Note 4 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Due in one year or less, Amortized Cost	$ 935,275
Due in one year or less, Fair Value	934,634
Due after one year through five years, Amortized Cost	15,297
Due after one year through five years, Fair Value	15,297
Due after five years through ten years, Amortized Cost	1,510
Due after five years through ten years, Fair Value	1,295
Due after ten years, Amortized Cost	705,801
Due after ten years, Fair Value	637,810
Total, amortized cost	1,657,883	$ 1,735,451
Total, fair value	$ 1,589,036	$ 1,658,223