ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		$ (614.8)	[1]	$ (587.5)		$ (644.1)
Other comprehensive income	[2]	23.3		(6.4)		(2.1)
Ending balance		(770.4)		(614.8)	[1]	(587.5)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(251.7)		(245.3)		(243.2)
Other comprehensive income	[2]	23.3		(6.4)		(2.1)
Ending balance		(228.4)		(251.7)		(245.3)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(24.0)		(23.5)		(5.4)
Other comprehensive income		9.0		(0.5)		(18.1)
Ending balance		(15.0)		(24.0)		(23.5)
Other comprehensive income (loss), tax benefit (expense)		0.4		(1.1)		5.1
Actuarial (Loss) Gain on Post-retirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(224.4)		(217.7)		(235.6)
Other comprehensive income		12.0		(6.7)		17.6
Ending balance		(212.4)		(224.4)		(217.7)
Actuarial (Loss) Gain on Post-retirement Benefits - Amortization of pension related costs
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income		8.1		7.6		7.2
Other comprehensive income (loss), tax benefit (expense)		(1.6)		(1.3)		(1.3)
Actuarial (Loss) Gain on Post-retirement Benefits - Net gain (loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income		1.8		(14.3)		(6.9)
Other comprehensive income (loss), tax benefit (expense)		0.3		4.1		3.3
Accumulated Defined Benefit Plans Adjustment, Settlement Attributable to Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income						17.3
Other comprehensive income (loss), tax benefit (expense)						(3.7)
Deferred Gain (Loss) - Hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(3.0)		(3.8)		(2.2)
Other comprehensive income		2.3		0.8		(1.6)
Ending balance		(0.7)		(3.0)		(3.8)
Other comprehensive income (loss), tax benefit (expense)				(0.5)		1.0
Deferred Gain (Loss) - Hedging - amortization of deferred gains (losses) related to the de-designated 2013 Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income		2.3
Other comprehensive income (loss), tax benefit (expense)		1.4
Accumulated Defined Benefit Plans Adjustment, Curtailment Gain Attributable to Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income		2.1
Other comprehensive income (loss), tax benefit (expense)		(0.3)
Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(0.3)		(0.3)		(0.3)
Other comprehensive income		0.0		0.0		0.0
Ending balance		$ (0.3)		$ (0.3)		$ (0.3)

[1] Adjusted as a result of the adoption of certain accounting pronouncements as of December 31, 2017. See Note 1, "Description of Business and Summaryof Significant Accounting Policies - Recently Adopted Accounting Pronouncements," for details of these adjustments.

[2] See Note 17, "Accumulated Other Comprehensive Loss," regarding the changes in the accumulated balances for each component of other comprehensive loss during 2017, 2016 and 2015.