Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Name:	us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Variable Interest Entities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Variable Interest Entity [Line Items]
Income before income taxes	$ 20.2	$ 86.3	$ 110.6	$ 198.0
SunCoke Middletown [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable interest entity, ownership percentage (in hundredths)			0.00%
Income before income taxes	$ 17.0	$ 17.8	$ 43.2	$ 49.8
Vicksmetal Armco Associates [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable interest entity, ownership percentage (in hundredths)			50.00%