Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 68,756,000	$ 193,930,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	12,717,000	17,438,000
Securities available for sale, continuous unrealized loss position, 12 months or more	516,942,000	379,216,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	80,482,000	65,843,000
Securities available for sale, continuous unrealized loss position	585,698,000	573,146,000
Securities available for sale, continuous unrealized loss position, unrealized loss	93,199,000	83,281,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	2,679,000	53,019,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,124,000	5,713,000
Securities available for sale, continuous unrealized loss position, 12 months or more	381,400,000	335,725,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	67,127,000	59,379,000
Securities available for sale, continuous unrealized loss position	384,079,000	388,744,000
Securities available for sale, continuous unrealized loss position, unrealized loss	68,251,000	65,092,000
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	26,231,000	31,127,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	7,558,000	6,068,000
Securities available for sale, continuous unrealized loss position, 12 months or more	1,604,000	12,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	127,000	0
Securities available for sale, continuous unrealized loss position	27,835,000	31,139,000
Securities available for sale, continuous unrealized loss position, unrealized loss	7,685,000	6,068,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	33,136,000	97,252,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	2,992,000	4,516,000
Securities available for sale, continuous unrealized loss position, 12 months or more	115,872,000	32,870,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	10,538,000	4,542,000
Securities available for sale, continuous unrealized loss position	149,008,000	130,122,000
Securities available for sale, continuous unrealized loss position, unrealized loss	13,530,000	9,058,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	6,710,000	12,532,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,043,000	1,141,000
Securities available for sale, continuous unrealized loss position, 12 months or more	18,066,000	10,609,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	2,690,000	1,922,000
Securities available for sale, continuous unrealized loss position	24,776,000	23,141,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 3,733,000	$ 3,063,000