Acquisitions and Dropdown Transactions (Convent Marine Terminal Acquisition Narrative) (Details) - SunCoke Energy Partners, L.P. - Convent Marine Terminal - USD ($) shares in Millions, $ in Millions		12 Months Ended
	Aug. 12, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Interest acquired (as a percent)	100.00%
Total consideration	$ 403.1
Consideration transferred, cash payment	191.7
Debt assumed	114.9
Cash withheld to fund capital expenditures	$ 21.5
Revenue from acquisition to period end		$ 71.1	$ 62.7	$ 28.6
Operating income from acquisition to period end		$ 42.3	$ 46.5	$ 18.4
Common units
Business Acquisition [Line Items]
Stock issued, shares	4.8
Stock issued as consideration	$ 75.0