SUPPLEMENTAL GUARANTOR FINANCIAL INFORMATION (Statements of Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net (loss) income	$ (80.0)	$ 41.7
Other comprehensive (loss) income net of tax:
Foreign currency translation adjustments, net	(9.0)	(8.3)
Unrealized losses on derivative contracts, net	(17.9)	(3.3)
Amortization of prior service costs and actuarial losses, net	9.2	5.7
Total other comprehensive (loss) income, net of tax	(17.7)	(5.9)
Comprehensive (loss) income	(97.7)	35.8
Parent Guarantor
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net (loss) income	(80.0)	41.7
Other comprehensive (loss) income net of tax:
Foreign currency translation adjustments, net	0.0	0.0
Unrealized losses on derivative contracts, net	(17.9)	(3.3)
Amortization of prior service costs and actuarial losses, net	7.9	5.1
Total other comprehensive (loss) income, net of tax	(10.0)	1.8
Comprehensive (loss) income	(90.0)	43.5
Issuer
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net (loss) income	(54.4)	25.2
Other comprehensive (loss) income net of tax:
Foreign currency translation adjustments, net	0.0	0.0
Unrealized losses on derivative contracts, net	0.0	0.0
Amortization of prior service costs and actuarial losses, net	0.0	0.0
Total other comprehensive (loss) income, net of tax	0.0	0.0
Comprehensive (loss) income	(54.4)	25.2
Subsidiary Non-Guarantor
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net (loss) income	(25.2)	90.0
Other comprehensive (loss) income net of tax:
Foreign currency translation adjustments, net	(9.0)	(8.3)
Unrealized losses on derivative contracts, net	0.0	0.0
Amortization of prior service costs and actuarial losses, net	1.3	0.6
Total other comprehensive (loss) income, net of tax	(7.7)	(7.7)
Comprehensive (loss) income	(32.9)	82.3
Eliminations
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net (loss) income	79.6	(115.2)
Other comprehensive (loss) income net of tax:
Foreign currency translation adjustments, net	0.0	0.0
Unrealized losses on derivative contracts, net	0.0	0.0
Amortization of prior service costs and actuarial losses, net	0.0	0.0
Total other comprehensive (loss) income, net of tax	0.0	0.0
Comprehensive (loss) income	$ 79.6	$ (115.2)