Segment Information - Segment Results (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reportable segment results
Revenues	$ 1,268.8	$ 1,321.9	$ 2,632.8	$ 2,013.3
Adjusted EBITDA	358.2	577.8	748.8	905.3
Seaborne Thermal
Reportable segment results
Revenues	399.5	354.9	746.0	606.1
Adjusted EBITDA	197.5	176.8	361.5	267.3
Seaborne Metallurgical
Reportable segment results
Revenues	372.5	533.8	660.9	855.1
Adjusted EBITDA	102.5	299.7	193.3	480.7
Powder River Basin
Reportable segment results
Revenues	259.7	229.7	565.0	480.9
Adjusted EBITDA	26.2	(2.0)	62.0	5.6
Other U.S. Thermal
Reportable segment results
Revenues	199.9	224.9	449.3	428.0
Adjusted EBITDA	51.9	61.9	116.1	111.9
Corporate and Other (1)
Reportable segment results
Revenues	37.2	(21.4)	211.6	(356.8)
Adjusted EBITDA	$ (19.9)	$ 41.4	$ 15.9	$ 39.8