Investment Securities (Details Textual) - USD ($) |
May 30, 2020 |
Feb. 29, 2020 |
|---|---|---|
| Debt Securities, Available-for-sale [Line Items] | ||
| Short term held-to-maturity securities | $ 29,500,000 | $ 385,600,000 |
| Auction Rate Securities [Member] | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Long term available-for-sale investment securities | 20,300,000 | 20,300,000 |
| Valuation adjustments | $ (447,000) | $ (5,000) |