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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue, Major Customer [Line Items]
Total export sales	$ 7,764	$ 12,621	$ 29,270	$ 43,943
Americas
Revenue, Major Customer [Line Items]
Total export sales	159	344	976	1,114
Europe
Revenue, Major Customer [Line Items]
Total export sales	2,543	3,592	9,114	13,463
Asia
Revenue, Major Customer [Line Items]
Total export sales	4,959	8,675	18,933	29,322
Other
Revenue, Major Customer [Line Items]
Total export sales	$ 103	$ 10	$ 247	$ 44