CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 117.1	$ 193.0
Depreciation	109.8	110.2
Amortization	17.3	11.7
Deferred income taxes	(7.2)	4.6
Pension and OPEB expense (income)	(16.2)	(32.4)
Contributions to pension trust	(15.2)	(6.0)
Other postretirement benefit payments	(19.3)	(21.5)
Changes in working capital	28.8	(57.3)
Other operating items, net	(27.7)	0.9
Net cash flows from operating activities	187.4	203.2
Cash flows from investing activities:
Capital investments	(64.0)	(52.1)
Other investing items, net	0.3	2.9
Net cash flows from investing activities	(63.7)	(49.2)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	(80.0)	0.0
Proceeds from issuance of long-term debt	0.0	400.0
Redemption of long-term debt	0.0	(538.2)
Debt issuance costs	0.0	(8.3)
SunCoke Middletown distributions to noncontrolling interest owners	(34.8)	(41.9)
Other financing items, net	(0.9)	(2.5)
Net cash flows from financing activities	(115.7)	(190.9)
Net increase (decrease) in cash and cash equivalents	8.0	(36.9)
Cash and cash equivalents, beginning of period	38.0	173.2
Cash and cash equivalents, end of period	46.0	136.3
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	102.1	101.8
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	7.7	8.4
Net cash flows from operating activities	37.5	39.2
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	$ (34.8)	$ (41.9)