Note 5 - Fair Value of Financial Instruments (Details Textual) |
3 Months Ended |
|---|---|
Jun. 30, 2020 | |
| Available for Sale Debt Securitites, Percent of Total Assets | 89.00% |
| Minimum [Member] | |
| Available for Sale Debt Securities, Remaining Maturity (Month) | 120 days |
| Maximum [Member] | |
| Available for Sale Debt Securities, Remaining Maturity (Month) | 3 years 240 days |