Income Taxes (Schedule Of Deferred Tax Assets And Valuation Allowance) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 18,333	$ 17,110
Share-based compensation	3,230	5,817
Research and development credit carryforwards	6,687	6,587
Other	264	237
Total deferred tax assets	28,514	29,751
Valuation allowance	(28,447)	(29,725)
Net deferred tax assets:	67	26
Deferred tax liabilities:
Property and equipment	(5)	(7)
Operating lease right-of-use assets	(62)	(19)
Total deferred tax liabilities:	(67)	(26)
Net deferred tax asset / (liability):