Income Taxes - Reconciliation of Provision for Income Taxes at Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory tax rate	$ (23,496)	$ (16,388)	$ (19,718)
Tax benefit at state statutory tax rate	(1,008)	(499)	(1,169)
Foreign tax rate differential	57	(826)	(526)
Unbenefitted loss of consolidated investment	0	0	2,366
Change in valuation allowance	17,701	9,738	12,407
Meals and entertainment	222	44	34
Stock compensation	7,857	8,492	7,160
Nondeductible expenses and other	(161)	121	627
Provision for income taxes	$ 1,172	$ 682	$ 1,181