Investments In Securities (Schedule Of Gross Realized Gains And Losses On Securities) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Total, Gross realized gains	$ 90,605	$ 303,116
Total, Gross realized losses	(99)	(159,831)
Net realized gain from securities	90,506	143,285
Gain on other investments	12,833	6,545
Total	12,833	6,545
Net realized gain on investments	103,339	149,830
Issuer Obligations Of U S States Territories And Political Subdivisions Special Revenue [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Gross realized gains	139	160
Total, Gross realized losses	(99)	(85)
Common Stocks And Nonredeemable Preferred Stocks
Schedule of Available-for-sale Securities [Line Items]
Total, Gross realized gains	90,466	227,960
Total, Gross realized losses	0	(116,952)
Auction Rate Securities
Schedule of Available-for-sale Securities [Line Items]
Total, Gross realized gains		74,996
Impairments of Debt And Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Gross realized losses	$ 0	$ (42,794)