Information about Geographic Areas and Operating Segments - Total Revenue and Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Total revenue:
Total revenue	$ 19,203	$ 18,848	$ 39,881	$ 41,689
Long-lived assets:
Total long-lived assets	5,479		5,479		$ 5,181
North America [Member]
Total revenue:
Total revenue	18,179	17,728	37,468	39,498
Long-lived assets:
Total long-lived assets	1,285		1,285		991
Asia [Member]
Total revenue:
Total revenue	135	306	585	555
Long-lived assets:
Total long-lived assets	113		113		76
Europe [Member]
Total revenue:
Total revenue	889	$ 814	1,828	$ 1,636
Long-lived assets:
Total long-lived assets	$ 4,081		$ 4,081		$ 4,114