Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Total SunCoke Energy, Inc. Equity	Non-controlling Interests
Beginning balance at Dec. 31, 2015	$ 622.8	$ 0.7	$ (140.7)	$ 486.1	$ (19.8)	$ (36.4)	$ 289.9	$ 332.9
Beginning balance, shares at Dec. 31, 2015		71,489,448	7,477,657
Stockholders' Equity
Net income	59.5					14.4	14.4	45.1
Reclassifications of prior service cost and actuarial loss amortization to earnings (net of related tax expense of $3.4 million)	0.0
Retirement benefit plans funded status adjustment (net of related tax benefit of $0.2 million, $0.3 million and $0.1 million, respectively)	(0.2)				(0.2)		(0.2)
Currency translation adjustment	1.0				1.0		1.0
Recognition of accumulated currency translation loss upon sale of equity method investment	0.0
Cash distributions to noncontrolling interests	(49.2)							(49.2)
Share-based compensation expense	6.5			6.5			6.5
Share issuances, net of shares withheld for taxes and other equity activities	(0.5)			(0.5)			(0.5)
Share issuances, net of shares withheld for taxes and other equity activities, shares		217,856
Ending balance. shares at Dec. 31, 2016		71,707,304	7,477,657
Ending balance at Dec. 31, 2016	639.9	$ 0.7	$ (140.7)	492.1	(19.0)	(22.0)	311.1	328.8
Stockholders' Equity
Net income	103.5					122.4	122.4	(18.9)
Reclassifications of prior service cost and actuarial loss amortization to earnings (net of related tax expense of $3.4 million)	0.2				0.2		0.2
Retirement benefit plans funded status adjustment (net of related tax benefit of $0.2 million, $0.3 million and $0.1 million, respectively)	(0.8)				(0.8)		(0.8)
Currency translation adjustment	(0.5)				(0.5)		(0.5)
Recognition of accumulated currency translation loss upon sale of equity method investment	0.0
Cash distributions to noncontrolling interests	(47.0)							(47.0)
Share-based compensation expense	4.8			4.7			4.7	0.1
Share issuances, net of shares withheld for taxes and other equity activities	1.1			1.1			1.1
Share issuances, net of shares withheld for taxes and other equity activities, shares		299,601
Acquisition of additional interest in the Partnership:
Partnership unit repurchases and cash paid	(48.7)			(19.1)			(19.1)	(29.6)
Deferred tax adjustment	7.1			7.1			7.1
Ending balance. shares at Dec. 31, 2017		72,006,905	7,477,657
Ending balance at Dec. 31, 2017	659.6	$ 0.7	$ (140.7)	486.2	(21.2)	101.2	426.2	233.4
Acquisition of additional interest in the Partnership:
Cumulative effect from adoption of ASU 2016-09 | ASU 2016-09	0.0			0.3		(0.3)
Cumulative effect from adoption of ASU 2016-09 | ASU 2018-02	0.0			(1.1)		1.1
Net income	47.0					26.2	26.2	20.8
Reclassifications of prior service cost and actuarial loss amortization to earnings (net of related tax expense of $3.4 million)	(0.1)				(0.1)		(0.1)
Retirement benefit plans funded status adjustment (net of related tax benefit of $0.2 million, $0.3 million and $0.1 million, respectively)	0.6				0.6		0.6
Currency translation adjustment	(1.4)				(1.4)		(1.4)
Recognition of accumulated currency translation loss upon sale of equity method investment	9.0				9.0		9.0	0.0
Cash distributions to noncontrolling interests	(31.9)							(31.9)
Share-based compensation expense	3.1			3.1			3.1	0.0
Share issuances, net of shares withheld for taxes and other equity activities	0.7			0.7			0.7
Share issuances, net of shares withheld for taxes and other equity activities, shares		226,845
Partnership unit repurchases and cash paid	(4.2)			(1.5)			(1.5)	(2.7)
Deferred tax adjustment	0.3			0.3			0.3
Ending balance. shares at Dec. 31, 2018		72,233,750	7,477,657
Ending balance at Dec. 31, 2018	$ 682.7	$ 0.7	$ (140.7)	$ 488.8	$ (13.1)	$ 127.4	$ 463.1	$ 219.6