Condensed Consolidated Income Statements - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Sales of physical commodities	$ 6,929,500,000	$ 6,255,800,000	$ 13,225,300,000	$ 13,970,200,000
Principal gains, net	110,300,000	98,500,000	203,100,000	175,600,000
Commission and clearing fees	85,100,000	106,400,000	184,600,000	192,900,000
Consulting,management, and account fees	19,100,000.0	18,400,000.0	38,200,000.0	35,000,000.0
Interest income	48,200,000	27,900,000	93,200,000	51,900,000
Total revenues	7,192,200,000	6,507,000,000	13,744,400,000	14,425,600,000
Cost of sales of physical commodities	6,921,100,000	6,246,800,000	13,208,600,000	13,952,800,000
Operating revenues	271,100,000	260,200,000	535,800,000	472,800,000
Transaction-based clearing expenses	42,700,000	50,700,000	92,800,000	87,600,000
Introducing broker commissions	24,800,000	36,200,000	57,400,000	67,300,000
Interest expense	38,400,000	19,000,000	71,400,000	33,300,000
Net operating revenues	165,200,000	154,300,000	314,200,000	284,600,000
Compensation and other expenses:
Compensation and benefits	97,900,000	88,200,000	187,000,000	165,400,000
Trading systems and market information	9,500,000	8,900,000	18,700,000	17,100,000
Occupancy and equipment rental	5,000,000	4,200,000	9,400,000	8,300,000
Professional fees	5,000,000	3,900,000	10,300,000	8,600,000
Travel and business development	4,000,000	3,000,000	7,800,000	6,500,000
Non-trading technology and support	5,000,000	3,400,000	9,200,000	6,500,000
Depreciation and amortization	3,200,000	2,900,000	6,100,000	5,600,000
Communications	2,000,000	1,400,000	3,300,000	2,800,000
Provision for Doubtful Accounts	700,000	200,000	1,000,000	300,000
(Recovery) bad debt on physical coal	0	0	(2,400,000.0)	1,000,000.0
Other	7,400,000	8,700,000	13,900,000	14,400,000
Total compensation and other expenses	139,700,000	124,800,000	264,300,000	236,500,000
Other gain	5,400,000	0	5,400,000	0
Income before tax	30,900,000	29,500,000	55,300,000	48,100,000
Income tax expense	7,500,000	6,800,000	13,700,000	32,300,000
Net income	$ 23,400,000	$ 22,700,000	$ 41,600,000	$ 15,800,000
Earnings per share:
Basic	$ 1.23	$ 1.20	$ 2.19	$ 0.83
Diluted	$ 1.21	$ 1.18	$ 2.15	$ 0.81
Weighted-average number of common shares outstanding:
Basic	18,753,490	18,559,849	18,706,104	18,502,795
Diluted	19,004,793	18,859,333	18,999,889	18,836,213