Segment Information - Segment Results (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reportable segment results
Revenues	$ 983.6	$ 1,364.0
Adjusted EBITDA	160.5	390.6
Seaborne Thermal
Reportable segment results
Revenues	283.9	346.5
Adjusted EBITDA	93.8	164.0
Seaborne Metallurgical
Reportable segment results
Revenues	247.0	288.4
Adjusted EBITDA	48.3	90.8
Powder River Basin
Reportable segment results
Revenues	254.1	305.3
Adjusted EBITDA	16.4	35.8
Other U.S. Thermal
Reportable segment results
Revenues	191.6	249.4
Adjusted EBITDA	46.5	64.2
Corporate and Other (1)
Reportable segment results
Revenues	7.0	174.4
Adjusted EBITDA	$ (44.5)	$ 35.8