Information about Operating Segments and Geographic Areas - Revenue and Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Total revenue:
Total revenue	$ 19,469	$ 19,653	$ 18,848	$ 22,841	$ 26,797	$ 22,467	$ 22,738	$ 25,439	$ 80,811	$ 97,441
Long-lived assets:
Total long-lived assets	5,181				5,351				5,181	5,351
North America [Member]
Total revenue:
Total revenue									76,062	92,299
Long-lived assets:
Total long-lived assets	991				1,025				991	1,025
Asia [Member]
Total revenue:
Total revenue									1,644	2,024
Long-lived assets:
Total long-lived assets	76				90				76	90
Europe [Member]
Total revenue:
Total revenue									3,105	3,118
Long-lived assets:
Total long-lived assets	$ 4,114				$ 4,236				$ 4,114	$ 4,236