CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 155.1	$ 38.3
Depreciation	110.2	108.0
Amortization	11.7	9.9
Deferred income taxes	(17.9)	(7.2)
Pension and OPEB expense (income)	(32.4)	(23.8)
Contributions to pension trust	(6.0)	0.0
Other postretirement benefit payments	(21.5)	(16.0)
Changes in working capital	6.5	122.2
Other operating items, net	(2.5)	41.6
Net cash flows from operating activities	203.2	273.0
Cash flows from investing activities:
Capital investments	(52.1)	(53.9)
Cash held for retirement of debt	0.0	(135.4)
Other investing items, net	2.9	2.1
Net cash flows from investing activities	(49.2)	(187.2)
Cash flows from financing activities:
Net borrowings (payments) under credit facility	0.0	(400.0)
Proceeds from issuance of long-term debt	400.0	380.0
Redemption of long-term debt	(538.2)	(259.0)
Proceeds from issuance of common stock	0.0	249.4
Debt issuance costs	(8.3)	(19.3)
SunCoke Middletown distributions to noncontrolling interest owners	(41.9)	(37.0)
Other financing items, net	(2.5)	(0.3)
Net cash flows from financing activities	(190.9)	(86.2)
Net increase (decrease) in cash and cash equivalents	(36.9)	(0.4)
Cash and cash equivalents, beginning of period	173.2	56.6
Cash and cash equivalents, end of period	136.3	56.2
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Cash flows from operating activities:
Depreciation	101.8	100.8
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Depreciation	8.4	7.2
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	(41.9)	(37.0)
Cash and cash equivalents, beginning of period	5.0
Cash and cash equivalents, end of period	2.2
Variable Interest Entity, Primary Beneficiary [Member] | SunCoke Middletown [Member]
Cash flows from operating activities:
Net cash flows from operating activities	$ 39.2	$ 43.9