Other income, net - Schedule of Other Income Net (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Income and Expenses [Abstract]
Foreign exchange losses	$ (30)	$ (12)	$ (31)	$ (20)
Interest income	376	250	624	484
Miscellaneous expenses	(118)	(9)	(171)	(29)
Other income, net	$ 228	$ 229	$ 422	$ 435

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

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