Commitments and Contingencies - Contigent Consideration for Acquisitions (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
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	$ 8.0		$ 8.0		$ 9.6
Change in fair value of contingent consideration for acquisitions	(0.2)	0.8	0.6	4.7
Forward Insight Commodities Acquisition [Member]
Business Acquisition, Contingent Consideration [Line Items]
Present Value of Estimated Total Purchase Price	0.5		0.5
Tradewire Acquisition [Member] [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	4.8		4.8
Present Value of Estimated Total Purchase Price	6.3		6.3
Coffee Network Acquisition [Member]
Business Acquisition, Contingent Consideration [Line Items]
Present Value of Estimated Total Purchase Price	0.1		0.1
Hencorp Acquisition [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	2.6		2.6
Present Value of Estimated Total Purchase Price	7.5		7.5
Contingent Consideration [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	(0.2)	0.8	0.1	1.6
Change in fair value of contingent consideration for acquisitions			$ 0.1	$ 1.6