Note 12 - Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance	$ 313,872	$ 286,519	$ 259,895
Other comprehensive (loss) income	(431)	(2,131)	(1,453)
Balance	333,644	313,872	286,519
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(1,211)	965	2,456
Other comprehensive (loss) income before reclassifications	(721)	(2,176)	(1,558)
Amounts reclassified from accumulated other comprehensive income	151		67
Other comprehensive (loss) income	(1,067)	(2,176)	(1,491)
Balance	(2,278)	(1,211)	965
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance	(16)	(60)	16
Other comprehensive (loss) income before reclassifications	209	44	(76)
Amounts reclassified from accumulated other comprehensive income
Other comprehensive (loss) income	250	44	(76)
Balance	234	(16)	(60)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(272)	(273)	(387)
Other comprehensive (loss) income before reclassifications	(70)	1	114
Amounts reclassified from accumulated other comprehensive income
Other comprehensive (loss) income	(120)	1	114
Balance	(392)	(272)	(273)
Disproportionate Tax Effect [Member]
Balance	(1,499)	632	2,085
Other comprehensive (loss) income before reclassifications	(582)	(2,131)	(1,520)
Amounts reclassified from accumulated other comprehensive income	151		67
Other comprehensive (loss) income	(431)	(2,131)	(1,453)
Balance	$ (1,930)	$ (1,499)	$ 632