Note 13 - Employee Benefit Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Requisite Service Period (Year)	3 years
Defined Benefit Plan, Accumulated Benefit Obligation	$ 13,600,000	$ 12,300,000
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	$ 293,000
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	20.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 260,000	266,000
Liability, Defined Benefit Plan, Total	2,000,000	1,900,000
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total	205,000	224,000
Board of Directors [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 143,000	$ 140,000