Non-Marketable Investments - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Carrying value of the Company's non-marketable investments	$ 2,500,000	$ 2,500,000		$ 3,600,000
Book value of investment	400,000	400,000		$ 400,000
Losses from non-marketable investments	$ 1,100,000	1,200,000
Distributions received from funds		$ 0	$ 100,000
Limited Partnerships Investments [Member] | Minimum [Member]
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items]
Ownership interest of Company		5.00%