SUPPLEMENTAL GUARANTOR FINANCIAL INFORMATION (Statements of Comprehensive Income (Loss))(Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net income (loss)	$ 195.1	$ 52.7	$ 274.6	$ 60.2
Foreign currency translation adjustments, net	(2.0)	9.8	(15.7)	31.7
Unrealized (losses) gains on derivative contracts, net	(3.6)	1.3	(6.1)	(4.4)
Amortization of prior service costs and actuarial losses, net	7.5	4.3	21.0	12.7
Total other comprehensive income (loss), net of tax	1.9	15.4	(0.8)	40.0
Comprehensive income (loss)	197.0	68.1	273.8	100.2
Parent Guarantor
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net income (loss)	195.1	52.7	274.6	60.2
Foreign currency translation adjustments, net	0.0	0.0	0.0	0.0
Unrealized (losses) gains on derivative contracts, net	(3.6)	1.3	(6.1)	(4.4)
Amortization of prior service costs and actuarial losses, net	6.6	3.6	19.7	11.6
Total other comprehensive income (loss), net of tax	3.0	4.9	13.6	7.2
Comprehensive income (loss)	198.1	57.6	288.2	67.4
Issuer
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net income (loss)	57.0	28.7	107.3	15.9
Foreign currency translation adjustments, net	0.0	0.0	0.0	0.0
Unrealized (losses) gains on derivative contracts, net	0.0	0.0	0.0	0.0
Amortization of prior service costs and actuarial losses, net	0.0	0.0	0.0	0.0
Total other comprehensive income (loss), net of tax	0.0	0.0	0.0	0.0
Comprehensive income (loss)	57.0	28.7	107.3	15.9
Subsidiary Non-Guarantor
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net income (loss)	150.4	80.5	337.3	151.0
Foreign currency translation adjustments, net	(2.0)	9.8	(15.7)	31.7
Unrealized (losses) gains on derivative contracts, net	0.0	0.0	0.0	0.0
Amortization of prior service costs and actuarial losses, net	0.9	0.7	1.3	1.1
Total other comprehensive income (loss), net of tax	(1.1)	10.5	(14.4)	32.8
Comprehensive income (loss)	149.3	91.0	322.9	183.8
Eliminations
Supplemental Guarantor Financial Information Statements Of Comprehensive Income (Loss) [Line Items]
Net income (loss)	(207.4)	(109.2)	(444.6)	(166.9)
Foreign currency translation adjustments, net	0.0	0.0	0.0	0.0
Unrealized (losses) gains on derivative contracts, net	0.0	0.0	0.0	0.0
Amortization of prior service costs and actuarial losses, net	0.0	0.0	0.0	0.0
Total other comprehensive income (loss), net of tax	0.0	0.0	0.0	0.0
Comprehensive income (loss)	$ (207.4)	$ (109.2)	$ (444.6)	$ (166.9)