SUPPLEMENTAL GUARANTOR FINANCIAL INFORMATION (Statements of Operations) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		55 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019
Supplemental Guarantor Financial Information Statement of Operations [Line Items]
Sales	$ 1,592.9		$ 1,728.4		$ 3,146.3	$ 3,438.7
Operating expenses:
Cost of goods sold	1,463.7		1,460.7		2,811.0	2,989.4
Selling and administration	97.0		110.3		204.0	210.8
Restructuring charges	3.8	$ 4.0	6.4	$ 4.0	7.8	10.4	$ 189.8
Acquisition-related costs	0.0		0.3		0.0	0.6
Other operating (loss) income	0.1		0.0		0.2	8.1
Operating (loss) income	(28.5)		(150.7)		(123.7)	(235.6)
Losses of non-consolidated affiliates	0.0		(21.1)		0.0	(20.6)
Equity income (loss) in subsidiaries	0.0		0.0		0.0	0.0
Interest expense	57.9		61.1		115.3	124.8
Interest income	0.3		0.4		0.5	0.8
Non-operating pension income (expense)	4.2		5.4		8.1	10.8
Other income	0.0		0.0		11.2	0.0
Income (loss) before taxes	(24.9)		74.3		28.2	101.8
Income tax (benefit) provision	(4.9)		15.7		6.5	22.3
Net (loss) income	(20.0)	$ 41.7	58.6	$ 20.9	21.7	79.5
Parent Guarantor
Supplemental Guarantor Financial Information Statement of Operations [Line Items]
Sales	324.0		369.5		656.8	722.2
Operating expenses:
Cost of goods sold	309.8		332.9		613.9	644.9
Selling and administration	47.8		53.2		99.6	100.3
Restructuring charges	0.0		0.0		1.4	0.0
Acquisition-related costs			0.3			0.6
Other operating (loss) income	(2.3)		(3.2)		(4.4)	2.6
Operating (loss) income	35.9		20.1		62.5	21.0
Losses of non-consolidated affiliates			(21.1)			(20.6)
Equity income (loss) in subsidiaries	10.9		98.5		73.5	126.9
Interest expense	18.3		18.1		35.7	35.1
Interest income	2.0		1.9		2.6	2.9
Non-operating pension income (expense)	5.7		6.7		11.1	13.4
Other income					11.2
Income (loss) before taxes	(35.6)		47.8		0.2	66.5
Income tax (benefit) provision	(15.6)		(10.8)		(21.5)	(13.0)
Net (loss) income	(20.0)		58.6		21.7	79.5
Issuer
Supplemental Guarantor Financial Information Statement of Operations [Line Items]
Sales	0.0		0.0		0.0	0.0
Operating expenses:
Cost of goods sold	0.0		0.0		0.0	0.0
Selling and administration	0.0		0.0		0.0	0.0
Restructuring charges	0.0		0.0		0.0	0.0
Acquisition-related costs			0.0			0.0
Other operating (loss) income	0.0		0.0		0.0	0.0
Operating (loss) income	0.0		0.0		0.0	0.0
Losses of non-consolidated affiliates			0.0			0.0
Equity income (loss) in subsidiaries	(8.6)		88.1		44.0	110.3
Interest expense	35.7		37.8		71.8	79.1
Interest income	0.0		0.0		0.0	0.0
Non-operating pension income (expense)	0.0		0.0		0.0	0.0
Other income					0.0
Income (loss) before taxes	(44.3)		50.3		(27.8)	31.2
Income tax (benefit) provision	(8.7)		(9.2)		(17.4)	(19.1)
Net (loss) income	(35.6)		59.5		(10.4)	50.3
Subsidiary Non-Guarantor
Supplemental Guarantor Financial Information Statement of Operations [Line Items]
Sales	1,397.3		1,465.9		2,725.0	2,932.9
Operating expenses:
Cost of goods sold	1,282.3		1,234.8		2,432.6	2,560.9
Selling and administration	49.2		57.1		104.4	110.5
Restructuring charges	3.8		6.4		6.4	10.4
Acquisition-related costs			0.0			0.0
Other operating (loss) income	2.4		3.2		4.6	5.5
Operating (loss) income	(64.4)		(170.8)		(186.2)	(256.6)
Losses of non-consolidated affiliates			0.0			0.0
Equity income (loss) in subsidiaries	0.0		0.0		0.0	0.0
Interest expense	6.5		6.8		11.7	13.7
Interest income	0.9		0.1		1.8	1.0
Non-operating pension income (expense)	(1.5)		(1.3)		(3.0)	(2.6)
Other income					0.0
Income (loss) before taxes	57.3		162.8		173.3	241.3
Income tax (benefit) provision	19.4		35.7		45.4	54.4
Net (loss) income	37.9		127.1		127.9	186.9
Eliminations
Supplemental Guarantor Financial Information Statement of Operations [Line Items]
Sales	(128.4)		(107.0)		(235.5)	(216.4)
Operating expenses:
Cost of goods sold	(128.4)		(107.0)		(235.5)	(216.4)
Selling and administration	0.0		0.0		0.0	0.0
Restructuring charges	0.0		0.0		0.0	0.0
Acquisition-related costs			0.0			0.0
Other operating (loss) income	0.0		0.0		0.0	0.0
Operating (loss) income	0.0		0.0		0.0	0.0
Losses of non-consolidated affiliates			0.0			0.0
Equity income (loss) in subsidiaries	(2.3)		(186.6)		(117.5)	(237.2)
Interest expense	(2.6)		(1.6)		(3.9)	(3.1)
Interest income	(2.6)		(1.6)		(3.9)	(3.1)
Non-operating pension income (expense)	0.0		0.0		0.0	0.0
Other income					0.0
Income (loss) before taxes	(2.3)		(186.6)		(117.5)	(237.2)
Income tax (benefit) provision	0.0		0.0		0.0	0.0
Net (loss) income	$ (2.3)		$ (186.6)		$ (117.5)	$ (237.2)