Note 5 - Marketable Securities - Reconciliation of Marketable Securities (Details) - USD ($) |
Dec. 31, 2016 |
Mar. 31, 2016 |
|---|---|---|
| Adjusted Cost | $ 84,537,083 | $ 84,683,815 |
| Gross Unrealized Gains | 123,045 | 719,728 |
| Gross Unrealized Losses | (336,187) | (10,824) |
| Fair Market Value | 84,323,941 | 85,392,719 |
| Corporate Bond Securities [Member] | ||
| Adjusted Cost | 83,222,388 | 83,339,487 |
| Gross Unrealized Gains | 123,045 | 717,206 |
| Gross Unrealized Losses | (334,944) | (10,824) |
| Fair Market Value | 83,010,489 | 84,045,869 |
| Municipal Bonds [Member] | ||
| Adjusted Cost | 1,314,695 | 1,344,328 |
| Gross Unrealized Gains | 2,522 | |
| Gross Unrealized Losses | (1,243) | |
| Fair Market Value | $ 1,313,452 | $ 1,346,850 |