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				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Balance	$ 87,545	$ 85,858	$ 82,089	$ 80,008	$ 85,858	$ 80,008
Net current period other comprehensive income (loss)	497	1,197	911	873
Balance	88,544	87,545	84,357	82,089	88,544	84,357
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	1,089	(108)	(644)	(1,517)	(108)	(1,517)
Other comprehensive income before reclassification	937		910		2,196	1,785
Amounts reclassified from accumulated other comprehensive income (loss)	(440)		1		(502)	(1)
Net current period other comprehensive income (loss)	497		911		1,694	1,784
Balance	1,586	1,089	267	(644)	1,586	267
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(5,227)	(5,227)	(4,840)	(4,840)	(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)	(5,227)	(4,840)	(4,840)	(5,227)	(4,840)
AOCI Attributable to Parent [Member]
Balance	(4,138)	(5,335)	(5,484)	(6,357)	(5,335)	(6,357)
Other comprehensive income before reclassification	937		910		2,196	1,785
Amounts reclassified from accumulated other comprehensive income (loss)	(440)		1		(502)	(1)
Net current period other comprehensive income (loss)	497	1,197	911	873	1,694	1,784
Balance	$ (3,641)	$ (4,138)	$ (4,573)	$ (5,484)	$ (3,641)	$ (4,573)