CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 63.0	$ 244.1	$ 164.9
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	192.6	220.2	226.0
Amortization	32.7	32.0	24.1
Ashland Works closure	56.0	0.0	0.0
Asset impairment charge	0.0	0.0	75.6
Credit for adjustment of liability for transportation costs	0.0	0.0	(19.3)
Deferred income taxes	(1.0)	(8.0)	(9.0)
Contributions to pension trust	(43.5)	(49.9)	(44.1)
Pension and OPEB (income) expense	17.8	(11.6)	(64.4)
(Gains) losses on retirement of debt	(0.8)	(2.0)	21.3
Mark-to-market (gains) losses on derivative contracts	(44.0)	(8.9)	(45.7)
Other operating items, net	(7.6)	2.4	20.1
Changes in assets and liabilities, net of effect of acquired business:
Accounts receivable	60.2	(125.0)	(34.4)
Inventory	73.7	(34.8)	(116.7)
Accounts payable and other current liabilities	(172.8)	119.6	46.2
Other assets	75.0	52.9	(6.5)
Other pension payments	(0.9)	(1.0)	(1.1)
OPEB payments	(26.8)	(35.6)	(39.6)
Other liabilities	(7.7)	(29.7)	1.4
Net cash flows from operating activities	265.9	364.7	198.8
Cash flows from investing activities:
Capital investments	(194.8)	(152.0)	(152.5)
Investment in acquired business, net of cash acquired	0.0	0.0	(360.4)
Other investing items, net	6.6	0.1	4.2
Net cash flows from investing activities	(188.2)	(151.9)	(508.7)
Cash flows from financing activities:
Net borrowings (repayments) under credit facility	115.0	(115.0)	450.0
Proceeds from issuance of long-term debt	0.0	0.0	680.0
Redemption of long-term debt	(152.3)	(12.6)	(848.4)
Debt issuance costs	0.0	0.0	(25.3)
SunCoke Middletown distributions to noncontrolling interest owners	(55.6)	(73.7)	(79.1)
Other financing items, net	(2.4)	(0.9)	(2.5)
Net cash flows from financing activities	(95.3)	(202.2)	174.7
Net increase (decrease) in cash and cash equivalents	(17.6)	10.6	(135.2)
Cash and cash equivalents, beginning of year	48.6	38.0	173.2
Cash and cash equivalents, end of year	31.0	48.6	38.0
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	169.9	201.6	209.8
Cash flows from investing activities:
Capital investments	(180.8)	(150.1)	(149.6)
SunCoke Middletown [Member]
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation	22.7	18.6	16.2
Cash flows from investing activities:
Capital investments	(14.0)	(1.9)	(2.9)
Cash flows from financing activities:
SunCoke Middletown distributions to noncontrolling interest owners	$ (55.6)	$ (73.7)	$ (79.1)