Information about Geographic Areas and Operating Segments - Revenue and Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Total revenue:
Total revenue	$ 20,678	$ 22,841
Long-lived assets:
Total long-lived assets	5,190		$ 5,181
North America [Member]
Total revenue:
Total revenue	19,289	21,770
Long-lived assets:
Total long-lived assets	986		991
Asia [Member]
Total revenue:
Total revenue	450	249
Long-lived assets:
Total long-lived assets	94		76
Europe [Member]
Total revenue:
Total revenue	939	$ 822
Long-lived assets:
Total long-lived assets	$ 4,110		$ 4,114