Note 8 - Fair Value Disclosures and Reporting and Fair Value Measurements - Level 3 Quantitative Information (Details) - USD ($) $ in Thousands |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Total available-for-sale securities | $ 584,897 | $ 625,330 |
| Corporate Debt Securities [Member] | ||
| Total available-for-sale securities | 83,836 | 86,467 |
| Fair Value, Recurring [Member] | ||
| Total available-for-sale securities | 584,897 | 625,330 |
| Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | ||
| Total available-for-sale securities | 83,836 | 86,467 |
| Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | ||
| Total available-for-sale securities | 1,423 | 1,313 |
| Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | ||
| Total available-for-sale securities | $ 1,423 | $ 1,313 |