CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 244.1	$ 164.9	$ 49.2
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	220.2	226.0	216.6
Amortization	32.0	24.1	18.4
Asset impairment charge	0.0	75.6	0.0
Charge (credit) for transportation costs affected by termination of pellet agreement	0.0	(19.3)	32.9
Deferred income taxes	(8.0)	(9.0)	(4.1)
Contributions to pension trust	(49.9)	(44.1)	0.0
Pension and OPEB (income) expense	(11.6)	(64.4)	24.3
(Gains) losses on retirement of debt	(2.0)	21.3	9.2
Mark-to-market (gains) losses on derivative contracts	(8.9)	(45.7)	1.2
Other operating items, net	2.4	20.1	3.0
Changes in assets and liabilities, net of effect of acquired business:
Accounts receivable	(125.0)	(34.4)	0.1
Inventory	(34.8)	(116.7)	129.6
Accounts payable and other current liabilities	119.6	46.2	(143.2)
Other assets	52.9	(6.5)	40.9
Other pension payments	(1.0)	(1.1)	(33.0)
OPEB payments	(35.6)	(39.6)	(34.4)
Other liabilities	(29.7)	1.4	(6.1)
Net cash flows from operating activities	364.7	198.8	304.6
Cash flows from investing activities:
Capital investments	(152.0)	(152.5)	(127.6)
Investment in acquired business, net of cash acquired	0.0	(360.4)	0.0
Other investing items, net	0.1	4.2	2.3
Net cash flows from investing activities	(151.9)	(508.7)	(125.3)
Cash flows from financing activities:
Net borrowings (repayments) under credit facility	(115.0)	450.0	(550.0)
Proceeds from issuance of long-term debt	0.0	680.0	380.0
Redemption of long-term debt	(12.6)	(848.4)	(392.8)
Proceeds from issuance of common stock	0.0	0.0	600.4
Debt issuance costs	0.0	(25.3)	(20.4)
SunCoke Middletown distributions to noncontrolling interest owners	(73.7)	(79.1)	(85.1)
Other financing items, net	(0.9)	(2.5)	5.2
Net cash flows from financing activities	(202.2)	174.7	(62.7)
Net increase (decrease) in cash and cash equivalents	10.6	(135.2)	116.6
Cash and cash equivalents, beginning of year	38.0	173.2	56.6
Cash and cash equivalents, end of year	48.6	38.0	173.2
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	201.6	209.8	201.7
SunCoke Middletown [Member]
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	18.6	16.2	14.9
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	$ (73.7)	$ (79.1)	$ (85.1)