Property and Equipment and Assets Held For Sale (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 3,453		$ 3,453		$ 3,411
Less: accumulated depreciation	(2,606)		(2,606)		(2,314)
Property and equipment, net	847		847		1,097
Depreciation	100	$ 200	300	$ 300
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	1,582		$ 1,582		1,557
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		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		47
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful life			5 years
Property and equipment at cost	137		$ 137		137
Computer software
Property, Plant and Equipment [Line Items]
Useful life			3 years
Property and equipment at cost	1,043		$ 1,043		1,043
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	211		211		201
Projects in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 62		$ 62		$ 55