Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 119,073,000	$ 32,243,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	899,000	395,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	85,330,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	859,000
Securities available for sale, continuous unrealized loss position	119,073,000	117,573,000
Securities available for sale, continuous unrealized loss position, unrealized loss	899,000	1,254,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	118,650,000	25,650,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	897,000	349,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	73,913,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	793,000
Securities available for sale, continuous unrealized loss position	118,650,000	99,563,000
Securities available for sale, continuous unrealized loss position, unrealized loss	897,000	1,142,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	2,838,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	28,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	10,423,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	54,000
Securities available for sale, continuous unrealized loss position	0	13,261,000
Securities available for sale, continuous unrealized loss position, unrealized loss	0	82,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	3,755,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	18,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	994,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	12,000
Securities available for sale, continuous unrealized loss position	0	4,749,000
Securities available for sale, continuous unrealized loss position, unrealized loss	0	30,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	423,000	0
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	2,000	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	423,000	0
Securities available for sale, continuous unrealized loss position, unrealized loss	2,000	0
Other Debt and Equity Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	0
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	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	0	0
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 0	$ 0