Note 2 - Securities - Available-for-sale Securities (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost	$ 332,759,000	$ 336,562,000
Gross Unrealized Gains	2,414,000	927,000
Gross Unrealized Losses	(5,083,000)	(9,429,000)
Fair Value	330,090,000	328,060,000
US Government Agencies Debt Securities [Member]
Amortized Cost	165,551,000	159,271,000
Gross Unrealized Gains	208,000	106,000
Gross Unrealized Losses	(4,591,000)	(7,337,000)
Fair Value	161,168,000	152,040,000
Collateralized Mortgage Backed Securities [Member]
Amortized Cost	39,304,000	47,329,000
Gross Unrealized Gains	405,000	486,000
Gross Unrealized Losses	(214,000)	(423,000)
Fair Value	39,495,000	47,392,000
Municipal General Obligation Bonds [Member]
Amortized Cost	121,803,000	120,284,000
Gross Unrealized Gains	1,750,000	312,000
Gross Unrealized Losses	(243,000)	(1,549,000)
Fair Value	123,310,000	119,047,000
Municipal Revenue Bonds [Member]
Amortized Cost	4,099,000	7,699,000
Gross Unrealized Gains	51,000	23,000
Gross Unrealized Losses	(16,000)	(91,000)
Fair Value	4,134,000	7,631,000
Other Debt and Equity Securities [Member]
Amortized Cost	2,002,000	1,979,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(19,000)	(29,000)
Fair Value	$ 1,983,000	$ 1,950,000