Information about Geographic Areas - Classification of Revenue by Geography (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 28,616	$ 27,016	$ 76,700	$ 79,672
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	21,032	20,060	53,865	59,612
Europe & Middle East
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	6,110	4,911	18,260	14,564
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,474	$ 2,045	$ 4,575	$ 5,496