Note 5 - Debt Securities - Summary of Volume of State and Political Subdivision Securities Held in Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt securities, available for sale, amortized cost	$ 532,250	$ 541,196
Available for sale securities, unrealized gains	591	1,534
Available for sale securities, unrealized losses	42,570	39,968
Debt securities available for sale (at fair value)	490,271	$ 502,762	[1]
CALIFORNIA
Debt securities, available for sale, amortized cost	43,888
Available for sale securities, unrealized gains	0
Available for sale securities, unrealized losses	8,389
Debt securities available for sale (at fair value)	35,499
TEXAS
Debt securities, available for sale, amortized cost	27,926
Available for sale securities, unrealized gains	28
Available for sale securities, unrealized losses	3,733
Debt securities available for sale (at fair value)	24,221
OREGON
Debt securities, available for sale, amortized cost	16,283
Available for sale securities, unrealized gains	0
Available for sale securities, unrealized losses	2,938
Debt securities available for sale (at fair value)	13,345
MICHIGAN
Debt securities, available for sale, amortized cost	14,502
Available for sale securities, unrealized gains	0
Available for sale securities, unrealized losses	1,616
Debt securities available for sale (at fair value)	12,886
PENNSYLVANIA
Debt securities, available for sale, amortized cost	10,662
Available for sale securities, unrealized gains	7
Available for sale securities, unrealized losses	1,273
Debt securities available for sale (at fair value)	$ 9,396

[1] Derived from audited consolidated financial statements.