Note 5 - Marketable Securities - Reconciliation of Marketable Securities (Details) - USD ($) |
Sep. 30, 2017 |
Mar. 31, 2017 |
|---|---|---|
| Adjusted Cost | $ 76,498,214 | $ 76,462,904 |
| Gross Unrealized Gains | 197,573 | 187,001 |
| Gross Unrealized Losses | (151,289) | (247,149) |
| Fair Market Value | 76,544,498 | 76,402,756 |
| Corporate Bond Securities [Member] | ||
| Adjusted Cost | 76,498,214 | 75,158,087 |
| Gross Unrealized Gains | 197,573 | 187,001 |
| Gross Unrealized Losses | (151,289) | (246,935) |
| Fair Market Value | 76,544,498 | 75,098,153 |
| Municipal Bonds [Member] | ||
| Adjusted Cost | 1,304,817 | |
| Gross Unrealized Gains | ||
| Gross Unrealized Losses | (214) | |
| Fair Market Value | $ 1,304,603 |