Note 2 - Securities - Available-for-sale Securities (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Securities available for sale, amortized cost	$ 663,977,000	$ 597,463,000
Securities available for sale, gross unrealized gains	264,000	5,238,000
Securities available for sale, gross unrealized losses	(60,603,000)	(9,958,000)
Securities available for sale, fair value	603,638,000	592,743,000
US Government Agencies Debt Securities [Member]
Securities available for sale, amortized cost	453,512,000	398,874,000
Securities available for sale, gross unrealized gains	0	266,000
Securities available for sale, gross unrealized losses	(46,177,000)	(8,769,000)
Securities available for sale, fair value	407,335,000	390,371,000
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale, amortized cost	40,676,000	41,906,000
Securities available for sale, gross unrealized gains	56,000	549,000
Securities available for sale, gross unrealized losses	(4,368,000)	(652,000)
Securities available for sale, fair value	36,364,000	41,803,000
Municipal General Obligation Bonds [Member]
Securities available for sale, amortized cost	145,002,000	133,894,000
Securities available for sale, gross unrealized gains	190,000	4,092,000
Securities available for sale, gross unrealized losses	(7,519,000)	(392,000)
Securities available for sale, fair value	137,673,000	137,594,000
Municipal Revenue Bonds [Member]
Securities available for sale, amortized cost	24,287,000	22,289,000
Securities available for sale, gross unrealized gains	18,000	331,000
Securities available for sale, gross unrealized losses	(2,539,000)	(145,000)
Securities available for sale, fair value	21,766,000	22,475,000
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