Marketable Securities (Schedule Of Cost And Fair Value Of Marketable Securities) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Cost Basis		$ 17,988,827
Gross Unrealized Losses		(56,886)
Fair Value		17,931,941
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis		3,241,005
Gross Unrealized Losses		(2,505)
Fair Value		3,238,500
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 5,999,356	14,747,822
Gross Unrealized Losses	(17,836)	(54,381)
Fair Value	$ 5,981,520	$ 14,693,441