StoneX (SNEX) 10-Q 8 May 24 2024 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Mar. 31, 2024	May 06, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
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	230 Park Ave
Entity Address, Address Line Two	10th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10169
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		31,716,068
Entity Central Index Key	0000913760
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Mar. 31, 2024		Sep. 30, 2023
ASSETS
Cash and cash equivalents	$ 1,305.1		$ 1,108.3
Restricted cash	363	[1]	0
Cash, securities and other assets segregated under federal and other regulations (including $4.1 million and $5.8 million at fair value at March 31, 2024 and September 30, 2023, respectively)	2,838.4		2,426.3
Collateralized transactions:
Securities purchased under agreements to resell	3,744.6		2,979.5
Securities borrowed	1,430.6		1,129.1
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net (including $4,157.3 million and $4,248.3 million at fair value at March 31, 2024 and September 30, 2023, respectively)	7,706.5		7,443.8
Receivable from clients, net (including $(3.4) million and $(7.9) million at fair value at March 31, 2024 and September 30, 2023, respectively)	1,293.4		683.1
Notes receivable, net	0		5.2
Income taxes receivable	32.9		25.1
Financial instruments owned, at fair value (includes securities pledged as collateral that can be sold or repledged of $1,860.8 million and $1,466.4 million at March 31, 2024 and September 30, 2023, respectively)	5,666.5		5,044.8
Physical commodities inventory, net (including $355.2 million and $386.5 million at fair value at March 31, 2024 and September 30, 2023, respectively)	616.9		537.3
Deferred tax asset	42.3		45.4
Property and equipment, net	134.2		123.5
Operating right of use assets	146.4		122.1
Goodwill and intangible assets, net	79.5		82.4
Other assets	250.7		182.8
Total assets	25,651		21,938.7
Liabilities:
Accounts payable and other accrued liabilities (including $1.7 million and $1.5 million at fair value at March 31, 2024 and September 30, 2023, respectively)	491.8		533
Operating lease liabilities	181.9		149.3
Payables to:
Clients (including $585.6 million and $79.8 million at fair value at March 31, 2024 and September 30, 2023, respectively)	11,165.4		9,976
Broker-dealers, clearing organizations and counterparties (including $(21.3) million and $10.2 million at fair value at March 31, 2024 and September 30, 2023, respectively)	391.7		442.4
Lenders under loans	253.6		341
Senior secured borrowings, net	885.9		342.1
Income taxes payable	36.6		38.2
Deferred tax liability	8.2		8.1
Collateralized transactions:
Securities sold under agreements to repurchase	6,011.7		4,526.6
Securities loaned	1,458.6		1,117.3
Financial instruments sold, not yet purchased, at fair value	3,223		3,085.6
Total liabilities	24,108.4		20,559.6
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.01 par value. Authorized 1,000,000 shares; no shares issued or outstanding	0		0
Common stock, $0.01 par value. Authorized 200,000,000 shares; 35,561,232 issued and 31,650,247 outstanding at March 31, 2024 and 35,105,852 issued and 31,194,867 outstanding at September 30, 2023	0.4		0.4
Common stock in treasury, at cost. 3,910,985 shares at March 31, 2024 and September 30, 2023	(69.3)		(69.3)
Additional paid-in-capital	390.8		371.7
Retained earnings	1,250.3		1,128.1
Accumulated other comprehensive loss, net	(29.6)		(51.8)
Total equity	1,542.6		1,379.1
Total liabilities and stockholders' equity	$ 25,651		$ 21,938.7
[1] Represents restricted cash held in an escrow account, as further described in Note 1 and Note 9.

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Statement of Financial Position [Abstract]
Cash, securities and other assets segregated under federal and other regulations at fair value	$ 4.1	$ 5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties at fair value	4,157.3	4,248.3
Receivables from clients at fair value	(3.4)	(7.9)
Financial instruments owned, securities pledged as collateral that can be sold or repledged	1,860.8	1,466.4
Physical commodities inventory at fair value	355.2	386.5
Accounts payable and other accrued liabilities at fair value	1.7	1.5
Payables to client at fair value	585.6	79.8
Payables to broker-dealers, clearing organizations and counterparties at fair value	$ (21.3)	$ 10.2
Preferred stock - par value (in dollars 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)	200,000,000	200,000,000
Common stock - issued (in shares)	35,561,232	35,105,852
Common stock - outstanding (in shares)	31,650,247	31,194,867
Treasury stock - shares (in shares)	3,910,985	3,910,985

Condensed Consolidated Income S

Condensed Consolidated Income Statements (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Revenues:
Total revenues	$ 22,106.1	$ 16,161	$ 41,679.1	$ 29,172.6
Cost of sales of physical commodities	21,287.9	15,456.6	40,076.7	27,813.4
Operating revenues	818.2	704.4	1,602.4	1,359.2
Transaction-based clearing expenses	78.5	69.2	152.8	136.5
Introducing broker commissions	42	42.2	81.1	79
Interest expense	259.2	178.7	495.2	333
Interest expense on corporate funding	16.2	14.9	29.4	29.3
Net operating revenues	422.3	399.4	843.9	781.4
Compensation and other expenses:
Compensation and benefits	234.4	232.5	452.5	431.5
Trading systems and market information	19.4	17.8	38.1	35.5
Professional fees	19.3	11.3	35	27.2
Non-trading technology and support	18	16.2	34.9	31
Occupancy and equipment rental	13.6	10.6	21.3	19.5
Selling and marketing	15.6	14.2	27.3	27.1
Travel and business development	7.1	5.8	14.2	11.5
Communications	2.3	2.1	4.5	4.3
Depreciation and amortization	12.3	13.1	23.5	25.8
Bad debts (recoveries), net	(0.4)	3	(0.7)	3.7
Other	15.3	15.3	32.2	34.7
Total compensation and other expenses	356.9	341.9	682.8	651.8
Gain on acquisition and other gains	6.9	0	6.9	23.5
Income before tax	72.3	57.5	168	153.1
Income tax expense	19.2	15.8	45.8	34.8
Net income	$ 53.1	$ 41.7	$ 122.2	$ 118.3
Earnings per share:
Basic (in dollar per shares)	$ 1.68	$ 1.35	$ 3.88	$ 3.85
Diluted (in dollar per shares)	$ 1.63	$ 1.30	$ 3.76	$ 3.71
Weighted-average number of common shares outstanding:
Basic (in shares)	30,473,856	29,895,041	30,352,824	29,775,078
Diluted (in shares)	31,498,943	30,931,792	31,373,739	30,830,870
Sales of physical commodities
Revenues:
Total revenues	$ 21,321.9	$ 15,506.2	$ 40,142.8	$ 27,909.6
Principal gains, net
Revenues:
Total revenues	281.8	256.6	575.6	510.8
Commission and clearing fees
Revenues:
Total revenues	136.2	130.7	265.9	248.7
Consulting, management, and account fees
Revenues:
Total revenues	40.2	40.7	78.7	80.5
Interest income
Revenues:
Total revenues	$ 326	$ 226.8	$ 616.1	$ 423

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 53.1	$ 41.7	$ 122.2	$ 118.3
Other comprehensive (loss)/gain, net of tax:
Foreign currency translation adjustment	(4.6)	3.2	2.3	11.4
Cash flow hedges	(0.8)	14.3	19.9	29
Total other comprehensive (loss)/gain, net of tax	(5.4)	17.5	22.2	40.4
Comprehensive income	$ 47.7	$ 59.2	$ 144.4	$ 158.7

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions		6 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net income		$ 122.2	$ 118.3
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization		23.5	25.8
Amortization of right of use assets		9.1	5.7
Bad debts (recoveries), net		(0.7)	3.7
Deferred income taxes		(3.3)	1.8
Amortization of debt issuance costs		2.6	2.8
Amortization of share-based compensation		16.8	14.9
Gain on acquisition		0	(23.5)
Changes in operating assets and liabilities, net:
Securities and other assets segregated under federal and other regulations		1.7	579.6
Securities purchased under agreements to resell		(765.1)	(951.2)
Securities borrowed		(301.5)	456.1
Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net		133.2	(1,314.1)
Receivables from clients, net		(609.6)	(363.3)
Income taxes receivable		(7.7)	3.7
Financial instruments owned, at fair value		(616.3)	(859.3)
Physical commodities inventory, net		(79.6)	(36.1)
Other assets		(68.7)	(45.2)
Accounts payable and other accrued liabilities		(41.7)	60.1
Operating lease liabilities		(0.8)	(0.5)
Payables to clients		1,189.4	274.1
Payables to broker-dealers, clearing organizations, and counterparties		(50.7)	(101.8)
Income taxes payable		(1.5)	9.2
Securities sold under agreements to repurchase		1,485.1	1,827.5
Securities loaned		341.3	(425)
Financial instruments sold, not yet purchased, at fair value		158.7	134
Net cash provided by/(used in) operating activities		936.4	(602.7)
Cash flows from investing activities:
Proceeds from notes receivable		5	0
Acquisition of businesses and assets, net of cash received		(1.1)	(6.1)
Sale of exchange memberships and common stock		0.1	0
Purchases of property and equipment		(30.1)	(22.5)
Net cash used in investing activities		(26.1)	(28.6)
Cash flows from financing activities:
Net change in payables to lenders under loans with maturities 90 days or less		(87.4)	67
Proceeds from payables to lenders under loans with maturities greater than 90 days		0	150
Repayments of payables to lenders under loans with maturities greater than 90 days		0	(151)
Proceeds from issuance of senior secured notes		550	0
Deferred payments on acquisitions		0	(17.2)
Debt issuance costs		(7.9)	0
Shares withheld to cover taxes on vesting of equity awards		(1.2)	0
Exercise of stock options		3.5	3.6
Net cash provided by financing activities		457	52.4
Effect of exchange rates on cash, restricted cash, segregated cash, cash equivalents, and segregated cash equivalents		2.2	11.1
Net increase/(decrease) in cash, restricted cash, segregated cash, cash equivalents, and segregated cash equivalents		1,369.5	(567.8)
Cash, restricted cash, segregated cash, cash equivalents, and segregated cash equivalents at beginning of period		6,041.7	6,285.1
Cash, restricted cash, segregated cash, cash equivalents, and segregated cash equivalents at end of period		7,411.2	5,717.3
Supplemental disclosure of cash flow information:
Cash paid for interest		548.6	337.5
Income taxes paid, net of cash refunds		56	19.5
Supplemental disclosure of non-cash investing and financing activities:
Additional consideration payable related to acquisition of customer list		0.8	0
Identified intangible assets and goodwill on acquisitions		0	10.3
Additional consideration payable related to acquisitions, net		0	28.7
Acquisition of business:
Assets acquired		0	143
Liabilities assumed		0	84.1
Total net assets acquired		0	58.9
Cash and cash equivalents		1,305.1	1,263.9
Restricted cash	[1]	363	0
Cash segregated under federal and other regulations	[2]	2,834.3	2,486.4
Securities segregated under federal and other regulations	[2]	0	0.2
Cash segregated and deposited with or pledged to exchange-clearing organizations and other futures commission merchants (“FCMs”)	[3]	1,362.9	1,032.5
Securities segregated and pledged to exchange-clearing organizations	[3]	1,545.9	934.3
Total cash, restricted cash, segregated cash, cash equivalents, and segregated cash equivalents shown in the condensed consolidated statements of cash flows		7,411.2	5,717.3
Non-cash equivalent segregated assets		4.1	25.7
Non-segregated cash and other non-cash equivalent assets included within deposits and receivables from broker-dealers, clearing organizations, and counterparties		$ 4,797.7	$ 5,649.5
[1] Represents restricted cash held in an escrow account, as further described in Note 1 and Note 9. Cash, securities and other assets segregated under federal and other regulations on the Condensed Consolidated Balance Sheets. 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 U.S. Treasury obligations pledged to exchange-clearing organizations with original or acquired maturities greater than 90 days, and other assets of $4,797.7 million and $5,649.5 million as of March 31, 2024 and 2023, respectively, included within Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net on the Condensed Consolidated Balance Sheets.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders’ Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss, net
Beginning balance at Sep. 30, 2022	$ 1,070.1	$ 0.4	$ (69.3)	$ 340	$ 889.6	$ (90.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	118.3				118.3
Other comprehensive gain (loss), net of tax	40.4					40.4
Exercise of stock options	3.6			3.6
Share-based compensation	14.9			14.9
Ending balance at Mar. 31, 2023	1,247.3	0.4	(69.3)	358.5	1,007.9	(50.2)
Beginning balance at Dec. 31, 2022	1,176.6	0.4	(69.3)	347	966.2	(67.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41.7				41.7
Other comprehensive gain (loss), net of tax	17.5					17.5
Exercise of stock options	2.1			2.1
Share-based compensation	9.4			9.4
Ending balance at Mar. 31, 2023	1,247.3	0.4	(69.3)	358.5	1,007.9	(50.2)
Beginning balance at Sep. 30, 2023	1,379.1	0.4	(69.3)	371.7	1,128.1	(51.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	122.2				122.2
Other comprehensive gain (loss), net of tax	22.2					22.2
Exercise of stock options	3.5			3.5
Shares withheld to cover taxes on vesting of equity awards	(1.2)			(1.2)
Share-based compensation	16.8			16.8
Ending balance at Mar. 31, 2024	1,542.6	0.4	(69.3)	390.8	1,250.3	(29.6)
Beginning balance at Dec. 31, 2023	1,482.8	0.4	(69.3)	378.7	1,197.2	(24.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	53.1				53.1
Other comprehensive gain (loss), net of tax	(5.4)					(5.4)
Exercise of stock options	3			3
Shares withheld to cover taxes on vesting of equity awards	(0.1)			(0.1)
Share-based compensation	9.2			9.2
Ending balance at Mar. 31, 2024	$ 1,542.6	$ 0.4	$ (69.3)	$ 390.8	$ 1,250.3	$ (29.6)

Basis of Presentation and Conso

Basis of Presentation and Consolidation and Accounting Standards Adopted	6 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation and Accounting Standards Adopted	Basis of Presentation and Consolidation and Accounting Standards Adopted StoneX Group Inc., a Delaware corporation, and its consolidated subsidiaries (collectively “StoneX” 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, products 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. The Company delivers access and services through the entire lifecycle of a trade, by delivering deep market expertise and on-the-ground intelligence, best execution, and finally post-trade clearing, custody, as well as settlement services. The Company has created revenue streams, diversified by asset class, client type and geography, that earn commissions, spreads, and principal revenue as clients execute transactions across its financial network, while monetizing non-trading client activity including interest and fee earnings on client balances as well as earning consulting fees for market intelligence and risk management services. The Company provides its services to a diverse group of clients in more than 180 countries. These clients include more than 54,000 commercial, institutional, and payments clients and over 400,000 retail clients. The Company’s clients include 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 common stock trades on The NASDAQ Global Select Market under the symbol “SNEX”. Basis of Presentation and Consolidation The accompanying unaudited Condensed Consolidated Balance Sheet as of September 30, 2023, which has been derived from the audited consolidated balance sheet of September 30, 2023, and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to those rules and regulations. The Company believes that the included disclosures clearly and fairly present the information within. In management’s opinion, all adjustments, generally consisting of normal accruals, considered necessary to fairly present the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X. Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2023, as filed with the SEC. These condensed consolidated financial statements include the accounts of StoneX Group Inc. and all entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. The Company’s fiscal year end is September 30, and its fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to fiscal years and fiscal interim periods. Preparing condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurement for financial instruments, revenue recognition, valuation of inventories, and income taxes. 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 financial statement issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. Estimates and assumptions were considered and made in context with the information reasonably available to the Company as of March 31, 2024 and through the date of this Form 10-Q. In the Condensed Consolidated Income Statements, the total revenues reported combine gross revenues for the physical commodities business and net revenues for all other businesses. The subtotal Operating revenues in the Condensed Consolidated Income Statements is calculated by deducting Cost of sales of physical commodities from Total revenues . The subtotal Net operating revenues in the Condensed Consolidated Income Statements is calculated as Operating revenues less Transaction-based clearing expenses , Introducing broker commissions , Interest expense, and Interest expense on corporate funding . 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 certain 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, direct non-variable expenses, as well as variable and non-variable expenses to operational and administrative employees. Common Stock Split On November 7, 2023, the Company’s Board of Directors approved a three-for-two split of its common stock, to be effected as a stock dividend. The stock split was effective on November 24, 2023, and entitled each shareholder of record as of November 17, 2023 to receive one additional share of common stock for every two shares owned and cash in lieu of fractional shares. The stock split increased the number of shares of common stock outstanding. All share and per share amounts contained herein have been retroactively adjusted for the stock split. The shares of common stock retain a par value of $0.01 per share. Accordingly, an amount equal to the par value of the increased shares resulting from the stock split was reclassified from Additional paid-in-capital to Common stock. Restricted Cash During the three months ended March 31, 2024, the Company established an escrow account designated to hold immediately available funds deposited by the Company and distribute the same amount on June 15, 2024, the intended redemption date, for the settlement of its 8.625% Senior Secured Notes due 2025. The Company has classified these funds as restricted because the funding is irrevocable, and the Company does not have the ability to withdraw the funds. See Note 9. Gain on Acquisition In October 2022, the Company’s wholly owned subsidiary, StoneX Netherlands B.V., acquired CDI-Societe Cotonniere De Distribution S.A. The fair value of identifiable net assets acquired was approximately $66.2 million and the purchase price was approximately $42.7 million. The value that the Company acquired in excess of consideration paid resulted in a gain on acquisition of $23.5 million for the six months ended March 31, 2023. Accounting Standards

Earnings per Share

Earnings per Share	6 Months Ended
	Mar. 31, 2024
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 earnings per share computations for the periods presented below. Three Months Ended March 31, Six Months Ended March 31, (in millions, except share amounts) 2024 2023 2024 2023 Numerator: Net income $ 53.1 $ 41.7 $ 122.2 $ 118.3 Less: Allocation to participating securities (1.9) (1.5) (4.3) (4.0) Net income allocated to common stockholders $ 51.2 $ 40.2 $ 117.9 $ 114.3 Denominator: Weighted average number of: Common shares outstanding 30,473,856 29,895,041 30,352,824 29,775,078 Dilutive potential common shares outstanding: Share-based awards 1,025,087 1,036,751 1,020,915 1,055,792 Diluted weighted-average common shares 31,498,943 30,931,792 31,373,739 30,830,870 The dilutive effect of share-based awards is reflected in diluted net income per share by applying the treasury stock method, which includes consideration of unamortized share-based compensation expense. Options to purchase 1,849,986 and 185,058 shares of common stock for the three months ended March 31, 2024 and 2023, respectively, were excluded from the calculation of diluted earnings per share as they would have been anti-dilutive. Options to purchase 1,321,535 and 272,094 shares of common stock for the six months ended March 31, 2024 and 2023, respectively, were excluded from the calculation of diluted earnings per share as they would have been anti-dilutive.

Assets and Liabilities, at Fair

Assets and Liabilities, at Fair Value	6 Months Ended
	Mar. 31, 2024
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. 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 an asset or liability at the measurement date. The Company uses prices and inputs that are current as of 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 to mitigate risks related to the reasonableness of such prices. Financial and nonfinancial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). A market is active if there are sufficient transactions on an ongoing basis to provide current pricing information for the asset or liability, pricing information is released publicly, and price quotations do not vary substantially either over time or among market participants. Observable inputs reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from sources independent of the reporting entity. Relevant guidance requires the Company to consider counterparty credit risk of all parties to outstanding derivative instruments that would be considered by a market participant in the transfer or settlement of such contracts (exit price). The Company’s exposure to credit risk on derivative financial instruments principally relates to the portfolio of Over-the-counter (“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. In accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“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. Fair value of financial and nonfinancial assets and liabilities that are carried on the Condensed Consolidated Balance Sheets at fair value on a recurring basis Cash and cash equivalents reported at fair value on a recurring basis includes certificates of deposit and 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 instruments with such quotes 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 based upon observable inputs for comparable financial instruments, 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 foreign exchange, 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 comparing of primary vendor prices to internal trader prices or secondary vendor prices. When evaluating the propriety of vendor-priced financial instruments using secondary prices, considerations include the range and quality of vendor prices, level of observable transactions for identical and similar instruments, and judgments based upon knowledge of a particular market and asset class. If the primary vendor price does not represent fair value, justification for using a secondary price, including source data used to make the determination, is subject to review and approval by authorized personnel prior to using a secondary price. Financial instruments owned and sold that are valued using third party pricing sources are included within either Level 1 or Level 2 of the fair value hierarchy based upon the observability of the inputs used and the level of activity in the market. The fair value estimates presented herein are based on pertinent information available to management as of March 31, 2024 and September 30, 2023. Although management is not aware of any factors that would significantly affect the estimated fair value amounts, such amounts have not been comprehensively revalued for purposes of these condensed consolidated financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein. The following tables set forth the Company’s financial and nonfinancial assets and liabilities accounted for at fair value, on a recurring basis, as of March 31, 2024 and September 30, 2023 by level in the fair value hierarchy. All fair value measurements were performed on a recurring basis as of March 31, 2024 and September 30, 2023. March 31, 2024 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 18.1 $ — $ — $ — $ 18.1 Money market mutual funds 99.9 — — — 99.9 Cash and cash equivalents 118.0 — — — 118.0 Commodities warehouse receipts 4.1 — — — 4.1 Securities and other assets segregated under federal and other regulations 4.1 — — — 4.1 U.S. Treasury obligations 3,405.5 — — — 3,405.5 To be announced and forward settling securities — 25.3 — (22.4) 2.9 Foreign government obligations 19.0 — — — 19.0 Derivatives 4,489.9 1,592.6 — (5,352.6) 729.9 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 7,914.4 1,617.9 — (5,375.0) 4,157.3 Receivables from clients, net - Derivatives 167.0 533.9 — (704.3) (3.4) Equity securities 466.7 14.5 — — 481.2 Corporate and municipal bonds — 339.9 — — 339.9 U.S. Treasury obligations 517.7 — — — 517.7 U.S. government agency obligations — 466.2 — — 466.2 Foreign government obligations 41.3 — — — 41.3 Agency mortgage-backed obligations — 3,186.0 — — 3,186.0 Asset-backed obligations — 136.9 — — 136.9 Derivatives 0.5 960.5 — (600.5) 360.5 Commodities leases — 15.3 — — 15.3 Commodities warehouse receipts 74.9 — — — 74.9 Exchange firm common stock 12.9 — — — 12.9 Cash flow hedges — 7.1 — — 7.1 Mutual funds and other 23.8 — 2.8 — 26.6 Financial instruments owned 1,137.8 5,126.4 2.8 (600.5) 5,666.5 Physical commodities inventory 166.8 188.4 — — 355.2 Total assets at fair value $ 9,508.1 $ 7,466.6 $ 2.8 $ (6,679.8) $ 10,297.7 Liabilities: Accounts payable and other accrued liabilities $ — $ — $ 1.7 $ — $ 1.7 Payables to clients - Derivatives 4,483.9 225.7 — (4,124.0) 585.6 TBA and forward settling securities — 22.9 — (21.9) 1.0 Derivatives 166.8 1,747.0 — (1,936.1) (22.3) Payable to broker-dealers, clearing organizations and counterparties 166.8 1,769.9 — (1,958.0) (21.3) Equity securities 275.8 4.8 — — 280.6 Foreign government obligations 45.0 — — — 45.0 Corporate and municipal bonds — 174.4 — — 174.4 U.S. Treasury obligations 2,239.4 — — — 2,239.4 U.S. government agency obligations — 27.2 — — 27.2 Agency mortgage-backed obligations — 7.6 — — 7.6 Asset-backed obligations — 5.3 — — 5.3 Derivatives 9.3 974.1 — (546.7) 436.7 Cash flow hedges — 5.7 — — 5.7 Other — — 1.1 — 1.1 Financial instruments sold, not yet purchased 2,569.5 1,199.1 1.1 (546.7) 3,223.0 Total liabilities at fair value $ 7,220.2 $ 3,194.7 $ 2.8 $ (6,628.7) $ 3,789.0 (1) Represents cash collateral and the impact of netting across at each level of the fair value hierarchy. September 30, 2023 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 8.7 $ — $ — $ — $ 8.7 Money market mutual funds 57.8 — — — 57.8 Cash and cash equivalents 66.5 — — — 66.5 Commodities warehouse receipts 5.8 — — — 5.8 Securities and other assets segregated under federal and other regulations 5.8 — — — 5.8 U.S. Treasury obligations 4,023.8 — — — 4,023.8 TBA and forward settling securities — 73.5 — (31.7) 41.8 Foreign government obligations 17.8 — — — 17.8 Derivatives 5,497.5 1,135.9 — (6,468.5) 164.9 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 9,539.1 1,209.4 — (6,500.2) 4,248.3 Receivables from clients, net - Derivatives 61.7 561.3 (630.9) (7.9) Equity securities 324.0 10.3 — — 334.3 Corporate and municipal bonds — 284.2 — — 284.2 U.S. Treasury obligations 531.7 — — — 531.7 U.S. government agency obligations — 451.7 — — 451.7 Foreign government obligations 43.3 — — — 43.3 Agency mortgage-backed obligations — 2,865.8 — — 2,865.8 Asset-backed obligations — 138.8 — — 138.8 Derivatives 0.6 868.1 — (600.2) 268.5 Commodities leases — 16.0 — — 16.0 Commodities warehouse receipts 54.7 — — — 54.7 Exchange firm common stock 12.0 — — — 12.0 Cash flow hedges — 1.7 — — 1.7 Mutual funds and other 39.3 — 2.8 — 42.1 Financial instruments owned 1,005.6 4,636.6 2.8 (600.2) 5,044.8 Physical commodities inventory 240.3 146.2 — — 386.5 Total assets at fair value $ 10,919.0 $ 6,553.5 $ 2.8 $ (7,731.3) $ 9,744.0 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.5 $ — $ 1.5 Payables to clients - Derivatives 5,430.7 226.2 (5,577.1) 79.8 TBA and forward settling securities — 47.5 — (31.4) 16.1 Derivatives 112.2 1,402.0 — (1,520.1) (5.9) Payable to broker-dealers, clearing organizations and counterparties 112.2 1,449.5 — (1,551.5) 10.2 Equity securities 230.6 5.5 — — 236.1 Foreign government obligations 21.5 — — — 21.5 Corporate and municipal bonds — 81.6 — — 81.6 U.S. Treasury obligations 2,409.3 — — — 2,409.3 U.S. government agency obligations — 5.1 — — 5.1 Agency mortgage-backed obligations — 31.7 — — 31.7 Derivatives 2.4 769.2 — (510.4) 261.2 Cash flow hedges — 27.1 — — 27.1 Other — 10.9 1.1 — 12.0 Financial instruments sold, not yet purchased 2,663.8 931.1 1.1 (510.4) 3,085.6 Total liabilities at fair value $ 8,206.7 $ 2,606.8 $ 2.6 $ (7,639.0) $ 3,177.1 (1) Represents cash collateral and the impact of netting across at each level of the fair value hierarchy. Realized and unrealized gains and losses are included in Principal gains, net , Interest income , and Cost of sales of physical commodities in the Condensed Consolidated Income Statements. Additional disclosures about the fair value of financial instruments that are not carried on the Condensed Consolidated Balance Sheets at fair value Many, but not all, of the financial instruments that the Company holds are recorded at fair value in the Condensed Consolidated Balance Sheets. The following represents financial instruments for which the ending balance at March 31, 2024 and September 30, 2023 was not carried at fair value on the Condensed Consolidated Balance Sheets in accordance with U.S. GAAP: 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 resell and securities sold under agreements to repurchase, and securities borrowed and loaned are recorded at amounts that approximate the fair value of these instruments due to their short-term nature and level of collateralization. These financial instruments generally expose the Company to limited credit risk and have no stated maturities or have short-term maturities and carry interest rates that approximate market rates. Under the fair value hierarchy, cash and cash equivalents and cash segregated under federal and other regulations are classified as Level 1. Securities purchased under agreements to resell and securities sold under agreements to repurchase, and securities borrowed and loaned are classified as Level 2 under the fair value hierarchy as they are generally overnight or short-term in nature and are collateralized by equity securities, U.S. Treasury obligations, U.S. government agency obligations, agency mortgage-backed obligations, and asset-backed obligations. Receivables and other assets : Receivables from broker-dealers, clearing organizations, and counterparties, receivables from clients, net, notes receivables, and certain other assets are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Payables : Payables to clients and payables to broker-dealers, clearing organizations, and counterparties are recorded at amounts that approximate fair value due to their short-term nature and are classified as Level 2 under the fair value hierarchy. Lenders under loans : Payables to lenders under loans carry variable rates of interest and thus approximate fair value and are classified as Level 2 under the fair value hierarchy. Senior secured borrowings, net : Senior secured borrowings, net includes the Company's 8.625% Senior Secured Notes due 2025 (the “Senior Secured Notes 2025”) and the Company’s 7.875% Senior Secured Notes due 2031 (the “Senior Secured Notes 2031”), as further described in Note 9, with a carrying value of $343.7 million and $542.2 million, respectively, as of March 31, 2024. The carrying value of the Senior Secured Notes 2025 and Senior Secured Notes 2031 represent their principal amount net of unamortized deferred financing costs and original issue discount. As of March 31, 2024, the Senior Secured Notes 2025 had a fair value of $349.4 million and the Senior Secured Notes 2031 had a fair value of $557.8 million, with both being 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	6 Months Ended
	Mar. 31, 2024
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 condensed consolidated financial statements as of March 31, 2024 and September 30, 2023 at the fair values of the related financial instruments. The Company will incur losses if the fair value of the underlying financial instruments increases subsequent to March 31, 2024. The total financial instruments sold, not yet purchased of $3,223.0 million and $3,085.6 million as of March 31, 2024 and September 30, 2023, respectively, includes $436.7 million and $261.2 million for derivative contracts not designated as hedges, respectively, which represented a liability to the Company based on their fair values as of March 31, 2024 and September 30, 2023. 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 Condensed Consolidated 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 , Payable 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 March 31, 2024 and September 30, 2023. Assets represent net unrealized gains and liabilities represent net unrealized losses. March 31, 2024 September 30, 2023 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,732.5 $ 1,725.8 $ 1,907.0 $ 1,890.3 OTC commodity derivatives 2,319.0 2,269.6 1,523.3 1,456.0 Exchange-traded foreign exchange derivatives 1.4 1.4 4.3 4.3 OTC foreign exchange derivatives 326.1 280.4 497.1 455.3 Exchange-traded interest rate derivatives 782.2 791.5 1,507.6 1,509.8 OTC interest rate derivatives 270.2 270.2 417.6 417.6 Exchange-traded equity index derivatives 2,141.3 2,141.3 2,140.9 2,140.9 OTC equity and indices derivatives 171.7 126.6 127.3 68.5 TBA and forward settling securities 25.3 22.9 73.5 47.5 Subtotal 7,769.7 7,629.7 8,198.6 7,990.2 Derivative contracts designated as hedging instruments: Interest rate contracts — 5.7 — 24.6 Foreign currency forward contracts 7.1 — 1.7 2.5 Subtotal 7.1 5.7 1.7 27.1 Gross fair value of derivative contracts $ 7,776.8 $ 7,635.4 $ 8,200.3 $ 8,017.3 Impact of netting and collateral (6,679.8) (6,628.7) (7,731.3) (7,639.0) Total fair value included in Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net $ 732.8 $ 206.7 Total fair value included in Receivable from clients, net $ (3.4) $ (7.9) Total fair value included in Financial instruments owned, at fair value $ 367.6 $ 270.2 Total fair value included in Payables to clients $ 585.6 $ 79.8 Total fair value included in Payables to broker-dealers, clearing organizations and counterparties $ (21.3) $ 10.2 Total fair value included in Financial instruments sold, not yet purchased, at fair value $ 442.4 $ 288.3 (1) As of March 31, 2024 and September 30, 2023, the Company’s derivative contract volume for open positions was approximately 11.8 million and 13.4 million contracts, respectively. The Company’s derivative contracts are principally held in its Institutional, Commercial, and Retail segments. The Company provides its Institutional segment clients access to exchanges at which they can carry out their trading strategies. 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 exchange 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 difference (“CFD”) 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, other derivatives, or cash collateral paid or received. Hedging Activities The Company uses interest rate derivatives, in the form of swaps, to hedge risk related to variability in overnight rates. These hedges are designated cash flow hedges, through which the Company mitigates uncertainty in its interest income by converting floating-rate interest income to fixed-rate interest income. While the swaps mitigate interest rate risk, they do introduce credit risk, which is the possibility that the Company’s trading counterparty fails to meet its obligation. The Company minimizes this risk by entering into its swaps with highly-rated, multi-national institutions. In addition to credit risk, there is market risk associated with the swap positions. The Company’s market risk is limited, because any amounts the Company must pay from having exchanged variable interest will be funded by the variable interest the Company receives on its deposits. As of March 31, 2024, the Company’s hedges will all have matured in less than 1 year from the end of the current period. The Company also uses foreign currency derivatives, in the form of forward contracts, to hedge risk related to the variability in exchange rates relative to certain of the Company’s non-USD expenditures. These hedges are designated cash flow hedges, through which the Company mitigates variability in exchange rates by exchanging foreign currency for USD at fixed exchange rates at a pre-determined future date, or several cash flows at several pre-determined future dates. While the forward contracts mitigate exchange rate variability risk, they do introduce credit risk, which is the possibility that the Company’s trading counterparty fails to meet its obligation. The Company minimizes this risk by entering into its forward contracts with highly-rated, multi-national institutions. These hedges will all mature within 2 years from the end of the current period. The Company assesses the effectiveness of its hedges at each reporting period to identify any required reclassifications into current earnings. During the three months ended March 31, 2024 and 2023, the Company did not designate any portion of its hedges as ineffective and thus did not have any values in current earnings related to ineffective hedges. The fair values of derivative instruments designated for hedging held as of March 31, 2024 and September 30, 2023 are as follow: March 31, 2024 September 30, 2023 (in millions) Balance Sheet Location Fair Value Fair Value Asset Derivatives Derivatives designated as hedging instruments: Foreign currency forward contracts Financial instruments owned, net $ 7.1 $ 1.7 Total derivatives designated as hedging instruments $ 7.1 $ 1.7 Derivative assets expected to be released from Other comprehensive income into current earnings: Foreign currency forward contracts $ 5.6 $ 1.4 Total expected to be released from Other comprehensive income into earnings $ 5.6 $ 1.4 Liability Derivatives Derivatives designated as hedging instruments: Interest rate contracts Financial instruments sold, not yet purchased $ 5.7 $ 24.6 Foreign currency forward contracts Financial instruments sold, not yet purchased — 2.5 Total derivatives designated as hedging instruments $ 5.7 $ 27.1 Derivative liabilities expected to be released from Other comprehensive income into current earnings: Interest rate contracts $ 5.7 $ 20.3 Foreign currency forward contracts — 1.0 Total expected to be released from Other comprehensive income into earnings $ 5.7 $ 21.3 The notional values of derivative instruments designated for hedging held as of March 31, 2024 and September 30, 2023 are as follows: March 31, 2024 September 30, 2023 (in millions) Notional Value Notional Value Derivatives designated as hedging instruments: Interest rate contracts $ 1,000.0 $ 2,000.0 Foreign currency forward contracts: Foreign currency forward contracts to purchase Polish Zloty: Local currency zł 156.1 zł 156.1 USD $ 35.8 $ 34.0 Foreign currency forward contracts to purchase British Pound Sterling: Local currency £ 120.0 £ 168.0 USD $ 147.6 $ 206.9 The Condensed Consolidated Income Statement effects of derivative instruments designated for hedging held for the three and six months ended March 31, 2024 and 2023 are as follows: (in millions) Income Statement Location Three Months Ended March 31, 2024 Six Months Ended March 31, 2024 Total amounts reclassified from Accumulated Other Comprehensive Income into Income: Interest rate contracts Interest income $ (4.6) $ (20.5) Foreign currency forward contracts Compensation and benefits 1.8 3.7 Total derivatives designated as hedging instruments $ (2.8) $ (16.8) Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring $ — $ — (in millions) Income Statement Location Three Months Ended March 31, 2023 Six Months Ended March 31, 2023 Total amounts reclassified from Accumulated Other Comprehensive Income into Income: Interest rate contracts Interest Income $ (11.6) $ (17.0) Foreign currency forward contracts Compensation and benefits 0.7 0.5 Total derivatives designated as hedging instruments $ (10.9) $ (16.5) Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring $ — $ — The accumulated other comprehensive income effects of derivative instruments designated for hedging held for three and six months ended March 31, 2024 and 2023 are as follow: Amount of Gain/(Loss) Recognized in Other Comprehensive Income on Derivatives, net of tax (in millions) Three Months Ended March 31, 2024 Three Months Ended March 31, 2023 Derivatives in Cash Flow Hedging Relationships: Interest rate contracts $ 1.7 $ 10.6 Foreign currency forward contracts (2.5) 3.7 Total $ (0.8) $ 14.3 Amount of Gain Recognized in Other Comprehensive Income on Derivatives, net of tax (in millions) Six Months Ended March 31, 2024 Six Months Ended March 31, 2023 Derivatives in Cash Flow Hedging Relationships: Interest rate contracts $ 14.3 $ 9.2 Foreign currency forward contracts 5.6 19.8 Total $ 19.9 $ 29.0 The following table sets forth the Company’s net gains/(losses) related to derivative financial instruments for the three and six months ended March 31, 2024 and 2023 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 Condensed Consolidated Income Statements. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Commodities $ 30.4 $ 147.8 $ 117.5 $ 202.0 Foreign exchange 32.6 (72.8) 57.8 (24.0) Interest rate, equities, and indices 15.5 25.6 42.9 33.9 TBA and forward settling securities 25.5 (14.1) (67.7) (37.1) Net gains from derivative contracts $ 104.0 $ 86.5 $ 150.5 $ 174.8 Credit Risk In the normal course of business, the Company purchases and sells financial instruments, commodities and foreign currencies as either a principal or agent on behalf of its clients. If either the client or counterparty fails to perform, the Company may be required to discharge the obligations of the nonperforming party. In such circumstances, the Company may sustain a loss if the fair value of the financial instrument, commodity, or foreign currency is different from the contract value of the transaction. The majority of the Company’s transactions and, consequently, the concentration of its credit exposure are with commodity exchanges, clients, broker-dealers and other financial institutions. These activities primarily involve collateralized and uncollateralized arrangements and may result in credit exposure in the event that a counterparty fails to meet its contractual obligations. The Company’s exposure to credit risk can be directly impacted by volatile financial markets, which may impair counterparties’ ability to satisfy contractual obligations. The Company seeks to control its credit risk through a variety of reporting and control procedures, including establishing credit and/or position limits based upon a review of the counterparties’ financial condition and credit ratings. The Company monitors collateral levels on a daily basis for compliance with regulatory and internal guidelines and requests changes in collateral levels as appropriate. The Company is a party to financial instruments in the normal course of its business through client and proprietary trading accounts in exchange-traded and OTC derivative instruments. These instruments are primarily the result of the execution of orders for commodity futures, options on futures, OTC swaps and options and spot and forward foreign currency contracts on behalf of its clients, substantially all of which are transacted on a margin basis. Such transactions may expose the Company to significant credit risk in the event that margin requirements are not sufficient to fully cover losses which clients may incur. The Company controls the risks associated with these transactions by requiring clients to maintain margin deposits in compliance with individual exchange regulations and internal guidelines. The Company monitors required margin levels daily, and therefore, may require clients to deposit additional collateral or reduce positions when necessary. The Company also establishes credit limits for clients, which are monitored daily. The Company evaluates each client’s creditworthiness on a case by case basis. Clearing, financing, and settlement activities may require the Company to maintain funds with or pledge securities as collateral with other financial institutions. Generally, these exposures to both clients and exchanges are subject to master netting, or client agreements, which reduce the exposure to the Company by permitting receivables and payables with such clients to be offset in the event of a client default. Management believes that the margin deposits held as of March 31, 2024 and September 30, 2023 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	6 Months Ended
	Mar. 31, 2024
Receivables [Abstract]
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $0.0 million as of March 31, 2024 and $0.1 million as of September 30, 2023. The allowance for doubtful accounts related to receivables from clients was $57.0 million and $59.8 million as of March 31, 2024 and September 30, 2023, respectively. The Company had no allowance for doubtful accounts related to notes receivable as of March 31, 2024 and September 30, 2023. Activity in the allowance for doubtful accounts for the six months ended March 31, 2024 was as follows: (in millions) Balance as of September 30, 2023 $ 59.9 Recovery of bad debts (1) (2.1) Allowance charge-offs (1.2) Other 0.4 Balance as of March 31, 2024 $ 57.0 (1) An additional $1.4 million is included in bad debt expense for the six months ended March 31, 2024 on the consolidated income statement, which is not included in the allowance at the period then ended.

Physical Commodities Inventory

Physical Commodities Inventory	6 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Physical Commodities Inventory	Physical Commodities Inventory The Company’s inventories consist of finished physical commodities as shown below. (in millions) March 31, September 30, Physical Ag & Energy (1) $ 188.4 $ 146.2 Precious metals - held by broker-dealer subsidiary 166.8 240.3 Precious metals - held by non-broker-dealer subsidiaries 261.7 150.8 Physical commodities inventory, net $ 616.9 $ 537.3 (1) Physical Ag & Energy consists of agricultural commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, cocoa, cotton, and various energy commodity inventories. Agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. The Company records changes to these values in Cost of sales of physical commodities on the Condensed Consolidated Income Statements.

Goodwill

Goodwill	6 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill allocated to the Company’s operating segments is as follows: (in millions) March 31, September 30, Commercial $ 33.5 $ 33.7 Institutional 9.8 9.8 Retail 5.8 5.8 Payments 10.0 10.0 Total Goodwill $ 59.1 $ 59.3

Intangible Assets

Intangible Assets	6 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	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): March 31, 2024 September 30, 2023 Gross Amount Accumulated Net Amount Gross Amount Accumulated Net Amount Intangible assets subject to amortization Trade/domain names $ 4.1 $ (2.8) $ 1.3 $ 4.1 $ (2.4) $ 1.7 Software programs/platforms 4.9 (3.7) 1.2 28.5 (26.9) 1.6 Client and supplier base 35.2 (23.0) 12.2 38.3 (24.1) 14.2 Total intangible assets subject to amortization 44.2 (29.5) 14.7 70.9 (53.4) 17.5 Intangible assets not subject to amortization Website domains 2.0 — 2.0 1.9 — 1.9 Business licenses 3.7 — 3.7 3.7 — 3.7 Total intangible assets not subject to amortization 5.7 — 5.7 5.6 — 5.6 Total intangible assets $ 49.9 $ (29.5) $ 20.4 $ 76.5 $ (53.4) $ 23.1 Amortization expense related to intangible assets was $2.1 million and $4.1 million for the three months ended March 31, 2024 and 2023, respectively. Amortization expense related to intangible assets was $4.1 million and $8.0 million for the six months ended March 31, 2024 and 2023, respectively. The Company wrote off $27.8 million of fully amortized intangible assets during the six months ended March 31, 2024. As of March 31, 2024, estimated future amortization expense was as follows: (in millions) Fiscal 2024 (remaining months) $ 3.0 Fiscal 2025 3.7 Fiscal 2026 2.9 Fiscal 2027 2.3 Fiscal 2028 and thereafter 2.8 Total intangible assets subject to amortization $ 14.7

Credit Facilities

Credit Facilities	6 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Credit Facilities	Credit Facilities Committed Credit Facilities The Company and its subsidiaries have committed credit facilities under which they may borrow up to $1,200.0 million, subject to the terms and conditions of these facilities. The amounts outstanding under these credit facilities carry variable rates of interest, thus approximating fair value. The committed credit facilities generally have covenant requirements that relate to various leverage, debt to net worth, fixed charge, tangible net worth, excess net capital, or profitability measures. The Company and its subsidiaries were in compliance with all relevant covenants as of March 31, 2024. Uncommitted Credit Facilities The Company has access to certain uncommitted financing agreements that support its ordinary course securities and commodities inventories. The agreements are subject to certain borrowing terms and conditions. Note Payable to Bank The Company has notes payable to a commercial bank related to the financing of certain equipment which secures the notes. Senior Secured Notes On March 1, 2024, the Company issued $550 million in aggregate principal amount of the Company’s 7.875% Senior Secured Notes due 2031 (the “Notes due 2031”) at the offering price of 100% of the aggregate principal amount. The Notes due 2031 are fully and unconditionally guaranteed, jointly and severally, on a senior secured second lien basis by each of the Company’s existing and future subsidiaries that guarantees indebtedness under the Company’s senior secured revolving credit facility and certain other senior indebtedness. Interest related to these notes is payable twice annually, in arrears. The Company incurred debt issuance costs of $7.9 million, which are being amortized over the term of the Notes due 2031 under the effective interest method. The Company used a portion of the proceeds from the issuance of the Notes due 2031 to irrevocably fund an account holding funds to satisfy its 8.625% Senior Secured Notes due 2025 (the “Notes due 2025”) via an in-substance defeasance. The defeasance included placing $363.0 million of immediately available funds, representing the aggregate principal amount outstanding and all unpaid interest (accrued and yet to be accrued) through, but not including, June 15, 2024, into an escrow account designated to hold and distribute the same amount on the intended redemption date of June 15, 2024. These funds are reported within Restricted Cash on the Condensed Consolidated Balance Sheets. The Notes due 2025 are scheduled to mature on June 15, 2025. Interest on the Notes due 2025 accrues at a rate of 8.625% per annum and is payable semiannually in arrears. The Company incurred debt issuance costs of $9.5 million in connection with the issuance of the Notes due 2025 in June 2020, which are being amortized over the term of the Notes due 2025 under the effective interest method. The Company has had the right, since June 15, 2022, to redeem the Notes due 2025, in whole or in part, at the redemption prices set forth in the indenture governing the Notes due 2025. The following table sets forth a listing of credit facilities, the current committed amounts as of the report date on the facilities, and outstanding (in millions, except for percentages): (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment March 31, 2024 September 30, Committed Credit Facilities Senior StoneX Group Inc. Committed Credit Facility - Revolving Line of Credit (1) April 21, 2026 $ 500.0 $ 25.0 (5) $ 150.0 StoneX Financial Inc. None October 29, 2024 190.0 — (5) — StoneX Commodity Solutions LLC Certain assets July 28, 2024 400.0 71.0 (5) 103.0 StoneX Financial Ltd. None October 12, 2024 100.0 50.0 (5) 25.0 StoneX Financial Pte. Ltd. None September 6, 2024 10.0 — (5) — $ 1,200.0 $ 146.0 $ 278.0 Uncommitted Credit Facilities Various 100.4 (5) 55.5 Note Payable to Bank Certain equipment 7.2 (5) 7.5 Senior Secured Notes due 2031 (2) 542.2 (4) — Senior Secured Notes due 2025 (2) 343.7 (3) 342.1 Total outstanding borrowings $ 1,139.5 $ 683.1 (1) The StoneX Group Inc. senior committed credit facility is a revolving facility 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. The maturity date remains April 21, 2025 for one lender representing $17.5 million of the facility commitment. (2) The 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 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) Included in Senior secured borrowings, net on the Condensed Consolidated Balance Sheets. Amounts outstanding under the Notes due 2025 are reported net of unamortized original issue discount and unamortized deferred financing costs of $4.2 million and $5.8 million, in the respective periods presented. The amounts payable under Notes due 2025 have been defeased as the Company has placed the necessary funds in escrow, reported in Restricted cash on the Condensed Consolidated Balance Sheets. (4) Included in Senior secured borrowings, net on the Condensed Consolidated Balance Sheets . Amounts outstanding under the Notes due 2031 are reported net of unamortized deferred financing costs of $7.8 million. (5) Included in Lenders under loans on the Condensed Consolidated Balance Sheets . As reflected above, certain of the Company’s committed credit facilities are scheduled to expire during the next twelve months following the quarterly period ended March 31, 2024. The Company intends to renew or replace the 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.

Securities and Commodity Financ

Securities and Commodity Financing Transactions	6 Months Ended
	Mar. 31, 2024
Broker-Dealer [Abstract]
Securities and Commodity Financing Transactions	Securities and Commodity Financing Transactions The Company’s repurchase agreements and securities borrowing and lending arrangements are generally recorded at cost in the Condensed Consolidated Balance Sheets, which is a reasonable approximation of their fair values due to their short-term nature. Secured borrowing and lending arrangements are entered into to obtain collateral necessary to effect settlement, finance inventory positions, meet customer needs or re-lend as part of our dealer operations. The fair value of securities loaned and borrowed is monitored daily compared with the related payable or receivable, and additional collateral or returning excess collateral is requested, as appropriate. These arrangements may serve to limit credit risk resulting from our transactions with our counterparties. Financial instruments are pledged as collateral under repurchase agreements, securities lending agreements and other secured arrangements, including clearing arrangements. Agreements with counterparties generally contain contractual provisions allowing counterparties the right to sell or repledge collateral. Either the Company or its counterparties may require additional collateral. All collateral is held by the Company or a custodian. The following tables set forth the carrying value of repurchase agreements, and securities lending agreements by remaining contractual maturity (in millions): March 31, 2024 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 10,183.8 $ 1,183.1 $ 610.6 $ 97.5 $ 12,075.0 Securities loaned 1,458.6 — — — 1,458.6 Gross amount of secured financing $ 11,642.4 $ 1,183.1 $ 610.6 $ 97.5 $ 13,533.6 September 30, 2023 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 8,300.0 $ 786.8 $ 107.0 $ 2.6 $ 9,196.4 Securities loaned 1,117.3 — — — 1,117.3 Gross amount of secured financing $ 9,417.3 $ 786.8 $ 107.0 $ 2.6 $ 10,313.7 Offsetting of Collateralized Transactions The following table sets forth the carrying value of repurchase agreements and securities lending agreements by class of collateral pledged (in millions): Securities sold under agreements to repurchase March 31, 2024 September 30, 2023 U.S. Treasury obligations $ 9,017.4 $ 3,696.1 U.S. government agency obligations 99.1 542.2 Asset-backed obligations 40.9 102.9 Agency mortgage-backed obligations 2,302.5 4,371.6 Foreign government obligations 318.2 148.1 Corporate bonds 296.9 335.5 Total securities sold under agreement to repurchase $ 12,075.0 $ 9,196.4 Securities loaned Equity securities $ 1,458.6 $ 1,117.3 Total securities loaned 1,458.6 1,117.3 Gross amount of secured financing $ 13,533.6 $ 10,313.7 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): March 31, 2024 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Securities purchased under agreements to resell $ 9,807.9 $ (6,063.3) $ 3,744.6 Securities borrowed $ 1,430.6 $ — $ 1,430.6 Securities sold under agreements to repurchase $ 12,075.0 $ (6,063.3) $ 6,011.7 Securities loaned $ 1,458.6 $ — $ 1,458.6 September 30, 2023 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Securities purchased under agreements to resell $ 7,649.3 $ (4,669.8) $ 2,979.5 Securities borrowed $ 1,129.1 $ — $ 1,129.1 Securities sold under agreements to repurchase $ 9,196.4 $ (4,669.8) $ 4,526.6 Securities loaned $ 1,117.3 $ — $ 1,117.3 The Company pledges securities owned as collateral in both tri-party and bilateral arrangements. Pledged securities under tri-party arrangements may not be repledged or sold by the Company’s counterparties, whereas bilaterally pledged securities may be. The approximate fair value of pledged securities that can be sold or repledged by the Company’s counterparties has been parenthetically disclosed on the Condensed Consolidated Balance Sheets. The Company receives securities as collateral under reverse repurchase agreements, securities borrowed agreements, and margin securities held on behalf of counterparties. 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 arrangement and matched-booked trading strategies. Additional securities collateral is obtained as necessary to ensure such transactions are adequately collateralized. In many instances, the Company is permitted by contract to repledge the securities received as collateral, which may include pledges to cover collateral requirements for tri-party repurchase agreements. The following table sets forth the carrying value, which approximates fair value because of its short term nature, of collateral pledged, received and repledged (in millions): March 31, 2024 September 30, 2023 Securities pledged or repledged to cover collateral requirements for tri-party arrangements $ 5,827.0 $ 4,726.6 Securities received as collateral that may be repledged $ 14,131.4 $ 9,180.1 Securities received as collateral that may be repledged covering securities sold short $ 2,563.7 $ 2,461.1 Repledged securities borrowed and client securities held under custodial clearing arrangements to collateralize securities loaned agreements $ 1,298.5 $ 1,097.3

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Contingencies The Company had receivables, net of collections and other allowable deductions, of $11.1 million as of March 31, 2024, due from account holders in connection with the OptionSellers matter previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2023. The allowance against these uncollected balances was $3.5 million as of March 31, 2024. The Company is pursuing collection of the outstanding balances through arbitration proceedings against the account holders. The Company will consider developments in these proceedings, and any other relevant matters, in determining whether any changes in the allowance against the uncollected balances are required. In these and other arbitration proceedings, clients are seeking damages from StoneX Financial Inc. related to the trading losses in their accounts. During the six months ended March 31, 2024, the Company favorably resolved several of these arbitration claims through arbitration decisions and privately negotiated settlements. All of the arbitration panels that issued decisions during the period awarded StoneX Financial Inc. the full amount of the uncollected balances. As noted, several of the arbitrations were resolved through privately negotiated settlement, pursuant to which the account holders agreed to pay some or all of their outstanding deficit balances. The Company intends to continue vigorously pursuing claims through arbitration and settling cases in what the Company determines to be appropriate circumstances. The ultimate outcome of remaining arbitrations cannot presently be determined. Depending on future collections and the outcomes of arbitration proceedings, any provisions for bad debts and actual losses may be material to the Company’s financial results. However, the Company believes that the likelihood of a material adverse outcome is remote, and does not currently believe that any potential losses related to this matter would impact its ability to comply with its ongoing liquidity, capital, and regulatory requirements. Legal Proceedings From time to time and in the ordinary course of business, the Company is involved in various legal actions and proceedings, including tort claims, contractual disputes, employment matters, workers’ compensation claims and collections. The Company carries insurance that provides protection against certain types of claims, up to the relevant policy’s limits. On November 13, 2023, BTIG filed a civil complaint (the “BTIG complaint”) against the Company and StoneX Financial Inc. in San Francisco Superior Court (CGC-23-610525) seeking monetary damages and injunctive relief for, among other things, alleged theft of purported trade secrets by former BTIG employees later employed at StoneX. The Company intends to vigorously defend itself. In addition, the Company subsequently received from the U.S. Department of Justice (the “DOJ”) and the SEC subpoenas that the Company believes are related to conduct alleged in the BTIG complaint, and the Company is cooperating with these agencies. The ultimate outcomes of the BTIG complaint and the DOJ and SEC subpoenas cannot presently be determined. As of March 31, 2024 and September 30, 2023, the Condensed Consolidated Balance Sheets include loss contingency accruals which are not material, individually or in the aggregate, to the Company’s financial position or liquidity. In the opinion of management, possible exposure from loss contingencies in excess of the amounts accrued, is not likely to be material to the Company’s earnings, financial position or liquidity. Contractual Commitments Self-Insurance The Company self-insures its costs related to medical and dental claims. The Company is self-insured, up to a stop loss amount, for eligible participating employees and retirees, and for qualified dependent medical and dental claims, subject to deductibles and limitations. As of March 31, 2024, the Company had $1.7 million accrued for self-insured medical and dental claims included in Accounts payable and other accrued liabilities in the Condensed Consolidated Balance Sheet.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss, Net	6 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Accumulated Other Comprehensive Loss, Net	Accumulated Other Comprehensive Loss, Net Accumulated other comprehensive loss, net 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 includes net actuarial losses from defined benefit pension plans, foreign currency translation adjustments, and cash flow hedge gains or losses. See note 4 for additional information on cash flow hedges. The following table summarizes the changes in accumulated other comprehensive loss, net for the six months ended March 31, 2024. (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Cash Flow Hedge Accumulated Other Comprehensive Loss, net Balances as of September 30, 2023 $ (31.2) $ (2.2) $ (18.4) $ (51.8) Other comprehensive income, net of tax 2.3 — 19.9 22.2 Balances as of March 31, 2024 $ (28.9) $ (2.2) $ 1.5 $ (29.6)

Revenue from Contracts with Cli

Revenue from Contracts with Clients	6 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Clients	Revenue from Contracts with Clients 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 in accordance with FASB ASC 606, Revenues from Contracts with Customers (Topic 606). 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. Topic 606 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. Revenues within the scope of Topic 606 are presented within Commission and clearing fees; Consulting, management, and account fees; and Sales of physical commodities on the Condensed Consolidated Income Statements. Revenues that are not within the scope of Topic 606 are presented within Sales of physical commodities , Principal gains, net , and Interest income on the Condensed Consolidated Income Statements. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Revenues from contracts with clients as a percentage of total revenues 2.3 % 5.7 % 2.7 % 6.4 % 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 periods indicated. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 55.8 $ 55.3 $ 107.2 $ 104.0 OTC derivative brokerage 3.0 4.5 5.8 8.1 Equities and fixed income 14.5 15.6 31.0 31.0 Mutual funds 0.9 0.9 1.6 1.5 Insurance and annuity products 3.7 2.7 5.7 4.5 Other 0.2 1.1 0.1 2.2 Total sales-based commission 78.1 80.1 151.4 151.3 Trailing: Mutual funds 3.2 3.1 6.2 6.1 Insurance and annuity products 3.7 3.5 7.4 7.0 Total trailing commission 6.9 6.6 13.6 13.1 Clearing fees 45.4 40.0 88.7 76.0 Trade conversion fees 3.5 2.0 7.5 4.4 Other 2.3 2.0 4.7 3.9 Total commission and clearing fees 136.2 130.7 265.9 248.7 Consulting, management, and account fees: Underwriting fees 0.1 0.1 0.1 0.3 Asset management fees 12.3 11.1 23.7 21.8 Advisory and consulting fees 9.0 9.0 17.2 17.7 Sweep program fees 11.3 12.9 22.7 24.3 Client account fees 4.3 3.7 8.5 7.5 Other 3.2 3.9 6.5 8.9 Total consulting, management, and account fees 40.2 40.7 78.7 80.5 Sales of physical commodities: Precious metals sales under ASC Topic 606 332.8 746.4 792.0 1,535.0 Total revenues from contracts with clients $ 509.2 $ 917.8 $ 1,136.6 $ 1,864.2 Method of revenue recognition: Point-in-time $ 469.7 $ 878.2 $ 1,059.4 $ 1,787.3 Time elapsed 39.5 39.6 77.2 76.9 Total revenues from contracts with clients 509.2 917.8 1,136.6 1,864.2 Other sources of revenues Physical precious metals under ASC Topic 815 20,067.0 13,703.1 37,229.5 24,182.1 Physical agricultural and energy products 922.1 1,056.7 2,121.3 2,192.5 Principal gains, net 281.8 256.6 575.6 510.8 Interest income 326.0 226.8 616.1 423.0 Total revenues $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Total revenues by primary geographic region: United States $ 1,407.7 $ 1,471.1 $ 3,011.2 $ 3,034.7 Europe 560.2 912.0 1,218.6 1,827.0 South America 105.0 56.5 233.0 118.7 Middle East and Asia 20,025.1 13,720.0 37,200.7 24,186.3 Other 8.1 1.4 15.6 5.9 Total revenues $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Operating revenues by primary geographic region: United States $ 590.0 $ 538.5 $ 1,158.0 $ 1,028.4 Europe 161.1 105.5 296.7 207.0 South America 25.2 32.0 66.4 63.5 Middle East and Asia 33.7 27.1 65.7 54.5 Other 8.2 1.3 15.6 5.8 Total operating revenues $ 818.2 $ 704.4 $ 1,602.4 $ 1,359.2 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, Institutional and Retail reportable segments. Sales of physical commodities under topic 606 are primarily related to the Company’s Commercial and Retail 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. Precious metals sales that are recognized on a point-in-time basis are included in the Retail and the Commercial reportable segments 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. The following table indicates the relevant income and expense: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Dividend income on long equity positions $ 65.8 $ 3.2 $ 86.0 $ 17.4 Dividend expense on short equity positions 64.7 4.1 83.5 17.3 Dividend (loss)/income, net reported within Principal Gains, net $ 1.1 $ (0.9) $ 2.5 $ 0.1 Remaining Performance Obligations Remaining performance obligations are services that the Company has committed to perform in the future in connection with its contracts with clients. The Company’s remaining performance obligations are generally related to its risk management consulting and asset management contracts with clients. Revenues associated with remaining performance obligations related to these contracts with clients are not material to the overall consolidated results of the Company. For the Company’s asset management activities, where fees are calculated based on a percentage of the fair 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 fair value of eligible assets in clients’ accounts.

Other Expenses

Other Expenses	6 Months Ended
	Mar. 31, 2024
Other Expenses [Abstract]
Other Expenses	Other Expenses Other expenses consisted of the following, for the periods indicated. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Non-income taxes $ 2.8 $ 2.2 $ 5.3 $ 6.9 Insurance 3.2 3.0 6.1 5.7 Employee related expenses 1.7 2.3 3.6 5.9 Other direct business expenses 3.5 4.1 7.9 8.1 Membership fees 1.0 1.1 1.9 1.9 Director and public company expenses 0.7 0.5 1.2 1.0 Office expenses 0.5 0.5 1.1 0.9 Other expenses 1.9 1.6 5.1 4.3 Total other expenses $ 15.3 $ 15.3 $ 32.2 $ 34.7

Income Taxes

Income Taxes	6 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The income tax provision for interim periods comprises income tax on ordinary income (loss) at the most recent estimated annual effective income tax rate, adjusted for the income tax effect of discrete items. Management uses an estimated annual effective income tax rate based on the forecasted pretax income/(loss) and statutory tax rates in the various jurisdictions in which the Company operates. The Company’s effective income tax rate differs from the U.S. statutory income tax rate primarily due to state and local taxes, global intangible low taxed income (“GILTI”), and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no income tax benefit can be recognized are excluded from the estimated annual effective income tax rate. 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. The Company is required to assess its deferred tax assets and the need for a valuation allowance at each reporting period. This assessment requires judgment on the part of management with respect to benefits that may be realized. The Company will record a valuation allowance against deferred tax assets when it is considered more likely than not that all or a portion of the deferred tax assets will not be realized. Current and Prior Period Tax Expense Income tax expense, as shown on the Condensed Consolidated Income Statements, reflects estimated federal, foreign, state and local income taxes. The Company’s effective tax rate was 26% and 27% for the three months ended March 31, 2024 and 2023, respectively. The effective tax rate was higher than the U.S. federal statutory rate of 21% for the three months ended March 31, 2024 due to U.S. state and local taxes, GILTI, U.S. and foreign permanent differences, and the amount of foreign earnings taxed at higher rates.

Regulatory Capital Requirements

Regulatory Capital Requirements	6 Months Ended
	Mar. 31, 2024
Capital and Other Regulatory Requirements [Abstract]
Regulatory Capital Requirements	Regulatory Capital Requirements The Company’s activities are subject to significant governmental regulation, both in the U.S. and in the international jurisdictions in which it operates. Subsidiaries of the Company were in compliance with all of their regulatory requirements as of March 31, 2024. The following table details those subsidiaries with minimum regulatory requirements in excess of $10.0 million along with the actual balance maintained as of that date. (in millions) As of March 31, 2024 Subsidiary Regulatory Authority Actual Minimum StoneX Financial Inc. SEC and CFTC $ 351.2 $ 257.2 StoneX Financial Ltd. FCA $ 455.5 $ 358.0 Gain Capital Group, LLC CFTC and NFA $ 50.6 $ 29.9 StoneX Financial Pte. Ltd. MAS $ 91.3 $ 25.8 StoneX Markets LLC CFTC and NFA $ 219.2 $ 125.9 Certain other subsidiaries of the Company, typically with a minimum requirement less than $10.0 million, are also subject to net capital requirements promulgated by authorities in the countries in which they operate. As of March 31, 2024, all of the Company’s subsidiaries were in compliance with their local regulatory requirements.

Segment Analysis

Segment Analysis	6 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Segment Analysis	Segment Analysis The Company’s operating segments are principally based on the nature of the clients it serves (commercial, institutional, and retail), and a fourth operating segment, its payments business. The Company manages its business in this manner due to its large global footprint, in which it has approximately 4,300 employees allowing it to serve clients in more than 180 countries. The Company’s business activities are managed as operating segments, which are our reportable segments for financial statement purposes as shown below. • Commercial • Institutional • Retail • Payments (previously disclosed as Global Payments) 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 places 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 18,000 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 U.S. 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 180 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. Total revenues, operating revenues and net operating revenues shown in the table below as “Corporate” primarily consist of interest income from the Company’s 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. “Overhead costs and expenses” 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. These amount represent the gross overhead costs and expenses, before any allocation of overhead costs to operating segments. Information for the reportable segments is shown in accordance with the Segment Reporting Topic of the ASC as follows: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Total revenues: Commercial $ 21,479.1 $ 15,450.7 $ 40,457.1 $ 27,744.2 Institutional 463.4 362.5 899.1 706.0 Retail 111.3 304.6 213.0 620.8 Payments 49.3 49.8 109.9 105.2 Corporate 14.4 2.5 23.6 15.3 Eliminations (11.4) (9.1) (23.6) (18.9) Total $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Operating revenues: Commercial $ 200.5 $ 220.1 $ 398.9 $ 402.5 Institutional 463.4 362.5 899.1 706.0 Retail 102.0 78.6 194.5 149.1 Payments 49.3 49.8 109.9 105.2 Corporate 14.4 2.5 23.6 15.3 Eliminations (11.4) (9.1) (23.6) (18.9) Total $ 818.2 $ 704.4 $ 1,602.4 $ 1,359.2 Net operating revenues (loss): Commercial $ 164.2 $ 185.1 $ 327.6 $ 337.8 Institutional 149.8 137.9 298.4 281.1 Retail 74.3 50.8 141.3 94.7 Payments 46.8 47.4 105.0 100.7 Corporate (12.8) (21.8) (28.4) (32.9) Total $ 422.3 $ 399.4 $ 843.9 $ 781.4 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial $ 119.3 $ 140.9 $ 245.7 $ 256.6 Institutional 102.5 89.3 202.7 183.9 Retail 69.9 48.4 132.5 87.6 Payments 37.3 38.1 84.9 80.2 Total $ 329.0 $ 316.7 $ 665.8 $ 608.3 Segment income: (Net contribution less non-variable direct segment costs) Commercial $ 85.6 $ 102.9 $ 172.8 $ 185.7 Institutional 61.3 55.8 126.5 117.8 Retail 33.2 4.8 61.9 0.6 Payments 24.6 15.9 59.6 48.2 Total $ 204.7 $ 179.4 $ 420.8 $ 352.3 Reconciliation of segment income to income before tax: Segment income $ 204.7 $ 179.4 $ 420.8 $ 352.3 Net operating revenue (loss) with Corporate (12.8) (21.8) (28.4) (32.9) Overhead costs and expenses (119.6) (100.1) (224.4) (189.8) Gain on acquisition — — — 23.5 Income before tax $ 72.3 $ 57.5 $ 168.0 $ 153.1 (in millions) As of March 31, 2024 As of September 30, 2023 Total assets: Commercial $ 5,154.8 $ 4,676.3 Institutional 17,684.1 15,059.3 Retail 1,111.8 1,014.2 Payments 433.1 376.6 Corporate 1,267.2 812.3 Total $ 25,651.0 $ 21,938.7

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net income	$ 53.1	$ 41.7	$ 122.2	$ 118.3

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Basis of Presentation and Con_2

Basis of Presentation and Consolidation and Accounting Standards Adopted (Policies)	6 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The accompanying unaudited Condensed Consolidated Balance Sheet as of September 30, 2023, which has been derived from the audited consolidated balance sheet of September 30, 2023, and the unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to those rules and regulations. The Company believes that the included disclosures clearly and fairly present the information within. In management’s opinion, all adjustments, generally consisting of normal accruals, considered necessary to fairly present the condensed consolidated financial statements for the interim periods presented have been reflected as required by Rule 10-01 of Regulation S-X. Operating results for interim periods are not necessarily indicative of the results that may be expected for the full year. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2023, as filed with the SEC.
Consolidation	These condensed consolidated financial statements include the accounts of StoneX Group Inc. and all entities in which the Company has a controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation.
Fiscal Period	The Company’s fiscal year end is September 30, and its fiscal quarters end on December 31, March 31, June 30 and September 30. Unless otherwise stated, all dates refer to fiscal years and fiscal interim periods.
Use of Estimates	Preparing condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates and assumptions relate to fair value measurement for financial instruments, revenue recognition, valuation of inventories, and income taxes. 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 financial statement issuance. Although these and other estimates and assumptions are based on the best available information, actual results could be materially different from these estimates. Estimates and assumptions were considered and made in context with the information reasonably available to the Company as of March 31, 2024 and through the date of this Form 10-Q.
Restricted Cash	Restricted Cash During the three months ended March 31, 2024, the Company established an escrow account designated to hold immediately available funds deposited by the Company and distribute the same amount on June 15, 2024, the intended redemption date, for the settlement of its 8.625% Senior Secured Notes due 2025. The Company has classified these funds as restricted because the funding is irrevocable, and the Company does not have the ability to withdraw the funds. See Note 9.
Gain on Acquisition	Gain on Acquisition In October 2022, the Company’s wholly owned subsidiary, StoneX Netherlands B.V., acquired CDI-Societe Cotonniere De Distribution S.A. The fair value of identifiable net assets acquired was approximately $66.2 million and the purchase price was approximately $42.7 million. The value that the Company acquired in excess of consideration paid resulted in a gain on acquisition of $23.5 million for the six months ended March 31, 2023.
Accounting Standards	Accounting Standards
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.
Income Taxes	The income tax provision for interim periods comprises income tax on ordinary income (loss) at the most recent estimated annual effective income tax rate, adjusted for the income tax effect of discrete items. Management uses an estimated annual effective income tax rate based on the forecasted pretax income/(loss) and statutory tax rates in the various jurisdictions in which the Company operates. The Company’s effective income tax rate differs from the U.S. statutory income tax rate primarily due to state and local taxes, global intangible low taxed income (“GILTI”), and differing statutory tax rates applied to the income of non-U.S. subsidiaries. The Company records the tax effect of certain discrete items, including the effects of changes in tax laws, tax rates and adjustments with respect to valuation allowances or other unusual or nonrecurring tax adjustments, in the interim period in which they occur, as an addition to, or reduction from, the income tax provision, rather than being included in the estimated effective annual income tax rate. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no income tax benefit can be recognized are excluded from the estimated annual effective income tax rate.

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Mar. 31, 2024
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 earnings per share computations for the periods presented below. Three Months Ended March 31, Six Months Ended March 31, (in millions, except share amounts) 2024 2023 2024 2023 Numerator: Net income $ 53.1 $ 41.7 $ 122.2 $ 118.3 Less: Allocation to participating securities (1.9) (1.5) (4.3) (4.0) Net income allocated to common stockholders $ 51.2 $ 40.2 $ 117.9 $ 114.3 Denominator: Weighted average number of: Common shares outstanding 30,473,856 29,895,041 30,352,824 29,775,078 Dilutive potential common shares outstanding: Share-based awards 1,025,087 1,036,751 1,020,915 1,055,792 Diluted weighted-average common shares 31,498,943 30,931,792 31,373,739 30,830,870

Assets and Liabilities, at Fa_2

Assets and Liabilities, at Fair Value (Tables)	6 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of 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 March 31, 2024 and September 30, 2023 by level in the fair value hierarchy. All fair value measurements were performed on a recurring basis as of March 31, 2024 and September 30, 2023. March 31, 2024 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 18.1 $ — $ — $ — $ 18.1 Money market mutual funds 99.9 — — — 99.9 Cash and cash equivalents 118.0 — — — 118.0 Commodities warehouse receipts 4.1 — — — 4.1 Securities and other assets segregated under federal and other regulations 4.1 — — — 4.1 U.S. Treasury obligations 3,405.5 — — — 3,405.5 To be announced and forward settling securities — 25.3 — (22.4) 2.9 Foreign government obligations 19.0 — — — 19.0 Derivatives 4,489.9 1,592.6 — (5,352.6) 729.9 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 7,914.4 1,617.9 — (5,375.0) 4,157.3 Receivables from clients, net - Derivatives 167.0 533.9 — (704.3) (3.4) Equity securities 466.7 14.5 — — 481.2 Corporate and municipal bonds — 339.9 — — 339.9 U.S. Treasury obligations 517.7 — — — 517.7 U.S. government agency obligations — 466.2 — — 466.2 Foreign government obligations 41.3 — — — 41.3 Agency mortgage-backed obligations — 3,186.0 — — 3,186.0 Asset-backed obligations — 136.9 — — 136.9 Derivatives 0.5 960.5 — (600.5) 360.5 Commodities leases — 15.3 — — 15.3 Commodities warehouse receipts 74.9 — — — 74.9 Exchange firm common stock 12.9 — — — 12.9 Cash flow hedges — 7.1 — — 7.1 Mutual funds and other 23.8 — 2.8 — 26.6 Financial instruments owned 1,137.8 5,126.4 2.8 (600.5) 5,666.5 Physical commodities inventory 166.8 188.4 — — 355.2 Total assets at fair value $ 9,508.1 $ 7,466.6 $ 2.8 $ (6,679.8) $ 10,297.7 Liabilities: Accounts payable and other accrued liabilities $ — $ — $ 1.7 $ — $ 1.7 Payables to clients - Derivatives 4,483.9 225.7 — (4,124.0) 585.6 TBA and forward settling securities — 22.9 — (21.9) 1.0 Derivatives 166.8 1,747.0 — (1,936.1) (22.3) Payable to broker-dealers, clearing organizations and counterparties 166.8 1,769.9 — (1,958.0) (21.3) Equity securities 275.8 4.8 — — 280.6 Foreign government obligations 45.0 — — — 45.0 Corporate and municipal bonds — 174.4 — — 174.4 U.S. Treasury obligations 2,239.4 — — — 2,239.4 U.S. government agency obligations — 27.2 — — 27.2 Agency mortgage-backed obligations — 7.6 — — 7.6 Asset-backed obligations — 5.3 — — 5.3 Derivatives 9.3 974.1 — (546.7) 436.7 Cash flow hedges — 5.7 — — 5.7 Other — — 1.1 — 1.1 Financial instruments sold, not yet purchased 2,569.5 1,199.1 1.1 (546.7) 3,223.0 Total liabilities at fair value $ 7,220.2 $ 3,194.7 $ 2.8 $ (6,628.7) $ 3,789.0 (1) Represents cash collateral and the impact of netting across at each level of the fair value hierarchy. September 30, 2023 (in millions) Level 1 Level 2 Level 3 Netting (1) Total Assets: Certificates of deposit $ 8.7 $ — $ — $ — $ 8.7 Money market mutual funds 57.8 — — — 57.8 Cash and cash equivalents 66.5 — — — 66.5 Commodities warehouse receipts 5.8 — — — 5.8 Securities and other assets segregated under federal and other regulations 5.8 — — — 5.8 U.S. Treasury obligations 4,023.8 — — — 4,023.8 TBA and forward settling securities — 73.5 — (31.7) 41.8 Foreign government obligations 17.8 — — — 17.8 Derivatives 5,497.5 1,135.9 — (6,468.5) 164.9 Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net 9,539.1 1,209.4 — (6,500.2) 4,248.3 Receivables from clients, net - Derivatives 61.7 561.3 (630.9) (7.9) Equity securities 324.0 10.3 — — 334.3 Corporate and municipal bonds — 284.2 — — 284.2 U.S. Treasury obligations 531.7 — — — 531.7 U.S. government agency obligations — 451.7 — — 451.7 Foreign government obligations 43.3 — — — 43.3 Agency mortgage-backed obligations — 2,865.8 — — 2,865.8 Asset-backed obligations — 138.8 — — 138.8 Derivatives 0.6 868.1 — (600.2) 268.5 Commodities leases — 16.0 — — 16.0 Commodities warehouse receipts 54.7 — — — 54.7 Exchange firm common stock 12.0 — — — 12.0 Cash flow hedges — 1.7 — — 1.7 Mutual funds and other 39.3 — 2.8 — 42.1 Financial instruments owned 1,005.6 4,636.6 2.8 (600.2) 5,044.8 Physical commodities inventory 240.3 146.2 — — 386.5 Total assets at fair value $ 10,919.0 $ 6,553.5 $ 2.8 $ (7,731.3) $ 9,744.0 Liabilities: Accounts payable and other accrued liabilities - contingent liabilities $ — $ — $ 1.5 $ — $ 1.5 Payables to clients - Derivatives 5,430.7 226.2 (5,577.1) 79.8 TBA and forward settling securities — 47.5 — (31.4) 16.1 Derivatives 112.2 1,402.0 — (1,520.1) (5.9) Payable to broker-dealers, clearing organizations and counterparties 112.2 1,449.5 — (1,551.5) 10.2 Equity securities 230.6 5.5 — — 236.1 Foreign government obligations 21.5 — — — 21.5 Corporate and municipal bonds — 81.6 — — 81.6 U.S. Treasury obligations 2,409.3 — — — 2,409.3 U.S. government agency obligations — 5.1 — — 5.1 Agency mortgage-backed obligations — 31.7 — — 31.7 Derivatives 2.4 769.2 — (510.4) 261.2 Cash flow hedges — 27.1 — — 27.1 Other — 10.9 1.1 — 12.0 Financial instruments sold, not yet purchased 2,663.8 931.1 1.1 (510.4) 3,085.6 Total liabilities at fair value $ 8,206.7 $ 2,606.8 $ 2.6 $ (7,639.0) $ 3,177.1 (1)

Financial Instruments with Of_2

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk (Tables)	6 Months Ended
	Mar. 31, 2024
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 March 31, 2024 and September 30, 2023. Assets represent net unrealized gains and liabilities represent net unrealized losses. March 31, 2024 September 30, 2023 (in millions) Assets (1) Liabilities (1) Assets (1) Liabilities (1) Derivative contracts not accounted for as hedges: Exchange-traded commodity derivatives $ 1,732.5 $ 1,725.8 $ 1,907.0 $ 1,890.3 OTC commodity derivatives 2,319.0 2,269.6 1,523.3 1,456.0 Exchange-traded foreign exchange derivatives 1.4 1.4 4.3 4.3 OTC foreign exchange derivatives 326.1 280.4 497.1 455.3 Exchange-traded interest rate derivatives 782.2 791.5 1,507.6 1,509.8 OTC interest rate derivatives 270.2 270.2 417.6 417.6 Exchange-traded equity index derivatives 2,141.3 2,141.3 2,140.9 2,140.9 OTC equity and indices derivatives 171.7 126.6 127.3 68.5 TBA and forward settling securities 25.3 22.9 73.5 47.5 Subtotal 7,769.7 7,629.7 8,198.6 7,990.2 Derivative contracts designated as hedging instruments: Interest rate contracts — 5.7 — 24.6 Foreign currency forward contracts 7.1 — 1.7 2.5 Subtotal 7.1 5.7 1.7 27.1 Gross fair value of derivative contracts $ 7,776.8 $ 7,635.4 $ 8,200.3 $ 8,017.3 Impact of netting and collateral (6,679.8) (6,628.7) (7,731.3) (7,639.0) Total fair value included in Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net $ 732.8 $ 206.7 Total fair value included in Receivable from clients, net $ (3.4) $ (7.9) Total fair value included in Financial instruments owned, at fair value $ 367.6 $ 270.2 Total fair value included in Payables to clients $ 585.6 $ 79.8 Total fair value included in Payables to broker-dealers, clearing organizations and counterparties $ (21.3) $ 10.2 Total fair value included in Financial instruments sold, not yet purchased, at fair value $ 442.4 $ 288.3 (1) As of March 31, 2024 and September 30, 2023, the Company’s derivative contract volume for open positions was approximately 11.8 million and 13.4 million contracts, respectively.
Schedule of Fair Value of Derivative Instruments Designated for Hedging	The fair values of derivative instruments designated for hedging held as of March 31, 2024 and September 30, 2023 are as follow: March 31, 2024 September 30, 2023 (in millions) Balance Sheet Location Fair Value Fair Value Asset Derivatives Derivatives designated as hedging instruments: Foreign currency forward contracts Financial instruments owned, net $ 7.1 $ 1.7 Total derivatives designated as hedging instruments $ 7.1 $ 1.7 Derivative assets expected to be released from Other comprehensive income into current earnings: Foreign currency forward contracts $ 5.6 $ 1.4 Total expected to be released from Other comprehensive income into earnings $ 5.6 $ 1.4 Liability Derivatives Derivatives designated as hedging instruments: Interest rate contracts Financial instruments sold, not yet purchased $ 5.7 $ 24.6 Foreign currency forward contracts Financial instruments sold, not yet purchased — 2.5 Total derivatives designated as hedging instruments $ 5.7 $ 27.1 Derivative liabilities expected to be released from Other comprehensive income into current earnings: Interest rate contracts $ 5.7 $ 20.3 Foreign currency forward contracts — 1.0 Total expected to be released from Other comprehensive income into earnings $ 5.7 $ 21.3
Schedule of Notional Amounts of Outstanding Derivative Positions	The notional values of derivative instruments designated for hedging held as of March 31, 2024 and September 30, 2023 are as follows: March 31, 2024 September 30, 2023 (in millions) Notional Value Notional Value Derivatives designated as hedging instruments: Interest rate contracts $ 1,000.0 $ 2,000.0 Foreign currency forward contracts: Foreign currency forward contracts to purchase Polish Zloty: Local currency zł 156.1 zł 156.1 USD $ 35.8 $ 34.0 Foreign currency forward contracts to purchase British Pound Sterling: Local currency £ 120.0 £ 168.0 USD $ 147.6 $ 206.9
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The Condensed Consolidated Income Statement effects of derivative instruments designated for hedging held for the three and six months ended March 31, 2024 and 2023 are as follows: (in millions) Income Statement Location Three Months Ended March 31, 2024 Six Months Ended March 31, 2024 Total amounts reclassified from Accumulated Other Comprehensive Income into Income: Interest rate contracts Interest income $ (4.6) $ (20.5) Foreign currency forward contracts Compensation and benefits 1.8 3.7 Total derivatives designated as hedging instruments $ (2.8) $ (16.8) Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring $ — $ — (in millions) Income Statement Location Three Months Ended March 31, 2023 Six Months Ended March 31, 2023 Total amounts reclassified from Accumulated Other Comprehensive Income into Income: Interest rate contracts Interest Income $ (11.6) $ (17.0) Foreign currency forward contracts Compensation and benefits 0.7 0.5 Total derivatives designated as hedging instruments $ (10.9) $ (16.5) Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring $ — $ — The following table sets forth the Company’s net gains/(losses) related to derivative financial instruments for the three and six months ended March 31, 2024 and 2023 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 Condensed Consolidated Income Statements. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Commodities $ 30.4 $ 147.8 $ 117.5 $ 202.0 Foreign exchange 32.6 (72.8) 57.8 (24.0) Interest rate, equities, and indices 15.5 25.6 42.9 33.9 TBA and forward settling securities 25.5 (14.1) (67.7) (37.1) Net gains from derivative contracts $ 104.0 $ 86.5 $ 150.5 $ 174.8
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income	The accumulated other comprehensive income effects of derivative instruments designated for hedging held for three and six months ended March 31, 2024 and 2023 are as follow: Amount of Gain/(Loss) Recognized in Other Comprehensive Income on Derivatives, net of tax (in millions) Three Months Ended March 31, 2024 Three Months Ended March 31, 2023 Derivatives in Cash Flow Hedging Relationships: Interest rate contracts $ 1.7 $ 10.6 Foreign currency forward contracts (2.5) 3.7 Total $ (0.8) $ 14.3 Amount of Gain Recognized in Other Comprehensive Income on Derivatives, net of tax (in millions) Six Months Ended March 31, 2024 Six Months Ended March 31, 2023 Derivatives in Cash Flow Hedging Relationships: Interest rate contracts $ 14.3 $ 9.2 Foreign currency forward contracts 5.6 19.8 Total $ 19.9 $ 29.0

Allowance for Doubtful Accoun_2

Allowance for Doubtful Accounts (Tables)	6 Months Ended
	Mar. 31, 2024
Receivables [Abstract]
Schedule of Financing Receivable, Allowance for Credit Loss	Activity in the allowance for doubtful accounts for the six months ended March 31, 2024 was as follows: (in millions) Balance as of September 30, 2023 $ 59.9 Recovery of bad debts (1) (2.1) Allowance charge-offs (1.2) Other 0.4 Balance as of March 31, 2024 $ 57.0 (1) An additional $1.4 million is included in bad debt expense for the six months ended March 31, 2024 on the consolidated income statement, which is not included in the allowance at the period then ended.

Physical Commodities Inventory

Physical Commodities Inventory (Tables)	6 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Schedule of Inventory	The Company’s inventories consist of finished physical commodities as shown below. (in millions) March 31, September 30, Physical Ag & Energy (1) $ 188.4 $ 146.2 Precious metals - held by broker-dealer subsidiary 166.8 240.3 Precious metals - held by non-broker-dealer subsidiaries 261.7 150.8 Physical commodities inventory, net $ 616.9 $ 537.3 (1) Physical Ag & Energy consists of agricultural commodity inventories, including corn, soybeans, wheat, dried distillers grain, canola, sorghum, coffee, cocoa, cotton, and various energy commodity inventories. Agricultural inventories have reliable, readily determinable and realizable market prices, have relatively insignificant costs of disposal and are available for immediate delivery. The Company records changes to these values in Cost of sales of physical commodities on the Condensed Consolidated Income Statements.

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill allocated to the Company’s operating segments is as follows: (in millions) March 31, September 30, Commercial $ 33.5 $ 33.7 Institutional 9.8 9.8 Retail 5.8 5.8 Payments 10.0 10.0 Total Goodwill $ 59.1 $ 59.3

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [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): March 31, 2024 September 30, 2023 Gross Amount Accumulated Net Amount Gross Amount Accumulated Net Amount Intangible assets subject to amortization Trade/domain names $ 4.1 $ (2.8) $ 1.3 $ 4.1 $ (2.4) $ 1.7 Software programs/platforms 4.9 (3.7) 1.2 28.5 (26.9) 1.6 Client and supplier base 35.2 (23.0) 12.2 38.3 (24.1) 14.2 Total intangible assets subject to amortization 44.2 (29.5) 14.7 70.9 (53.4) 17.5 Intangible assets not subject to amortization Website domains 2.0 — 2.0 1.9 — 1.9 Business licenses 3.7 — 3.7 3.7 — 3.7 Total intangible assets not subject to amortization 5.7 — 5.7 5.6 — 5.6 Total intangible assets $ 49.9 $ (29.5) $ 20.4 $ 76.5 $ (53.4) $ 23.1
Schedule of Expected Amortization Expense	As of March 31, 2024, estimated future amortization expense was as follows: (in millions) Fiscal 2024 (remaining months) $ 3.0 Fiscal 2025 3.7 Fiscal 2026 2.9 Fiscal 2027 2.3 Fiscal 2028 and thereafter 2.8 Total intangible assets subject to amortization $ 14.7

Credit Facilities (Tables)

Credit Facilities (Tables)	6 Months Ended
	Mar. 31, 2024
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 (in millions, except for percentages): (in millions) Amounts Outstanding Borrower Security Renewal/Expiration Date Total Commitment March 31, 2024 September 30, Committed Credit Facilities Senior StoneX Group Inc. Committed Credit Facility - Revolving Line of Credit (1) April 21, 2026 $ 500.0 $ 25.0 (5) $ 150.0 StoneX Financial Inc. None October 29, 2024 190.0 — (5) — StoneX Commodity Solutions LLC Certain assets July 28, 2024 400.0 71.0 (5) 103.0 StoneX Financial Ltd. None October 12, 2024 100.0 50.0 (5) 25.0 StoneX Financial Pte. Ltd. None September 6, 2024 10.0 — (5) — $ 1,200.0 $ 146.0 $ 278.0 Uncommitted Credit Facilities Various 100.4 (5) 55.5 Note Payable to Bank Certain equipment 7.2 (5) 7.5 Senior Secured Notes due 2031 (2) 542.2 (4) — Senior Secured Notes due 2025 (2) 343.7 (3) 342.1 Total outstanding borrowings $ 1,139.5 $ 683.1 (1) The StoneX Group Inc. senior committed credit facility is a revolving facility 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. The maturity date remains April 21, 2025 for one lender representing $17.5 million of the facility commitment. (2) The 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 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) Included in Senior secured borrowings, net on the Condensed Consolidated Balance Sheets. Amounts outstanding under the Notes due 2025 are reported net of unamortized original issue discount and unamortized deferred financing costs of $4.2 million and $5.8 million, in the respective periods presented. The amounts payable under Notes due 2025 have been defeased as the Company has placed the necessary funds in escrow, reported in Restricted cash on the Condensed Consolidated Balance Sheets. (4) Included in Senior secured borrowings, net on the Condensed Consolidated Balance Sheets . Amounts outstanding under the Notes due 2031 are reported net of unamortized deferred financing costs of $7.8 million. (5) Included in Lenders under loans on the Condensed Consolidated Balance Sheets .

Securities and Commodity Fina_2

Securities and Commodity Financing Transactions (Tables)	6 Months Ended
	Mar. 31, 2024
Broker-Dealer [Abstract]
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets	The following tables set forth the carrying value of repurchase agreements, and securities lending agreements by remaining contractual maturity (in millions): March 31, 2024 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 10,183.8 $ 1,183.1 $ 610.6 $ 97.5 $ 12,075.0 Securities loaned 1,458.6 — — — 1,458.6 Gross amount of secured financing $ 11,642.4 $ 1,183.1 $ 610.6 $ 97.5 $ 13,533.6 September 30, 2023 Overnight and Open Less than 30 Days 30-90 Days Over 90 Days Total Securities sold under agreements to repurchase $ 8,300.0 $ 786.8 $ 107.0 $ 2.6 $ 9,196.4 Securities loaned 1,117.3 — — — 1,117.3 Gross amount of secured financing $ 9,417.3 $ 786.8 $ 107.0 $ 2.6 $ 10,313.7
Schedule of Financial Instruments Owned and Pledged as Collateral	The following table sets forth the carrying value of repurchase agreements and securities lending agreements by class of collateral pledged (in millions): Securities sold under agreements to repurchase March 31, 2024 September 30, 2023 U.S. Treasury obligations $ 9,017.4 $ 3,696.1 U.S. government agency obligations 99.1 542.2 Asset-backed obligations 40.9 102.9 Agency mortgage-backed obligations 2,302.5 4,371.6 Foreign government obligations 318.2 148.1 Corporate bonds 296.9 335.5 Total securities sold under agreement to repurchase $ 12,075.0 $ 9,196.4 Securities loaned Equity securities $ 1,458.6 $ 1,117.3 Total securities loaned 1,458.6 1,117.3 Gross amount of secured financing $ 13,533.6 $ 10,313.7 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): March 31, 2024 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Securities purchased under agreements to resell $ 9,807.9 $ (6,063.3) $ 3,744.6 Securities borrowed $ 1,430.6 $ — $ 1,430.6 Securities sold under agreements to repurchase $ 12,075.0 $ (6,063.3) $ 6,011.7 Securities loaned $ 1,458.6 $ — $ 1,458.6 September 30, 2023 Offsetting of collateralized transactions: Gross Amounts Recognized Amounts Offset in the Condensed Consolidated Balance Sheet Net Amounts Presented in the Condensed Consolidated Balance Sheet Securities purchased under agreements to resell $ 7,649.3 $ (4,669.8) $ 2,979.5 Securities borrowed $ 1,129.1 $ — $ 1,129.1 Securities sold under agreements to repurchase $ 9,196.4 $ (4,669.8) $ 4,526.6 Securities loaned $ 1,117.3 $ — $ 1,117.3
Schedule of Carrying Value of Collateral Pledged, Received and Repledged	The following table sets forth the carrying value, which approximates fair value because of its short term nature, of collateral pledged, received and repledged (in millions): March 31, 2024 September 30, 2023 Securities pledged or repledged to cover collateral requirements for tri-party arrangements $ 5,827.0 $ 4,726.6 Securities received as collateral that may be repledged $ 14,131.4 $ 9,180.1 Securities received as collateral that may be repledged covering securities sold short $ 2,563.7 $ 2,461.1 Repledged securities borrowed and client securities held under custodial clearing arrangements to collateralize securities loaned agreements $ 1,298.5 $ 1,097.3

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss, Net (Tables)	6 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Loss	The following table summarizes the changes in accumulated other comprehensive loss, net for the six months ended March 31, 2024. (in millions) Foreign Currency Translation Adjustment Pension Benefits Adjustment Cash Flow Hedge Accumulated Other Comprehensive Loss, net Balances as of September 30, 2023 $ (31.2) $ (2.2) $ (18.4) $ (51.8) Other comprehensive income, net of tax 2.3 — 19.9 22.2 Balances as of March 31, 2024 $ (28.9) $ (2.2) $ 1.5 $ (29.6)

Revenue from Contracts with C_2

Revenue from Contracts with Clients (Tables)	6 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Revenues from contracts with clients as a percentage of total revenues 2.3 % 5.7 % 2.7 % 6.4 % 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 periods indicated. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Revenues from contracts with clients: Commission and clearing fees: Sales-based: Exchange-traded futures and options $ 55.8 $ 55.3 $ 107.2 $ 104.0 OTC derivative brokerage 3.0 4.5 5.8 8.1 Equities and fixed income 14.5 15.6 31.0 31.0 Mutual funds 0.9 0.9 1.6 1.5 Insurance and annuity products 3.7 2.7 5.7 4.5 Other 0.2 1.1 0.1 2.2 Total sales-based commission 78.1 80.1 151.4 151.3 Trailing: Mutual funds 3.2 3.1 6.2 6.1 Insurance and annuity products 3.7 3.5 7.4 7.0 Total trailing commission 6.9 6.6 13.6 13.1 Clearing fees 45.4 40.0 88.7 76.0 Trade conversion fees 3.5 2.0 7.5 4.4 Other 2.3 2.0 4.7 3.9 Total commission and clearing fees 136.2 130.7 265.9 248.7 Consulting, management, and account fees: Underwriting fees 0.1 0.1 0.1 0.3 Asset management fees 12.3 11.1 23.7 21.8 Advisory and consulting fees 9.0 9.0 17.2 17.7 Sweep program fees 11.3 12.9 22.7 24.3 Client account fees 4.3 3.7 8.5 7.5 Other 3.2 3.9 6.5 8.9 Total consulting, management, and account fees 40.2 40.7 78.7 80.5 Sales of physical commodities: Precious metals sales under ASC Topic 606 332.8 746.4 792.0 1,535.0 Total revenues from contracts with clients $ 509.2 $ 917.8 $ 1,136.6 $ 1,864.2 Method of revenue recognition: Point-in-time $ 469.7 $ 878.2 $ 1,059.4 $ 1,787.3 Time elapsed 39.5 39.6 77.2 76.9 Total revenues from contracts with clients 509.2 917.8 1,136.6 1,864.2 Other sources of revenues Physical precious metals under ASC Topic 815 20,067.0 13,703.1 37,229.5 24,182.1 Physical agricultural and energy products 922.1 1,056.7 2,121.3 2,192.5 Principal gains, net 281.8 256.6 575.6 510.8 Interest income 326.0 226.8 616.1 423.0 Total revenues $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Total revenues by primary geographic region: United States $ 1,407.7 $ 1,471.1 $ 3,011.2 $ 3,034.7 Europe 560.2 912.0 1,218.6 1,827.0 South America 105.0 56.5 233.0 118.7 Middle East and Asia 20,025.1 13,720.0 37,200.7 24,186.3 Other 8.1 1.4 15.6 5.9 Total revenues $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Operating revenues by primary geographic region: United States $ 590.0 $ 538.5 $ 1,158.0 $ 1,028.4 Europe 161.1 105.5 296.7 207.0 South America 25.2 32.0 66.4 63.5 Middle East and Asia 33.7 27.1 65.7 54.5 Other 8.2 1.3 15.6 5.8 Total operating revenues $ 818.2 $ 704.4 $ 1,602.4 $ 1,359.2
Schedule of Income and Expense	The following table indicates the relevant income and expense: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Dividend income on long equity positions $ 65.8 $ 3.2 $ 86.0 $ 17.4 Dividend expense on short equity positions 64.7 4.1 83.5 17.3 Dividend (loss)/income, net reported within Principal Gains, net $ 1.1 $ (0.9) $ 2.5 $ 0.1

Other Expenses (Tables)

Other Expenses (Tables)	6 Months Ended
	Mar. 31, 2024
Other Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component	Other expenses consisted of the following, for the periods indicated. Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Non-income taxes $ 2.8 $ 2.2 $ 5.3 $ 6.9 Insurance 3.2 3.0 6.1 5.7 Employee related expenses 1.7 2.3 3.6 5.9 Other direct business expenses 3.5 4.1 7.9 8.1 Membership fees 1.0 1.1 1.9 1.9 Director and public company expenses 0.7 0.5 1.2 1.0 Office expenses 0.5 0.5 1.1 0.9 Other expenses 1.9 1.6 5.1 4.3 Total other expenses $ 15.3 $ 15.3 $ 32.2 $ 34.7

Regulatory Capital Requiremen_2

Regulatory Capital Requirements (Tables)	6 Months Ended
	Mar. 31, 2024
Capital and Other Regulatory Requirements [Abstract]
Schedule of Subsidiaries with Minimum Regulatory Requirements	The following table details those subsidiaries with minimum regulatory requirements in excess of $10.0 million along with the actual balance maintained as of that date. (in millions) As of March 31, 2024 Subsidiary Regulatory Authority Actual Minimum StoneX Financial Inc. SEC and CFTC $ 351.2 $ 257.2 StoneX Financial Ltd. FCA $ 455.5 $ 358.0 Gain Capital Group, LLC CFTC and NFA $ 50.6 $ 29.9 StoneX Financial Pte. Ltd. MAS $ 91.3 $ 25.8 StoneX Markets LLC CFTC and NFA $ 219.2 $ 125.9

Segment Analysis (Tables)

Segment Analysis (Tables)	6 Months Ended
	Mar. 31, 2024
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: Three Months Ended March 31, Six Months Ended March 31, (in millions) 2024 2023 2024 2023 Total revenues: Commercial $ 21,479.1 $ 15,450.7 $ 40,457.1 $ 27,744.2 Institutional 463.4 362.5 899.1 706.0 Retail 111.3 304.6 213.0 620.8 Payments 49.3 49.8 109.9 105.2 Corporate 14.4 2.5 23.6 15.3 Eliminations (11.4) (9.1) (23.6) (18.9) Total $ 22,106.1 $ 16,161.0 $ 41,679.1 $ 29,172.6 Operating revenues: Commercial $ 200.5 $ 220.1 $ 398.9 $ 402.5 Institutional 463.4 362.5 899.1 706.0 Retail 102.0 78.6 194.5 149.1 Payments 49.3 49.8 109.9 105.2 Corporate 14.4 2.5 23.6 15.3 Eliminations (11.4) (9.1) (23.6) (18.9) Total $ 818.2 $ 704.4 $ 1,602.4 $ 1,359.2 Net operating revenues (loss): Commercial $ 164.2 $ 185.1 $ 327.6 $ 337.8 Institutional 149.8 137.9 298.4 281.1 Retail 74.3 50.8 141.3 94.7 Payments 46.8 47.4 105.0 100.7 Corporate (12.8) (21.8) (28.4) (32.9) Total $ 422.3 $ 399.4 $ 843.9 $ 781.4 Net contribution: (Revenues less cost of sales of physical commodities, transaction-based clearing expenses, variable compensation, introducing broker commissions and interest expense) Commercial $ 119.3 $ 140.9 $ 245.7 $ 256.6 Institutional 102.5 89.3 202.7 183.9 Retail 69.9 48.4 132.5 87.6 Payments 37.3 38.1 84.9 80.2 Total $ 329.0 $ 316.7 $ 665.8 $ 608.3 Segment income: (Net contribution less non-variable direct segment costs) Commercial $ 85.6 $ 102.9 $ 172.8 $ 185.7 Institutional 61.3 55.8 126.5 117.8 Retail 33.2 4.8 61.9 0.6 Payments 24.6 15.9 59.6 48.2 Total $ 204.7 $ 179.4 $ 420.8 $ 352.3 Reconciliation of segment income to income before tax: Segment income $ 204.7 $ 179.4 $ 420.8 $ 352.3 Net operating revenue (loss) with Corporate (12.8) (21.8) (28.4) (32.9) Overhead costs and expenses (119.6) (100.1) (224.4) (189.8) Gain on acquisition — — — 23.5 Income before tax $ 72.3 $ 57.5 $ 168.0 $ 153.1 (in millions) As of March 31, 2024 As of September 30, 2023 Total assets: Commercial $ 5,154.8 $ 4,676.3 Institutional 17,684.1 15,059.3 Retail 1,111.8 1,014.2 Payments 433.1 376.6 Corporate 1,267.2 812.3 Total $ 25,651.0 $ 21,938.7

Basis of Presentation and Con_3

Basis of Presentation and Consolidation and Accounting Standards Adopted (Details) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended
	Nov. 07, 2023	Oct. 31, 2022 USD ($)	Mar. 31, 2024 USD ($) country client $ / shares	Mar. 31, 2023 USD ($)	Mar. 31, 2024 USD ($) country client $ / shares	Mar. 31, 2023 USD ($)	Mar. 01, 2024	Sep. 30, 2023 $ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of countries in which entity operates (more than) | country			180		180
Number of commercial and institutional clients (more than) | client			54,000		54,000
Number of retail clients | client			400,000		400,000
Stock split, conversion ratio	1.5
Common stock - par value (in dollar per share) | $ / shares			$ 0.01		$ 0.01			$ 0.01
Gain on acquisition and other gains			$ 0	$ 0	$ 0	$ 23.5
Senior Secured Notes due 2025 | Senior Notes
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Debt instrument, interest rate, stated percentage			8.625%		8.625%		8.625%
Cotton Distributors Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Fair value of identifiable net assets acquired		$ 66.2
Purchase price		$ 42.7
Gain on acquisition and other gains						$ 23.5
Retail Segment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of countries in which entity operates (more than) | country			180		180

Earnings per Share - EPS Reconc

Earnings per Share - EPS Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net income	$ 53.1	$ 41.7	$ 122.2	$ 118.3
Less: Allocation to participating securities	(1.9)	(1.5)	(4.3)	(4)
Net income allocated to common stockholders, basic	51.2	40.2	117.9	114.3
Net income allocated to common stockholders, diluted	$ 51.2	$ 40.2	$ 117.9	$ 114.3
Denominator:
Common shares outstanding (in shares)	30,473,856	29,895,041	30,352,824	29,775,078
Dilutive potential common shares outstanding:
Share-based awards (in shares)	1,025,087	1,036,751	1,020,915	1,055,792
Diluted weighted - average common shares (in shares)	31,498,943	30,931,792	31,373,739	30,830,870

Earnings per Share - Narrative

Earnings per Share - Narrative (Details) - shares	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share [Abstract]
Antidilutive securities (in shares)	1,849,986	185,058	1,321,535	272,094

Assets and Liabilities, at Fa_3

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 4.1	$ 5.8
Securities and other assets segregated under federal and other regulations	2,838.4	2,426.3
Financial instruments owned	5,666.5	5,044.8
Physical commodities inventory	616.9	537.3
Accounts payable and other accrued liabilities	491.8	533
Financial instruments sold, not yet purchased	3,223	3,085.6
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	118	66.5
Securities and other assets segregated under federal and other regulations	4.1	5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	4,157.3	4,248.3
Receivables from clients, net - Derivatives	(3.4)	(7.9)
Financial instruments owned	5,666.5	5,044.8
Total assets at fair value	10,297.7	9,744
Accounts payable and other accrued liabilities	1.7
Payables to clients - Derivatives	585.6	79.8
Total liabilities at fair value	3,789	3,177.1
Fair Value, Recurring | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities		1.5
Fair Value, Recurring | TBA and forward settling securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	1	16.1
Fair Value, Recurring | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(22.3)	(5.9)
Fair Value, Recurring | Payable to broker-dealers, clearing organizations and counterparties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(21.3)	10.2
Fair Value, Recurring | Physical commodities inventory
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	355.2	386.5
Fair Value, Recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	481.2	334.3
Financial instruments sold, not yet purchased	280.6	236.1
Fair Value, Recurring | Corporate and municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	339.9	284.2
Financial instruments sold, not yet purchased	174.4	81.6
Fair Value, Recurring | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	517.7	531.7
Financial instruments sold, not yet purchased	2,239.4	2,409.3
Fair Value, Recurring | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	466.2	451.7
Financial instruments sold, not yet purchased	27.2	5.1
Fair Value, Recurring | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	41.3	43.3
Financial instruments sold, not yet purchased	45	21.5
Fair Value, Recurring | Agency mortgage-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	3,186	2,865.8
Financial instruments sold, not yet purchased	7.6	31.7
Fair Value, Recurring | Asset-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	136.9	138.8
Financial instruments sold, not yet purchased	5.3
Fair Value, Recurring | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	360.5	268.5
Financial instruments sold, not yet purchased	436.7	261.2
Fair Value, Recurring | Commodities leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	15.3	16
Fair Value, Recurring | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	74.9	54.7
Fair Value, Recurring | Exchange firm common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	12.9	12
Fair Value, Recurring | Cash flow hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	7.1	1.7
Financial instruments sold, not yet purchased	5.7	27.1
Fair Value, Recurring | Mutual funds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	26.6	42.1
Fair Value, Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased	1.1	12
Fair Value, Recurring | TBA and forward settling securities
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	2.9	41.8
Fair Value, Recurring | Foreign government obligations
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	17.8
Fair Value, Recurring | U.S. Treasury obligations
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	3,405.5	4,023.8
Fair Value, Recurring | Derivatives
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	729.9	164.9
Fair Value, Recurring | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities and other assets segregated under federal and other regulations	4.1	5.8
Fair Value, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	18.1	8.7
Fair Value, Recurring | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	99.9	57.8
Fair Value, Recurring | Netting
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Securities and other assets segregated under federal and other regulations	0	0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	(5,375)	(6,500.2)
Receivables from clients, net - Derivatives	(704.3)	(630.9)
Financial instruments owned	(600.5)	(600.2)
Total assets at fair value	(6,679.8)	(7,731.3)
Accounts payable and other accrued liabilities	0
Payables to clients - Derivatives	(4,124)	(5,577.1)
Financial instruments sold, not yet purchased	(546.7)	(510.4)
Total liabilities at fair value	(6,628.7)	(7,639)
Fair Value, Recurring | Netting | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities		0
Fair Value, Recurring | Netting | TBA and forward settling securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(21.9)	(31.4)
Fair Value, Recurring | Netting | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(1,936.1)	(1,520.1)
Fair Value, Recurring | Netting | Payable to broker-dealers, clearing organizations and counterparties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	(1,958)	(1,551.5)
Fair Value, Recurring | Netting | Physical commodities inventory
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
Fair Value, Recurring | Netting | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | Corporate and municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | Agency mortgage-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | Asset-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0
Fair Value, Recurring | Netting | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	(600.5)	(600.2)
Financial instruments sold, not yet purchased	(546.7)	(510.4)
Fair Value, Recurring | Netting | Commodities leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Netting | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Netting | Exchange firm common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Netting | Cash flow hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | Mutual funds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Netting | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Netting | TBA and forward settling securities
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	(22.4)	(31.7)
Fair Value, Recurring | Netting | Foreign government obligations
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, Recurring | Netting | U.S. Treasury obligations
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, Recurring | Netting | Derivatives
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	(5,352.6)	(6,468.5)
Fair Value, Recurring | Netting | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities and other assets segregated under federal and other regulations	0	0
Fair Value, Recurring | Netting | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Recurring | Netting | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	118	66.5
Securities and other assets segregated under federal and other regulations	4.1	5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	7,914.4	9,539.1
Receivables from clients, net - Derivatives	167	61.7
Financial instruments owned	1,137.8	1,005.6
Total assets at fair value	9,508.1	10,919
Accounts payable and other accrued liabilities	0
Payables to clients - Derivatives	4,483.9	5,430.7
Financial instruments sold, not yet purchased	2,569.5	2,663.8
Total liabilities at fair value	7,220.2	8,206.7
Fair Value, Recurring | Level 1 | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities		0
Fair Value, Recurring | Level 1 | TBA and forward settling securities
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, Recurring | Level 1 | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	166.8	112.2
Fair Value, Recurring | Level 1 | Payable to broker-dealers, clearing organizations and counterparties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	166.8	112.2
Fair Value, Recurring | Level 1 | Physical commodities inventory
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	166.8	240.3
Fair Value, Recurring | Level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	466.7	324
Financial instruments sold, not yet purchased	275.8	230.6
Fair Value, Recurring | Level 1 | Corporate and municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 1 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	517.7	531.7
Financial instruments sold, not yet purchased	2,239.4	2,409.3
Fair Value, Recurring | Level 1 | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 1 | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	41.3	43.3
Financial instruments sold, not yet purchased	45	21.5
Fair Value, Recurring | Level 1 | Agency mortgage-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 1 | Asset-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0
Fair Value, Recurring | Level 1 | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0.5	0.6
Financial instruments sold, not yet purchased	9.3	2.4
Fair Value, Recurring | Level 1 | Commodities leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 1 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	74.9	54.7
Fair Value, Recurring | Level 1 | Exchange firm common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	12.9	12
Fair Value, Recurring | Level 1 | Cash flow hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 1 | Mutual funds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	23.8	39.3
Fair Value, Recurring | Level 1 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 1 | TBA and forward settling securities
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, Recurring | Level 1 | Foreign government obligations
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	17.8
Fair Value, Recurring | Level 1 | U.S. Treasury obligations
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	3,405.5	4,023.8
Fair Value, Recurring | Level 1 | Derivatives
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	4,489.9	5,497.5
Fair Value, Recurring | Level 1 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities and other assets segregated under federal and other regulations	4.1	5.8
Fair Value, Recurring | Level 1 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	18.1	8.7
Fair Value, Recurring | Level 1 | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	99.9	57.8
Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Securities and other assets segregated under federal and other regulations	0	0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net	1,617.9	1,209.4
Receivables from clients, net - Derivatives	533.9	561.3
Financial instruments owned	5,126.4	4,636.6
Total assets at fair value	7,466.6	6,553.5
Accounts payable and other accrued liabilities	0
Payables to clients - Derivatives	225.7	226.2
Financial instruments sold, not yet purchased	1,199.1	931.1
Total liabilities at fair value	3,194.7	2,606.8
Fair Value, Recurring | Level 2 | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities		0
Fair Value, Recurring | Level 2 | TBA and forward settling securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	22.9	47.5
Fair Value, Recurring | Level 2 | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	1,747	1,402
Fair Value, Recurring | Level 2 | Payable to broker-dealers, clearing organizations and counterparties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable to broker-dealers, clearing organizations and counterparties	1,769.9	1,449.5
Fair Value, Recurring | Level 2 | Physical commodities inventory
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	188.4	146.2
Fair Value, Recurring | Level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	14.5	10.3
Financial instruments sold, not yet purchased	4.8	5.5
Fair Value, Recurring | Level 2 | Corporate and municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	339.9	284.2
Financial instruments sold, not yet purchased	174.4	81.6
Fair Value, Recurring | Level 2 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 2 | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	466.2	451.7
Financial instruments sold, not yet purchased	27.2	5.1
Fair Value, Recurring | Level 2 | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 2 | Agency mortgage-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	3,186	2,865.8
Financial instruments sold, not yet purchased	7.6	31.7
Fair Value, Recurring | Level 2 | Asset-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	136.9	138.8
Financial instruments sold, not yet purchased	5.3
Fair Value, Recurring | Level 2 | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	960.5	868.1
Financial instruments sold, not yet purchased	974.1	769.2
Fair Value, Recurring | Level 2 | Commodities leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	15.3	16
Fair Value, Recurring | Level 2 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 2 | Exchange firm common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 2 | Cash flow hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	7.1	1.7
Financial instruments sold, not yet purchased	5.7	27.1
Fair Value, Recurring | Level 2 | Mutual funds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 2 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased	0	10.9
Fair Value, Recurring | Level 2 | TBA and forward settling securities
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	25.3	73.5
Fair Value, Recurring | Level 2 | Foreign government obligations
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, Recurring | Level 2 | U.S. Treasury obligations
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, Recurring | Level 2 | Derivatives
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	1,592.6	1,135.9
Fair Value, Recurring | Level 2 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities and other assets segregated under federal and other regulations	0	0
Fair Value, Recurring | Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Recurring | Level 2 | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Securities and other assets 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	2.8	2.8
Total assets at fair value	2.8	2.8
Accounts payable and other accrued liabilities	1.7
Payables to clients - Derivatives	0
Financial instruments sold, not yet purchased	1.1	1.1
Total liabilities at fair value	2.8	2.6
Fair Value, Recurring | Level 3 | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable and other accrued liabilities		1.5
Fair Value, Recurring | Level 3 | TBA and forward settling securities
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, Recurring | Level 3 | Derivatives
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, Recurring | Level 3 | Payable to broker-dealers, clearing organizations and counterparties
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, Recurring | Level 3 | Physical commodities inventory
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Physical commodities inventory	0	0
Fair Value, Recurring | Level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Corporate and municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Foreign government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Agency mortgage-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Asset-backed obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0
Fair Value, Recurring | Level 3 | Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Commodities leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 3 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 3 | Exchange firm common stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Fair Value, Recurring | Level 3 | Cash flow hedges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	0	0
Financial instruments sold, not yet purchased	0	0
Fair Value, Recurring | Level 3 | Mutual funds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned	2.8	2.8
Fair Value, Recurring | Level 3 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased	1.1	1.1
Fair Value, Recurring | Level 3 | TBA and forward settling securities
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, Recurring | Level 3 | Foreign government obligations
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, Recurring | Level 3 | U.S. Treasury obligations
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, Recurring | Level 3 | Derivatives
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, Recurring | Level 3 | Commodities warehouse receipts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities and other assets segregated under federal and other regulations	0	0
Fair Value, Recurring | Level 3 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Fair Value, Recurring | Level 3 | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 0	$ 0

Assets and Liabilities, at Fa_4

Assets and Liabilities, at Fair Value - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2024	Mar. 01, 2024	Sep. 30, 2023
Senior Secured Notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value	$ 343.7		$ 342.1
Senior Secured Notes due 2025 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate, stated percentage	8.625%	8.625%
Senior Secured Notes due 2025 | Level 2 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 349.4
Senior Secured Notes due 2031
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value	542.2		$ 0
Senior Secured Notes due 2031 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, interest rate, stated percentage		7.875%
Senior Secured Notes due 2031 | Level 2 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 557.8

Financial Instruments with Of_3

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2024	Sep. 30, 2023
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Financial instruments sold, not yet purchased	$ 3,223	$ 3,085.6
Interest rate contracts
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Maximum length of time hedged in cash flow hedge	1 year
Foreign currency forward contracts
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Maximum length of time hedged in cash flow hedge	2 years
Fair Value, Recurring | Derivatives
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Financial instruments sold, not yet purchased	$ 436.7	261.2
Fair Value, Recurring | Derivatives | Not Designated as Hedging Instrument
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Financial instruments sold, not yet purchased	$ 436.7	$ 261.2

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) contract in Millions, $ in Millions	Mar. 31, 2024 USD ($) contract	Sep. 30, 2023 USD ($) contract
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	$ 7,776.8	$ 8,200.3
Derivative liability, fair value, gross liability	7,635.4	8,017.3
Impact of netting and collateral asset	(6,679.8)	(7,731.3)
Impact of netting and collateral liability	$ (6,628.7)	$ (7,639)
Derivative, number of instruments held | contract	11.8	13.4
Total fair value included in Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	$ 732.8	$ 206.7
Total fair value included in Receivable from clients, net
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	(3.4)	(7.9)
Total fair value included in Financial instruments owned, at fair value
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	367.6	270.2
Total fair value included in Payables to clients
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	585.6	79.8
Total fair value included in Payables to broker-dealers, clearing organizations and counterparties
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	(21.3)	10.2
Total fair value included in Financial instruments sold, not yet purchased, at fair value
Derivatives, Fair Value [Line Items]
Derivative, fair value, net	442.4	288.3
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	7,769.7	8,198.6
Derivative liability, fair value, gross liability	7,629.7	7,990.2
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	7.1	1.7
Derivative liability, fair value, gross liability	5.7	27.1
Exchange-traded commodity derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	1,732.5	1,907
Derivative liability, fair value, gross liability	1,725.8	1,890.3
OTC commodity derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	2,319	1,523.3
Derivative liability, fair value, gross liability	2,269.6	1,456
Exchange-traded foreign exchange derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	1.4	4.3
Derivative liability, fair value, gross liability	1.4	4.3
OTC foreign exchange derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	326.1	497.1
Derivative liability, fair value, gross liability	280.4	455.3
Exchange-traded interest rate derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	782.2	1,507.6
Derivative liability, fair value, gross liability	791.5	1,509.8
OTC interest rate derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	270.2	417.6
Derivative liability, fair value, gross liability	270.2	417.6
OTC interest rate derivatives | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	0	0
Derivative liability, fair value, gross liability	5.7	24.6
Exchange-traded equity index derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	2,141.3	2,140.9
Derivative liability, fair value, gross liability	2,141.3	2,140.9
OTC equity and indices derivatives | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	171.7	127.3
Derivative liability, fair value, gross liability	126.6	68.5
TBA and forward settling securities | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	25.3	73.5
Derivative liability, fair value, gross liability	22.9	47.5
Foreign currency forward contracts | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	7.1	1.7
Derivative liability, fair value, gross liability	$ 0	$ 2.5

Financial Instruments with Of_5

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Fair Values of Derivative Instruments Designated for Hedging Held (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2024	Sep. 30, 2023
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 7,776.8	$ 8,200.3
Liability Derivatives	7,635.4	8,017.3
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Asset Derivatives	7.1	1.7
Derivative assets expected to be released from Other comprehensive income into current earnings:	5.6	1.4
Liability Derivatives	5.7	27.1
Derivative liabilities expected to be released from Other comprehensive income into current earnings:	5.7	21.3
Designated as Hedging Instrument | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Asset Derivatives	7.1	1.7
Derivative assets expected to be released from Other comprehensive income into current earnings:	5.6	1.4
Liability Derivatives	0	2.5
Derivative liabilities expected to be released from Other comprehensive income into current earnings:	0	1
Designated as Hedging Instrument | Interest rate contracts
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	0
Liability Derivatives	5.7	24.6
Derivative liabilities expected to be released from Other comprehensive income into current earnings:	$ 5.7	$ 20.3

Financial Instruments with Of_6

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Notional Values For Derivatives Instrument (Details) - Designated as Hedging Instrument £ in Millions, zł in Millions, $ in Millions	Mar. 31, 2024 USD ($)	Mar. 31, 2024 PLN (zł)	Mar. 31, 2024 GBP (£)	Sep. 30, 2023 USD ($)	Sep. 30, 2023 PLN (zł)	Sep. 30, 2023 GBP (£)
Interest rate contracts
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Derivative, notional amount	$ 1,000			$ 2,000
Foreign currency forward contracts | Polish Zloty
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Derivative, notional amount	35.8	zł 156.1		34	zł 156.1
Foreign currency forward contracts | British Pound Sterling
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]
Derivative, notional amount	$ 147.6		£ 120	$ 206.9		£ 168

Financial Instruments with Of_7

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Income Statement Effects of Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total derivatives designated as hedging instruments	$ (2.8)	$ (10.9)	$ (16.8)	$ (16.5)
Amount of gain reclassified from accumulated other comprehensive income into income as a result of a forecasted transaction that is no longer probable of occurring	0	0	0	0
Interest rate contracts
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total derivatives designated as hedging instruments	15.5	25.6	42.9	33.9
Interest rate contracts | Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total derivatives designated as hedging instruments	(4.6)	(11.6)	(20.5)	(17)
Foreign currency forward contracts | Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Total derivatives designated as hedging instruments	$ 1.8	$ 0.7	$ 3.7	$ 0.5

Financial Instruments with Of_8

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Accumulated Other Comprehensive Income Effects of Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain/(Loss) Recognized in Other Comprehensive Income on Derivatives, net of tax	$ (0.8)	$ 14.3	$ 19.9	$ 29
Interest rate contracts
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain/(Loss) Recognized in Other Comprehensive Income on Derivatives, net of tax	1.7	10.6	14.3	9.2
Foreign currency forward contracts
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Amount of Gain/(Loss) Recognized in Other Comprehensive Income on Derivatives, net of tax	$ (2.5)	$ 3.7	$ 5.6	$ 19.8

Financial Instruments with Of_9

Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Realized Gains/Losses on Derivative Contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Commodities
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 30.4	$ 147.8	$ 117.5	$ 202
Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	32.6	(72.8)	57.8	(24)
Interest rate, equities, and indices
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	15.5	25.6	42.9	33.9
TBA and forward settling securities
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	25.5	(14.1)	(67.7)	(37.1)
Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 104	$ 86.5	$ 150.5	$ 174.8

Allowance for Doubtful Accoun_3

Allowance for Doubtful Accounts - Narrative (Details) - USD ($)	Mar. 31, 2024	Sep. 30, 2023
Receivables [Abstract]
Allowance for doubtful accounts - deposits with and receivables from broker-dealers, clearings organizations, and counterparties	$ 0	$ 100,000
Allowance for doubtful accounts receivable	57,000,000	59,800,000
Allowance for doubtful accounts related to notes receivable	$ 0	$ 0

Allowance for Doubtful Accoun_4

Allowance for Doubtful Accounts - Allowance for Bad Debts (Details) $ in Millions	6 Months Ended
	Mar. 31, 2024 USD ($)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance as of September 30, 2023	$ 59.9
Recovery of bad debts	(2.1)
Allowance charge-offs	(1.2)
Other	0.4
Balance as of March 31, 2024	57
Bad debt expense	$ 1.4

Physical Commodities Inventor_2

Physical Commodities Inventory - Physical Commodities Inventory (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Inventory [Line Items]
Physical Ag & Energy	$ 188.4	$ 146.2
Precious metals - held by broker-dealer subsidiary	355.2	386.5
Physical commodities inventory, net	616.9	537.3
Physical Commodities Inventory - Precious Metals
Inventory [Line Items]
Precious metals - held by broker-dealer subsidiary	166.8	240.3
Precious metals - held by non-broker-dealer subsidiaries	$ 261.7	$ 150.8

Goodwill - Goodwill by Segment

Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Goodwill [Line Items]
Total Goodwill	$ 59.1	$ 59.3
Commercial
Goodwill [Line Items]
Total Goodwill	33.5	33.7
Institutional
Goodwill [Line Items]
Total Goodwill	9.8	9.8
Retail
Goodwill [Line Items]
Total Goodwill	5.8	5.8
Payments
Goodwill [Line Items]
Total Goodwill	$ 10	$ 10

Goodwill - Narrative (Details)

Goodwill - Narrative (Details) $ in Millions	6 Months Ended
	Mar. 31, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, foreign exchange translation	$ 0.2

Intangible Assets - Gross and N

Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross amount	$ 44.2	$ 70.9
Finite-lived intangible assets, accumulated amortization	(29.5)	(53.4)
Total intangible assets subject to amortization	14.7	17.5
Indefinite-lived intangible assets	5.7	5.6
Intangible assets, gross amount	49.9	76.5
Total intangible assets, net amount	20.4	23.1
Website domains
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived license agreements	2	1.9
Business licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	3.7	3.7
Trade/domain names
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived trade/domain names, gross amount	4.1	4.1
Finite-lived intangible assets, accumulated amortization	(2.8)	(2.4)
Total intangible assets subject to amortization	1.3	1.7
Software programs/platforms
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived software programs/platforms, gross amount	4.9	28.5
Finite-lived intangible assets, accumulated amortization	(3.7)	(26.9)
Total intangible assets subject to amortization	1.2	1.6
Client and supplier base
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived customer base, gross amount	35.2	38.3
Finite-lived intangible assets, accumulated amortization	(23)	(24.1)
Total intangible assets subject to amortization	$ 12.2	$ 14.2

Intangible Assets - Narrative (

Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 2.1	$ 4.1	$ 4.1	$ 8
Write off amortized intangible assets			$ 27.8

Intangible Assets - Finite-Live

Intangible Assets - Finite-Lived Intangible Assets Future Amortization Expense (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Fiscal 2024 (remaining months)	$ 3
Fiscal 2025	3.7
Fiscal 2026	2.9
Fiscal 2027	2.3
Fiscal 2028 and thereafter	2.8
Total intangible assets subject to amortization	$ 14.7	$ 17.5

Credit Facilities - Senior Secu

Credit Facilities - Senior Secured Notes (Details) - USD ($)	Mar. 31, 2024	Mar. 01, 2024
Senior Secured Notes due 2031 | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 550,000,000
Debt instrument, interest rate, stated percentage		7.875%
Debt instrument offering price, percentage		100%
Debt issuance costs, gross		$ 7,900,000
Senior Secured Notes due 2025 | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 363,000,000
Debt instrument, interest rate, stated percentage	8.625%	8.625%
Debt issuance costs, gross		$ 9,500,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity under credit facilities	$ 1,200,000,000

Credit Facilities - Credit Faci

Credit Facilities - Credit Facilities and Financing Bridge Commitment (Details)	Mar. 31, 2024 USD ($) lender	Sep. 30, 2023 USD ($)
Line of Credit Facility [Line Items]
Uncommitted Credit Facilities	$ 100,400,000	$ 55,500,000
Note Payable to Bank	7,200,000	7,500,000
Total outstanding borrowings	1,139,500,000	683,100,000
Senior StoneX Group Inc. Committed Credit Facility - Revolving Line of Credit | Secured Debt
Line of Credit Facility [Line Items]
Line of credit facility borrowing	$ 17,500,000
Number of lender | lender	1
Senior Secured Notes due 2025
Line of Credit Facility [Line Items]
Senior secured notes	$ 343,700,000	342,100,000
Senior Secured Notes due 2025 | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, unamortized discount (premium) and debt issuance costs, net	4,200,000	5,800,000
Senior Secured Notes due 2031
Line of Credit Facility [Line Items]
Senior secured notes	542,200,000	0
Senior Secured Notes due 2031 | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, unamortized discount (premium) and debt issuance costs, net	7,800,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity under credit facilities	1,200,000,000
Amount outstanding	146,000,000	278,000,000
Revolving Credit Facility | Senior StoneX Group Inc. Committed Credit Facility - Revolving Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility borrowing	500,000,000
Long-term line of credit, noncurrent	25,000,000	150,000,000
Revolving Credit Facility | StoneX Financial Inc.
Line of Credit Facility [Line Items]
Line of credit facility borrowing	190,000,000
Line of credit facility	0	0
Revolving Credit Facility | StoneX Commodity Solutions LLC
Line of Credit Facility [Line Items]
Line of credit facility borrowing	400,000,000
Line of credit facility	71,000,000	103,000,000
Revolving Credit Facility | StoneX Financial Ltd.
Line of Credit Facility [Line Items]
Line of credit facility borrowing	100,000,000
Line of credit facility	50,000,000	25,000,000
Revolving Credit Facility | StoneX Financial Pte. Ltd.
Line of Credit Facility [Line Items]
Line of credit facility borrowing	10,000,000
Line of credit facility	$ 0	$ 0

Securities and Commodity Fina_3

Securities and Commodity Financing Transactions - Collateral Maturities of Gross Obligations (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 12,075	$ 9,196.4
Securities loaned	1,458.6	1,117.3
Gross amount of secured financing	13,533.6	10,313.7
Overnight and Open
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	10,183.8	8,300
Securities loaned	1,458.6	1,117.3
Gross amount of secured financing	11,642.4	9,417.3
Less than 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	1,183.1	786.8
Securities loaned	0	0
Gross amount of secured financing	1,183.1	786.8
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	610.6	107
Securities loaned	0	0
Gross amount of secured financing	610.6	107
Over 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	97.5	2.6
Securities loaned	0	0
Gross amount of secured financing	$ 97.5	$ 2.6

Securities and Commodity Fina_4

Securities and Commodity Financing Transactions - Underlying Collateral Types of Gross Obligations (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 12,075	$ 9,196.4
Securities loaned	1,458.6	1,117.3
Gross amount of secured financing	13,533.6	10,313.7
U.S. Treasury obligations
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	9,017.4	3,696.1
U.S. government agency obligations
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	99.1	542.2
Asset-backed obligations
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	40.9	102.9
Agency mortgage-backed obligations
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	2,302.5	4,371.6
Foreign government obligations
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	318.2	148.1
Corporate bonds
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	296.9	335.5
Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Securities loaned	$ 1,458.6	$ 1,117.3

Securities and Commodity Fina_5

Securities and Commodity Financing Transactions - Netting of Securities Purchased Under Agreements (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Broker-Dealer [Abstract]
Securities purchased under agreements to resell, gross	$ 9,807.9	$ 7,649.3
Securities purchased under agreements to resell, offset	(6,063.3)	(4,669.8)
Securities purchased under agreements to resell, net	3,744.6	2,979.5
Securities borrowed, gross	1,430.6	1,129.1
Securities borrowed, net	1,430.6	1,129.1
Securities sold under agreements to repurchase, gross	12,075	9,196.4
Securities sold under agreements to repurchase, offset	(6,063.3)	(4,669.8)
Securities sold under agreements to repurchase, net	6,011.7	4,526.6
Securities loaned, gross	1,458.6	1,117.3
Securities loaned, net	$ 1,458.6	$ 1,117.3

Securities and Commodity Fina_6

Securities and Commodity Financing Transactions - Carrying Value of Collateral Pledged, Received and Repledged (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Assets Sold under Agreements to Repurchase [Line Items]
Securities pledged or repledged to cover collateral requirements for tri-party arrangements	$ 5,666.5	$ 5,044.8
Securities received as collateral that may be repledged	14,131.4	9,180.1
Securities received as collateral that may be repledged covering securities sold short	2,563.7	2,461.1
Asset Pledged as Collateral with Right
Assets Sold under Agreements to Repurchase [Line Items]
Repledged securities borrowed and client securities held under custodial clearing arrangements to collateralize securities loaned agreements	1,298.5	1,097.3
Tri-party Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Securities pledged or repledged to cover collateral requirements for tri-party arrangements	$ 5,827	$ 4,726.6

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Loss contingency, range of possible loss, portion not accrued	$ 11.1
Loss contingency accrual	3.5
Self insurance reserve and dental claims	$ 1.7

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,482.8	$ 1,176.6	$ 1,379.1	$ 1,070.1
Other comprehensive income, net of tax	(5.4)	17.5	22.2	40.4
Ending balance	1,542.6	1,247.3	1,542.6	1,247.3
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(31.2)
Other comprehensive income, net of tax			2.3
Ending balance	(28.9)		(28.9)
Pension Benefits Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(2.2)
Other comprehensive income, net of tax			0
Ending balance	(2.2)		(2.2)
Cash Flow Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(18.4)
Other comprehensive income, net of tax			19.9
Ending balance	1.5		1.5
Accumulated Other Comprehensive Loss, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(24.2)	(67.7)	(51.8)	(90.6)
Other comprehensive income, net of tax	(5.4)	17.5	22.2	40.4
Ending balance	$ (29.6)	$ (50.2)	$ (29.6)	$ (50.2)

Revenue from Contracts with C_3

Revenue from Contracts with Clients - Revenue from Contracts with Clients (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 509.2	$ 917.8	$ 1,136.6	$ 1,864.2
Principal gains, net	281.8	256.6	575.6	510.8
Interest income	326	226.8	616.1	423
Total revenues	22,106.1	16,161	41,679.1	29,172.6
Total operating revenues	818.2	704.4	1,602.4	1,359.2
United States
Disaggregation of Revenue [Line Items]
Total revenues	1,407.7	1,471.1	3,011.2	3,034.7
Total operating revenues	590	538.5	1,158	1,028.4
Europe
Disaggregation of Revenue [Line Items]
Total revenues	560.2	912	1,218.6	1,827
Total operating revenues	161.1	105.5	296.7	207
South America
Disaggregation of Revenue [Line Items]
Total revenues	105	56.5	233	118.7
Total operating revenues	25.2	32	66.4	63.5
Middle East and Asia
Disaggregation of Revenue [Line Items]
Total revenues	20,025.1	13,720	37,200.7	24,186.3
Total operating revenues	33.7	27.1	65.7	54.5
Other
Disaggregation of Revenue [Line Items]
Total revenues	8.1	1.4	15.6	5.9
Total operating revenues	8.2	1.3	15.6	5.8
Point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	469.7	878.2	1,059.4	1,787.3
Time elapsed
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	39.5	39.6	77.2	76.9
Exchange-traded futures and options
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	55.8	55.3	107.2	104
OTC derivative brokerage
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3	4.5	5.8	8.1
Equities and fixed income
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	14.5	15.6	31	31
Mutual funds
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0.9	0.9	1.6	1.5
Insurance and annuity products
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.7	2.7	5.7	4.5
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0.2	1.1	0.1	2.2
Total sales-based commission
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	78.1	80.1	151.4	151.3
Mutual funds
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.2	3.1	6.2	6.1
Insurance and annuity products
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.7	3.5	7.4	7
Total trailing commission
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	6.9	6.6	13.6	13.1
Clearing fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	45.4	40	88.7	76
Trade conversion fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.5	2	7.5	4.4
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2.3	2	4.7	3.9
Total commission and clearing fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	136.2	130.7	265.9	248.7
Total revenues	136.2	130.7	265.9	248.7
Underwriting fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0.1	0.1	0.1	0.3
Asset management fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12.3	11.1	23.7	21.8
Advisory and consulting fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	9	9	17.2	17.7
Sweep program fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11.3	12.9	22.7	24.3
Client account fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	4.3	3.7	8.5	7.5
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3.2	3.9	6.5	8.9
Total consulting, management, and account fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	40.2	40.7	78.7	80.5
Total revenues	40.2	40.7	78.7	80.5
Precious metals sales under ASC Topic 606
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	332.8	746.4	792	1,535
Physical precious metals under ASC Topic 815
Disaggregation of Revenue [Line Items]
Sales of physical commodities	20,067	13,703.1	37,229.5	24,182.1
Physical agricultural and energy products
Disaggregation of Revenue [Line Items]
Sales of physical commodities	$ 922.1	$ 1,056.7	$ 2,121.3	$ 2,192.5
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Clients
Disaggregation of Revenue [Line Items]
Revenues from contracts with clients as a percentage of total revenues	2.30%	5.70%	2.70%	6.40%

Revenue from Contracts with C_4

Revenue from Contracts with Clients - Schedule of Principal Gains, Net Related To Income and Expense of Dividends (Details) - Equity securities - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Dividend (loss)/income, net reported within Principal Gains, net	$ 1.1	$ (0.9)	$ 2.5	$ 0.1
Dividend income on long equity positions
Disaggregation of Revenue [Line Items]
Dividend (loss)/income, net reported within Principal Gains, net	65.8	3.2	86	17.4
Dividend expense on short equity positions
Disaggregation of Revenue [Line Items]
Dividend (loss)/income, net reported within Principal Gains, net	$ (64.7)	$ (4.1)	$ (83.5)	$ (17.3)

Other Expenses - Other Expenses

Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Other Expenses [Abstract]
Non-income taxes	$ 2.8	$ 2.2	$ 5.3	$ 6.9
Insurance	3.2	3	6.1	5.7
Employee related expenses	1.7	2.3	3.6	5.9
Other direct business expenses	3.5	4.1	7.9	8.1
Membership fees	1	1.1	1.9	1.9
Director and public company expenses	0.7	0.5	1.2	1
Office expenses	0.5	0.5	1.1	0.9
Other expenses	1.9	1.6	5.1	4.3
Total other expenses	$ 15.3	$ 15.3	$ 32.2	$ 34.7

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Effective income tax rate	26%	27%

Regulatory Capital Requiremen_3

Regulatory Capital Requirements (Details) $ in Millions	Mar. 31, 2024 USD ($)
Capital and Other Regulatory Requirements [Abstract]
Adjusted net capital	$ 10
StoneX Financial Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual	351.2
Minimum Requirement	257.2
StoneX Financial Ltd.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual	455.5
Minimum Requirement	358
Gain Capital Group, LLC
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual	50.6
Minimum Requirement	29.9
StoneX Financial Pte. Ltd.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual	91.3
Minimum Requirement	25.8
StoneX Markets LLC
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual	219.2
Minimum Requirement	$ 125.9

Segment Analysis - Narrative (D

Segment Analysis - Narrative (Details)	6 Months Ended
	Mar. 31, 2024 employee country market currency
Segment Reporting Information [Line Items]
Number of employees | employee	4,300
Number of countries in which entity operates (more than)	180
Number of global financial markets (more than) | market	18,000
Payments
Segment Reporting Information [Line Items]
Number of countries in which entity operates (more than)	180
Number of different types of foreign currencies (more than) | currency	140

Segment Analysis - Segment Repo

Segment Analysis - Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 22,106.1	$ 16,161	$ 41,679.1	$ 29,172.6
Operating revenues:	818.2	704.4	1,602.4	1,359.2
Net operating revenues (loss):	422.3	399.4	843.9	781.4
Net contribution:	329	316.7	665.8	608.3
Segment income:	204.7	179.4	420.8	352.3
Net operating revenue (loss) with Corporate	(12.8)	(21.8)	(28.4)	(32.9)
Overhead costs and expenses	(119.6)	(100.1)	(224.4)	(189.8)
Gain on acquisition	0	0	0	23.5
Income before tax	72.3	57.5	168	153.1
Assets	25,651		25,651		$ 21,938.7
Corporate
Segment Reporting Information [Line Items]
Total revenues	14.4	2.5	23.6	15.3
Operating revenues:	14.4	2.5	23.6	15.3
Net operating revenues (loss):	(12.8)	(21.8)	(28.4)	(32.9)
Assets	1,267.2		1,267.2		812.3
Eliminations
Segment Reporting Information [Line Items]
Total revenues	(11.4)	(9.1)	(23.6)	(18.9)
Operating revenues:	(11.4)	(9.1)	(23.6)	(18.9)
Commercial
Segment Reporting Information [Line Items]
Net contribution:	119.3	140.9	245.7	256.6
Segment income:	85.6	102.9	172.8	185.7
Commercial | Operating Segments
Segment Reporting Information [Line Items]
Total revenues	21,479.1	15,450.7	40,457.1	27,744.2
Operating revenues:	200.5	220.1	398.9	402.5
Net operating revenues (loss):	164.2	185.1	327.6	337.8
Assets	5,154.8		5,154.8		4,676.3
Institutional
Segment Reporting Information [Line Items]
Net contribution:	102.5	89.3	202.7	183.9
Segment income:	61.3	55.8	126.5	117.8
Institutional | Operating Segments
Segment Reporting Information [Line Items]
Total revenues	463.4	362.5	899.1	706
Operating revenues:	463.4	362.5	899.1	706
Net operating revenues (loss):	149.8	137.9	298.4	281.1
Assets	17,684.1		17,684.1		15,059.3
Retail
Segment Reporting Information [Line Items]
Net contribution:	69.9	48.4	132.5	87.6
Segment income:	33.2	4.8	61.9	0.6
Retail | Operating Segments
Segment Reporting Information [Line Items]
Total revenues	111.3	304.6	213	620.8
Operating revenues:	102	78.6	194.5	149.1
Net operating revenues (loss):	74.3	50.8	141.3	94.7
Assets	1,111.8		1,111.8		1,014.2
Payments
Segment Reporting Information [Line Items]
Net contribution:	37.3	38.1	84.9	80.2
Segment income:	24.6	15.9	59.6	48.2
Payments | Operating Segments
Segment Reporting Information [Line Items]
Total revenues	49.3	49.8	109.9	105.2
Operating revenues:	49.3	49.8	109.9	105.2
Net operating revenues (loss):	46.8	$ 47.4	105	$ 100.7
Assets	$ 433.1		$ 433.1		$ 376.6