Balance Sheet Components - Components of Inventory and Printed Circuit Board Assemblies ("PCBAs") (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Inventory [Line Items]
Total inventory and printed circuit board assemblies	$ 4,227	$ 4,037
Raw materials
Inventory [Line Items]
Total inventory and printed circuit board assemblies	1,666	1,574
Finished goods
Inventory [Line Items]
Total inventory and printed circuit board assemblies	$ 2,561	$ 2,463