Consolidated Statements of Operations - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 1,502,400,000	$ 2,355,700,000	$ 2,189,100,000
Cost of sales	1,262,700,000	1,715,300,000	1,608,300,000
Gross margin	239,700,000	640,400,000	580,800,000
Selling, general and administrative expenses	121,100,000	158,700,000	146,000,000.0
Research and technology expenses	46,600,000	56,500,000	55,900,000
Other operating expense	57,900,000	0	7,700,000
Operating income	14,100,000	425,200,000	371,200,000
Interest expense, net	41,800,000	45,500,000	37,700,000
(Loss) income before income taxes, and equity in earnings	(27,700,000)	379,700,000	333,500,000
Income tax (benefit) expense	(61,000,000.0)	76,800,000	62,500,000
Income before equity in earnings	33,300,000	302,900,000	271,000,000.0
(Loss) equity in earnings from affiliated companies	(1,600,000)	3,700,000	5,600,000
Net income	$ 31,700,000	$ 306,600,000	$ 276,600,000
Basic net income per common share:	$ 0.38	$ 3.61	$ 3.15
Diluted net income per common share:	$ 0.38	$ 3.57	$ 3.11
Weighted-average common shares:
Basic	83.8	84.9	87.9
Diluted	84.0	85.8	89.0