Balance Sheet Components - Schedule of Deferred Revenue (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred Revenue [Line Items]
Total deferred revenue	$ 14,160	$ 19,475
Less: current portion of deferred revenue	(9,644)	(13,731)
Noncurrent portion of deferred revenue	4,516	5,744
Product
Deferred Revenue [Line Items]
Total deferred revenue	3,654	9,623
Service
Deferred Revenue [Line Items]
Total deferred revenue	7,991	6,981
Distribution Rights
Deferred Revenue [Line Items]
Total deferred revenue	$ 2,515	$ 2,871