Other Financial Statement Data (Schedule Of Changes In Deferred Warranty Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Extended Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 346	$ 199	$ 475
Revenue deferrals	357	581	353
Amortization of deferred revenue	(444)	(434)	(629)
Total deferred warranty revenue	259	346	199
Current portion of deferred warranty revenue	(225)	(280)	(196)
Long-term deferred warranty revenue	$ 34	$ 66	$ 3