Note 4 - Marketable Securities (Details Textual) |
Mar. 31, 2018
USD ($)
|
Mar. 31, 2017
USD ($)
|
|---|---|---|
| Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Total | 19 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | $ 9,072,719 | |
| Number of Other-than-temporarily Impaired Marketable Securities | 0 |