Supplementary Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Cash Flow Information [Abstract]
Interest, net of capitalized interest	$ 161.3	$ 121.9	$ 116.2
Income taxes	0.7	(0.3)	1.2
Supplementary Cash Flow [Line Items]
Net cash flows from operating activities	200.3	(322.8)	(110.2)
Cash and Cash Equivalents, at Carrying Value	56.6	70.2	45.3	$ 227.0
Supplementary cash flow, noncash investing and financing activities [Abstract]
Capital investments	37.4	29.5	10.2
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Supplementary Cash Flow [Line Items]
Net cash flows from operating activities	87.4	66.4	82.6
Cash and Cash Equivalents, at Carrying Value	7.6	18.2
Restricted stock and RSUs [Member]
Supplementary cash flow, noncash investing and financing activities [Abstract]
Issuance of restricted stock and restricted stock units	$ 4.1	$ 4.5	$ 3.0