Other Financial Statement Data (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,095	$ 2,975
Accumulated Amortization	(2,715)	(2,537)
Net	380	438
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,687	2,567
Accumulated Amortization	(2,463)	(2,351)
Net	224	216
Software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(111)	(82)
Net	95	124
Marketing Assets and Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(45)	(33)
Net	56	68
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(96)	(71)
Net	$ 5	$ 30