Note 8 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Due in one year or less, Amortized Cost	$ 442,957
Due in one year or less, Fair Value	442,208
Due after one year through five years, Amortized Cost	241,407
Due after one year through five years, Fair Value	225,644
Due after five years through ten years, Amortized Cost	154,327
Due after five years through ten years, Fair Value	142,157
Due after ten years, Amortized Cost	846,260
Due after ten years, Fair Value	698,789
Total, Amortized Cost	1,684,951	$ 1,622,173
Total, Fair Value	$ 1,508,798	$ 1,473,348