Note 5 - Marketable Securities - Reconciliation of Marketable Securities (Details) - USD ($)	Dec. 31, 2016	Mar. 31, 2016
Adjusted Cost	$ 84,537,083	$ 84,683,815
Gross Unrealized Gains	123,045	719,728
Gross Unrealized Losses	(336,187)	(10,824)
Fair Market Value	84,323,941	85,392,719
Corporate Bond Securities [Member]
Adjusted Cost	83,222,388	83,339,487
Gross Unrealized Gains	123,045	717,206
Gross Unrealized Losses	(334,944)	(10,824)
Fair Market Value	83,010,489	84,045,869
Municipal Bonds [Member]
Adjusted Cost	1,314,695	1,344,328
Gross Unrealized Gains		2,522
Gross Unrealized Losses	(1,243)
Fair Market Value	$ 1,313,452	$ 1,346,850

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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