Intangible Assets, Net - Summary of Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Definite-lived intangible assets:
Investment contracts	$ 158,747	$ 158,747
Accumulated amortization	(154,533)	(152,676)
Definite-lived intangible assets, net	4,214	6,071
Indefinite-lived intangible assets	34,816	34,816
Total intangible assets, net	$ 39,030	$ 40,887	$ 41,672	$ 41,783