Financial Statement Details - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 26,773	$ 25,134
Less—accumulated depreciation and amortization	(16,017)	(18,436)
Property, plant and equipment, net	10,756	6,698
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	253	247
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,303	2,247
Test equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,952	14,444
Computer equipment and purchased software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,911	4,889
Product tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,139	504
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,535	677
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,535	1,990
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 145	$ 136