Acquisition of Noncontrolling Interest (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]
Cash paid									$ 4,200,000	$ 48,700,000	$ 0
Decrease in noncontrolling interest									4,200,000	48,700,000
Decrease in additional paid-in capital									1,200,000	12,000,000
Deferred tax adjustment									300,000	7,100,000
Change in Ownership Interest
Net income attributable to SunCoke Energy, Inc	$ 1,800,000	$ 11,500,000	$ 4,200,000	$ 8,700,000	$ 134,000,000	$ 11,600,000	$ (24,200,000)	$ 1,000,000	26,200,000	122,400,000	$ 14,400,000
Decrease in SunCoke Energy, Inc. equity for the purchase of additional interest in the Partnership									(1,200,000)	(12,000,000)
Changes from net income attributable to SunCoke Energy, Inc and transfers to noncontrolling interest									25,000,000	110,400,000
Public Unit Purchase Program
Subsidiary, Sale of Stock [Line Items]
Authorized purchase amount					$ 100,000,000					$ 100,000,000
Remaining balance	$ 47,100,000								$ 47,100,000
Units purchased (in shares)									231,171	2,853,032
Cash paid									$ 4,200,000	$ 48,700,000
Decrease in noncontrolling interest									2,700,000	29,600,000
Decrease in additional paid-in capital									1,200,000	12,000,000
Deferred tax adjustment									300,000	7,100,000
Change in Ownership Interest
Decrease in SunCoke Energy, Inc. equity for the purchase of additional interest in the Partnership									$ (1,200,000)	$ (12,000,000)