Note 4 - Securities - Fair Value and Associated Unrealized Losses on Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale securities, less than 12 months, fair value	$ 105,042	$ 54,959
Available-for-sale securities, less than 12 months, unrealized losses	(2,258)	(515)
Available-for-sale securities, fair value	113,345	64,836
Available-for-sale securities, unrealized losses	(2,508)	(748)
Available-for-sale securities, 12 months or more, fair value	8,303	9,877
Available-for-sale securities, 12 months or more, unrealized losses	(250)	(233)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	20,329	7,682
Available-for-sale securities, less than 12 months, unrealized losses	(420)	(39)
Available-for-sale securities, fair value	20,329	7,682
Available-for-sale securities, unrealized losses	(420)	(39)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Held-to-maturity securities, less than 12 months, fair value	11,639	1,513
Held-to-maturity securities, less than 12 months, unrealized losses	(425)	(63)
Held-to-maturity securities, 12 months or more, fair value	933	4,831
Held-to-maturity securities, 12 months or more, unrealized losses	(98)	(157)
Held-to-maturity securities, fair value	12,572	6,344
Held-to-maturity securities, unrealized losses	(523)	(220)
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Available-for-sale securities, less than 12 months, fair value	52,345	16,279
Available-for-sale securities, less than 12 months, unrealized losses	(1,396)	(210)
Available-for-sale securities, fair value	56,453	21,210
Available-for-sale securities, unrealized losses	(1,497)	(270)
Available-for-sale securities, 12 months or more, fair value	4,108	4,931
Available-for-sale securities, 12 months or more, unrealized losses	(101)	(60)
Corporate Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	8,908	18,707
Available-for-sale securities, less than 12 months, unrealized losses	(140)	(191)
Available-for-sale securities, fair value	8,908	18,707
Available-for-sale securities, unrealized losses	(140)	(191)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Commercial Mortgage Backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value	12,041	7,557
Available-for-sale securities, less than 12 months, unrealized losses	(191)	(62)
Available-for-sale securities, fair value	14,890	9,073
Available-for-sale securities, unrealized losses	(281)	(134)
Available-for-sale securities, 12 months or more, fair value	2,849	1,516
Available-for-sale securities, 12 months or more, unrealized losses	(90)	(72)
Asset-backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value	11,419	4,734
Available-for-sale securities, less than 12 months, unrealized losses	(111)	(13)
Available-for-sale securities, fair value	12,765	8,164
Available-for-sale securities, unrealized losses	(170)	(114)
Available-for-sale securities, 12 months or more, fair value	1,346	3,430
Available-for-sale securities, 12 months or more, unrealized losses	$ (59)	$ (101)