Other Financial Statement Data (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,306	$ 3,162
Accumulated Amortization	(2,996)	(2,829)
Net	310	333
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,898	2,754
Accumulated Amortization	(2,662)	(2,533)
Net	236	221
Software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(170)	(141)
Net	36	65
Marketing Assets and Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(63)	(54)
Net	38	47
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(101)	(101)
Net	$ 0	$ 0