Note 3 - Recently Adopted Accounting Pronouncements - Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Affiliate credit loss impairment expense	$ 0	$ 0	$ 53,581	$ 0
Trade Accounts Receivable [Member]
Balance			70
Affiliate credit loss impairment expense			418
Other			0
Balance	651		651
Trade Accounts Receivable [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance			163
Due from Affiliate [Member]
Balance			20,083
Affiliate credit loss impairment expense			54,550
Other			(1,937)
Balance	$ 72,696		72,696
Due from Affiliate [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance			$ 0