Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net sales	$ 251.9	$ 248.7
Cost of goods sold	164.4	157.4
Gross profit	87.5	91.3
Selling, general and administrative expenses	54.4	34.8
Equity earnings from joint venture	(21.0)	(19.5)
Operating income	54.1	76.0
Interest expense	5.7	6.7
Other non-operating (income) expense, net	(1.3)	369.4
Earnings (loss) from continuing operations before income taxes	49.7	(300.1)
Income tax expense (benefit)	12.2	(77.5)
Earnings (loss) from continuing operations	37.5	(222.6)
(Loss) from disposal of discontinued businesses, net of tax expense (benefit) of $1.7 and ($1.4)	(2.1)	(3.6)
Net (loss) from discontinued operations	(2.1)	(3.6)
Net earnings (loss)	35.4	(226.2)
Other comprehensive income, net of tax:
Foreign currency translation adjustments	0.6	(2.1)
Derivative gain (loss), net	3.8	(11.8)
Pension and postretirement adjustments	0.2	288.3
Total other comprehensive income	4.6	274.4
Total comprehensive income	$ 40.0	$ 48.2
Earnings (loss) per share of common stock, continuing operations:
Basic	$ 0.78	$ (4.64)
Diluted	0.78	(4.64)
(Loss) per share of common stock, discontinued operations:
Basic	(0.04)	(0.07)
Diluted	(0.04)	(0.07)
Net earnings (loss) per share of common stock:
Basic	0.74	(4.71)
Diluted	$ 0.74	$ (4.71)
Average number of common shares outstanding:
Basic	47.8	48.0
Diluted	48.0	48.0