Note 3 - Fair Value of Financial Instruments - Reconciliation of Available-for-sale Securities (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2019
Amortized Cost	$ 69,933,553	$ 74,223,159
Gross Unrealized Holding Gains	752,621	315,902
Gross Unrealized Holding Losses	(91,432)	(421,798)
Estimated Fair Value	70,594,742	74,117,263
Money Market Funds [Member]
Amortized Cost	7,903,433	6,703,809
Gross Unrealized Holding Gains
Gross Unrealized Holding Losses
Estimated Fair Value	7,903,433	6,703,809
Corporate Bond Securities [Member]
Amortized Cost	62,030,120	67,519,350
Gross Unrealized Holding Gains	752,621	315,902
Gross Unrealized Holding Losses	(91,432)	(421,798)
Estimated Fair Value	$ 62,691,309	$ 67,413,454

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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