Note 8 - Benefit Plans - Actual and Target Pension Plan Asset Allocation (Details)	Dec. 31, 2020	Dec. 31, 2019
Percentage of plan assets	100.00%	100.00%
Target allocation	100.00%
Equity Securities [Member]
Percentage of plan assets	0.00%	68.00%
Target allocation	60.00%
Fixed Income Investments [Member]
Percentage of plan assets	40.00%	31.00%
Target allocation	40.00%
Money Market Funds [Member]
Percentage of plan assets	60.00%	0.00%
Target allocation	0.00%
Other than Securities Investment [Member]
Percentage of plan assets	0.00%	1.00%
Target allocation	0.00%