Consolidated Income Statements - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Sales of physical commodities	$ 52,899.2	$ 31,830.3	$ 26,682.4
Principal gains, net	622.2	415.8	354.1
Revenue from contract with customer	487.3	452.0	462.9
Interest income	130.9	198.9	123.3
Total revenues	54,139.6	32,897.0	27,622.7
Cost of sales of physical commodities	52,831.3	31,790.9	26,646.9
Operating revenues	1,308.3	1,106.1	975.8
Transaction-based clearing expenses	222.5	183.5	179.7
Introducing broker commissions	113.8	114.7	133.8
Interest expense	80.4	142.0	70.5
Interest expense on corporate funding	23.6	12.7	10.2
Net operating revenues	868.0	653.2	581.6
Compensation and other expenses:
Compensation and benefits	518.7	393.1	337.7
Trading systems and market information	46.3	38.8	34.7
Professional fees	30.2	21.0	18.1
Non-trading technology and support	28.4	20.1	13.9
Occupancy and equipment rental	23.5	19.4	16.5
Selling and marketing	12.2	5.2	6.2
Travel and business development	8.9	16.2	13.8
Communications	7.0	6.6	5.4
Depreciation and amortization	19.7	14.0	11.6
Bad debts, net of recoveries and impairment	18.7	2.5	3.1
(Recovery) bad debt on physical coal	0.0	(12.4)	1.0
Other	29.6	23.2	20.1
Total compensation and other expenses	743.2	547.7	482.1
Gain on acquisitions and other gains	81.9	5.5	2.0
Income before tax	206.7	111.0	101.5
Income tax expense	37.1	25.9	46.0
Net income (loss)	$ 169.6	$ 85.1	$ 55.5
Earnings per share:
Basic (in dollar per share)	$ 8.78	$ 4.46	$ 2.93
Diluted (in dollar per share)	$ 8.61	$ 4.39	$ 2.87
Weighted-average number of common shares outstanding:
Basic (in shares)	18,824,328	18,738,905	18,549,011
Diluted (in shares)	19,180,479	19,014,395	18,934,830
Commission and Clearing Fees [Member]
Revenues:
Revenue from contract with customer	$ 403.6	$ 372.4	$ 391.8
Consulting, Management, and Account Fees [Member]
Revenues:
Revenue from contract with customer	$ 83.7	$ 79.6	$ 71.1