Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 68,002,000	$ 32,243,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	514,000	395,000
Securities available for sale, continuous unrealized loss position, 12 months or more	32,000	85,330,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	1,000	859,000
Securities available for sale, continuous unrealized loss position	68,034,000	117,573,000
Securities available for sale, continuous unrealized loss position, unrealized loss	515,000	1,254,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	67,172,000	25,650,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	497,000	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	67,172,000	99,563,000
Securities available for sale, continuous unrealized loss position, unrealized loss	497,000	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	32,000	10,423,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	1,000	54,000
Securities available for sale, continuous unrealized loss position	32,000	13,261,000
Securities available for sale, continuous unrealized loss position, unrealized loss	1,000	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	830,000	0
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	17,000	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	830,000	0
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 17,000	$ 0