Income Taxes - Components of the Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 64	$ 0	$ 0
State	(92)	61	80
Foreign	440	165	136
Total	412	226	216
Deferred:
Federal	(3,222)	(26,386)	(15,488)
State	5,799	(4,165)	(2,948)
Foreign	(874)	(848)	(529)
Total	1,703	(31,399)	(18,965)
Change in valuation allowance	(2,030)	30,908	18,695
Total	$ 85	$ (265)	$ (54)