Note 5 - Fair Value of Financial Instruments - Investment Securities With Unrealized Losses (Details) - USD ($) |
Jun. 30, 2021 |
Mar. 31, 2021 |
|---|---|---|
| Fair market value, less than 12 months | $ 10,354,738 | $ 10,322,539 |
| Gross unrealized losses, less than 12 months | (95,650) | (160,674) |
| Fair market value, 12 months or greater | 0 | 0 |
| Gross unrealized losses, 12 months or greater | 0 | 0 |
| Total fair market value | 10,354,738 | 10,322,539 |
| Total gross unrealized losses | (95,650) | (160,674) |
| Corporate Bond Securities [Member] | ||
| Fair market value, less than 12 months | 10,354,738 | 10,322,539 |
| Gross unrealized losses, less than 12 months | (95,650) | (160,674) |
| Fair market value, 12 months or greater | 0 | 0 |
| Gross unrealized losses, 12 months or greater | 0 | 0 |
| Total fair market value | 10,354,738 | 10,322,539 |
| Total gross unrealized losses | $ (95,650) | $ (160,674) |