Note 5 - Debt Securities - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Due in one year or less, amortized cost	$ 61,182
Due in one year or less, estimated fair value	59,324
Due from one to five years, amortized cost	155,429
Due from one to five years, estimated fair value	149,212
Due from five to ten years, amortized cost	113,695
Due from five to ten years, estimated fair value	104,397
Due after ten years, amortized cost	201,944
Due after ten years, estimated fair value	177,338
Total amortized cost	532,250	$ 541,196
Total estimated fair value	$ 490,271	$ 502,762	[1]

[1] Derived from audited consolidated financial statements.