Note 15 - Segment Information - Industry Segment (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue		$ 121,296	$ 371,182	$ 396,396	$ 728,165
Earnings (Loss) Before Income Tax		(28,746)	47,022	(24,363)	66,475
Segment Assets		2,566,132	2,765,471	2,566,132	2,765,471	$ 2,693,802
Depreciation, Depletion and Amortization		46,155	46,151	101,098	96,875
Capital Expenditures		19,269	48,783	46,447	82,954
Coal Revenue [Member]
Revenue	[1]	102,313	350,620	357,765	683,123
Terminal Revenue [Member]
Revenue		15,898	16,708	32,399	34,526
Freight Revenue [Member]
Revenue		3,085	3,854	6,232	10,516
Intersegment Eliminations [Member]
Revenue		0	0	0	0
Earnings (Loss) 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		105,111	354,474	363,710	693,639
Earnings (Loss) Before Income Tax		(21,823)	60,786	(10,949)	125,484
Segment Assets		1,889,557	1,973,627	1,889,557	1,973,627
Depreciation, Depletion and Amortization		46,793	45,427	95,210	90,295
Capital Expenditures		16,262	39,813	36,954	72,185
Pennsylvania Mining Complex [Member] | Operating Segments [Member] | Coal Revenue [Member]
Revenue	[1]	102,026	350,620	357,478	683,123
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		3,085	3,854	6,232	10,516
Other Segments [Member] | Operating Segments [Member]
Revenue		16,185	16,708	32,686	34,526
Earnings (Loss) Before Income Tax		(6,923)	(13,764)	(13,414)	(59,009)
Segment Assets		676,575	791,844	676,575	791,844
Depreciation, Depletion and Amortization		(638)	724	5,888	6,580
Capital Expenditures		3,007	8,970	9,493	10,769
Other Segments [Member] | Operating Segments [Member] | Coal Revenue [Member]
Revenue	[1]	287	0	287	0
Other Segments [Member] | Operating Segments [Member] | Terminal Revenue [Member]
Revenue		15,898	16,708	32,399	34,526
Other Segments [Member] | Operating Segments [Member] | Freight Revenue [Member]
Revenue		$ 0	$ 0	$ 0	$ 0

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