Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012 funds	Dec. 31, 2011	Dec. 31, 2012 Assets acquired under capital leases - equipment	Dec. 31, 2012 Minimum	Dec. 31, 2012 Minimum Telephone and computer equipment	Dec. 31, 2012 Minimum Computer software	Dec. 31, 2012 Minimum Furniture and fixtures	Dec. 31, 2012 Minimum Leasehold improvements	Dec. 31, 2012 Maximum	Dec. 31, 2012 Maximum Telephone and computer equipment	Dec. 31, 2012 Maximum Computer software	Dec. 31, 2012 Maximum Furniture and fixtures	Dec. 31, 2012 Maximum Leasehold improvements	Dec. 31, 2012 Investment Company [Member] funds
Organization [Line Items]
Number of funds, Consolidated	8													3
Deferred rent	$ 13.8	$ 15.3
Useful life			5 years		3 years	3 years	3 years	1 year		5 years	5 years	8 years	11 years
Redemption fee, percent				1.00%					5.00%