CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 78.7	$ 4.4
Depreciation	55.1	53.7
Amortization	7.2	5.3
Deferred income taxes	(11.9)	4.5
Pension and OPEB expense (income)	(16.2)	(11.9)
Other postretirement benefit payments	(11.4)	(9.6)
Changes in working capital	(54.6)	71.6
Other operating items, net	(10.6)	18.7
Net cash flows from operating activities	36.3	136.7
Cash flows from investing activities:
Capital investments	(32.5)	(28.8)
Other investing items, net	1.5	(0.1)
Net cash flows from investing activities	(31.0)	(28.9)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	0.0	(30.0)
Proceeds from issuance of long-term debt	400.0	0.0
Redemption of long-term debt	(367.5)	0.0
Debt issuance costs	(7.8)	0.0
SunCoke Middletown distributions to noncontrolling interest owners	(15.1)	(21.1)
Other financing items, net	(2.4)	(0.3)
Net cash flows from financing activities	7.2	(51.4)
Net increase (decrease) in cash and cash equivalents	12.5	56.4
Cash and cash equivalents, beginning of period	173.2	56.6
Cash and cash equivalents, end of period	185.7	113.0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	51.0	50.1
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	4.1	3.6
Net cash flows from operating activities	20.3	20.4
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(15.1)	$ (21.1)
Cash and cash equivalents, beginning of period	5.0
Cash and cash equivalents, end of period	$ 10.1