Note 7 - Other Comprehensive Income - Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Balance	$ 313,872	$ 286,519
Other comprehensive income, net of tax	774	3,314
Balance	319,687	296,323
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(1,211)	965
Other comprehensive income, net of tax	689	3,653
Balance	(522)	4,618
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance	(16)	(60)
Other comprehensive income, net of tax	85	(339)
Balance	69	(399)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(272)	(273)
Other comprehensive income, net of tax
Balance	(272)	(273)
AOCI Attributable to Parent [Member]
Balance	(1,499)	632
Other comprehensive income, net of tax	774	3,314
Balance	$ (725)	$ 3,946