Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 3,102		$ 3,102		$ 2,984
Less: accumulated depreciation	(2,687)		(2,687)		(2,595)
Property and equipment, net	415		415		389
Depreciation	46	$ 95	92	$ 200
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	1,317		$ 1,317		1,297
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	203		$ 203		203
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	1,046		$ 1,046		1,028
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	211		211		211
Finance lease right-of-use asset
Property, Plant and Equipment [Line Items]
Property and equipment at cost	13		13		13
Projects in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 128		$ 128		$ 48