Accounts Receivable - Schedule of Changes in Sales Return Reserve (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Beginning balance	$ (1,107)	$ (1,481)	$ (787)
Provision	(40)	(26)	(1,586)
Usage	626	361	851
Translation adjustments	(107)	39	41
Ending balance	$ (628)	$ (1,107)	$ (1,481)