Note 9 - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance	$ 85,858	$ 80,008
Net current period other comprehensive income (loss)	1,197	873
Balance	87,545	84,257
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	(108)	(1,517)
Other comprehensive income before reclassification	1,259	875
Amounts reclassified from accumulated other comprehensive income (loss)	(62)	(2)
Net current period other comprehensive income (loss)	1,197	873
Balance	1,089	(644)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(5,227)	(4,840)
Other comprehensive income before reclassification
Amounts reclassified from accumulated other comprehensive income (loss)
Net current period other comprehensive income (loss)
Balance	(5,227)	(4,840)
AOCI Attributable to Parent [Member]
Balance	(5,335)	(6,357)
Other comprehensive income before reclassification	1,259	875
Amounts reclassified from accumulated other comprehensive income (loss)	(62)	(2)
Net current period other comprehensive income (loss)	1,197	873
Balance	$ (4,138)	$ (5,484)