Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Sep. 30, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

The Company has set forth certain quarterly unaudited financial data for the past two years in the tables below:

	For the 2016 Fiscal Quarter Ended
(in millions, except per share amounts)	September 30		June 30		March 31		December 31
Total revenues	$	2,777.6	$	4,868.5	$	3,708.9	$	3,399.9
Cost of sales of physical commodities	2,599.0		4,693.5		3,542.8		3,248.6
Operating revenues	178.6		175.0		166.1		151.3
Transaction-based clearing expenses	32.0		35.2		32.9		29.8
Introducing broker commissions	28.1		14.8		13.2		12.8
Interest expense	7.5		7.7		7.1		6.0
Net operating revenues	111.0		117.3		112.9		102.7
Compensation and other expenses	98.0		95.9		92.9		90.6
Gain on acquisition	6.2		—		—		—
Income before tax	19.2		21.4		20.0		12.1
Income tax expense	2.4		6.8		5.5		3.3
Net income	$	16.8	$	14.6	$	14.5	$	8.8
Net basic earnings per share	$	0.91	$	0.79	$	0.77	$	0.47
Net diluted earnings per share	$	0.90	$	0.78	$	0.76	$	0.46

	For the 2015 Fiscal Quarter Ended
(in millions, except per share amounts)	September 30		June 30		March 31		December 31
Total revenues	$	2,628.4	$	3,995.1	$	14,442.0	$	13,627.7
Cost of sales of physical commodities	2,449.7		3,843.5		14,285.5		13,490.2
Operating revenues	178.7		151.6		156.5		137.5
Transaction-based clearing expenses	31.3		30.2		31.8		29.4
Introducing broker commissions	15.1		13.1		12.3		12.2
Interest expense	5.0		4.9		4.5		2.7
Net operating revenues	127.3		103.4		107.9		93.2
Compensation and other expenses	98.1		86.2		89.8		79.6
Income before tax	29.2		17.2		18.1		13.6
Income tax expense	8.1		5.0		5.1		4.2
Net income	$	21.1	$	12.2	$	13.0	$	9.4
Net basic earnings per share	$	1.12	$	0.64	$	0.68	$	0.50
Net diluted earnings per share	$	1.09	$	0.62	$	0.67	$	0.49