Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 17,478,000	$ 72,791,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	374,000	1,582,000
Securities available for sale, continuous unrealized loss position, 12 months or more	74,296,000	205,540,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	723,000	9,775,000
Securities available for sale, continuous unrealized loss position	91,774,000	278,331,000
Securities available for sale, continuous unrealized loss position, unrealized loss	1,097,000	11,357,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	15,630,000	31,220,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	370,000	1,136,000
Securities available for sale, continuous unrealized loss position, 12 months or more	53,935,000	136,445,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	588,000	8,206,000
Securities available for sale, continuous unrealized loss position	69,565,000	167,665,000
Securities available for sale, continuous unrealized loss position, unrealized loss	958,000	9,342,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	11,460,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	136,000
Securities available for sale, continuous unrealized loss position, 12 months or more	17,049,000	23,762,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	116,000	656,000
Securities available for sale, continuous unrealized loss position	17,049,000	35,222,000
Securities available for sale, continuous unrealized loss position, unrealized loss	116,000	792,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	1,848,000	28,923,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	4,000	299,000
Securities available for sale, continuous unrealized loss position, 12 months or more	2,758,000	43,961,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	18,000	866,000
Securities available for sale, continuous unrealized loss position	4,606,000	72,884,000
Securities available for sale, continuous unrealized loss position, unrealized loss	22,000	1,165,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	1,188,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	11,000
Securities available for sale, continuous unrealized loss position, 12 months or more	554,000	1,372,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	1,000	47,000
Securities available for sale, continuous unrealized loss position	554,000	2,560,000
Securities available for sale, continuous unrealized loss position, unrealized loss	1,000	58,000
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