Segment Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 plant mine segment
Segment Reporting Information [Line Items]
Number of reportable segments | segment	1
West Virgina | All Other
Segment Reporting Information [Line Items]
Number of preparation plants	1
Met | Virgina | Operating segments
Segment Reporting Information [Line Items]
Number of active mines | mine	5
Number of preparation plants	2
Met | West Virgina | Operating segments
Segment Reporting Information [Line Items]
Number of active mines | mine	17
Number of preparation plants	6