Intangible Assets (Schedule Of Intangible Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,094	$ 3,095
Accumulated Amortization	(2,764)	(2,715)
Net	330	380
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,686	2,687
Accumulated Amortization	(2,487)	(2,463)
Net	199	224
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	206
Accumulated Amortization	(126)	(111)
Net	80	95
Marketing assets and customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(50)	(45)
Net	51	56
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	101	101
Accumulated Amortization	(101)	(96)
Net	$ 0	$ 5