Intangible Assets (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,223	$ 3,205
Accumulated Amortization	(2,943)	(2,895)
Net	280	310
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,916	2,898
Accumulated Amortization	(2,700)	(2,662)
Net	216	236
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(178)	(170)
Net	28	36
Marketing assets and customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(65)	(63)
Net	$ 36	$ 38