Note 3 - Fair Value of Financial Instruments - Reconciliation of Available-for-sale Securities (Details) - USD ($)	Mar. 31, 2021	Mar. 31, 2020
Amortized Cost	$ 63,451,301	$ 69,933,553
Gross Unrealized Holding Gains	1,570,195	752,621
Gross Unrealized Holding Losses	(160,674)	(91,432)
Estimated Fair Value	64,860,822	70,594,742
Money Market Funds [Member]
Amortized Cost	10,143,196	7,903,433
Gross Unrealized Holding Gains
Gross Unrealized Holding Losses
Estimated Fair Value	10,143,196	7,903,433
Corporate Bond Securities [Member]
Amortized Cost	53,308,105	62,030,120
Gross Unrealized Holding Gains	1,570,195	752,621
Gross Unrealized Holding Losses	(160,674)	(91,432)
Estimated Fair Value	$ 54,717,626	$ 62,691,309

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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