Note 3 - Securities - Available-for-sale Securities (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Amortized cost	$ 347,795,000	$ 341,948,000
Securities available for sale, gross unrealized gains	928,000	1,355,000
Securities available for sale, gross unrealized losses	(11,357,000)	(7,559,000)
Fair value	337,366,000	335,744,000
US Government Agencies Debt Securities [Member]
Amortized cost	196,109,000	175,953,000
Securities available for sale, gross unrealized gains	310,000	99,000
Securities available for sale, gross unrealized losses	(9,342,000)	(6,352,000)
Fair value	187,077,000	169,700,000
Collateralized Mortgage Backed Securities [Member]
Amortized cost	44,263,000	38,967,000
Securities available for sale, gross unrealized gains	187,000	335,000
Securities available for sale, gross unrealized losses	(792,000)	(510,000)
Fair value	43,658,000	38,792,000
Municipal General Obligation Bonds [Member]
Amortized cost	103,235,000	121,040,000
Securities available for sale, gross unrealized gains	427,000	891,000
Securities available for sale, gross unrealized losses	(1,165,000)	(638,000)
Fair value	102,497,000	121,293,000
Municipal Revenue Bonds [Member]
Amortized cost	3,688,000	3,978,000
Securities available for sale, gross unrealized gains	4,000	30,000
Securities available for sale, gross unrealized losses	(58,000)	(30,000)
Fair value	3,634,000	3,978,000
Other Debt and Equity Securities [Member]
Amortized cost	500,000	2,010,000
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	0	(29,000)
Fair value	$ 500,000	$ 1,981,000