Note 10 - Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance	$ 389,365	$ 377,994	$ 366,500	$ 345,515	$ 337,702	$ 333,644	$ 366,500	$ 333,644
Net current period other comprehensive income gain (loss)	662	3,579	2,629	(1,592)	(1,200)	(3,408)	6,870	(6,200)
Balance	396,111	389,365	377,994	352,980	345,515	337,702	396,111	352,980
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	1,291		(5,330)	(7,274)		(1,781)	(5,330)	(1,781)
Net current period other comprehensive income gain (loss)	719			(1,632)			7,340	(6,629)
Balance	2,010	1,291		(8,906)	(7,274)		2,010	(8,906)
Reclassification adjustment for adoption of ASU 2018-02								(496)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance	(14)		408	623		193	408	193
Net current period other comprehensive income gain (loss)	(55)			40			(477)	429
Balance	(69)	(14)		663	623		(69)	663
Reclassification adjustment for adoption of ASU 2018-02								41
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(211)		(220)	(393)		(342)	(220)	(342)
Net current period other comprehensive income gain (loss)	(2)			0			7	0
Balance	(213)	(211)		(393)	(393)		(213)	(393)
Reclassification adjustment for adoption of ASU 2018-02								(51)
AOCI Attributable to Parent [Member]
Balance	1,066	(2,513)	(5,142)	(7,044)	(5,844)	(1,930)	(5,142)	(1,930)
Net current period other comprehensive income gain (loss)	662	3,579	2,629	(1,592)	(1,200)	(3,408)	6,870	(6,200)
Balance	$ 1,728	$ 1,066	$ (2,513)	$ (8,636)	$ (7,044)	$ (5,844)	$ 1,728	(8,636)
Reclassification adjustment for adoption of ASU 2018-02								$ (506)