Income Taxes - Schedule of Income (Loss) before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ (7,132)	$ (15,145)	$ (2,651)
Foreign	(75)	(427)	117
Loss before provision for income taxes	$ (7,207)	$ (15,572)	$ (2,534)