14. Foreign Customer Sales (Details) - Foreign Sales [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Revenue, Major Customer [Line Items]
Total foreign sales	$ 18,336	$ 14,620
Sales Revenue [Member] | Canada, Mexico & South/Central America [Member]
Revenue, Major Customer [Line Items]
Total foreign sales	3,067	2,608
Sales Revenue [Member] | Pacific Rim [Member]
Revenue, Major Customer [Line Items]
Total foreign sales	3,678	2,418
Sales Revenue [Member] | Europe Africa And Middle East [Member]
Revenue, Major Customer [Line Items]
Total foreign sales	$ 11,591	$ 9,594