CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income (loss)	$ (316.0)	$ (63.8)
Depreciation	166.6	146.3
Amortization	17.0	15.9
Impairment of Magnetation investment	256.3	0.0
Deferred income taxes	37.8	6.3
Pension and OPEB expense (income)	(48.1)	(74.2)
Contributions to pension trust	(24.1)	(196.5)
Other postretirement benefit payments	(32.9)	(48.8)
Other operating items, net	24.6	(14.1)
Net cash flows from operating activities	200.1	(380.6)
Cash flows from investing activities:
Capital investments	(71.0)	(39.3)
Investments in Magnetation joint venture	0.0	(90.0)
Investment in acquired business, net of cash acquired	0.0	(677.2)
Proceeds from sale of equity investee	25.0	0.0
Other investing items, net	1.5	15.4
Net cash flows from investing activities	(44.5)	(791.1)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	(55.0)	470.0
Proceeds from issuance of long-term debt	0.0	427.1
Redemption of long-term debt	(10.1)	(0.6)
Proceeds from issuance of common stock	0.0	345.3
Debt issuance costs	0.0	(10.6)
SunCoke Middletown distributions to noncontrolling interest owners	(69.7)	(40.6)
Other financing items, net	(1.0)	(3.4)
Net cash flows from financing activities	(135.8)	1,187.2
Net increase (decrease) in cash and cash equivalents	19.8	15.5
Cash and cash equivalents, beginning of period	70.2	45.3
Cash and cash equivalents, end of period	90.0	60.8
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	155.9	135.6
Changes in working capital	111.9	(134.9)
Cash flows from investing activities:
Capital investments	(70.1)	(38.2)
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	10.7	10.7
Changes in working capital	10.1	(13.7)
Net cash flows from operating activities	68.2	43.8
Cash flows from investing activities:
Capital investments	(0.9)	(1.1)
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(69.7)	(40.6)
Cash and cash equivalents, beginning of period	18.2
Cash and cash equivalents, end of period	15.9
Zanesville Works Retiree Healthcare Benefits Litigation [Member]
Cash flows from operating activities:
Contribution to retirees VEBA	$ (3.1)	$ (3.1)