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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Total revenue:
Total revenue	$ 14,180	$ 19,203	$ 29,276	$ 39,881
Long-lived assets:
Total long-lived assets	2,063		2,063		$ 5,692
North America [Member]
Total revenue:
Total revenue	12,039	18,179	26,567	37,468
Long-lived assets:
Total long-lived assets	1,405		1,405		1,578
Asia [Member]
Total revenue:
Total revenue	1,443	135	1,550	585
Long-lived assets:
Total long-lived assets	228		228		91
Europe [Member]
Total revenue:
Total revenue	698	$ 889	1,159	$ 1,828
Long-lived assets:
Total long-lived assets	$ 430		$ 430		$ 4,023