Other Financial Statement Data (Schedule Of Changes In Deferred Warranty Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Movement in Extended Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 344	$ 275
Revenue deferrals	147	134
Amortization of deferred revenue	(106)	(100)
Total deferred warranty revenue	385	309
Current portion of deferred warranty revenue	(281)	(227)
Long-term deferred warranty revenue	$ 104	$ 82