Note 5 - Marketable Securities (Details Textual)
|
Sep. 30, 2017
USD ($)
|
Mar. 31, 2017
USD ($)
|
| Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions |
9
|
|
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value |
$ 7,611,641
|
|
| Number of Other-than-temporarily Impaired Marketable Securities |
0
|
|
| Corporate Bond Securities [Member] |
|
|
| Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year |
3
|
|
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value |
$ 7,611,641
|
|