Balance Sheet Components - Schedule of Deferred Revenue (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deferred Revenue [Line Items]
Total deferred revenue	$ 15,794	$ 19,475
Less: current portion of deferred revenue	(10,287)	(13,731)
Noncurrent portion of deferred revenue	5,507	5,744
Product
Deferred Revenue [Line Items]
Total deferred revenue	5,424	9,623
Service
Deferred Revenue [Line Items]
Total deferred revenue	7,618	6,981
Distribution Rights
Deferred Revenue [Line Items]
Total deferred revenue	$ 2,752	$ 2,871