Note 5 - Marketable Securities - Reconciliation of Marketable Securities (Details) - USD ($)	Jun. 30, 2017	Mar. 31, 2017
Gross Unrealized Gains	$ 181,106	$ 187,001
Gross Unrealized Losses	(154,828)	(247,149)
Total	80,210,820	76,402,756
Adjusted Cost	80,184,542	76,462,904
Corporate Bond Securities [Member]
Gross Unrealized Gains	181,106	187,001
Gross Unrealized Losses	(154,146)	(246,935)
Total	78,916,563	75,098,153
Adjusted Cost	78,889,603	75,158,087
Municipal Bonds [Member]
Gross Unrealized Gains
Gross Unrealized Losses	(682)	(214)
Total	1,294,257	1,304,603
Adjusted Cost	$ 1,294,939	$ 1,304,817

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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