Note 5 - Fair Value of Financial Instruments - Reconciliation of Available-for-sale Securities (Details) - USD ($) |
Dec. 31, 2021 |
Mar. 31, 2021 |
|---|---|---|
| Amortized Cost | $ 56,738,624 | $ 63,451,301 |
| Gross Unrealized Holding Gains | 772,080 | 1,570,195 |
| Gross Unrealized Holding Losses | (216,834) | (160,674) |
| Estimated Fair Value | 57,293,870 | 64,860,822 |
| Amortized Cost | 56,738,624 | 63,451,301 |
| Money Market Funds [Member] | ||
| Amortized Cost | 7,631,824 | 10,143,196 |
| Gross Unrealized Holding Gains | 0 | 0 |
| Gross Unrealized Holding Losses | 0 | 0 |
| Estimated Fair Value | 7,631,824 | 10,143,196 |
| Amortized Cost | 7,631,824 | 10,143,196 |
| Corporate Bond Securities [Member] | ||
| Amortized Cost | 49,106,800 | 53,308,105 |
| Gross Unrealized Holding Gains | 772,080 | 1,570,195 |
| Gross Unrealized Holding Losses | (216,834) | (160,674) |
| Estimated Fair Value | 49,662,046 | 54,717,626 |
| Amortized Cost | $ 49,106,800 | $ 53,308,105 |