Purchased, at Fair Value	685.3	688
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	38.1	29.5
Financial Instruments Sold, Not yet Purchased, at Fair Value	55.4	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] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	8	3
Financial Instruments Sold, Not yet Purchased, at Fair Value	1.1	0.4
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	111.6	79.1
Financial Instruments Sold, Not yet Purchased, at Fair Value	29.2	20.1
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] | 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] | TBA and forward settling securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations	6.1	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	8.6
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 and Cash Equivalents, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Receivables from Clearing Organizations	0	0
Financial Instruments, Owned, at Fair Value	0	0
Assets, Fair Value Disclosure	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Liabilities, Fair Value Disclosure	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] | 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] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | 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] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange firm common stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual funds and other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | 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] | 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]
Receivables from Clearing Organizations	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] | 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] | Commodities warehouse receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Securities Segregated under Federal and Other Regulations	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 0	0
Collateralized Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		(2.1)
Debt Security, Government, Non-US [Member] | Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		0
Derivative [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payables to Broker-Dealers and Clearing Organizations		(271.6)
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		(7,787.1)
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		7,495.9
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		19.6
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		0
US Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		778.4
US Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Counterparty And Cash Collateral Netting Adjustment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		0
US Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		778.4
US Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		0
US Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivables from Clearing Organizations		$ 0

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	Jun. 30, 2019	Sep. 30, 2018
Financial Instruments Sold, Not yet Purchased, at Fair Value	$ 861.2	$ 866.5
Financial instrument sold, not yet purchased [Member]
Derivative, Fair Value, Net	$ 199	$ 193.4

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	Jun. 30, 2019	Sep. 30, 2018
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4,413.7	$ 8,035.9
Derivative Liability, Fair Value, Gross Liability	4,725.7	8,511
Impact of netting and collateral	4,281.8	8,118.5
Impact of netting and collateral	4,512.7	8,317.6
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(114.3)	(268.7)
Financial instruments owned [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	246.2	186.1
Payable to broker-dealers, clearing organizations and counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	14	0
Financial instrument sold, not yet purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	199	193.4
Exchange-traded Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,577.7	2,455.7
Derivative Liability, Fair Value, Gross Liability	1,610.4	2,499.3
Over the Counter (OTC) Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	241.9	207
Derivative Liability, Fair Value, Gross Liability	380.8	369.9
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	76.9	49.8
Derivative Liability, Fair Value, Gross Liability	73.1	37.2
Over the Counter (OTC) Foreign Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	334.2	302.5
Derivative Liability, Fair Value, Gross Liability	308.7	303.9
Exchange-traded interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,200.7	449.3
Derivative Liability, Fair Value, Gross Liability	1,417.6	478.7
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	20.4	24.8
Derivative Liability, Fair Value, Gross Liability	22.5	25.9
Equity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	955.8	4,541.8
Derivative Liability, Fair Value, Gross Liability	904.2	4,794
TBA and forward settling securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6.1	5
Derivative Liability, Fair Value, Gross Liability	$ 8.4	$ 2.1

Financial Instruments with Of_5

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) number in Millions	Jun. 30, 2019	Sep. 30, 2018
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative, Number of Instruments Held	12.9	10.6

Financial Instruments with Of_6

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - TBAs and Forward Settling Securities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Derivative Asset, Fair Value, Gross Asset	$ 4,413.7	$ 8,035.9
Derivative Liability, Fair Value, Gross Liability	4,725.7	8,511
TBA securities purchased [Member]
Derivative Liability, Notional Amount	254.5	293.2
Derivative Asset, Notional Amount	(1,256.6)	(721.5)
TBA securities sold [Member]
Derivative Liability, Notional Amount	2,132.1	812.7
Derivative Asset, Notional Amount	(290.6)	(1,099.5)
Forward settling securities purchased [Member]
Derivative Asset, Notional Amount		(614.3)
Over the Counter (OTC) Commodity Contracts [Member]
Derivative Liability, Notional Amount	492.7	0
Derivative Asset, Notional Amount	(345.7)	(427.2)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | TBA securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset	3.6	1.2
Derivative Liability, Fair Value, Gross Liability	(0.2)	(0.6)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | TBA securities sold [Member]
Derivative Asset, Fair Value, Gross Asset	0	3.2
Derivative Liability, Fair Value, Gross Liability	0	(1.5)
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | Forward settling securities purchased [Member]
Derivative Asset, Fair Value, Gross Asset		0.5
Deposits and receivables from broker-dealers, clearing organizations and counterparties [Domain] | Over the Counter (OTC) Commodity Contracts [Member]
Derivative Asset, Fair Value, Gross Asset	2.2	0.1
Payable to broker-dealers, clearing organizations and counterparties [Member] | TBA securities sold [Member]
Derivative Asset, Fair Value, Gross Asset	0.3	0
Derivative Liability, Fair Value, Gross Liability	(6.9)	0
Payable to broker-dealers, clearing organizations and counterparties [Member] | Over the Counter (OTC) Commodity Contracts [Member]
Derivative Liability, Fair Value, Gross Liability	$ (1.3)	$ 0

Financial Instruments with Of_7

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 19.5	$ 38.1	$ 63.6	$ 71.9
Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	1.6	2.9	5.3	7.7
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(0.6)	0.5	(3.2)	1.1
TBA and forward settling securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(8)	0	(6.7)	10.3
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 12.5	$ 41.5	$ 59	$ 91

Receivables From Customers, N_2

Receivables From Customers, Net and Notes Receivable, Net - Allowance for Customer Receivables (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Receivables from customers and notes receivable, net [Abstract]
Allowance for Doubtful Accounts Receivable	$ 11.2	$ 10.2
Allowance for Doubtful Accounts, Premiums and Other Receivables	$ 45.6	$ 48

Receivables From Customers, N_3

Receivables From Customers, Net and Notes Receivable, Net Receivables from Customers, Net and Notes Receivables, Net - Bad Debt Expense and Recoveries (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Provision for Doubtful Accounts	$ 0.5	$ 1.6	$ 1.5	$ 1.9
Payments for Legal Settlements			8.4
Other Segments [Member]
Allowance for Doubtful Accounts Receivable, Recoveries			$ 2.4

Physical Commodities Inventor_3

Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Inventory [Line Items]
Physical Ag & Energy(1)	$ 147.6	$ 114.7
Precious metals - held by non-broker-dealer subsidiaries(3)	202.9	156.9
Physical commodities inventory	347.8	222.5
Physical commodities inventory - precious metals [Member]
Inventory [Line Items]
Precious metals - held by non-broker-dealer subsidiaries(3)	22.3	42.1
Finished commodities	$ 177.9	$ 65.7

Physical Commodities Inventor_4

Physical Commodities Inventory - LCM Adjustments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2016
Physical Commodities Inventory [Abstract]
Inventory Adjustments	$ 2.6	$ 0.4	$ 0.6

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Goodwill	$ 53.7	$ 48.4
Commercial Hedging [Member]
Goodwill [Line Items]
Goodwill	30.3	30.3
Global Payments [Member]
Goodwill [Line Items]
Goodwill	6.9	8.9
Physical Commodities [Member]
Goodwill [Line Items]
Goodwill	9.5	2.4
Securities [Member]
Goodwill [Line Items]
Goodwill	$ 7	$ 6.8

Goodwill Goodwill Adjustments (

Goodwill Goodwill Adjustments (Details) - USD ($)	6 Months Ended	9 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Translation and Purchase Accounting Adjustments		$ 0	$ (1,300,000)
Goodwill, Acquired During Period	$ 7,100,000	200,000
Indefinite-lived Intangible Assets, Translation and Purchase Accounting Adjustments		$ 2,000,000

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived License Agreements	$ 2.7	$ 2.7	$ 0
Finite-Lived Intangible Assets, Accumulated Amortization	0	(14.6)	(12.7)
Finite-Lived Intangible Assets, Net	9.5	9.5	11.4
Finite-Lived Intangible Assets, Gross		24.1	24.1
Gross Finite and Indefinite-Lived Intangible Assets		26.8	24.1
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	(14.6)		(12.7)
Intangible Assets, Net (Excluding Goodwill)	$ 12.2		11.4
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Computer Software, Gross		2.7	2.7
Finite-Lived Intangible Assets, Accumulated Amortization		(2.6)	(2.6)
Finite-Lived Intangible Assets, Net		0.1	0.1
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Customer Lists, Gross		21.4	21.4
Finite-Lived Intangible Assets, Accumulated Amortization		(12)	(10.1)
Finite-Lived Intangible Assets, Net		$ 9.4	$ 11.3

Intangible Assets - Indefinite-

Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Indefinite-lived Intangible Assets [Line Items]
Gross Finite and Indefinite-Lived Intangible Assets		$ 26.8	$ 24.1
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	$ (14.6)		(12.7)
Intangible Assets, Net (Excluding Goodwill)	$ 12.2		$ 11.4

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2019 (remaining six months)	$ 0.7
Fiscal 2020	2.2
Fiscal 2021	2.2
Fiscal 2022	1
Fiscal 2023 and thereafter	3.4
Finite-Lived Intangible Assets, Net	$ 9.5	$ 9.5	$ 11.4

Intangible Assets Definite Live

Intangible Assets Definite Lived Intangible Assets Amortization (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Definite Lived Intangible Assets Amortization [Abstract]
Amortization of Intangible Assets	$ 0.6	$ 1.9	$ 1.7	$ 2.1

Intangible Assets Intangible As

Intangible Assets Intangible Assets Acquired (Details) $ in Millions	9 Months Ended
	Jun. 30, 2019USD ($)
Intangible Assets Acquired [Abstract]
Indefinite-lived Intangible Assets Acquired	$ 2.7

Credit Facilities - Number of C

Credit Facilities - Number of Credit Facilities (Details) $ in Millions	Jun. 30, 2019USD ($)	Mar. 31, 2019	Dec. 31, 2018USD ($)
Number of credit facilities		4
HCO Syndicated line of credit facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 350		$ 262
Line of Credit Facility, Remaining Borrowing Capacity	345.6
FCS Margin line of credit facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	75
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	232.5
INTL FCStone Ltd [Member]
Line of Credit Facility, Maximum Borrowing Capacity	100
INTL FCStone Ltd [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50		$ 25

Credit Facilities - Credit Faci

Credit Facilities - Credit Facilities (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Line of Credit Facility [Line Items]
Short-term Debt	$ 470.8		$ 336.2
Notes Payable to Bank	0.6		1.2
Debt and Capital Lease Obligations	$ 507.4		355.2
Debt Instrument, Interest Rate During Period	2.00%
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Credit Facilities Expiring Within One Year	$ 357.5
Line of Credit Facility, Maximum Borrowing Capacity	703.1
IFFI Uncommitted Lines of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Short-term Debt	30.5		14
HCO Syndicated line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	345.6
Line of Credit Facility, Maximum Borrowing Capacity	350	$ 262
Payments of Financing Costs	3.1
Lenders under loans	306.7
FCS Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75
Line of Credit, Current	0		0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	232.5
Line of Credit, Current	164.1		128
INTL FCStone Ltd [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	50	$ 25
Line of Credit, Current	0		0
INTL FCStone Ltd. Uncommitted Line of Credit [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	20
INTL FCStone Financial Inc. Uncommitted Commodities Delivery Line [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75
IFL Uncommitted Line of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Short-term Debt	0		0
Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	20
Short-term Debt	$ 5.5		$ 3.8

Commodity and Other Repurchas_4

Commodity and Other Repurchase Agreements Commodity and Other Repurchase Agreements (Details) - USD ($)	Jun. 30, 2019	Sep. 30, 2018
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financing Receivable, Gross	$ 1,300,000	$ 1,900,000
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	2,904,800,000	1,294,800,000
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	370,900,000	123,000,000
Securities Loaned, Fair Value of Collateral	1,213,300,000	267,900,000
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	285,500,000	123,000,000
Trading Securities Pledged as Collateral	1,450,800,000	1,481,100,000
Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements	1,134,500,000	369,800,000
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	$ 427,100,000	$ 473,900,000

Commodity and Other Repurchas_5

Commodity and Other Repurchase Agreements and Collateralized Transactions Gross Financings Collateral Maturities Table (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 2,900.7	$ 1,936.7
Securities Loaned	1,240.9	277.9
Collateralized transactions:	4,141.6	2,214.6
Maturity Overnight and on Demand [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,816.4	934.9
Securities Loaned	1,240.9	277.9
Collateralized transactions:	3,057.3	1,212.8
Maturity Less than 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	585.3	661.3
Securities Loaned	0	0
Collateralized transactions:	585.3	661.3
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	499	340.5
Securities Loaned	0	0
Collateralized transactions:	$ 499	$ 340.5

Commodity and Other Repurchas_6

Commodity and Other Repurchase Agreements and Collateralized Transactions Gross Collateralized Financings by Collateral Type Table (Details) - USD ($)	Jun. 30, 2019	Sep. 30, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 2,900,700,000	$ 1,936,700,000
Securities Loaned	1,240,900,000	277,900,000
Collateralized transactions:	4,141,600,000	2,214,600,000
US Government Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	57,100,000	39,600,000
US Government Agencies Debt Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	259,800,000	461,700,000
Asset-backed Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	94,500,000	50,000,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	2,489,300,000	1,385,400,000
Equity Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Loaned	$ 1,240,900,000	$ 277,900,000

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies - Contingencies and Litigation (Details) $ in Millions	Jun. 30, 2019USD ($)
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	$ 29.2

Commitments and Contingencies_2

Commitments and Contingencies Commitments and Contingencies - Self Insurance (Details) $ in Millions	Jun. 30, 2019USD ($)
Commitments and Contingencies [Abstract]
Self Insurance Reserve	$ 0.7

Capital and Other Regulatory _3

Capital and Other Regulatory Requirements - Regulatory Capital Requirements (Details) $ in Millions	Jun. 30, 2019USD ($)
FCStone LLC [Member]
Net Capital under Commodity Exchange Act Computation	$ 174.4
Required Net Capital under Commodity Exchange Act	92
Cash and Securities Segregated under Commodity Exchange Act Regulation	2,407.4
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	2,349.8
Secured Funds	141.1
Secured Funds Required Under Commodity Exchange Act	125
Sterne Agee, and Leach, Inc [Member]
Required Net Capital under Commodity Exchange Act	0.4
Sterne Agee Financial Services, Inc. [Member]
Net Capital under Commodity Exchange Act Computation	4.7
INTL FCStone Ltd [Member]
Net Capital under Commodity Exchange Act Computation	236.3
Required Net Capital under Commodity Exchange Act	115.6
Cash and Securities Segregated under Commodity Exchange Act Regulation	210.9
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	206.3
INTL Netherlands BV [Member]
Net Capital under Commodity Exchange Act Computation	238.4
Required Net Capital under Commodity Exchange Act	116.6
INTL FCStone DTVM Ltda [Member]
Capital Required for Capital Adequacy	2.2
Capital	13.2
Gainvest S.A. Sociedad Gerente de FCI - Comision Nacional de Valores [Member]
Net Capital under Commodity Exchange Act Computation	0.5
Required Net Capital under Commodity Exchange Act	0.1
Capital Required for Capital Adequacy	0.1
Capital	4.5
INTL Capital S.A. – General Inspector of Justice [Member] [Domain]
Net Capital under Commodity Exchange Act Computation	0.7
Required Net Capital under Commodity Exchange Act	0.2
INTL Capital S.A. – Superintendence of Securities Markets of Buenos Aires [Member] [Domain]
Capital Required for Capital Adequacy	0.5
Capital	5.4
INTL FCStone Financial (Canada) Inc. [Member] [Member]
Net Capital under Commodity Exchange Act Computation	1.8
Required Net Capital under Commodity Exchange Act	0.2
Cash and Securities Segregated under Commodity Exchange Act Regulation	0
Cash and Securities Segregated under Commodity Exchange Act Regulation, Amount Required to be Segregated	0
Customer Reserve Requirement [Member] [Member]
Cash Reserve Deposit Required and Made	15.2
Cash Reserve Deposit Required	9.4
PAB Reserve Requirement [Member]
Cash Reserve Deposit Required and Made	0
Cash Reserve Deposit Required	$ 0

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Expenses [Abstract]
General Insurance Expense	$ 0.9	$ 0.7	$ 2.6	$ 1.9
Advertising Expense	1.2	1	4.1	5.3
Supplies and Postage Expense	0.5	0.5	1.5	1.3
Clearance Fees	0.7	0.8	1.8	1.8
Taxes, Miscellaneous	1.1	1.3	3.2	3.8
Other Expenses	2.7	1.7	7.8	6.3
Other Cost and Expense, Operating	$ 7.1	$ 6	$ 21	$ 20.4

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	$ (32.5)		$ (32.5)		$ (33.1)
Other comprehensive loss	0.3	$ (4.9)	0.6	$ (8.7)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(29.9)		(29.9)		(30.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0.6
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(2.6)		(2.6)		(2.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	(32.5)		(32.5)		$ (33.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0.6
Other comprehensive loss	$ 0.3	$ (4.9)	$ 0.6	$ (8.7)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended			12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2016
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate					21.00%			24.50%
Undistributed Earnings of Foreign Subsidiaries	$ 351.6				$ 351.6	$ 354.7		$ 354.7
Foreign Earnings Repatriated					$ 13
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	0.10%	0.20%			0.10%		0.40%
Effective Income Tax Rate Reconciliation, Tax Settlement, State and Local, Amount	$ 0.7				$ 0.7
Effective Income Tax Rate Reconciliation, Tax Settlement, State and Local, Percent	3.00%						0.80%
Operating Loss Carryforwards	$ 9.4				9.4
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	5.7				5.7
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	6.5				6.5
Deferred Tax Assets, Valuation Allowance	3.5				3.5				$ 3.6
Income Tax Expense (Benefit)	$ 5.3	$ 8.9			$ 19		$ 41.2
Effective Income Tax Rate Reconciliation, Percent	25.00%	27.00%			25.00%		51.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount							$ 20.1
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent							25.00%
Deferred Income Tax Expense (Benefit)				$ 8.9		$ 0.3
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount			$ 0.7	$ 12

Acquisitions Akshay Financeware

Acquisitions Akshay Financeware, Inc. Acquisition (Details) - USD ($) $ in Millions	Apr. 01, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 1.4
Indefinite-lived Intangible Assets Acquired		$ 2.7
Akshay Financeware, Inc. Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		0.2
Indefinite-lived Intangible Assets Acquired		$ 2.7

Acquisitions GMP Securities Acq

Acquisitions GMP Securities Acquisition (Details) - USD ($) $ in Millions	Apr. 01, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jan. 14, 2019
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 1.4
Business Combination, Bargain Purchase, Gain Recognized, Amount			$ 5.4	$ 0
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 0.3
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		0.6
GMP Securities Acquisition [Member]
Business Acquisition [Line Items]
Cash and cash equivalents					$ 1.1
Business Combination, Consideration Transferred			8.2
Business Combination, Bargain Purchase, Gain Recognized, Amount			5.4
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		2.9	5.4
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 0.6	$ 1.8
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, net					2.7
Property and equipment, net					0.7
Other assets					0.7
Total fair value of assets acquired					20
Accounts payable and other accrued liabilities					1.9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other					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

Acquisitions UOB Acquisition (D

Acquisitions UOB Acquisition (Details) - USD ($) $ in Millions	Apr. 01, 2019	May 08, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 1.4
GMP Securities Acquisition [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 8.2
UOB Acquisition [Member] [Member]
Business Acquisition [Line Items]
Escrow Deposit Disbursements Related to Property Acquisition			$ 2.5
Business Combination, Consideration Transferred		$ 2.5

Acquisitions Coininvest and EPM

Acquisitions Coininvest and EPMT Acquisitions (Details) - USD ($) $ in Millions	Apr. 01, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 1.4
GMP Securities Acquisition [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	2
Receivables from clients (1)	1.2
Receivable from affiliate	1.1
Physical commodities inventory	9.8
Other assets	1.3
Total fair value of assets acquired	15.4
Accounts payable and other accrued liabilities	0.2
Payables to clients	0.2
Income taxes payable	0.1
Total fair value of liabilities assumed	0.5
Fair value of net assets acquired	14.9
Business Combination, Consideration Transferred		$ 22
Goodwill, Acquired During Period	$ 7.1

Segment Analysis (Details)

Segment Analysis (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 7,873,000,000	$ 7,118,300,000	$ 21,617,400,000	$ 21,543,900,000
Operating revenues	283,400,000	259,800,000	819,200,000	732,600,000
Net operating revenues	165,600,000	154,600,000	479,800,000	439,200,000
Net Segment Contribution	119,600,000	114,200,000	357,200,000	328,900,000
Segment Income	69,600,000	70,400,000	218,300,000	200,900,000
Costs not allocated to operating segments	48,000,000	39,500,000	146,800,000	121,900,000
Other gain	0	2,000,000	5,400,000	2,000,000
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	21,600,000	32,900,000	76,900,000	81,000,000
Assets	10,054,900,000		10,054,900,000		$ 7,824,700,000
Commercial Hedging [Member]
Segment Reporting Information [Line Items]
Revenues	86,400,000	77,900,000	226,800,000	217,700,000
Operating revenues	86,400,000	77,900,000	226,800,000	217,700,000
Net operating revenues	66,900,000	61,000,000	178,000,000	172,000,000
Net Segment Contribution	48,000,000	44,300,000	127,900,000	125,500,000
Segment Income	29,700,000	25,300,000	73,200,000	74,000,000
Assets	2,084,400,000		2,084,400,000		1,935,700,000
Global Payments [Member]
Segment Reporting Information [Line Items]
Revenues	28,900,000	26,000,000	86,000,000	74,000,000
Operating revenues	28,900,000	26,000,000	86,000,000	74,000,000
Net operating revenues	27,500,000	24,700,000	81,700,000	69,600,000
Net Segment Contribution	22,300,000	19,900,000	66,400,000	55,900,000
Segment Income	17,000,000	16,000,000	51,400,000	44,100,000
Assets	262,700,000		262,700,000		206,600,000
Securities Segment [Member]
Segment Reporting Information [Line Items]
Revenues	74,200,000	49,900,000	215,800,000	148,400,000
Operating revenues	74,200,000	49,900,000	215,800,000	148,400,000
Net operating revenues	30,300,000	23,600,000	94,400,000	74,700,000
Net Segment Contribution	17,900,000	17,500,000	59,800,000	55,600,000
Segment Income	8,200,000	10,300,000	36,000,000	34,100,000
Assets	5,178,100,000		5,178,100,000		3,058,200,000
Physical Commodities [Member]
Segment Reporting Information [Line Items]
Revenues	7,604,300,000	6,873,400,000	20,847,000,000	20,852,300,000
Operating revenues	14,700,000	14,900,000	48,800,000	41,000,000
Net operating revenues	9,700,000	11,400,000	35,200,000	32,300,000
Net Segment Contribution	6,400,000	8,100,000	25,000,000	23,100,000
Segment Income	2,800,000	5,100,000	16,500,000	11,800,000
Assets	488,000,000		488,000,000		413,700,000
Clearing and Execution Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	78,900,000	88,900,000	247,700,000	249,100,000
Operating revenues	78,900,000	88,900,000	247,700,000	249,100,000
Net operating revenues	32,500,000	32,700,000	101,000,000	91,900,000
Net Segment Contribution	25,000,000	24,400,000	78,100,000	68,800,000
Segment Income	11,900,000	13,700,000	41,200,000	36,900,000
Assets	1,914,000,000		1,914,000,000		2,109,900,000
Corporate [Member]
Segment Reporting Information [Line Items]
Net operating revenues	(1,300,000)	$ 1,200,000	(10,500,000)	$ (1,300,000)
Assets	$ 127,700,000		$ 127,700,000		$ 100,600,000