Total Net Revenue Based on Disaggregation Criteria (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 19,522	$ 16,528
Point-in-Time
Disaggregation Of Revenue [Line Items]
Total net revenue	18,256	15,763
Over Time
Disaggregation Of Revenue [Line Items]
Total net revenue	1,266	765
Americas
Disaggregation Of Revenue [Line Items]
Total net revenue	14,725	13,232
Americas | Point-in-Time
Disaggregation Of Revenue [Line Items]
Total net revenue	13,524	12,484
Americas | Over Time
Disaggregation Of Revenue [Line Items]
Total net revenue	1,201	748
Europe and the Middle East
Disaggregation Of Revenue [Line Items]
Total net revenue	2,930	2,308
Europe and the Middle East | Point-in-Time
Disaggregation Of Revenue [Line Items]
Total net revenue	2,865	2,294
Europe and the Middle East | Over Time
Disaggregation Of Revenue [Line Items]
Total net revenue	65	14
Asia-Pacific
Disaggregation Of Revenue [Line Items]
Total net revenue	1,867	988
Asia-Pacific | Point-in-Time
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 1,867	985
Asia-Pacific | Over Time
Disaggregation Of Revenue [Line Items]
Total net revenue		$ 3