Balance Sheet Components - Property and Equipment Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment, Net
Total property and equipment, gross	$ 10,105	$ 9,226
Less: accumulated depreciation	(8,185)	(7,572)
Total property and equipment, net	1,920	1,654
Depreciation and amortization expense	700	1,200	$ 1,300
Manufacturing equipment
Property and Equipment, Net
Total property and equipment, gross	8,983	8,256
Computer and network equipment
Property and Equipment, Net
Total property and equipment, gross	588	546
Furniture and fixtures
Property and Equipment, Net
Total property and equipment, gross	188	184
Software
Property and Equipment, Net
Total property and equipment, gross	333	227
Leasehold improvements
Property and Equipment, Net
Total property and equipment, gross	$ 13	$ 13