Note 10 - Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Balance, January 1, 2018	$ 366,500	$ 333,644
Net current period other comprehensive income gain (loss)	2,629	(3,408)
Reclassification adjustment for adoption of ASU 2018-02
Balance, March 31, 2018	377,994	337,702
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance, January 1, 2018	(5,330)	(1,781)
Net current period other comprehensive income gain (loss)	2,794	(3,718)
Reclassification adjustment for adoption of ASU 2018-02		(496)
Balance, March 31, 2018	(2,536)	(5,995)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance, January 1, 2018	408	193
Net current period other comprehensive income gain (loss)	(174)	310
Reclassification adjustment for adoption of ASU 2018-02		41
Balance, March 31, 2018	234	544
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, January 1, 2018	(220)	(342)
Net current period other comprehensive income gain (loss)	9
Reclassification adjustment for adoption of ASU 2018-02		(51)
Balance, March 31, 2018	(211)	(393)
AOCI Attributable to Parent [Member]
Balance, January 1, 2018	(5,142)	(1,930)
Net current period other comprehensive income gain (loss)	2,629	(3,408)
Reclassification adjustment for adoption of ASU 2018-02		(506)
Balance, March 31, 2018	$ (2,513)	$ (5,844)