Note 7 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Due in one year or less, Amortized Cost	$ 45,215
Due in one year or less, Fair Value	45,234
Due after one year through five years, Amortized Cost	117,088
Due after one year through five years, Fair Value	115,615
Due after five years through ten years, Amortized Cost	149,474
Due after five years through ten years, Fair Value	153,657
Due after ten years, Amortized Cost	761,297
Due after ten years, Fair Value	764,710
Total, Amortized Cost	1,073,074	$ 1,019,230
Total, Fair Value	$ 1,079,216	$ 1,036,550