Note 5 - Fair Value of Financial Instruments (Tables)
|
6 Months Ended |
Sep. 30, 2018 |
|---|
| Notes Tables |
|
| Investments Classified by Contractual Maturity Date [Table Text Block] |
| | | | | | | | | | | | | $ | 76,576,286 | | | $ | 29,716,134 | | | $ | 22,784,235 | | | $ | 24,075,917 | | |
| Fair Value, Assets Measured on Recurring Basis [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Money market funds | | $ | 5,774,385 | | | $ | - | | | $ | 5,774,385 | | | $ | 3,951,032 | | | $ | - | | | $ | 3,951,032 | | | Corporate bonds | | | - | | | | 70,801,901 | | | | 70,801,901 | | | | 54,517,969 | | | | 19,085,998 | | | | 73,603,967 | | | Total | | $ | 5,774,385 | | | $ | 70,801,901 | | | $ | 76,576,286 | | | $ | 58,469,001 | | | $ | 19,085,998 | | | $ | 77,554,999 | | |
| Schedule of Available-for-sale Securities Reconciliation [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Money market funds | | $ | 5,774,385 | | | $ | - | | | $ | - | | | $ | 5,774,385 | | | $ | 3,951,032 | | | $ | - | | | $ | - | | | $ | 3,951,032 | | | Corporate bonds | | | 72,122,677 | | | | - | | | | (1,320,776 | ) | | | 70,801,901 | | | | 74,853,327 | | | | - | | | | (1,249,360 | ) | | | 73,603,967 | | | Total | | $ | 77,897,062 | | | $ | - | | | $ | (1,320,776 | ) | | $ | 76,576,286 | | | $ | 78,804,359 | | | $ | - | | | $ | (1,249,360 | ) | | $ | 77,554,999 | | |
| Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As of September 30, 2018 | | | | | | | | | | | | | | | | | | | | | | | | | | Corporate bonds | | $ | 47,928,537 | | | $ | (580,584 | ) | | $ | 22,873,364 | | | $ | (740,192 | ) | | $ | 70,801,901 | | | $ | (1,320,776 | ) | | Total | | $ | 47,928,537 | | | $ | (580,584 | ) | | $ | 22,873,364 | | | $ | (740,192 | ) | | $ | 70,801,901 | | | $ | (1,320,776 | ) | | | | | | | | | | | | | | | | | | | | | | | | | | | | As of March 31, 2018 | | | | | | | | | | | | | | | | | | | | | | | | | | Corporate bonds | | $ | 61,731,248 | | | $ | (1,003,849 | ) | | $ | 9,072,719 | | | $ | (245,511 | ) | | $ | 70,803,967 | | | $ | (1,249,360 | ) | | Total | | $ | 61,731,248 | | | $ | (1,003,849 | ) | | $ | 9,072,719 | | | $ | (245,511 | ) | | $ | 70,803,967 | | | $ | (1,249,360 | ) | |