Other Financial Statement Data (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,162	$ 3,095
Accumulated Amortization	(2,829)	(2,715)
Net	333	380
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,754	2,687
Accumulated Amortization	(2,533)	(2,463)
Net	221	224
Software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(141)	(111)
Net	65	95
Marketing Assets and Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(54)	(45)
Net	47	56
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(101)	(96)
Net	$ 0	$ 5