Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Supplemental cash flow, net cash paid (received) during the period for: [Abstract]
Interest, net of capitalized interest	$ 78.7	$ 82.4
Income taxes	(3.2)	0.1
Net Cash Provided by (Used in) Operating Activities	273.0	83.9
Cash and Cash Equivalents, at Carrying Value	56.2	75.0	$ 56.6	$ 70.2
Supplemental cash flow, noncash investing and financing activities [Abstract]
Capital investments	24.3	24.3
Restricted Stock and Restricted Stock Units [Member]
Supplemental cash flow, noncash investing and financing activities [Abstract]
Issuance of restricted stock and restricted stock units	1.8	3.8
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Supplemental cash flow, net cash paid (received) during the period for: [Abstract]
Net Cash Provided by (Used in) Operating Activities	43.9	46.1
Cash and Cash Equivalents, at Carrying Value	14.1		$ 7.6
Research And Innovation Center Middletown OH [Member]
Supplemental cash flow, noncash investing and financing activities [Abstract]
Research and Innovation Center capital lease	$ 15.4	$ 0.0