Summary of Significant Accounting Policies - Summary of Product Revenue by Geographical Locations of Customers (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Total product revenue	$ 13,564	$ 7,006
North America
Disaggregation Of Revenue [Line Items]
Total product revenue	2,387	1,065
Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Total product revenue	11,006	5,911
Other
Disaggregation Of Revenue [Line Items]
Total product revenue	$ 171	$ 30