Note 3 - Debt Securities Available for Sale and Held to Maturity (Details Textual) - USD ($) $ in Thousands |
Jun. 30, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|---|---|
| Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest | $ 1 | $ 1 | $ 1 | $ 1 |
| Debt Securities, Available-for-Sale and Held-to-Maturity, Before Allowance for Credit Loss | 4,429,617 | 4,281,314 | ||
| Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Nonaccrual | 0 | |||
| Corporate Debt Securities [Member] | ||||
| Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest | 0 | |||
| Asset Pledged as Collateral [Member] | Public Deposits and Short-term Borrowed Funds [Member] | ||||
| Debt Securities, Available-for-Sale and Held-to-Maturity, Before Allowance for Credit Loss | $ 1,923,462 | $ 1,952,111 |