Consolidated Sponsored Investment Products - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014 Funds	Dec. 31, 2013 Funds	Sep. 30, 2013
Investments [Abstract]
Number of consolidated sponsored investment products	12	8
Number of additional consolidated sponsored investment product	5
Number of deconsolidated sponsored investment product	1
Fair value, equity, Level 1 to Level 2 transfers, amount	$ 0		$ 0
Fair value, equity, Level 2 to Level 1 transfers, amount			$ 5,200,000