Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Cash Flow Information [Abstract]
Interest, net of capitalized interest	$ 116.2	$ 69.5	$ 44.3
Income taxes	1.2	1.3	0.1
Supplemental Cash Flow [Line Items]
Net cash flows from operating activities	(110.2)	(270.8)	(180.5)
Cash and Cash Equivalents, at Carrying Value	45.3	227.0	42.0	216.8
Supplemental cash flow, noncash investing and financing activities [Abstract]
Issuance of restricted stock and restricted stock units	3.0	5.4	5.7
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Supplemental cash flow, noncash investing and financing activities [Abstract]
Capital investments	10.2	13.9	10.2
AK Coal [Member]
Supplemental cash flow, noncash investing and financing activities [Abstract]
Issuance of note payable for AK Coal purchase (at fair value)	0	0	10.2
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Supplemental Cash Flow [Line Items]
Net cash flows from operating activities	82.6	55.2	(15.7)
Cash and Cash Equivalents, at Carrying Value	14.2	0
Supplemental cash flow, noncash investing and financing activities [Abstract]
Capital investments	$ 0	$ 0	$ 16.3