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	$ 16,161.0	$ 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	42.0	42.2	81.1	79.0
Interest expense	259.2	178.7	495.2	333.0
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	35.0	27.2
Non-trading technology and support	18.0	16.2	34.9	31.0
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	(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	0.0	6.9	23.5
Income before tax	72.3	57.5	168.0	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	$ 326.0	$ 226.8	$ 616.1	$ 423.0