Property and Equipment and Assets Held For Sale - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 3,374		$ 3,375
Less: accumulated depreciation	(2,864)		(2,765)
Property and equipment, net	510		610
Depreciation	105	$ 151
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 1,491		1,511
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	15 years
Tooling
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 371		371
Tooling | Minimum
Property, Plant and Equipment [Line Items]
Useful life	2 years
Tooling | Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Vehicles
Property, Plant and Equipment [Line Items]
Useful life	5 years
Property and equipment at cost	$ 47		47
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful life	5 years
Property and equipment at cost	$ 137		137
Computer software
Property, Plant and Equipment [Line Items]
Useful life	3 years
Property and equipment at cost	$ 1,043		1,043
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	211		211
Finance lease right-of-use asset
Property, Plant and Equipment [Line Items]
Property and equipment at cost	13		0
Projects in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 61		$ 55