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Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect		$ (102.0)			$ (102.0)		$ (104.8)
Income tax effect		4.0			4.0		6.1
Accumulated other comprehensive loss		(98.0)			(98.0)		(98.7)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	$ 762.2	709.4	$ 762.2	$ 853.1	762.2	$ 829.6
Impact of ASU 2018-02			1.3
Balance, end		689.9		833.5	689.9	833.5
Defined benefit plan and other postretirement liabilities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect		(104.3)			(104.3)		(107.3)
Income tax effect		(4.5)			(4.5)		(6.6)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	(100.7)	(100.7)	(100.7)	(90.8)	(100.7)	(93.8)
Impact of ASU 2018-02	(1.3)
Net amount reclassified to net income (loss)		0.7		0.1	2.1	3.2
Balance, end		(100.0)		(90.7)	(100.0)	(90.7)
Unrealized gain (loss) on financial instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect		2.3			2.3		2.5
Income tax effect		0.5			0.5		$ 0.5
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	2.0	2.0	2.0	2.1	2.0	2.1
Impact of ASU 2018-02	0.0
Net amount reclassified to net income (loss)		(0.0)		(0.0)	(0.1)	(0.1)
Balance, end		2.0		2.1	2.0	2.1
Accumulated other comprehensive loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	(98.7)	(98.7)	$ (98.7)	(88.7)	(98.7)	(91.7)
Impact of ASU 2018-02	$ (1.3)
Net amount reclassified to net income (loss)		0.7		0.1	2.0	3.1
Balance, end		$ (98.0)		$ (88.7)	$ (98.0)	$ (88.7)

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The tax effect of AOCI as reported on the balance sheet.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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