Note 16 - Segment Information - Industry Segment (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenue		$ 214,292	$ 321,444	$ 610,688	$ 1,049,609
(Loss) Earnings Before Income Tax		(3,442)	9,439	(27,805)	75,914
Segment Assets		2,554,838	2,723,235	2,554,838	2,723,235	$ 2,693,802
Depreciation, Depletion and Amortization		54,959	54,370	156,057	151,245
Capital Expenditures		19,508	48,521	65,955	131,475
Coal Revenue [Member]
Revenue	[1]	184,375	301,542	542,140	984,665
Terminal Revenue [Member]
Revenue		17,008	16,303	49,407	50,829
Freight Revenue [Member]
Revenue		12,909	3,599	19,141	14,115
Intersegment Eliminations [Member]
Revenue		0	0	0	0
(Loss) Earnings Before Income Tax		0	0	0	0
Segment Assets		0	0	0	0
Depreciation, Depletion and Amortization		0	0	0	0
Capital Expenditures		0	0	0	0
Intersegment Eliminations [Member] | Coal Revenue [Member]
Revenue	[1]	0	0	0	0
Intersegment Eliminations [Member] | Terminal Revenue [Member]
Revenue		0	0	0	0
Intersegment Eliminations [Member] | Freight Revenue [Member]
Revenue		0	0	0	0
Pennsylvania Mining Complex [Member] | Operating Segments [Member]
Revenue		196,975	305,141	560,686	998,780
(Loss) Earnings Before Income Tax		(6,930)	30,546	(18,405)	156,029
Segment Assets		1,878,350	2,014,381	1,878,350	2,014,381
Depreciation, Depletion and Amortization		49,944	45,829	145,154	136,124
Capital Expenditures		15,733	45,232	52,687	117,417
Pennsylvania Mining Complex [Member] | Operating Segments [Member] | Coal Revenue [Member]
Revenue	[1]	184,066	301,542	541,545	984,665
Pennsylvania Mining Complex [Member] | Operating Segments [Member] | Terminal Revenue [Member]
Revenue		0	0	0	0
Pennsylvania Mining Complex [Member] | Operating Segments [Member] | Freight Revenue [Member]
Revenue		12,909	3,599	19,141	14,115
Other Segments [Member] | Operating Segments [Member]
Revenue		17,317	16,303	50,002	50,829
(Loss) Earnings Before Income Tax		3,488	(21,107)	(9,400)	(80,115)
Segment Assets		676,488	708,854	676,488	708,854
Depreciation, Depletion and Amortization		5,015	8,541	10,903	15,121
Capital Expenditures		3,775	3,289	13,268	14,058
Other Segments [Member] | Operating Segments [Member] | Coal Revenue [Member]
Revenue	[1]	309	0	595	0
Other Segments [Member] | Operating Segments [Member] | Terminal Revenue [Member]
Revenue		17,008	16,303	49,407	50,829
Other Segments [Member] | Operating Segments [Member] | Freight Revenue [Member]
Revenue		$ 0	$ 0	$ 0	$ 0

[1] For the three and nine months ended September 30, 2020 and 2019, the PAMC segment had revenues from the following customers, each comprising over 10% of the Company's total sales: