Investments - Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Marketable Securities [Abstract]
Cost	$ 48,755	$ 25,937
Unrealized Loss	(769)	(849)
Unrealized Gain	2,859	3,880
Fair Value	50,845	28,968
Sponsored Funds [Member]
Marketable Securities [Abstract]
Cost	37,426	16,079
Unrealized Loss	(633)	(704)
Unrealized Gain	2,036	2,529
Fair Value	38,829	17,904
Cost	3,074	2,815
Unrealized Loss	(136)	(145)
Unrealized Gain	151	15
Fair Value	3,089	2,685
Equity Securities [Member]
Marketable Securities [Abstract]
Cost	8,255	7,043
Unrealized Loss	0
Unrealized Gain	672	1,336
Fair Value	$ 8,927	$ 8,379