Segment Information - Long-Lived Assets by Location (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 25,660	$ 28,591
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	20,773	23,697
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	4,672	4,640
Rest of World [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 215	$ 254