Fair Value Of Financial Instruments (Fair Value Of Financial Assets Measured On A Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Total assets measured at fair value	$ 28,114	$ 24,928
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
ASSETS
Total cash and cash equivalents	5,598	6,429
Investments [Member] | U.S. Treasury Securities [Member]
ASSETS
Total investments	22,516	18,499
Level 1 [Member]
ASSETS
Total assets measured at fair value	5,598	6,429
Level 1 [Member] | Cash And Cash Equivalents [Member] | Money Market Funds [Member]
ASSETS
Total cash and cash equivalents	5,598	6,429
Level 2 [Member]
ASSETS
Total assets measured at fair value	22,516	18,499
Level 2 [Member] | Investments [Member] | U.S. Treasury Securities [Member]
ASSETS
Total investments	$ 22,516	$ 18,499