Investments - Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 25,937	$ 13,670
Unrealized Loss	(849)	(726)
Unrealized Gain	3,880	2,104
Fair Value	28,968	15,048
Sponsored Mutual Funds and Variable Insurance Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	16,079	7,312
Unrealized Loss	(704)	(689)
Unrealized Gain	2,529	1,390
Fair Value	17,904	8,013
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	7,043	3,739
Unrealized Loss
Unrealized Gain	1,336	640
Fair Value	8,379	4,379
Sponsored Closed-End Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	2,815	2,619
Unrealized Loss	(145)	(37)
Unrealized Gain	15	74
Fair Value	$ 2,685	$ 2,656