Goodwill and Intangible Assets - Schedule of Changes to Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Beginning balance	$ 8,342	$ 10,010
Translation adjustment	781	(1,668)
Ending balance	$ 9,123	$ 8,342