Note 3 - Securities - Available-for-sale Securities (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Amortized cost	$ 329,979,000	$ 347,795,000
Securities available for sale, gross unrealized gains	5,930,000	928,000
Securities available for sale, gross unrealized losses	(1,254,000)	(11,357,000)
Fair value	334,655,000	337,366,000
US Government Agencies Debt Securities [Member]
Amortized cost	185,103,000	196,109,000
Securities available for sale, gross unrealized gains	2,449,000	310,000
Securities available for sale, gross unrealized losses	(1,142,000)	(9,342,000)
Fair value	186,410,000	187,077,000
Collateralized Mortgage Backed Securities [Member]
Amortized cost	41,998,000	44,263,000
Securities available for sale, gross unrealized gains	554,000	187,000
Securities available for sale, gross unrealized losses	(82,000)	(792,000)
Fair value	42,470,000	43,658,000
Municipal General Obligation Bonds [Member]
Amortized cost	98,245,000	103,235,000
Securities available for sale, gross unrealized gains	2,864,000	427,000
Securities available for sale, gross unrealized losses	(30,000)	(1,165,000)
Fair value	101,079,000	102,497,000
Municipal Revenue Bonds [Member]
Amortized cost	4,133,000	3,688,000
Securities available for sale, gross unrealized gains	63,000	4,000
Securities available for sale, gross unrealized losses	0	(58,000)
Fair value	4,196,000	3,634,000
Other Debt and Equity Securities [Member]
Amortized cost	500,000	500,000
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	0	0
Fair value	$ 500,000	$ 500,000