Information about Geographic Areas - Classification of Revenue by Geography (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 30,032	$ 28,616	$ 24,999	$ 23,085	$ 35,234	$ 27,016	$ 34,592	$ 18,063	$ 106,732	$ 114,905	$ 86,489
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									74,137	86,099	60,330
Europe & Middle East
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									25,715	21,791	18,497
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 6,880	$ 7,015	$ 7,662