Note 8 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Due in one year or less, Amortized Cost	$ 355,228
Due in one year or less, Fair Value	353,895
Due after one year through five years, Amortized Cost	239,805
Due after one year through five years, Fair Value	224,105
Due after five years through ten years, Amortized Cost	165,000
Due after five years through ten years, Fair Value	154,597
Due after ten years, Amortized Cost	869,324
Due after ten years, Fair Value	754,724
Total, Amortized Cost	1,629,357	$ 1,622,173
Total, Fair Value	$ 1,487,321	$ 1,473,348