Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 32.9	$ (16.5)	$ (6.5)	$ 0.4	$ (55.8)	$ 6.4	$ (48.6)	$ (3.8)	$ 10.3	$ (101.8)	$ 50.1
Other comprehensive (loss) income:
Reclassifications of prior service cost (benefit) and actuarial loss amortization to earnings (net of related tax (expense) benefit of ($3.4 million), $2.7 million and $1.3 million, respectively)									5.2	(4.0)	(1.9)
Retirement benefit plans funded status adjustment (net of related tax benefit (expense) of $0.1 million, $1.6 million and ($3.8 million), respectively)									(0.4)	(2.6)	5.7
Currency translation adjustment									(3.1)	(0.8)	(10.0)
Comprehensive income (loss)									12.0	(109.2)	43.9
Less: Comprehensive income attributable to noncontrolling interests									32.3	24.3	25.1
Comprehensive (loss) income attributable to SunCoke Energy, Inc.									$ (20.3)	$ (133.5)	$ 18.8