Note 4 - Securities - Fair Value and Associated Unrealized Losses on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available-for-sale securities, less than 12 months, fair value	$ 107,311	$ 105,042
Available-for-sale securities, less than 12 months, unrealized losses	(1,890)	(2,258)
Available-for-sale securities, 12 months or more, fair value	14,812	8,303
Available-for-sale securities, 12 months or more, unrealized losses	(402)	(250)
Available-for-sale securities, fair value	122,123	113,345
Available-for-sale securities, unrealized losses	(2,292)	(2,508)
US Government Agencies Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	9,204	9,139
Available-for-sale securities, less than 12 months, unrealized losses	(74)	(83)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Available-for-sale securities, fair value	9,204	9,139
Available-for-sale securities, unrealized losses	(74)	(83)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	15,993	20,329
Available-for-sale securities, less than 12 months, unrealized losses	(270)	(420)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Available-for-sale securities, fair value	15,993	20,329
Available-for-sale securities, unrealized losses	(270)	(420)
Held-to-maturity securities, less than 12 months, fair value	10,824	11,639
Held-to-maturity securities, less than 12 months, unrealized losses	(247)	(425)
Held-to-maturity securities, 12 months or more, fair value	945	933
Held-to-maturity securities, 12 months or more, unrealized losses	(85)	(98)
Held-to-maturity securities, fair value	11,769	12,572
Held-to-maturity securities, unrealized losses	(332)	(523)
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Available-for-sale securities, less than 12 months, fair value	67,189	52,345
Available-for-sale securities, less than 12 months, unrealized losses	(1,273)	(1,396)
Available-for-sale securities, 12 months or more, fair value	7,355	4,108
Available-for-sale securities, 12 months or more, unrealized losses	(196)	(101)
Available-for-sale securities, fair value	74,544	56,453
Available-for-sale securities, unrealized losses	(1,469)	(1,497)
Corporate Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	2,952	8,908
Available-for-sale securities, less than 12 months, unrealized losses	(99)	(140)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Available-for-sale securities, fair value	2,952	8,908
Available-for-sale securities, unrealized losses	(99)	(140)
Commercial Mortgage Backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value	9,793	12,041
Available-for-sale securities, less than 12 months, unrealized losses	(146)	(191)
Available-for-sale securities, 12 months or more, fair value	6,136	2,849
Available-for-sale securities, 12 months or more, unrealized losses	(154)	(90)
Available-for-sale securities, fair value	15,929	14,890
Available-for-sale securities, unrealized losses	(300)	(281)
Asset-backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value	2,180	2,280
Available-for-sale securities, less than 12 months, unrealized losses	(28)	(28)
Available-for-sale securities, 12 months or more, fair value	1,321	1,346
Available-for-sale securities, 12 months or more, unrealized losses	(52)	(59)
Available-for-sale securities, fair value	3,501	3,626
Available-for-sale securities, unrealized losses	$ (80)	$ (87)