Note 7 - Credit Losses - Impact of ASC 326 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Allowance for Credit Losses on Receivables	$ 1,661	$ 2,811	$ 0
Trade Accounts Receivable [Member]
Allowance for Credit Losses on Receivables	4,426	2,100	2,100
Other Receivables [Member]
Allowance for Credit Losses on Receivables	$ 4,710	711	$ 711
Other Assets [Member]
Allowance for Credit Losses on Receivables		0
Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for Credit Losses on Receivables		7,218
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] | Trade Accounts Receivable [Member]
Allowance for Credit Losses on Receivables		3,051
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] | Other Receivables [Member]
Allowance for Credit Losses on Receivables		3,372
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] | Other Assets [Member]
Allowance for Credit Losses on Receivables		795
Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for Credit Losses on Receivables		4,407
Cumulative Effect, Period of Adoption, Adjustment [Member] | Trade Accounts Receivable [Member]
Allowance for Credit Losses on Receivables		951
Cumulative Effect, Period of Adoption, Adjustment [Member] | Other Receivables [Member]
Allowance for Credit Losses on Receivables		2,661
Cumulative Effect, Period of Adoption, Adjustment [Member] | Other Assets [Member]
Allowance for Credit Losses on Receivables		$ 795