Other Financial Statement Data (Schedule Of Amortization Expense For Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 178	$ 165	$ 176
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 112	98	110
Intangible assets acquired, Weighted Average Life (in years)	2 years
Software [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 29	29	29
Intangible assets acquired, Weighted Average Life (in years)	3 years 2 months 12 days
Marketing Assets and Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 12	12	12
Intangible assets acquired, Weighted Average Life (in years)	4 years 9 months 18 days
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 25	$ 26	$ 25
Intangible assets acquired, Weighted Average Life (in years)	2 months 12 days