Note 13 - Other Comprehensive Income (Loss) (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Stockholders' Equity Attributable to Parent, Ending Balance		$ 406,297,000	$ 366,500,000	$ 333,644,000		$ 313,872,000
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%	35.00%
Accounting Standards Update 2018-02 [Member]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	$ (506,000)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance		$ 1,085,000	$ (5,330,000)	$ (1,781,000)	[1]	(1,211,000)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			(496,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance		(37,000)	408,000	193,000	[1]	(16,000)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			41,000
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance		$ (371,000)	(220,000)	(342,000)	[1]	$ (272,000)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			$ (51,000)
Previously Reported [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance				(2,278,000)
Previously Reported [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance				234,000
Previously Reported [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance				$ (392,000)

[1] December 31, 2017 AOCI component balances reflect a correction of incorrectly reported year-end balances in the Footnote titled "Other Comprehensive Income (Loss)" of the 2017 Form 10-K, which were presented as $(2,278), $234, and $(392) for securities AFS, cash flow hedges, and minimum pension liability, respectively.