Condensed Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		51 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020
Income Statement [Abstract]
Sales	$ 1,241.2		$ 1,592.9		$ 2,666.3	$ 3,146.3
Operating expenses:
Cost of goods sold	1,235.7		1,463.7		2,609.9	2,811.0
Selling and administration	99.7		97.0		196.4	204.0
Restructuring charges	1.7	$ 1.7	3.8	$ 4.0	3.4	7.8	$ 243.7
Other operating income	0.1		0.1		0.1	0.2
Operating (loss) income	(95.8)		28.5		(143.3)	123.7
Interest expense	69.4		57.9		132.5	115.3
Interest income	0.2		0.3		0.3	0.5
Non-operating pension income	(4.9)		(4.2)		(9.5)	(8.1)
Other income	0.0		0.0		0.0	11.2
Income (loss) before taxes	(160.1)		(24.9)		(266.0)	28.2
Income tax (benefit) provision	(40.0)		(4.9)		(65.9)	6.5
Net (loss) income	$ (120.1)	$ (80.0)	$ (20.0)	$ 41.7	$ (200.1)	$ 21.7
Net (loss) income per common share:
Basic	$ (0.76)		$ (0.12)		$ (1.27)	$ 0.13
Diluted	$ (0.76)		$ (0.12)		$ (1.27)	$ 0.13
Average common shares outstanding:
Basic	157.9		164.6		157.8	164.8
Diluted	157.9		164.6		157.8	165.7