Fair Value Measurement (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Company's debt	$ 898.7	$ 919.7
Total borrowings	885.8	887.3
Fair Value, Inputs, Level 3 | SunCoke Energy Partners, L.P. | Convent Marine Terminal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration	3.1	2.5
Fair Value, Inputs, Level 3 | SunCoke Energy Partners, L.P. | Convent Marine Terminal | Accrued Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration	0.4
Fair Value, Inputs, Level 3 | SunCoke Energy Partners, L.P. | Convent Marine Terminal | Other Deferred Credits and Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration	2.7
Cash Equivalents | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	$ 7.7	$ 5.5