Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 6,423		$ 6,423		$ 5,258
Less: accumulated depreciation	(3,110)		(3,110)		(2,829)
Property and equipment, net	3,313		3,313		2,429
Depreciation	219	$ 79	555	$ 181
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	3,470		$ 3,470		$ 2,864
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life			3 years		3 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life			15 years		15 years
Tooling
Property, Plant and Equipment [Line Items]
Property and equipment at cost	833		$ 833		$ 851
Tooling | Minimum
Property, Plant and Equipment [Line Items]
Useful life			2 years		2 years
Tooling | Maximum
Property, Plant and Equipment [Line Items]
Useful life			5 years		5 years
Vehicles
Property, Plant and Equipment [Line Items]
Useful life			5 years		5 years
Property and equipment at cost	78		$ 78		$ 39
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful life			5 years		5 years
Property and equipment at cost	170		$ 170		$ 104
Computer software
Property, Plant and Equipment [Line Items]
Useful life			3 years		3 years
Property and equipment at cost	1,060		$ 1,060		$ 581
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	551		551		509
Projects in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 261		$ 261		$ 310