Note 5 - Fair Value of Financial Instruments - Assets Measured on Recurring Basis (Details) - USD ($)
Jun. 30, 2021
Mar. 31, 2021
Total $ 62,756,448 $ 64,860,822
Money Market Funds [Member]    
Total 8,231,700 10,143,196
Corporate Bond Securities [Member]    
Total 54,524,748 54,717,626
Fair Value, Recurring [Member]    
Total 62,756,448 64,860,822
Fair Value, Recurring [Member] | Money Market Funds [Member]    
Total 8,231,700 10,143,196
Fair Value, Recurring [Member] | Corporate Bond Securities [Member]    
Total 54,524,748 54,717,626
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Total 8,231,700 10,143,196
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]    
Total 8,231,700 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 54,524,748 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 $ 54,524,748 $ 54,717,626