Concentration of Credit Risk (Details) (Customer Concentration Risk [Member], USD $)	9 Months Ended
	Sep. 30, 2012
Foreign retail funds [Member]
Concentration Risk [Line Items]
Entity-Wide Revenue, Major Customer, Amount	$ 40,375,000
Concentration Risk, Percentage	20.00%
Investment Advisory and Administration Fees [Member]
Concentration Risk [Line Items]
Entity-Wide Revenue, Major Customer, Amount	31,319,000
Portfolio Consulting and Other Revenue [Member]
Concentration Risk [Line Items]
Entity-Wide Revenue, Major Customer, Amount	$ 9,056,000