Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 6,198		$ 6,198		$ 5,258
Less: accumulated depreciation	(3,059)		(3,059)		(2,829)
Property and equipment, net	3,139		3,139		2,429
Depreciation	185	$ 52	336	$ 101
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment at cost	3,388		$ 3,388		$ 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	802		$ 802		$ 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]
Property and equipment at cost	78		$ 78		$ 39
Useful life			5 years		5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment at cost	170		$ 170		$ 104
Useful life			5 years		5 years
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment at cost	707		$ 707		$ 581
Useful life			3 years		3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment at cost	534		$ 534		$ 509
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment at cost	$ 519		$ 519		$ 310