Balance Sheet Components - Schedule of Deferred Revenue (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Deferred Revenue [Line Items]
Total deferred revenue	$ 13,145	$ 19,475
Less: current portion of deferred revenue	(8,232)	(13,731)
Noncurrent portion of deferred revenue	4,913	5,744
Product
Deferred Revenue [Line Items]
Total deferred revenue	1,729	9,623
Service
Deferred Revenue [Line Items]
Total deferred revenue	8,782	6,981
Distribution Rights
Deferred Revenue [Line Items]
Total deferred revenue	$ 2,634	$ 2,871