CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income (loss)	$ 38.3	$ (340.3)
Depreciation	108.0	111.1
Amortization	9.9	12.5
Impairment of Magnetation investment	0.0	256.3
Deferred income taxes	(7.2)	20.7
Pension and OPEB expense (income)	(23.8)	(32.2)
Contributions to pension trust	0.0	(1.0)
Other postretirement benefit payments	(16.0)	(22.2)
Changes in working capital	122.2	52.6
Other operating items, net	41.6	26.4
Net cash flows from operating activities	273.0	83.9
Cash flows from investing activities:
Capital investments	(53.9)	(49.7)
Cash held for retirement of debt	(135.4)	0.0
Proceeds from sale of equity investee	0.0	25.0
Other investing items, net	2.1	1.3
Net cash flows from investing activities	(187.2)	(23.4)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	(400.0)	(10.0)
Proceeds from issuance of long-term debt	380.0	0.0
Redemption of long-term debt	(259.0)	(2.2)
Proceeds from issuance of common stock	249.4	0.0
Debt issuance costs	(19.3)	0.0
SunCoke Middletown distributions to noncontrolling interest owners	(37.0)	(42.6)
Other financing items, net	(0.3)	(0.9)
Net cash flows from financing activities	(86.2)	(55.7)
Net increase (decrease) in cash and cash equivalents	(0.4)	4.8
Cash and cash equivalents, beginning of period	56.6	70.2
Cash and cash equivalents, end of period	56.2	75.0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	100.8	103.9
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	7.2	7.2
Net cash flows from operating activities	43.9	46.1
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(37.0)	$ (42.6)
Cash and cash equivalents, beginning of period	7.6
Cash and cash equivalents, end of period	$ 14.1