Segment Analysis (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2013
Segment Reporting Information [Line Items]
Revenues	$ 7,005.1	$ 9,659.1	$ 23,366.7	$ 33,565.9
Operating revenues	118.2	123.0	360.3	356.3
Net operating revenues	76.0	81.3	235.3	239.7
Net Contribution	58.7	60.5	181.8	174.5
Net Segment Income	29.5	31.5	95.4	86.8
Costs not allocated	25.5	24.4	77.2	64.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	4.0	7.1	18.2	22.8
Assets	3,184.1		3,184.1		2,848.0
Commercial Hedging [Member]
Segment Reporting Information [Line Items]
Revenues	54.9	54.0	164.3	155.2
Operating revenues	54.9	54.0	164.3	155.2
Net operating revenues	44.1	43.9	132.9	126.3
Net Contribution	32.2	31.4	97.3	92.4
Net Segment Income	16.6	16.1	51.3	45.5
Assets	1,444.3		1,444.3		1,005.1
Global Payments [Member]
Segment Reporting Information [Line Items]
Revenues	13.6	11.2	40.0	30.6
Operating revenues	13.6	11.2	40.0	30.6
Net operating revenues	11.9	9.9	34.7	27.2
Net Contribution	9.3	7.6	27.1	20.7
Net Segment Income	7.0	5.4	20.3	15.0
Assets	35.1		35.1		57.2
Securities Segment [Member]
Segment Reporting Information [Line Items]
Revenues	20.0	16.0	58.6	48.7
Operating revenues	20.0	16.0	58.6	48.7
Net operating revenues	12.8	10.6	40.2	34.6
Net Contribution	9.7	8.1	30.5	27.0
Net Segment Income	4.9	3.2	15.9	12.8
Assets	247.8		247.8		204.2
Physical Commodities [Member]
Segment Reporting Information [Line Items]
Revenues	6,890.5	9,544.5	23,020.3	33,231.8
Operating revenues	3.6	8.4	13.9	22.2
Net operating revenues	3.0	7.5	11.7	19.2
Net Contribution	2.0	5.5	9.2	14.3
Net Segment Income	0.1	3.5	3.6	8.5
Assets	182.0		182.0		132.5
Clearing and Execution Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	27.1	34.1	85.5	92.1
Operating revenues	27.1	34.1	85.5	92.1
Net operating revenues	6.5	10.5	22.0	26.0
Net Contribution	5.5	7.9	17.7	20.1
Net Segment Income	0.9	3.3	4.3	5.0
Assets	1,166.8		1,166.8		1,333.3
Corporate [Member]
Segment Reporting Information [Line Items]
Revenues	(1.0)	(0.7)	(2.0)	7.5
Operating revenues	(1.0)	(0.7)	(2.0)	7.5
Net operating revenues	(2.3)	(1.1)	(6.2)	6.4
Assets	$ 108.1		$ 108.1		$ 115.7