Revenue Concentrations, Significant Customers And Geographic Areas (Schedule Of Sales By Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Major Customer [Line Items]
Total export sales	$ 9,574	$ 11,886	$ 31,094	$ 33,424
Americas
Revenue, Major Customer [Line Items]
Total export sales	418	355	994	568
Europe
Revenue, Major Customer [Line Items]
Total export sales	1,926	4,093	6,189	9,360
China
Revenue, Major Customer [Line Items]
Total export sales	2,135	2,354	8,469	7,750
Taiwan
Revenue, Major Customer [Line Items]
Total export sales	842	794	3,986	1,635
Other Asia
Revenue, Major Customer [Line Items]
Total export sales	4,005	3,942	10,824	13,563
Other
Revenue, Major Customer [Line Items]
Total export sales	$ 248	$ 348	$ 632	$ 548