Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 4,159,000	$ 72,791,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	3,000	1,582,000
Securities available for sale, continuous unrealized loss position, 12 months or more	220,427,000	205,540,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	7,860,000	9,775,000
Securities available for sale, continuous unrealized loss position	224,586,000	278,331,000
Securities available for sale, continuous unrealized loss position, unrealized loss	7,863,000	11,357,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	0	31,220,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	0	1,136,000
Securities available for sale, continuous unrealized loss position, 12 months or more	153,927,000	136,445,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	6,883,000	8,206,000
Securities available for sale, continuous unrealized loss position	153,927,000	167,665,000
Securities available for sale, continuous unrealized loss position, unrealized loss	6,883,000	9,342,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	3,404,000	11,460,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,000	136,000
Securities available for sale, continuous unrealized loss position, 12 months or more	26,840,000	23,762,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	551,000	656,000
Securities available for sale, continuous unrealized loss position	30,244,000	35,222,000
Securities available for sale, continuous unrealized loss position, unrealized loss	552,000	792,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	253,000	28,923,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,000	299,000
Securities available for sale, continuous unrealized loss position, 12 months or more	38,347,000	43,961,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	390,000	866,000
Securities available for sale, continuous unrealized loss position	38,600,000	72,884,000
Securities available for sale, continuous unrealized loss position, unrealized loss	391,000	1,165,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	502,000	1,188,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,000	11,000
Securities available for sale, continuous unrealized loss position, 12 months or more	1,313,000	1,372,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	36,000	47,000
Securities available for sale, continuous unrealized loss position	1,815,000	2,560,000
Securities available for sale, continuous unrealized loss position, unrealized loss	37,000	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