Fixed Assets (Schedule of Depreciation and Amortization of Fixed Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Cost of sales	$ 27,042	$ 22,993	$ 21,289
Selling, general and administrative expenses	7,798	5,140	4,137
Total	$ 34,840	$ 28,133	$ 25,426