Other Income - Schedule of Other Income Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Change in fair value of derivative liability		$ 81	$ (52)
Foreign exchange losses	$ (19)	(13)	(476)
Interest income	998	619	108
Miscellaneous expenses	(39)	(43)	(100)
Other income (expenses)	$ 940	$ 644	$ (520)