Intangible Assets (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,158	$ 2,139
Accumulated Amortization	(1,855)	(1,814)
Net	303	325
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,866	1,832
Accumulated Amortization	(1,585)	(1,542)
Net	281	290
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(206)	(200)
Net	0	6
Marketing assets and customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	86	101
Accumulated Amortization	(64)	(72)
Net	$ 22	$ 29