Note 5 - Reconciliation of Marketable Securities (Details) - USD ($)	Jun. 30, 2015	Mar. 31, 2015
Corporate Bond Securities [Member]
Adjusted Cost	$ 85,929,786	$ 88,456,886
Gross Unrealized Gains	724,435	1,185,469
Gross Unrealized Losses	(36,779)	(16,371)
Available-for-sale Securities	86,617,442	89,625,984
Municipal Bonds [Member]
Adjusted Cost	1,373,962	1,383,839
Gross Unrealized Gains	$ 185	$ 3,272
Gross Unrealized Losses
Available-for-sale Securities	$ 1,374,147	$ 1,387,111
Adjusted Cost	87,303,748	89,840,725
Gross Unrealized Gains	724,620	1,188,741
Gross Unrealized Losses	(36,779)	(16,371)
Available-for-sale Securities	$ 87,991,589	$ 91,013,095