Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 293,910,000	$ 351,062,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	18,152,000	6,455,000
Securities available for sale, continuous unrealized loss position, 12 months or more	240,819,000	110,491,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	22,994,000	3,503,000
Securities available for sale, continuous unrealized loss position	534,729,000	461,553,000
Securities available for sale, continuous unrealized loss position, unrealized loss	41,146,000	9,958,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	190,990,000	274,287,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	11,971,000	5,274,000
Securities available for sale, continuous unrealized loss position, 12 months or more	215,783,000	110,053,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	20,025,000	3,495,000
Securities available for sale, continuous unrealized loss position	406,773,000	384,340,000
Securities available for sale, continuous unrealized loss position, unrealized loss	31,996,000	8,769,000
Collateralized Mortgage-Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	26,110,000	23,184,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,783,000	652,000
Securities available for sale, continuous unrealized loss position, 12 months or more	6,594,000	24,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	809,000	0
Securities available for sale, continuous unrealized loss position	32,704,000	23,208,000
Securities available for sale, continuous unrealized loss position, unrealized loss	2,592,000	652,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	63,139,000	40,748,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	3,399,000	392,000
Securities available for sale, continuous unrealized loss position, 12 months or more	12,600,000	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	1,386,000	0
Securities available for sale, continuous unrealized loss position	75,739,000	40,748,000
Securities available for sale, continuous unrealized loss position, unrealized loss	4,785,000	392,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	13,671,000	12,843,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	999,000	137,000
Securities available for sale, continuous unrealized loss position, 12 months or more	5,842,000	414,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	774,000	8,000
Securities available for sale, continuous unrealized loss position	19,513,000	13,257,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 1,773,000	$ 145,000