Note 8 - Components of Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Income (Loss) (Details) (Parentheticals) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Unrealized holding gain (loss) on available for sale securities, tax	$ 1,028,000	$ 1,209
Reclassification adjustment for gain included in net income, taxes	(4,000)	(3,000)
Reclassification adjustment for gain included in net income, taxes	(4,000)	(3,000)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Unrealized holding gain (loss) on available for sale securities, tax	0
Reclassification adjustment for gain included in net income, taxes	0	0
Reclassification adjustment for gain included in net income, taxes	0	0
AOCI Attributable to Parent [Member]
Unrealized holding gain (loss) on available for sale securities, tax	1,028,000	1,209
Reclassification adjustment for gain included in net income, taxes	(4,000)	(3,000)
Reclassification adjustment for gain included in net income, taxes	$ (4,000)	$ (3,000)