Acquisition of Noncontrolling Interest (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 25, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jul. 26, 2017	Apr. 17, 2017	Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]
Total cost for purchase of public units				$ (24,600,000)	$ 0
Noncontrolling interests decrease		$ (222,900,000)		(222,900,000)				$ (328,800,000)
Decrease in additional paid-in capital		(5,800,000)		(5,800,000)
Deferred tax adjustment		3,400,000		3,400,000
Change in Ownership Interest
Net income attributable to SunCoke Energy, Inc.		(24,200,000)	$ (4,600,000)	(23,200,000)	$ (8,700,000)
Decrease in SunCoke Energy, Inc. equity for the purchase of additional interest in the Partnership		(5,800,000)		(5,800,000)
Change from net income attributable to SunCoke Energy, Inc. and transfers to noncontrolling interest		$ (30,000,000)		(29,000,000)
Public Unit Purchase Program
Subsidiary, Sale of Stock [Line Items]
Authorized purchase amount							$ 50,000,000
Number of shares purchased (in shares)		1,460,404
Percentage of ownership purchased		7.00%
Total cost for purchase of public units		$ (24,600,000)
Noncontrolling interests decrease		$ 15,400,000		$ 15,400,000
Public Unit Purchase Program | Forecast
Change in Ownership Interest
Remaining balance						$ 73,100,000
Public Unit Purchase Program | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Number of shares purchased (in shares)	131,274
Total cost for purchase of public units	$ (2,300,000)
Change in Ownership Interest
Incremental authorized amount	$ 50,000,000