Revenue Concentrations, Significant Customers And Geographic Areas (Schedule Of Sales By Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue, Major Customer [Line Items]
Total export sales	$ 11,780	$ 10,605
Americas
Revenue, Major Customer [Line Items]
Total export sales	401	371
Europe
Revenue, Major Customer [Line Items]
Total export sales	2,103	2,658
China
Revenue, Major Customer [Line Items]
Total export sales	3,880	2,775
Taiwan
Revenue, Major Customer [Line Items]
Total export sales	1,716	2,144
Other Asia
Revenue, Major Customer [Line Items]
Total export sales	3,680	2,613
Other
Revenue, Major Customer [Line Items]
Total export sales	$ 0	$ 44