Commitments and Contingencies (Details) (USD $)	9 Months Ended		3 Months Ended		3 Months Ended				3 Months Ended				3 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010 Sun Trust Acquisition [Member] years	Sep. 30, 2011 Sun Trust Acquisition [Member]	Dec. 31, 2008 Prudent Bear Acquisition [Member] years	Sep. 30, 2011 Prudent Bear Acquisition [Member]	Mar. 31, 2011 Prudent Bear Acquisition [Member]	Mar. 31, 2010 Prudent Bear Acquisition [Member]	Dec. 31, 2008 Clover Capital Acquisition [Member] years	Sep. 30, 2011 Clover Capital Acquisition [Member]	Dec. 31, 2010 Clover Capital Acquisition [Member]	Dec. 31, 2009 Clover Capital Acquisition [Member]	Sep. 30, 2007 Rochdale Acquisition [Member] years	Sep. 30, 2011 Rochdale Acquisition [Member]	Dec. 31, 2010 Rochdale Acquisition [Member]
Business Acquisition Contingent Consideration Payable Period			5		4				5				5
Fair value of future consideration payments liability				$ 18,400,000
Fair value of future consideration payments liability, current		5,300,000		5,000,000
Fair value of future consideration payments liability, noncurrent				13,400,000
Estimated remaining contingent purchase price payments				25,000,000		49,000,000				56,000,000				20,000,000
Accrued contingent purchase price payment						0				0	0	0		700,000
Contingent purchase price payments							44,700,000	5,100,000						3,600,000	1,100,000
Maximum bonus payable over remaining terms	68,000,000
Bonus payable related to the Fund Bonus	500,000
Operating Leases, Future Minimum Payments Due, Current	2,000,000
Operating Leases Future Minimum Payments Due In Two Years Through Five Years	6,000,000
Operating Leases, Future Minimum Payments, Due Thereafter	$ 38,000,000