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Note 21 - Weighted-average Assumed Healthcare Cost Trend Rates Used to Compute Other Post-retirement Amounts (Details) - Other Postretirement Benefits Plan [Member]
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Weighted Average Assumed Healthcare Cost Trend Rates Used To Compute Other Postretirement Amounts [Line Items]    
Healthcare cost trend 5.33% 5.37%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 3.14% 3.14%
Year that the rate reaches the ultimate trend rate 2039 2038