Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Allocation (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 503	$ 504	$ 1,069	$ 845
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	39	31	77	59
Sales and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	12	12	25	23
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	40	71	58	28
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 412	$ 390	$ 909	$ 735