Note 6 - Leases - Lease Terms and Discount Rates for Lease Liabilities (Details)	Sep. 30, 2020	Dec. 31, 2019
Finance leases, weighted-average remaining lease term (Year)	3 years 3 months 7 days	3 years 9 months 14 days
Operating leases, weighted-average remaining lease term (Year)	18 years 2 months 23 days	8 years 3 months 21 days
Finance leases, weighted-average discount rate	5.48%	5.40%
Operating leases, weighted-average discount rate	3.37%	4.50%