Note 5 - Securities - Securities Available-for-sale (Details) - USD ($)
Sep. 30, 2016
Dec. 31, 2015
US Government Agencies Debt Securities [Member]    
Securities available-for-sale, Amortized Costs $ 268,925,000 $ 216,897,000
Securities available-for-sale, Gross Unrealized Gains 2,038,000 519,000
Securities available-for-sale, Gross Unrealized Losses 253,000 4,952,000
Securities available-for-sale, Fair Values 270,710,000 212,464,000
US States and Political Subdivisions Debt Securities [Member]    
Securities available-for-sale, Amortized Costs 12,572,000 15,934,000
Securities available-for-sale, Gross Unrealized Gains 352,000 541,000
Securities available-for-sale, Gross Unrealized Losses 0 0
Securities available-for-sale, Fair Values 12,924,000 16,475,000
Collateralized Mortgage Backed Securities [Member]    
Securities available-for-sale, Amortized Costs 932,000 1,199,000
Securities available-for-sale, Gross Unrealized Gains 103,000 120,000
Securities available-for-sale, Gross Unrealized Losses 0 0
Securities available-for-sale, Fair Values 1,035,000 1,319,000
Corporate Debt Securities [Member]    
Securities available-for-sale, Amortized Costs 6,016,000 6,015,000
Securities available-for-sale, Gross Unrealized Gains 440,000 22,000
Securities available-for-sale, Gross Unrealized Losses 291,000
Securities available-for-sale, Fair Values 6,456,000 5,746,000
Other Securities [Member]    
Securities available-for-sale, Amortized Costs 189,000 189,000
Securities available-for-sale, Gross Unrealized Gains 0 0
Securities available-for-sale, Gross Unrealized Losses 37,000 62,000
Securities available-for-sale, Fair Values 152,000 127,000
Securities available-for-sale, Amortized Costs 288,634,000 240,234,000
Securities available-for-sale, Gross Unrealized Gains 2,933,000 1,202,000
Securities available-for-sale, Gross Unrealized Losses 290,000 5,305,000
Securities available-for-sale, Fair Values $ 291,277,000 $ 236,131,000