Consolidated Income Statements	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares
Revenues:
Sales of physical commodities	$ 31,830,300,000	$ 26,682,400,000	$ 28,673,300,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,451,300,000	2,287,600,000	2,659,800,000
Principal gains, net	415,800,000	354,100,000	297,000,000
Commission and clearing fees	372,400,000	391,800,000	318,600,000
Consulting, management, and account fees	79,600,000	71,100,000	65,000,000
Interest income	198,900,000	123,300,000	69,700,000
Total revenues	32,897,000,000	27,622,700,000	29,423,600,000
Cost of sales of physical commodities	31,790,900,000	26,646,900,000	28,639,600,000
Operating revenues	1,106,100,000	975,800,000	784,000,000
Transaction-based clearing expenses	183,500,000	179,700,000	136,300,000
Introducing broker commissions	114,700,000	133,800,000	113,000,000
Interest expense	154,700,000	80,700,000	42,100,000
Net operating revenues	653,200,000	581,600,000	492,600,000
Compensation and other expenses:
Compensation and benefits	393,100,000	337,700,000	295,700,000
Trade systems and market information	38,800,000	34,700,000	34,400,000
Occupancy and equipment rental	19,400,000	16,500,000	15,200,000
Professional fees	21,000,000	18,100,000	15,200,000
Travel and business development	16,200,000	13,800,000	13,300,000
Non-trading technology and support	20,100,000	13,900,000	11,600,000
Depreciation and amortization	14,000,000	11,600,000	9,800,000
Communications	6,600,000	5,400,000	5,000,000
Bad debts	2,500,000	3,100,000	4,300,000
(Recovery) bad debt on physical coal	(12,400,000.0)	1,000,000.0	47,000,000.0
Other	28,400,000	26,300,000	25,900,000
Total compensation and other expenses	547,700,000	482,100,000	477,400,000
Other gains	5,500,000	2,000,000	0
Income from operations, before tax	111,000,000	101,500,000	15,200,000
Income tax expense	25,900,000	46,000,000	8,800,000
Net Income	$ 85,100,000	$ 55,500,000	$ 6,400,000
Earnings per share:
Basic | $ / shares	$ 4.46	$ 2.93	$ 0.32
Diluted | $ / shares	$ 4.39	$ 2.87	$ 0.31
Weighted-average number of common shares outstanding:
Basic | shares	18,738,905	18,549,011	18,395,987
Diluted | shares	19,014,395	18,934,830	18,687,354