Information about Geographic Areas and Operating Segments - Total Revenue and Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Total revenue:
Total revenue	$ 15,096	$ 20,678
Long-lived assets:
Total long-lived assets	1,886		$ 5,692
North America [Member]
Total revenue:
Total revenue	14,528	19,289
Long-lived assets:
Total long-lived assets	1,545		1,578
Asia [Member]
Total revenue:
Total revenue	107	450
Long-lived assets:
Total long-lived assets	83		91
Europe [Member]
Total revenue:
Total revenue	461	$ 939
Long-lived assets:
Total long-lived assets	$ 258		$ 4,023