Non-Marketable Investments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Carrying value of the Company's non-marketable investments	$ 4,300,000		$ 5,700,000
Gain (loss) from non-marketable investments	42,000	(200,000)
Book value of investment	900,000		900,000
Gross distributions received from funds		100,000
Gross distributions received from cost and equity method investment	$ 1,400,000
Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Ownership interest of company	5.00%