Note 4 - Marketable Securities - Reconciliation of Marketable Securities (Details) - USD ($)	Mar. 31, 2017	Mar. 31, 2016
Adjusted Cost	$ 76,462,904	$ 84,683,815
Gross Unrealized Gains	187,001	719,728
Gross Unrealized Losses	(247,149)	(10,824)
Fair Market Value	76,402,756	85,392,719
Corporate Bond Securities [Member]
Adjusted Cost	75,158,087	83,339,487
Gross Unrealized Gains	187,001	717,206
Gross Unrealized Losses	(246,935)	(10,824)
Fair Market Value	75,098,153	84,045,869
Municipal Bonds [Member]
Adjusted Cost	1,304,817	1,344,328
Gross Unrealized Gains		2,522
Gross Unrealized Losses	(214)
Fair Market Value	$ 1,304,603	$ 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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