Consolidated Balance Sheet Details - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,524	$ 13,224
Less accumulated depreciation	(1,279)	(11,514)
Property and equipment, net	245	1,710
Machinery, equipment and tooling [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	0	11,011
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	0	104
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	141	78
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	976	1,372
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 407	$ 659