Income Taxes - Summary of Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
State	$ 49	$ 63	$ 71
Foreign	256	209	85
Total current	305	272	156
Deferred
Federal			(1,312)
State			(99)
Foreign	(47)	(36)	(8)
Total deferred	(47)	(36)	(1,419)
Total income tax provision (benefit)	$ 258	$ 236	$ (1,263)