Segments and Geographic Information - Schedule of Other Information by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Product revenues	$ 9,343	$ 9,569	$ 19,417	$ 17,295
Service revenues	5,717	4,387	11,167	7,908
License revenues	250		250
Total revenues	15,310	13,956	30,834	25,203
Cost of product revenues	6,158	5,303	12,174	9,617
Cost of service revenues	2,959	2,347	5,969	4,590
Total cost of revenues	9,117	7,650	18,143	14,207
Gross profit	6,193	6,306	12,691	10,996
Total operating expenses	8,136	6,662	13,618	12,807
Total non-operating income	729	(20)	485	(6)
Loss before income taxes	(1,214)	(376)	(442)	(1,817)
Product [Member]
Revenues
Product revenues	9,343	9,569	19,417	17,295
License revenues	250		250
Total revenues	9,593	9,569	19,667	17,295
Cost of product revenues	6,158	5,303	12,174	9,617
Total cost of revenues	6,158	5,303	12,174	9,617
Gross profit	3,435	4,266	7,493	7,678
Service [Member]
Revenues
Service revenues	5,717	4,387	11,167	7,908
Total revenues	5,717	4,387	11,167	7,908
Cost of service revenues	2,959	2,347	5,969	4,590
Total cost of revenues	2,959	2,347	5,969	4,590
Gross profit	$ 2,758	$ 2,040	$ 5,198	$ 3,318