CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 166.4	$ 107.2
Depreciation	168.2	161.7
Amortization	17.9	14.3
Deferred income taxes	(36.1)	6.1
Pension and OPEB expense (income)	(48.6)	(29.5)
Contributions to pension trust	(38.1)	0.0
Other pension payments	(0.7)	(32.6)
Other postretirement benefit payments	(30.0)	(24.3)
Changes in working capital, net of effect of acquired business	(44.1)	37.5
Other operating items, net	(0.9)	47.5
Net cash flows from operating activities	154.0	287.9
Cash flows from investing activities:
Capital investments	(88.7)	(81.9)
Investment in acquired business, net of cash acquired	(360.9)	0.0
Other investing items, net	4.2	2.2
Net cash flows from investing activities	(445.4)	(79.7)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	415.0	(360.0)
Proceeds from issuance of long-term debt	680.0	380.0
Redemption of long-term debt	(821.8)	(392.8)
Proceeds from issuance of common stock	0.0	249.4
Debt issuance costs	(25.0)	(20.4)
SunCoke Middletown distributions to noncontrolling interest owners	(58.2)	(63.2)
Other financing items, net	(2.5)	(0.3)
Net cash flows from financing activities	187.5	(207.3)
Net increase (decrease) in cash and cash equivalents	(103.9)	0.9
Cash and cash equivalents, beginning of period	173.2	56.6
Cash and cash equivalents, end of period	69.3	57.5
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	155.8	150.8
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	12.4	10.9
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(58.2)	(63.2)
Cash and cash equivalents, beginning of period	5.0
Cash and cash equivalents, end of period	4.5
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Net cash flows from operating activities	$ 59.2	$ 68.0