Information about Geographic Areas and Operating Segments - Total Revenue and Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Total revenue:
Total revenue	$ 14,641	$ 16,694	$ 43,917	$ 56,575
Long-lived assets:
Total long-lived assets	1,607		1,607		$ 5,692
North America [Member]
Total revenue:
Total revenue	12,714	15,441	39,281	52,909
Long-lived assets:
Total long-lived assets	1,027		1,027		1,578
Asia [Member]
Total revenue:
Total revenue	1,586	579	3,136	1,164
Long-lived assets:
Total long-lived assets	200		200		91
Europe [Member]
Total revenue:
Total revenue	341	$ 674	1,500	$ 2,502
Long-lived assets:
Total long-lived assets	$ 380		$ 380		$ 4,023