Note 7 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Due in one year or less, Amortized Cost	$ 661,864
Due in one year or less, Fair Value	661,135
Due after one year through five years, Amortized Cost	207,407
Due after one year through five years, Fair Value	198,023
Due after five years through ten years, Amortized Cost	140,147
Due after five years through ten years, Fair Value	131,192
Due after ten years, Amortized Cost	774,497
Due after ten years, Fair Value	662,817
Total, Amortized Cost	1,783,915	$ 1,726,080
Total, Fair Value	$ 1,653,167	$ 1,604,570