Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 262,853,000	$ 119,073,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	8,331,000	899,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	0
Securities available for sale, continuous unrealized loss position	262,853,000	119,073,000
Securities available for sale, continuous unrealized loss position, unrealized loss	8,331,000	899,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	234,832,000	118,650,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	7,572,000	897,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	0
Securities available for sale, continuous unrealized loss position	234,832,000	118,650,000
Securities available for sale, continuous unrealized loss position, unrealized loss	7,572,000	897,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	7,264,000	0
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	328,000	0
Securities available for sale, continuous unrealized loss position, 12 months or more	0	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	0
Securities available for sale, continuous unrealized loss position	7,264,000	0
Securities available for sale, continuous unrealized loss position, unrealized loss	328,000	0
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	13,961,000	0
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	274,000	0
Securities available for sale, continuous unrealized loss position, 12 months or more	0	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	0
Securities available for sale, continuous unrealized loss position	13,961,000	0
Securities available for sale, continuous unrealized loss position, unrealized loss	274,000	0
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	6,796,000	423,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	157,000	2,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	0
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	0
Securities available for sale, continuous unrealized loss position	6,796,000	423,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 157,000	$ 2,000