Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Machinery, equipment and vehicles	$ 16,078	$ 14,810
Furniture and fixtures	3,090	3,118
Leasehold improvements	1,967	1,823
Buildings	331	302
Property, Plant and Equipment, Gross, Total	21,466	20,053
Accumulated depreciation and amortization	(16,343)	(15,506)
Property, Plant and Equipment, Net, Total	$ 5,123	$ 4,547