Note 5 - Debt Securities - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Due in one year or less, amortized cost	$ 61,455
Due in one year or less, estimated fair value	59,934
Due from one to five years, amortized cost	161,414
Due from one to five years, estimated fair value	156,157
Due from five to ten years, amortized cost	112,930
Due from five to ten years, estimated fair value	105,048
Due after ten years, amortized cost	205,397
Due after ten years, estimated fair value	181,623
Total amortized cost	541,196	$ 455,067
Total estimated fair value	$ 502,762	$ 405,201