Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 91,866,000	$ 193,930,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	7,604,000	17,438,000
Securities available for sale, continuous unrealized loss position, 12 months or more	468,191,000	379,216,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	64,923,000	65,843,000
Securities available for sale, continuous unrealized loss position	560,057,000	573,146,000
Securities available for sale, continuous unrealized loss position, unrealized loss	72,527,000	83,281,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	14,000,000	53,019,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	755,000	5,713,000
Securities available for sale, continuous unrealized loss position, 12 months or more	382,220,000	335,725,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	57,025,000	59,379,000
Securities available for sale, continuous unrealized loss position	396,220,000	388,744,000
Securities available for sale, continuous unrealized loss position, unrealized loss	57,780,000	65,092,000
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	29,016,000	31,127,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	5,508,000	6,068,000
Securities available for sale, continuous unrealized loss position, 12 months or more	1,742,000	12,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	88,000	0
Securities available for sale, continuous unrealized loss position	30,758,000	31,139,000
Securities available for sale, continuous unrealized loss position, unrealized loss	5,596,000	6,068,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	43,446,000	97,252,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	940,000	4,516,000
Securities available for sale, continuous unrealized loss position, 12 months or more	67,822,000	32,870,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	5,791,000	4,542,000
Securities available for sale, continuous unrealized loss position	111,268,000	130,122,000
Securities available for sale, continuous unrealized loss position, unrealized loss	6,731,000	9,058,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	5,404,000	12,532,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	401,000	1,141,000
Securities available for sale, continuous unrealized loss position, 12 months or more	16,407,000	10,609,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	2,019,000	1,922,000
Securities available for sale, continuous unrealized loss position	21,811,000	23,141,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 2,420,000	$ 3,063,000