Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 SunCoke Middletown [Member] Variable Interest Entity, Primary Beneficiary [Member] MW tons	Sep. 30, 2011 SunCoke Middletown [Member] Variable Interest Entity, Primary Beneficiary [Member]	Sep. 30, 2012 SunCoke Middletown [Member] Variable Interest Entity, Primary Beneficiary [Member] MW tons	Sep. 30, 2011 SunCoke Middletown [Member] Variable Interest Entity, Primary Beneficiary [Member]	Sep. 30, 2012 Magnetation LLC [Member] Variable Interest Entity, Not Primary Beneficiary [Member]	Sep. 30, 2012 Magnetation LLC [Member] Variable Interest Entity, Not Primary Beneficiary [Member]	Dec. 31, 2011 Magnetation LLC [Member] Variable Interest Entity, Not Primary Beneficiary [Member]	Oct. 04, 2011 Magnetation LLC [Member] Variable Interest Entity, Not Primary Beneficiary [Member]	Sep. 30, 2012 Vicksmetal Armco Associates [Member] Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Expected Production Of Coke					550,000		550,000
Expected Production Of Electricity					45		45
Operating profit (loss)	$ (12.0)	$ 11.4	$ 48.8	$ 99.4	$ 13.2	$ (4.4)	$ 31.7	$ (5.9)
Income (loss) before income taxes	(28.7)	(6.8)	(9.7)	64.4	13.2	(4.4)	31.7	(5.9)
Variable interest entity, ownership percentage							0.00%						50.00%
Equity method investment, ownership percentage (in hundredths)												49.90%
Income (Loss) from Equity Method Investments									4.6	4.2
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity									75.7	75.7
Investment Commitment Owed									22.5	22.5	47.5
Payments to Acquire Businesses and Interest in Affiliates			$ 38.1	$ 0					$ 25.0