Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 192,224,000	$ 183,125,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	8,149,000	8,655,000
Securities available for sale, continuous unrealized loss position, 12 months or more	28,411,000	70,085,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	437,000	774,000
Securities available for sale, continuous unrealized loss position	220,635,000	253,210,000
Securities available for sale, continuous unrealized loss position, unrealized loss	8,586,000	9,429,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	123,657,000	110,160,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	6,850,000	7,172,000
Securities available for sale, continuous unrealized loss position, 12 months or more	4,108,000	5,073,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	135,000	165,000
Securities available for sale, continuous unrealized loss position	127,765,000	115,233,000
Securities available for sale, continuous unrealized loss position, unrealized loss	6,985,000	7,337,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	19,107,000	3,670,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	145,000	4,000
Securities available for sale, continuous unrealized loss position, 12 months or more	15,498,000	37,072,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	148,000	419,000
Securities available for sale, continuous unrealized loss position	34,605,000	40,742,000
Securities available for sale, continuous unrealized loss position, unrealized loss	293,000	423,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	46,728,000	65,895,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	1,047,000	1,360,000
Securities available for sale, continuous unrealized loss position, 12 months or more	8,805,000	27,734,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	154,000	189,000
Securities available for sale, continuous unrealized loss position	55,533,000	93,629,000
Securities available for sale, continuous unrealized loss position, unrealized loss	1,201,000	1,549,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	1,246,000	1,921,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	78,000	90,000
Securities available for sale, continuous unrealized loss position, 12 months or more	0	206,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	0	1,000
Securities available for sale, continuous unrealized loss position	1,246,000	2,127,000
Securities available for sale, continuous unrealized loss position, unrealized loss	78,000	91,000
Other Debt and Equity Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	1,486,000	1,479,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	29,000	29,000
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	1,486,000	1,479,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 29,000	$ 29,000