Note 5 - Fair Value of Financial Instruments - Assets Measured on Recurring Basis (Details) - USD ($)	Sep. 30, 2021	Mar. 31, 2021
Total	$ 60,647,982	$ 64,860,822
Money Market Funds [Member]
Total	10,442,555	10,143,196
Corporate Bond Securities [Member]
Total	50,205,427	54,717,626
Fair Value, Recurring [Member]
Total	60,647,982	64,860,822
Fair Value, Recurring [Member] | Money Market Funds [Member]
Total	10,442,555	10,143,196
Fair Value, Recurring [Member] | Corporate Bond Securities [Member]
Total	50,205,427	54,717,626
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total	10,442,555	10,143,196
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Total	10,442,555	10,143,196
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member]
Total	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total	50,205,427	54,717,626
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Total	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member]
Total	$ 50,205,427	$ 54,717,626