Intangible Assets, Net - Summary of Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Definite-lived intangible assets:
Investment contracts	$ 158,747	$ 158,747
Accumulated amortization	(151,891)	(149,380)
Definite-lived intangible assets, net	6,856	9,367
Indefinite-lived intangible assets	34,816	32,416
Total intangible assets, net	$ 41,672	$ 41,783	$ 42,710	$ 44,633