Components of Accumulated Other Comprehensive Loss - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	$ 420.0	$ 451.7	$ 1,251.3	$ 1,431.8
Selling, general and administrative expenses	11.0	11.6	31.7	38.2
Other operating (income) expense - net	(0.2)	(0.1)	0.3	0.4
Income tax effect	0.3	(1.3)	(1.6)	(5.7)
Net of tax	58.2	20.7	87.8	76.0
Reclassification out of accumulated other comprehensive income [Member] | Defined benefit plan and other postretirement liabilities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	0.8	0.8	2.3	1.7
Selling, general and administrative expenses	0.1	(0.3)	0.5	(0.9)
Other operating (income) expense - net	0.5	0.5	1.4	2.1
Income tax effect	(0.2)	(0.3)	(0.8)	(0.8)
Net of tax	1.2	0.7	3.4	2.1
Reclassification out of accumulated other comprehensive income [Member] | Unrealized loss on financial instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	(0.1)	0.0	(0.1)	(0.1)
Income tax effect	0.0	0.0	0.0	0.0
Net of tax	$ (0.1)	$ 0.0	$ (0.1)	$ (0.1)