Note 5 - Reconciliation of Marketable Securities (Details) - USD ($)	Sep. 30, 2015	Mar. 31, 2015
Corporate Bond Securities [Member]
Adjusted Cost	$ 81,960,402	$ 88,456,886
Gross Unrealized Gains	645,841	1,185,469
Gross Unrealized Losses	(17,615)	(16,371)
Available-for-sale Securities, Debt Securities	82,588,628	89,625,984
Municipal Bonds [Member]
Adjusted Cost	1,364,084	1,383,839
Gross Unrealized Gains	$ 4,064	$ 3,272
Gross Unrealized Losses
Available-for-sale Securities, Debt Securities	$ 1,368,148	$ 1,387,111
Adjusted Cost	83,324,486	89,840,725
Gross Unrealized Gains	649,905	1,188,741
Gross Unrealized Losses	(17,615)	(16,371)
Available-for-sale Securities, Debt Securities	$ 83,956,776	$ 91,013,095