Note 2 - Major Transactions (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income (Loss) From Sale of Contracts	$ 17,847	$ 0	$ 17,847	$ 0
Gain (Loss) on Disposition of Assets, Total			15,241	$ 1,986
Settlement Transaction with Murray Energy [Member]
Income (Loss) From Sale of Contracts	18,561
Gain (Loss) on Disposition of Assets, Total	6,230
Income (Loss) From Expense Rebates Offset With Cure Costs	1,940
Other Receivables	8,088		8,088		$ 13,567
Other Assets, Total	$ 21,326		$ 21,326