Investment Securities And Short-Term Investments (Schedule Of Short-Term Investments Measured at Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 123,100	$ 159,994
Gross Unrealized Gain	220	127
Gross Unrealized (Loss)	(58)	(87)
Fair Value	123,262	160,034
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,070	32,124
Gross Unrealized Gain	65	27
Gross Unrealized (Loss)		(13)
Fair Value	21,135	32,138
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	81,330	120,012
Gross Unrealized Gain	69	89
Gross Unrealized (Loss)	(58)	(74)
Fair Value	81,341	120,027
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,165
Fair Value		2,165
Government Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,700	5,693
Gross Unrealized Gain	86	11
Fair Value	$ 20,786	$ 5,704