Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 594,412	$ 382,261	$ 1,402,345	$ 1,107,014
Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	25	908	1,429	19,467
North America revenues
Disaggregation of Revenue [Line Items]
Revenues	300,634	256,378	738,617	715,905
North America revenues | Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	25	908	1,429	19,467
Seaborne revenues
Disaggregation of Revenue [Line Items]
Revenues	293,778	125,883	663,728	391,109
Seaborne revenues | Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
MET | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	295,291	168,054	693,522	489,660
MET | North America revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	52,654	47,197	124,782	117,058
MET | Seaborne revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	242,637	120,857	568,740	372,602
Thermal | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	299,096	213,299	707,394	597,887
Thermal | North America revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	247,955	208,273	612,406	579,380
Thermal | Seaborne revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	$ 51,141	$ 5,026	$ 94,988	$ 18,507