Note 5 - Fair Value of Financial Instruments - Reconciliation of Available-for-sale Securities (Details) - USD ($) |
Jun. 30, 2021 |
Mar. 31, 2021 |
|---|---|---|
| Amortized Cost | $ 61,462,346 | $ 63,451,301 |
| Gross Unrealized Holding Gains | 1,389,752 | 1,570,195 |
| Gross Unrealized Holding Losses | (95,650) | (160,674) |
| Estimated Fair Value | 62,756,448 | 64,860,822 |
| Money Market Funds [Member] | ||
| Amortized Cost | 8,231,700 | 10,143,196 |
| Gross Unrealized Holding Gains | 0 | 0 |
| Gross Unrealized Holding Losses | 0 | 0 |
| Estimated Fair Value | 8,231,700 | 10,143,196 |
| Corporate Bond Securities [Member] | ||
| Amortized Cost | 53,230,646 | 53,308,105 |
| Gross Unrealized Holding Gains | 1,389,752 | 1,570,195 |
| Gross Unrealized Holding Losses | (95,650) | (160,674) |
| Estimated Fair Value | $ 54,524,748 | $ 54,717,626 |