Other income, net - Schedule of Other Income Net (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Income and Expenses [Abstract]
Foreign exchange losses	$ (1)	$ (8)
Interest income	248	234
Miscellaneous expenses	(53)	(20)
Other income, net	$ 194	$ 206