Note 2 - Securities - Available-for-sale Securities (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Securities available for sale, amortized cost	$ 686,841,000	$ 685,646,000
Securities available for sale, gross unrealized gains	625,000	571,000
Securities available for sale, gross unrealized losses	(78,494,000)	(83,281,000)
Securities available for sale, fair value	608,972,000	602,936,000
US Government Agencies Debt Securities [Member]
Securities available for sale, amortized cost	454,164,000	453,836,000
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	(61,070,000)	(65,092,000)
Securities available for sale, fair value	393,094,000	388,744,000
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale, amortized cost	36,374,000	38,002,000
Securities available for sale, gross unrealized gains	10,000	19,000
Securities available for sale, gross unrealized losses	(5,864,000)	(6,068,000)
Securities available for sale, fair value	30,520,000	31,953,000
Municipal General Obligation Bonds [Member]
Securities available for sale, amortized cost	165,793,000	163,041,000
Securities available for sale, gross unrealized gains	511,000	450,000
Securities available for sale, gross unrealized losses	(8,739,000)	(9,058,000)
Securities available for sale, fair value	157,565,000	154,433,000
Municipal Revenue Bonds [Member]
Securities available for sale, amortized cost	30,010,000	30,267,000
Securities available for sale, gross unrealized gains	104,000	102,000
Securities available for sale, gross unrealized losses	(2,821,000)	(3,063,000)
Securities available for sale, fair value	27,293,000	27,306,000
Other Debt and Equity Securities [Member]
Securities available for sale, amortized cost	500,000	500,000
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	0	0
Securities available for sale, fair value	$ 500,000	$ 500,000