Balance Sheet Components - Schedule of Deferred Revenue (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred Revenue [Line Items]
Total deferred revenue	$ 19,933	$ 23,389
Less: current portion of deferred revenue	(15,540)	(20,151)
Noncurrent portion of deferred revenue	4,393	3,238
Product
Deferred Revenue [Line Items]
Total deferred revenue	11,917	18,861
Services
Deferred Revenue [Line Items]
Total deferred revenue	4,908	1,182
Distribution Rights
Deferred Revenue [Line Items]
Total deferred revenue	$ 3,108	$ 3,346