Business Segment Information - Adjusted EBITDA (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Adjusted EBITDA
Adjusted EBITDA attributable to SunCoke Energy, Inc.		$ 28.7	$ 29.8
Add: Adjusted EBITDA attributable to noncontrolling interests		24.3	18.1
Adjusted EBITDA		53.0	47.9
Adjustments to EBITDA [Abstract]
Adjustment to unconsolidated affiliate earnings		0.0	0.3
Charges		0.2
Depreciation, depletion and amortization expense		28.2	23.8
Interest expense, net		14.0	13.9
(Gain) loss on extinguishment of debt		(20.4)	9.4
Income tax expense		3.3	1.1
Asset and goodwill impairment		10.7	0.0
Coal Logistics deferred revenue		9.2	0.0
Reduction of contingent consideration		(3.7)	0.0
Net income		12.6	0.4
Asset impairment		10.7	0.0
Depreciation and amortization expense		28.2	23.8
Deferred income tax expense		3.2	3.1
Changes in working capital and other		(4.9)	(25.6)
Net cash provided by operating activities		29.4	11.1
Reduction of contingent consideration		3.7	0.0
Cost of Products Sold and Operating Expenses
Adjustments to EBITDA [Abstract]
Reduction of contingent consideration		(3.7)
Reduction of contingent consideration		3.7
Convent Marine Terminal
Adjustments to EBITDA [Abstract]
Business combination, contingent consideration	$ 4.2	4.2		$ 7.9
Employee Severance, Contract Termination And Other
Adjustments to EBITDA [Abstract]
Charges		(0.9)	(1.0)
Coal Mining
Adjustments to EBITDA [Abstract]
Charges		0.2
Depreciation, depletion and amortization expense		1.5	2.8
Depreciation and amortization expense		1.5	2.8
Coal Mining | Employee Severance
Adjustments to EBITDA [Abstract]
Charges		0.2		$ 10.2
Coal Mining | Coal Mining Business | Employee Severance
Adjustments to EBITDA [Abstract]
Adjustment in severance accrual			$ 2.2
Coal Mining | Disposal Group, Held-for-sale, Not Discontinued Operation | Coal Mining Permits and Related Reclamation Obligations
Adjustments to EBITDA [Abstract]
Gain (loss) on disposal of business		$ 1.5
Coal Mining | Disposal Group, Held-for-sale, Not Discontinued Operation | Coal Mining Permits and Related Reclamation Obligations | Cost of Products Sold and Operating Expenses
Adjustments to EBITDA [Abstract]
Gain (loss) on disposal of business	$ 1.5