Segment and Geographic Information - Summary of Revenue by Geographic Area on the Customers' Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Entity Wide Revenue Major Customer [Line Items]
Total revenue	$ 34,042	$ 22,237	$ 10,390
Reportable Geographical Components | United States
Entity Wide Revenue Major Customer [Line Items]
Total revenue	11,506	1,106	5,332
Reportable Geographical Components | UAE
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,675	0	0
Reportable Geographical Components | Korea
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,504	182	4,988
Reportable Geographical Components | Israel
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,309	0	0
Reportable Geographical Components | China
Entity Wide Revenue Major Customer [Line Items]
Total revenue	4,680	0	0
Reportable Geographical Components | Japan
Entity Wide Revenue Major Customer [Line Items]
Total revenue	753	10,375	0
Reportable Geographical Components | Netherlands
Entity Wide Revenue Major Customer [Line Items]
Total revenue	317	5,486	0
Reportable Geographical Components | Italy
Entity Wide Revenue Major Customer [Line Items]
Total revenue	298	5,088	0
Reportable Geographical Components | Rest of World
Entity Wide Revenue Major Customer [Line Items]
Total revenue	$ 0	$ 0	$ 70