Note 9 - Other Comprehensive Income - Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Balance	$ 333,644		$ 313,872
Other comprehensive income, net of tax	(3,408)		774
Adoption of Accounting Standards Update 2018-02	(506)
Balance	337,702		319,687
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(1,781)	[1]	(1,211)
Other comprehensive income, net of tax	(3,718)		689
Adoption of Accounting Standards Update 2018-02	(496)
Balance	(5,995)		(522)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance	193	[1]	(16)
Other comprehensive income, net of tax	310		85
Adoption of Accounting Standards Update 2018-02	41
Balance	544		69
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(342)	[1]	(272)
Other comprehensive income, net of tax
Adoption of Accounting Standards Update 2018-02	(51)
Balance	(393)		(272)
Disproportionate Tax Effect [Member]
Balance	(1,930)	[1]	(1,499)
Other comprehensive income, net of tax	(3,408)		774
Adoption of Accounting Standards Update 2018-02	(506)
Balance	$ (5,844)		$ (725)

[1] December 31, 2017 AOCI component balances reflect a correction of incorrectly reported year-end balances in Note 12 of the 2017 Form 10-K, which were presented as $(2,278), $234, and $(392) for securities available-for-sale, cash flow hedges, and minimum pension liability, respectively.