Condensed Consolidated Income Statements - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Sales of physical commodities	$ 10,804.3	$ 20,016.9	$ 19,687.8	$ 30,994.9
Principal gains, net	265.2	168.5	468.6	281.0
Commission and clearing fees	129.8	116.6	249.2	203.8
Consulting, management, and account fees	22.1	22.6	45.1	43.9
Interest income	23.4	41.7	44.6	87.7
Total revenues	11,244.8	20,366.3	20,495.3	31,611.3
Cost of sales of physical commodities	10,773.4	19,999.5	19,643.8	30,967.7
Operating revenues	471.4	366.8	851.5	643.6
Transaction-based clearing expenses	74.8	63.8	140.2	110.1
Introducing broker commissions	40.8	29.6	79.0	55.8
Interest expense	11.1	27.8	21.0	58.9
Interest expense on corporate funding	10.5	2.2	21.0	4.9
Net operating revenues	334.2	243.4	590.3	413.9
Compensation and other expenses:
Compensation and benefits	185.0	136.7	338.6	240.7
Trading systems and market information	14.8	11.2	28.5	21.6
Professional fees	9.0	4.7	18.3	10.7
Non-trading technology and support	10.6	5.9	21.5	11.9
Occupancy and equipment rental	7.5	4.9	16.1	9.9
Selling and marketing	6.5	4.2	15.3	5.6
Travel and business development	0.5	3.2	1.5	7.7
Communications	2.4	1.5	4.7	3.1
Depreciation and amortization	8.6	4.2	17.0	8.1
Bad debts	0.9	4.4	2.4	4.4
Other	12.1	6.4	23.2	12.5
Total compensation and other expenses	257.9	187.3	487.1	336.2
Other gain	0.0	0.0	0.0	0.1
Income before tax	76.3	56.1	103.2	77.8
Income tax expense	21.0	16.8	28.4	22.2
Net income	$ 55.3	$ 39.3	$ 74.8	$ 55.6
Earnings per share:
Basic (in dollar per shares)	$ 2.81	$ 2.03	$ 3.81	$ 2.88
Diluted (in dollar per shares)	$ 2.73	$ 2.00	$ 3.71	$ 2.84
Weighted-average number of common shares outstanding:
Basic (in shares)	19,112,216	18,872,937	19,025,604	18,811,268
Diluted (in shares)	19,670,539	19,189,953	19,570,028	19,132,497