Other income, net - Schedule of Other Income Net (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Income and Expenses [Abstract]
Interest income	$ 436	$ 376	$ 886	$ 624
Foreign exchange losses	(9)	(30)	(7)	(31)
Miscellaneous expenses		(118)	(1)	(171)
Total Other income (expenses)	$ 427	$ 228	$ 878	$ 422

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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