Note 4 - Securities - Fair Value and Associated Unrealized Losses on Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale securities, fair value	$ 99,001	$ 113,345
Available-for-sale securities, unrealized losses	(1,224)	(2,508)
Available-for-sale securities, less than 12 months, fair value	85,199	105,042
Available-for-sale securities, less than 12 months, unrealized losses	(897)	(2,258)
Available-for-sale securities, 12 months or more, fair value	13,802	8,303
Available-for-sale securities, 12 months or more, unrealized losses	(327)	(250)
US Government Agencies Debt Securities [Member]
Available-for-sale securities, fair value	8,259	9,139
Available-for-sale securities, unrealized losses	(59)	(83)
Available-for-sale securities, less than 12 months, fair value	8,259	9,139
Available-for-sale securities, less than 12 months, unrealized losses	(59)	(83)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, fair value	10,757	20,329
Available-for-sale securities, unrealized losses	(106)	(420)
Held-to-maturity securities, less than 12 months, fair value	2,037	11,639
Held-to-maturity securities, less than 12 months, unrealized losses	(25)	(425)
Held-to-maturity securities, 12 months or more, fair value	989	933
Held-to-maturity securities, 12 months or more, unrealized losses	(42)	(98)
Held-to-maturity securities, fair value	3,026	12,572
Held-to-maturity securities, unrealized losses	(67)	(523)
Available-for-sale securities, less than 12 months, fair value	10,757	20,329
Available-for-sale securities, less than 12 months, unrealized losses	(106)	(420)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Available-for-sale securities, fair value	53,322	56,453
Available-for-sale securities, unrealized losses	(711)	(1,497)
Available-for-sale securities, less than 12 months, fair value	45,078	52,345
Available-for-sale securities, less than 12 months, unrealized losses	(529)	(1,396)
Available-for-sale securities, 12 months or more, fair value	8,244	4,108
Available-for-sale securities, 12 months or more, unrealized losses	(182)	(101)
Corporate Debt Securities [Member]
Available-for-sale securities, fair value	2,959	8,908
Available-for-sale securities, unrealized losses	(88)	(140)
Available-for-sale securities, less than 12 months, fair value	2,959	8,908
Available-for-sale securities, less than 12 months, unrealized losses	(88)	(140)
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, fair value	20,287	14,890
Available-for-sale securities, unrealized losses	(185)	(281)
Available-for-sale securities, less than 12 months, fair value	15,996	12,041
Available-for-sale securities, less than 12 months, unrealized losses	(94)	(191)
Available-for-sale securities, 12 months or more, fair value	4,291	2,849
Available-for-sale securities, 12 months or more, unrealized losses	(91)	(90)
Asset-backed Securities [Member]
Available-for-sale securities, fair value	3,417	3,626
Available-for-sale securities, unrealized losses	(75)	(87)
Available-for-sale securities, less than 12 months, fair value	2,150	2,280
Available-for-sale securities, less than 12 months, unrealized losses	(21)	(28)
Available-for-sale securities, 12 months or more, fair value	1,267	1,346
Available-for-sale securities, 12 months or more, unrealized losses	$ (54)	$ (59)