Note 5 - Fair Value of Financial Instruments - Assets Measured on Recurring Basis (Details) - USD ($)
|
Dec. 31, 2018 |
Mar. 31, 2018 |
| Total |
$ 75,268,216
|
$ 77,554,999
|
| Money Market Funds [Member] |
|
|
| Total |
5,915,078
|
3,951,032
|
| Corporate Bond Securities [Member] |
|
|
| Total |
69,353,138
|
73,603,967
|
| Fair Value, Measurements, Recurring [Member] |
|
|
| Total |
75,268,216
|
77,554,999
|
| Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] |
|
|
| Total |
5,915,078
|
3,951,032
|
| Fair Value, Measurements, Recurring [Member] | Corporate Bond Securities [Member] |
|
|
| Total |
69,353,138
|
73,603,967
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |
|
|
| Total |
5,915,078
|
58,469,001
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] |
|
|
| Total |
5,915,078
|
3,951,032
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member] |
|
|
| Total |
|
54,517,969
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |
|
|
| Total |
69,353,138
|
19,085,998
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] |
|
|
| Total |
|
|
| Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member] |
|
|
| Total |
$ 69,353,138
|
$ 19,085,998
|