Other income, net - Schedule of Other Income Net (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Income and Expenses [Abstract]
Interest income	$ 392	$ 469	$ 1,278	$ 1,093
Foreign exchange losses	1	(3)	(6)	(34)
Miscellaneous expenses	(9)	(262)	(10)	(433)
Total Other income (expenses)	$ 384	$ 204	$ 1,262	$ 626