Acquisitions (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended				1 Months Ended	0 Months Ended											1 Months Ended	3 Months Ended	12 Months Ended	13 Months Ended	1 Months Ended												1 Months Ended
	Nov. 30, 2011	Sep. 30, 2012 business	Sep. 30, 2011 business	Sep. 30, 2010 business	Apr. 30, 2010 payment	Nov. 30, 2011 Coffee Network Acquisition [Member] payment	Nov. 25, 2011 MF Metals Team Acquisition [Member] professional	Apr. 30, 2012 TRX Futures Acquisition [Member]	Apr. 30, 2010 TRX Futures Acquisition [Member]	Feb. 29, 2012 DTVM Acquisition [Member]	Oct. 31, 2010 Hencorp Acquisition [Member] payment	Apr. 30, 2011 Hudson Capital Asset Acquisition [Member]	Aug. 31, 2011 Arabian Commodities Limited [Member]	Apr. 30, 2010 RMI-RMC Acquistion [Member]	Sep. 30, 2011 Hanley Group Acquisition [Member]	Sep. 30, 2010 Hanley Group Acquisition [Member]	Jul. 31, 2010 Hanley Group Acquisition [Member] payment	Sep. 30, 2010 Provident Group Asset Acquisition [Member]	Dec. 31, 2010 Provident Group Asset Acquisition [Member]	Sep. 30, 2011 Provident Group Asset Acquisition [Member]	Sep. 30, 2011 Provident Group Asset Acquisition [Member]	Oct. 31, 2010 Customer Relationships [Member] Hencorp Acquisition [Member]	Apr. 30, 2010 Customer Relationships [Member] RMI-RMC Acquistion [Member]	Jul. 31, 2010 Customer Relationships [Member] Hanley Group Acquisition [Member]	Sep. 30, 2010 Customer Relationships [Member] Provident Group Asset Acquisition [Member]	Apr. 30, 2010 Software Programs and Platforms [Member] RMI-RMC Acquistion [Member]	Jul. 31, 2010 Software Programs and Platforms [Member] Hanley Group Acquisition [Member]	Oct. 31, 2010 Noncompete Agreements [Member] Hencorp Acquisition [Member]	Jul. 31, 2010 Noncompete Agreements [Member] Hanley Group Acquisition [Member]	Oct. 31, 2010 Trade Names [Member] Hencorp Acquisition [Member]	Apr. 30, 2010 Trade Names [Member] Hencorp Acquisition [Member]	Jul. 31, 2010 Trade Names [Member] Hanley Group Acquisition [Member]	Sep. 30, 2010 Trade Names [Member] Provident Group Asset Acquisition [Member]	Jul. 31, 2010 Restricted Stock [Member] Hanley Group Acquisition [Member]
Business Acquisition [Line Items]
Business Acquisition, Contingent Consideration, Potential Cash Payment											$ 0.3
Number of Businesses Acquired		3	2	3
Goodwill, Expected Tax Deductible Amount		0.7	4.9	39.8
Business Acquisition, Percentage of Voting Interests Acquired						100.00%		100.00%		100.00%
Business Acquisition, Cost of Acquired Entity, Cash Paid, Payment 1				6.0		0.2					2.3					7.5
Business Combination, Contingent Consideration Arrangements, Number of Annual Payments					2	3					3						2
Business Combination, Consideration Transferred						0.3		12.9		1.5		1.0	7.1					5.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Amortizable Intangibles						0.2	0.5				1.7											1.3	7.0	0.2	0.2	0.8	1.2	0.4	2.9
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						2 years	3 years															20 years	20 years	5 years	2 years	5 years	5 years	2 years	3 years
Acquisition Measurement Period During Which Valuations Are Finalized	1 year							1 year
Business Combination, Professionals Hired From Acquiree Company							50
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangibles							1.0
Goodwill		43.6	42.5					0.3		0.8	2.1			7.7			18.7
Business Combination, Cost of Acquired Entity, Number of Payments											2						2
Business Acquisition, Cost of Acquired Entity, Total of Payments 2 and 3											1.4						24.3
Business Combination, Consideration, Including Contingent Consideration									15.2		6.4						51.6
Business Acquisition, Cost of Acquired Entity, Cash Paid, Payment 4											0.3				6.3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangibles Not Amortizable																														0.8	1.2	0.1	0.2
Business Acquisition, Cost of Acquired Entity, Cash Paid, Payment 2			3.1												18.2
Business Acquisition, Cost of Acquired Entity, Cash Paid, Payment 3																6.1
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Maximum Percent of Final Contingent Payment to be Paid in Stock																																		30.00%
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Option, Exercise Period, Number of Days Commencing on June 30, 2013																																		20 days
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Option, Price Per Share																																		$ 16
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Option, Price Per Share, Percent of Fair Value of Common Stock on June 20, 2013																																		75.00%
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Option, Maximum Number of Shares Issuable Upon Exercise																																		187,500
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Option, Stock Restriction Lapse Period																																		3 years
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Total Shares Purchased and Placed In Escrow																		8,700		205,625	214,325
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Period From Date of Closing Over Which Shares Will be Released from Escrow																		5 years
Business Combination, Cost of Acquired Entity, Equity Interest Issued or Issuable, Shares Released from Escrow		3,255
Business Combination, Bargain Purchase, Gain Recognized, Amount																			$ 0.4