CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 44.8	$ 100.6
Depreciation	54.9	55.1
Amortization	10.0	7.2
Deferred income taxes	(6.8)	1.5
Pension and OPEB expense (income)	(8.1)	(16.2)
Contributions to pension trust	(6.0)	0.0
Other postretirement benefit payments	(10.1)	(11.4)
Changes in working capital	0.2	(92.5)
Other operating items, net	(13.3)	(8.0)
Net cash flows from operating activities	65.6	36.3
Cash flows from investing activities:
Capital investments	(37.9)	(32.5)
Other investing items, net	0.0	1.5
Net cash flows from investing activities	(37.9)	(31.0)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	(10.0)	0.0
Proceeds from issuance of long-term debt	0.0	400.0
Redemption of long-term debt	0.0	(367.5)
Debt issuance costs	0.0	(7.8)
SunCoke Middletown distributions to noncontrolling interest owners	(10.3)	(15.1)
Other financing items, net	(0.9)	(2.4)
Net cash flows from financing activities	(21.2)	7.2
Net increase (decrease) in cash and cash equivalents	6.5	12.5
Cash and cash equivalents, beginning of period	38.0	173.2
Cash and cash equivalents, end of period	44.5	185.7
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	51.1	51.0
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	3.8	4.1
Net cash flows from operating activities	21.5	20.3
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(10.3)	$ (15.1)
Cash and cash equivalents, beginning of period	0.1
Cash and cash equivalents, end of period	$ 10.6