Condensed Consolidated Income Statements - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Sales of physical commodities	$ 20,016,900,000	$ 6,929,500,000	$ 30,994,900,000	$ 13,225,300,000
Principal gains, net	168,500,000	110,300,000	281,000,000	203,100,000
Commission and clearing fees	116,600,000	85,100,000	203,800,000	184,600,000
Consulting, management, and account fees	22,600,000	19,100,000	43,900,000	38,200,000
Interest income	41,700,000	48,200,000	87,700,000	93,200,000
Total revenues	20,366,300,000	7,192,200,000	31,611,300,000	13,744,400,000
Cost of sales of physical commodities	19,999,500,000	6,921,100,000	30,967,700,000	13,208,600,000
Operating revenues	366,800,000	271,100,000	643,600,000	535,800,000
Transaction-based clearing expenses	63,800,000	42,700,000	110,100,000	92,800,000
Introducing broker commissions	29,600,000	24,800,000	55,800,000	57,400,000
Interest expense	30,000,000	38,400,000	63,800,000	71,400,000
Net operating revenues	243,400,000	165,200,000	413,900,000	314,200,000
Compensation and other expenses:
Compensation and benefits	136,700,000	97,900,000	240,700,000	187,000,000
Trading systems and market information	11,200,000	9,500,000	21,600,000	18,700,000
Occupancy and equipment rental	4,900,000	5,000,000	9,900,000	9,400,000
Professional fees	4,700,000	5,000,000	10,700,000	10,300,000
Travel and business development	3,200,000	4,000,000	7,700,000	7,800,000
Non-trading technology and support	5,900,000	5,000,000	11,900,000	9,200,000
Depreciation and amortization	4,200,000	3,200,000	8,100,000	6,100,000
Communications	1,500,000	2,000,000	3,100,000	3,300,000
Bad debts	4,400,000	700,000	4,400,000	1,000,000
Recovery of bad debt on physical coal	0	0	0.0	(2,400,000.0)
Other	10,600,000	7,400,000	18,100,000	13,900,000
Total compensation and other expenses	187,300,000	139,700,000	336,200,000	264,300,000
Other gain	0	5,400,000	100,000	5,400,000
Income before tax	56,100,000	30,900,000	77,800,000	55,300,000
Income tax expense	16,800,000	7,500,000	22,200,000	13,700,000
Net income	$ 39,300,000	$ 23,400,000	$ 55,600,000	$ 41,600,000
Earnings per share:
Basic	$ 2.03	$ 1.23	$ 2.88	$ 2.19
Diluted	$ 2.00	$ 1.21	$ 2.84	$ 2.15
Weighted-average number of common shares outstanding:
Basic	18,872,937	18,753,490	18,811,268	18,706,104
Diluted	19,189,953	19,004,793	19,132,497	18,999,889