Condensed Consolidated Income Statements - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Revenues:
Revenues	$ 16,161.0	$ 16,382.7	$ 29,172.6	$ 30,724.1
Cost of sales of physical commodities	15,456.6	15,838.0	27,813.4	29,728.9
Operating revenues	704.4	544.7	1,359.2	995.2
Transaction-based clearing expenses	69.2	76.5	136.5	147.4
Introducing broker commissions	42.2	43.2	79.0	81.5
Interest expense	178.7	14.1	333.0	29.8
Interest expense on corporate funding	14.9	10.6	29.3	22.4
Net operating revenues	399.4	400.3	781.4	714.1
Compensation and other expenses:
Compensation and benefits	232.5	207.1	431.5	382.1
Trading systems and market information	17.8	16.9	35.5	33.0
Professional fees	11.3	13.8	27.2	25.7
Non-trading technology and support	16.2	12.8	31.0	25.8
Occupancy and equipment rental	10.6	8.8	19.5	17.5
Selling and marketing	14.2	14.3	27.1	25.3
Travel and business development	5.8	3.0	11.5	5.9
Communications	2.1	2.1	4.3	4.0
Depreciation and amortization	13.1	11.3	25.8	20.4
Bad debts, net of recoveries	3.0	12.3	3.7	12.1
Other	15.3	16.9	34.7	28.8
Total compensation and other expenses	341.9	319.3	651.8	580.6
Gain on acquisition and other gain	0.0	6.4	23.5	6.4
Income before tax	57.5	87.4	153.1	139.9
Income tax expense	15.8	23.4	34.8	34.2
Net income	$ 41.7	$ 64.0	$ 118.3	$ 105.7
Earnings per share:
Basic (in dollar per shares)	$ 2.02	$ 3.18	$ 5.77	$ 5.27
Diluted (in dollar per shares)	$ 1.95	$ 3.11	$ 5.57	$ 5.15
Weighted-average number of common shares outstanding:
Basic (in shares)	19,930,027	19,573,871	19,850,052	19,477,540
Diluted (in shares)	20,621,194	20,012,709	20,553,913	19,930,047
Sales of physical commodities
Revenues:
Revenues	$ 15,506.2	$ 15,864.2	$ 27,909.6	$ 29,783.1
Principal gains, net
Revenues:
Revenues	256.6	323.5	510.8	574.6
Commission and clearing fees
Revenues:
Revenues	130.7	138.4	248.7	254.7
Consulting, management, and account fees
Revenues:
Revenues	40.7	25.4	80.5	49.5
Interest income
Revenues:
Revenues	$ 226.8	$ 31.2	$ 423.0	$ 62.2