Note 2 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Securities available for sale, continuous unrealized loss position, less than 12 months	$ 146,824,000	$ 183,125,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	3,920,000	8,655,000
Securities available for sale, continuous unrealized loss position, 12 months or more	10,588,000	70,085,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	112,000	774,000
Securities available for sale, continuous unrealized loss position	157,412,000	253,210,000
Securities available for sale, continuous unrealized loss position, unrealized loss	4,032,000	9,429,000
US Government Agencies Debt Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	108,900,000	110,160,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	3,590,000	7,172,000
Securities available for sale, continuous unrealized loss position, 12 months or more	1,972,000	5,073,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	28,000	165,000
Securities available for sale, continuous unrealized loss position	110,872,000	115,233,000
Securities available for sale, continuous unrealized loss position, unrealized loss	3,618,000	7,337,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	18,835,000	3,670,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	105,000	4,000
Securities available for sale, continuous unrealized loss position, 12 months or more	5,829,000	37,072,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	59,000	419,000
Securities available for sale, continuous unrealized loss position	24,664,000	40,742,000
Securities available for sale, continuous unrealized loss position, unrealized loss	164,000	423,000
Municipal General Obligation Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	16,242,000	65,895,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	196,000	1,360,000
Securities available for sale, continuous unrealized loss position, 12 months or more	2,243,000	27,734,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	12,000	189,000
Securities available for sale, continuous unrealized loss position	18,485,000	93,629,000
Securities available for sale, continuous unrealized loss position, unrealized loss	208,000	1,549,000
Municipal Revenue Bonds [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	1,353,000	1,921,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	8,000	90,000
Securities available for sale, continuous unrealized loss position, 12 months or more	544,000	206,000
Securities available for sale, continuous unrealized loss position, 12 months or more, unrealized loss	13,000	1,000
Securities available for sale, continuous unrealized loss position	1,897,000	2,127,000
Securities available for sale, continuous unrealized loss position, unrealized loss	21,000	91,000
Other Debt and Equity Securities [Member]
Securities available for sale, continuous unrealized loss position, less than 12 months	1,494,000	1,479,000
Securities available for sale, continuous unrealized loss position, less than 12 months, unrealized loss	21,000	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	1,494,000	1,479,000
Securities available for sale, continuous unrealized loss position, unrealized loss	$ 21,000	$ 29,000