StoneX (SNEX) 10-K 14 Dec 20 2020 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Dec. 10, 2020	Mar. 31, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	000-23554
Entity Registrant Name	StoneX Group Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	59-2921318
Entity Address, Address Line One	155 East 44th Street
Entity Address, Address Line Two	Suite 900
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10017
City Area Code	212
Local Phone Number	485-3500
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	SNEX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 429.6
Entity Common Stock, Shares Outstanding		19,434,929
Documents Incorporated by Reference	Certain portions of the definitive Proxy Statement for the Registrant’s Annual Meeting of Stockholders to be held on February 24, 2021 are incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0000913760
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2020
Amendment Flag	false
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
ASSETS
Cash and cash equivalents	$ 952.6	$ 471.3
Cash, securities and other assets segregated under federal and other regulations (including $2.6 million and $306.0 million at fair value at September 30, 2020 and September 30, 2019, respectively)	1,920.2	1,049.9
Collateralized transactions:
Securities purchased under agreements to resell	1,696.2	1,424.5
Securities borrowed	1,440	1,423.2
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net (including $1,775.8 million and $626.9 million at fair value at September 30, 2020 and September 30, 2019, respectively)	3,629.9	2,540.5
Receivable from clients, net	411.4	422.3
Notes receivable, net	1.7	2.9
Income taxes receivable	16.6	5.2
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $468.6 million and $478.8 million at September 30, 2020 and September 30, 2019, respectively)	2,727.7	2,175.2
Physical commodities inventory, net (including $215.7 million and $151.9 million at fair value at September 30, 2020 and September 30, 2019, respectively)	281.1	229.3
Deferred income taxes, net	36.9	18
Property and equipment, net	62.1	43.9
Operating right of use assets	101.5
Goodwill and intangible assets, net	109.5	67.9
Other assets	87.5	62
Total assets	13,474.9	9,936.1
Liabilities:
Accounts payable and other accrued liabilities (including $1.5 million and $1.8 million at fair value at September 30, 2020 and September 30, 2019, respectively)	272.6	157.5
Operating lease liabilities	118.7
Payables to:
Clients	5,689	3,589.5
Broker-dealers, clearing organizations and counterparties (including $14.7 million and $5.6 million at fair value at September 30, 2020 and September 30, 2019, respectively)	537.5	266.2
Payable to lenders under loans	268.1	202.3
Senior secured borrowings, net	515.5	167.6
Income taxes payable	22.6	10.4
Collateralized transactions:
Securities sold under agreements to repurchase	3,155.5	2,773.7
Securities loaned	1,441.9	1,459.9
Financial instruments sold, not yet purchased, at fair value	686	714.8
Total liabilities	12,707.4	9,341.9
Commitments and contingencies (Note 13)
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; 21,798,551 issued and 19,376,594 outstanding at September 30, 2020 and 21,297,317 issued and 19,075,360 outstanding at September 30, 2019	0.2	0.2
Common stock in treasury, at cost - 2,421,957 shares at September 30, 2020 and 2,221,957 shares at September 30, 2019	(57.6)	(50.1)
Additional paid-in-capital	292.6	276.8
Retained earnings	572.4	402.1
Accumulated other comprehensive loss, net	(40.1)	(34.8)
Total equity	767.5	594.2
Total liabilities and stockholders' equity	$ 13,474.9	$ 9,936.1

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Statement of Financial Position [Abstract]
Securities and other assets segregated, fair value	$ 2.6	$ 306
Deposits and receivables from broker dealer at fair value	1,775.8	626.9
Financial instrument owned, at fair value	468.6	478.8
Physical commodities inventory, net at fair value	215.7	151.9
Accounts payable and other accrued at fair value	1.5	1.8
Payables to broker dealer at fair value	$ 14.7	$ 5.6
Preferred stock - par value (in dollar per share)	$ 0.01	$ 0.01
Preferred stock - authorized (in shares)	1,000,000	1,000,000
Preferred stock - issued (in shares)	0	0
Preferred stock - outstanding (in shares)	0	0
Common stock - par value (in dollar per share)	$ 0.01	$ 0.01
Common stock - authorized (in shares)	30,000,000	30,000,000
Common stock - issued (in shares)	21,798,551	21,297,317
Common stock - outstanding (in shares)	19,376,594	19,075,360
Treasury stock - shares (in shares)	2,421,957	2,221,957

Consolidated Income Statements

Consolidated Income Statements - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Sales of physical commodities	$ 52,899.2	$ 31,830.3	$ 26,682.4
Principal gains, net	622.2	415.8	354.1
Revenue from contract with customer	487.3	452	462.9
Interest income	130.9	198.9	123.3
Total revenues	54,139.6	32,897	27,622.7
Cost of sales of physical commodities	52,831.3	31,790.9	26,646.9
Operating revenues	1,308.3	1,106.1	975.8
Transaction-based clearing expenses	222.5	183.5	179.7
Introducing broker commissions	113.8	114.7	133.8
Interest expense	80.4	142	70.5
Interest expense on corporate funding	23.6	12.7	10.2
Net operating revenues	868	653.2	581.6
Compensation and other expenses:
Compensation and benefits	518.7	393.1	337.7
Trading systems and market information	46.3	38.8	34.7
Professional fees	30.2	21	18.1
Non-trading technology and support	28.4	20.1	13.9
Occupancy and equipment rental	23.5	19.4	16.5
Selling and marketing	12.2	5.2	6.2
Travel and business development	8.9	16.2	13.8
Communications	7	6.6	5.4
Depreciation and amortization	19.7	14	11.6
Bad debts, net of recoveries and impairment	18.7	2.5	3.1
(Recovery) bad debt on physical coal	0	(12.4)	1
Other	29.6	23.2	20.1
Total compensation and other expenses	743.2	547.7	482.1
Gain on acquisitions and other gains	81.9	5.5	2
Income before tax	206.7	111	101.5
Income tax expense	37.1	25.9	46
Net income (loss)	$ 169.6	$ 85.1	$ 55.5
Earnings per share:
Basic (in dollar per share)	$ 8.78	$ 4.46	$ 2.93
Diluted (in dollar per share)	$ 8.61	$ 4.39	$ 2.87
Weighted-average number of common shares outstanding:
Basic (in shares)	18,824,328	18,738,905	18,549,011
Diluted (in shares)	19,180,479	19,014,395	18,934,830
Commission and Clearing Fees [Member]
Revenues:
Revenue from contract with customer	$ 403.6	$ 372.4	$ 391.8
Consulting, Management, and Account Fees [Member]
Revenues:
Revenue from contract with customer	$ 83.7	$ 79.6	$ 71.1

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 169.6	$ 85.1	$ 55.5
Other comprehensive loss, net of tax:
Foreign currency translation adjustment	(4.5)	(0.8)	(9)
Pension liabilities adjustment	(0.2)	(0.8)	0.3
Reclassification of adjustment for losses (gains) included in net income:
Periodic pension costs (included in compensation and benefits)	0.1	0.1	0.1
Foreign currency gains realized upon dissolution of subsidiaries (included in principal gains, net)	0	(0.2)	0
Reclassification adjustment for losses (gains) included in net income	0.1	(0.1)	0.1
Other comprehensive loss	(4.6)	(1.7)	(8.6)
Comprehensive income	$ 165	$ 83.4	$ 46.9

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 169.6	$ 85.1	$ 55.5
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Recovery) bad debt on physical coal	0	(2.4)	1
Depreciation and amortization	19.7	14	11.6
Amortization of operating right of use assets	9.9
Provision for bad debts, net of recoveries and impairment	18.7	2.5	3.1
Deferred income taxes	4.1	3.7	22.3
Amortization and extinguishment of debt issuance costs	6.5	1.5	1
Actuarial gain on pension and postretirement benefits	(0.2)	(0.3)	(0.3)
Amortization of share-based compensation expense	10.3	8.1	6.6
Gain on acquisition	(81.9)	(5.5)	0
Changes in operating assets and liabilities, net:
Cash, securities and other assets segregated under federal and other regulations	293	337.2	(626.7)
Securities purchased under agreements to resell	(271.7)	(553.7)	(464.9)
Securities borrowed	(16.8)	(1,197.7)	(138.8)
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	(326)	(241.7)	(292.9)
Receivable from clients, net	0.9	(134.3)	(24.3)
Notes receivable, net	1.2	0.9	6.8
Income taxes receivable	(11.1)	(4.2)	(1.3)
Financial instruments owned, at fair value	(552.5)	(113.3)	(308.7)
Physical commodities inventory	(51.8)	3	(98.7)
Other assets	(3.7)	(8.3)	(3.3)
Accounts payable and other accrued liabilities	42.7	6.7	18.6
Operating lease liabilities	(9.5)
Payable to clients	2,093.7	(46.8)	520
Payable to broker-dealers, clearing organizations and counterparties	270.8	176.4	(27.8)
Income taxes payable	(0.3)	1.8	3.2
Securities sold under agreements to repurchase	381.8	837	543.7
Securities loaned	(18)	1,182	166.8
Financial instruments sold, not yet purchased, at fair value	(28.8)	(156.1)	153.9
Net cash provided by (used in) operating activities	1,950.6	195.6	(473.6)
Cash flows from investing activities:
Cash paid for acquisitions	(225)	(28.9)	(3.7)
Sale of clearing organization common stock	0	0	0.8
Purchase of property and equipment	(16.6)	(11.9)	(12.5)
Net cash used in investing activities	(241.6)	(40.8)	(15.4)
Cash flows from financing activities:
Net change in lenders under loans with maturities 90 days or less	99.7	(162.6)	125.8
Proceeds from lenders under loans with maturities greater than 90 days	608.5	357.2	0
Repayments of lenders under loans with maturities greater than 90 days	(642)	(346.7)	0
Proceeds from issuance of senior secured term loan	21.5	175	0
Repayments of senior secured term loan	(9.8)	(6.6)	0
Proceeds from issuance of senior secured notes	344.8	0	0
Repayment of senior secured notes	(92.1)	0	0
Repayments of note payable	(0.4)	(0.8)	(0.8)
Deferred payments on acquisitions	(0.9)	0	(5.5)
Share repurchase	(7.5)	(3.8)	0
Debt issuance costs	(15)	(3.3)	(0.4)
Exercise of stock options	5.5	1.2	2.6
Withholding taxes on stock option exercises	0	0	(0.8)
Net cash provided by financing activities	312.3	9.6	120.9
Effect of exchange rates on cash, segregated cash, cash equivalents, and segregated cash equivalents	(4.2)	(0.7)	(4.1)
Net increase (decrease) in cash, segregated cash, cash equivalents, and segregated cash equivalents	2,017.1	163.7	(372.2)
Cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period	2,451.3	2,287.6	2,659.8
Cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period	4,468.4	2,451.3	2,287.6
Supplemental disclosure of cash flow information:
Cash paid for interest	90.4	153.2	78.9
Income taxes paid, net of cash refunds	44	24.6	22.2
Supplemental disclosure of non-cash investing and financing activities:
Identified intangible assets and goodwill on acquisitions	11.8	10.8	3.9
Additional consideration payable related to acquisitions	21.6	1.8	0
Acquisition of businesses:
Assets acquired	1,169.2	47.1	1.7
Liabilities acquired	(359.5)	(8.9)	(1.9)
Total net assets acquired	809.7	38.2	(0.2)
Total cash, segregated cash, cash equivalents, and segregated cash equivalents shown in the consolidated statements of cash flows	$ 4,468.4	$ 2,287.6	$ 2,287.6

Consolidated Statements of Stoc

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock [Member]	Common Stock [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Treasury Stock [Member]	Treasury Stock [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Other Comprehensive Loss, Net [Member]	Accumulated Other Comprehensive Loss, Net [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Loss, Net [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Beginning balance at Sep. 30, 2017	$ 449.9		$ 0.2		$ (46.3)		$ 259		$ 261.5			$ (24.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	55.5								55.5
Other comprehensive loss	(8.6)											(8.6)
Exercise of stock options	1.9						1.9
Share-based compensation	6.6						6.6
Ending balance at Sep. 30, 2018	505.3		0.2		(46.3)		267.5		317			(33.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85.1								85.1
Other comprehensive loss	(1.7)											(1.7)
Exercise of stock options	1.2						1.2
Share-based compensation	8.1						8.1
Repurchase of stock	(3.8)				(3.8)
Ending balance at Sep. 30, 2019	$ 594.2	$ 594.2	0.2	$ 0.2	(50.1)	$ (50.1)	276.8	$ 276.8	402.1	$ 0.7	$ 402.8	(34.8)	$ (0.7)	$ (35.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member
Net income	$ 169.6								169.6
Other comprehensive loss	(4.6)											(4.6)
Exercise of stock options	5.5						5.5
Share-based compensation	10.3						10.3
Repurchase of stock	(7.5)				(7.5)
Ending balance at Sep. 30, 2020	$ 767.5		$ 0.2		$ (57.6)		$ 292.6		$ 572.4			$ (40.1)

Description of Business and Sig

Description of Business and Significant Accounting Policies	12 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Description of Business and Significant Accounting Policies	Description of Business and Significant Accounting Policies StoneX Group Inc., a Delaware corporation, and its consolidated subsidiaries (collectively “SNEX” or “the Company”), is a global financial services network that connects companies, organizations, traders and investors to the global market ecosystem through a unique blend of digital platforms, end-to-end clearing and execution services, high touch service and deep expertise. The Company strives to be the one trusted partner to its clients, providing its network, product and services to allow them to pursue trading opportunities, manage their market risks, make investments and improve their business performance. The Company offers a vertically integrated product suite, beginning with high-touch and electronic access to nearly all major financial markets worldwide, as well as numerous liquidity venues. It delivers this access through the entire lifecycle of a trade, from deep market expertise and on-the-ground intelligence, to best execution and finally post-trade clearing, custody and settlement services. The Company has created a revenue stream that is diversified by asset class, client type and geography, earning commissions and spreads as clients execute transactions across our financial network, monetizing non-trading client activity including interest and fee earnings on client balances as well as earning consulting and fees for our market intelligence and risk management services. The Company provides these services to a diverse group of more than 32,000 commercial and institutional clients and over 330,000 retail clients located in more than 130 countries, including commercial entities, asset managers, regional, national and introducing broker-dealers, insurance companies, brokers, institutional investors and professional traders, commercial and investment banks and government and non-governmental organizations (“NGOs”). The Company’s shareholders voted and approved to change the Company’s name from INTL FCStone Inc. to StoneX Group Inc. on June 24, 2020. The change in the Company’s name became effective on July 7, 2020 and the Company’s common stock began trading on The NASDAQ Global Select Market under the symbol “SNEX”. Basis of Presentation The accompanying consolidated financial statements include the accounts of StoneX Group Inc. and all other entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. Unless otherwise stated herein, all references to fiscal 2020, fiscal 2019, and fiscal 2018 refer to the Company’s fiscal years ended September 30. In the consolidated income statements, the total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. The subtotal ‘operating revenues’ in the consolidated income statements is calculated by deducting physical commodities cost of sales from total revenues. The subtotal ‘net operating revenues’ in the consolidated income statements is calculated as operating revenues less transaction-based clearing expenses, introducing broker commissions and interest expense. Transaction-based clearing expenses represent variable expenses paid to executing brokers, exchanges, clearing organizations and banks in relation to transactional volumes. Introducing broker commissions include commission paid to non-employee third parties that have introduced clients to the Company. Net operating revenues represent revenues available to pay variable compensation to risk management consultants and traders and direct non-variable expenses, as well as variable and non-variable expenses of operational and administrative employees. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments, revenue recognition, the provision for probable losses from bad debts, valuation of inventories, and incomes taxes and contingencies. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. The Company reviews all significant estimates affecting the financial statements on a recurring basis and records the effect of any necessary adjustments prior to their issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. Internal Subsidiaries Consolidation As discussed further in Note 21, on January 14, 2019 the Company acquired 100% of the U.S.-based broker-dealer GMP Securities LLC (“GMP”). Subsequent to the acquisition date, the legal name of GMP was changed to INTL FCStone Credit Trading LLC (“IFT”). Effective May 1, 2019, the Company merged IFT into StoneX Financial Inc. (“StoneX Financial”). As such, the assets, liabilities and equity of IFT were transferred into StoneX Financial. Reclassifications During the year ended September 30, 2020, the Company reclassified certain selling and marketing related costs in connection with the acquisition of Gain Capital Holdings, Inc. (“Gain”). In performing this reclassification, the Company has made retrospective adjustments to the consolidated income statements for the years ended September 30, 2019 and 2018. For the years ended September 30, 2019 and 2018, selling and marketing related costs of $5.2 million and $6.2 million, were reclassified from ‘Other’ expense to ‘Selling and marketing’ expense. During the year ended September 30, 2019, the Company reclassified certain brokerage related revenues for which the Company earns commissions on trading activity in the capacity of an agent. In performing this reclassification, the Company has made a retrospective adjustment to the consolidated income statement for the year ended September 30, 2018. For the year ended September 30, 2018, brokerage related revenue of $35.0 million, was reclassified from ‘principal gains, net’ to ‘commissions and clearing fees’. Additionally, the Company has changed the name of the line item ‘trading gains, net’ to ‘principal gains, net’ on the consolidated income statement 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. Foreign Currency Translation The Company’s consolidated financial statements are reported in U.S. dollars. The Company’s foreign subsidiaries maintain their records either in U.S. dollars or in certain instances the currency of the country in which they operate. The method of translating local currency financial information into U.S. dollars depends on whether the economy in which the foreign subsidiary operates has been designated as highly inflationary or not. Economies with a three-year cumulative inflation rate of more than 100% are considered highly inflationary. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expense are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in earnings. Foreign subsidiaries that operate in highly inflationary countries use the U.S. dollar as their functional currency. Local currency monetary assets and liabilities are remeasured into U.S. dollars using rates of exchange as of each balance sheet date, with remeasurement adjustments and other transaction gains and losses recognized in earnings. Nonmonetary assets and liabilities do not fluctuate with changes in the local currency exchange rates to the dollar as the translated amounts for nonmonetary assets and liabilities at the end of the accounting period in which the economy becomes highly inflationary becomes the accounting basis for those assets and liabilities in the period of change and subsequent periods. Revenues and expenses are translated at rates of exchange in effect during the year. The Company operates asset management and debt trading businesses in Argentina through various wholly-owned subsidiaries. Operating revenues from the Argentinean subsidiaries represented approximately 2% of the consolidated operating revenues for the year ended September 30, 2020. The operating environment in Argentina continues to present business challenges, including ongoing devaluation of the Argentine peso and significant inflation. For the year ended September 30, 2018, the Argentine peso declined approximately 139% (from 17.3 to 41.3 pesos to the U.S. dollar). Based upon inflationary data published by the International Practices Task Force of the Center for Audit Quality, the economy of Argentina became highly inflationary during the three months ended June 30, 2018. Beginning July 1, 2018, the Company designated Argentina’s economy as highly inflationary for accounting purposes. As a result, the Company has accounted for the Argentinean entities using the U.S. dollar as their functional currency beginning in the quarter ending September 30, 2018. Argentine peso-denominated monetary assets and liabilities are remeasured at each balance sheet date to the currency exchange rate then in effect, with currency remeasurement gains and loses recognized in earnings. The translated balances for nonmonetary assets and liabilities as of June 30, 2018, became the accounting basis for those assets in the period of change and subsequent periods. As a result of Argentina’s highly inflationary status, the Company recorded translation losses through earnings of $3.9 million and $3.4 million for the years ended September 30, 2019 and 2018, respectively. Translation adjustments recorded through earnings were de minimis for the year ended September 30, 2020, as the Company has implemented strategies to reduce the exposure to the Argentine peso. At September 30, 2020, the Company had net monetary liabilities denominated in Argentine pesos of $0.1 million, compared to net monetary assets of $5.5 million at September 30, 2019. The Company held cash and cash equivalents denominated in Argentine pesos of $0.1 million and $1.4 million as of September 30, 2020 and 2019, respectively. At September 30, 2020 and 2019, the Company had net nonmonetary assets denominated in Argentine pesos of $0.9 million and $1.0 million, respectively. Cash and Cash Equivalents The Company considers cash held at banks and all highly liquid investments not held for trading purposes, with original or acquired maturities of 90 days or less, including certificates of deposit and money market mutual funds, to be cash and cash equivalents. Cash and cash equivalents consists of cash, certificates of deposit, and money market mutual funds not deposited with or pledged to clearing organizations, broker-dealers, clearing organizations or counterparties, or segregated under federal or other regulations. Certificates of deposit are stated at cost plus accrued interest, which approximates fair value, and may be withdrawn at any time at the discretion of the Company without penalty. Money market mutual funds are stated at their net asset value. Cash, Securities and Other Assets Segregated under Federal and other Regulations Pursuant to requirements of the Commodity Exchange Act and Commission Regulation 30.7 of the U.S. Commodity Futures Trading Commission (“CFTC”) in the U.S., the Markets in Financial Instruments Implementing Directive 2006/73/EC underpinning the Client Asset (“CASS”) rules in the Financial Services Authority (“FSA”) handbook in the United Kingdom (“U.K.”), and the Securities & Futures Act (“SFA”) in Singapore, funds deposited by clients relating to futures and options on futures contracts in regulated commodities must be carried in separate accounts which are designated as segregated or secured client accounts. Additionally, in accordance with Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), the Company maintains separate accounts for the exclusive benefit of securities clients and proprietary accounts of broker dealers (“PABs”). Rule 15c3-3 requires the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. The deposits in segregated client accounts and SRBAs are not commingled with the funds of the Company. Under the FSA’s rules, certain categories of clients may choose to opt-out of segregation. As of September 30, 2020 and September 30, 2019, cash, securities, and other assets segregated under federal and other regulations consisted of cash held at banks of approximately $1,907.2 million and $743.9 million, respectively, U.S. Treasury obligations of approximately $10.6 million and $299.8 million, respectively, and commodities warehouse receipts of approximately $2.4 million and $6.2 million, respectively (see fair value measurements discussion in Note 5). Collateralized Transactions The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed transactions, and securities loaned transactions primarily to fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, or meet counterparty needs under matched-booked trading strategies. These transactions are accounted for as collateralized financing transactions and are recorded at their contractual amounts plus accrued interest. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to collateralize such agreements and transactions in accordance with contractual arrangements. The Company monitors the fair value of the collateral on a daily basis and the Company may require counterparties, or may be required by counterparties, to deposit additional collateral or return collateral pledged. Interest income and interest expense are recognized over the life of the arrangements and are recorded in the statement of income as interest income or interest expense, as applicable. The carrying amount of these transactions approximate fair value due to their short-term nature and the level of collateralization. These transactions are reported gross, except when a right of offset exists and the other criteria for netting under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 210-20, Balance Sheet - Offsetting are met. Deposits with and Receivables from Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties As required by regulations of the CFTC, FSA, and Monetary Authority of Singapore (“MAS”), client funds received to margin, guarantee, and/or secure commodity futures and futures on options as well as retail foreign exchange transactions are segregated and accounted for separately from the general assets of the Company. Deposits with broker-dealers, clearing organizations, and counterparties pertain primarily to deposits made to satisfy margin requirements on client and proprietary open futures and options on futures positions and to satisfy the requirements set by clearing exchanges for clearing membership. The Company also pledges margin deposits with various counterparties for over-the-counter (“OTC”) derivative contracts, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. The Company also deposits cash margin with various securities clearing organizations as an ongoing condition of the securities clearing relationships, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties are reported gross, except where a right of offset exists. As of September 30, 2020 and September 30, 2019, the Company had cash and cash equivalents on deposit with or pledged to broker-dealers, clearing organizations, and counterparties of approximately 1.6 billion. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes guaranty deposits with clearing exchanges. The guaranty deposits are held by the clearing exchanges for use in potential default situations by one or more members of the clearing exchanges. The guaranty deposits may be applied to the Company’s obligations to the clearing exchange, or to the clearing exchange’s obligations to unrelated parties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include securities pledged to clearing exchanges. These securities are either pledged to the Company by its clients or represent investments of client funds. It is the Company’s practice to include client-owned securities on its consolidated balance sheets, as the rights to those securities have been transferred to the Company under the terms of the futures trading agreements. Securities pledged primarily include U.S. Treasury obligations, foreign government obligations, and certain exchange-traded funds (“ETFs”). Securities that are not client-owned, and represent an investment of client funds, are adjusted to fair value with associated changes in unrealized gains or losses recorded in ‘interest income’ in the consolidated income statements. For client-owned securities, the change in fair value is offset against the payable to clients with no impact recognized in the consolidated income statements. The fair value of these securities included within deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $1,949.3 million and $603.8 million as of September 30, 2020 and September 30, 2019, respectively. Management has considered guidance required by ASC 860, Transfers and Servicing as it relates to securities pledged by clients to margin their futures and options on futures trading accounts. Based on a review of the agreements with the client, management believes the transferor surrenders control over those assets because: (a) the transferred assets have been isolated from the transferor—put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (b) each transferee has the right to pledge or exchange the assets (or beneficial interests) it received, and no condition both constrains the transferee (or holder) from taking advantage of its right to pledge or exchange and provides more than a trivial benefit to the transferor and (c) the transferor does not maintain effective control over the transferred assets through either (1) an agreement that both entitles and obligates the transferor to repurchase or redeem them before their maturity or (2) the ability to unilaterally cause the holder to return specific assets, other than through a cleanup call. Under this guidance, the Company reflects the client collateral assets and corresponding liabilities in the Company’s consolidated balance sheets as of September 30, 2020 and September 30, 2019. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes amounts due from clearing exchanges for unrealized gains and losses associated with clients’ options on futures contracts. See discussion in the Financial Instruments section below for additional information on the Company’s accounting policies for derivative contracts. For client-owned derivative contracts, the fair value is offset against the payable to clients with no impact recognized on the consolidated income statements. The Company maintains client omnibus and proprietary accounts with other clearing organizations, and the equity balances in those accounts along with any margin cash or securities deposited with the clearing organizations are included in deposits with and receivables from broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include amounts due from or due to clearing exchanges for daily variation settlements on open futures and options on futures positions. The variation settlements due from or due to clearing exchanges are paid in cash on the following business day. Variation settlements equal the daily settlement of futures contracts and premiums on options on futures contracts. Receivables from broker-dealers and counterparties also include amounts receivable for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payables to broker-dealers and counterparties primarily include amounts payable for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivables from broker-dealers, clearing organizations and counterparties, and payables to broker-dealers, clearing organizations and counterparties also include amounts related to the value of registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. Receivable from and Payable to Clients Receivable from clients, net of the allowance for doubtful accounts, include the total of net deficits in individual exchange-traded futures and OTC derivative trading accounts carried by the Company. Client deficits arise from realized and unrealized trading losses on client futures, options on futures, swaps and forwards and amounts due on cash and margin transactions. Client deficit accounts are reported gross of client accounts that contain net credit or positive balances, except where a right of offset exists. Net deficits in individual futures exchange-traded and OTC derivative trading accounts include both secured and unsecured deficit balances due from clients as of the balance sheet date. Secured deficit amounts are backed by U.S. Treasury obligations and commodity warehouse receipts. These U.S Treasury obligations and commodity warehouse receipts are not netted against the secured deficit amounts, as the conditions for right of setoff have not been met. See note 13 for additional discussion of client deficit accounts originating in November 2018. Receivable from clients, net also includes the net amounts receivable from securities clients in connection with the settlement of regular-way cash securities, margin loans to clients, and client cash debits. It is the Company’s policy to report margin loans and payables that arise due to positive cash flows in the same client’s accounts on a net basis when the conditions for netting as specified in U.S. GAAP are met. Clients’ securities transactions cleared by the Company are recorded on a settlement date basis. Securities cleared by the Company and pledged to the Company as a condition of the custodial clearing arrangements are owned by the clients, including those that collateralize margin or other similar transactions, and are not reflected on the consolidated balance sheets as the Company does not have title to, or beneficial interests, in those assets. In the event of uncompleted transactions on settlement date, the Company records corresponding receivables and payables, respectively. The carrying value of the receivables and payables approximates fair value due to their short-term nature. Receivables from clients, net also include amounts receivable from non-broker-dealer clients for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payable to clients represent the total of client accounts with credit or positive balances. Client accounts are used primarily in connection with exchange-traded and OTC commodity, foreign exchange, precious metals, and securities transactions and include gains and losses on open trades as well as securities and cash margin deposits made as required by the Company, the exchange-clearing organizations or other clearing organizations. Client accounts with credit or positive balances are reported gross of client deficit accounts, except where a right of offset exists. Payables to broker-dealers and counterparties also includes amounts payable to non-broker-dealer clients for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivable from and payables to clients also include amounts related to the value of non-registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. The future collectability of receivables from clients can be impacted by the Company’s collection efforts, the financial stability of its clients, and the general economic climate in which it operates. The Company evaluates accounts that it believes may become uncollectible on a specific identification basis, through reviewing daily margin deficit reports, the historical daily aging of the receivables, and by monitoring the financial strength of its clients. The Company may unilaterally close client trading positions in certain circumstances. In addition, to evaluate client margining and collateral requirements, client positions are stress tested regularly and monitored for excessive concentration levels relative to the overall market size. Furthermore, in certain instances, the Company is indemnified, and able to charge back, introducing broker-dealers for bad debts incurred by their clients. The Company generally charges off an outstanding receivable balance when all economic means of recovery have been exhausted. That determination considers information such as the occurrence of significant changes in the client’s financial position such that the client can no longer pay the obligation, or that the proceeds from collateral will not be sufficient to pay the balance. Notes Receivable Accrual of commodity financing income on any note is discontinued when, in the opinion of management, there is reasonable doubt as to the timely collectability of interest or principal. Nonaccrual notes are returned to an accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely payment of principal and interest. The Company records a charge against earnings for notes receivable losses when management believes that the collection of outstanding principal is not probable. Physical Commodities Inventory Inventories of certain agricultural commodities are carried at net realizable value, which approximates fair value less disposal costs. The agricultural commodities inventories have reliable, readily determinable and realizable market prices, have relatively predictable and insignificant costs of disposal and are available for immediate delivery. Changes in the fair values of these agricultural commodities inventories are included as a component of ‘cost of sales of physical commodities’ in the consolidated income statements. Inventories of energy related products are valued at the lower of cost or net realizable value. Inventories of precious metals held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value, using the weighted-average price and first-in first-out costing method. Precious metals inventory held by StoneX Financial Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ in the consolidated income statements. Property and Equipment Property and equipment is stated at cost, net of accumulated depreciation and amortization and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the estimated useful life of the improvement or the term of the lease, whichever is shorter. Expenditures that increase the value or productive capacity of assets are capitalized. When property and equipment are retired, sold, or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in earnings. The Company accounts for costs incurred to develop its trading platforms and related software in accordance with ASC 350-40, Internal-Use Software. ASC 350-40 requires that such technology be capitalized in the application development stages. Costs related to training, administration and non-value added maintenance are charged to expense as incurred. Capitalized software development costs are amortized over the useful life of the software, which the Company estimates at three years. In accordance with ASC 360-10, Property, Plant and Equipment, the Company periodically evaluates the carrying value of long-lived assets when events and circumstances warrant such review. The carrying value of a long-lived asset is considered impaired when the anticipated identifiable undiscounted cash flows from such an asset (or asset group) are less than carrying value. In that event, a loss is recognized in the amount by which the carrying value exceeds fair market value of the long-lived asset. This standard applies to assets held for use and not to assets held for sale. The Company has no assets held for sale. The Company has identified no such impairment indicators as of September 30, 2020 or 2019. Acquisitions The Company applies acquisition accounting on the date of acquisition to those transactions meeting the definition of a business under ASC 805. Applying acquisition accounting requires the Company to allocate the purchase consideration to the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed on the acquisition date. In determining the fair value of identifiable assets acquired and liabilities assumed, the Company frequently utilize the assistance of a third-party valuation specialist. The Company applies certain significant assumptions, estimates, and judgments in determining the fair value of assets acquired and liabilities assumed on the acquisition date. These significant assumptions, estimates, and judgements include, but are not limited to, cash flow forecasts, discount rates, client churn rates, royalty rates, and economic lives. Any excess of the purchase consideration over the fair value of the net assets acquired is recorded as goodwill. Alternatively, in an instance where the fair value of the net assets acquired exceeds the purchase consideration, the Company records a bargain purchase gain in the consolidated income statement at the date of acquisition. While the Company uses its best estimates and assumptions as a part of the purchase price allocation to accurately value assets acquired and liabilities assumed at the acquisition date, these estimates are inherently uncertain and subject to refinement. As a result, during the remeasurement period, which may extend one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill or bargain purchase gain. Upon conclusion of the measurement period or final determination of the fair values of assets acquired and liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the consolidated income statements rather than adjusted through goodwill or bargain purchase gains. The Company includes the post-acquisition results of acquired businesses in the consolidated income statements from the date of acquisition. Acquisition related costs, such as fees for attorneys, accountants, and investm

Leases

Leases	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	Leases The Company currently leases office space under non-cancelable operating leases with third parties as of September 30, 2020. Leases with an initial term of 12 months or less are not recorded on the condensed consolidated balance sheet and the Company recognizes lease expense for these leases on a straight-line basis over the lease term. Certain office space leases include one or more options to renew, with renewal terms that can extend the lease term from three As the office space leases do not provide an implicit rate, the Company applies a collateralized incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. The Company applied a collateralized incremental borrowing rate as of October 1, 2019 for operating leases that commenced prior to that date. For office space leases executed by subsidiaries, including foreign subsidiaries, the Company has applied the incremental borrowing rate of the parent company. The Company believes this is a reasonable approach as its subsidiaries either do not have their own treasury functions or the credit facilities available to its subsidiaries do not permit the financing of right-of-use assets. Additionally, in certain instances, the parent company provides a guarantee of the lease payments to the lessor under office space leases executed by its subsidiaries. As such, the Company believes that the pricing of subsidiary leases is more significantly influenced by the credit standing of the parent company than that of its subsidiaries. Certain office space leases contain variable lease payments related to fair market rent adjustments and local inflation index measures. The Company estimates variable lease payments based upon information available at the lease commencement date in determining the present value of lease payments. The Company applied information available as of October 1, 2019 for operating leases that commenced prior to that date. The Company has elected to not separate lease components from nonlease components for all office space leases. The Company does not have any financing leases as of September 30, 2020. Operating lease expense is recognized on a straight-line basis over the lease term and is reported within ‘occupancy and equipment rental’ on the condensed consolidated statement of income. As of September 30, 2020, the Company recorded operating lease right-of-use assets and operating lease liabilities of $101.5 million and $118.7 million, respectively. As of October 1, 2019, in conjunction with the adoption of the new accounting standard, the Company recorded operating lease right-of-use assets and operating lease liabilities of $33.1 million and $36.2 million, respectively. The following table presents operating lease costs and other related information as of and for the year ended September 30, 2020 (in millions, except as stated): Year Ended September 30, 2020 Operating lease costs (1) $ 17.2 Supplemental cash flow information and non-cash activity: Cash paid for amounts included in the measurement of operating lease liabilities $ 12.1 Right-of-use assets obtained in exchange for operating lease liabilities $ 96.4 Lease term and discount rate information: Weighted average remaining lease term (years) 11.3 Weighted average discount rate 4.3 % (1) Includes short-term leases and variable lease costs, which are immaterial. The maturities of the lease liabilities are as follows as of September 30, 2020 (in millions): 2021 $ 16.0 2022 15.3 2023 13.6 2024 11.8 2025 11.0 After 2025 82.6 Total lease payments 150.3 Less: interest 31.6 Present value of lease liabilities $ 118.7 In accordance with the disclosure requirements for the adoption of Topic 842, the Company is presenting its operating lease commitment table as of September 30, 2019, which was previously disclosed in Note 12 of the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2019 (in millions): 2020 $ 11.2 2021 9.9 2022 7.5 2023 6.2 2024 5.8 Thereafter 2.6 $ 43.2

Revenue from Contracts with Cli

Revenue from Contracts with Clients	12 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Clients	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 0.9%, 1.4%, and 1.7% of the Company’s total revenues for the years ended September 30, 2020, 2019, and 2018 respectively. The Company’ revenues from contracts with clients subject to Topic 606 represent approximately 37.2%, 40.9%, and 47.4% of the Company’s operating revenues for the years ended September 30, 2020, 2019, and 2018, respectively. Revenues within the scope of Topic 606 are presented within ‘Commission and clearing fees’ and ‘Consulting, management, and account fees’ on the consolidated income statements. Revenues that are not within the scope of Topic 606 are presented within ‘sales of physical commodities’, ‘principal gains, net’, and ‘interest income’ on the consolidated income statements. The following table represents a disaggregation of the Company’s total revenues separated between revenues from contracts with clients and other sources of revenue for the years ended September 30, 2020, 2019, and 2018 (in millions): Year Ended September 30, 2020 2019 2018 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 143.7 $ 144.9 $ 163.4 OTC derivative brokerage 19.7 32.1 30.3 Equities and fixed income 39.9 16.1 11.2 Mutual funds 5.2 7.5 7.2 Insurance and annuity products 8.4 7.3 5.8 Other 1.4 1.3 0.9 Total sales-based commission 218.3 209.2 218.8 Trailing: Mutual funds 12.9 12.4 13.2 Insurance and annuity products 15.3 14.4 14.6 Total trailing commission 28.2 26.8 27.8 Clearing fees 139.0 118.8 123.3 Trade conversion fees 8.9 7.5 6.8 Other 9.2 10.1 15.1 Total commission and clearing fees: 403.6 372.4 391.8 Consulting, management, and account fees: Underwriting fees 0.6 0.7 1.7 Asset management fees 31.3 26.2 24.8 Advisory and consulting fees 22.2 20.0 19.0 Sweep program fees 9.5 16.3 11.6 Client account fees 12.3 10.6 11.1 Other 7.8 5.8 2.9 Total consulting, management, and account fees 83.7 79.6 71.1 Total revenues from contracts with clients $ 487.3 $ 452.0 $ 462.9 Method of revenue recognition: Point-in-time $ 396.1 $ 362.7 $ 379.7 Time elapsed 91.2 89.3 83.2 Total revenues from contracts with clients 487.3 452.0 462.9 Other sources of revenues Physical precious metals trading 51,598.5 30,694.5 25,762.9 Physical agricultural and energy product trading 1,300.7 1,135.8 919.5 Principal gains, net 622.2 415.8 354.1 Interest income 130.9 198.9 123.3 Total revenues $ 54,139.6 $ 32,897.0 $ 27,622.7 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 and consulting, management, and account fees revenue are primarily related to the Commercial and Institutional reportable segments. Principal gains, net are contributed by all of the Company’s reportable segments. Interest income is primarily related to the Commercial and Institutional reportable segments. Precious metals trading and agricultural and energy product trading revenues are primarily related to the Commercial reportable segment. Commission and Clearing Fees Commission revenue represents sales and brokerage commissions generated by internal brokers, introducing broker-dealers, or registered investment advisors of introducing-broker dealers for their clients’ trading activity in futures, options on futures, OTC derivatives, fixed income securities, equity securities, mutual funds, and annuities. The Company views the selling, distribution, and marketing, or any combination thereof, of mutual funds and insurance and annuity products to clients on the Company’s registered investment advisor (“RIA”) platform as a single performance obligation to the product sponsors. The Company is the principal for commission revenue, as it is responsible for the execution of the clients’ purchases and sales, and maintains relationships with product sponsors for trailing commission. Introducing broker dealers and registered investment advisors assist the Company in performing its obligations. Accordingly, total commission revenues are reported on a gross basis. The Company primarily generates commission revenue on exchange-traded derivatives, OTC derivatives, and securities. Exchange-traded and OTC derivative commissions are recognized at a point in time on the trade date when the client, either directly or through the use of an internal broker or introducing broker, requests the clearance and execution of a trade. Securities commissions are either sale-based commissions that are recognized at a point in time on the trade date or trailing commission that are recognized over time as earned. Sales-based securities commissions are typically a flat fee per security transaction and in certain instances are based on a percentage of the trade date transaction value. Trailing commission revenue is generally based on a percentage of the periodic fair value of clients’ investment holdings in trail-eligible assets, and is recognized over the period during which services, such as on-going support, are performed. As trailing commission revenue is based on the fair value of clients’ investment holdings in trail-eligible assets, this variable consideration is constrained until the fair value of trail-eligible assets is determinable. Clearing fees generally represent transactional based fees charged by the various exchanges and clearing organizations for which the Company or one of its clearing brokers is a member for the privilege of executing and clearing trades through them. Clearing fees are generally passed through to the clients’ accounts and are reported gross as the Company maintains control over the clearing and execution services provided, maintains relationships with the exchanges or clearing brokers, and has ultimate discretion in whether the fees are passed through to the clients and the rates at which they are passed through. As clearing fees are transactional based revenues they are recognized at a point in time on the trade date along with the related commission revenue when the client requests the clearance and execution of a trade. Trade Conversion Fees Trade conversion fees include revenue earned from converting foreign ordinary equities into an American Depository Receipt (“ADR”) or Global Depository Receipt (“GDR”) and fees earned from converting an ADR or GDR into foreign ordinary equities on behalf of clients. Trade conversion revenue is recognized at a point in time on the trade date. Underwriting Fees Revenues from investment banking consists of revenues earned from underwriting fixed income securities, primarily municipal and asset-backed securities, and are recognized in revenues upon completion of the underlying transaction, which is generally the trade date, based upon the terms of the assignment as the performance obligation is to successfully broker a specific transaction. Asset Management Fees The Company earns asset management fees on Company sponsored and managed mutual funds and on the advisory accounts of independent registered investment advisors on the Company’s platform. The Company provides ongoing investment advice and acts as a custodian, providing brokerage and execution services on transactions, and performs administrative services for these accounts. This series of performance obligations transfers control of the services to the client over time as the services are performed. This revenue is recognized ratably over time to match the continued delivery of the performance obligations to the client over the life of the contract. The asset management revenue generated is based on a percentage of the market value of the eligible assets in the clients’ accounts. As such, the consideration for this revenue is variable and this variable consideration is constrained until the market value of eligible assets in the clients’ accounts is determinable. Advisory and Consulting Fees Advisory and consulting fees are primarily related to risk management consulting fees which are billed and recognized as revenue on a monthly basis when risk management services are provided. Risk management consulting contracts are generally for a minimum term of six months and then continue from month to month, but may be terminated at any time after the original six months by either party upon providing written notice. Advisory and consulting fees are not variable based on client trading activities. This revenue is generally recognized ratably over time to match the continued delivery of the performance obligation to the client over the life of the contract. Sweep Program Fees The Company earns fees generated in lieu of interest income from a multi-bank sweep program with unaffiliated banks and money market funds. Pursuant to contractual arrangements with clients and their introducing-brokers, available cash balances in client accounts are swept into either Federal Deposit Insurance Corporation (“FDIC”) insured cash accounts at unaffiliated banks or unaffiliated money market funds for which the Company earns a portion of the interest income generated by the client balances for administration and recordkeeping. The fees generated by the Company’s multi-bank sweep program are reported net of the balances remitted to the introducing-brokers and the clients of introducing-brokers. These fees are paid and recognized over time to match the continued delivery of the administration and recordkeeping performance obligations to the life of the contract. The fees earned under this program are generally based upon the type of sweep account, prevailing interest rates, and the amount of client balances invested. Client Accounts Fees Client accounts fees represent fees earned for custodial, recordkeeping, and administrative functions performed for the securities clearing accounts of clients. These include statement delivery fees, account transfer fees, safekeeping fees, errors and omission insurance fees, platform fees, and other fees. Client account fees that are transactional based, such as account transfer fees, are recognized at a point in time when the related performance obligation is satisfied. Client account fees that are related to ongoing services, such as statement delivery fees and errors and omission insurance fees, are recognized over time. Client account fees that relate to ongoing services are typically billed to clients’ accounts on a monthly or quarterly basis. Physical Precious Metals Trading The Company principally generates revenue from trading physical precious metals on an OTC basis. Revenues from the sale of physical precious metals are recorded on a trade date basis and generally settle on an unallocated basis. Substantially all of the Company’s sales of precious metals are conducted using sales contracts that meet the definition of derivative instruments in accordance with ASC 815, Derivatives and Hedging (“Topic 815”). The contracts underlying the Company’s commitment to deliver precious metals are referred to as fixed price forward commodity contracts because the price of the commodity is fixed at the time the order is placed. Although the contracts typically are executed on a spot basis and settle on unallocated account, the client has the option to request delivery of the precious metals, the option to net settle out of the position by executing an offsetting trade, or the option to roll the transaction to a subsequent maturity date. Thus, the sales contracts contain embedded option derivatives that would be subject to the guidance in Topic 815. As the contracts are subject to the guidance in Topic 815, the fixed price derivative sales contracts are outside the scope of Topic 606. The Company recognizes revenue when control of the inventory is transferred within the meaning of Topic 606. Physical precious metals trading revenue generated by registered broker-dealer subsidiaries are presented on a net basis and included as a component of ‘Principal gains, net’ in the consolidated income statements, in accordance with U.S GAAP accounting requirements for broker-dealers. Physical precious metals trading revenue for subsidiaries that are not broker-dealers continue to be recorded on a gross basis. Physical Agricultural and Energy Product Trading The Company principally generates revenue from merchandising and originating physical agricultural and energy commodities from forward firm sales commitments accounted in accordance with Topic 815. The fixed and provisionally-priced derivative sales contracts that result in physical delivery are outside the scope of Topic 606. The Company recognizes revenue when control of the inventory is transferred within the meaning of Topic 606. Principal Gains, Net Principal gains, net includes revenues on financial transactions or contracts for which the Company acts as principal that is reported on a net basis and is primarily outside the scope of ASC 606. Principal gains, net includes margins generated from OTC derivative trades, equities, fixed income, precious metals, and foreign exchange executed with clients and other counterparties and are recognized on a trade-date basis. Principal gains, net, also includes realized and unrealized gains and losses derived principally from market making activities in OTC derivatives, equities, fixed income, and foreign exchange. Net dealer inventory and investment gains are recognized on a trade-date basis and include realized gains or losses and changes in unrealized gains or losses on investments at fair value. Principal gains, net also includes dividend income on long equity positions and dividend expense on short equity positions, which are recognized on the ex-dividend date. Interest Income Interest income is generated from client funds deposited with the Company to satisfy margin requirements which is held by third-party banks or on deposit with or pledged to exchange-clearing organizations or other FCMs. Interest income is also generated from the investment of client funds in allowable securities, primarily U.S. Treasury obligations. Interest income is also generated from trading fixed income securities that the Company holds in its market-making businesses. Interest income also includes interest generated from collateralized transactions, including securities borrowed and securities purchased under agreements to resell, and from extending margin loans to clients. Interest income is recognized on an accrual basis and is not within the scope of Topic 606. Remaining Performance Obligations Remaining performance obligations are services that the firm has committed to perform in the future in connection with its contracts with clients. The Company’s remaining performance obligations are generally related to its risk management consulting and asset management contracts with clients. Revenues associated with remaining performance obligations related to these contracts with clients are not material to the overall consolidated results of the Company. Similar to above, risk management consulting contracts are generally for a minimum term of six months and then continue from month to month, but may be terminated at any time after the original six months by either party upon providing written notice. Asset management contracts may be terminated by the client at any time. For the Company’s asset management activities, where fees are calculated based on a percentage of the market value of eligible assets in client’s accounts, future revenue associated with remaining performance obligations cannot be determined as such fees are subject to fluctuations in the market value of eligible assets in clients’ accounts. Practical Expedients The Company has applied Topic 606’s practical expedient that permits for the non-disclosure of the value of performance obligations for (i) contracts with an original expected length or one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which is has the right to invoice for services performed.

Earnings per Share

Earnings per Share	12 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings per Share	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 net income per share computations for the periods presented below. Year Ended September 30, (in millions, except share amounts) 2020 2019 2018 Numerator: Net income $ 169.6 $ 85.1 $ 55.5 Less: Allocation to participating securities (4.0) (1.5) (0.9) Net income allocated to common stockholders $ 165.6 $ 83.6 $ 54.6 Denominator: Weighted average number of: Common shares outstanding 18,824,328 18,738,905 18,549,011 Dilutive potential common shares outstanding: Share-based awards 356,151 275,490 385,819 Diluted shares outstanding 19,180,479 19,014,395 18,934,830 The dilutive effect of share-based awards is reflected in diluted net income per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense. Options to purchase 898,420, 907,089 and 92,627 shares of common stock for fiscal years ended September 30, 2020, 2019, and 2018, respectively, were excluded from the calculation of diluted earnings per share because they would have been anti-dilutive.

Assets and Liabilities, at Fair

Assets and Liabilities, at Fair Value	12 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Assets and Liabilities, at Fair Value	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 inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Level 3 comprises financial assets and liabilities whose fair value is estimated based on internally developed models or methodologies utilizing significant inputs that are not readily observable from objective sources. Level 3 includes contingent liabilities that have been valued using an income approach based upon management developed discounted cash flow projections, which are an unobservable input. The Company had $1.5 million and $1.8 million of contingent liabilities classified within Level 3 of the fair value hierarchy as of September 30, 2020 and September 30, 2019 , respectively. The Company had no Level 3 assets as of September 30, 2020 and September 30, 2019. Financial and nonfinancial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). A market is active if there are sufficient transactions on an ongoing basis to provide current pricing information for the asset or liability, pricing information is released publicly, and price quotations do not vary substantially either over time or among market makers. Observable inputs reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the reporting entity. The guidance requires the Company to consider counterparty credit risk of all parties of outstanding derivative instruments that would be considered by a market participant in the transfer or settlement of such contracts (exit price). The Company’s exposure to credit risk on derivative financial instruments relates to the portfolio of OTC derivative contracts as all exchange-traded contracts held can be settled on an active market with a credit guarantee from the respective exchange. The Company requires each counterparty to deposit margin collateral for all OTC instruments and is also required to deposit margin collateral with counterparties. The Company has assessed the nature of these deposits and used its discretion to adjust each based on the underlying credit considerations for the counterparty and determined that the collateral deposits minimize the exposure to counterparty credit risk in the evaluation of the fair value of OTC instruments as determined by a market participant. Fair value of financial and nonfinancial assets and liabilities that are carried on the Consolidated Balance Sheets at fair value on a recurring basis Cash and cash equivalents reported at fair value on a recurring basis includes certificates of deposit and money market mutual funds, which are stated at cost plus accrued interest, which approximates fair value. Cash, securities and other assets segregated under federal and other regulations reported at fair value on a recurring basis include the value of pledged investments, primarily U.S. Treasury obligations and commodities warehouse receipts. Deposits with and receivables from broker-dealers, clearing organizations and counterparties and payable to clients and broker-dealers, clearing organizations and counterparties includes the fair value of pledged investments, primarily U.S. Treasury obligations and foreign government obligations. These balances also include the fair value of exchange-traded options on futures and OTC forwards, swaps, and options. Financial instruments owned and sold, not yet purchased include the fair value of equity securities, which includes common, preferred, and foreign ordinary shares, American Depository Receipts (“ADRs”), Global Depository Receipts (“GDRs”), and exchange-traded funds (“ETFs”), corporate and municipal bonds, U.S. Treasury obligations, U.S. government agency obligations, foreign government obligations, agency mortgage-backed obligations, asset-backed obligations, derivative financial instruments, commodities warehouse receipts, exchange firm common stock, and investments in managed funds. The fair value of exchange firm common stock is determined by quoted market prices. Cash equivalents, debt and equity securities, commodities warehouse receipts, physical commodities inventory, derivative financial instruments and contingent liabilities are carried at fair value, on a recurring basis, and are classified and disclosed into three levels in the fair value hierarchy. The following section describes the valuation methodologies used by the Company to measure classes of financial instruments at fair value and specifies the level within the fair value hierarchy where various financial instruments are classified. The Company uses quoted prices in active markets, where available, and classifies such instruments within Level 1 of the fair value hierarchy. Examples include U.S. Treasury obligations, foreign government obligations, commodities warehouse receipts, certain equity securities traded in active markets, physical precious metals inventory held by a regulated broker-dealer subsidiary, exchange firm common stock, investments in managed funds, as well as options on futures contracts traded on national exchanges. The fair value of exchange firm common stock is determined by recent sale transactions and is included within Level 1. When instruments are traded in secondary markets and observable prices are not available for substantially the full term, the Company generally relies on internal valuation techniques or prices obtained from third-party pricing services or brokers or a combination thereof, and accordingly, classified these instruments as Level 2. Examples include corporate and municipal bonds, U.S. government agency obligations, agency-mortgage backed obligations, asset-backed obligations, certain equity securities traded in less active markets, and OTC derivative contracts, which include purchase and sale commitments related to the Company’s agricultural and energy commodities. Certain derivatives without a quoted price in an active market and derivatives executed OTC are valued using internal valuation techniques, including pricing models which utilize significant inputs observable to market participants. The valuation techniques and inputs depend on the type of derivative and the nature of the underlying instrument. The key inputs depend upon the type of derivative and the nature of the underlying instrument and include interest yield curves, foreign exchange rates, commodity prices, volatilities and correlation. These derivative instruments are included within Level 2 of the fair value hierarchy. Physical commodities inventory includes precious metals that are a part of the trading activities of a regulated broker-dealer subsidiary and is recorded at fair value using exchange-quoted prices. Physical commodities inventory also includes agricultural commodities that are a part of the trading activities of a non-broker dealer subsidiary and are recorded at net realizable value using exchange-quoted prices. The fair value of precious metals physical commodities inventory is based upon unadjusted exchange-quoted prices and is, therefore, classified within Level 1 of the fair value hierarchy. The fair value of agricultural physical commodities inventory and the related OTC firm sale and purchase commitments are generally based upon exchange-quoted prices, adjusted for basis or differences in local markets, broker or dealer quotations or market transactions in either listed or OTC markets. Exchange-quoted prices are adjusted for location and quality because the exchange-quoted prices for agricultural and energy related products represent contracts that have standardized terms for commodity, quantity, future delivery period, delivery location, and commodity quality or grade. The basis or local market adjustments are observable inputs or have an insignificant impact on the measurement of fair value and, therefore, the agricultural physical commodities inventory as well as the related OTC forward firm sale and purchase commitments have been included within Level 2 of the fair value hierarchy. With the exception of certain derivative instruments where the valuation approach is disclosed above, financial instruments owned and sold are primarily valued using third-party pricing sources. Third-party pricing vendors compile prices from various sources and often apply matrix pricing for similar securities when market-observable transactions for the instruments are not observable for substantially the full term. The Company reviews the pricing methodologies used by third-party pricing vendors in order to evaluate the fair value hierarchy classification of vendor-priced financial instruments and the accuracy of vendor pricing, which typically involves the comparison of primary vendor prices to internal trader prices or secondary vendor prices. When evaluating the propriety of vendor-priced financial instruments using secondary prices, considerations include the range and quality of vendor prices, level of observable transactions for identical and similar instruments, and judgments based upon knowledge of a particular market and asset class. If a primary vendor price does not represent fair value, justification for using a secondary price, including source data used to make the determination, is subject to review and approval by authorized personnel prior to using a secondary price. Financial instruments owned and sold that are valued using third-party pricing vendors are included within either Level 1 or Level 2 of the fair value hierarchy based upon the observability of the inputs used and the level of activity in the market. The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2020 and September 30, 2019 by level in the fair value hierarchy. Except as disclosed in Note 8, there were no assets or liabilities that were measured at fair value on a nonrecurring basis as of September 30, 2020 and September 30, 2019. September 30, 2020 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 3.2 $ — $ — $ — $ 3.2 Money market mutual funds 12.8 — — — 12.8 Cash and cash equivalents 16.0 — — — 16.0 Commodities warehouse receipts 2.4 — — — 2.4 U.S. Treasury obligations 0.2 — — — 0.2 Securities and other assets segregated under federal and other regulations 2.6 — — — 2.6 U.S. Treasury obligations 1,941.3 — — — 1,941.3 To be announced ("TBA") and forward settling securities — 31.0 — (11.8) 19.2 Foreign government obligations 8.0 — — — 8.0 Derivatives 1,949.0 395.8 — (2,537.5) (192.7) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,898.3 426.8 — (2,549.3) 1,775.8 Receivables from clients, net - Derivatives — 235.6 — (234.1) 1.5 Equity securities 254.9 9.4 — — 264.3 Corporate and municipal bonds — 66.9 — — 66.9 U.S. Treasury obligations 419.9 — — — 419.9 U.S. government agency obligations — 293.4 — — 293.4 Foreign government obligations 2.5 — — — 2.5 Agency mortgage-backed obligations — 1,384.6 — — 1,384.6 Asset-backed obligations — 33.0 — — 33.0 Derivatives 0.7 652.3 — (535.6) 117.4 Commodities leases — 24.9 — — 24.9 Commodities warehouse receipts 103.2 — — — 103.2 Exchange firm common stock 10.1 — — — 10.1 Mutual funds and other 7.5 — — — 7.5 Financial instruments owned 798.8 2,464.5 — (535.6) 2,727.7 Physical commodities inventory 26.8 188.9 — — 215.7 Total assets at fair value $ 4,742.5 $ 3,315.8 $ — $ (3,319.0) $ 4,739.3 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.5 $ — $ 1.5 Payables to clients - Derivatives 2,000.8 176.4 — (2,399.9) (222.7) TBA and forward settling securities — 22.0 — (11.8) 10.2 Derivatives — 306.7 — (302.2) 4.5 Payable to broker-dealers, clearing organizations and counterparties — 328.7 — (314.0) 14.7 Equity securities 218.0 14.9 — — 232.9 Corporate and municipal bonds — 22.5 — — 22.5 U.S. Treasury obligations 247.5 — — — 247.5 U.S. government agency obligations — 0.1 — — 0.1 Agency mortgage-backed obligations — 5.1 — — 5.1 Derivatives 563.6 — (386.8) 176.8 Commodities leases — 1.1 — — 1.1 Financial instruments sold, not yet purchased 465.5 607.3 — (386.8) 686.0 Total liabilities at fair value $ 2,466.3 $ 1,112.4 $ 1.5 $ (3,100.7) $ 479.5 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level. September 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 4.9 $ — $ — $ — $ 4.9 Money market mutual funds 8.9 — — — 8.9 Cash and cash equivalents 13.8 — — — 13.8 Commodities warehouse receipts 6.2 — — — 6.2 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 306.0 — — — 306.0 U.S. Treasury obligations 593.9 — — — 593.9 TBA and forward settling securities — 9.8 — (1.5) 8.3 Foreign government obligations 9.9 — — — 9.9 Derivatives 3,131.2 43.2 — (3,159.6) 14.8 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,735.0 53.0 — (3,161.1) 626.9 Equity securities 159.5 9.0 — — 168.5 Corporate and municipal bonds — 80.0 — — 80.0 U.S. Treasury obligations 248.7 — — — 248.7 U.S. government agency obligations — 447.1 — — 447.1 Foreign government obligations 0.5 — — — 0.5 Agency mortgage-backed obligations — 1,045.0 — — 1,045.0 Asset-backed obligations — 29.1 — — 29.1 Derivatives 1.0 486.3 — (420.8) 66.5 Commodities leases — 28.6 — — 28.6 Commodities warehouse receipts 48.4 — — — 48.4 Exchange firm common stock 12.7 — — — 12.7 Mutual funds and other 0.1 — — — 0.1 Financial instruments owned 470.9 2,125.1 — (420.8) 2,175.2 Physical commodities inventory 7.1 144.8 — — 151.9 Total assets at fair value $ 4,532.8 $ 2,322.9 $ — $ (3,581.9) $ 3,273.8 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.8 $ — $ 1.8 TBA and forward settling securities — 6.8 — (1.5) 5.3 Derivatives 3,079.1 38.3 — (3,117.1) 0.3 Payable to broker-dealers, clearing organizations and counterparties 3,079.1 45.1 — (3,118.6) 5.6 Equity securities 147.3 10.8 — — 158.1 Corporate and municipal bonds — 39.2 — — 39.2 U.S. Treasury obligations 272.3 — — — 272.3 U.S. government agency obligations — 43.8 — — 43.8 Agency mortgage-backed obligations — 29.6 — — 29.6 Derivatives — 480.3 — (422.2) 58.1 Commodities leases — 113.7 — — 113.7 Financial instruments sold, not yet purchased 419.6 717.4 — (422.2) 714.8 Total liabilities at fair value $ 3,498.7 $ 762.5 $ 1.8 $ (3,540.8) $ 722.2 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level. Realized and unrealized gains and losses are included in ‘principal gains, net’, ‘interest income’, and ‘cost of sales of physical commodities’ in the consolidated income statements. Information on Level 3 Financial Liabilities The acquisition of Fillmore Advisors, LLC, as further discussed in Note 21, included a contingent consideration arrangement as a component of the purchase price. Pursuant to the contingent consideration agreement, the Company is required to make additional future cash payments based on certain financial performance measures of the acquired business. As of September 30, 2020 and 2019, the Company has classified its liability for the contingent consideration within Level 3 of the fair value hierarchy because the fair value was determined using significant unobservable inputs, which included projected cash flows. During the year ended September 30, 2020, the Company recorded cash settlements against the liability of $0.9 million, partially offset by remeasurement losses of $0.6 million, which are included in ‘Other’ expenses on the consolidated income statement for the year ended September 30, 2020. The fair value of an exchange-traded options on futures contract is equal to the unrealized gain or loss on the contract determined by marking the contract to the current settlement price for a like contract on the valuation date of the contract. A settlement price may not be used if the market makes a limit move with respect to a particular options on futures contract or if the contract’s underlying experiences significant price fluctuations after the determination of the settlement price. When a settlement price cannot be used, options on futures contracts will be valued at their fair value as determined in good faith pursuant to procedures adopted by management of the Company. The Company has classified equity investments in exchange firms’ common stock not pledged for clearing purposes as trading securities. The investments are recorded at fair value, with unrealized gains and losses recorded, net of taxes, included in earnings. As of September 30, 2020, the cost and fair value of the equity investments in exchange firms is $3.7 million and $10.1 million, respectively. As of September 30, 2019, the cost and fair value of the equity investments in exchange firms was $3.7 million and $12.7 million, respectively. Additional Disclosures about the Fair Value of Financial Instruments that are not carried on the Consolidated Balance Sheets at Fair Value Many, but not all, of the financial instruments that the Company holds are recorded at fair value in the Consolidated Balance Sheets. The following represents financial instruments in which the ending balance at September 30, 2020 and 2019 was not carried at fair value in accordance with U.S. GAAP on our Consolidated Balance Sheets: Short-term financial instruments: The carrying value of short-term financial instruments, including cash and cash equivalents, cash segregated under federal and other regulations, securities purchased under agreements to re-sell and securities sold under agreements to re-purchase, and securities borrowed and loaned are recorded at amounts that approximate the fair value of these instruments due to their short-term nature and level of collateralization. These financial instruments generally expose us to limited credit risk and have no stated maturities or have short-term maturities and carry interest rates that approximate market rates. Under the fair value hierarchy, cash and cash equivalents and cash segregated under federal and other regulations are classified as Level 1. Securities purchased under agreements to re-sell and securities sold under agreements to re-purchase, and securities borrowed and loaned are classified as Level 2 under the fair value hierarchy as they are generally overnight, or short-term in nature, and are collateralized by common stock, U.S. Treasury obligations, U.S. government agency obligations, agency mortgage-backed obligations, and asset-backed obligations. Receivables and other assets: R eceivables from broker-dealers, clearing organizations, and counterparties, receivables from clients, net, notes receivables, net and certain other assets are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Payables: P ayables to clients and payables to brokers-dealers, clearing organizations, and counterparties are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Lender under loans : Payables to lenders under loans carry variable rates of interest and thus approximate fair value and are classified as Level 2 under the fair value hierarchy. Senior secured borrowings, net : Senior secured borrowings, net includes a senior secured term loan with a carrying value of $179.5 million as of September 30, 2020, which carries a variable rate of interest and thus approximates fair value and is classified as Level 2 under the fair value hierarchy. Senior secured borrowings, net also includes the Company's 8.625% Senior Secured Notes due 2025 (the “Senior Secured Notes”) and Gain’s 5.00% Senior Notes due 2022 (the “Gain Notes”) as further described in Note 12 with a carrying value of $336.0 million as of September 30, 2020. The carrying value of the Senior Secured Notes and Gain Notes represent their principal amounts net of unamortized deferred financing costs and original issue discount. As of September 30, 2020, the Senior Secured Notes and Gain Notes had a fair value of $379.4 million and are classified as Level 2 under the fair value hierarchy

Financial Instruments with Off-

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk	12 Months Ended
	Sep. 30, 2020
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk	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 consolidated financial statements as of September 30, 2020 at the fair values of the related financial instruments. The Company will incur losses if the fair value of the underlying financial instruments increases subsequent to September 30, 2020. The total of $686.0 million as of September 30, 2020 includes $176.8 million for derivative contracts, which represent a liability to the Company based on their fair values as of September 30, 2020. Derivatives The Company utilizes derivative products in its trading capacity as a dealer in order to satisfy client needs and mitigate risk. The Company manages risks from both derivatives and non-derivative cash instruments on a consolidated basis. The risks of derivatives should not be viewed in isolation, but in aggregate with the Company’s other trading activities. The Company’s derivative positions are included in the consolidating balance sheets in ‘deposits with and receivables from broker-dealers, clearing organizations, and counterparties’, ‘receivables from clients, net’, ‘financial instruments owned and sold, not yet purchased, at fair value’, ‘payables to clients’ and ‘payables to broker-dealers, clearing organizations and counterparties’. Listed below are the fair values of the Company’s derivative assets and liabilities as of September 30, 2020 and September 30, 2019. Assets represent net unrealized gains and liabilities represent net unrealized losses. September 30, 2020 September 30, 2019 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,637.2 $ 1,747.3 $ 1,437.1 $ 1,463.4 OTC commodity derivatives 553.9 433.2 84.2 106.2 Exchange-traded foreign exchange derivatives 9.3 13.0 36.9 33.5 OTC foreign exchange derivatives 520.8 461.5 403.2 368.8 Exchange-traded interest rate derivatives 271.1 200.7 900.1 882.0 OTC interest rate derivatives 96.0 96.6 42.1 43.6 Exchange-traded equity index derivatives 32.1 39.8 758.1 700.2 OTC equity and indices derivatives 113.0 55.4 — — TBA and forward settling securities 31.0 22.0 9.8 6.8 Gross fair value of derivative contracts 3,264.4 3264400000 3,069.5 3,671.5 3,604.5 Impact of netting and collateral $ (3,319.0) $ (3,100.7) $ (3,581.9) $ (3,540.8) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties,net' $ (173.5) $ 23.1 Total fair value included in 'Receivables from clients, net' $1.5 $ — Total fair value included in 'Financial instruments owned, at fair value $117.4 66.5 Total fair value included in 'Payables to clients' $ (222.7) $ — Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties $ 14.7 $ 5.6 Total fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 176.8 $ 58.1 (1) As of September 30, 2020 and September 30, 2019, the Company’s derivative contract volume for open positions was approximately 7.9 million and 10.6 million contracts, respectively. The Company’s derivative contracts are principally held in its Commercial and Retail segments. The Company assists its Commercial 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 segment clients with option products, including combinations of buying and selling puts and calls. In its Retail segment, the Company provides its retail clients with access to spot foreign exchange, precious metals trading, as well as contracts for a difference (“CFDs”) and spread bets, where permitted. The Company mitigates its risk by generally offsetting the client’s transaction simultaneously with one of the Company’s trading counterparties or will offset that transaction with a similar but not identical position on the exchange. The risk mitigation of these offsetting trades is not within the documented hedging designation requirements of the Derivatives and Hedging Topic of the ASC. These derivative contracts are traded along with cash transactions because of the integrated nature of the markets for these products. The Company manages the risks associated with derivatives on an aggregate basis along with the risks associated with its proprietary trading and market-making activities in cash instruments as part of its firm-wide risk management policies. In particular, the risks related to derivative positions may be partially offset by inventory, unrealized gains in inventory or cash collateral paid or received. The Company transacts in derivative instruments, which consist of futures, mortgage-backed TBA securities and forward settling transactions, that are used to manage risk exposures in the Company’s fixed income portfolio. The fair value of these transactions is recorded in deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties. Realized and unrealized gains and losses on securities and derivative transactions are reflected in ‘principal gains, net’. The Company enters into TBA securities transactions for the sole purpose of managing risk associated with the purchase of mortgage pass-through securities. As of September 30, 2020 and September 30, 2019, TBA and forward settling securities recorded within deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties are summarized as follows (in millions): September 30, 2020 September 30, 2019 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 $ 10.8 $ 5,389.3 $ 3.7 $ 1,778.4 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (1.7) $ 2,647.7 $ (0.6) $ 234.5 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ 2.8 $ (2,978.7) $ 0.9 $ (451.6) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (13.0) $ (6,549.4) $ (5.9) $ (2,788.0) Unrealized loss on forward settling securities purchased within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ (0.3) $ 1,243.5 Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ 17.4 $ (1,946.0) $ 5.2 $ (581.2) Unrealized loss on forward settling securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (7.3) $ 2,447.1 $ — $ — The notional amounts of these instruments reflect the extent of the Company’s involvement in TBA and forward settling securities and do not represent counterparty exposure. The following table sets forth the Company’s net gains (losses) related to derivative financial instruments for the fiscal years ended September 30, 2020, 2019, and 2018, in accordance with the Derivatives and Hedging Topic of the ASC. The net gains (losses) set forth below are included in ‘principal gains, net’ and ‘cost of sales of physical commodities’ in the consolidated income statements. Year Ended September 30, (in millions) 2020 2019 2018 Commodities $ 197.3 $ 100.8 $ 94.0 Foreign exchange 38.2 8.1 9.2 Interest rate, equities, and indices 20.4 (2.6) 1.0 TBA and forward settling securities (49.7) (35.3) 14.5 Net gains from derivative contracts $ 206.2 $ 71.0 $ 118.7 Credit Risk In the normal course of business, the Company purchases and sells financial instruments, commodities and foreign currencies as either principal or agent on behalf of its clients. If either the client or counterparty fails to perform, the Company may be required to discharge the obligations of the nonperforming party. In such circumstances, the Company may sustain a loss if the fair value of the financial instrument or foreign currency is different from the contract value of the transaction. The majority of the Company’s transactions and, consequently, the concentration of its credit exposure are with commodity exchanges, clients, broker-dealers and other financial institutions. These activities primarily involve collateralized and uncollateralized arrangements and may result in credit exposure in the event that a counterparty fails to meet its contractual obligations. The Company’s exposure to credit risk can be directly impacted by volatile financial markets, which may impair the ability of counterparties to satisfy their contractual obligations. The Company seeks to control its credit risk through a variety of reporting and control procedures, including establishing credit limits based upon a review of the counterparties’ financial condition and credit ratings. The Company monitors collateral levels on a daily basis for compliance with regulatory and internal guidelines and requests changes in collateral levels as appropriate. The Company is a party to financial instruments in the normal course of its business through client and proprietary trading accounts in exchange-traded and OTC derivative instruments. These instruments are primarily the execution of orders for commodity futures, options on futures and forward foreign currency contracts on behalf of its clients, substantially all of which are transacted on a margin basis. Such transactions may expose the Company to significant credit risk in the event margin requirements are not sufficient to fully cover losses which clients may incur. The Company controls the risks associated with these transactions by requiring clients to maintain margin deposits in compliance with individual exchange regulations and internal guidelines. The Company monitors required margin levels daily and, therefore, may require clients to deposit additional collateral or reduce positions when necessary. The Company also establishes credit limits for clients, which are monitored daily. The Company evaluates each client’s creditworthiness on a case by case basis. Clearing, financing, and settlement activities may require the Company to maintain funds with or pledge securities as collateral with other financial institutions. Generally, these exposures to both clients and counterparties are subject to master netting, or client agreements, which reduce the exposure to the Company by permitting receivables and payables with such clients to be offset in the event of a client default. Management believes that the margin deposits held as of September 30, 2020 and September 30, 2019 were adequate to minimize the risk of material loss that could be created by positions held at that time. Additionally, the Company monitors collateral fair value on a daily basis and adjusts collateral levels in the event of excess market exposure. Derivative financial instruments involve varying degrees of off-balance sheet market risk whereby changes in the fair values of underlying financial instruments may result in changes in the fair value of the financial instruments in excess of the amounts reflected in the consolidated balance sheets. Exposure to market risk is influenced by a number of factors, including the relationships between the financial instruments and the Company’s positions, as well as the volatility and liquidity in the markets in which the financial instruments are traded. The principal risk components of financial instruments include, among other things, interest rate volatility, the duration of the underlying instruments and changes in commodity pricing and foreign exchange rates. The Company attempts to manage its exposure to market risk through various techniques. Aggregate market limits have been established and market risk measures are routinely monitored against these limits.

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts	12 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net, receivables from clients, net, and notes receivable, net include an allowance for doubtful accounts, which reflects the Company’s best estimate of probable losses inherent in the accounts. The Company provides for an allowance for doubtful accounts based on a specific-identification basis. The Company continually reviews its allowance for doubtful accounts. The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $1.3 million and $36.9 million as of September 30, 2020 and September 30, 2019, respectively. During the year ended September 30, 2020, the Company charged off $35.6 million of receivables against the allowance for doubtful accounts related to the physical coal business, which the Company exited in fiscal 2018. The allowance for doubtful accounts related to receivables from clients was $25.8 million and $11.7 million as of September 30, 2020 and September 30, 2019, respectively. The Company had no allowance for doubtful accounts related to notes receivable as of September 30, 2020 and September 30, 2019. During the year ended September 30, 2020, the Company recorded bad debt expense of $13.0 million. The bad debt expense during fiscal 2020 primarily related to $3.5 million of client OTC derivative account deficits in the Commercial segment, $5.4 million of client exchange-traded futures and options on futures account deficits in the Institutional segment, and $0.6 million of OTC derivative client account deficits in the Retail segment. The Company also incurred bad debt expense of $3.2 million within the Commercial segment related to receivables in the Company’s physical energy commodity business. During the year ended September 30, 2019, the Company recorded bad debt expense, net of recoveries, of $2.5 million, including a net increase in provision for bad debts of $2.6 million, direct write-offs of $0.3 million, and direct recoveries of $0.4 million. The increase in provision for bad debts during fiscal 2019 primarily related to $2.7 million of client OTC derivative account deficits in the Commercial segment, and $1.4 million in the Institutional segment, partially offset by client recoveries in the Commercial segment. Additionally, during the year ended September 30, 2019, the Company recorded recoveries on the bad debt on physical coal of $12.4 million, reducing the allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties. See additional information in Note 19. During the year ended September 30, 2018, the Company recorded bad debt expense, net of recoveries, of $3.1 million, including a net increase in provision for bad debts of $2.9 million, direct write-offs of $0.3 million, and recoveries of $0.1 million. The increase in provision for bad debts during fiscal 2018 primarily related to $2.8 million of agricultural OTC derivative client accounts deficits in the Commercial segment and $0.4 million of client exchange-traded futures and options on futures account deficits in the Institutional segment, partially offset by a provision decrease in the physical agricultural and energy business of the Commercial segment. Additionally, during the year ended September 30, 2018, the Company recorded charges to earnings of $1.0 million, to record an additional allowance for doubtful accounts related to a bad debt incurred in the physical coal business. See additional information in Note 19. Activity in the allowance for doubtful accounts for the fiscal years ended September 30, 2020, 2019, and 2018 was as follows: (in millions) 2020 2019 2018 Balance, beginning of year $ 48.6 $ 58.2 $ 54.6 Provision (recovery) for bad debts 13.0 (9.8) 3.9 Allowance charge-offs (35.6) (1.3) (0.3) Other (1) 1.1 1.5 — Balance, end of year $ 27.1 $ 48.6 $ 58.2 (1) Allowance increase is related to a recoverable amount due from an affiliated party and recorded in ‘other assets’ on the consolidated balance sheets.

Physical Commodities Inventory

Physical Commodities Inventory	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Physical Commodities Inventory	Physical Commodities Inventory The Company’s inventories consist of finished physical commodities as shown below. (in millions) September 30, September 30, 2019 Physical Ag & Energy (1) $ 201.5 $ 144.8 Precious metals - held by broker-dealer subsidiary (2) 14.2 7.1 Precious metals - held by non-broker-dealer subsidiaries (3) 65.4 77.4 Physical commodities inventory $ 281.1 $ 229.3 (1) Physical Ag & Energy consists of agricultural commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, cocoa, cotton, and others. The agricultural commodity inventories are carried at net realizable value, which approximates selling prices in the ordinary course of business, less disposal costs, with changes in net realizable value included as a component of ‘cost of sales of physical commodities’ on the consolidated income statements. The agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. Physical Ag & Energy also consists of energy related inventories, including primarily propane, gasoline, and kerosene, which are valued at the lower of cost or net realizable value. (2) Precious metals held by the Company’s subsidiary, StoneX Financial Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ on the consolidated income statements, in accordance with U.S. GAAP accounting requirements for broker-dealers. (3) Precious metals inventory held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value. The Company has recorded lower of cost or net realizable value adjustments for certain precious metals inventory of $0.7 million and $0.5 million as of September 30, 2020 and 2019, respectively. The adjustments are included in ‘cost of sales of physical commodities’ in the consolidated income statements.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment, Net [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment are stated at cost, and reported net of accumulated depreciation on the consolidated balance sheets. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful lives of the assets. The estimated useful lives of property and equipment range from 3 to 10 years. During the fiscal years ended September 30, 2020, 2019, and 2018, depreciation expense was $13.3 million, $11.2 million, and $9.4 million, respectively. A summary of property and equipment, at cost less accumulated depreciation as of September 30, 2020 and 2019 is as follows: (in millions) September 30, 2020 September 30, 2019 Property and equipment: Furniture and fixtures $ 10.2 $ 10.6 Software 28.6 33.9 Equipment 30.8 28.1 Leasehold improvements 38.3 20.3 Total property and equipment 107.9 92.9 Less accumulated depreciation (45.8) (49.0) Property and equipment, net $ 62.1 $ 43.9

Goodwill

Goodwill	12 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill allocated to the Company’s operating segments as of September 30, 2020 and 2019 is as follows: (in millions) September 30, September 30, 2019 Commercial $ 32.7 $ 32.7 Institutional 9.8 8.7 Retail 2.2 2.2 Global Payments 10.0 7.6 Total Goodwill 54.7 51.2 The Company recorded $0.1 million and zero in foreign exchange revaluation adjustments on goodwill for the years ended September 30, 2020 and 2019, respectively. The Company recorded additional goodwill of $2.3 million during the year ended September 30, 2020 within the Global Payments operating segment related to the initial purchase price allocation for the acquisition of GIROXX GmbH (“GIROXX”) as further discussed in Note 21. The Company recorded additional goodwill of $1.1 million during the year ended September 30, 2020 within the Institutional reportable segment related to the final purchase price allocation for the acquisition of the futures and options brokerage and clearing business of UOB Bullion and Futures Limited as further discussed in Note 21.

Intangible Assets

Intangible Assets	12 Months Ended
	Sep. 30, 2020
Intangible Assets [Abstract]
Intangible Assets	Intangible Assets The Company recorded $3.1 million, $1.0 million, $1.7 million, and $9.8 million of customer base intangible assets during the year ended September 30, 2020 related to the acquisitions of UOB Bullion and Futures Limited, IFCM Commodities GmbH, Quest Capital, and Gain, respectively, as further discussed in Note 21. The Company recorded $22.2 million and $1.5 million of software program/platform intangible assets during the year ended September 30, 2020 related to the acquisitions of Gain and GIROXX, respectively, as further discussed in Note 21. The Company recorded $3.7 million of trade/domain name intangible assets during the year ended September 30, 2020 related to the acquisition of Gain as further discussed in Note 21. The Company recorded $0.4 million of indefinite lived business license intangible assets during the year ended September 30, 2020 related to the acquisition of GIROXX as further discussed in Note 21. The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows (in millions): September 30, 2020 September 30, 2019 Gross Amount Accumulated Net Amount Gross Amount Accumulated Net Amount Intangible assets subject to amortization: Trade/domain names $ 3.7 $ (0.2) $ 3.5 $ — $ — $ — Software programs/platforms 29.0 (4.9) 24.1 5.3 (3.0) 2.3 Customer base 38.2 (16.3) 21.9 22.1 (12.5) 9.6 Total intangible assets subject to amortization 70.9 (21.4) 49.5 27.4 (15.5) 11.9 Intangible assets not subject to amortization: Website domains 2.1 — 2.1 2.1 — 2.1 Business licenses 3.2 — 3.2 2.7 — 2.7 Total intangible assets not subject to amortization: 5.3 — 5.3 4.8 — 4.8 Total intangible assets $ 76.2 $ (21.4) $ 54.8 $ 32.2 $ (15.5) $ 16.7 Amortization expense related to intangible assets was $5.8 million, $2.8 million, and $2.3 million for the years ended September 30, 2020, 2019, and 2018, respectively. As of September 30, 2020, the estimated future amortization expense was as follows: (in millions) Fiscal 2021 $ 15.1 Fiscal 2022 13.8 Fiscal 2023 12.2 Fiscal 2024 4.7 Fiscal 2025 and thereafter 3.7 $ 49.5

Credit Facilities

Credit Facilities	12 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Credit Facilities	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 $736.6 million, subject to the terms and conditions for these facilities. The amounts outstanding under these credit facilities carry variable rates of interest, thus approximating fair value. The Company’s committed credit facilities consist of the following: • A three-year first-lien senior secured syndicated loan facility under which $376.6 million is available to the Company for general working capital requirements and capital expenditures. During the year ended September 30, 2020, additional members were added to the syndication further increasing the committed amount to $393.0 million. The amended facility is comprised of a $196.5 million revolving credit facility and a $196.5 million Term Loan facility. The Company is required to make quarterly principal payments against the Term Loan equal to 1.25% of the original balance with the remaining balance due on the maturity date. During the year ended September 30, 2020, the Company made scheduled quarterly principal payments against the Term Loan equal to $9.8 million, reducing the amount outstanding to $180.1 million as of September 30, 2020. Amounts repaid on the Term Loan may not be reborrowed. The credit facility is secured by a first priority lien on substantially all of the assets of the Company and those of our subsidiaries that guarantee the credit facility. Per the terms of the amended facility, the commitment fees and interest rates are subject to decrease if the Company’s consolidated leverage ratio, as defined, decreases below certain thresholds. As of September 30, 2020, unused portions of the loan facility require a commitment fee of 0.625% on the unused commitment. Both the revolving credit facility and the Term Loan are subject to variable rates of interest. As of September 30, 2020, borrowings under the facility bear interest at the Eurodollar Rate, as defined, plus 3.00% or the Base Rate, as defined, plus 2.00%. Borrowings under the Base Rate and Eurodollars options were subject to interest rates of 5.25% and 3.10%, respectively, as of September 30, 2020. The agreement contains financial covenants related to consolidated tangible net worth, consolidated funded debt to net worth ratio, consolidated fixed charge coverage ratio and consolidated net unencumbered liquid assets, as defined. The agreement also contains a non-financial covenant related to the allowable annual consolidated capital expenditures permitted under the agreement. The Company was in compliance with all covenants under the loan facility as of September 30, 2020. • An unsecured committed line of credit under which $75.0 million is available to the Company’s wholly owned subsidiary, StoneX Financial Inc to provide short term funding of margin to commodity exchanges as necessary. This line of credit is subject to annual review, and the continued availability of this line of credit is subject to StoneX Financial Inc’s financial condition and operating results continuing to be satisfactory as set forth in the agreement. Unused portions of the margin line require a commitment fee of 0.50% on the unused commitment. Borrowings under the margin line are on a demand basis and bear interest at the Base Rate, as defined, plus 2.00%, which was 5.25% as of September 30, 2020. The agreement contains financial covenants related to StoneX Financial Inc’s tangible net worth, excess net capital and maximum net loss over a trailing twelve month period, as defined. StoneX Financial Inc was in compliance with these covenants as of September 30, 2020. The facility is guaranteed by the Company. • A syndicated committed borrowing facility under which $260.0 million is available to the Company’s wholly owned subsidiary, FCStone Merchant Services, LLC (“FCStone Merchants”) to finance commodity financing arrangements and commodity repurchase agreements. The facility is secured by the assets of FCStone Merchants, and guaranteed by the Company. Unused portions of the borrowing facility require a commitment fee of 0.35% on the unused commitment. The borrowings outstanding under the facility bear interest at a rate per annum equal to the Eurodollar Rate plus Applicable Margin, as defined, or the Base Rate plus Applicable Margin, as defined. Borrowings under the Base Rate and Eurodollar options were subject to interest rates of 3.25% and 2.4%, respectively, as of September 30, 2020. The agreement contains financial covenants related to tangible net worth, as defined. FCStone Merchants was in compliance with this covenant as of September 30, 2020. • An unsecured syndicated committed borrowing facility under which $25.0 million is available to the Company’s wholly owned subsidiary, StoneX Financial Ltd for short term funding of margin to commodity exchanges. The borrowings outstanding under the facility bear interest at a rate per annum equal to 2.50% plus LIBOR, as defined. The agreement contains financial covenants related to net tangible assets, as defined. StoneX Financial Ltd was in compliance with this covenant as of September 30, 2020. The facility is guaranteed by the Company. This facility matured on October 14, 2020 and was replaced by an unsecured syndicated committed borrowing facility with substantially similar terms. Uncommitted Credit Facilities During the year ended September 30, 2020, the Company executed a secured, uncommitted loan facility, under which StoneX Financial Ltd may borrow up to $20.0 million, collateralized by commodities warehouse receipts, to facilitate the financing of inventory of commodities, subject to certain terms and conditions of the credit agreement. There were $20.0 million in borrowings outstanding under this credit facility as of September 30, 2020. The Company has a secured, uncommitted loan facility, under which StoneX 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 at September 30, 2020 and 2019. The Company has a secured, uncommitted loan facility, under which StoneX 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 no borrowings outstanding under this credit facility as of September 30, 2020, and September 30, 2019. The Company has secured uncommitted loan facilities under which StoneX 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 September 30, 2020 and September 30, 2019. The Company had a secured, uncommitted loan facility under which FCStone Merchant Services, LLC could 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. There were $3.4 million in borrowings outstanding under this credit facility as of September 30, 2019. The credit facility was terminated during the three months ended March 31, 2020, in connection with the refinancing and extension of FCStone Merchant Services, LLC’s committed credit facility. Note Payable to Bank In April 2015, the Company obtained a $4.0 million loan from a commercial bank, secured by equipment purchased with the proceeds. The note was payable in monthly installments, with the final payment made during March 2020. The note bore interest at a rate per annum equal to LIBOR plus 2.00%. Senior Secured Notes On June 11, 2020, the Company completed the issuance and sale of $350 million in aggregate principal amount of the Company’s Notes at the offering price of 98.5% of the aggregate principal amount. The Company used the proceeds from the issuance of the Senior Secured Notes to fund the merger consideration for the consummation of the merger of the Company’s wholly-owned subsidiary with Gain as further discussed in Note 18, to pay acquisition related costs of the merger, and to fund the redemption of the Gain Notes. The Senior Secured Notes are fully and unconditionally guaranteed, jointly and severally, on a senior second lien secured basis, by certain subsidiaries of the Company that guarantee the Company’s senior committed credit facility and by Gain and certain of its domestic subsidiaries. The Notes will mature on June 15, 2025. Interest on the Senior Secured Notes accrues at a rate of 8.625% per annum and is payable semiannually in arrears on June 15 and December 15 of each year, commencing on December 15, 2020. The Company incurred debt issuance costs of $9.5 million in connection with the issuance of the Senior Secured Notes, which are being amortized over the term of the Senior Secured Notes under the effective interest method. The Company has the option to redeem all or a portion of the Senior Secured Notes at any time prior to June 15, 2022 at a price equal to 100% of the principal amount of the Senior Secured Notes redeemed plus accrued and unpaid interest to the redemption date plus a “make-whole” premium. At any time on or after June 15, 2022, the Company may redeem the Senior Secured Notes, in whole or in part, at the redemption prices set forth in the indenture. At any time before June 15, 2022, the Company may also redeem up to 40% of the aggregate principal amount of the Senior Secured Notes at a redemption price of 108.625% of the principal amount, plus accrued and unpaid interest, if any, to the date of redemption, with the proceeds of certain equity offerings. In addition, upon the earlier to occur of (x) a business combination between the Company’s subsidiaries that are registered in the UK and regulated by the Financial Conduct Authority and (y) the one year anniversary of the date of issuance of the Senior Secured Notes, the Company may elect to redeem up to $100.0 million in aggregate principal amount of the Senior Secured Notes at a redemption price equal to 103% of the principal amount of the Senior Secured Notes redeemed, plus accrued and unpaid interest, if any, to the date of redemption. If the Company elects not to redeem the Senior Secured Notes, the holders of the Senior Secured Notes will have the right to require the Company to repurchase up to $100.0 million in aggregate principal amount of the Senior Secured Notes (or a lesser amount equal to the difference between $100.0 million and the amounts previously redeemed by the Company) at a purchase price equal to 103% of the principal amount of the Senior Secured Notes repurchased, plus accrued and unpaid interest, if any, to the date of repurchase. In connection with the Gain merger, the Company assumed the Gain Notes in an aggregate principal amount of $92.0 million. The consummation of the merger with Gain constituted a fundamental change and make-whole fundamental change under the terms of the Gain Notes’ indenture. As a result, the holders of the Gain Notes were entitled to require the Company to repurchase the Gain Notes at a repurchase price equal to 100% of the principal amount, together with accrued and unpaid interest, on September 1, 2020. Alternatively, the holders of the Gain Notes could continue to hold such notes without exercising the repurchase right, in which case the Gain Notes continued to bear interest at 5.00% and the notes are convertible into the right to convert the principal amount of the Senior Secured Notes solely into cash in an amount equal to the conversion rate in effect on the conversion date multiplied by $6.00. Under the terms of the fundamental change and make-whole fundamental change, the Company redeemed $91.5 million of the aggregate principal amount of Gain Notes on September 1, 2020, with approximately $0.5 million remaining outstanding as of September 30, 2020. The Company was required to redeem the Senior Secured Notes in an amount equal to the aggregate principal amount of the Gain Notes that remained outstanding after the fundamental change repurchase date, at a redemption price equal to 100% of the principal amount of the Senior Secured Notes redeemed, plus accrued and unpaid interest, if any, to the redemption date. Financing Bridge Commitment On February 26, 2020, the Company entered into a commitment letter with Jefferies Finance LLC (“Jefferies”), pursuant to which subject to the terms and conditions set forth therein, Jefferies committed to provide a $350 million senior secured bridge loan facility to finance the merger with Gain and to pay related fees and expenses. In consideration for Jefferies commitment to provide the bridge facility, the Company paid Jefferies a non-refundable commitment fee of $4.4 million. As a result of the issuance of the Senior Secured Notes as described above, the commitment was terminated and the commitment fee was extinguished and included in ‘interest expense’ on the consolidated income statement for the year ended September 30, 2020. 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 and the Senior Secured Notes as of the periods indicated: (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment September 30, 2020 September 30, 2019 Committed Credit Facilities Term Loan (1) February 22, 2022 $ 180.1 $ 179.5 (3) $ 167.6 Revolving Line of Credit (1) February 22, 2022 196.5 23.0 70.0 Senior StoneX Group Inc. Committed Credit Facility 376.6 202.5 237.6 StoneX Financial Inc. None April 2, 2021 75.0 — — FCStone Merchants Services, LLC Certain commodities assets January 29, 2022 260.0 200.1 128.5 StoneX Financial Ltd. (4) None October 14, 2021 25.0 25.0 — $ 736.6 $ 427.6 $ 366.1 Uncommitted Credit Facilities StoneX Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a — 3.4 StoneX Financial Ltd. Commodities warehouse receipts n/a n/a 20.0 — Notes payable to bank Certain equipment — 0.4 Senior Secured Notes (2) $ 336.0 (3) $ — Total outstanding borrowings $ 783.6 $ 369.9 (1) The StoneX Group Inc. committed credit facility is secured by substantially all of the assets of StoneX Group Inc. and certain subsidiaries identified in the credit facility agreement as obligors, and pledged equity of certain subsidiaries identified in the credit facility as limited guarantors. (2) The Senior Secured Notes and the related guarantees are secured by liens on substantially all of the Company’s and the guarantors’ assets, subject to certain customary and other exceptions and permitted liens. The liens on the assets that secure the Senior Secured Notes and the related guarantees are contractually subordinated to the liens on the assets that secure the Company’s and the guarantors’ existing and future first lien secured indebtedness, including indebtedness under the Company’s senior committed credit facility. (3) Amounts outstanding under the Term Loan and the Senior Secured Notes are reported net of unamortized deferred financing costs and original issue discount of $0.5 million and $14.0 million, respectively. (4) The StoneX Financial Ltd committed credit facility facility in place at September 30, 2020 matured on October 14, 2020 and was replaced by an unsecured syndicated committed borrowing facility with substantially the similar terms. The expiration date noted above relates to the new facility which became effective October 14, 2020. As reflected above, $75.0 million of the Company’s committed credit facilities are scheduled to expire during the fiscal year ended September 30, 2021. The Company intends to renew or replace these facilities as they expire, and based on the Company’s liquidity position and capital structure, the Company believes it will be able to do so.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal and Regulatory Proceedings Certain conditions may exist as of the date the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. In assessing loss contingencies related to legal and regulatory proceedings that are pending against the Company or unasserted claims that may result in such proceedings, the Company’s legal counsel evaluates the perceived merits of any legal or regulatory proceedings or unasserted claims as well as the perceived merits of the amount of relief sought or expected to be sought therein. If the assessment of a contingency indicates that it is probable that a material loss had been incurred at the date of the financial statements and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potentially material loss contingency is not probable, but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, together with an estimate of the range of possible loss if determinable and material, would be disclosed. Neither accrual nor disclosure is required for loss contingencies that are deemed remote. The Company accrues legal fees related to contingent liabilities as they are incurred. From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the limits of the respective policy. Additionally, the Company is subject to extensive regulation and supervision by U.S. federal and international governmental agencies and various self-regulatory organizations. The Company and its advisors periodically engage with such regulatory agencies and organizations, in the context of examinations or otherwise, to respond to inquiries, informational requests, and investigations. From time to time, such engagements result in regulatory complaints or other matters, the resolution of which can include fines and other remediation. As of September 30, 2020 and 2019, the consolidated balance sheets include loss contingency accruals, recorded during and prior to these fiscal years then ended, which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, and in addition to the possible losses discussed below, is not material to the Company’s earnings, financial position or liquidity. The following is a summary of a significant legal matter involving the Company OptionSellers During the week ended November 16, 2018, balances in approximately 300 accounts of the FCM division of the Company’s wholly owned subsidiary, StoneX 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 StoneX 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 StoneX Financial Inc. acted solely as the clearing firm in its role as the FCM. StoneX Financial Inc.’s client agreements hold account holders liable for all losses in their accounts and obligate the account holders to reimburse StoneX Financial Inc. for any account deficits in their accounts. As of September 30, 2019, the aggregate receivable from these client accounts, net of collections and other allowable deductions, was $29.0 million, with no individual account receivable exceeding $1.4 million. StoneX 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. StoneX Financial Inc. has been named in arbitrations brought by clients seeking damages relating to the trading losses in these accounts. The Company believes that such cases are without merit and intend to defend them vigorously. At the same time, the Company has initiated numerous arbitration proceedings against clients to recover deficit balances in their accounts. The Company believes it has a valid claim against its clients, based on the express language of the client contracts and legal precedent, and intends to pursue collection of these claims vigorously. The Company has done an assessment of the collectability of these accounts, considered the status of arbitration proceedings, and has concluded that it does not have a sufficient basis to record an allowance against these uncollected balances. As the Company moves through the collection and arbitration processes and additional information becomes available, the Company will continue to consider the need for an allowance against the carrying value of these uncollected balances. Depending on future collections and arbitration proceedings, any provisions for bad debts and actual losses ultimately may or may not be material to the Company’s financial results. Currently, the Company does not believe that any potential losses related to this matter would impact its ability to comply with its ongoing liquidity, capital, and regulatory requirements. Contractual Commitments Purchase Commitments The Company determines an estimate of contractual purchase commitments in the ordinary course of business primarily for the purchase of precious metals and agricultural and energy commodities. Unpriced contract commitments have been estimated using September 30, 2020 fair values. The purchase commitments and other obligations as of September 30, 2020 for less than one year, one to three years, three to five years, and after five years were $5,230.9 million, $19.2 million, $17.2 million, and $3.2 million respectively. The purchase commitments for less than one year will be offset by corresponding sales commitments of $5,162.4 million. Exchange Member Guarantees The Company is a member of various exchanges that trade and clear futures and option contracts. In connection with the Sterne acquisition, the Company is also a member of and provides guarantees to securities clearinghouses and exchanges in connection with client trading activities. Associated with its memberships, the Company may be required to pay a proportionate share of the financial obligations of another member who may default on its obligations to the exchanges. While the rules governing different exchange memberships vary, in general the Company’s guarantee obligations would arise only if the exchange had previously exhausted its resources. In addition, any such guarantee obligation would be apportioned among the other non-defaulting members of the exchange. Any potential contingent liability under these arrangements is not quantifiable and could exceed the cash and securities it has posted to the clearinghouse as collateral. The Company has not recorded any contingent liability in the consolidated financial statements for these agreements and believes that any potential requirement to make payments under these agreements is remote. Self-Insurance The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. Liabilities are recognized based on claims filed and an estimate of claims incurred but not reported. The Company has purchased stop-loss coverage to limit its exposure on a per claim basis and in aggregate in the event that aggregated actual claims would exceed 120% of actuarially estimated claims. The Company is insured for covered costs in excess of these limits. Although the ultimate outcome of these matters may exceed the amounts recorded and additional losses may be incurred, the Company does not believe that any additional potential exposure for such liabilities will have a material adverse effect on the Company’s consolidated financial position or results of operations. As of September 30, 2020 and September 30, 2019, the Company had $1.1 million and $0.8 million, respectively, accrued for self-insured medical and dental claims included in ‘accounts payable and other liabilities’ in the consolidated balance sheets.

Regulatory Requirements and Sub

Regulatory Requirements and Subsidiary Dividend Restrictions	12 Months Ended
	Sep. 30, 2020
Capital and Other Regulatory Requirements [Abstract]
Regulatory Requirements and Subsidiary Dividend Restrictions	Regulatory Requirements and Subsidiary Dividend Restrictions The Company’s subsidiary StoneX Financial is registered as a broker dealer and member of the Financial Industry Regulatory Authority (“FINRA”) subject to the SEC Uniform Net Capital Rule 15c3-1, which requires the maintenance of minimum net capital. StoneX Financial is also a futures commission merchant registered with the CFTC and subject to the net capital requirements of the CFTC Regulation 1.17. Under the more restrictive of these rules, StoneX Financial is required to maintain “adjusted net capital”, equivalent to the greater of $1,000,000 or 8 percent of client and non-client risk maintenance margin requirements on all positions, as defined in such rules, regulations, and requirements. Adjusted net capital and the related net capital requirement may fluctuate on a daily basis. StoneX Financial also has a restriction on dividends, which restricts the withdrawal of equity capital if the planned withdrawal would reduce net capital, subsequent to haircuts and charges, to an amount less than 120% of the greatest minimum requirement. The Company’s subsidiary Gain Capital Group, LLC is subject to regulation by the CFTC and NFA and is required to maintain specific levels of regulatory capital. As a futures commission merchant and retail foreign exchange dealer, Gain Capital Group, LLC is required to maintain adjusted net capital of the greater of $1.0 million or 8% of customer and non-customer risk maintenance margin, or $20.0 million plus 5.0% of the amount of retail customer liabilities over $10.0 million, plus 10% of all liabilities owed to eligible contract participant counterparties acting as a dealer that are not an affiliate. StoneX Financial as a registered securities carrying broker dealer is also subject to Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), which requires the Company to maintain separate accounts for the benefit of securities clients and proprietary accounts of broker dealers (“PABs”). These client protection rules require the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. As of September 30, 2020, StoneX Financial prepared reserve computations for the client accounts and PAB accounts in accordance with the customer reserve computation guidelines set forth in Rule 15c3-3. Based upon these computations, the customer reserve requirement was $18.5 million as of September 30, 2020. The Company held $17.3 million in the customer SRBA as of September 30, 2020 and made additional deposits of $6.2 million on October 2, 2020, to meet the customer segregation and segregated deposit timing requirements of Rule 15c3-3. The PAB reserve requirement was $2.2 million as of September 30, 2020. The Company held $2.1 million in the PAB SRBA as of September 30, 2020, and made additional deposits of $1.1 million on October 2, 2020, to meet the PAB segregation and segregated deposit timing requirements of Rule 15c3-3. Pursuant to the requirements of the Commodity Exchange Act, funds deposited by clients of StoneX Financial and Gain Capital Group, LLC relating to their trading of futures and options on futures on a U.S. commodities exchange must be carried in separate accounts which are designated as segregated clients’ accounts. Pursuant to the requirements of the CFTC, funds deposited by clients of StoneX Financial and Gain Capital Group, LLC relating to their trading of futures and options on futures traded on, or subject to the rules of, a foreign board of trade must be carried in separate accounts in an amount sufficient to satisfy all of StoneX Financial’s and Gain Capital Group, LLC’s current obligations to clients trading foreign futures and foreign options on foreign commodity exchanges or boards of trade, which are designated as secured clients’ accounts. As of September 30, 2020, StoneX Financial had client segregated and client secured funds of $3,089.9 million and $162.6 million, respectively, compared to a minimum regulatory requirement of $3,030.6 million and $150.1 million, respectively. As of September 30, 2020, Gain Capital Group, LLC had client segregated and client secured funds of $340.4 million and $4.3 million, respectively, compared to a minimum regulatory requirement of $319.8 million and $2.5 million, respectively. The Company’s subsidiaries StoneX Financial Ltd. and Gain Capital U.K. Ltd. are regulated by the Financial Conduct Authority (“FCA”), the regulator of the financial services industry in the U.K. The regulations impose regulatory capital, as well as conduct of business, governance, and other requirements. The conduct of business rules include those that govern the treatment of client money and other assets which under certain circumstances for certain classes of client must be segregated from the firm’s own assets. As of September 30, 2020, StoneX Financial Ltd. and Gain Capital U.K. Ltd. had client segregated funds of $516.5 million and $206.9 million, respectively, compared to a minimum regulatory requirement of $505.6 million and $205.6 million, respectively. StoneX Financial Pte. Ltd. is regulated by the Monetary Authority of Singapore (“MAS”) and operates as an approved holder of a Capital Market Services License. StoneX Financial Pte. Ltd. is subject to the requirements of MAS and pursuant to the Securities and Futures Act. The regulations include those that govern the treatment of client money and other assets which under certain circumstances must be segregated from the firm’s own assets. As of September 30, 2020, StoneX Financial Pte. Ltd. had client segregated funds of $340.6 million compared to a minimum regulatory requirement of $338.9 million. The following table details the Company’s subsidiaries with a minimum regulatory net capital requirement in excess of $5.0 million as well as the actual regulatory capital of the subsidiary as of September 30, 2020 (in millions): Subsidiary Regulatory Authority Actual Minimum StoneX Financial Inc. SEC and CFTC $ 229.8 $ 137.6 StoneX Financial Ltd. FCA $ 264.3 $ 145.1 Gain Capital Group, LLC CFTC $ 71.5 $ 32.2 Gain Capital U.K. Ltd. FCA $ 185.4 $ 65.2

Securities and Commodity Financ

Securities and Commodity Financing Transactions	12 Months Ended
	Sep. 30, 2020
Brokers and Dealers [Abstract]
Securities and Commodity Financing Transactions	Securities and Commodity Financing Transactions The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed and securities loaned transactions to, among other things, fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, and to accommodate counterparties’ needs under matched-book trading strategies. These agreements are recorded as collateralized financings at their contractual amounts plus accrued interest. The related interest is recorded in the consolidated income statements as interest income or interest expense, as applicable. In connection with these agreements and transactions, it is the policy of the Company to receive or pledge cash or securities to adequately collateralize such agreements and transactions in accordance with contractual agreements. The collateral is valued daily and the Company may require counterparties to deposit additional collateral or return collateral pledged. The Company pledges financial instruments owned to collateralize repurchase agreements. At September 30, 2020 and 2019, financial instruments owned, at fair value of $468.6 million and $478.8 million, respectively, were pledged as collateral under repurchase agreements. The counterparty has the right to repledge the collateral in connection with these transactions. These financial instruments owned have been pledged as collateral and have been parenthetically disclosed on the consolidated balance sheets. In addition, as of September 30, 2020 and 2019, the Company pledged financial instruments owned, at fair value of $1,266.4 million and $1,228.9 million, respectively, to cover collateral requirements for tri-party repurchase agreements. These securities have not been parenthetically disclosed on the consolidated balance sheets since the counterparties do not have the right to sell or repledge the collateral. The Company also repledged securities received under reverse repurchase agreements of $1,484.7 million and $1,175.1 million, respectively, to cover collateral requirements for tri-party repurchase agreements. The Company also has repledged securities borrowed and client securities held under custodial clearing arrangements to collateralize securities loaned agreements with a fair value of $1,410.3 million and $1,414.0 million as of September 30, 2020 and 2019, respectively. At September 30, 2020 and 2019, the Company had accepted collateral that it is permitted by contract to sell or repledge. This collateral consists primarily of securities received in reverse repurchase agreements, securities borrowed agreements, and margin securities held on behalf of correspondent brokers. The fair value of such collateral at September 30, 2020 and 2019 was $3,303.1 million and $3,060.2 million, respectively, of which $285.7 million and $329.8 million, respectively, was used to cover securities sold short which are recorded in financial instruments sold, not yet purchased on the consolidated balance sheets. In the normal course of business, this collateral is used by the Company to cover financial instruments sold, not yet purchased, to obtain financing in the form of repurchase agreements, and to meet counterparties’ needs under lending arrangements and matched-book trading strategies. The following tables provide the contractual maturities of gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): September 30, 2020 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 1,736.3 $ 1,069.2 $ 325.0 25.0 $ 3,155.5 Securities loaned 1,441.9 — — — 1,441.9 Gross amount of secured financing $ 3,178.2 $ 1,069.2 $ 325.0 $ 25.0 $ 4,597.4 September 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 1,553.9 $ 565.8 $ 654.0 — $ 2,773.7 Securities loaned 1,459.9 — — — 1,459.9 Gross amount of secured financing $ 3,013.8 $ 565.8 $ 654.0 — $ 4,233.6 The following table provides the underlying collateral types of the gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): Securities sold under agreements to repurchase September 30, 2020 September 30, 2019 U.S. Treasury obligations $ 815.8 $ 108.8 U.S. government agency obligations 279.5 359.5 Asset-backed obligations 18.0 96.7 Agency mortgage-backed obligations 1,990.0 2,208.7 Corporate bonds 52.2 — Total securities sold under agreement to repurchase $ 3,155.5 $ 2,773.7 Securities loaned Equity securities 1,441.9 1,459.9 Total securities loaned 1,441.9 1,459.9 Gross amount of secured financing $ 4,597.4 $ 4,233.6 The following tables provide the netting of securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed and securities loaned as of the periods indicated (in millions): September 30, 2020 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 1,696.2 $ — $ 1,696.2 Securities borrowed $ 1,440.0 $ — $ 1,440.0 Securities sold under agreements to repurchase $ 3,155.5 $ — $ 3,155.5 Securities loaned $ 1,441.9 $ — $ 1,441.9 September 30, 2019 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 1,474.4 $ (49.9) $ 1,424.5 Securities borrowed $ 1,423.2 $ — $ 1,423.2 Securities sold under agreements to repurchase $ 2,823.6 $ (49.9) $ 2,773.7 Securities loaned $ 1,459.9 $ — $ 1,459.9

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Share-based compensation expense is included in ‘compensation and benefits’ in the consolidated income statements and totaled $10.3 million, $8.1 million and $6.6 million for the fiscal years ended September 30, 2020, 2019, and 2018, respectively. Stock Option Plans The Company sponsors a stock option plan for its directors, officers, employees and consultants. The 2013 Stock Option Plan, which was approved by the Company’s Board of Directors and shareholders, authorizes the Company to issue stock options covering up to 2.0 million shares of the Company’s common stock. As of September 30, 2020, there were 0.7 million shares authorized for future grant under this plan. Awards that expire or are canceled generally become available for issuance again under the plan. The Company settles stock option exercises with newly issued shares of common stock. Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions: Fiscal Year Ended September 30, 2020 2020 (1) 2019 2018 Expected stock price volatility — % 27 % 30 % Expected dividend yield — % — % — % Risk free interest rate — % 1.86 % 1.23 % Average expected life (in years) 0.00 6.05 3.06 (1) There were no stock options granted under the plan during the year ended September 30, 2020. Expected stock price volatility rates are primarily based on the historical volatility. The Company has not paid dividends in the past and does not currently expect to do so in the future. Risk free interest rates are based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option or award. The average expected life represents the estimated period of time that options or awards granted are expected to be outstanding, based on the Company’s historical share option exercise experience for similar option grants. The weighted average fair value of options issued during fiscal years ended September 30, 2020, 2019, and 2018 was $0.00, $10.47 and 9.79, respectively. The following is a summary of stock option activity for the year ended September 30, 2020: Shares Number of Weighted Weighted Weighted Aggregate Balances at September 30, 2019 692,652 1,684,378 $ 37.59 $ 11.32 4.62 $ 9.2 Exercised (244,511) $ 30.56 $ 11.36 Forfeited 13,662 (13,662) $ 39.64 $ 8.62 Expired 18,169 (18,169) $ 37.30 $ 8.19 Balances at September 30, 2020 724,483 1,408,036 $ 38.79 $ 11.38 4.16 $ 17.4 Exercisable at September 30, 2020 423,112 $ 29.25 $ 12.64 1.38 $ 9.3 The total compensation cost not yet recognized for non-vested awards of $7.2 million as of September 30, 2020 has a weighted-average period of 5.35 years over which the compensation expense is expected to be recognized. The total intrinsic value of options exercised during fiscal years ended September 30, 2020, 2019, and 2018 was $4.2 million, $0.7 million and $2.1 million, respectively. The options outstanding as of September 30, 2020 broken down by exercise price are as follows: Exercise Price Number of Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Term $ — - $ 5.00 — n/a n/a $ 5.00 - $ 10.00 — n/a n/a $ 10.00 - $ 15.00 — n/a n/a $ 15.00 - $ 20.00 — n/a n/a $ 20.00 - $ 25.00 — n/a n/a $ 25.00 - $ 30.00 420,000 $ 25.91 1.36 $ 30.00 - $ 35.00 — n/a n/a $ 35.00 - $ 40.00 126,161 $ 39.65 2.02 $ 40.00 - $ 45.00 859,875 $ 44.92 5.84 $ 45.00 - $ 50.00 — n/a n/a $ 50.00 - $ 55.00 — n/a n/a $ 55.00 - $ 60.00 2,000 $ 55.28 1.89 1,408,036 $ 38.79 4.16 Restricted Stock Plan The Company sponsors a restricted stock plan for its directors, officers and employees. The Company’s 2017 restricted stock plan, which was approved by the Company’s Board of Directors and shareholders, authorizes up to 1.5 million shares to be issued. As of September 30, 2020, 0.9 million shares were authorized for future grant under the restricted stock plan. Awards that expire or are canceled generally become available for issuance again under the plan. The Company utilizes newly issued shares of common stock to make restricted stock grants. The following is a summary of restricted stock activity through September 30, 2020: Shares Number of Weighted Weighted Aggregate Balances at September 30, 2019 1,156,902 350,778 $ 40.06 1.36 $ 14.4 Granted (299,858) 299,858 $ 44.94 Vested — (161,880) $ 40.26 Forfeited 4,410 (4,410) $ 44.23 Balances at September 30, 2020 861,454 484,346 $ 42.97 1.37 $ 24.8 The total compensation cost not yet recognized of $15.6 million as of September 30, 2020 has a weighted-average period of 1.37 years over which the compensation expense is expected to be recognized. Compensation expense is amortized on a straight-line basis over the vesting period. Restricted stock grants are included in the Company’s total issued and outstanding common shares.

Retirement Plans

Retirement Plans	12 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Retirement Plans	Retirement Plans Defined Benefit Retirement Plans The Company has a frozen qualified defined benefit pension plan (the “Qualified Plan”) and a nonqualified defined benefit pension plan (the “Nonqualified Plan”), and recognizes their funded status, measured as the difference between the fair value of the plan assets and the projected benefit obligation, in “other assets” or “accounts payable and other accrued liabilities” in the consolidated balance sheets, depending on the funded status of each plan. The Qualified Plan assets, which are managed in a third-party trust, primarily consist of a diversified blend of approximately 80% debt securities and 20% equity investments and had a total fair value of $40.8 million and $38.9 million as of September 30, 2020 and 2019, respectively. All Qualified Plan assets fall within Level 2 of the fair value hierarchy. The benefit obligation associated with the Qualified Plan will vary over time only as a result of changes in market interest rates, the life expectancy of the plan participants, and benefit payments, since the accrual of benefits was suspended when the Qualified Plan was frozen in 2006. The benefit obligation was $38.1 million and $36.5 million and the discount rate assumption used in the measurement of this obligation was 2.55% and 3.10% as of September 30, 2020 and 2019, respectively. Related to the Qualified Plan, the Company’s net pension obligation was in a funded status of $2.7 million and $2.4 million as of September 30, 2020 and 2019, respectively. The Nonqualified Plan assets had a total fair value of less than $0.1 million as of September 30, 2020 and 2019. The benefit obligation associated with the Nonqualified Plan will vary over time only as a result of changes in market interest rates, the life expectancy of the plan participants, and benefit payments. There are no active participants in the Nonqualified plan. The benefit obligation was $1.6 million and $1.7 million as of September 30, 2020 and 2019, respectively. Related to the Nonqualified Plan, the Company’s unfunded pension obligation was $1.6 million as of September 30, 2020 and 2019. The Company recognized a net periodic benefit of $0.4 million, $0.1 million and $0.2 million for the year ended September 30, 2020, 2019 and 2018, respectively. The expected long-term return on plan assets assumption was 4.35% for 2020. The Company made contributions of $0.1 million to the plans in the years ended September 30, 2020 and 2019. The Company complies with minimum funding requirements. The estimated undiscounted future benefit payments are expected to be $2.1 million in 2021, $2.1 million in 2022, $2.1 million in 2023, $2.1 million in 2024, $2.0 million in 2025 and $9.5 million in 2026 through 2030. Defined Contribution Retirement Plans The Company offers participation in the StoneX Group Inc. 401(k) Plan (“401(k) Plan”), a defined contribution plan providing retirement benefits to all domestic full-time non-temporary employees who have reached 21 years of age. Employees may contribute from 1% to 80% of their annual compensation to the 401(k) Plan, limited to a maximum annual amount as set periodically by the Internal Revenue Service. The Company makes matching contributions to the 401(k) Plan in an amount equal to 62.5% of each participant’s eligible elective deferral contribution to the 401(k) Plan, up to 8% of employee compensation. Matching contributions vest, by participant, based on the following years of service schedule: less than two years – none, after two years – 33%, after three years – 66%, and after four years – 100%. U.K. based employees of StoneX Group are eligible to participate in a defined contribution pension plan. The Company contributes double the employee’s contribution up to 10% of total base salary for this plan. For this plan, employees are 100% vested in both the employee and employer contributions at all times. For fiscal year ended September 30, 2020, 2019 and 2018, the Company’s contributions to these defined contribution plans were $10.1 million, $7.5 million and $6.8 million, respectively.

Other Expenses

Other Expenses	12 Months Ended
	Sep. 30, 2020
Other Expenses [Abstract]
Other Expenses	Other Expenses Other expenses for the years ended September 30, 2020, 2019, and 2018 are comprised of the following: Year Ended September 30, (in millions) 2020 2019 2018 Insurance $ 4.7 $ 3.4 $ 2.6 Office supplies and printing 1.8 1.9 1.7 Other clearing related expenses 2.8 2.5 2.5 Other non-income taxes 6.6 4.6 4.9 Contingent consideration, net 0.5 — — Other 13.2 10.8 8.4 Total other expenses $ 29.6 $ 23.2 $ 20.1

Bad Debt on Physical Coal

Bad Debt on Physical Coal	12 Months Ended
	Sep. 30, 2020
Bad Debt on Physical Coal [Abstract]
Bad Debt on Physical Coal	Bad Debt on Physical Coal During the year ended September 30, 2018 and 2017, the Company recorded charges to earnings of $1.0 million and $47.0 million, respectively, to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business, conducted solely in the Company’s Singapore subsidiary, StoneX APAC Pte. Ltd., with a coal supplier. Components of the bad debt on physical coal included allowances on amounts due to the Company from its supplier related to: coal paid for but not delivered to clients; reimbursement of demurrage claims, dead freight and other charges paid by StoneX APAC Pte. Ltd. to its clients; reimbursement due for deficiencies in the quality of coal delivered to clients; and losses incurred related to the cancellation of open sales contracts. During the year ended September 30, 2018, the Company completed its exit of the physical coal business. During the year ended September 30, 2019, the Company reached settlements with clients, paying $8.4 million related to demurrage, dead freight, and other penalty charges regarding coal supplied during fiscal 2017. The settlement amounts paid were less than the accrued liabilities for the transactions recorded during fiscal 2018 and fiscal 2017, and accordingly the Company recorded a recovery on the bad debt on physical coal of $2.4 million. During the year ended September 30, 2019, the Company also received $10.0 million through an insurance policy claim related to the physical coal matter, and recorded the insurance proceeds as an additional recovery. The Company has presented the bad debt on physical coal and subsequent recoveries separately as a component of income before tax in the consolidated income statements.

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effects of the Tax Cuts and Jobs Act On December 22, 2017, the President of the United States signed and enacted into law H.R. 1, the Tax Cuts and Jobs Act (“the Tax Reform”). Among the significant changes to the U.S. Internal Revenue Code, the Tax Reform lowered the U.S. federal corporate income tax rate from 35% to 21%, effective January 1, 2018. The Company computed its income tax expense for the years ending September 30, 2020 and 2019 using a U.S. statutory tax rate of 21%. The Company computed income tax expense for the year ended September 30, 2018 using a U.S. statutory tax rate of 24.5%. The Tax Reform imposed a mandatory repatriation transition tax on previously untaxed accumulated and current earnings and profits (“E&P”) of certain foreign subsidiaries for the year ended September 30, 2018. The Tax Reform also established new tax laws that affected the years ending September 30, 2020 and 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. For the year ended September 30, 2018, the Company recorded income tax expense of $8.6 million related to the remeasurement of deferred tax assets and liabilities, which increased the effective tax rate by 8.5%. The Tax Reform also included a mandatory repatriation transition tax on previously untaxed accumulated and current E&P of certain of the Company’s foreign subsidiaries. To determine the amount of the transition tax, the Company determined, in addition to other factors, the amount of post 1986 E&P of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. The Company recorded a transition tax obligation of $11.2 million during the year ended September 30, 2018, which increased the effective tax rate by 11% during the year ended September 30, 2018. Coronavirus Aid, Relief, and Economic Security Act On March 27, 2020, the U.S. government enacted the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”), which provides economic relief in response to the coronavirus pandemic. The CARES Act, among other things, includes provisions to allow certain net operating losses to be carried-back up to five years, to increase interest deduction limitations, accelerates the refunds of alternative minimum tax credits, and makes technical corrections to tax depreciation methods for qualified leasehold improvement property. The Company evaluated and properly accounted for the provisions of the CARES Act and there was no material impact to the Company’s consolidated financial statements. Income tax expense (benefit) for the years ended September 30, 2020, 2019, and 2018 was allocated as follows: Year Ended September 30, (in millions) 2020 2019 2018 Income tax expense attributable to income from operations $ 37.1 $ 25.9 $ 46.0 Taxes allocated to stockholders’ equity, related to pension liabilities — (0.2) 0.1 Total income tax expense $ 37.1 $ 25.7 $ 46.1 The components of income tax expense (benefit) attributable to income from operations were as follows: Year Ended September 30, (in millions) 2020 2019 2018 Current taxes: U.S. federal $ (0.6) $ (1.9) $ 0.8 U.S. State and local 2.3 (0.8) 0.5 International 31.3 24.9 22.4 Total current taxes 33.0 22.2 23.7 Deferred taxes 4.1 3.7 22.3 Income tax expense $ 37.1 $ 25.9 $ 46.0 U.S. and international components of income (loss) from operations, before tax, was as follows: Year Ended September 30, (in millions) 2020 2019 2018 U.S. $ 88.8 $ (2.6) $ 9.9 International 117.9 113.6 91.6 Income from operations, before tax $ 206.7 $ 111.0 $ 101.5 Items accounting for the difference between income taxes computed at the federal statutory rate and income tax expense were as follows: Year Ended September 30, 2020 2019 2018 Federal statutory rate effect of: 21.0 % 21.0 % 24.5 % U.S. State and local income taxes 1.0 % (1.5) % 0.8 % Foreign earnings and losses taxed at different rates 0.1 % 0.7 % (0.8) % Change in foreign valuation allowance 1.0 % 1.0 % (0.8) % Change in state valuation allowance 0.2 % 0.5 % — % U.S. permanent items 0.9 % 0.1 % (0.2) % Foreign permanent items 0.5 % 0.7 % 2.1 % U.S. bargain purchase gain (8.3) % (1.0) % — % Remeasurement of deferred tax — % — % 8.5 % Repatriation Transition tax — % — % 11.0 % GILTI 0.7 % 2.2 % — % Other reconciling items 0.9 % (0.4) % 0.2 % Effective rate 18.0 % 23.3 % 45.3 % The components of deferred income tax assets and liabilities were as follows: (in millions) September 30, 2020 September 30, 2019 Deferred tax assets: Share-based compensation $ 3.1 $ 3.3 Deferred compensation 4.1 3.6 Foreign net operating loss carryforwards 5.4 2.6 U.S. State and local net operating loss carryforwards 9.0 9.2 U.S. federal net operating loss carryforwards 1.8 1.1 Intangible assets 9.9 4.8 Bad debt reserve 4.4 1.3 Tax credit carryforwards 0.2 0.5 Foreign tax credit carryforwards 2.4 5.0 Other compensation 5.8 2.2 Property and equipment 7.3 — Other 1.9 1.1 Total gross deferred tax assets 55.3 34.7 Less valuation allowance (12.4) (8.5) Deferred tax assets 42.9 26.2 Deferred income tax liabilities: Unrealized gain on securities 2.4 3.2 Prepaid expenses 3.4 2.2 Property and equipment — 2.6 Pension liability 0.2 0.2 Deferred income tax liabilities 6.0 8.2 Deferred income taxes, net $ 36.9 $ 18.0 Deferred income tax balances reflect the effects of temporary differences between the carrying amounts of assets and liabilities and their tax bases and are stated at enacted tax rates expected to be in effect when taxes are actually paid or recovered. As of September 30, 2020 and September 30, 2019, the Company has net operating loss carryforwards for U.S. federal, state, local, and foreign income tax purposes of $6.9 million and $7.1 million, net of valuation allowances, respectively, which are available to offset future taxable income in these jurisdictions. The state and local net operating loss carryforwards of $4.7 million, net of valuation allowance, begin to expire after September 2022. The Company also has $0.6 million, net of valuation allowances, of federal net operating loss carryforwards, which consist of a portion that will expire in tax years ending 2031 through 2036. The remaining portion of the federal net operating loss carryforwards do not expire, but cannot be utilized until after 2037 and are limited by Internal Revenue Code (“IRC”) Section 382. As of September 30, 2020, Gain Capital UK Ltd. has a net operating loss carryforward of $0.9 million. As a result of Tax Reform, the AMT credit carryforward deferred tax asset was reclassified to income taxes receivable during the year ended September 30, 2018. As a result of the CARES Act, the AMT credit carryforward was 50% refundable during the year ending September 30, 2019 and the remaining 50% is refundable in the year ended September 30, 2020, to the extent it is not used to offset regular income tax liability. During the year ended September 30, 2018, the Company generated $5.1 million in foreign tax credit carryforwards as part of the mandatory repatriation transition tax. These credits are being fully utilized during the year ended September 30, 2020. The Company also has $1.3 million, net of valuation allowance, in foreign tax credits due to the merger with Gain, as further discussed in Note 21, which expire in 2023. In the judgment of management, the Company believes that sufficient taxable income will be earned to utilize the foreign tax credit carryforwards, net of valuation allowance, before they expire. The valuation allowance for deferred tax assets as of September 30, 2020 was $12.4 million. The net change in the total valuation allowance for the year ended September 30, 2020 was an increase of $3.9 million. Of this amount, $1.1 million was related to foreign tax credits acquired through the merger with Gain, which are limited by provision of IRC Section 383 and expire in 2023. The remaining increase is related to foreign and state net operating loss carryforwards. The valuation allowances as of September 30, 2020 and September 30, 2019 were primarily related to U.S. state and local and foreign net operating loss carryforwards that, in the judgment of management, are not more likely than not to be realized. T he Company does not intend to distribute earnings of its foreign subsidiaries 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, and earnings that would not result in any significant foreign taxes. The Company repatriated $30.0 million and $13.0 million during the years ended September 30, 2020 and September 30, 2019, respectively, of earnings previously taxed in the U.S. resulting in no significant incremental taxes. Therefore, the Company has not recognized a deferred tax liability on its investment in foreign subsidiaries. The Company had a de minimis balance of unrecognized tax benefits as of September 30, 2020, 2019, and 2018 that, if recognized, would affect the effective tax rate. Accrued interest and penalties are included in the related tax liability line in the consolidated balance sheets. The Company had no accrued interest and penalties included in the consolidated balance sheets as of September 30, 2020 and September 30, 2019. The Company recognizes accrued interest and penalties related to income taxes as a component of income tax expense. The Company had a de minimus amount of interest, net of federal benefit, and penalties recognized as a component of income tax expense during the years ended September 30, 2020, 2019, and 2018.

Acquisitions

Acquisitions	12 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Acquisitions	Acquisitions The Company’s consolidated financial statements include the operating results and cash flows of the acquired businesses from the dates of acquisition. Acquisitions in Fiscal 2020 Gain Capital Holdings, Inc. On February 26, 2020, the Company entered into a definitive merger agreement to acquire Gain. The Company agreed to acquire Gain for $6.00 per share in an all-cash transaction. Gain is a global provider of trading services and solutions to institutional and retail investors, specializing in both OTC products and exchange-traded futures and options on futures. Gain provides its clients with access to a diverse range of global OTC financial markets, including spot foreign exchange, precious metals, and CFDs (where permitted). As a result of the acquisition, the Company added a new digital platform to its global financial network, significantly expanded its offerings to retail clients, as well as added a complementary exchange-traded futures and options on futures business. The acquisition of Gain is also expected to accelerate the digitization of the Company’s trading platforms. The merger closed on July 30, 2020 (“the Gain acquisition date”) subsequent to approval by Gain’s shareholders, approval by regulators, and the completion of customary closing conditions. On the Gain acquisition date, each issued and outstanding share of Gain common stock (other than shares of Gain common stock held by those Gain stockholders who had properly demanded and not waived or withdrawn appraisal rights under Delaware law as further discussed below) automatically converted into the right to receive $6.00 per share in cash. Purchase Price The aggregate merger consideration was (in millions): Aggregate cash consideration $ 215.0 Accrual for merger cash consideration 21.6 Total merger consideration $ 236.6 Subsequent to the Gain acquisition date, holders of 3.6 million shares of Gain common stock outstanding at the Gain acquisition date who did not vote to approve the merger (“Dissenting Holders”, and the shares held by such Dissenting Holders, the “Dissenting Shares”) purportedly demanded appraisal rights pursuant to Section 262 of the Delaware General Corporation Law in the Court of Chancery of the State of Delaware. The $21.6 million accrual for merger consideration included in the aggregate merger consideration was based upon 3.6 million Dissenting Shares assuming a right to receive $6.00 per share at the Gain acquisition date. Any subsequent settlement with the Dissenting Holders will be considered the settlement of a post-acquisition contingency to be included in the Company’s post-acquisition consolidated income statements. Preliminary Purchase Price Allocation The consolidated financial statements have been prepared using the acquisition method of accounting under U.S. GAAP with the Company treated as the acquirer of Gain for accounting purposes. Under the acquisition method of accounting, the aggregate merger consideration was allocated to the assets acquired and liabilities assumed generally based on their fair value at the Gain acquisition date. The Company has made significant estimates and assumptions in determining the fair value of assets acquired and liabilities based upon discussions with management and informed insights into the industries in which Gain operates. These significant estimates and assumptions include, but are not limited to, projected cash flows of the acquired business, client attrition rates, discount rates, royalty rates, and economic lives of the identified assets. The Company engaged a third party valuation specialist to assist with assessing the overall reasonableness of the bargain purchase gain as further discussed below and determining the fair value of the net identifiable assets acquired. The following table summarizes the preliminary purchase price allocation as of the Gain acquisition date (in millions): Preliminary Purchase Price Allocation Cash and cash equivalents $ 507.2 Cash, securities and other assets segregated under federal and other regulations 497.4 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties (1) 249.7 Receivables from clients, net (2) 2.0 Income taxes receivable 0.4 Deferred income taxes, net 23.0 Property and equipment, net 6.1 Right of use assets, net 15.0 Other assets 17.9 Total fair value of tangible assets acquired 1,318.7 Accounts payable and other accrued liabilities 52.7 Operating lease liabilities 15.0 Payable to clients 863.4 Payable to broker-dealers, clearing organizations, and counterparties 0.5 Income taxes payable 12.4 Convertible senior notes (3) 92.0 Total fair value of tangible liabilities assumed 1,036.0 Fair value of tangible net assets acquired (4) 282.7 Identifiable intangible assets acquired Trademarks/domain names (5) 3.7 Software programs/platforms (5) 22.2 Customer base (5) 9.8 Total fair value of intangible assets acquired 35.7 Fair value of identifiable net assets acquired 318.4 Total merger consideration 236.6 Bargain purchase gain $ 81.8 (1) Amount represents the contractual amount of deposits with and receivables from broker-dealers, clearing organizations, and counterparties, all of which the Company expects to be collectible as of the Gain acquisition date. (2) 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 Gain acquisition date. (3) As $91.5 million of the $92.0 million in aggregate principal of the Gain Notes were redeemed on September 1, 2020, the Company believes that the face value of the Gain Notes approximated their fair value as of the Gain acquisition date due to the fundamental change right provided for in the Gain Notes indenture. Refer to Note 12 for further discussion of the Gain Notes redemption. (4) With the exception of deferred income taxes and the convertible senior notes, the Company believes that the fair value of the tangible assets acquired and tangible liabilities assumed approximate their carrying values as of the Gain acquisition date due either to their short-term nature, the Company’s ability to initiate the withdrawal and settlement of client related trading balances, or the fact that the balances are recorded at fair value on a recurring basis. (5) The trademark/domain names, software programs/platforms, and customer base intangible assets have been assigned useful lives of 5 years, 3 years, and 4 years, respectively. The Company believes that the transaction resulted in a bargain purchase gain primarily due to the significant market volatility experienced during the first calendar quarter of 2020, primarily as a result of the COVID-19 pandemic. The market volatility experienced during 2020 through the Gain acquisition date increased significantly compared to corresponding historical periods. This resulted in Gain generating windfall profits and a corresponding increase in net tangible book value. The bargain purchase gain is included in ‘Gain on acquisitions and other gains’ on the Company’s consolidated income statement for the year ended September 30, 2020. Post-Acquisition Results and Unaudited Pro Forma Information Gain’s results of operations and cash flows have been included in the Company’s consolidated financial statements for the period subsequent to July 31, 2020. For the year ended September 30, 2020, the Company’s results include total revenues and net income from Gain of $49.0 million and $1.8 million, respectively. The following unaudited pro forma financial information (in millions, except per share amounts) has been adjusted to give effect to the Gain merger as if it were consummated on October 1, 2018. Year Ended September 30, 2020 Year Ended September 30, 2019 Total revenues $ 54,414.1 $ 33,160.0 Net income $ 138.5 $ 38.3 Basic earnings per share $ 7.17 $ 2.01 Diluted earnings per share $ 7.02 $ 1.97 The unaudited pro forma financial information includes material, nonrecurring pro forma adjustments directly attributable to the Gain acquisition primarily including the adjustment for a goodwill impairment loss, adjustment for the bargain purchase gain, adjustments to the amortization of intangible assets, and adjustments for direct and incremental acquisition-related costs and the related tax effects. The unaudited pro forma financial information does not include any revenue or cost saving synergies from operating efficiencies or the effect of incremental costs incurred from integrating the companies. The Company incurred costs related to the merger of $5.2 million for the year ended September 30, 2020, that are included within ‘Professional fees’ on the consolidated income statement. The business acquired has been assigned to the Company’s Retail and Institutional reportable segments. UOB Bullion and Futures Limited On March 19, 2019, the Company’s subsidiary StoneX Financial Pte Ltd executed an asset purchase agreement to acquire the futures and options brokerage and clearing business of UOB Bullion and Futures Limited (“UOB”), a subsidiary of United Overseas Bank Limited. Closing was conditional upon receiving regulatory approval by the Monetary Authority of Singapore. This acquisition provides the Company access to an established institutional client base and also augments the Company’s global service capabilities in Singapore. The cash purchase price for the acquired assets was $5.0 million of which $2.5 million was due upon the execution of the asset purchase agreement and the remaining $2.5 million was due upon the closing of the acquisition, which occurred on October 7, 2019. The purchase price allocation resulted in the recognition of liabilities assumed related to the futures and options on futures client account balances of approximately $351.8 million as of the acquisition date, which was recorded within ‘payables to clients’ on the consolidated balance sheet, and an equal and offsetting amount of assets acquired. The carrying amount of the client assets and related liabilities was assumed to approximate fair value due to their short-term nature, the Company’s ability to initiate the withdrawal and settlement of client related trading balances, and the fact that the open derivative positions are recorded at fair value on a recurring basis. The Company also acquired certain client base intangible assets and property and equipment in connection with the acquisition. The Company engaged a third-party valuation specialist to assist with the valuation of the acquired intangible assets and property and equipment. As of the acquisition date, $0.8 million of the purchase price was allocated to the fair value of the property and equipment acquired and $3.1 million was allocated to the fair value of the client base intangible assets acquired. The remaining excess of the purchase price over the fair value of the net assets acquired of $1.1 million was allocated to goodwill. The Company believes the goodwill represents the synergies that can be realized from integrating the acquired business into its existing exchange-traded futures and option business. The allocation of the purchase price to the fair value of assets acquired and liabilities assumed is considered final as of September 30, 2020. The business acquired has been assigned to the Company’s Institutional reportable segment. The client base intangible assets have been assigned a useful life of 5 years. UOB’s results of operations and cash flows have been included in the Company’s consolidated financial statements for the period subsequent to October 7, 2019. For the year ended September 30, 2020, the Company’s results include total revenues and net loss from UOB of $10.3 million and $1.4 million, respectively. Tellimer In December 2019, the Company executed a definitive purchase agreement to acquire the brokerage businesses of Tellimer Group (“Tellimer”). This transaction involved the stock purchase of 100% of Exotix Partners, LLP, based in the United Kingdom, and the stock purchase of 100% of Tellimer Capital Ltd based in Nigeria. The closing of this transaction was subject to limited conditions including regulatory approval in the relevant jurisdictions. The cash purchase price was equal to the net tangible book value of the acquired entities upon closing. Regulatory approval for the acquisition of Exotix Partners, LLP, was obtained during the period with the acquisition closing on April 1, 2020. The cash purchase price for the acquisition of Exotix Partners, LLP, was $4.7 million. The final allocation of the cash purchase price to the fair value of assets acquired and liabilities assumed resulted in the recognition of $1.0 million in cash and cash equivalents, $1.0 million in receivables from clients, net, $0.3 million in property and equipment, net, $3.4 million in other assets, and $1.0 million in liabilities assumed. Regulatory approval for the acquisition of Tellimer Capital Ltd was obtained during the period with the acquisition closing on June 1, 2020. The cash purchase price for the acquisition of Tellimer Capital Ltd and the related allocation to the fair value of assets acquired and liabilities assumed was not material to the Company’s consolidated financial statements. Tellimer’s results of operations and cash flows have been included in the Company’s consolidated financial statements from the dates of acquisition. For the year ended September 30, 2020, the Company’s results include total revenues and net loss from Tellimer of $5.9 million and less than $0.1 million, respectively. The acquired business have been assigned to the Company’s Institutional reportable segment. IFCM Commodities On January 2, 2020, the Company’s wholly owned subsidiary, INTL Netherlands B.V., executed and closed on a stock purchase agreement to acquire 100% of the equity interests of IFCM Commodities GmbH (“IFCM”) based in Germany. IFCM specializes in providing commodity price risk management solutions for base metals serving clients across Germany and continental Europe and historically introduced clients to StoneX Financial Ltd. This purchase is part of the Company’s overall strategic plan to expand the Company’s footprint in Germany and continental Europe in order to handle European clients and regional metals business following Brexit. The cash purchase price of $1.9 million was equal to net tangible book value upon closing plus a premium of $1.0 million. The excess of the cash consideration over the fair value of the net tangible assets acquired on the closing date was allocated to the fair value of IFCM’s client relationships. This client base intangible asset has been assigned, and will be amortized over, a useful of five years. IFCM’s results of operations and cash flows have been included in the Company’s consolidated financial statements for the period subsequent to January 2, 2020. For the year ended September 30, 2020, the Company’s results include total revenues and net income from IFCM of $1.8 million and $0.5 million, respectively. GIROXX In January 2020, the Company’s wholly owned subsidiary, StoneX Financial Ltd, executed a stock purchase agreement to acquire 100% of GIROXX based in Germany. Through its digital platform, GIROXX provides online payment and foreign exchange hedging services to small and medium sized enterprises in Germany, Austria, and Switzerland. The Company offers a wide range of financial services including advisory and execution services in commodities, which will be offered to GIROXX’s institutional client base. This purchase completes a series of acquisitions and restructurings to ensure that all clients of the Company are secure with their continuity of service and market access following Brexit. The closing of the transaction was conditional upon the approval of financial services regulators in Germany, which was obtained during the period with the transaction closing on May 1, 2020. The cash purchase price for the acquisition of GIROXX was $4.4 million. The preliminary allocation of the cash purchase price to the fair value of tangible assets acquired and liabilities assumed resulted in the recognition of cash and cash equivalents of $6.5 million, property and equipment of $0.1 million, accounts payables and other accrued liabilities of $0.6 million, and payables to clients of $5.8 million as of the acquisition date. The Company acquired certain identifiable intangible assets in connection with the acquisition of GIROXX, primarily related to a business license permitting the Company to facilitate payment transactions in the European Union and certain proprietary developed software. The Company has preliminarily allocated $0.4 million and $1.5 million of the excess purchase price over net tangible assets acquired to the business license and proprietary developed software, respectively. The remaining excess purchase price over the net tangible assets acquired of $2.3 million has preliminary been allocated to goodwill. The Company believes the preliminary allocation to goodwill represents the synergies that can be realized from integrating the acquired business into its existing Global Payments reportable segment. The Company is in the process of gathering the information necessary to complete a valuation analysis of the intangible assets acquired. Once the valuation analysis is complete, the Company will record measurement period adjustments to reflect the final determination of the fair value of the identifiable intangible assets acquired with any remaining excess consideration allocated to goodwill. The acquired business license has been assigned an indefinite life and the proprietary developed software has been preliminarily assigned a useful life of 3 years. GIROXX’s results of operations and cash flows have been included in the Company’s consolidated financial statements for the period subsequent to May 1, 2020. For the year ended September 30, 2020, the Company’s results include total revenues and net loss from GIROXX of $0.5 million and $0.6 million, respectively. The acquired business has been assigned to the Company’s Global Payments reportable segment. Asset Acquisitions Quest Capital In August 2019, the Company’s subsidiary, SA Stone Wealth Management, executed an asset purchase agreement to acquire certain client accounts of Quest Capital Strategies, Inc. The asset purchase agreement was subject to FINRA approval and other conditions to closing. FINRA approval was obtained and the other conditions to closing were fulfilled and the closing of the transaction occurred on December 9, 2019. The cash purchase price for the acquired client accounts was equal to $1.7 million. This transaction was accounted for as an asset acquisition at cost. The cash purchase price was allocated to the fair value of the client lists and relationships obtained and has been assigned, and will be amortized, over a useful life of seven years. Acquisitions in Fiscal 2019 Carl Kliem S.A. On November 30, 2018, the Company acquired the entire issued and outstanding share capital of Carl Kliem S.A., an independent interdealer broker based in Luxembourg, which provides foreign exchange, interest rate and fixed income products to institutional clients across the European Union (“E.U.”). Carl Kliem S.A. employs approximately 40 people and has more than 400 active institutional clients. This acquisition provides the Company with access to additional European institutional clients that can benefit from the Company’s full suite of financial services and a E.U.-based entity in anticipation of the U.K.’s planned exit from the E.U. The purchase price was $2.1 million of cash consideration, and was equal to the net tangible book value on the closing date less restructuring costs. The Company subsequently renamed Carl Kliem S.A. to StoneX Financial Europe S.A. The final purchase price allocation resulted in cash and cash equivalents of $1.7 million, receivables from clients of $1.1 million, property and equipment of $0.1 million, income tax receivables of $0.1 million, accounts payable and other accrued liabilities of $0.6 million, and payable to broker-dealers, clearing organizations, and counterparties of $0.2 million. The net fair value of the assets acquired exceeded the aggregate cash purchase price; accordingly, the Company recorded a bargain purchase gain of $0.1 million during the year ended September 30, 2019, which is presented within ‘Gain on acquisitions and other gains’ in the consolidated income statement. The business activities of INTL FCStone Europe S.A. have been included within the Company’s Institutional reportable segment. The Company’s consolidated income statement for the year ended September 30, 2019 includes operating revenues and a net loss of $4.2 million and $2.3 million, respectively, for the post-acquisition results of the acquired business. GMP Securities LLC On January 14, 2019 the Company acquired 100% of the U.S.-based broker-dealer GMP Securities LLC (“GMP”), formerly known as Miller Tabak Securities, LLC, an independent, SEC-registered broker-dealer and Financial Industry Regulatory Authority, Inc. (“FINRA”) member. GMP has an institutional fixed-income trading business which deals in high yield, convertible and emerging market debt and makes markets in certain equity securities. This transaction also involved the purchase of GMP’s U.S.-based parent. This acquisition allows the Company to expand its fixed income product offerings to clients and adds new institutional clients who can benefit from the Company’s full suite of financial services. The purchase price was $8.2 million of cash consideration was equal to the final net tangible book value determined as of the acquisition date less $2.0 million. The net fair value of the assets acquired exceeded the aggregate cash purchase price, and accordingly the Company recorded a bargain purchase gain of $5.4 million during the year ended September 30, 2019, which is presented within ‘Gain on acquisitions and other gains’ in the consolidated income statement. The Company believes the transaction resulted in a bargain purchase gain due to the Company’s ability to incorporate GMP’s business activities into its existing business structure, and its ability to utilize certain deferred tax assets, including net operating loss carryforwards, and other assets while operating the business that may not have been likely to be realized by the seller nor was contemplated in the purchase price. On May 1, 2019, GMP was merged into the Company’s wholly owned regulated U.S. subsidiary, StoneX Financial. The Company’s consolidated income statement includes the post-acquisition results, which include operating revenues and a net loss before tax of $8.2 million and $2.1 million, respectively, for the year ended September 30, 2019. The acquired businesses are included within the Company’s Institutional reportable segment. The following represents the final allocation of the purchase price to the fair value of identifiable assets acquired and liabilities assumed as of the acquisition date (in millions): Fair Value Cash and cash equivalents $ 1.1 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties (1) 7.7 Financial instruments owned, at fair value (2) 7.1 Deferred income taxes 2.7 Property and equipment 0.7 Other assets 0.7 Total fair value of assets acquired 20.0 Accounts payable and other accrued liabilities 1.9 Payable to broker-dealers, clearing organizations, and counterparties 0.1 Financial instruments sold, not yet purchased, at fair value (2) 4.4 Total fair value of liabilities assumed 6.4 Fair value of net assets acquired 13.6 Purchase price 8.2 Bargain purchase gain $ 5.4 (1) Amount represents the contractual amount of deposits and receivables due from the clearing organization for trading activity as of the acquisition date. (2) Financial instruments owned and sold, not yet purchased, at fair value primarily includes equity securities and high yield, convertible and emerging market fixed income securities. Equity securities have been included within Level 1 of the fair value hierarchy and fixed income securities have been included in Level 2 of the fair value hierarchy as disclosed in Note 4. Coininvest GmbH and European Precious Metal Trading GmbH On April 1, 2019, the Company’s subsidiary StoneX (Netherlands) B.V. acquired 100% of the outstanding shares of Coininvest GmbH and European Precious Metal Trading GmbH. Through the websites coininvest.com and silver-to-go.com, Coininvest GmbH and European Precious Metal Trading GmbH are leading European online providers of gold, silver, platinum, and palladium products to retail investors, institutional investors, and financial advisors. The addition of Coininvest GmbH and European Precious Metal Trading GmbH to the Company’s global product suite expands its offering, providing clients the ability to purchase physical gold and other precious metals, in multiple forms, and in denominations of their choice, to add to their investment portfolios. The purchase price consisted of cash consideration of $22.0 million, including $11.2 million for the purchase of shareholders loans outstanding with the acquired entities. The cash consideration transferred exceeded the final fair value of the tangible net assets acquired on the closing date by $6.8 million. The Company acquired certain identifiable intangible assets, including website domain names and internally developed software. The Company has engaged a third-party valuation specialist to assist with the valuation of these acquired intangible assets. Based upon the final valuation analysis, the Company allocated $2.1 million and $2.5 million of the excess consideration over the final fair value of tangible net assets acquired on the closing date to the identifiable domain names and internally developed software, respectively. The remaining excess of $2.2 million was allocated to goodwill. The goodwill represents the synergies expected to be achieved by combining the acquired business with the Company’s existing precious metals offering and the acquired assembled workforce. The internally developed software was assigned to the Retail reportable segment and is being amortized over a useful life of 5 years. The useful life of the domain names was determined to be indefinite. The Company’s consolidated income statement includes the post-acquisition results, including operating revenues and a net loss before tax of $0.6 million and $0.3 million, respectively, for the year ended September 30, 2019. Operating revenues during the year ended September 30, 2019 include unrealized losses on derivatives held to manage the downside price risk of physical commodities inventory, which is valued at the lower of cost or net realizable value; therefore, inventory was not recorded above its cost basis. The acquired businesses are included within the Company’s Commercial 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 $ 2.0 Receivables from clients (1) 1.2 Receivable from affiliate 1.1 Income tax receivable 0.1 Physical commodities inventory 9.8 Deferred tax assets, net 0.2 Other assets 1.2 Total fair value of tangible assets acquired 15.6 Accounts payable and other accrued liabilities 0.2 Payables to clients 0.2 Total fair value of tangible liabilities assumed 0.4 Fair value of net tangible assets acquired 15.2 Purchase price 22.0 Excess purchase price over fair value of tangible net assets acquired $ 6.8 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Domain names $ 2.1 Internally developed software 2.5 Total excess purchase price allocated to identifiable intangible assets 4.6 Remaining excess allocated to goodwill $ 2.2 (1) Amount represents the contractual amount of receivables due from clients for trading activity, all of which was collected. Fillmore Advisors, LLC On September 1, 2019, the Company acquired 100% of the U.S.-based trading firm Fillmore Advisors, LLC (“Fillmore”). Fillmore is an independent, SEC-registered broker-dealer firm and FINRA member firm and a leading provider of outsourced trading solutions and operational consulting to institutional asset managers. The firm, headquartered in Park City, Utah, is composed of traders that specialize in global buy-side and sell-side experience. Institutional clients can benefit from Fillmore’s comprehensive product coverage offering for equities, equity-linked, foreign exchange, credit, rates, and commodities. Fillmore will become an extension of the newly established prime brokerage division of the Company’s Institutional reportable segment. The purchase price consists of $1.4 million of cash consideration and also includes a contingent earn-out with payments over the eight quarters following the acquisition. The contingent earn-out payments are variable in nature and equal to 50% of Segment Income, as defined in the SPA, for each quarterly period. The fair value of the contingent consideration was estimated at $1.8 million as of the closing date. See Note 5 for fair value measurement considerations. The Company acquired certain identifiable intangible assets related to Fillmore’s client base. Based upon the final valuation analysis, the Company has allocated $0.7 million of the excess consideration over the final fair value of tangible net assets acquired on the closing date to this intangible asset. The remaining excess of $1.9 million was allocated to goodwill. The goodwill represents the synergies expected to be achieved by combining the acquired business with the Company’s existing prime brokerage offering and the acquired assembled workforce. The client base intangible asset and goodwill were assigned to the Institutional reportable segment. The client base intangible asset will be amortized over a useful life of 5 years. 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 $ 0.2 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties 0.3 Receivables from clients, net (1) 0.2 Other assets 0.4 Total fair value of tangible assets acquired 1.1 Accounts payable and other accrued liabilities 0.5 Total fair value of tangible liabilities assumed 0.5 Fair value of net tangible assets acquired 0.6 Purchase price (2) 3.2 Excess purchase price over fair value of tangible net assets acquired $ 2.6 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Client relationships $ 0.7 Total excess purchase price allocated to identifiable intangible assets 0.7 Remaining excess allocated to goodwill $ 1.9 (1) Amount represents the contractual amount of receivables due from clients for trading activity, all of which was collected. (2) Includes the fair value of contingent consideration of $1.8 million. Acquisitions in Fiscal 2018 PayCommerce Financial Solutions, LLC On September 5, 2018, the Company acquired all of the outstanding membership interests of PayCommerce Financial Solutions, LLC (“PCFS”). Subsequent to the acquisition, the Company renamed PCFS to INTL Technology Services, LLC (“ITS”). ITS is a fully accredited Society for Worldwide Interbank Financial Telecommunication (“SWIFT”) Service Bureau provider. This acquisition enables the Company to act as a SWIFT Service Bureau for its 300-plus correspondent banking network, thus providing another important service for delivering local currency, cross-border payments to the developing world. The purchase price was approximately $3.8 million of cash consideration. The final purchase price allocation resulted in $0.7 million in receivables, $0.8 million in property, plant, and equipment, a $0.5 million equity investment related to a minority interest in the joint venture entity Akshay Financeware, Inc., and $2.2 million in liabilities assumed. Additionally, the Company acquired identifiable, definite-lived client relationship and client list assets that have been assigned a fair value of $1.3 million and a useful life of 5 years. The fair value of the consideration transferred exceeded the final fair value of identifiable assets acquired and liabilities assumed. The excess of the purchase consideration over the final fair value of net tangible and identifiable intangible assets acquired of $2.6 m

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive (Loss) Income Comprehensive income consists of net income and other gains and losses affecting stockholders’ equity that, under U.S. GAAP, are excluded from net income. Other comprehensive loss includes net actuarial losses from defined benefit pension plans and losses on foreign currency translations. The following table summarizes the changes in accumulated other comprehensive loss for the year ended September 30, 2020. (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2019 $ (31.5) $ (3.3) $ (34.8) ASU 2018-02 cumulative transition adjustment — (0.7) (0.7) Adjusted Balances as of September 30, 2019 (31.5) (4.0) (35.5) Other comprehensive loss (4.5) (0.2) (4.7) Amounts reclassified from AOCI, net of tax — 0.1 0.1 Other comprehensive loss (4.5) (0.1) (4.6) Balances as of September 30, 2020 $ (36.0) $ (4.1) $ (40.1)

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Segment and Geographic Information	Segment and Geographic Information During the three months ended September 30, 2020, the Company completed its acquisition of Gain Capital Group Inc. (“Gain”), which it views as a significant acquisition and which triggered a reassessment of the financial information reviewed by its executive management team, which is considered our Chief Operating Decision Maker, on a regular basis, and which is used to make resource allocation decisions. The acquisition of Gain added a significant amount of incremental business from a new client type – retail. Prior to the acquisition, Gain was a publicly traded corporation in the United States, and reported its performance along two reportable segments: retail and futures, in its periodic reporting with the SEC. The Company has existing businesses with activities similar to Gain’s futures business. Gain’s retail business however, represents a fundamental change in the Company’s business strategy. In light of this fundamental change and reassessment described above, the Company has modified the operating segments it uses to evaluate its performance. Accordingly, its operating segments are now based primarily on the nature of the clients we serve (commercial, institutional, and retail), and a fourth operating segment, its global payments business. The Company manages its business in this manner due to its large global footprint, in which it has more than 2,900 employees allowing it to serve clients in more than 180 countries. Following the acquisition of Gain, the Company’s business activities are managed as operating segments and organized into reportable segments as follows: • Commercial • Institutional • Retail • Global Payments All segment information has been revised to reflect the operating segment reorganization retroactive to October 1, 2017. Commercial The Company offers commercial clients a comprehensive array of products and services, including risk management and hedging services, execution and clearing of exchange-traded and OTC products, voice brokerage, market intelligence and physical trading as well as commodity financing and logistics services. The ability to provide these high-value-added products and services, differentiates the Company from its competitors and maximizes the opportunity to retain clients. Institutional The Company provides institutional clients with a complete suite of equity trading services to help them find liquidity with best execution, consistent liquidity across a robust array of fixed income products, competitive and efficient clearing and execution in all major futures and securities exchanges globally as well as prime brokerage in equities and major foreign currency pairs and swap transactions. In addition, the Company originates, structures and place debt instruments in the international and domestic capital markets. These instruments include asset-backed securities (primarily in Argentina) and domestic municipal securities. Retail The Company provides retail clients around the world access to over 15,000 global financial markets, including spot foreign exchange ("forex"), both financial trading and physical investment in precious metals, as well as contracts for difference (“CFDs”), which are investment products with returns linked to the performance of underlying assets. In addition, its independent wealth management business offers a comprehensive product suite to retail investors in the United States. Global Payments The Company provides customized foreign exchange and treasury services to banks and commercial businesses as well as charities and non-governmental organizations and government organizations. The Company provides transparent pricing and offers payments services in more than 170 countries and 140 currencies, which it believes is more than any other payments solution provider. ******** The total revenues reported combine gross revenues from physical contracts for subsidiaries that are not broker-dealers and net revenues for all other businesses. In order to reflect the way that the Company’s management views the results, the table below also reflects the segment contribution to ‘operating revenues’, which is shown on the face of the consolidated income statements and which is calculated by deducting physical commodities cost of sales from total revenues. Segment data includes the profitability measure of net contribution by segment. Net contribution is one of the key measures used by management to assess the performance of each segment and for decisions regarding the allocation of the Company’s resources. Net contribution is calculated as revenue less direct cost of sales, transaction-based clearing expenses, variable compensation, introducing broker commissions, and interest expense. Variable compensation paid to risk management consultants/traders generally represents a fixed percentage of revenues generated, and in some cases, revenues generated less transaction-based clearing expenses, base salaries and an overhead allocation. Segment data also includes segment income which is calculated as net contribution less non-variable direct expenses of the segment. These non-variable direct expenses include trader base compensation and benefits, operational employee compensation and benefits, communication and data services, business development, professional fees, bad debt expense and other direct expenses. Inter-segment revenues, expenses, receivables and payables are eliminated upon consolidation, except revenues and expenses related to foreign currency transactions undertaken on an arm’s length basis by the foreign exchange trading business for the securities business. The foreign exchange trading business competes for this business as it does any other business. If its rates are not competitive, the securities businesses buy or sell their foreign currency through other market participants. Total revenues, operating revenues and net operating revenues shown as “Corporate Unallocated” primarily consist of interest income from its centralized corporate treasury function. In the normal course of operations, the Company operates a centralized corporate treasury function in which it may sweep excess cash from certain subsidiaries, where permitted within regulatory limitations, in exchange for a short-term interest bearing intercompany payable, or provide excess cash to subsidiaries in exchange for a short-term interest bearing intercompany receivable in lieu of the subsidiary borrowing on external credit facilities. The intercompany receivables and payables are eliminated during consolidation; however, this practice may impact reported total assets between segments. Net costs not allocated to operating segments include costs and expenses of certain shared services such as information technology, accounting and treasury, credit and risk, legal and compliance, and human resources and other activities. Information for the reportable segments is shown in accordance with the Segment Reporting Topic of the ASC as follows Year Ended September 30, (in millions) 2020 2019 2018 Total revenues: Commercial $ 52,970.1 $ 32,125.4 $ 27,018.7 Institutional 624.1 515.0 427.1 Retail 432.7 148.1 73.3 Global Payments 117.4 112.8 99.2 Corporate Unallocated 14.6 20.8 23.9 Eliminations (19.3) (25.1) (19.5) Total $ 54,139.6 $ 32,897.0 $ 27,622.7 Operating revenues: Commercial $ 431.5 $ 404.4 $ 371.8 Institutional 624.1 515.0 427.1 Retail 140.0 78.2 73.3 Global Payments 117.4 112.8 99.2 Corporate Unallocated 14.6 20.8 23.9 Eliminations (19.3) (25.1) (19.5) Total $ 1,308.3 $ 1,106.1 $ 975.8 Net operating revenues (loss): Commercial $ 353.4 $ 321.2 $ 299.4 Institutional 363.8 220.1 176.3 Retail 63.8 15.7 12.7 Global Payments 111.5 107.0 93.5 Corporate Unallocated (24.5) (10.8) (0.3) Total $ 868.0 $ 653.2 $ 581.6 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial $ 242.2 $ 224.6 $ 210.0 Institutional 248.9 157.0 135.6 Retail 58.8 14.6 11.8 Global Payments 89.6 86.6 75.0 Total $ 639.5 $ 482.8 $ 432.4 Segment income (loss): (Net contribution less non-variable direct segment costs) Commercial (1) $ 141.9 $ 144.6 $ 118.3 Institutional 152.9 88.6 78.2 Retail 31.7 6.4 5.6 Global Payments 68.6 66.1 59.8 Total $ 395.1 $ 305.7 $ 261.9 Reconciliation of segment income to income before tax: Segment income $ 395.1 $ 305.7 $ 261.9 Net costs not allocated to operating segments (270.3) (200.2) (162.4) Gain on acquisitions and other gains 81.9 5.5 2.0 Income before tax $ 206.7 $ 111.0 $ 101.5 (1) During fiscal 2019, the Company recorded recoveries on the bad debt on physical coal of $12.4 million. During fiscal 2018, the Company recorded charges to earnings of $1.0 million to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business with a coal supplier, as further discussed in Note 19. (in millions) As of September 30, 2020 As of September 30, 2019 As of September 30, 2018 Total assets: Commercial $ 2,753.6 $ 2,386.4 $ 2,349.5 Institutional 8,740.8 7,111.2 5,168.1 Retail 1,245.9 12.4 — Global Payments 315.9 278.2 206.6 Corporate unallocated 418.7 147.9 100.5 Total $ 13,474.9 $ 9,936.1 $ 7,824.7 Information regarding revenues and operating revenues for the years ended September 30, 2020, 2019, and 2018, and information regarding long-lived assets (defined as property, equipment, leasehold improvements and software) as of September 30, 2020, 2019, and 2018 in geographic areas were as follows: Year Ended September 30, (in millions) 2020 2019 2018 Total revenues: United States $ 2,223.3 $ 1,947.6 $ 1,587.6 Europe 532.6 280.2 189.6 South America 58.9 56.5 59.5 Middle East and Asia 51,317.1 30,606.9 25,781.4 Other 7.7 5.8 4.6 Total $ 54,139.6 $ 32,897.0 $ 27,622.7 Operating revenues: United States $ 928.3 $ 799.4 $ 695.3 Europe 237.9 209.6 189.0 South America 58.9 56.5 58.0 Middle East and Asia 75.5 34.8 28.9 Other 7.7 5.8 4.6 Total $ 1,308.3 $ 1,106.1 $ 975.8 (in millions) As of September 30, 2020 As of September 30, 2019 As of September 30, 2018 Long-lived assets, as defined: United States $ 55.4 $ 33.9 $ 33.0 Europe 3.1 6.6 6.8 South America 2.1 2.1 1.4 Middle East and Asia 1.3 1.0 1.2 Other 0.2 0.3 — Total $ 62.1 $ 43.9 $ 42.4

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	Quarterly Financial Information (Unaudited) The Company has set forth certain quarterly unaudited financial data for the past two years in the tables below: For the 2020 Fiscal Quarter Ended (in millions, except per share amounts) September 30 June 30 March 31 December 31 Total revenues $ 14,284.9 $ 8,243.4 $ 20,366.3 $ 11,245.0 Cost of sales of physical commodities 13,942.8 7,920.8 19,999.5 10,968.2 Operating revenues 342.1 322.6 366.8 276.8 Transaction-based clearing expenses 57.1 55.3 63.8 46.3 Introducing broker commissions 34.0 24.0 29.6 26.2 Interest expense 10.0 11.5 27.8 31.1 Interest expense on corporate funding 14.8 3.9 2.2 2.7 Net operating revenues 226.2 227.9 243.4 170.5 Compensation and benefits 145.5 132.5 136.7 104.0 Bad debts, net of recoveries and impairment 12.5 1.8 4.4 — Other expenses 70.1 44.6 46.2 44.9 Total compensation and other expenses 228.1 178.9 187.3 148.9 Gain on acquisitions (1) 81.8 — — 0.1 Income before tax 79.9 49.0 56.1 21.7 Income tax expense 2.5 12.4 16.8 5.4 Net income $ 77.4 $ 36.6 $ 39.3 $ 16.3 Net basic earnings per share $ 4.00 $ 1.90 $ 2.03 $ 0.85 Net diluted earnings per share $ 3.90 $ 1.87 $ 2.00 $ 0.84 For the 2019 Fiscal Quarter Ended (in millions, except per share amounts) September 30, June 30, March 31, December 31, Total revenues $ 11,279.6 $ 7,873.0 $ 7,192.2 $ 6,552.2 Cost of sales of physical commodities 10,992.7 7,589.6 6,921.1 6,287.5 Operating revenues 286.9 283.4 271.1 264.7 Transaction-based clearing expenses 45.0 45.7 42.7 50.1 Introducing broker commissions 27.7 29.6 24.8 32.6 Interest expense 37.2 39.4 35.2 30.2 Interest expense on corporate funding 3.6 3.1 3.2 2.8 Net operating revenues 173.4 165.6 165.2 149.0 Compensation and benefits 105.2 100.9 97.9 89.1 Bad debts, net of recoveries 1.0 0.5 0.7 0.3 Recovery of bad debt on physical coal (2) (10.0) — — (2.4) Other expenses 43.2 42.6 41.1 37.6 Total compensation and other expenses 139.4 144.0 139.7 124.6 Gain on acquisitions (3) 0.1 — 5.4 — Income before tax 34.1 21.6 30.9 24.4 Income tax expense 6.9 5.3 7.5 6.2 Net income (loss) $ 27.2 $ 16.3 $ 23.4 $ 18.2 Net basic (loss) earnings per share $ 1.42 $ 0.85 $ 1.23 $ 0.96 Net diluted (loss) earnings per share $ 1.40 $ 0.84 $ 1.21 $ 0.94 (1) During the fourth quarter ended September 30, 2020, the Company recorded a bargain purchase gain of $81.8 million related to the acquisition of Gain. See Note 21 for additional information. (2) During the fourth quarter ended September 30, 2019, the Company recorded a recovery on the bad debt on physical coal received through an insurance policy claim related to the matter. See Note 19 for additional information.

Condensed Financial Information

Condensed Financial Information of Parent Company Only Disclosure	12 Months Ended
	Sep. 30, 2020
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure	Schedule I StoneX Group Inc. Condensed Balance Sheets Parent Company Only (in millions) September 30, 2020 September 30, 2019 ASSETS Cash and cash equivalents $ 7.4 $ 2.0 Receivable from subsidiaries, net — 17.6 Receivable from clients 0.4 0.5 Notes receivable, net 1.7 2.8 Income taxes receivable 46.2 15.7 Investment in subsidiaries (1) 834.0 399.4 Deferred income taxes, net 4.3 8.2 Property and equipment, net 42.1 26.9 Operating right of use assets 69.0 — Other assets 20.1 13.0 Total assets $ 1,025.2 $ 486.1 LIABILITIES AND EQUITY Liabilities: Accounts payable and other accrued liabilities $ 73.4 $ 29.4 Operating lease liabilities 85.4 — Payable to clients 0.3 0.3 Payable to subsidiaries, net 96.5 — Payable to lenders under loans 23.0 70.4 Senior secured borrowings, net 515.1 167.6 Financial instruments sold, not yet purchased, at fair value 1.1 84.5 Total liabilities 794.8 352.2 Equity: StoneX Group Inc. (Parent Company Only) stockholders’ equity: Preferred stock, $0.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding — — Common stock, $0.01 par value. Authorized 30,000,000 shares; 21,798,551 issued and 19,376,594 outstanding at September 30, 2020 and 21,297,317 issued and 19,075,360 outstanding at September 30, 2019 0.2 0.2 Common stock in treasury, at cost - 2,421,957 shares at September 30, 2020 and 2,221,957 shares at September 30, 2019 (57.6) (50.1) Additional paid-in capital 292.6 276.8 Retained earnings (1) (4.8) (93.0) Total StoneX Group Inc. (Parent Company Only) stockholders’ equity 230.4 133.9 Total liabilities and equity $ 1,025.2 $ 486.1 (1) Within the Condensed Balance Sheets and Condensed Statements of Operations of StoneX Group Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, investment in subsidiaries and retained earnings would each increase by $577.2 million as of September 30, 2020, respectively, and $495.1 million, as of September 30, 2019, respectively. Schedule I StoneX Group Inc. Condensed Statements of Operations Parent Company Only Year Ended September 30, (in millions) 2020 2019 2018 Revenues: Management fees from affiliates $ 45.1 $ 43.2 $ 40.4 Trading losses, net 0.6 — — Consulting fees 0.3 0.1 — Interest income 2.4 1.5 2.3 Dividend income from subsidiaries (2) 111.8 85.7 41.9 Total revenues 160.2 130.5 84.6 Interest expense 30.0 19.7 15.7 Net revenues 130.2 110.8 68.9 Non-interest expenses: Compensation and benefits 88.0 79.7 73.0 Clearing and related expenses 0.3 0.9 1.1 Trade systems and market information 3.9 6.4 5.8 Occupancy and equipment rental 3.8 3.4 2.6 Professional fees 12.9 7.3 6.7 Travel and business development 1.7 2.9 2.6 Non-trading technology and support 19.8 12.5 9.1 Depreciation and amortization 6.7 5.2 4.8 Communications 0.7 0.8 0.9 Impairment 2.5 — — Management services fees to affiliates 2.3 0.5 — Other 10.8 5.8 6.9 Total non-interest expenses 153.4 125.4 113.5 Gain on acquisitions 81.9 5.3 — Income (loss) before tax 58.7 (9.3) (44.6) Income tax expense 29.5 24.6 7.4 Net income (loss) $ 88.2 $ 15.3 $ (37.2) (2) W ithin the Condensed Balance Sheets and Condensed Statements of Operations of StoneX Group Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, revenues would also include income from investment in subsidiaries of $81.4 million, $69.8 million, and $92.7 million for the years ended September 30, 2020, 2019, and 2018, respectively. Schedule I StoneX Group Inc. Condensed Statements of Cash Flows Parent Company Only Year Ended September 30, (in millions) 2020 2019 2018 Cash flows from operating activities: Net income (loss) $ 88.2 $ 15.3 $ (37.2) Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Depreciation and amortization 6.7 5.2 4.8 Amortization of operating right of use assets 4.4 — — Deferred income taxes — 0.6 18.0 Amortization and extinguishment of debt issuance costs 6.1 1.2 0.7 Amortization of share-based compensation expense 9.2 7.1 6.1 Impairment 2.5 — — Gain on acquisition (81.9) (5.4) — Changes in operating assets and liabilities: Due to/from subsidiaries 149.3 8.3 (69.4) Receivables from clients, net 0.1 (0.5) — Notes receivable, net 1.1 (1.0) 2.9 Income taxes receivable (48.4) (0.8) (6.6) Financial instruments owned, at fair value — 4.4 (4.4) Other assets (7.7) (4.4) (0.7) Accounts payable and other accrued liabilities 24.0 4.6 8.6 Operating lease liabilities (2.8) — — Payable to clients — (1.4) (0.3) Financial instruments sold, not yet purchased, at fair value (83.4) 25.2 34.0 Net cash provided by (used in) operating activities 67.4 58.4 (43.5) Cash flows from investing activities: Capital contribution in affiliates (251.9) (75.8) (4.5) Purchase of property and equipment (10.2) (6.2) (5.9) Net cash used in investing activities (262.1) (82.0) (10.4) Cash flows from financing activities: Proceeds from revolving credit facility Net change in lenders under loans (47.0) (138.2) 58.2 Payments of notes payable (0.4) (0.8) (0.8) Proceeds from issuance of senior secured term loan 21.5 175.0 — Repayments of senior secured term loan (9.8) (6.6) — Proceeds from issuance of senior secured notes 344.8 — — Repayments of senior secured notes (92.1) — — Deferred payments on acquisitions (0.9) — (5.5) Share repurchase (7.5) (3.8) — Debt issuance costs (14.0) (3.0) — Exercise of stock options 5.5 1.2 2.6 Withholding taxes on stock option exercises — — (0.8) Net cash provided by financing activities 200.1 23.8 53.7 Net increase (decrease) in cash and cash equivalents 5.4 0.2 (0.2) Cash and cash equivalents at beginning of period 2.0 1.8 2.0 Cash and cash equivalents at end of period $ 7.4 $ 2.0 $ 1.8 Supplemental disclosure of cash flow information: Cash paid for interest $ 15.3 $ 18.9 $ 15.0 Income taxes (received) paid, net of cash refunds $ (4.3) $ (23.9) $ (18.4) Supplemental disclosure of non-cash investing and financing activities: Additional consideration payable related to acquisitions $ 21.6 $ 1.8 $ —

Description of Business and S_2

Description of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of StoneX Group Inc. and all other entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. Unless otherwise stated herein, all references to fiscal 2020, fiscal 2019, and fiscal 2018 refer to the Company’s fiscal years ended September 30. In the consolidated income statements, the total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. The subtotal ‘operating revenues’ in the consolidated income statements is calculated by deducting physical commodities cost of sales from total revenues. The subtotal ‘net operating revenues’ in the consolidated income statements is calculated as operating revenues less transaction-based clearing expenses, introducing broker commissions and interest expense. Transaction-based clearing expenses represent variable expenses paid to executing brokers, exchanges, clearing organizations and banks in relation to transactional volumes. Introducing broker commissions include commission paid to non-employee third parties that have introduced clients to the Company. Net operating revenues represent revenues available to pay variable compensation to risk management consultants and traders and direct non-variable expenses, as well as variable and non-variable expenses of operational and administrative employees.
Consolidation	The accompanying consolidated financial statements include the accounts of StoneX Group 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	Unless otherwise stated herein, all references to fiscal 2020, fiscal 2019, and fiscal 2018 refer to the Company’s fiscal years ended September 30.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurements for financial instruments, revenue recognition, the provision for probable losses from bad debts, valuation of inventories, and incomes taxes and contingencies. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. The Company reviews all significant estimates affecting the financial statements on a recurring basis and records the effect of any necessary adjustments prior to their issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates.
Reclassifications	Reclassifications During the year ended September 30, 2020, the Company reclassified certain selling and marketing related costs in connection with the acquisition of Gain Capital Holdings, Inc. (“Gain”). In performing this reclassification, the Company has made retrospective adjustments to the consolidated income statements for the years ended September 30, 2019 and 2018. For the years ended September 30, 2019 and 2018, selling and marketing related costs of $5.2 million and $6.2 million, were reclassified from ‘Other’ expense to ‘Selling and marketing’ expense. During the year ended September 30, 2019, the Company reclassified certain brokerage related revenues for which the Company earns commissions on trading activity in the capacity of an agent. In performing this reclassification, the Company has made a retrospective adjustment to the consolidated income statement for the year ended September 30, 2018. For the year ended September 30, 2018, brokerage related revenue of $35.0 million, was reclassified from ‘principal gains, net’ to ‘commissions and clearing fees’. Additionally, the Company has changed the name of the line item ‘trading gains, net’ to ‘principal gains, net’ on the consolidated income statement 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.
Foreign Currency Translation	Foreign Currency Translation The Company’s consolidated financial statements are reported in U.S. dollars. The Company’s foreign subsidiaries maintain their records either in U.S. dollars or in certain instances the currency of the country in which they operate. The method of translating local currency financial information into U.S. dollars depends on whether the economy in which the foreign subsidiary operates has been designated as highly inflationary or not. Economies with a three-year cumulative inflation rate of more than 100% are considered highly inflationary. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expense are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in earnings. Foreign subsidiaries that operate in highly inflationary countries use the U.S. dollar as their functional currency. Local currency monetary assets and liabilities are remeasured into U.S. dollars using rates of exchange as of each balance sheet date, with remeasurement adjustments and other transaction gains and losses recognized in earnings. Nonmonetary assets and liabilities do not fluctuate with changes in the local currency exchange rates to the dollar as the translated amounts for nonmonetary assets and liabilities at the end of the accounting period in which the economy becomes highly inflationary becomes the accounting basis for those assets and liabilities in the period of change and subsequent periods. Revenues and expenses are translated at rates of exchange in effect during the year. The Company operates asset management and debt trading businesses in Argentina through various wholly-owned subsidiaries. Operating revenues from the Argentinean subsidiaries represented approximately 2% of the consolidated operating revenues for the year ended September 30, 2020. The operating environment in Argentina continues to present business challenges, including ongoing devaluation of the Argentine peso and significant inflation. For the year ended September 30, 2018, the Argentine peso declined approximately 139% (from 17.3 to 41.3 pesos to the U.S. dollar). Based upon inflationary data published by the International Practices Task Force of the Center for Audit Quality, the economy of Argentina became highly inflationary during the three months ended June 30, 2018.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers cash held at banks and all highly liquid investments not held for trading purposes, with original or acquired maturities of 90 days or less, including certificates of deposit and money market mutual funds, to be cash and cash equivalents. Cash and cash equivalents consists of cash, certificates of deposit, and money market mutual funds not deposited with or pledged to clearing organizations, broker-dealers, clearing organizations or counterparties, or segregated under federal or other regulations. Certificates of deposit are stated at cost plus accrued interest, which approximates fair value, and may be withdrawn at any time at the discretion of the Company without penalty. Money market mutual funds are stated at their net asset value.
Cash, Securities and Other Assets Segregated under Federal and other Regulations	Cash, Securities and Other Assets Segregated under Federal and other Regulations Pursuant to requirements of the Commodity Exchange Act and Commission Regulation 30.7 of the U.S. Commodity Futures Trading Commission (“CFTC”) in the U.S., the Markets in Financial Instruments Implementing Directive 2006/73/EC underpinning the Client Asset (“CASS”) rules in the Financial Services Authority (“FSA”) handbook in the United Kingdom (“U.K.”), and the Securities & Futures Act (“SFA”) in Singapore, funds deposited by clients relating to futures and options on futures contracts in regulated commodities must be carried in separate accounts which are designated as segregated or secured client accounts. Additionally, in accordance with Rule 15c3-3 of the Securities Exchange Act of 1934 (“Rule 15c3-3”), the Company maintains separate accounts for the exclusive benefit of securities clients and proprietary accounts of broker dealers (“PABs”). Rule 15c3-3 requires the Company to maintain special reserve bank accounts (“SRBAs”) for the exclusive benefit of securities clients and PABs. The deposits in segregated client accounts and SRBAs are not commingled with the funds of the Company. Under the FSA’s rules, certain categories of clients may choose to opt-out of segregation.
Collateralized Transactions	Collateralized Transactions The Company enters into securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed transactions, and securities loaned transactions primarily to fund principal debt trading, acquire securities to cover short positions, acquire securities for settlement, or meet counterparty needs under matched-booked trading strategies.
Deposits with and Receivables from Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties	Deposits with and Receivables from Broker-dealers, Clearing Organizations and Counterparties, and Payables to Broker-dealers, Clearing Organizations and Counterparties As required by regulations of the CFTC, FSA, and Monetary Authority of Singapore (“MAS”), client funds received to margin, guarantee, and/or secure commodity futures and futures on options as well as retail foreign exchange transactions are segregated and accounted for separately from the general assets of the Company. Deposits with broker-dealers, clearing organizations, and counterparties pertain primarily to deposits made to satisfy margin requirements on client and proprietary open futures and options on futures positions and to satisfy the requirements set by clearing exchanges for clearing membership. The Company also pledges margin deposits with various counterparties for over-the-counter (“OTC”) derivative contracts, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. The Company also deposits cash margin with various securities clearing organizations as an ongoing condition of the securities clearing relationships, and these deposits are also included in deposits with broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties are reported gross, except where a right of offset exists. As of September 30, 2020 and September 30, 2019, the Company had cash and cash equivalents on deposit with or pledged to broker-dealers, clearing organizations, and counterparties of approximately 1.6 billion. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes guaranty deposits with clearing exchanges. The guaranty deposits are held by the clearing exchanges for use in potential default situations by one or more members of the clearing exchanges. The guaranty deposits may be applied to the Company’s obligations to the clearing exchange, or to the clearing exchange’s obligations to unrelated parties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include securities pledged to clearing exchanges. These securities are either pledged to the Company by its clients or represent investments of client funds. It is the Company’s practice to include client-owned securities on its consolidated balance sheets, as the rights to those securities have been transferred to the Company under the terms of the futures trading agreements. Securities pledged primarily include U.S. Treasury obligations, foreign government obligations, and certain exchange-traded funds (“ETFs”). Securities that are not client-owned, and represent an investment of client funds, are adjusted to fair value with associated changes in unrealized gains or losses recorded in ‘interest income’ in the consolidated income statements. For client-owned securities, the change in fair value is offset against the payable to clients with no impact recognized in the consolidated income statements. The fair value of these securities included within deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $1,949.3 million and $603.8 million as of September 30, 2020 and September 30, 2019, respectively. Management has considered guidance required by ASC 860, Transfers and Servicing as it relates to securities pledged by clients to margin their futures and options on futures trading accounts. Based on a review of the agreements with the client, management believes the transferor surrenders control over those assets because: (a) the transferred assets have been isolated from the transferor—put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (b) each transferee has the right to pledge or exchange the assets (or beneficial interests) it received, and no condition both constrains the transferee (or holder) from taking advantage of its right to pledge or exchange and provides more than a trivial benefit to the transferor and (c) the transferor does not maintain effective control over the transferred assets through either (1) an agreement that both entitles and obligates the transferor to repurchase or redeem them before their maturity or (2) the ability to unilaterally cause the holder to return specific assets, other than through a cleanup call. Under this guidance, the Company reflects the client collateral assets and corresponding liabilities in the Company’s consolidated balance sheets as of September 30, 2020 and September 30, 2019. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also includes amounts due from clearing exchanges for unrealized gains and losses associated with clients’ options on futures contracts. See discussion in the Financial Instruments section below for additional information on the Company’s accounting policies for derivative contracts. For client-owned derivative contracts, the fair value is offset against the payable to clients with no impact recognized on the consolidated income statements. The Company maintains client omnibus and proprietary accounts with other clearing organizations, and the equity balances in those accounts along with any margin cash or securities deposited with the clearing organizations are included in deposits with and receivables from broker-dealers, clearing organizations, and counterparties. Deposits with and receivables from broker-dealers, clearing organizations, and counterparties also include amounts due from or due to clearing exchanges for daily variation settlements on open futures and options on futures positions. The variation settlements due from or due to clearing exchanges are paid in cash on the following business day. Variation settlements equal the daily settlement of futures contracts and premiums on options on futures contracts. Receivables from broker-dealers and counterparties also include amounts receivable for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payables to broker-dealers and counterparties primarily include amounts payable for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivables from broker-dealers, clearing organizations and counterparties, and payables to broker-dealers, clearing organizations and counterparties also include amounts related to the value of registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days.
Receivable from and Payable to Clients	Receivable from and Payable to Clients Receivable from clients, net of the allowance for doubtful accounts, include the total of net deficits in individual exchange-traded futures and OTC derivative trading accounts carried by the Company. Client deficits arise from realized and unrealized trading losses on client futures, options on futures, swaps and forwards and amounts due on cash and margin transactions. Client deficit accounts are reported gross of client accounts that contain net credit or positive balances, except where a right of offset exists. Net deficits in individual futures exchange-traded and OTC derivative trading accounts include both secured and unsecured deficit balances due from clients as of the balance sheet date. Secured deficit amounts are backed by U.S. Treasury obligations and commodity warehouse receipts. These U.S Treasury obligations and commodity warehouse receipts are not netted against the secured deficit amounts, as the conditions for right of setoff have not been met. See note 13 for additional discussion of client deficit accounts originating in November 2018. Receivable from clients, net also includes the net amounts receivable from securities clients in connection with the settlement of regular-way cash securities, margin loans to clients, and client cash debits. It is the Company’s policy to report margin loans and payables that arise due to positive cash flows in the same client’s accounts on a net basis when the conditions for netting as specified in U.S. GAAP are met. Clients’ securities transactions cleared by the Company are recorded on a settlement date basis. Securities cleared by the Company and pledged to the Company as a condition of the custodial clearing arrangements are owned by the clients, including those that collateralize margin or other similar transactions, and are not reflected on the consolidated balance sheets as the Company does not have title to, or beneficial interests, in those assets. In the event of uncompleted transactions on settlement date, the Company records corresponding receivables and payables, respectively. The carrying value of the receivables and payables approximates fair value due to their short-term nature. Receivables from clients, net also include amounts receivable from non-broker-dealer clients for securities sold but not yet delivered by the Company on settlement date (“fails-to-deliver”) and net receivables arising from unsettled proprietary trades. Payable to clients represent the total of client accounts with credit or positive balances. Client accounts are used primarily in connection with exchange-traded and OTC commodity, foreign exchange, precious metals, and securities transactions and include gains and losses on open trades as well as securities and cash margin deposits made as required by the Company, the exchange-clearing organizations or other clearing organizations. Client accounts with credit or positive balances are reported gross of client deficit accounts, except where a right of offset exists. Payables to broker-dealers and counterparties also includes amounts payable to non-broker-dealer clients for securities purchased but not yet received by the Company on settlement date (“fails-to-receive”) and net payables arising from unsettled proprietary trades. Receivable from and payables to clients also include amounts related to the value of non-registered broker-dealer clients cross-currency payment transactions related to the Global Payments segment. These amounts arise due to a clearing period before the funds are received and payments are made, which usually is one to two business days. The future collectability of receivables from clients can be impacted by the Company’s collection efforts, the financial stability of its clients, and the general economic climate in which it operates. The Company evaluates accounts that it believes may become uncollectible on a specific identification basis, through reviewing daily margin deficit reports, the historical daily aging of the receivables, and by monitoring the financial strength of its clients. The Company may unilaterally close client trading positions in certain circumstances. In addition, to evaluate client margining and collateral requirements, client positions are stress tested regularly and monitored for excessive concentration levels relative to the overall market size. Furthermore, in certain instances, the Company is indemnified, and able to charge back, introducing broker-dealers for bad debts incurred by their clients. The Company generally charges off an outstanding receivable balance when all economic means of recovery have been exhausted. That determination considers information such as the occurrence of significant changes in the client’s financial position such that the client can no longer pay the obligation, or that the proceeds from collateral will not be sufficient to pay the balance.
Notes Receivable	Notes Receivable Accrual of commodity financing income on any note is discontinued when, in the opinion of management, there is reasonable doubt as to the timely collectability of interest or principal. Nonaccrual notes are returned to an accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely payment of principal and interest. The Company records a charge against earnings for notes receivable losses when management believes that the collection of outstanding principal is not probable.
Physcial Commodities Inventory	Physical Commodities Inventory Inventories of certain agricultural commodities are carried at net realizable value, which approximates fair value less disposal costs. The agricultural commodities inventories have reliable, readily determinable and realizable market prices, have relatively predictable and insignificant costs of disposal and are available for immediate delivery. Changes in the fair values of these agricultural commodities inventories are included as a component of ‘cost of sales of physical commodities’ in the consolidated income statements.
Property and Equipment	Property and Equipment Property and equipment is stated at cost, net of accumulated depreciation and amortization and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the estimated useful life of the improvement or the term of the lease, whichever is shorter. Expenditures that increase the value or productive capacity of assets are capitalized. When property and equipment are retired, sold, or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in earnings. The Company accounts for costs incurred to develop its trading platforms and related software in accordance with ASC 350-40, Internal-Use Software. ASC 350-40 requires that such technology be capitalized in the application development stages. Costs related to training, administration and non-value added maintenance are charged to expense as incurred. Capitalized software development costs are amortized over the useful life of the software, which the Company estimates at three years.
Goodwill and Identifiable Intangible Assets	Goodwill and Identifiable Intangible Assets Goodwill is the cost of acquired companies in excess of the fair value of identifiable net assets at the acquisition date. Goodwill is not subject to amortization, but rather is evaluated for impairment at least annually. The Company evaluates its goodwill for impairment at the fiscal year end (or more frequently if indicators of potential impairment exist) in accordance with ASC 350, Intangibles - Goodwill and Other. Goodwill impairment is determined by comparing the estimated fair value of a reporting unit with its respective carrying value. If the estimated fair value exceeds the carrying value, goodwill at the reporting unit level is not deemed to be impaired. However, if the estimated fair value is below carrying value, further analysis is required to determine the amount of the impairment. This further analysis involves assigning tangible assets and liabilities, identified intangible assets and goodwill to reporting units and comparing the fair value of each reporting unit to its carrying amount. In the course of the evaluation of the potential impairment of goodwill, the Company may perform either a qualitative or a quantitative assessment. The Company’s qualitative assessment of potential impairment may result in the determination that a quantitative impairment analysis is not necessary. Under this elective process, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads the Company to determine that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If after assessing the totality of events or circumstances, the Company determines it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then performing a quantitative analysis is not required. However, if the Company concludes otherwise, then the Company performs a quantitative impairment analysis. If the Company either chooses not to perform a qualitative assessment, or the Company chooses to perform a qualitative assessment but is unable to qualitatively conclude that no impairment has occurred, then the Company performs a quantitative evaluation. In the case of a quantitative assessment, the Company estimates the fair value of the reporting unit which the goodwill that is subject to the quantitative analysis is associated (generally defined as the businesses for which financial information is available and reviewed regularly by management) and compares it to the carrying value. If the estimated fair value of a reporting unit is less than its carrying value, the Company estimates the fair value of all assets and liabilities of the reporting unit, including goodwill. If the carrying value of the reporting unit’s goodwill is greater than the estimated fair value, an impairment charge is recognized for the excess. The fair value of the Company’s reporting units exceeded their respective carrying values under the first step of the quantitative assessment and no impairment charges were recorded for any of the periods presented. five
Financial Instruments Owned and Sold, Not Yet Purchased	Financial Instruments Owned and Sold, Not Yet Purchased Financial instruments owned and sold, not yet purchased, at fair value consist of financial instruments carried at fair value on a recurring basis or amounts that approximate fair value, with related realized and unrealized gains and losses recognized in current period earnings. Realized and unrealized gains and losses on financial instruments owned and sold, not yet purchased, are included in ‘principal gains, net’, ‘interest income’, ‘interest expense’, and ‘cost of sales of physical commodities’ in the consolidated income statements. The fair value of a financial instrument is the amount at which the instrument could be exchanged in a current transaction between willing parties, other than in a forced or liquidation sale. Financial instruments owned and sold, not yet purchased are comprised primarily of the financial instruments held by the Company’s broker-dealer subsidiaries and the Company’s OTC derivative swap dealer. Financial instruments owned and financial instruments sold, not yet purchased, includes trading securities that the Company holds as a principal. The Company has not classified any financial instruments owned or sold, not yet purchased, as available-for-sale or held-to-maturity. Financial instruments owned and sold, not yet purchased includes derivative instruments that the Company holds as a principal which are primarily transacted on an OTC basis. As a derivatives dealer, the Company utilizes derivative instruments to manage exposures to foreign currency, commodity price and interest rate risks for the Company and its clients. The Company’s objectives for holding derivatives include reducing, eliminating, and efficiently managing the economic impact of these exposures as effectively as possible. The Company’s derivative instruments also include forward purchase and sale commitments for the physical delivery of agricultural and energy related commodities in a future period. Contracts to purchase agricultural and energy commodities generally relate to the current or future crop year. Contracts for the sale of agricultural and energy commodities generally do not extend beyond one year. Derivative instruments are recognized as either assets or liabilities and are measured at fair value on a recurring basis. As the Company does not elect hedge accounting for any derivative instruments, realized and unrealized gains and losses from the change in fair value of derivative instruments are recognized immediately in current period earnings. Realized and unrealized gains and losses from the derivative instruments in which the Company acts as a dealer are included within ‘principal gains, net’ on the consolidated income statements. Realized and unrealized gains and losses on firm purchase and sale commitments are included within ‘cost of sales of physical commodities’ on the consolidated income statements. To reduce credit exposure on the derivative instruments for which the Company acts as a dealer, the Company may enter into a master netting arrangement that allows for settlement of all derivative transactions with each counterparty. In addition, the credit support annex that accompanies master netting arrangements allows parties to the master netting agreement to mitigate their credit risk by requiring the party which is out of the money to post collateral. The Company accepts collateral in the form of cash or other marketable securities. Where permitted, the Company elects to net-by-counterparty certain derivative instruments entered into under a legally enforceable master netting agreement and, therefore, the fair value of those derivative instruments are netted by counterparty in the consolidated balance sheets. As the Company elects to net-by-counterparty the fair value of such derivative instruments, the Company also nets-by-counterparty cash collateral exchanged as part of those derivative instruments. The Company also brokers foreign exchange forwards, options and cash, or spot, transactions between clients and external counterparties. A portion of the contracts are arranged on an offsetting basis, limiting the Company’s risk to performance of the two offsetting parties. The offsetting nature of the contracts eliminates the effects of market fluctuations on the Company’s operating results. Due to the Company’s role as a principal participating in both sides of these contracts, the amounts are presented gross on the consolidated balance sheets at their respective fair values, net of offsetting assets and liabilities. The Company holds proprietary positions in its foreign exchange line of business. On a limited basis, the Company’s foreign exchange trade desk will accept a client transaction and will offset that transaction with a similar but not identical position with a counterparty. These unmatched transactions are intended to be short-term in nature and are often conducted to facilitate the most effective transaction for the Company’s client. These spot and forward contracts are accounted for as free-standing derivatives and reported in the consolidated balance sheets at their fair values.
Exchange and Clearing Organization Memberships	Exchange and Clearing Organization Memberships The Company is required to hold certain exchange and clearing organization memberships and pledges them for clearing purposes, in order to provide the Company the right to process trades directly with the respective venues. Exchange memberships include seats on the Chicago Board of Trade (“CBOT”), the Minneapolis Grain Exchange, the New York Mercantile Exchange (“NYMEX”), the Commodity Exchange, Inc. (“COMEX”) Division of the New York Mercantile Exchange, Mercado de Valores de Buenos Aires S.A. (“MERVAL”), the Chicago Mercantile Exchange (“CME”) Growth and Emerging Markets, InterContinental Exchange, Inc. (“ICE”) Futures US, ICE Europe Ltd and London Metal Exchange (“LME”). Exchange firm and clearing organization common stock include shares of CME Group, Inc., ICE, LME, and the Depository Trust & Clearing Corporation (“DTCC”). Exchange and clearing organization memberships required in order to conduct business through the respective venues are recorded at cost and are included in ‘other assets’ on the consolidated balance sheets. Equity investments in exchange firm common stock not required in order to conduct business on the exchanges are classified as trading securities included within ‘financial instruments owned’ on the consolidated balance sheets and recorded at fair value, with unrealized gains and losses recorded as a component of ‘principal gains, net’ on the consolidated income statements. The fair value of exchange firm common stock not required in order to conduct business on the exchanges is determined from quoted market prices. Exchange memberships that represent (a) both an ownership interest and the right to conduct business in the respective venues and are held for operating purposes, or (b) an ownership interest, which must be held by the Company to conduct business in the respective venues are accounted for as an ownership interest at cost with appropriate consideration for other-than-temporary impairment. The cost of exchange and clearing organization memberships that represent an ownership interest and are required in order to conduct business in the respective venues was $5.6 million as of September 30, 2020 and September 30, 2019 compared to a fair value of $6.7 million and $6.0 million as of September 30, 2020 and September 30, 2019, respectively. Fair value was determined using quoted market prices and recent transactions. Alternatively, exchange memberships, or seats, that only represent the right to conduct business on an exchange, but not an ownership interest in the exchange, are accounted for as intangible assets at cost with potential impairment determined under Accounting Standards Codification 350-30- Intangibles - Goodwill and Other . The cost of exchange memberships required in order to conduct business on the exchange, but that do not represent an ownership interest in the exchange, was $5.8 million as of September 30, 2020 and September 30, 2019. As of September 30, 2020, there were no indicators of impairment that would suggest that the carrying value of exchange memberships that don’t represent an ownership interest are impaired, primarily based upon projections of future cash flows and earnings attributable to access these respective venues.
Product Financing Arrangements	Product Financing Arrangements In the normal course of operations, the Company executes notes receivable under repurchase agreements with clients whereby the clients sell certain commodity inventory or other investments to the Company and agree to repurchase the commodity inventory or investment at a future date at a fixed price. These transactions are short-term in nature, and in accordance with the guidance contained in ASC 860, Transfer and Servicing, are treated as secured borrowings rather than commodity inventory and purchases and sales in the Company’s consolidated financial statements. These transactions are reflected as ‘notes receivable’ in the consolidated balance sheet. Commodities or investments sold under repurchase agreements are reflected at the amount of cash received in connection with the transactions. The Company may be required to provide additional collateral based on the fair value of the underlying asset. The Company also participates in commodity repurchase transactions that are accounted for as commodity inventory and purchases and sales of physical commodities as opposed to secured borrowings. The repurchase price under these arrangements is not fixed at the time of execution and, therefore, do not meet all the criteria to be accounted for as product financing arrangements.
Lenders Under Loans and Senior Secured Borrowings	Lenders Under Loans Lenders under loans are accounted for at amortized cost, which approximates fair value due to their variable rates of interest. Senior Secured Borrowings
Acquisitions and Contingent Consideration	Contingent Consideration The Company estimates and records the acquisition date estimated fair value of contingent consideration as part of purchase price consideration for acquisitions. Additionally, each reporting period, the Company estimates changes in the fair value of contingent consideration, and any change in fair value is recognized in the consolidated income statements. An increase in the contingent consideration expected to be paid will result in a charge to operations in the period that the anticipated fair value of contingent consideration increases, while a decrease in the earn-out expected to be paid will result in a credit to operations in the period that the anticipated fair value of contingent consideration decreases. The estimate of the fair value of contingent consideration requires subjective assumptions to be made of future operating results, discount rates, and probabilities assigned to various potential operating result scenarios.
Cost of Sales of Physical Commodities	Cost of Sales of Physical CommoditiesCost of sales of physical commodities include finished commodity or raw material and processing costs along with operating costs relating to the receipt, storage and delivery of the physical commodities. Cost of sales of physical commodities also includes changes in the fair value of agricultural commodity inventories held for sale, and related forward purchase and sale commitments and exchange-traded futures and options contracts.
Interest Expense	Interest ExpenseInterest expense is recognized on an accrual basis. Interest expense is incurred on outstanding balances on the Company’s credit facilities. Interest expense is also incurred on fixed income securities sold, not yet purchased, that the Company holds in its market-marking businesses. Interest expense is also incurred from collateralized transactions, including securities loaned and securities sold under agreements to repurchase
Compensation and Benefits	Compensation and Benefits Compensation and benefits consists primarily of salaries, incentive compensation, variable compensation, including commissions, related payroll taxes and employee benefits. The Company classifies employees as either risk management consultants / traders, operational or administrative personnel, which includes the executive officers. Variable compensation paid to risk management consultants and traders generally represents a fixed percentage of revenues generated, and in some cases, revenues produced less direct costs and an overhead allocation. The Company accrues commission expense on a trade-date basis.
Share-Based Compensation	Share-Based Compensation The Company accounts for share-based compensation in accordance with the guidance in ASC 718-10, Compensation - Stock Compensation. The cost of employee services received in exchange for a share-based award is generally measured based on the grant-date fair value of the award. Share-based employee awards that require future service are amortized over the relevant
Transaction-Based Clearing Expenses	Transaction-Based Clearing Expenses Clearing fees and related expenses include primarily variable expenses for clearing and settlement services, including fees the Company pays to executing brokers, exchanges, clearing organizations and banks. These fees are based on transaction volume, and recorded as expense on the trade date. Clearing fees are passed on to clients and are presented gross in the consolidated statements of income as the Company acts as a principal for these transactions.
Introducing Broker Commissions	Introducing Broker Commissions Introducing broker commissions include commissions paid to non-employee third parties that have introduced clients to the Company. Introducing brokers are individuals or organizations that maintain relationships with clients and accept futures and options orders from those clients. The Company directly provides all account, transaction and margining services to introducing brokers, including accepting money, securities and property from the clients. The commissions are determined and settled monthly.
Income Taxes	Income Taxes Income tax expense includes U.S. federal, state and local and foreign income taxes. Certain items of income and expense are not reported in tax returns and financial statements in the same year. The objectives of accounting for income taxes are to recognize the amount of taxes payable or refundable for the current year. The Company utilizes the asset and liability method to provide income taxes on all transactions recorded in the consolidated financial statements. This method requires that income taxes reflect the expected future tax consequences of temporary differences between the carrying amounts of assets or liabilities for book and tax purposes. Accordingly, a deferred tax asset or liability for each temporary difference is determined based on the tax rates that the Company expects to be in effect when the underlying items of income and expense are realized. Judgment is required in assessing the future tax consequences of events that have been recognized in the Company’s financial statements or tax returns, including the repatriation of undistributed earnings of foreign subsidiaries. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some or all of the deferred tax assets will not be realized. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authority, based upon the technical merits of the position. The tax benefit recognized in the consolidated financial statements from such a position is measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. See Note 20 for further information on the Company’s income taxes.
Additional Paid-In Capital	Additional Paid-In Capital The Company’s additional paid-in capital (“APIC”) consists of stockholder contributions that are in excess of par value of common stock. Included in APIC are amounts related to the exercise of stock options and amortization of share-based compensation.
Comprehensive Income	Comprehensive Income Comprehensive income consists of net income and other gains and losses affecting stockholders’ equity that, under U.S. GAAP, are excluded from net income. Other comprehensive income (loss) includes net actuarial gains and losses from defined benefit pension plans and gains and losses on foreign currency translations.
Accounting Standards Adopted	Accounting Standards Adopted In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842). This update requires a lessee to recognize on the balance sheet a liability to make lease payments and a corresponding right-of-use asset. The guidance also requires certain qualitative and quantitative disclosures about the amount, timing and uncertainty of cash flows arising from leases. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases and ASU 2018-11, Leases (Topic 842) Targeted Improvements. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842) Codification Improvements. Among other things, this updated guidance provides an optional transition method, which allows for the initial application of the new accounting standard at the adoption date and the recognition of a cumulative-effect adjustment to the opening balance of retained earnings as of the beginning of the period of adoption. The Company adopted the new ASUs on October 1, 2019, using the effective date modified retrospective transition approach and has not restated comparative periods. The Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to not reassess contracts to determine if they contain leases, lease classification and initial direct costs. The Company’s application of the new standard resulted in changes to the condensed consolidated balance sheet but did not have an impact on the condensed consolidated income statement. See Note 2 for more information. In February 2018, the FASB issued ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments in this updated standard allow a reclassification from accumulated other comprehensive loss, net to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. The Company adopted this standard on October 1, 2019 and, as a result, recorded a $0.7 million reclassification between accumulated other comprehensive loss, net and retained earnings.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Lease, Cost	The following table presents operating lease costs and other related information as of and for the year ended September 30, 2020 (in millions, except as stated): Year Ended September 30, 2020 Operating lease costs (1) $ 17.2 Supplemental cash flow information and non-cash activity: Cash paid for amounts included in the measurement of operating lease liabilities $ 12.1 Right-of-use assets obtained in exchange for operating lease liabilities $ 96.4 Lease term and discount rate information: Weighted average remaining lease term (years) 11.3 Weighted average discount rate 4.3 %
Schedule of Operating Lease, Liability, Maturity	The maturities of the lease liabilities are as follows as of September 30, 2020 (in millions): 2021 $ 16.0 2022 15.3 2023 13.6 2024 11.8 2025 11.0 After 2025 82.6 Total lease payments 150.3 Less: interest 31.6 Present value of lease liabilities $ 118.7
Schedule of Lessee, Operating Lease	In accordance with the disclosure requirements for the adoption of Topic 842, the Company is presenting its operating lease commitment table as of September 30, 2019, which was previously disclosed in Note 12 of the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2019 (in millions): 2020 $ 11.2 2021 9.9 2022 7.5 2023 6.2 2024 5.8 Thereafter 2.6 $ 43.2

Revenue from Contracts with C_2

Revenue from Contracts with Clients (Tables)	12 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table represents a disaggregation of the Company’s total revenues separated between revenues from contracts with clients and other sources of revenue for the years ended September 30, 2020, 2019, and 2018 (in millions): Year Ended September 30, 2020 2019 2018 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 143.7 $ 144.9 $ 163.4 OTC derivative brokerage 19.7 32.1 30.3 Equities and fixed income 39.9 16.1 11.2 Mutual funds 5.2 7.5 7.2 Insurance and annuity products 8.4 7.3 5.8 Other 1.4 1.3 0.9 Total sales-based commission 218.3 209.2 218.8 Trailing: Mutual funds 12.9 12.4 13.2 Insurance and annuity products 15.3 14.4 14.6 Total trailing commission 28.2 26.8 27.8 Clearing fees 139.0 118.8 123.3 Trade conversion fees 8.9 7.5 6.8 Other 9.2 10.1 15.1 Total commission and clearing fees: 403.6 372.4 391.8 Consulting, management, and account fees: Underwriting fees 0.6 0.7 1.7 Asset management fees 31.3 26.2 24.8 Advisory and consulting fees 22.2 20.0 19.0 Sweep program fees 9.5 16.3 11.6 Client account fees 12.3 10.6 11.1 Other 7.8 5.8 2.9 Total consulting, management, and account fees 83.7 79.6 71.1 Total revenues from contracts with clients $ 487.3 $ 452.0 $ 462.9 Method of revenue recognition: Point-in-time $ 396.1 $ 362.7 $ 379.7 Time elapsed 91.2 89.3 83.2 Total revenues from contracts with clients 487.3 452.0 462.9 Other sources of revenues Physical precious metals trading 51,598.5 30,694.5 25,762.9 Physical agricultural and energy product trading 1,300.7 1,135.8 919.5 Principal gains, net 622.2 415.8 354.1 Interest income 130.9 198.9 123.3 Total revenues $ 54,139.6 $ 32,897.0 $ 27,622.7

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share	The following is a reconciliation of the numerator and denominator of the diluted net income per share computations for the periods presented below. Year Ended September 30, (in millions, except share amounts) 2020 2019 2018 Numerator: Net income $ 169.6 $ 85.1 $ 55.5 Less: Allocation to participating securities (4.0) (1.5) (0.9) Net income allocated to common stockholders $ 165.6 $ 83.6 $ 54.6 Denominator: Weighted average number of: Common shares outstanding 18,824,328 18,738,905 18,549,011 Dilutive potential common shares outstanding: Share-based awards 356,151 275,490 385,819 Diluted shares outstanding 19,180,479 19,014,395 18,934,830

Assets and Liabilities, at Fa_2

Assets and Liabilities, at Fair Value (Tables)	12 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of September 30, 2020 and September 30, 2019 by level in the fair value hierarchy. Except as disclosed in Note 8, there were no assets or liabilities that were measured at fair value on a nonrecurring basis as of September 30, 2020 and September 30, 2019. September 30, 2020 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 3.2 $ — $ — $ — $ 3.2 Money market mutual funds 12.8 — — — 12.8 Cash and cash equivalents 16.0 — — — 16.0 Commodities warehouse receipts 2.4 — — — 2.4 U.S. Treasury obligations 0.2 — — — 0.2 Securities and other assets segregated under federal and other regulations 2.6 — — — 2.6 U.S. Treasury obligations 1,941.3 — — — 1,941.3 To be announced ("TBA") and forward settling securities — 31.0 — (11.8) 19.2 Foreign government obligations 8.0 — — — 8.0 Derivatives 1,949.0 395.8 — (2,537.5) (192.7) Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,898.3 426.8 — (2,549.3) 1,775.8 Receivables from clients, net - Derivatives — 235.6 — (234.1) 1.5 Equity securities 254.9 9.4 — — 264.3 Corporate and municipal bonds — 66.9 — — 66.9 U.S. Treasury obligations 419.9 — — — 419.9 U.S. government agency obligations — 293.4 — — 293.4 Foreign government obligations 2.5 — — — 2.5 Agency mortgage-backed obligations — 1,384.6 — — 1,384.6 Asset-backed obligations — 33.0 — — 33.0 Derivatives 0.7 652.3 — (535.6) 117.4 Commodities leases — 24.9 — — 24.9 Commodities warehouse receipts 103.2 — — — 103.2 Exchange firm common stock 10.1 — — — 10.1 Mutual funds and other 7.5 — — — 7.5 Financial instruments owned 798.8 2,464.5 — (535.6) 2,727.7 Physical commodities inventory 26.8 188.9 — — 215.7 Total assets at fair value $ 4,742.5 $ 3,315.8 $ — $ (3,319.0) $ 4,739.3 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.5 $ — $ 1.5 Payables to clients - Derivatives 2,000.8 176.4 — (2,399.9) (222.7) TBA and forward settling securities — 22.0 — (11.8) 10.2 Derivatives — 306.7 — (302.2) 4.5 Payable to broker-dealers, clearing organizations and counterparties — 328.7 — (314.0) 14.7 Equity securities 218.0 14.9 — — 232.9 Corporate and municipal bonds — 22.5 — — 22.5 U.S. Treasury obligations 247.5 — — — 247.5 U.S. government agency obligations — 0.1 — — 0.1 Agency mortgage-backed obligations — 5.1 — — 5.1 Derivatives 563.6 — (386.8) 176.8 Commodities leases — 1.1 — — 1.1 Financial instruments sold, not yet purchased 465.5 607.3 — (386.8) 686.0 Total liabilities at fair value $ 2,466.3 $ 1,112.4 $ 1.5 $ (3,100.7) $ 479.5 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level. September 30, 2019 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 4.9 $ — $ — $ — $ 4.9 Money market mutual funds 8.9 — — — 8.9 Cash and cash equivalents 13.8 — — — 13.8 Commodities warehouse receipts 6.2 — — — 6.2 U.S. Treasury obligations 299.8 — — — 299.8 Securities and other assets segregated under federal and other regulations 306.0 — — — 306.0 U.S. Treasury obligations 593.9 — — — 593.9 TBA and forward settling securities — 9.8 — (1.5) 8.3 Foreign government obligations 9.9 — — — 9.9 Derivatives 3,131.2 43.2 — (3,159.6) 14.8 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 3,735.0 53.0 — (3,161.1) 626.9 Equity securities 159.5 9.0 — — 168.5 Corporate and municipal bonds — 80.0 — — 80.0 U.S. Treasury obligations 248.7 — — — 248.7 U.S. government agency obligations — 447.1 — — 447.1 Foreign government obligations 0.5 — — — 0.5 Agency mortgage-backed obligations — 1,045.0 — — 1,045.0 Asset-backed obligations — 29.1 — — 29.1 Derivatives 1.0 486.3 — (420.8) 66.5 Commodities leases — 28.6 — — 28.6 Commodities warehouse receipts 48.4 — — — 48.4 Exchange firm common stock 12.7 — — — 12.7 Mutual funds and other 0.1 — — — 0.1 Financial instruments owned 470.9 2,125.1 — (420.8) 2,175.2 Physical commodities inventory 7.1 144.8 — — 151.9 Total assets at fair value $ 4,532.8 $ 2,322.9 $ — $ (3,581.9) $ 3,273.8 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.8 $ — $ 1.8 TBA and forward settling securities — 6.8 — (1.5) 5.3 Derivatives 3,079.1 38.3 — (3,117.1) 0.3 Payable to broker-dealers, clearing organizations and counterparties 3,079.1 45.1 — (3,118.6) 5.6 Equity securities 147.3 10.8 — — 158.1 Corporate and municipal bonds — 39.2 — — 39.2 U.S. Treasury obligations 272.3 — — — 272.3 U.S. government agency obligations — 43.8 — — 43.8 Agency mortgage-backed obligations — 29.6 — — 29.6 Derivatives — 480.3 — (422.2) 58.1 Commodities leases — 113.7 — — 113.7 Financial instruments sold, not yet purchased 419.6 717.4 — (422.2) 714.8 Total liabilities at fair value $ 3,498.7 $ 762.5 $ 1.8 $ (3,540.8) $ 722.2 (1) Represents cash collateral and the impact of netting across the levels of the fair value hierarchy. Netting among positions classified within the same level are included in that level.

Financial Instruments with Of_2

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	12 Months Ended
	Sep. 30, 2020
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Schedule of Derivative Instruments	Listed below are the fair values of the Company’s derivative assets and liabilities as of September 30, 2020 and September 30, 2019. Assets represent net unrealized gains and liabilities represent net unrealized losses. September 30, 2020 September 30, 2019 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,637.2 $ 1,747.3 $ 1,437.1 $ 1,463.4 OTC commodity derivatives 553.9 433.2 84.2 106.2 Exchange-traded foreign exchange derivatives 9.3 13.0 36.9 33.5 OTC foreign exchange derivatives 520.8 461.5 403.2 368.8 Exchange-traded interest rate derivatives 271.1 200.7 900.1 882.0 OTC interest rate derivatives 96.0 96.6 42.1 43.6 Exchange-traded equity index derivatives 32.1 39.8 758.1 700.2 OTC equity and indices derivatives 113.0 55.4 — — TBA and forward settling securities 31.0 22.0 9.8 6.8 Gross fair value of derivative contracts 3,264.4 3264400000 3,069.5 3,671.5 3,604.5 Impact of netting and collateral $ (3,319.0) $ (3,100.7) $ (3,581.9) $ (3,540.8) Total fair value included in 'Deposits with and receivables from broker-dealers, clearing organizations, and counterparties,net' $ (173.5) $ 23.1 Total fair value included in 'Receivables from clients, net' $1.5 $ — Total fair value included in 'Financial instruments owned, at fair value $117.4 66.5 Total fair value included in 'Payables to clients' $ (222.7) $ — Total fair value included in 'Payables to broker-dealers, clearing organizations and counterparties $ 14.7 $ 5.6 Total fair value included in 'Financial instruments sold, not yet purchased, at fair value' $ 176.8 $ 58.1 (1) As of September 30, 2020 and September 30, 2019, the Company’s derivative contract volume for open positions was approximately 7.9 million and 10.6 million contracts, respectively.
Schedule of Derivative Instruments Included in Trading Activities	As of September 30, 2020 and September 30, 2019, TBA and forward settling securities recorded within deposits with and receivables from and payables to broker-dealers, clearing organizations, and counterparties are summarized as follows (in millions): September 30, 2020 September 30, 2019 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 $ 10.8 $ 5,389.3 $ 3.7 $ 1,778.4 Unrealized loss on TBA securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (1.7) $ 2,647.7 $ (0.6) $ 234.5 Unrealized gain on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ 2.8 $ (2,978.7) $ 0.9 $ (451.6) Unrealized loss on TBA securities sold within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ (13.0) $ (6,549.4) $ (5.9) $ (2,788.0) Unrealized loss on forward settling securities purchased within payables to broker-dealers, clearing organizations and counterparties and related notional amounts $ — $ — $ (0.3) $ 1,243.5 Unrealized gain on forward settling securities sold within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ 17.4 $ (1,946.0) $ 5.2 $ (581.2) Unrealized loss on forward settling securities purchased within deposits with and receivables from broker-dealers, clearing organizations and counterparties, net and related notional amounts $ (7.3) $ 2,447.1 $ — $ — The notional amounts of these instruments reflect the extent of the Company’s involvement in TBA and forward settling securities and do not represent counterparty exposure.
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The following table sets forth the Company’s net gains (losses) related to derivative financial instruments for the fiscal years ended September 30, 2020, 2019, and 2018, in accordance with the Derivatives and Hedging Topic of the ASC. The net gains (losses) set forth below are included in ‘principal gains, net’ and ‘cost of sales of physical commodities’ in the consolidated income statements. Year Ended September 30, (in millions) 2020 2019 2018 Commodities $ 197.3 $ 100.8 $ 94.0 Foreign exchange 38.2 8.1 9.2 Interest rate, equities, and indices 20.4 (2.6) 1.0 TBA and forward settling securities (49.7) (35.3) 14.5 Net gains from derivative contracts $ 206.2 $ 71.0 $ 118.7

Allowance for Doubtful Accoun_2

Allowance for Doubtful Accounts (Tables)	12 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Schedule of Allowance for Doubtful Accounts	Activity in the allowance for doubtful accounts for the fiscal years ended September 30, 2020, 2019, and 2018 was as follows: (in millions) 2020 2019 2018 Balance, beginning of year $ 48.6 $ 58.2 $ 54.6 Provision (recovery) for bad debts 13.0 (9.8) 3.9 Allowance charge-offs (35.6) (1.3) (0.3) Other (1) 1.1 1.5 — Balance, end of year $ 27.1 $ 48.6 $ 58.2 (1) Allowance increase is related to a recoverable amount due from an affiliated party and recorded in ‘other assets’ on the consolidated balance sheets.

Physical Commodities Inventory

Physical Commodities Inventory (Tables)	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Schedule of Inventory	The Company’s inventories consist of finished physical commodities as shown below. (in millions) September 30, September 30, 2019 Physical Ag & Energy (1) $ 201.5 $ 144.8 Precious metals - held by broker-dealer subsidiary (2) 14.2 7.1 Precious metals - held by non-broker-dealer subsidiaries (3) 65.4 77.4 Physical commodities inventory $ 281.1 $ 229.3 (1) Physical Ag & Energy consists of agricultural commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, cocoa, cotton, and others. The agricultural commodity inventories are carried at net realizable value, which approximates selling prices in the ordinary course of business, less disposal costs, with changes in net realizable value included as a component of ‘cost of sales of physical commodities’ on the consolidated income statements. The agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. Physical Ag & Energy also consists of energy related inventories, including primarily propane, gasoline, and kerosene, which are valued at the lower of cost or net realizable value. (2) Precious metals held by the Company’s subsidiary, StoneX Financial Ltd, a U.K. based broker-dealer subsidiary, is measured at fair value, with changes in fair value included as a component of ‘principal gains, net’ on the consolidated income statements, in accordance with U.S. GAAP accounting requirements for broker-dealers. (3) Precious metals inventory held by subsidiaries that are not broker-dealers are valued at the lower of cost or net realizable value.

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment	A summary of property and equipment, at cost less accumulated depreciation as of September 30, 2020 and 2019 is as follows: (in millions) September 30, 2020 September 30, 2019 Property and equipment: Furniture and fixtures $ 10.2 $ 10.6 Software 28.6 33.9 Equipment 30.8 28.1 Leasehold improvements 38.3 20.3 Total property and equipment 107.9 92.9 Less accumulated depreciation (45.8) (49.0) Property and equipment, net $ 62.1 $ 43.9

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill allocated to the Company’s operating segments as of September 30, 2020 and 2019 is as follows: (in millions) September 30, September 30, 2019 Commercial $ 32.7 $ 32.7 Institutional 9.8 8.7 Retail 2.2 2.2 Global Payments 10.0 7.6 Total Goodwill 54.7 51.2

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2020
Intangible Assets [Abstract]
Schedule of Finite and Indefinite-Lived Intangible Assets	The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows (in millions): September 30, 2020 September 30, 2019 Gross Amount Accumulated Net Amount Gross Amount Accumulated Net Amount Intangible assets subject to amortization: Trade/domain names $ 3.7 $ (0.2) $ 3.5 $ — $ — $ — Software programs/platforms 29.0 (4.9) 24.1 5.3 (3.0) 2.3 Customer base 38.2 (16.3) 21.9 22.1 (12.5) 9.6 Total intangible assets subject to amortization 70.9 (21.4) 49.5 27.4 (15.5) 11.9 Intangible assets not subject to amortization: Website domains 2.1 — 2.1 2.1 — 2.1 Business licenses 3.2 — 3.2 2.7 — 2.7 Total intangible assets not subject to amortization: 5.3 — 5.3 4.8 — 4.8 Total intangible assets $ 76.2 $ (21.4) $ 54.8 $ 32.2 $ (15.5) $ 16.7
Schedule of Expected Amortization Expense	As of September 30, 2020, the estimated future amortization expense was as follows: (in millions) Fiscal 2021 $ 15.1 Fiscal 2022 13.8 Fiscal 2023 12.2 Fiscal 2024 4.7 Fiscal 2025 and thereafter 3.7 $ 49.5

Credit Facilities (Tables)

Credit Facilities (Tables)	12 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Debt	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 and the Senior Secured Notes as of the periods indicated: (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment September 30, 2020 September 30, 2019 Committed Credit Facilities Term Loan (1) February 22, 2022 $ 180.1 $ 179.5 (3) $ 167.6 Revolving Line of Credit (1) February 22, 2022 196.5 23.0 70.0 Senior StoneX Group Inc. Committed Credit Facility 376.6 202.5 237.6 StoneX Financial Inc. None April 2, 2021 75.0 — — FCStone Merchants Services, LLC Certain commodities assets January 29, 2022 260.0 200.1 128.5 StoneX Financial Ltd. (4) None October 14, 2021 25.0 25.0 — $ 736.6 $ 427.6 $ 366.1 Uncommitted Credit Facilities StoneX Financial Inc. Commodities warehouse receipts and certain pledged securities n/a n/a — — FCStone Merchant Services, LLC Certain commodities assets n/a n/a — 3.4 StoneX Financial Ltd. Commodities warehouse receipts n/a n/a 20.0 — Notes payable to bank Certain equipment — 0.4 Senior Secured Notes (2) $ 336.0 (3) $ — Total outstanding borrowings $ 783.6 $ 369.9 (1) The StoneX Group Inc. committed credit facility is secured by substantially all of the assets of StoneX Group Inc. and certain subsidiaries identified in the credit facility agreement as obligors, and pledged equity of certain subsidiaries identified in the credit facility as limited guarantors. (2) The Senior Secured Notes and the related guarantees are secured by liens on substantially all of the Company’s and the guarantors’ assets, subject to certain customary and other exceptions and permitted liens. The liens on the assets that secure the Senior Secured Notes and the related guarantees are contractually subordinated to the liens on the assets that secure the Company’s and the guarantors’ existing and future first lien secured indebtedness, including indebtedness under the Company’s senior committed credit facility. (3) Amounts outstanding under the Term Loan and the Senior Secured Notes are reported net of unamortized deferred financing costs and original issue discount of $0.5 million and $14.0 million, respectively. (4) The StoneX Financial Ltd committed credit facility facility in place at September 30, 2020 matured on October 14, 2020 and was replaced by an unsecured syndicated committed borrowing facility with substantially the similar terms. The expiration date noted above relates to the new facility which became effective October 14, 2020.

Regulatory Requirements and S_2

Regulatory Requirements and Subsidiary Dividend Restrictions (Tables)	12 Months Ended
	Sep. 30, 2020
Capital and Other Regulatory Requirements [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	The following table details the Company’s subsidiaries with a minimum regulatory net capital requirement in excess of $5.0 million as well as the actual regulatory capital of the subsidiary as of September 30, 2020 (in millions): Subsidiary Regulatory Authority Actual Minimum StoneX Financial Inc. SEC and CFTC $ 229.8 $ 137.6 StoneX Financial Ltd. FCA $ 264.3 $ 145.1 Gain Capital Group, LLC CFTC $ 71.5 $ 32.2 Gain Capital U.K. Ltd. FCA $ 185.4 $ 65.2

Securities and Commodity Fina_2

Securities and Commodity Financing Transactions - Gross Obligations Contractual Maturities (Tables)	12 Months Ended
	Sep. 30, 2020
Brokers and Dealers [Abstract]
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets	The following tables provide the contractual maturities of gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): September 30, 2020 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 1,736.3 $ 1,069.2 $ 325.0 25.0 $ 3,155.5 Securities loaned 1,441.9 — — — 1,441.9 Gross amount of secured financing $ 3,178.2 $ 1,069.2 $ 325.0 $ 25.0 $ 4,597.4 September 30, 2019 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 1,553.9 $ 565.8 $ 654.0 — $ 2,773.7 Securities loaned 1,459.9 — — — 1,459.9 Gross amount of secured financing $ 3,013.8 $ 565.8 $ 654.0 — $ 4,233.6
Schedule of Financial Instruments Owned and Pledged as Collateral	The following table provides the underlying collateral types of the gross obligations under repurchase and securities lending agreements as of the periods indicated (in millions): Securities sold under agreements to repurchase September 30, 2020 September 30, 2019 U.S. Treasury obligations $ 815.8 $ 108.8 U.S. government agency obligations 279.5 359.5 Asset-backed obligations 18.0 96.7 Agency mortgage-backed obligations 1,990.0 2,208.7 Corporate bonds 52.2 — Total securities sold under agreement to repurchase $ 3,155.5 $ 2,773.7 Securities loaned Equity securities 1,441.9 1,459.9 Total securities loaned 1,441.9 1,459.9 Gross amount of secured financing $ 4,597.4 $ 4,233.6 The following tables provide the netting of securities purchased under agreements to resell, securities sold under agreements to repurchase, securities borrowed and securities loaned as of the periods indicated (in millions): September 30, 2020 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 1,696.2 $ — $ 1,696.2 Securities borrowed $ 1,440.0 $ — $ 1,440.0 Securities sold under agreements to repurchase $ 3,155.5 $ — $ 3,155.5 Securities loaned $ 1,441.9 $ — $ 1,441.9 September 30, 2019 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Consolidated Balance Sheet Net Amounts Presented in the Consolidated Balance Sheet Securities purchased under agreements to resell $ 1,474.4 $ (49.9) $ 1,424.5 Securities borrowed $ 1,423.2 $ — $ 1,423.2 Securities sold under agreements to repurchase $ 2,823.6 $ (49.9) $ 2,773.7 Securities loaned $ 1,459.9 $ — $ 1,459.9

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Payment Award, Stock options, Valuation Assumptions	Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions: Fiscal Year Ended September 30, 2020 2020 (1) 2019 2018 Expected stock price volatility — % 27 % 30 % Expected dividend yield — % — % — % Risk free interest rate — % 1.86 % 1.23 % Average expected life (in years) 0.00 6.05 3.06 (1) There were no stock options granted under the plan during the year ended September 30, 2020.
Share-based Compensation, Stock Options, Activity	The following is a summary of stock option activity for the year ended September 30, 2020: Shares Number of Weighted Weighted Weighted Aggregate Balances at September 30, 2019 692,652 1,684,378 $ 37.59 $ 11.32 4.62 $ 9.2 Exercised (244,511) $ 30.56 $ 11.36 Forfeited 13,662 (13,662) $ 39.64 $ 8.62 Expired 18,169 (18,169) $ 37.30 $ 8.19 Balances at September 30, 2020 724,483 1,408,036 $ 38.79 $ 11.38 4.16 $ 17.4 Exercisable at September 30, 2020 423,112 $ 29.25 $ 12.64 1.38 $ 9.3
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range	The options outstanding as of September 30, 2020 broken down by exercise price are as follows: Exercise Price Number of Options Outstanding Weighted Average Exercise Price Weighted Average Remaining Term $ — - $ 5.00 — n/a n/a $ 5.00 - $ 10.00 — n/a n/a $ 10.00 - $ 15.00 — n/a n/a $ 15.00 - $ 20.00 — n/a n/a $ 20.00 - $ 25.00 — n/a n/a $ 25.00 - $ 30.00 420,000 $ 25.91 1.36 $ 30.00 - $ 35.00 — n/a n/a $ 35.00 - $ 40.00 126,161 $ 39.65 2.02 $ 40.00 - $ 45.00 859,875 $ 44.92 5.84 $ 45.00 - $ 50.00 — n/a n/a $ 50.00 - $ 55.00 — n/a n/a $ 55.00 - $ 60.00 2,000 $ 55.28 1.89 1,408,036 $ 38.79 4.16
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following is a summary of restricted stock activity through September 30, 2020: Shares Number of Weighted Weighted Aggregate Balances at September 30, 2019 1,156,902 350,778 $ 40.06 1.36 $ 14.4 Granted (299,858) 299,858 $ 44.94 Vested — (161,880) $ 40.26 Forfeited 4,410 (4,410) $ 44.23 Balances at September 30, 2020 861,454 484,346 $ 42.97 1.37 $ 24.8

Other Expenses (Tables)

Other Expenses (Tables)	12 Months Ended
	Sep. 30, 2020
Other Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component	Other expenses for the years ended September 30, 2020, 2019, and 2018 are comprised of the following: Year Ended September 30, (in millions) 2020 2019 2018 Insurance $ 4.7 $ 3.4 $ 2.6 Office supplies and printing 1.8 1.9 1.7 Other clearing related expenses 2.8 2.5 2.5 Other non-income taxes 6.6 4.6 4.9 Contingent consideration, net 0.5 — — Other 13.2 10.8 8.4 Total other expenses $ 29.6 $ 23.2 $ 20.1

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense (benefit) for the years ended September 30, 2020, 2019, and 2018 was allocated as follows: Year Ended September 30, (in millions) 2020 2019 2018 Income tax expense attributable to income from operations $ 37.1 $ 25.9 $ 46.0 Taxes allocated to stockholders’ equity, related to pension liabilities — (0.2) 0.1 Total income tax expense $ 37.1 $ 25.7 $ 46.1 The components of income tax expense (benefit) attributable to income from operations were as follows: Year Ended September 30, (in millions) 2020 2019 2018 Current taxes: U.S. federal $ (0.6) $ (1.9) $ 0.8 U.S. State and local 2.3 (0.8) 0.5 International 31.3 24.9 22.4 Total current taxes 33.0 22.2 23.7 Deferred taxes 4.1 3.7 22.3 Income tax expense $ 37.1 $ 25.9 $ 46.0
Schedule of Income before Income Tax, Domestic and Foreign	U.S. and international components of income (loss) from operations, before tax, was as follows: Year Ended September 30, (in millions) 2020 2019 2018 U.S. $ 88.8 $ (2.6) $ 9.9 International 117.9 113.6 91.6 Income from operations, before tax $ 206.7 $ 111.0 $ 101.5
Schedule of Effective Income Tax Rate Reconciliation	Items accounting for the difference between income taxes computed at the federal statutory rate and income tax expense were as follows: Year Ended September 30, 2020 2019 2018 Federal statutory rate effect of: 21.0 % 21.0 % 24.5 % U.S. State and local income taxes 1.0 % (1.5) % 0.8 % Foreign earnings and losses taxed at different rates 0.1 % 0.7 % (0.8) % Change in foreign valuation allowance 1.0 % 1.0 % (0.8) % Change in state valuation allowance 0.2 % 0.5 % — % U.S. permanent items 0.9 % 0.1 % (0.2) % Foreign permanent items 0.5 % 0.7 % 2.1 % U.S. bargain purchase gain (8.3) % (1.0) % — % Remeasurement of deferred tax — % — % 8.5 % Repatriation Transition tax — % — % 11.0 % GILTI 0.7 % 2.2 % — % Other reconciling items 0.9 % (0.4) % 0.2 % Effective rate 18.0 % 23.3 % 45.3 %
Schedule of Deferred Tax Assets and Liabilities	The components of deferred income tax assets and liabilities were as follows: (in millions) September 30, 2020 September 30, 2019 Deferred tax assets: Share-based compensation $ 3.1 $ 3.3 Deferred compensation 4.1 3.6 Foreign net operating loss carryforwards 5.4 2.6 U.S. State and local net operating loss carryforwards 9.0 9.2 U.S. federal net operating loss carryforwards 1.8 1.1 Intangible assets 9.9 4.8 Bad debt reserve 4.4 1.3 Tax credit carryforwards 0.2 0.5 Foreign tax credit carryforwards 2.4 5.0 Other compensation 5.8 2.2 Property and equipment 7.3 — Other 1.9 1.1 Total gross deferred tax assets 55.3 34.7 Less valuation allowance (12.4) (8.5) Deferred tax assets 42.9 26.2 Deferred income tax liabilities: Unrealized gain on securities 2.4 3.2 Prepaid expenses 3.4 2.2 Property and equipment — 2.6 Pension liability 0.2 0.2 Deferred income tax liabilities 6.0 8.2 Deferred income taxes, net $ 36.9 $ 18.0

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Schedule of Aggregate Merger Consideration	The aggregate merger consideration was (in millions): Aggregate cash consideration $ 215.0 Accrual for merger cash consideration 21.6 Total merger consideration $ 236.6
Schedule of Preliminary Purchase Price Allocation as of the Acquisition	The following table summarizes the preliminary purchase price allocation as of the Gain acquisition date (in millions): Preliminary Purchase Price Allocation Cash and cash equivalents $ 507.2 Cash, securities and other assets segregated under federal and other regulations 497.4 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties (1) 249.7 Receivables from clients, net (2) 2.0 Income taxes receivable 0.4 Deferred income taxes, net 23.0 Property and equipment, net 6.1 Right of use assets, net 15.0 Other assets 17.9 Total fair value of tangible assets acquired 1,318.7 Accounts payable and other accrued liabilities 52.7 Operating lease liabilities 15.0 Payable to clients 863.4 Payable to broker-dealers, clearing organizations, and counterparties 0.5 Income taxes payable 12.4 Convertible senior notes (3) 92.0 Total fair value of tangible liabilities assumed 1,036.0 Fair value of tangible net assets acquired (4) 282.7 Identifiable intangible assets acquired Trademarks/domain names (5) 3.7 Software programs/platforms (5) 22.2 Customer base (5) 9.8 Total fair value of intangible assets acquired 35.7 Fair value of identifiable net assets acquired 318.4 Total merger consideration 236.6 Bargain purchase gain $ 81.8 (1) Amount represents the contractual amount of deposits with and receivables from broker-dealers, clearing organizations, and counterparties, all of which the Company expects to be collectible as of the Gain acquisition date. (2) 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 Gain acquisition date. (3) As $91.5 million of the $92.0 million in aggregate principal of the Gain Notes were redeemed on September 1, 2020, the Company believes that the face value of the Gain Notes approximated their fair value as of the Gain acquisition date due to the fundamental change right provided for in the Gain Notes indenture. Refer to Note 12 for further discussion of the Gain Notes redemption. (4) With the exception of deferred income taxes and the convertible senior notes, the Company believes that the fair value of the tangible assets acquired and tangible liabilities assumed approximate their carrying values as of the Gain acquisition date due either to their short-term nature, the Company’s ability to initiate the withdrawal and settlement of client related trading balances, or the fact that the balances are recorded at fair value on a recurring basis. (5) The trademark/domain names, software programs/platforms, and customer base intangible assets have been assigned useful lives of 5 years, 3 years, and 4 years, respectively. 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. 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 $ 2.0 Receivables from clients (1) 1.2 Receivable from affiliate 1.1 Income tax receivable 0.1 Physical commodities inventory 9.8 Deferred tax assets, net 0.2 Other assets 1.2 Total fair value of tangible assets acquired 15.6 Accounts payable and other accrued liabilities 0.2 Payables to clients 0.2 Total fair value of tangible liabilities assumed 0.4 Fair value of net tangible assets acquired 15.2 Purchase price 22.0 Excess purchase price over fair value of tangible net assets acquired $ 6.8 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Domain names $ 2.1 Internally developed software 2.5 Total excess purchase price allocated to identifiable intangible assets 4.6 Remaining excess allocated to goodwill $ 2.2 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 $ 0.2 Deposits with and receivables from broker-dealers, clearing organizations, and counterparties 0.3 Receivables from clients, net (1) 0.2 Other assets 0.4 Total fair value of tangible assets acquired 1.1 Accounts payable and other accrued liabilities 0.5 Total fair value of tangible liabilities assumed 0.5 Fair value of net tangible assets acquired 0.6 Purchase price (2) 3.2 Excess purchase price over fair value of tangible net assets acquired $ 2.6 Excess purchase price over fair value of tangible net assets acquired allocated to identifiable intangible assets: Client relationships $ 0.7 Total excess purchase price allocated to identifiable intangible assets 0.7 Remaining excess allocated to goodwill $ 1.9 (1) Amount represents the contractual amount of receivables due from clients for trading activity, all of which was collected. (2) Includes the fair value of contingent consideration of $1.8 million.
Schedule of Business Acquisition Pro Forma Financial Information	The following unaudited pro forma financial information (in millions, except per share amounts) has been adjusted to give effect to the Gain merger as if it were consummated on October 1, 2018. Year Ended September 30, 2020 Year Ended September 30, 2019 Total revenues $ 54,414.1 $ 33,160.0 Net income $ 138.5 $ 38.3 Basic earnings per share $ 7.17 $ 2.01 Diluted earnings per share $ 7.02 $ 1.97

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive (Loss) Income (Tables)	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Loss	The following table summarizes the changes in accumulated other comprehensive loss for the year ended September 30, 2020. (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Accumulated Other Comprehensive Loss Balances as of September 30, 2019 $ (31.5) $ (3.3) $ (34.8) ASU 2018-02 cumulative transition adjustment — (0.7) (0.7) Adjusted Balances as of September 30, 2019 (31.5) (4.0) (35.5) Other comprehensive loss (4.5) (0.2) (4.7) Amounts reclassified from AOCI, net of tax — 0.1 0.1 Other comprehensive loss (4.5) (0.1) (4.6) Balances as of September 30, 2020 $ (36.0) $ (4.1) $ (40.1)

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	12 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Schedule of Segment Reporting Information	Information for the reportable segments is shown in accordance with the Segment Reporting Topic of the ASC as follows Year Ended September 30, (in millions) 2020 2019 2018 Total revenues: Commercial $ 52,970.1 $ 32,125.4 $ 27,018.7 Institutional 624.1 515.0 427.1 Retail 432.7 148.1 73.3 Global Payments 117.4 112.8 99.2 Corporate Unallocated 14.6 20.8 23.9 Eliminations (19.3) (25.1) (19.5) Total $ 54,139.6 $ 32,897.0 $ 27,622.7 Operating revenues: Commercial $ 431.5 $ 404.4 $ 371.8 Institutional 624.1 515.0 427.1 Retail 140.0 78.2 73.3 Global Payments 117.4 112.8 99.2 Corporate Unallocated 14.6 20.8 23.9 Eliminations (19.3) (25.1) (19.5) Total $ 1,308.3 $ 1,106.1 $ 975.8 Net operating revenues (loss): Commercial $ 353.4 $ 321.2 $ 299.4 Institutional 363.8 220.1 176.3 Retail 63.8 15.7 12.7 Global Payments 111.5 107.0 93.5 Corporate Unallocated (24.5) (10.8) (0.3) Total $ 868.0 $ 653.2 $ 581.6 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial $ 242.2 $ 224.6 $ 210.0 Institutional 248.9 157.0 135.6 Retail 58.8 14.6 11.8 Global Payments 89.6 86.6 75.0 Total $ 639.5 $ 482.8 $ 432.4 Segment income (loss): (Net contribution less non-variable direct segment costs) Commercial (1) $ 141.9 $ 144.6 $ 118.3 Institutional 152.9 88.6 78.2 Retail 31.7 6.4 5.6 Global Payments 68.6 66.1 59.8 Total $ 395.1 $ 305.7 $ 261.9 Reconciliation of segment income to income before tax: Segment income $ 395.1 $ 305.7 $ 261.9 Net costs not allocated to operating segments (270.3) (200.2) (162.4) Gain on acquisitions and other gains 81.9 5.5 2.0 Income before tax $ 206.7 $ 111.0 $ 101.5 (1) During fiscal 2019, the Company recorded recoveries on the bad debt on physical coal of $12.4 million. During fiscal 2018, the Company recorded charges to earnings of $1.0 million to record an allowance for doubtful accounts related to a bad debt incurred in the physical coal business with a coal supplier, as further discussed in Note 19. (in millions) As of September 30, 2020 As of September 30, 2019 As of September 30, 2018 Total assets: Commercial $ 2,753.6 $ 2,386.4 $ 2,349.5 Institutional 8,740.8 7,111.2 5,168.1 Retail 1,245.9 12.4 — Global Payments 315.9 278.2 206.6 Corporate unallocated 418.7 147.9 100.5 Total $ 13,474.9 $ 9,936.1 $ 7,824.7
Schedule of Revenue Long-Lived Assets, by Geographical Areas	Information regarding revenues and operating revenues for the years ended September 30, 2020, 2019, and 2018, and information regarding long-lived assets (defined as property, equipment, leasehold improvements and software) as of September 30, 2020, 2019, and 2018 in geographic areas were as follows: Year Ended September 30, (in millions) 2020 2019 2018 Total revenues: United States $ 2,223.3 $ 1,947.6 $ 1,587.6 Europe 532.6 280.2 189.6 South America 58.9 56.5 59.5 Middle East and Asia 51,317.1 30,606.9 25,781.4 Other 7.7 5.8 4.6 Total $ 54,139.6 $ 32,897.0 $ 27,622.7 Operating revenues: United States $ 928.3 $ 799.4 $ 695.3 Europe 237.9 209.6 189.0 South America 58.9 56.5 58.0 Middle East and Asia 75.5 34.8 28.9 Other 7.7 5.8 4.6 Total $ 1,308.3 $ 1,106.1 $ 975.8 (in millions) As of September 30, 2020 As of September 30, 2019 As of September 30, 2018 Long-lived assets, as defined: United States $ 55.4 $ 33.9 $ 33.0 Europe 3.1 6.6 6.8 South America 2.1 2.1 1.4 Middle East and Asia 1.3 1.0 1.2 Other 0.2 0.3 — Total $ 62.1 $ 43.9 $ 42.4

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information (Unaudited)	The Company has set forth certain quarterly unaudited financial data for the past two years in the tables below: For the 2020 Fiscal Quarter Ended (in millions, except per share amounts) September 30 June 30 March 31 December 31 Total revenues $ 14,284.9 $ 8,243.4 $ 20,366.3 $ 11,245.0 Cost of sales of physical commodities 13,942.8 7,920.8 19,999.5 10,968.2 Operating revenues 342.1 322.6 366.8 276.8 Transaction-based clearing expenses 57.1 55.3 63.8 46.3 Introducing broker commissions 34.0 24.0 29.6 26.2 Interest expense 10.0 11.5 27.8 31.1 Interest expense on corporate funding 14.8 3.9 2.2 2.7 Net operating revenues 226.2 227.9 243.4 170.5 Compensation and benefits 145.5 132.5 136.7 104.0 Bad debts, net of recoveries and impairment 12.5 1.8 4.4 — Other expenses 70.1 44.6 46.2 44.9 Total compensation and other expenses 228.1 178.9 187.3 148.9 Gain on acquisitions (1) 81.8 — — 0.1 Income before tax 79.9 49.0 56.1 21.7 Income tax expense 2.5 12.4 16.8 5.4 Net income $ 77.4 $ 36.6 $ 39.3 $ 16.3 Net basic earnings per share $ 4.00 $ 1.90 $ 2.03 $ 0.85 Net diluted earnings per share $ 3.90 $ 1.87 $ 2.00 $ 0.84 For the 2019 Fiscal Quarter Ended (in millions, except per share amounts) September 30, June 30, March 31, December 31, Total revenues $ 11,279.6 $ 7,873.0 $ 7,192.2 $ 6,552.2 Cost of sales of physical commodities 10,992.7 7,589.6 6,921.1 6,287.5 Operating revenues 286.9 283.4 271.1 264.7 Transaction-based clearing expenses 45.0 45.7 42.7 50.1 Introducing broker commissions 27.7 29.6 24.8 32.6 Interest expense 37.2 39.4 35.2 30.2 Interest expense on corporate funding 3.6 3.1 3.2 2.8 Net operating revenues 173.4 165.6 165.2 149.0 Compensation and benefits 105.2 100.9 97.9 89.1 Bad debts, net of recoveries 1.0 0.5 0.7 0.3 Recovery of bad debt on physical coal (2) (10.0) — — (2.4) Other expenses 43.2 42.6 41.1 37.6 Total compensation and other expenses 139.4 144.0 139.7 124.6 Gain on acquisitions (3) 0.1 — 5.4 — Income before tax 34.1 21.6 30.9 24.4 Income tax expense 6.9 5.3 7.5 6.2 Net income (loss) $ 27.2 $ 16.3 $ 23.4 $ 18.2 Net basic (loss) earnings per share $ 1.42 $ 0.85 $ 1.23 $ 0.96 Net diluted (loss) earnings per share $ 1.40 $ 0.84 $ 1.21 $ 0.94 (1) During the fourth quarter ended September 30, 2020, the Company recorded a bargain purchase gain of $81.8 million related to the acquisition of Gain. See Note 21 for additional information. (2) During the fourth quarter ended September 30, 2019, the Company recorded a recovery on the bad debt on physical coal received through an insurance policy claim related to the matter. See Note 19 for additional information.

Description of Business and S_3

Description of Business and Significant Accounting Policies (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)countryclient$ / sharesshares	Sep. 30, 2019USD ($)$ / sharesshares	Sep. 30, 2018USD ($)	Jan. 14, 2019
Number of commercial and institutional clients (more than) | client	32,000
Number retail clients (more than) | client	330,000
Number of countries in which entity operates (more than) | country	180
Selling and marketing	$ 12.2	$ 5.2	$ 6.2
Amount recognized in loss due to inflationary accounting		3.9	3.4
Net assets and liabilities denominated in argentine pesos	0.1	(5.5)
Cash denominated in argentine pesos	0.1	1.4
Net denominated in argentine pesos	0.9	1
Cash held at banks and money market funds - segregated	1,907.2	743.9
US government obligations and other securities	10.6	299.8
Commodities warehouse receipts	2.4	6.2
Cash and cash equivalents - deposits and receivables	1,600	1,600
US government securities and other securities - deposits and receivables	$ 1,949.3	603.8
Acquired finite-lived intangible asset, weighted average useful life	1 year
Fair Value of exchange memberships	$ 6.7	$ 6
Preferred stock - authorized (in shares) | shares	1,000,000	1,000,000
Preferred stock - par value (in dollar per share) | $ / shares	$ 0.01	$ 0.01
Preferred stock - outstanding (in shares) | shares	0	0
Cumulative effect of new accounting principle in period of adoption		$ 0.7
Minimum [Member]
Property plant and equipment, useful life	3 years
Identifiable intangible assets	5 years
Maximum [Member]
Property plant and equipment, useful life	10 years
Identifiable intangible assets	20 years
Retail [Member]
Number of countries in which entity operates (more than) | country	130
Software Development [Member]
Property plant and equipment, useful life	3 years
Exchange Memberships Representing an Ownership Interest [Member]
Memberships in exchanges owned	$ 5.6	5.6
Exchange Memberships not Representing an Ownership Interest [Member]
Memberships in exchanges owned	$ 5.8	$ 5.8
Commission and Clearing Fees [Member]
Prior period reclassification adjustment			$ 35
GMP Securities Acquisition [Member]
Percentage of stock purchased				100.00%

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)officeSpace	Oct. 01, 2019USD ($)
Lessee, Lease, Description [Line Items]
Number of options to renew | officeSpace	1
Termination period	2 years
Operating right of use assets	$ 101.5	$ 33.1
Operating lease liabilities	$ 118.7	$ 36.2
Building [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Renewal term	3 years
Building [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Renewal term	10 years

Leases - Operating Lease Costs

Leases - Operating Lease Costs and Other Related Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Leases [Abstract]
Operating lease costs	$ 17.2
Cash paid for amounts included in the measurement of operating lease liabilities	12.1
Right-of-use assets obtained in exchange for operating lease liabilities	$ 96.4
Weighted average remaining lease term (years)	11 years 3 months 18 days
Weighted average discount rate	4.30%

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Oct. 01, 2019
Leases [Abstract]
2021	$ 16
2022	15.3
2023	13.6
2024	11.8
2025	11
After 2025	82.6
Total lease payments	150.3
Less: interest	31.6
Present value of lease liabilities	$ 118.7	$ 36.2

Leases - Operating Lease Commit

Leases - Operating Lease Commitment (Details) $ in Millions	Sep. 30, 2019USD ($)
Leases [Abstract]
2020	$ 11.2
2021	9.9
2022	7.5
2023	6.2
2024	5.8
Thereafter	2.6
Operating leases, future minimum payments due	$ 43.2

Revenue from Contracts with C_3

Revenue from Contracts with Clients - Narrative (Details)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Total revenues (percentage)	0.90%	1.40%	1.70%
Operating revenues (percentage)	37.20%	40.90%	47.40%
Term of risk management consulting contracts	6 months

Revenue from Contracts with C_4

Revenue from Contracts with Clients - Revenue from Contracts with Clients (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									$ 487.3	$ 452	$ 462.9
Sales of physical commodities									52,899.2	31,830.3	26,682.4
Principal gains, net									622.2	415.8	354.1
Interest income									130.9	198.9	123.3
Total revenues	$ 14,284.9	$ 8,243.4	$ 20,366.3	$ 11,245	$ 11,279.6	$ 7,873	$ 7,192.2	$ 6,552.2	54,139.6	32,897	27,622.7
Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									396.1	362.7	379.7
Time Elapsed [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									91.2	89.3	83.2
Exchange-Traded Futures and Options [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									143.7	144.9	163.4
OTC Derivative Brokerage [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									19.7	32.1	30.3
Equities and Fixed Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									39.9	16.1	11.2
Mutual Fund Sales Based [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									5.2	7.5	7.2
Insurance and Annuity Products [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									8.4	7.3	5.8
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									1.4	1.3	0.9
Sales Based Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									218.3	209.2	218.8
Mutual Fund [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									12.9	12.4	13.2
Insurance Annuity Trailing [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									15.3	14.4	14.6
Trailing Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									28.2	26.8	27.8
Clearing Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									139	118.8	123.3
Trade Conversion Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									8.9	7.5	6.8
Other Commission and Clearing Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									9.2	10.1	15.1
Commission and Clearing Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									403.6	372.4	391.8
Underwriting Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									0.6	0.7	1.7
Asset Management Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									31.3	26.2	24.8
Advisory and Consulting Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									22.2	20	19
Sweep Program Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									9.5	16.3	11.6
Client Account Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									12.3	10.6	11.1
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									7.8	5.8	2.9
Consulting, Management, and Account Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer									83.7	79.6	71.1
Precious Precious Metals Trading [Member]
Disaggregation of Revenue [Line Items]
Sales of physical commodities									51,598.5	30,694.5	25,762.9
Physical Agricultural and Energy Product trading [Member]
Disaggregation of Revenue [Line Items]
Sales of physical commodities									$ 1,300.7	$ 1,135.8	$ 919.5

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 169.6	$ 85.1	$ 55.5
Less: Allocation to participating securities	(4)	(1.5)	(0.9)
Net income allocated to common stockholders	$ 165.6	$ 83.6	$ 54.6
Denominator:
Common shares outstanding (in shares)	18,824,328	18,738,905	18,549,011
Dilutive potential common shares outstanding:
Share-based awards (in shares)	356,151	275,490	385,819
Diluted shares outstanding (in shares)	19,180,479	19,014,395	18,934,830

Earnings per Share - Narrative

Earnings per Share - Narrative (Details) - shares	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Antidilutive securities	898,420	907,089	92,627

Assets and Liabilities, at Fa_3

Assets and Liabilities, at Fair Value - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	$ 272.6	$ 157.5
Cash settlements	0.9
Remeasurement losses	0.6
Equity investments in exchange stock - cost	3.7	3.7
Financial instruments, owned, at fair value	2,727.7	2,175.2
Senior secured borrowings, net	$ 336	0
Senior Notes Due Twenty Twenty Two [Member] | Gain Capital Holdings Inc [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate, stated percentage	5.00%
Senior Notes Due Twenty Twenty Five [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate, stated percentage	8.625%
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	$ 2,727.7	2,175.2
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	10.1	12.7
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Exchange firm Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	379.4
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	2,464.5	2,125.1
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Exchange firm Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	$ 0	$ 0

Assets and Liabilities, at Fa_4

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated under federal and other regulations	$ 1,920.2	$ 1,049.9
Financial instruments, owned, at fair value	2,727.7	2,175.2
Physical commodities inventory	281.1	229.3
Accounts payable and other accrued liabilities	272.6	157.5
Payable to broker-dealers, clearing organizations and counterparties	537.5	266.2
Financial instruments sold, not yet purchased, at fair value	686	714.8
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	16
Cash and securities segregated under federal and other regulations	2.6	306
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	1,775.8	626.9
Receivables from clients, net - Derivatives	1.5
Financial instruments, owned, at fair value	2,727.7	2,175.2
Total assets at fair value	4,739.3	3,273.8
Payables to clients - Derivatives	(222.7)
Liabilities, fair value disclosure	479.5	722.2
Fair Value, Measurements, Recurring [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	10.2	5.3
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	4.5	0.3
Fair Value, Measurements, Recurring [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	14.7	5.6
Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	1.5	1.8
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	215.7	151.9
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	264.3	168.5
Financial instruments sold, not yet purchased, at fair value	232.9	158.1
Fair Value, Measurements, Recurring [Member] | Corporate and Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	66.9	80
Financial instruments sold, not yet purchased, at fair value	22.5	39.2
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	419.9	248.7
Financial instruments sold, not yet purchased, at fair value	247.5	272.3
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	293.4	447.1
Financial instruments sold, not yet purchased, at fair value	0.1	43.8
Fair Value, Measurements, Recurring [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	2.5	0.5
Fair Value, Measurements, Recurring [Member] | Agency Mortgage-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	1,384.6	1,045
Financial instruments sold, not yet purchased, at fair value	5.1	29.6
Fair Value, Measurements, Recurring [Member] | Asset-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	33	29.1
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	117.4	66.5
Financial instruments sold, not yet purchased, at fair value	176.8	58.1
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	24.9	28.6
Financial instruments sold, not yet purchased, at fair value	1.1	113.7
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	103.2	48.4
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	10.1	12.7
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	7.5	0.1
Fair Value, Measurements, Recurring [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	19.2	8.3
Fair Value, Measurements, Recurring [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	8	9.9
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	1,941.3	593.9
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	(192.7)	14.8
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	2.4	6.2
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated under federal and other regulations	0.2	299.8
Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3.2	4.9
Cash and cash equivalents		13.8
Fair Value, Measurements, Recurring [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	12.8	8.9
Fair Value, Measurements, Recurring [Member] | Netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Cash and securities segregated under federal and other regulations	0	0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	(2,549.3)	(3,161.1)
Receivables from clients, net - Derivatives	(234.1)
Financial instruments, owned, at fair value	(535.6)	(420.8)
Total assets at fair value	(3,319)	(3,581.9)
Payables to clients - Derivatives	(2,399.9)
Financial instruments sold, not yet purchased, at fair value	(386.8)	(422.2)
Liabilities, fair value disclosure	(3,100.7)	(3,540.8)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(11.8)	(1.5)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(302.2)	(3,117.1)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(314)	(3,118.6)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | 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] | Netting [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] | Netting [Member] | Corporate and Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Financial instruments sold, not yet purchased, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Financial instruments sold, not yet purchased, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Financial instruments sold, not yet purchased, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Agency Mortgage-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Financial instruments sold, not yet purchased, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Asset-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	(535.6)	(420.8)
Financial instruments sold, not yet purchased, at fair value	(386.8)	(422.2)
Fair Value, Measurements, Recurring [Member] | Netting [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] | Netting [Member] | Commodities Warehouse Receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Exchange firm Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Mutual Funds and Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	(11.8)	(1.5)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	(2,537.5)	(3,159.6)
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Commodities Warehouse Receipts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated under federal and other regulations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated under federal and other regulations	0	0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Cash and cash equivalents		0
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	16	13.8
Cash and securities segregated under federal and other regulations	2.6	306
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	3,898.3	3,735
Receivables from clients, net - Derivatives	0
Financial instruments, owned, at fair value	798.8	470.9
Total assets at fair value	4,742.5	4,532.8
Payables to clients - Derivatives	2,000.8
Financial instruments sold, not yet purchased, at fair value	465.5	419.6
Liabilities, fair value disclosure	2,466.3	3,498.7
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	3,079.1
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	3,079.1
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	26.8	7.1
Fair Value, Measurements, Recurring [Member] | 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	254.9	159.5
Financial instruments sold, not yet purchased, at fair value	218	147.3
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate and Municipal Bonds [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] | Level 1 [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	419.9	248.7
Financial instruments sold, not yet purchased, at fair value	247.5	272.3
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government Agency Obligations [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] | Level 1 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	2.5	0.5
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Agency Mortgage-backed Obligations [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] | Level 1 [Member] | Asset-backed Obligations [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] | Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	0.7	1
Financial instruments sold, not yet purchased, at fair value		0
Fair Value, Measurements, Recurring [Member] | 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] | 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	103.2	48.4
Fair Value, Measurements, Recurring [Member] | 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	10.1	12.7
Fair Value, Measurements, Recurring [Member] | 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	7.5	0.1
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	8	9.9
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	1,941.3	593.9
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	1,949	3,131.2
Fair Value, Measurements, Recurring [Member] | 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	2.4	6.2
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated under federal and other regulations	0.2	299.8
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3.2	4.9
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	12.8	8.9
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Cash and securities segregated under federal and other regulations	0	0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	426.8	53
Receivables from clients, net - Derivatives	235.6
Financial instruments, owned, at fair value	2,464.5	2,125.1
Total assets at fair value	3,315.8	2,322.9
Payables to clients - Derivatives	176.4
Financial instruments sold, not yet purchased, at fair value	607.3	717.4
Liabilities, fair value disclosure	1,112.4	762.5
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	22	6.8
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	306.7	38.3
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	328.7	45.1
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Physical commodities inventory [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	188.9	144.8
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	9.4	9
Financial instruments sold, not yet purchased, at fair value	14.9	10.8
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	66.9	80
Financial instruments sold, not yet purchased, at fair value	22.5	39.2
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury Obligations [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] | Level 2 [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	293.4	447.1
Financial instruments sold, not yet purchased, at fair value	0.1	43.8
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government Obligations [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] | Level 2 [Member] | Agency Mortgage-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	1,384.6	1,045
Financial instruments sold, not yet purchased, at fair value	5.1	29.6
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Asset-backed Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	33	29.1
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments, owned, at fair value	652.3	486.3
Financial instruments sold, not yet purchased, at fair value	563.6	480.3
Fair Value, Measurements, Recurring [Member] | 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	24.9	28.6
Financial instruments sold, not yet purchased, at fair value	1.1	113.7
Fair Value, Measurements, Recurring [Member] | 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] | 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] | 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] | Level 2 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	31	9.8
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	395.8	43.2
Fair Value, Measurements, Recurring [Member] | 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] | Level 2 [Member] | U.S. Treasury Obligations [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] | Level 2 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Cash and cash equivalents		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Cash and securities segregated under federal and other regulations	0	0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Receivables from clients, net - Derivatives	0
Financial instruments, owned, at fair value	0	0
Total assets at fair value	0	0
Payables to clients - Derivatives	0
Financial instruments sold, not yet purchased, at fair value	0	0
Liabilities, fair value disclosure	1.5	1.8
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities	1.5	1.8
Fair Value, Measurements, Recurring [Member] | 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] | 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] | Level 3 [Member] | Corporate and Municipal Bonds [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] | Level 3 [Member] | U.S. Treasury Obligations [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] | Level 3 [Member] | U.S. Government Agency Obligations [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] | Level 3 [Member] | Foreign Government Obligations [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] | Level 3 [Member] | Agency Mortgage-backed Obligations [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] | Level 3 [Member] | Asset-backed Obligations [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] | 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] | 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] | 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] | 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] | 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] | Level 3 [Member] | TBA and Forward Settling Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign Government Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	0	0
Fair Value, Measurements, Recurring [Member] | 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] | Level 3 [Member] | U.S. Treasury Obligations [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] | Level 3 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Cash and cash equivalents		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 0	$ 0

Financial Instruments with Of_3

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Derivatives, Fair Value [Line Items]
Financial instruments sold, not yet purchased, at fair value	$ 686	$ 714.8
Fair Value, Measurements, Recurring [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Financial instruments sold, not yet purchased, at fair value	$ 176.8	$ 58.1

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) position in Millions, $ in Millions	Sep. 30, 2020USD ($)position	Sep. 30, 2019USD ($)position
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	$ 3,264.4	$ 3,671.5
Derivative liability, fair value, gross liability	3,069.5	3,604.5
Gross fair value of derivative contracts	(3,319)	(3,581.9)
Gross fair value of derivative contracts	$ (3,100.7)	$ (3,540.8)
Derivative, number of instruments held | position	7.9	10.6
Deposits and Receivables from Exchange Clearing Organizations [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	$ (173.5)	$ 23.1
Receivable From Clients, Net [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	1.5	0
Financial Instruments Owned [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	117.4	66.5
Payables To Clients [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	(222.7)	0
Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	14.7	5.6
Financial Instrument Sold, Not Yet Purchased [Member]
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	176.8	58.1
Exchange-traded Commodity Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	1,637.2	1,437.1
Derivative liability, fair value, gross liability	1,747.3	1,463.4
OTC Commodity Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	553.9	84.2
Derivative liability, fair value, gross liability	433.2	106.2
Exchange-traded Foreign Exchange Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	9.3	36.9
Derivative liability, fair value, gross liability	13	33.5
OTC Foreign Exchange Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	520.8	403.2
Derivative liability, fair value, gross liability	461.5	368.8
Exchange-traded interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	271.1	900.1
Derivative liability, fair value, gross liability	200.7	882
OTC Interest Rate Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	96	42.1
Derivative liability, fair value, gross liability	96.6	43.6
Exchange-traded Equity Index Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	32.1	758.1
Derivative liability, fair value, gross liability	39.8	700.2
OTC Equity And Indices Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	113	0
Derivative liability, fair value, gross liability	55.4	0
TBA and Forward Settling Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	31	9.8
Derivative liability, fair value, gross liability	$ 22	$ 6.8

Financial Instruments with Of_5

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - TBAs and Forward Settling Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	$ 3,264.4	$ 3,671.5
Derivative liability, fair value, gross liability	(3,069.5)	(3,604.5)
TBA securities purchased [Member] | Deposits and Receivables from Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	10.8	3.7
Derivative asset, notional amount	(5,389.3)	(1,778.4)
Derivative liability, fair value, gross liability	(1.7)	(0.6)
Derivative liability, notional amount	(2,647.7)	(234.5)
TBA securities sold [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	2.8	0.9
Derivative asset, notional amount	(2,978.7)	(451.6)
Derivative liability, fair value, gross liability	(13)	(5.9)
Derivative liability, notional amount	(6,549.4)	(2,788)
Forward settling securities purchased [Member] | Deposits and Receivables from Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value, gross liability	(7.3)	0
Derivative liability, notional amount	(2,447.1)	0
Forward settling securities purchased [Member] | Payables to Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value, gross liability	0	(0.3)
Derivative liability, notional amount	0	(1,243.5)
Forward settling securities sold [Member] | Deposits and Receivables from Broker-dealers, Clearing Organizations and Counterparties [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	17.4	5.2
Derivative asset, notional amount	$ (1,946)	$ (581.2)

Financial Instruments with Of_6

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Commodities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 197.3	$ 100.8	$ 94
Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	38.2	8.1	9.2
Interest Rate, Equities, and Indices [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	20.4	(2.6)	1
TBA and Forward Settling Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	(49.7)	(35.3)	14.5
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 206.2	$ 71	$ 118.7

Allowance for Doubtful Accoun_3

Allowance for Doubtful Accounts - Narrative (Details) - USD ($)	3 Months Ended				12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts - deposits with and receivables from broker-dealers, clearings organizations, and counterparties	$ 36,900,000				$ 1,300,000	$ 36,900,000
Accounts receivable, allowance for credit loss, write-off					35,600,000	300,000	$ 300,000
Allowance for doubtful accounts receivable	11,700,000				25,800,000	11,700,000
Allowance for doubtful accounts	0				0	0
Provision for bad debts, net of recoveries and impairment					13,000,000	2,500,000	3,100,000
(Recovery) bad debt on physical coal	$ (10,000,000)	$ 0	$ 0	$ (2,400,000)	0	(12,400,000)	1,000,000	$ 47,000,000
Net increase in provision for bad debts						2,600,000	2,900,000
Allowance for doubtful accounts receivable, recoveries						400,000	100,000
Commerical Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for bad debts, net of recoveries and impairment					3,500,000
(Recovery) bad debt on physical coal					3,200,000
Net increase in provision for bad debts						2,700,000	2,800,000
Institutional Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for bad debts, net of recoveries and impairment					5,400,000
Net increase in provision for bad debts						$ 1,400,000	$ 400,000
Retail [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for bad debts, net of recoveries and impairment					$ 600,000

Allowance for Doubtful Accoun_4

Allowance for Doubtful Accounts - Allowance for Bad Debts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of year	$ 48.6	$ 58.2	$ 54.6
Provision (recovery) for bad debts	13	(9.8)	3.9
Allowance charge-offs	(35.6)	(1.3)	(0.3)
Other	1.1	1.5	0
Balance, end of year	$ 27.1	$ 48.6	$ 58.2

Physical Commodities Inventor_2

Physical Commodities Inventory - Physical Commodities Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Inventory [Line Items]
Physical Ag & Energy	$ 201.5	$ 144.8
Precious metals - held by broker -dealer subsidiary	215.7	151.9
Physical commodities inventory	281.1	229.3
Physical Commodities Inventory - Precious Metals [Member]
Inventory [Line Items]
Precious metals - held by broker -dealer subsidiary	14.2	7.1
Precious metals - held by non -broker -dealer subsidiaries	$ 65.4	$ 77.4

Physical Commodities Inventor_3

Physical Commodities Inventory -Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Crude Oil And Low Sulfur Fuel Oil [Member]
Inventory [Line Items]
Inventory adjustments	$ 7.6
Precious Precious Metals Trading [Member]
Inventory [Line Items]
Inventory adjustments	$ 0.7	$ 0.5

Property and Equipment, net - N

Property and Equipment, net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 13.3	$ 11.2	$ 9.4
Impairment charges	$ 5.7
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, useful life	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, useful life	10 years

Property and Equipment, net - A

Property and Equipment, net - Accumulated Depreciation (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment, Net [Abstract]
Furniture and fixtures	$ 10.2	$ 10.6
Software	28.6	33.9
Equipment	30.8	28.1
Leasehold improvements	38.3	20.3
Total property and equipment	107.9	92.9
Less accumulated depreciation	(45.8)	(49)
Property and equipment, net	$ 62.1	$ 43.9

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Line Items]
Remaining excess allocated to goodwill	$ 54.7	$ 51.2
Commercial [Member]
Goodwill [Line Items]
Remaining excess allocated to goodwill	32.7	32.7
Institutional [Member]
Goodwill [Line Items]
Remaining excess allocated to goodwill	9.8	8.7
Retail [Member]
Goodwill [Line Items]
Remaining excess allocated to goodwill	2.2	2.2
Global Payments [Member]
Goodwill [Line Items]
Remaining excess allocated to goodwill	$ 10	$ 7.6

Goodwill - Goodwill Reconciliat

Goodwill - Goodwill Reconciliation (Details) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Goodwill purchase accounting adjustments	$ 100,000	$ 0
GIROXX Gmbh [Member]
Business Acquisition [Line Items]
Remaining excess allocated to goodwill	2,300,000
UOB Bullion and Futures [Member]
Business Acquisition [Line Items]
Remaining excess allocated to goodwill	$ 1,100,000

Intangible Assets - Intangible

Intangible Assets - Intangible Assets Acquired During the Period (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
UOB Bullion and Futures Limited [Member] | Customer Base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 3.1
IFCM Commodities Acquisition [Member] | Customer Base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	1
Quest Capital Strategies Inc [Member] | Customer Base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	1.7
Gain Capital Holdings Inc [Member] | Customer Base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	9.8
Gain Capital Holdings Inc [Member] | Software Programs/Platforms [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	22.2
Gain Capital Holdings Inc [Member] | Trade/Domain Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	3.7
GIROXX [Member] | Software Programs/Platforms [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	1.5
GIROXX [Member] | Business Licenses [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 0.4

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived computer software, gross amount	$ 28.6	$ 33.9
Finite-lived intangible assets, gross amount	70.9	27.4
Finite-lived intangible assets, accumulated amortization	(21.4)	(15.5)
Finite-lived intangible assets, net amount	49.5	11.9
Indefinite-lived intangible assets, gross amount	5.3	4.8
Intangible assets, gross amount	76.2	32.2
Total intangible assets, net amount	54.8	16.7
Website Domains [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived license agreements	2.1	2.1
Business Licenses [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross amount	3.2	2.7
Trade/Domain Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived trade names, gross amount	3.7	0
Finite-lived intangible assets, accumulated amortization	(0.2)	0
Finite-lived intangible assets, net amount	3.5	0
Software Programs/Platforms [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived computer software, gross amount	29	5.3
Finite-lived intangible assets, accumulated amortization	(4.9)	(3)
Finite-lived intangible assets, net amount	24.1	2.3
Customer Base [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived customer lists, gross amount	38.2	22.1
Finite-lived intangible assets, accumulated amortization	(16.3)	(12.5)
Finite-lived intangible assets, net amount	$ 21.9	$ 9.6

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 5.8	$ 2.8	$ 2.3

Intangible Assets - Finite-Li_2

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2021	$ 15.1
Fiscal 2022	13.8
Fiscal 2023	12.2
Fiscal 2024	4.7
Fiscal 2025 and thereafter	3.7
Finite-lived intangible assets, net amount	$ 49.5	$ 11.9

Credit Facilities - Number of C

Credit Facilities - Number of Credit Facilities (Details)	12 Months Ended
	Sep. 30, 2020USD ($)facility	Jun. 11, 2020USD ($)	Sep. 30, 2019USD ($)	Apr. 30, 2015USD ($)
Line of Credit Facility [Line Items]
Number of credit facilities | facility	4
Maximum borrowing capacity under credit facilities	$ 736,600,000
Term of syndicated loan facility	3 years
Maximum available under credit facility	$ 393,000,000
Line of credit facility borrowing	$ 20,000,000
Debt instrument, face amount		$ 350,000,000
Term loan periodic principal payment percentage	1.25%
Term loan periodic payment	$ 9,800,000
Long-term debt, gross	180,100,000
Line of credit facility	0		$ 0
Notes payable to bank	$ 0		400,000	$ 4,000,000
Debt, weighted average interest rate	2.00%
Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Short-term Debt	$ 20,000,000		0
StoneX Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under credit facilities	376,600,000
Line of credit facility borrowing	196,500,000
Debt instrument, face amount	196,500,000
Long-term debt, gross	$ 180,100,000
Line of credit facility, unused capacity, commitment fee percentage	0.625%
Long-term debt	$ 202,500,000		237,600,000
StoneX, Ltd [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing	25,000,000
Line of credit facility	25,000,000		0
StoneX Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing	$ 75,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.50%
Line of credit facility, interest rate at period end	5.25%
Long-term debt	$ 0		0
Line of credit facility	0		0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing	$ 260,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.35%
Line of credit facility	$ 200,100,000		128,500,000
StoneX Financial Inc. Uncommitted Commodities Delivery Line [Domain]
Line of Credit Facility [Line Items]
Line of credit facility borrowing	20,000,000
IFL Uncommitted Line of Credit [Member]
Line of Credit Facility [Line Items]
Short-term Debt	$ 0		$ 3,400,000
Base Rate [Member] | StoneX Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Line of credit facility, interest rate at period end	5.25%
Base Rate [Member] | StoneX, Ltd [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.50%
Base Rate [Member] | StoneX Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Base Rate [Member] | FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, interest rate at period end	3.25%
Eurodollar [Member] | StoneX Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Line of credit facility, interest rate at period end	3.10%
Eurodollar [Member] | FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, interest rate at period end	2.40%

Credit Facilities - Senior Secu

Credit Facilities - Senior Secured Notes due 2025 (Details) - USD ($)	Sep. 01, 2020	Jun. 11, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Debt instrument, face amount		$ 350,000,000
Debt instrument offering price, percentage		98.50%	8.625%
Debt issuance costs, gross			$ 9,500,000
Debt instrument, redemption price, percentage	100.00%	108.625%	100.00%
Debt instrument, redemption price, percentage of principal amount redeemed			40.00%
Debt instrument remaining outstanding			$ 500,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 91,500,000		$ 100,000,000
Debt instrument, redemption price, percentage		100.00%	103.00%
Debt instrument, redemption price, percentage of principal amount redeemed			103.00%
Debt instrument, conversion price (in dollars per share)			$ 6
Senior Notes [Member] | Gain Capital Holdings Inc [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 92,000,000
Debt instrument, interest rate, stated percentage			5.00%

Credit Facilities - Credit Faci

Credit Facilities - Credit Facilities and Financing Bridge Commitment (Details) - USD ($)	Feb. 26, 2020	Sep. 30, 2020	Sep. 30, 2019	Apr. 30, 2015
Line of Credit Facility [Line Items]
Senior secured bridge loan	$ 350,000,000
Non-refundable commitment fee	$ 4,400,000
Long-term debt, gross		$ 180,100,000
Line of credit facility borrowing		20,000,000
Maximum borrowing capacity under credit facilities		736,600,000
Line of credit facility		0	$ 0
Amount outstanding		427,600,000	366,100,000
Notes payable to bank		0	400,000	$ 4,000,000
Senior Secured Notes		336,000,000	0
Lenders under loans		783,600,000	369,900,000
Debt instrument, unamortized discount (premium) and debt issuance costs, net		500,000
StoneX Inc. Bank of America Syndicated Credit Facility [Member]
Line of Credit Facility [Line Items]
Long-term debt, gross		180,100,000
Line of credit facility borrowing		196,500,000
Maximum borrowing capacity under credit facilities		376,600,000
Loans Payable		179,500,000	167,600,000
Long-term line of credit, noncurrent		23,000,000	70,000,000
Long-term debt		202,500,000	237,600,000
StoneX Financial Margin line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing		75,000,000
Long-term debt		0	0
Line of credit facility		0	0
FMS Sub-note commodity line of credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing		260,000,000
Line of credit facility		200,100,000	128,500,000
StoneX, Ltd [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing		25,000,000
Line of credit facility		25,000,000	0
IFFI Uncommitted Lines of Credit [Member] [Member]
Line of Credit Facility [Line Items]
Line of credit facility borrowing		100,000,000
Short-term Debt		0	0
IFL Uncommitted Line of Credit [Member]
Line of Credit Facility [Line Items]
Short-term Debt		0	3,400,000
Rabobank Uncommited Line of Credit [Domain]
Line of Credit Facility [Line Items]
Short-term Debt		20,000,000	$ 0
Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt instrument, unamortized discount (premium) and debt issuance costs, net		14,000,000
Main line of credit facilities [Member]
Line of Credit Facility [Line Items]
Credit Facilities Expiring Within One Year		$ 75,000,000

Commitments and Contingencies -

Commitments and Contingencies - Contingencies and Litigation (Details) $ in Millions	Nov. 16, 2018account	Sep. 30, 2019USD ($)
Other Commitments [Line Items]
Loss contingency, range of possible loss, portion not accrued		$ 29
Maximum amount of individual accounts receivable account		$ 1.4
StoneX Financial [Member]
Other Commitments [Line Items]
Number of accounts | account	300

Commitments and Contingencies_2

Commitments and Contingencies - Purchase Obligations (Details) $ in Millions	Sep. 30, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase obligation, due in next twelve months	$ 5,230.9
Purchase obligation, due in second and third year	19.2
Purchase obligation, due in fourth and fifth year	17.2
Purchase obligation, due after fifth year	3.2
Other commitment, due in next twelve months	$ 5,162.4

Commitments and Contingencies_3

Commitments and Contingencies - Self-Insurance (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Percentage of stop loss actual estimated claims	120.00%
Self insurance reserve and dental claims	$ 1.1	$ 0.8

Regulatory Requirements and S_3

Regulatory Requirements and Subsidiary Dividend Restrictions - Narrative (Details)	12 Months Ended
	Sep. 30, 2020USD ($)
Capital and Other Regulatory Requirements [Line Items]
Adjusted net capital	$ 5,000,000
Net capital under commodity exchange act computation	20,000,000
Required net capital under commodity exchange act	10,000,000
StoneX Financial [Member]
Capital and Other Regulatory Requirements [Line Items]
Adjusted net capital	1,000,000
Adjusted net capital of percentage	$ 0.08
Broker-dealer, minimum net capital required, dividend withdrawal threshold, percent	120.00%
Gain Capital Group, LLC [Member]
Capital and Other Regulatory Requirements [Line Items]
Adjusted net capital	$ 1,000,000
Adjusted net capital of percentage	0.08
Net capital under commodity exchange act computation	$ 71,500,000
Percentage of net capital under commodity exchange act computation	5.00%
Required net capital under commodity exchange act	$ 32,200,000
Percentage of required net capital under commodity exchange act	10.00%

Regulatory Requirements and S_4

Regulatory Requirements and Subsidiary Dividend Restrictions - Customer Reserve Requirements (Details) - USD ($) $ in Millions	Oct. 02, 2020	Sep. 30, 2020
Customer Reserve Requirement [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required		$ 18.5
Customer SRBA [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required		17.3
Customer SRBA [Member] | Subsequent Event [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required and made	$ 6.2
PAB Reserve Requirement [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required		2.2
PAB SRBA [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required		$ 2.1
PAB SRBA [Member] | Subsequent Event [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash reserve deposit required and made	$ 1.1

Regulatory Requirements and S_5

Regulatory Requirements and Subsidiary Dividend Restrictions - Regulatory Capital Requirements (Details) $ in Millions	Sep. 30, 2020USD ($)
StoneX Financial [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	$ 3,089.9
Secured funds	162.6
Minimum regulatory requirement	3,030.6
Secured funds required under commodity exchange act	150.1
Gain Capital Group, LLC [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	340.4
Secured funds	4.3
Minimum regulatory requirement	319.8
Secured funds required under commodity exchange act	2.5
StoneX Financial Ltd. [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	516.5
Minimum regulatory requirement	505.6
Gain Capital U.K. Ltd [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	206.9
Minimum regulatory requirement	205.6
StoneX Financial Pte. Ltd. [Member]
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	340.6
Minimum regulatory requirement	$ 338.9

Regulatory Requirements and S_6

Regulatory Requirements and Subsidiary Dividend Restrictions - Minimum Regulatory Net Capital (Details) $ in Millions	Sep. 30, 2020USD ($)
Capital and Other Regulatory Requirements [Line Items]
Actual	$ 20
Minimum Requirement	10
StoneX Financial Inc. [Member]
Capital and Other Regulatory Requirements [Line Items]
Actual	229.8
Minimum Requirement	137.6
StoneX Financial Ltd. [Member]
Capital and Other Regulatory Requirements [Line Items]
Actual	264.3
Minimum Requirement	145.1
Gain Capital Group, LLC [Member]
Capital and Other Regulatory Requirements [Line Items]
Actual	71.5
Minimum Requirement	32.2
Gain Capital U.K. Ltd [Member]
Capital and Other Regulatory Requirements [Line Items]
Actual	185.4
Minimum Requirement	$ 65.2

Securities and Commodity Fina_3

Securities and Commodity Financing Transactions - Fair Value of Securities Accepted or Pledged as Collateral (Details) - USD ($)	Sep. 30, 2020	Sep. 30, 2019
Brokers and Dealers [Abstract]
Financial instruments owned and pledged as collateral, amount eligible to be repledged by counterparty	$ 468,600,000	$ 478,800,000
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	1,266,400,000	1,228,900,000
Pledged assets separately reported, securities Pledged for repurchase agreements, at fair value	1,484,700,000	1,175,100,000
Securities loaned, fair value of collateral	1,410,300,000	1,414,000,000
Fair value of securities received as collateral that can be resold or repledged	3,303,100,000	3,060,200,000
Fair value of securities received as collateral that have been resold or repledged	$ 285,700,000	$ 329,800,000

Securities and Commodity Fina_4

Securities and Commodity Financing Transactions (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	$ 3,155.5	$ 2,773.7
Securities loaned	1,441.9	1,459.9
Gross amount of secured financing	4,597.4	4,233.6
Securities purchased under agreements to resell, gross	1,696.2	1,474.4
Securities borrowed, gross	1,440	1,423.2
Securities sold under agreements to repurchase, gross	3,155.5	2,823.6
Securities loaned, gross	1,441.9	1,459.9
Securities Purchased under Agreements to Resell, Offset	0	(49.9)
Securities borrowed, Offset	0	0
Securities sold under agreements to repurchase, Offset	0	(49.9)
Securities loaned, Offset	0	0
Securities purchased under agreements to resell	1,696.2	1,424.5
Securities borrowed	1,440	1,423.2
U.S. Treasury Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	815.8	108.8
U.S. Government Agency Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	279.5	359.5
Asset-backed Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	18	96.7
Agency Mortgage-backed Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,990	2,208.7
Corporate Bonds [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	52.2	0
Equity Securities [Member]
Securities Financing Transaction [Line Items]
Securities loaned	1,441.9	1,459.9
Overnight and Open [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,736.3	1,553.9
Securities loaned	1,441.9	1,459.9
Gross amount of secured financing	3,178.2	3,013.8
Less than 30 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,069.2	565.8
Securities loaned	0	0
Gross amount of secured financing	1,069.2	565.8
30-90 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	325	654
Securities loaned	0	0
Gross amount of secured financing	325	654
Over 90 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	25	0
Securities loaned	0	0
Gross amount of secured financing	$ 25	$ 0

Share-Based Compensation - Shar

Share-Based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Allocated share-based compensation expense	$ 10.3	$ 8.1	$ 6.6

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Plan (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares)	2,000,000
Stock options authorized (in shares)	724,483	692,652
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value (in dollar per share)	$ 0	$ 10.47	$ 9.79
Employee service share-based compensation, non vested awards, total compensation cost not yet recognized, stock options	$ 7.2
Employee service share-based compensation, non vested awards, total compensation cost not yet recognized, period for recognition	5 years 4 months 6 days
Share-based compensation arrangement by share-based payment award, options, exercises in period, total intrinsic value	$ 4.2	$ 0.7	$ 2.1

Share-Based Compensation - St_2

Share-Based Compensation - Stock Option Plan Fair Value Weighted-Average Assumptions (Details) - shares	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Expected stock price volatility	0.00%	27.00%	30.00%
Expected dividend yield	0.00%	0.00%	0.00%
Risk free interest rate	0.00%	1.86%	1.23%
Average expected life	0 years	6 years 18 days	3 years 21 days
Stock options granted (in shares)	0

Share-Based Compensation - St_3

Share-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Shares available for grant, Beginning (in shares)	692,652
Share-based compensation arrangement by share-based payment award, options, forfeitures in period (in shares)	(13,662)
Share-based compensation arrangement by share-based payment award, options, Expirations (in shares)	(18,169)
Shares available for grant, Ending (in shares)	724,483	692,652
Number of Options Outstanding
Number of options outstanding, Beginning (in shares)	1,684,378
Number of options outstanding, Exercised (in shares)	(244,511)
Number of options outstanding, Ending (in shares)	1,408,036	1,684,378
Number of options outstanding, Exercisable (in shares)	423,112
Weighted Average  Exercise Price
Weighted average  exercise price, Beginning (in dollar per share)	$ 38.79	$ 37.59
Weighted average  exercise price, Exercise (in dollar per share)	30.56
Weighted average  exercise price, Forfeited (in dollar per share)	39.64
Weighted average  exercise price, Expired (in dollar per share)	37.30
Weighted average  exercise price, Exercisable (in dollar per share)	29.25
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, Beginning (in dollar per share)	11.32
Weighted average grant date fair value, Exercised (in dollar per share)	11.36
Weighted average grant date fair value, Forfeited (in dollar per share)	8.62
Weighted average grant date fair value, Expired (in dollar per share)	8.19
Weighted average grant date fair value, Ending (in dollar per share)	11.38	$ 11.32
Weighted average grant date fair value, Exercisable (in dollar per share)	$ 12.64
Stock Option Activity, Additional Disclosures
Weighted average remaining term (in years)	4 years 1 month 28 days	4 years 7 months 13 days
Weighted average remaining term (in years), Exercisable	1 year 4 months 17 days
Aggregate intrinsic value	$ 17.4	$ 9.2
Aggregate intrinsic value, Exercisable	$ 9.3

Share-Based Compensation - Opti

Share-Based Compensation - Options by Exercise Price (Details)	12 Months Ended
	Sep. 30, 2020$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of outstanding options (in share) | shares	1,408,036
Weighted average exercise price (in dollars per share)	$ 38.79
Weighted average remaining term (in years)	4 years 1 month 28 days
$0 - $5,00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 0
Exercise price range, upper range limit	$ 5
Number of outstanding options (in share) | shares	0
$5.00 - $10.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 5
Exercise price range, upper range limit	$ 10
Number of outstanding options (in share) | shares	0
$10.00 - $15.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 10
Exercise price range, upper range limit	$ 15
Number of outstanding options (in share) | shares	0
$15.00 - $20.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 15
Exercise price range, upper range limit	$ 20
Number of outstanding options (in share) | shares	0
$20.00 - $25.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 20
Exercise price range, upper range limit	$ 25
Number of outstanding options (in share) | shares	0
$25.00 - $30.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 25
Exercise price range, upper range limit	$ 30
Number of outstanding options (in share) | shares	420,000
Weighted average exercise price (in dollars per share)	$ 25.91
Weighted average remaining term (in years)	1 year 4 months 9 days
$30.00 - $35.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 30
Exercise price range, upper range limit	$ 35
Number of outstanding options (in share) | shares	0
$35.00 - $40.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 35
Exercise price range, upper range limit	$ 40
Number of outstanding options (in share) | shares	126,161
Weighted average exercise price (in dollars per share)	$ 39.65
Weighted average remaining term (in years)	2 years 7 days
$40.00 - $45.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 40
Exercise price range, upper range limit	$ 45
Number of outstanding options (in share) | shares	859,875
Weighted average exercise price (in dollars per share)	$ 44.92
Weighted average remaining term (in years)	5 years 10 months 2 days
$45.00 - $50.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 45
Exercise price range, upper range limit	$ 50
Number of outstanding options (in share) | shares	0
$50.00 - $55.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 50
Exercise price range, upper range limit	$ 55
Number of outstanding options (in share) | shares	0
$55.00 - $60.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit	$ 55
Exercise price range, upper range limit	$ 60
Number of outstanding options (in share) | shares	2,000
Weighted average exercise price (in dollars per share)	$ 55.28
Weighted average remaining term (in years)	1 year 10 months 20 days

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Plan (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)shares
Share-based Payment Arrangement [Abstract]
Share-based compensation arrangement by share-based payment award, shares issued in period (in shares)	1,500,000
Share-based compensation arrangement by share-based payment award, non-option equity instruments, granted (in shares)	900,000
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized | $	$ 15.6
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition - restricted stock	1 year 4 months 13 days

Share-Based Compensation - Re_2

Share-Based Compensation - Restricted Stock Plan Table (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Shares Available for Grant
Shares Available for Grant, Beginning (in shares)	1,156,902
Shares Available for Grant, Granted	299,858
Shares Available for Grant, Forfeited	4,410
Shares Available for Grant, Ending (in shares)	861,454	1,156,902
Number of Shares Outstanding
Number of Shares Outstanding, Beginning (in shares)	350,778
Number of Shares Outstanding, Granted	299,858
Number of Shares Outstanding, Vested (in shares)	(161,880)
Number of Shares Outstanding, Forfeited (in shares)	(4,410)
Number of Shares Outstanding, Ending (in shares)	484,346	350,778
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning (in dollar per share)	$ 40.06
Weighted Average Grant Date Fair Value, Granted (in dollar per share)	44.94
Weighted Average Grant Date Fair Value, Vested (in dollar per share)	40.26
Weighted Average Grant Date Fair Value, Forfeited (in dollar per share)	44.23
Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$ 42.97	$ 40.06
Stock Option Activity, Additional Disclosures
Weighted Average Remaining Term (in years)	1 year 4 months 13 days	1 year 4 months 9 days
Aggregate Intrinsic Value	$ 24.8	$ 14.4

Retirement Plans Retirement Pla

Retirement Plans Retirement Plans - Defined Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit	$ 0.4	$ 0.1	$ 0.2
Expected long-term return	4.35%
Defined benefit plan contributions	$ 0.1	0.1
Defined benefit plan, expected future benefit payment, year one	2.1
Defined benefit plan, expected future benefit payment, year two	2.1
Defined benefit plan, expected future benefit payment, year three	2.1
Defined benefit plan, expected future benefit payment, year four	2.1
Defined benefit plan, expected future benefit payment, year five	2
Defined benefit plan, expected future benefit payment, five fiscal years thereafter	$ 9.5
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, actual allocation, percentage	80.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, actual allocation, percentage	20.00%
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 40.8	38.9
Defined benefit plan, benefit obligation	$ 38.1	$ 36.5
Defined benefit plan, assumptions used calculating benefit obligation, discount rate	2.55%	3.10%
Defined benefit plan, funded (unfunded) status of plan	$ 2.7	$ 2.4
Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0.1	0.1
Defined benefit plan, benefit obligation	1.6	1.7
Defined benefit plan, funded (unfunded) status of plan	$ (1.6)	$ (1.6)

Retirement Plans Retirement P_2

Retirement Plans Retirement Plans - Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer discretionary contribution amount	$ 10.1	$ 7.5	$ 6.8
401k Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay	62.50%
Defined contribution plan, employers matching contribution, annual vesting percentage	8.00%
Defined contribution plan, employers matching contribution, annual vesting percentage, two to three years	33.00%
Defined contribution plan, employers matching contribution, annual vesting percentage, three to four years	66.00%
Defined contribution plan, employers matching contribution, annual vesting percentage, all years	100.00%
401k Plan [Member] | Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, maximum annual contributions per employee, percent	1.00%
401k Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, maximum annual contributions per employee, percent	80.00%
UK Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employers matching contribution, annual vesting percentage	100.00%
UK Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay	10.00%

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Other Expenses [Abstract]
Insurance	$ 4.7	$ 3.4	$ 2.6
Office supplies and printing	1.8	1.9	1.7
Other clearing related expenses	2.8	2.5	2.5
Other non-income taxes	6.6	4.6	4.9
Contingent consideration, net	0.5	0	0
Other	13.2	10.8	8.4
Total other expenses	$ 29.6	$ 23.2	$ 20.1

Bad Debt on Physical Coal (Deta

Bad Debt on Physical Coal (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Bad Debt on Physical Coal [Abstract]
Allowance for doubtful accounts	$ (10)	$ 0	$ 0	$ (2.4)	$ 0	$ (12.4)	$ 1	$ 47
Payments for legal settlements						8.4
Gain (loss) related to litigation settlement						2.4
Insurance recoveries						10
Accounts receivable, allowance for doubtful accounts					$ 35.6	$ 0.3	$ 0.3

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating Loss Carryforwards [Line Items]
Federal statutory rate effect of:	21.00%	21.00%	24.50%
Effective income tax rate reconciliation, Change in enacted tax rate, amount			$ 8.6
Remeasurement of deferred tax	0.00%	0.00%	8.50%
Effective income tax rate reconciliation, Repatriation of foreign earnings, amount			$ 11.2
Repatriation transition tax	0.00%	0.00%	11.00%
Operating loss carryforwards	$ 6.9	$ 7.1
State and local net operating loss carryforwards of net of valuation allowance	4.7
Federal operating loss carryforwards, net of valuation allowances	0.6
Foreign tax credit carryforwards	2.4	5	$ 5.1
Valuation allowance	(12.4)	(8.5)
Net change in total valuation allowance	3.9
Foreign earnings repatriated	30	$ 13
Gain Capital Holdings Inc [Member]
Operating Loss Carryforwards [Line Items]
Foreign tax credit carryforwards	1.1
Foreign tax credits, net	1.3
Gain Capital U.K. Ltd [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 0.9

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax expense attributable to income from operations	$ 2.5	$ 12.4	$ 16.8	$ 5.4	$ 6.9	$ 5.3	$ 7.5	$ 6.2	$ 37.1	$ 25.9	$ 46
Taxes allocated to stockholders’ equity, related to pension liabilities									0	(0.2)	0.1
Total income tax expense									$ 37.1	$ 25.7	$ 46.1

Income Taxes - Current and Defe

Income Taxes - Current and Deferred Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Current taxes:
Total current taxes									$ 33	$ 22.2	$ 23.7
Deferred taxes									4.1	3.7	22.3
Income tax expense	$ 2.5	$ 12.4	$ 16.8	$ 5.4	$ 6.9	$ 5.3	$ 7.5	$ 6.2	37.1	25.9	46
United States [Member]
Current taxes:
U.S. federal									(0.6)	(1.9)	0.8
U.S. State and local									2.3	(0.8)	0.5
Non-US [Member]
Current taxes:
International									$ 31.3	$ 24.9	$ 22.4

Income Taxes - U.S. and Interna

Income Taxes - U.S. and International Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating Loss Carryforwards [Line Items]
Income from operations, before tax	$ 206.7	$ 111	$ 101.5
United States [Member]
Operating Loss Carryforwards [Line Items]
U.S.	88.8	(2.6)	9.9
Non-US [Member]
Operating Loss Carryforwards [Line Items]
International	$ 117.9	$ 113.6	$ 91.6

Income Taxes - Effective Rate R

Income Taxes - Effective Rate Reconciliation (Details)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Operating Loss Carryforwards [Line Items]
Federal statutory rate effect of:	21.00%	21.00%	24.50%
U.S. State and local income taxes	1.00%	(1.50%)	0.80%
Foreign earnings and losses taxed at different rates	0.10%	0.70%	(0.80%)
U.S. permanent items	0.90%	0.10%	(0.20%)
Foreign permanent items	0.50%	0.70%	2.10%
U.S. bargain purchase gain	(8.30%)	(1.00%)	0.00%
Remeasurement of deferred tax	0.00%	0.00%	8.50%
Repatriation Transition tax	0.00%	0.00%	11.00%
GILTI	0.70%	2.20%	0.00%
Other reconciling items	0.90%	(0.40%)	0.20%
Effective rate	18.00%	23.30%	45.30%
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Change in foreign and state valuation allowance	1.00%	1.00%	(0.80%)
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Change in foreign and state valuation allowance	0.20%	0.50%	0.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Deferred tax assets:
Share-based compensation	$ 3.1	$ 3.3
Deferred compensation	4.1	3.6
Intangible assets	9.9	4.8
Bad debt reserve	4.4	1.3
Tax credit carryforwards	0.2	0.5
Foreign tax credit carryforwards	2.4	5	$ 5.1
Other compensation	5.8	2.2
Property and equipment	7.3	0
Other	1.9	1.1
Total gross deferred tax assets	55.3	34.7
Less valuation allowance	(12.4)	(8.5)
Deferred tax assets	42.9	26.2
Deferred income tax liabilities:
Unrealized gain on securities	2.4	3.2
Prepaid expenses	3.4	2.2
Property and equipment	0	2.6
Pension liability	0.2	0.2
Deferred income tax liabilities	6	8.2
Deferred income taxes, net	36.9	18
Non-US [Member]
Deferred tax assets:
Foreign net operating loss carryforwards	5.4	2.6
United States [Member]
Deferred tax assets:
U.S. State and local net operating loss carryforwards	9	9.2
U.S. federal net operating loss carryforwards	$ 1.8	$ 1.1

Acquisitions - Gain Capital Hol

Acquisitions - Gain Capital Holdings Inc (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 26, 2020	Sep. 30, 2020	Sep. 30, 2019
Aggregated Merger Consideration
Common stock outstanding (in shares)		19,376,594	19,075,360
Gain Capital Holdings Inc [Member]
Aggregated Merger Consideration
Common stock outstanding (in shares)	3,600,000
Gain Capital Holdings Inc [Member]
Business Acquisition [Line Items]
Business acquisition, share price (in dollars per share)	$ 6
Aggregated Merger Consideration
Aggregate cash consideration	$ 215
Accrual for merger cash consideration	21.6
Total merger consideration	$ 236.6
Business acquisition, cost incurred related to merger		$ 5.2

Acquisitions - Gain Capital H_2

Acquisitions - Gain Capital Holdings Inc Preliminary Purchase Price Allocation (Details) - USD ($) $ in Millions	Feb. 26, 2020	Sep. 30, 2020	Mar. 31, 2019	Sep. 30, 2020	Sep. 01, 2020
Preliminary Purchase Price Allocation
Bargain purchase gain		$ 81.8	$ 5.4
Acquired finite-lived intangible asset, weighted average useful life				1 year
Gain Capital Holdings Inc [Member]
Preliminary Purchase Price Allocation
Cash and cash equivalents	$ 507.2
Cash, securities and other assets segregated under federal and other regulations	497.4
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	249.7
Receivables from clients, net	2
Income taxes receivable	0.4
Deferred income taxes, net	23
Property and equipment, net	6.1
Right of use assets, net	15
Other assets	17.9
Total fair value of tangible assets acquired	1,318.7
Accounts payable and other accrued liabilities	52.7
Operating lease liabilities	15
Payable to clients	863.4
Payable to broker-dealers, clearing organizations, and counterparties	0.5
Income taxes payable	12.4
Convertible senior notes	92
Total fair value of tangible liabilities assumed	1,036
Fair value of tangible net assets acquired (4)	282.7
Identifiable intangible assets acquired	35.7
Fair value of identifiable net assets acquired	318.4
Total merger consideration	236.6
Bargain purchase gain	81.8
Business combination, convertible senior notes redeemed amount					$ 91.5
Gain Capital Holdings Inc [Member] | Trademarks /Domain Names [Member]
Preliminary Purchase Price Allocation
Identifiable intangible assets acquired	$ 3.7
Acquired finite-lived intangible asset, weighted average useful life	5 years
Gain Capital Holdings Inc [Member] | Software Programs/Platforms [Member]
Preliminary Purchase Price Allocation
Identifiable intangible assets acquired	$ 22.2
Acquired finite-lived intangible asset, weighted average useful life	3 years
Gain Capital Holdings Inc [Member] | Customer base [Member]
Preliminary Purchase Price Allocation
Identifiable intangible assets acquired	$ 9.8
Acquired finite-lived intangible asset, weighted average useful life	4 years

Acquisitions - Gain Capital H_3

Acquisitions - Gain Capital Holdings Inc Post Acquisition Results and Unaudited Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Total revenues	$ 14,284.9	$ 8,243.4	$ 20,366.3	$ 11,245	$ 11,279.6	$ 7,873	$ 7,192.2	$ 6,552.2	$ 54,139.6	$ 32,897	$ 27,622.7
Net income									169.6	85.1	$ 55.5
Gain Capital Holdings Inc [Member]
Business Acquisition [Line Items]
Total revenues									49
Net income									1.8
Business Acquisition, Pro Forma Information [Abstract]
Total revenues									54,414.1	33,160
Net income									$ 138.5	$ 38.3
Basic earnings per share (in dollars per share)									$ 7.17	$ 2.01
Diluted earnings per share (in dollars per share)									$ 7.02	$ 1.97

Acquisitions - UOB Bullion and

Acquisitions - UOB Bullion and Futures Limited (Details) - USD ($) $ in Millions	Oct. 07, 2019	Mar. 31, 2019	Oct. 07, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Purchase price allocated to goodwill				$ 54.7	$ 51.2
Acquired finite-lived intangible asset, weighted average useful life				1 year
UOB Bullion and Futures Limited [Member]
Business Acquisition [Line Items]
Purchase price	$ 2.5	$ 2.5	$ 5
Payable to clients	351.8		351.8
Purchase price allocated to property and equipment acquired	0.8
Purchase price allocated to client base intangible assets acquired	3.1
Purchase price allocated to goodwill	$ 1.1		$ 1.1
Operating revenues post-acquisition results of the acquired business				$ 10.3
Net income (loss) post-acquisition results of the acquired business				$ (1.4)
UOB Bullion and Futures Limited [Member] | Client Base Intangible Assets [Member]
Business Acquisition [Line Items]
Acquired finite-lived intangible asset, weighted average useful life	5 years

Acquisitions - Tellimer (Detail

Acquisitions - Tellimer (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020
Exotix Partners, LLP [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Tellimer [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Purchase price	$ 4.7
Cash and cash equivalents	1
Receivables from clients	1
Property and equipment, net	0.3
Other assets	3.4
Liabilities assumed	$ 1
Operating revenues post-acquisition results of the acquired business		$ 5.9
Net income (loss) post-acquisition results of the acquired business		$ 0.1

Acquisitions - IFCM Commodities

Acquisitions - IFCM Commodities (Details) - IFCM Commodities Acquisition [Member] - USD ($) $ in Millions	Jan. 02, 2020	Sep. 30, 2020
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Purchase price	$ 1.9
Business acquisition, premium amount	$ 1
Operating revenues post-acquisition results of the acquired business		$ 1.8
Net income (loss) post-acquisition results of the acquired business		$ 0.5

Acquisitions - GIROXX (Details)

Acquisitions - GIROXX (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Remaining excess allocated to goodwill		$ 54.7	$ 51.2
Acquired finite-lived intangible asset, weighted average useful life		1 year
GIROXX [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Purchase price	$ 4.4
Cash and cash equivalents	6.5
Property and equipment, net	0.1
Accounts payable and other accrued liabilities	0.6
Payable to clients	5.8
Remaining excess allocated to goodwill	$ 2.3
Operating revenues post-acquisition results of the acquired business		$ 0.5
Net income (loss) post-acquisition results of the acquired business		0.6
GIROXX [Member] | Licensing Agreements [Member]
Business Acquisition [Line Items]
Purchase price allocated to client base intangible assets acquired		0.4
GIROXX [Member] | Software Development [Member]
Business Acquisition [Line Items]
Purchase price allocated to client base intangible assets acquired		$ 1.5
Acquired finite-lived intangible asset, weighted average useful life	3 years

Acquisitions - Quest Capital an

Acquisitions - Quest Capital and Carl Kliem S.A. (Details) $ in Millions	Nov. 30, 2018USD ($)employeeclient	Aug. 31, 2019USD ($)	Sep. 30, 2020USD ($)employee	Mar. 31, 2019USD ($)	Sep. 30, 2019USD ($)
Business Acquisition [Line Items]
Number of employees | employee			2,900
Bargain purchase gain			$ 81.8	$ 5.4
Quest Capital Strategies Inc [Member]
Business Acquisition [Line Items]
Purchase price		$ 1.7
Carl Kliem S.A. [Member]
Business Acquisition [Line Items]
Number of employees | employee	40
Number of clients | client	400
Purchase price	$ 2.1
Cash and cash equivalents	1.7
Receivables from clients	1.1
Property and equipment, net	0.1
Income tax receivable	0.1
Accounts payable and other accrued liabilities	0.6
Payable to clients	$ 0.2
Bargain purchase gain					$ 0.1
Operating revenues post-acquisition results of the acquired business					4.2
Net income (loss) post-acquisition results of the acquired business					$ 2.3

Acquisitions - GMP Securities,

Acquisitions - GMP Securities, LLC (Details) - USD ($) $ in Millions	Jan. 14, 2019	Sep. 30, 2020	Mar. 31, 2019	Sep. 30, 2019
Net assets acquired based on fair values:
Bargain purchase gain		$ 81.8	$ 5.4
GMP Securities Acquisition [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Total merger consideration	$ 8.2
Business combination, excess amount above book value of tangible assets acquired	2
Operating revenues post-acquisition results of the acquired business				$ 8.2
Net income (loss) post-acquisition results of the acquired business				2.1
Net assets acquired based on fair values:
Cash and cash equivalents	1.1
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	7.7
Financial instruments owned, at fair value	7.1
Deferred income taxes, net	2.7
Property and equipment	0.7
Other assets	0.7
Total fair value of tangible assets acquired	20
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	4.4
Total fair value of tangible liabilities assumed	6.4
Fair value of identifiable net assets acquired	13.6
Purchase price	8.2
Bargain purchase gain	$ 5.4			$ 5.4

Acquisitions - Coininvest and E

Acquisitions - Coininvest and European Precious Metal Trading Acquisitions (Details) - USD ($) $ in Millions	Apr. 01, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Acquired finite-lived intangible asset, weighted average useful life		1 year
Net assets acquired based on fair values:
Goodwill		$ 54.7	$ 51.2
Coininvest and EPMT Acquisitions [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Total merger consideration	$ 22
Purchase of shareholders equity interest	$ 11.2
Operating revenues post-acquisition results of the acquired business			0.6
Acquired finite-lived intangible asset, weighted average useful life	5 years
Net income (loss) post-acquisition results of the acquired business			$ 0.3
Net assets acquired based on fair values:
Cash and cash equivalents	$ 2
Receivables from clients	1.2
Receivable from affiliate	1.1
Income tax receivable	0.1
Physical commodities inventory	9.8
Deferred tax assets, net	0.2
Other assets	1.2
Total fair value of tangible assets acquired	15.6
Accounts payable and other accrued liabilities	0.2
Payable to clients	0.2
Total fair value of tangible liabilities assumed	0.4
Fair value of identifiable net assets acquired	15.2
Purchase price	22
Total fair value of tangible assets acquired	6.8
Domain names	2.1
Identifiable intangible assets acquired	2.5
Total excess purchase price allocated to identifiable intangible assets	4.6
Goodwill	$ 2.2

Acquisitions - Fillmore Advisor

Acquisitions - Fillmore Advisors, LLC Acquisition (Details) - USD ($) $ in Millions	Sep. 01, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Acquired finite-lived intangible asset, weighted average useful life		1 year
Preliminary Purchase Price Allocation
Goodwill		$ 54.7	$ 51.2
Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Percentage of stock purchased	100.00%
Aggregate cash consideration	$ 1.4
Percentage of contingent earn-out payments	50.00%
Fair value of contingent consideration	$ 1.8
Acquired finite-lived intangible asset, weighted average useful life	5 years
Preliminary Purchase Price Allocation
Cash and cash equivalents	$ 0.2
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties	0.3
Receivables from clients	0.2
Other assets	0.4
Total fair value of tangible assets acquired	1.1
Accounts payable and other accrued liabilities	0.5
Total fair value of tangible liabilities assumed	0.5
Fair value of identifiable net assets acquired	0.6
Purchase price	3.2
Total fair value of tangible assets acquired	2.6
Purchase price allocated to client base intangible assets acquired	0.7
Total excess purchase price allocated to identifiable intangible assets	0.7
Goodwill	1.9
Cash [Member] | Fillmore Advisors, LLC [Member]
Business Acquisition [Line Items]
Fair value of contingent consideration	$ 1.8

Acquisitions - PayCommerce Fina

Acquisitions - PayCommerce Financial Solutions Acquisition (Details) - USD ($)	Feb. 13, 2019	Sep. 05, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Goodwill purchase accounting adjustments			$ 100,000	$ 0
PayCommerce [Member]
Business Acquisition [Line Items]
Total merger consideration		$ 3,800,000
Income tax receivable		700,000
Property and equipment, net		800,000
Total fair value of tangible liabilities assumed		2,200,000
Identifiable intangible assets acquired		$ 1,300,000
Finite-lived intangible asset, useful life		5 years
Remaining excess allocated to goodwill					$ 2,600,000
Akshay Financeware, Inc. Acquisition [Member]
Business Acquisition [Line Items]
Total merger consideration	$ 200,000
Equity investment related to a minority interest in the joint venture entity		$ 500,000
Remaining excess allocated to goodwill				$ 1,300,000
Purchase of shareholders equity interest	500,000
Indefinite-lived intangible assets acquired	2,700,000
Deferred tax liabilities	700,000
Goodwill purchase accounting adjustments	$ 1,300,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 594.2	$ 505.3	$ 449.9
Other comprehensive loss	(4.7)
Amounts reclassified from AOCI, net of tax	0.1	(0.1)	0.1
Other comprehensive loss	(4.6)	(1.7)	(8.6)
Ending balance	767.5	594.2	505.3
Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	594.2
Ending balance		594.2
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(31.5)
Other comprehensive loss	(4.5)
Amounts reclassified from AOCI, net of tax	0
Other comprehensive loss	(4.5)
Ending balance	(36)	(31.5)
Foreign Currency Translation Adjustment | Cumulative Effect, Period of Adoption, Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0
Ending balance		0
Foreign Currency Translation Adjustment | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(31.5)
Ending balance		(31.5)
Pension Benefits Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3.3)
Other comprehensive loss	(0.2)
Amounts reclassified from AOCI, net of tax	0.1
Other comprehensive loss	(0.1)
Ending balance	(4.1)	(3.3)
Pension Benefits Adjustment | Cumulative Effect, Period of Adoption, Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(0.7)
Ending balance		(0.7)
Pension Benefits Adjustment | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4)
Ending balance		(4)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(34.8)	(33.1)	(24.5)
Ending balance	(40.1)	(34.8)	$ (33.1)
Accumulated Other Comprehensive Loss | Cumulative Effect, Period of Adoption, Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(0.7)
Ending balance		(0.7)
Accumulated Other Comprehensive Loss | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (35.5)
Ending balance		$ (35.5)

Segment and Geographic Inform_3

Segment and Geographic Information - Additional Information (Details) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020USD ($)employeecountrymarket	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2020USD ($)employeecurrencymarketcountry	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Number of employees | employee	2,900								2,900
Number of countries in which entity operates (more than) | country	180								180
Total revenues	$ 14,284.9	$ 8,243.4	$ 20,366.3	$ 11,245	$ 11,279.6	$ 7,873	$ 7,192.2	$ 6,552.2	$ 54,139.6	$ 32,897	$ 27,622.7
Operating revenues	342.1	322.6	366.8	276.8	286.9	283.4	271.1	264.7	1,308.3	1,106.1	975.8
Net operating revenues (loss):	226.2	227.9	243.4	170.5	173.4	165.6	165.2	149	868	653.2	581.6
Net contribution:									639.5	482.8	432.4
Segment income (loss):									395.1	305.7	261.9
Net costs not allocated to operating segments									(270.3)	(200.2)	(162.4)
Gain on acquisitions and other gains									81.9	5.5	2
Income before tax	79.9	$ 49	$ 56.1	$ 21.7	34.1	21.6	30.9	24.4	206.7	111	101.5
(Recovery) bad debt on physical coal					(10)	$ 0	$ 0	$ (2.4)	0	(12.4)	1	$ 47
Total assets:	13,474.9				9,936.1				13,474.9	9,936.1	7,824.7
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									14.6	20.8	23.9
Operating revenues									14.6	20.8	23.9
Net operating revenues (loss):									(24.5)	(10.8)	(0.3)
Total assets:	418.7				147.9				418.7	147.9	100.5
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues									(19.3)	(25.1)	(19.5)
Operating revenues									(19.3)	(25.1)	(19.5)
Commercial [Member]
Segment Reporting Information [Line Items]
Net contribution:									242.2	224.6	210
Segment income (loss):									141.9	144.6	118.3
Commercial [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									52,970.1	32,125.4	27,018.7
Operating revenues									431.5	404.4	371.8
Net operating revenues (loss):									353.4	321.2	299.4
Total assets:	2,753.6				2,386.4				2,753.6	2,386.4	2,349.5
Institutional [Member]
Segment Reporting Information [Line Items]
Net contribution:									248.9	157	135.6
Segment income (loss):									152.9	88.6	78.2
Institutional [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									624.1	515	427.1
Operating revenues									624.1	515	427.1
Net operating revenues (loss):									363.8	220.1	176.3
Total assets:	$ 8,740.8				7,111.2				$ 8,740.8	7,111.2	5,168.1
Retail [Member]
Segment Reporting Information [Line Items]
Number of countries in which entity operates (more than) | country	130								130
Number of global financial markets | market	15,000								15,000
Net contribution:									$ 58.8	14.6	11.8
Segment income (loss):									31.7	6.4	5.6
Retail [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									432.7	148.1	73.3
Operating revenues									140	78.2	73.3
Net operating revenues (loss):									63.8	15.7	12.7
Total assets:	$ 1,245.9				12.4				$ 1,245.9	12.4	0
Global Payments [Member]
Segment Reporting Information [Line Items]
Number of countries in which entity operates (more than) | country	170								170
Number of different types of foreign currencies (more than) | currency									140
Net contribution:									$ 89.6	86.6	75
Segment income (loss):									68.6	66.1	59.8
Global Payments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues									117.4	112.8	99.2
Operating revenues									117.4	112.8	99.2
Net operating revenues (loss):									111.5	107	93.5
Total assets:	$ 315.9				$ 278.2				$ 315.9	$ 278.2	$ 206.6

Segment and Geographic Inform_4

Segment and Geographic Information - Total Revenues by Geographic Location (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Total revenues	$ 14,284.9	$ 8,243.4	$ 20,366.3	$ 11,245	$ 11,279.6	$ 7,873	$ 7,192.2	$ 6,552.2	$ 54,139.6	$ 32,897	$ 27,622.7
Operating revenues:	342.1	$ 322.6	$ 366.8	$ 276.8	286.9	$ 283.4	$ 271.1	$ 264.7	1,308.3	1,106.1	975.8
Long-lived assets, as defined:	62.1				43.9				62.1	43.9	42.4
United States [Member]
Total revenues									2,223.3	1,947.6	1,587.6
Operating revenues:									928.3	799.4	695.3
Long-lived assets, as defined:	55.4				33.9				55.4	33.9	33
Europe [Member]
Total revenues									532.6	280.2	189.6
Operating revenues:									237.9	209.6	189
Long-lived assets, as defined:	3.1				6.6				3.1	6.6	6.8
South America [Member]
Total revenues									58.9	56.5	59.5
Operating revenues:									58.9	56.5	58
Long-lived assets, as defined:	2.1				2.1				2.1	2.1	1.4
Middle East and Asia [Member]
Total revenues									51,317.1	30,606.9	25,781.4
Operating revenues:									75.5	34.8	28.9
Long-lived assets, as defined:	1.3				1				1.3	1	1.2
Other [Member]
Total revenues									7.7	5.8	4.6
Operating revenues:									7.7	5.8	4.6
Long-lived assets, as defined:	$ 0.2				$ 0.3				$ 0.2	$ 0.3	$ 0

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 14,284.9	$ 8,243.4	$ 20,366.3	$ 11,245	$ 11,279.6	$ 7,873	$ 7,192.2	$ 6,552.2	$ 54,139.6	$ 32,897	$ 27,622.7
Cost of sales of physical commodities	13,942.8	7,920.8	19,999.5	10,968.2	10,992.7	7,589.6	6,921.1	6,287.5	52,831.3	31,790.9	26,646.9
Operating revenues	342.1	322.6	366.8	276.8	286.9	283.4	271.1	264.7	1,308.3	1,106.1	975.8
Transaction-based clearing expenses	57.1	55.3	63.8	46.3	45	45.7	42.7	50.1	222.5	183.5	179.7
Introducing broker commissions	34	24	29.6	26.2	27.7	29.6	24.8	32.6	113.8	114.7	133.8
Interest expense	10	11.5	27.8	31.1	37.2	39.4	35.2	30.2	80.4	142	70.5
Interest expense on corporate funding	14.8	3.9	2.2	2.7	3.6	3.1	3.2	2.8	23.6	12.7	10.2
Net operating revenues	226.2	227.9	243.4	170.5	173.4	165.6	165.2	149	868	653.2	581.6
Compensation and benefits	145.5	132.5	136.7	104	105.2	100.9	97.9	89.1	518.7	393.1	337.7
Bad debts, net of recoveries and impairment	12.5	1.8	4.4	0	1	0.5	0.7	0.3	18.7	2.5	3.1
Recovery of bad debt on physical coal					(10)	0	0	(2.4)	0	(12.4)	1	$ 47
Other expenses	70.1	44.6	46.2	44.9	43.2	42.6	41.1	37.6
Total compensation and other expenses	228.1	178.9	187.3	148.9	139.4	144	139.7	124.6	743.2	547.7	482.1
Gain on acquisitions	81.8	0	0	0.1	0.1	0	5.4	0	81.9	5.5	2
Income before tax	79.9	49	56.1	21.7	34.1	21.6	30.9	24.4	206.7	111	101.5
Income tax expense	2.5	12.4	16.8	5.4	6.9	5.3	7.5	6.2	37.1	25.9	46
Net income (loss)	$ 77.4	$ 36.6	$ 39.3	$ 16.3	$ 27.2	$ 16.3	$ 23.4	$ 18.2	$ 169.6	$ 85.1	$ 55.5
Net basic (loss) earnings per share (in dollar per share)	$ 4	$ 1.90	$ 2.03	$ 0.85	$ 1.42	$ 0.85	$ 1.23	$ 0.96	$ 8.78	$ 4.46	$ 2.93
Net diluted (loss) earnings per share (in dollar per share)	$ 3.90	$ 1.87	$ 2	$ 0.84	$ 1.40	$ 0.84	$ 1.21	$ 0.94	$ 8.61	$ 4.39	$ 2.87
Bargain purchase gain related to acquisition	$ 81.8						$ 5.4

Condensed Financial Informati_2

Condensed Financial Information of Parent Company Only Disclosure - Balance Sheet (Details) - USD ($) $ in Millions		Sep. 30, 2020	Oct. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Cash and cash equivalents		$ 952.6		$ 471.3
Income taxes receivable		16.6		5.2
Deferred income taxes, net		36.9		18
Property and equipment, net		62.1		43.9
Operating right of use assets		101.5	$ 33.1
Total assets		13,474.9		9,936.1	$ 7,824.7
Liabilities:
Accounts payable and other accrued liabilities		272.6		157.5
Operating lease liabilities		118.7	$ 36.2
Payable to clients		5,689		3,589.5
Payable to lenders under loans		268.1		202.3
Senior Secured Notes		336		0
Financial instruments sold, not yet purchased, at fair value		686		714.8
Total liabilities		12,707.4		9,341.9
StoneX Group Inc. (Parent Company Only) stockholders’ equity:
Common stock, $0.01 par value. Authorized 30,000,000 shares; 21,798,551 issued and 19,376,594 outstanding at September 30, 2020 and 21,297,317 issued and 19,075,360 outstanding at September 30, 2019		0.2		0.2
Common stock in treasury, at cost - 2,421,957 shares at September 30, 2020 and 2,221,957 shares at September 30, 2019		(57.6)		(50.1)
Additional paid-in capital		292.6		276.8
Retained earnings		572.4		402.1
Total equity		767.5		594.2	$ 505.3	$ 449.9
Total liabilities and stockholders' equity		13,474.9		9,936.1
StoneX Group [Member]
Cash and cash equivalents		7.4		2
Receivable from subsidiaries, net		0		17.6
Receivable from clients		0.4		0.5
Notes receivable, net		1.7		2.8
Income taxes receivable		46.2		15.7
Investment in subsidiaries		834		399.4
Deferred income taxes, net		4.3		8.2
Property and equipment, net		42.1		26.9
Operating right of use assets		69
Other assets		20.1		13
Total assets		1,025.2		486.1
Liabilities:
Accounts payable and other accrued liabilities		73.4		29.4
Operating lease liabilities		85.4
Payable to clients		0.3		0.3
Payable to subsidiaries, net		96.5		0
Payable to lenders under loans		23		70.4
Senior Secured Notes		515.1		167.6
Financial instruments sold, not yet purchased, at fair value		1.1		84.5
Total liabilities		794.8		352.2
StoneX Group Inc. (Parent Company Only) stockholders’ equity:
Preferred stock, $.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding		0		0
Common stock, $0.01 par value. Authorized 30,000,000 shares; 21,798,551 issued and 19,376,594 outstanding at September 30, 2020 and 21,297,317 issued and 19,075,360 outstanding at September 30, 2019		0.2		0.2
Common stock in treasury, at cost - 2,421,957 shares at September 30, 2020 and 2,221,957 shares at September 30, 2019		(57.6)		(50.1)
Additional paid-in capital		292.6		276.8
Retained earnings	[1]	(4.8)		(93)
Total equity		230.4		133.9
Total liabilities and stockholders' equity		1,025.2		486.1
Adjustment to Investment in Subs for Equity Method Accounting		$ 577.2		$ 495.1
[1]	Within the Condensed Balance Sheets and Condensed Statements of Operations of StoneX Group Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, investment in subsidiaries and retained earnings would each increase by $577.2 million as of September 30, 2020, respectively, and $495.1 million, as of September 30, 2019, respectively.

Condensed Financial Informati_3

Condensed Financial Information of Parent Company Only Disclosure - Balance Sheet (Parentheticals) (Details) - $ / shares	Sep. 30, 2020	Sep. 30, 2019
Preferred stock - par value (in dollar per share)	$ 0.01	$ 0.01
Preferred stock - authorized (in shares)	1,000,000	1,000,000
Preferred stock - issued (in shares)	0	0
Preferred stock - outstanding (in shares)	0	0
Common stock - par value (in dollar per share)	$ 0.01	$ 0.01
Common stock - authorized (in shares)	30,000,000	30,000,000
Common stock - issued (in shares)	21,798,551	21,297,317
Common stock - outstanding (in shares)	19,376,594	19,075,360
Treasury stock - shares (in shares)	2,421,957	2,221,957
StoneX Group [Member]
Preferred stock - par value (in dollar per share)	$ 0.01	$ 0.01
Preferred stock - authorized (in shares)	1,000,000	1,000,000
Preferred stock - issued (in shares)	0	0
Preferred stock - outstanding (in shares)	0	0
Common stock - par value (in dollar per share)	$ 0.01	$ 0.01
Common stock - authorized (in shares)	30,000,000	30,000,000
Common stock - issued (in shares)	21,798,551	21,297,317
Common stock - outstanding (in shares)	19,376,594	19,075,360
Treasury stock - shares (in shares)	2,421,957	2,221,957

Condensed Financial Informati_4

Condensed Financial Information of Parent Company Only Disclosure - Income Statement (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Statements, Captions [Line Items]
Interest income										$ 130.9	$ 198.9	$ 123.3
Operating revenues		$ 342.1	$ 322.6	$ 366.8	$ 276.8	$ 286.9	$ 283.4	$ 271.1	$ 264.7	1,308.3	1,106.1	975.8
Interest expense		10	11.5	27.8	31.1	37.2	39.4	35.2	30.2	80.4	142	70.5
Net operating revenues		226.2	227.9	243.4	170.5	173.4	165.6	165.2	149	868	653.2	581.6
Non-interest expenses:
Compensation and benefits		145.5	132.5	136.7	104	105.2	100.9	97.9	89.1	518.7	393.1	337.7
Clearing and related expenses		57.1	55.3	63.8	46.3	45	45.7	42.7	50.1	222.5	183.5	179.7
Occupancy and equipment rental										23.5	19.4	16.5
Professional fees										30.2	21	18.1
Travel and business development										8.9	16.2	13.8
Depreciation and amortization										19.7	14	11.6
Communications										7	6.6	5.4
Other										29.6	23.2	20.1
Total compensation and other expenses		228.1	178.9	187.3	148.9	139.4	144	139.7	124.6	743.2	547.7	482.1
Gain on acquisitions		81.8	0	0	0.1	0.1	0	5.4	0	81.9	5.5	2
Income before tax		79.9	49	56.1	21.7	34.1	21.6	30.9	24.4	206.7	111	101.5
Income tax expense		2.5	12.4	16.8	5.4	6.9	5.3	7.5	6.2	37.1	25.9	46
Net income (loss)		$ 77.4	$ 36.6	$ 39.3	$ 16.3	$ 27.2	$ 16.3	$ 23.4	$ 18.2	169.6	85.1	55.5
StoneX Group [Member]
Condensed Financial Statements, Captions [Line Items]
Management fees from affiliates										45.1	43.2	40.4
Trading losses, net										0.6	0	0
Consulting fees										0.3	0.1	0
Interest income										2.4	1.5	2.3
Dividend income from subsidiaries	[1]									111.8	85.7	41.9
Operating revenues										160.2	130.5	84.6
Interest expense										30	19.7	15.7
Net operating revenues										130.2	110.8	68.9
Non-interest expenses:
Compensation and benefits										88	79.7	73
Clearing and related expenses										0.3	0.9	1.1
Trading systems and market information										3.9	6.4	5.8
Occupancy and equipment rental										3.8	3.4	2.6
Professional fees										12.9	7.3	6.7
Travel and business development										1.7	2.9	2.6
Non-trading technology and support										19.8	12.5	9.1
Depreciation and amortization										6.7
Communications										0.7	0.8	0.9
Impairment										2.5	0	0
Management services fees to affiliates										2.3	0.5	0
Other										10.8	5.8	6.9
Total compensation and other expenses										153.4	125.4	113.5
Gain on acquisitions										81.9	5.3	0
Income before tax										58.7	(9.3)	(44.6)
Income tax expense										29.5	24.6	7.4
Net income (loss)										88.2	15.3	(37.2)
Investment in subsidiaries for equity method accounting										$ 81.4	$ 69.8	$ 92.7
[1]	W ithin the Condensed Balance Sheets and Condensed Statements of Operations of StoneX Group Inc. - Parent Company Only, the Company has accounted for its investment in wholly owned subsidiaries using the cost method of accounting. Under this method, the Company’s share of the earnings or losses of such subsidiaries are not included in the Condensed Balance Sheet or Condensed Statements of Operations. If the accounting for its investment in wholly owned subsidiaries were presented under the equity method of accounting, revenues would also include income from investment in subsidiaries of $81.4 million, $69.8 million, and $92.7 million for the years ended September 30, 2020, 2019, and 2018, respectively.

Condensed Financial Informati_5

Condensed Financial Information of Parent Company Only Disclosure - Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income (loss)	$ 77.4	$ 36.6	$ 39.3	$ 16.3	$ 27.2	$ 16.3	$ 23.4	$ 18.2	$ 169.6	$ 85.1	$ 55.5
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization of operating right of use assets									9.9
Deferred income taxes									4.1	3.7	22.3
Amortization and extinguishment of debt issuance costs									6.5	1.5	1
Amortization of share-based compensation expense									10.3	8.1	6.6
Gain on acquisition	(81.8)						$ (5.4)
Changes in operating assets and liabilities:
Income taxes receivable									(11.1)	(4.2)	(1.3)
Financial instruments owned, at fair value									(552.5)	(113.3)	(308.7)
Other assets									(3.7)	(8.3)	(3.3)
Accounts payable and other accrued liabilities									42.7	6.7	18.6
Payable to clients									2,093.7	(46.8)	520
Financial instruments sold, not yet purchased, at fair value									(28.8)	(156.1)	153.9
Net cash provided by (used in) operating activities									1,950.6	195.6	(473.6)
Cash flows from investing activities:
Purchase of property and equipment									(16.6)	(11.9)	(12.5)
Net cash used in investing activities									(241.6)	(40.8)	(15.4)
Cash flows from financing activities:
Repayments of note payable									(0.4)	(0.8)	(0.8)
Repayments of senior secured term loan									(9.8)	(6.6)	0
Repayment of senior secured notes									(92.1)	0	0
Share repurchase									(7.5)	(3.8)	0
Debt issuance costs									(15)	(3.3)	(0.4)
Exercise of stock options									5.5	1.2	2.6
Withholding taxes on stock option exercises									0	0	(0.8)
Net cash provided by financing activities									312.3	9.6	120.9
Net increase (decrease) in cash, segregated cash, cash equivalents, and segregated cash equivalents									2,017.1	163.7	(372.2)
Cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period				2,451.3				2,287.6	2,451.3	2,287.6	2,659.8
Cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period	4,468.4				2,451.3				4,468.4	2,451.3	2,287.6
Cash paid for interest									90.4	153.2	78.9
Income taxes (received) paid, net of cash refunds									44	24.6	22.2
Additional consideration payable related to acquisitions									0.9
StoneX Group [Member]
Cash flows from operating activities:
Net income (loss)									88.2	15.3	(37.2)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization									6.7	5.2	4.8
Amortization of operating right of use assets									4.4
Deferred income taxes									0	0.6	18
Amortization and extinguishment of debt issuance costs									6.1	1.2	0.7
Amortization of share-based compensation expense									9.2	7.1	6.1
Impairment									2.5	0	0
Gain on acquisition									(81.9)	(5.4)	0
Changes in operating assets and liabilities:
Due to/from subsidiaries									149.3	8.3	(69.4)
Receivables from clients, net									0.1	(0.5)	0
Notes receivable, net									1.1	(1)	2.9
Income taxes receivable									(48.4)	(0.8)	(6.6)
Financial instruments owned, at fair value									0	4.4	(4.4)
Other assets									(7.7)	(4.4)	(0.7)
Accounts payable and other accrued liabilities									24	4.6	8.6
Operating lease liabilities									(2.8)
Payable to clients									0	(1.4)	(0.3)
Financial instruments sold, not yet purchased, at fair value									(83.4)	25.2	34
Net cash provided by (used in) operating activities									67.4	58.4	(43.5)
Cash flows from investing activities:
Capital contribution in affiliates									(251.9)	(75.8)	(4.5)
Purchase of property and equipment									(10.2)	(6.2)	(5.9)
Net cash used in investing activities									(262.1)	(82)	(10.4)
Cash flows from financing activities:
Net change in lenders under loans									(47)	(138.2)	58.2
Repayments of note payable									(0.4)	(0.8)	(0.8)
Proceeds from issuance of senior secured term loan									21.5	175	0
Repayments of senior secured term loan									(9.8)	(6.6)	0
Proceeds from issuance of senior secured notes									344.8	0	0
Repayment of senior secured notes									(92.1)	0	0
Deferred payments on acquisitions									(0.9)	0	(5.5)
Share repurchase									(7.5)	(3.8)	0
Debt issuance costs									(14)	(3)	0
Exercise of stock options									5.5	1.2	2.6
Withholding taxes on stock option exercises									0	0	(0.8)
Net cash provided by financing activities									200.1	23.8	53.7
Net increase (decrease) in cash, segregated cash, cash equivalents, and segregated cash equivalents									5.4	0.2	(0.2)
Cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period				$ 2				$ 1.8	2	1.8	2
Cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period	$ 7.4				$ 2				7.4	2	1.8
Cash paid for interest									15.3	18.9	15
Income taxes (received) paid, net of cash refunds									(4.3)	(23.9)	(18.4)
Additional consideration payable related to acquisitions									$ 21.6	$ 1.8	$ 0

Uncategorized Items - intl-2020

Label	Element	Value
Non cash equivalent segregated assets	intl_NonCashEquivalentSegregatedAssets	$ 306,000,000
Non cash equivalent segregated assets	intl_NonCashEquivalentSegregatedAssets	13,000,000
Non cash equivalent segregated assets	intl_NonCashEquivalentSegregatedAssets	643,200,000
Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties	intl_NonSegregatedCashAndOtherNonCashEquivalentAssetsIncludedWithInDepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterParties	2,021,300,000
Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties	intl_NonSegregatedCashAndOtherNonCashEquivalentAssetsIncludedWithInDepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterParties	1,304,400,000
Non segregated cash and other non cash equivalent assets included with in deposits and receivables from broker dealers clearing organizations and counter parties	intl_NonSegregatedCashAndOtherNonCashEquivalentAssetsIncludedWithInDepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterParties	1,054,700,000
Deposits with and receivables from broker dealers, clearing organizations, and counterparties [Member]
Restricted Cash Equivalents	us-gaap_RestrictedCashEquivalents	467,900,000	[1]
Restricted Cash Equivalents	us-gaap_RestrictedCashEquivalents	288,700,000	[1]
Restricted Cash Equivalents	us-gaap_RestrictedCashEquivalents	909,900,000	[1]
Restricted Cash	us-gaap_RestrictedCash	711,900,000	[1]
Restricted Cash	us-gaap_RestrictedCash	947,400,000	[1]
Restricted Cash	us-gaap_RestrictedCash	698,700,000	[1]
Cash segregated under federal and other regulations [Member]
Cash Segregated under Commodity Exchange Act Regulation	us-gaap_CashSegregatedUnderCommodityExchangeActRegulation	1,907,200,000	[2]
Cash Segregated under Commodity Exchange Act Regulation	us-gaap_CashSegregatedUnderCommodityExchangeActRegulation	743,900,000	[2]
Cash Segregated under Commodity Exchange Act Regulation	us-gaap_CashSegregatedUnderCommodityExchangeActRegulation	765,500,000	[2]
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	952,600,000
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	471,300,000
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	$ 342,300,000
[1]	Represents segregated client cash and U.S. Treasury obligations on deposit with, or pledged to, exchange clearing organizations and other FCMs. Excludes non-segregated cash, segregated securities pledged to exchange-clearing organizations with original or acquired maturities greater than 90 days, and other assets of $2,021.3 million , $1,304.4 million, and $1,054.7 million as of September 30, 2020, 2019, and 2018, respectively, included within ‘Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net’ on the consolidated balance sheets.
[2]	Represents segregated client cash held at third-party banks. Excludes segregated commodity warehouse receipts, segregated United States (“U.S.”) Treasury obligations with original or acquired maturities of greater than 90 days, and other assets of $13.0 million , $306.0 million, and $643.2 million as of September 30, 2020, 2019, and 2018, respectively, included within ‘Cash, securities and other assets segregated under federal and other regulations’ on the consolidated balance sheets.