Note 7 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Due in one year or less, Amortized Cost	$ 65,472
Due in one year or less, Fair Value	65,511
Due after one year through five years, Amortized Cost	71,862
Due after one year through five years, Fair Value	71,254
Due after five years through ten years, Amortized Cost	161,771
Due after five years through ten years, Fair Value	166,473
Due after ten years, Amortized Cost	692,619
Due after ten years, Fair Value	699,277
Total, Amortized Cost	991,724	$ 1,019,230
Total, Fair Value	$ 1,002,515	$ 1,036,550