Supplemental Condensed Consolidating Financial Information - Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Sales and other operating revenue	$ 323.2	$ 292.7	$ 632.9	$ 603.8
Equity in (loss) earnings of subsidiaries	0.0	0.0	0.0	0.0
Total revenues, net of equity (loss) earnings of subsidiaries	323.2	292.7	632.9	603.8
Costs and operating expenses
Cost of products sold and operating expenses	257.2	224.4	491.6	464.9
Selling, general and administrative expenses	24.1	23.7	43.8	47.0
Depreciation and amortization expense	33.3	28.6	66.6	56.8
Loss on divestiture of business	0.0	5.1	0.0	14.7
Total costs and operating expenses	314.6	281.8	602.0	583.4
Operating (loss) income	8.6	10.9	30.9	20.4
Interest (income) expense, net - affiliate	0.0	0.0	0.0	0.0
Interest expense (income), net	15.2	13.4	28.9	27.4
Total interest expense (income), net	15.2	13.4	28.9	27.4
Loss (gain) on extinguishment of debt	20.2	(3.5)	20.3	(23.9)
(Loss) income before income tax expense (benefit)	(26.8)	1.0	(18.3)	16.9
Income tax expense (benefit)	4.7	0.0	70.9	3.3
Net (loss) income	(31.5)	1.0	(89.2)	13.6
Less: Net (loss) income attributable to noncontrolling interests	(7.3)	5.6	(66.0)	22.3
Net loss attributable to SunCoke Energy, Inc.	(24.2)	(4.6)	(23.2)	(8.7)
Comprehensive (loss) income	(31.8)	1.7	(89.4)	14.7
Less: Comprehensive income (loss) attributable to noncontrolling interests	(7.3)	5.6	(66.0)	22.3
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	(24.5)	(3.9)	(23.4)	(7.6)
Reportable Legal Entities | Issuer
Revenues
Sales and other operating revenue	0.0	0.0	0.0	0.0
Equity in (loss) earnings of subsidiaries	(17.8)	(2.1)	(13.5)	(1.4)
Total revenues, net of equity (loss) earnings of subsidiaries	(17.8)	(2.1)	(13.5)	(1.4)
Costs and operating expenses
Cost of products sold and operating expenses	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	2.9	2.8	5.0	5.8
Depreciation and amortization expense	0.0	0.0	0.0	0.0
Loss on divestiture of business		0.0		0.0
Total costs and operating expenses	2.9	2.8	5.0	5.8
Operating (loss) income	(20.7)	(4.9)	(18.5)	(7.2)
Interest (income) expense, net - affiliate	0.0	0.0	0.0	0.0
Interest expense (income), net	1.2	1.7	2.5	3.2
Total interest expense (income), net	1.2	1.7	2.5	3.2
Loss (gain) on extinguishment of debt	0.3	0.0	0.4	0.0
(Loss) income before income tax expense (benefit)	(22.2)	(6.6)	(21.4)	(10.4)
Income tax expense (benefit)	2.0	(2.0)	1.8	(1.7)
Net (loss) income	(24.2)	(4.6)	(23.2)	(8.7)
Less: Net (loss) income attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net loss attributable to SunCoke Energy, Inc.	(24.2)	(4.6)	(23.2)	(8.7)
Comprehensive (loss) income	(24.5)	(3.9)	(23.4)	(7.6)
Less: Comprehensive income (loss) attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	(24.5)	(3.9)	(23.4)	(7.6)
Reportable Legal Entities | Guarantor Subsidiaries
Revenues
Sales and other operating revenue	51.5	42.2	102.4	84.9
Equity in (loss) earnings of subsidiaries	(19.6)	0.0	(102.1)	11.3
Total revenues, net of equity (loss) earnings of subsidiaries	31.9	42.2	0.3	96.2
Costs and operating expenses
Cost of products sold and operating expenses	38.6	31.6	75.5	65.5
Selling, general and administrative expenses	9.9	6.9	15.0	15.8
Depreciation and amortization expense	1.8	2.3	3.8	4.5
Loss on divestiture of business		0.0		0.0
Total costs and operating expenses	50.3	40.8	94.3	85.8
Operating (loss) income	(18.4)	1.4	(94.0)	10.4
Interest (income) expense, net - affiliate	(1.9)	(1.9)	(3.7)	(3.9)
Interest expense (income), net	0.0	0.0	(0.2)	0.0
Total interest expense (income), net	(1.9)	(1.9)	(3.9)	(3.9)
Loss (gain) on extinguishment of debt	0.0	0.0	0.0	0.0
(Loss) income before income tax expense (benefit)	(16.5)	3.3	(90.1)	14.3
Income tax expense (benefit)	(4.8)	1.0	(86.0)	7.1
Net (loss) income	(11.7)	2.3	(4.1)	7.2
Less: Net (loss) income attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net loss attributable to SunCoke Energy, Inc.	(11.7)	2.3	(4.1)	7.2
Comprehensive (loss) income	(11.7)	2.3	(4.1)	7.2
Less: Comprehensive income (loss) attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	(11.7)	2.3	(4.1)	7.2
Reportable Legal Entities | Non- Guarantor Subsidiaries
Revenues
Sales and other operating revenue	272.8	251.5	532.7	520.9
Equity in (loss) earnings of subsidiaries	0.0	0.0	0.0	0.0
Total revenues, net of equity (loss) earnings of subsidiaries	272.8	251.5	532.7	520.9
Costs and operating expenses
Cost of products sold and operating expenses	219.7	193.8	418.3	401.4
Selling, general and administrative expenses	11.3	14.0	23.8	25.4
Depreciation and amortization expense	31.5	26.3	62.8	52.3
Loss on divestiture of business		5.1		14.7
Total costs and operating expenses	262.5	239.2	504.9	493.8
Operating (loss) income	10.3	12.3	27.8	27.1
Interest (income) expense, net - affiliate	1.9	1.9	3.7	3.9
Interest expense (income), net	14.0	11.7	26.6	24.2
Total interest expense (income), net	15.9	13.6	30.3	28.1
Loss (gain) on extinguishment of debt	19.9	(3.5)	19.9	(23.9)
(Loss) income before income tax expense (benefit)	(25.5)	2.2	(22.4)	22.9
Income tax expense (benefit)	7.5	1.0	155.1	(2.1)
Net (loss) income	(33.0)	1.2	(177.5)	25.0
Less: Net (loss) income attributable to noncontrolling interests	(7.3)	5.6	(66.0)	22.3
Net loss attributable to SunCoke Energy, Inc.	(25.7)	(4.4)	(111.5)	2.7
Comprehensive (loss) income	(33.3)	1.9	(177.7)	26.1
Less: Comprehensive income (loss) attributable to noncontrolling interests	(7.3)	5.6	(66.0)	22.3
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	(26.0)	(3.7)	(111.7)	3.8
Combining and Consolidating Adjustments
Revenues
Sales and other operating revenue	(1.1)	(1.0)	(2.2)	(2.0)
Equity in (loss) earnings of subsidiaries	37.4	2.1	115.6	(9.9)
Total revenues, net of equity (loss) earnings of subsidiaries	36.3	1.1	113.4	(11.9)
Costs and operating expenses
Cost of products sold and operating expenses	(1.1)	(1.0)	(2.2)	(2.0)
Selling, general and administrative expenses	0.0	0.0	0.0	0.0
Depreciation and amortization expense	0.0	0.0	0.0	0.0
Loss on divestiture of business		0.0		0.0
Total costs and operating expenses	(1.1)	(1.0)	(2.2)	(2.0)
Operating (loss) income	37.4	2.1	115.6	(9.9)
Interest (income) expense, net - affiliate	0.0	0.0	0.0	0.0
Interest expense (income), net	0.0	0.0	0.0	0.0
Total interest expense (income), net	0.0	0.0	0.0	0.0
Loss (gain) on extinguishment of debt	0.0	0.0	0.0	0.0
(Loss) income before income tax expense (benefit)	37.4	2.1	115.6	(9.9)
Income tax expense (benefit)	0.0	0.0	0.0	0.0
Net (loss) income	37.4	2.1	115.6	(9.9)
Less: Net (loss) income attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net loss attributable to SunCoke Energy, Inc.	37.4	2.1	115.6	(9.9)
Comprehensive (loss) income	37.7	1.4	115.8	(11.0)
Less: Comprehensive income (loss) attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	$ 37.7	$ 1.4	$ 115.8	$ (11.0)