Note 4 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Due in one year or less, Amortized Cost	$ 311,603
Due in one year or less, Fair Value	310,050
Due after one year through five years, Amortized Cost	213,395
Due after one year through five years, Fair Value	196,616
Due after five years through ten years, Amortized Cost	168,767
Due after five years through ten years, Fair Value	159,448
Due after ten years, Amortized Cost	928,408
Due after ten years, Fair Value	807,234
Total, Amortized Cost	1,622,173	$ 1,126,867
Total, Fair Value	$ 1,473,348	$ 1,127,309