Note 3 - Revenue - Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total Revenue from Contracts with Customers	$ 1,261,034	$ 879,462	$ 1,375,559
Domestic Coal Revenue [Member]
Total Revenue from Contracts with Customers	590,941	506,554	822,389
Export Coal Revenue [Member]
Total Revenue from Contracts with Customers	501,081	266,108	466,140
Terminal Revenue [Member]
Total Revenue from Contracts with Customers	65,193	66,810	67,363
Freight Revenue [Member]
Total Revenue from Contracts with Customers	$ 103,819	$ 39,990	$ 19,667