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Debt - Revolving Facility (Narrative) (Details) - USD ($)	1 Months Ended
	Jul. 30, 2025	Jun. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Outstanding balance		$ 500,000,000.0	$ 500,000,000.0
Revolving Credit Facility \| SunCoke Revolving Credit Facility, Due 2024 \| Line of Credit
Debt Instrument [Line Items]
Outstanding balance		0
Remaining borrowing capacity		350,000,000.0
Revolving Credit Facility \| SunCoke Revolving Credit Facility, Due July 2030 \| Line of Credit \| Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, increase (decrease), net	$ (25,000,000)
Maximum borrowing capacity	$ 325,000,000
Letter of Credit \| SunCoke Revolving Credit Facility, Due 2024 \| Line of Credit
Debt Instrument [Line Items]
Outstanding balance		$ 7,300,000