Revenue Concentrations, Significant Customers, and Geographic Areas (Schedule Of Long-lived Assets Attributable To Each Geographic Area's Operations) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 2,687	$ 2,876
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	2,348	2,721
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	4	7
Asia And Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 335	$ 148