ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	[1]	Sep. 30, 2018		Sep. 30, 2017	[1]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					$ (770.4)
Other comprehensive income		$ (2.6)	$ 1.4		(5.1)	[2]	$ 15.8
Ending balance		(988.2)			(988.2)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(228.4)
Other comprehensive income	[2]				(5.1)
Ending balance		(233.5)			(233.5)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(15.0)
Other comprehensive income					(12.3)
Ending balance		(27.3)			(27.3)
Actuarial (Loss) Gain on Post-retirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(212.4)
Other comprehensive income					6.5
Ending balance		(205.9)			(205.9)
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					6.5
Other comprehensive income (loss), tax benefit (expense)					(0.8)
Deferred Gain (Loss) - Hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(0.7)
Other comprehensive income					0.7
Ending balance		0.0			0.0
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					0.7
Other comprehensive income (loss), tax benefit (expense)					0.5
Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(0.3)
Other comprehensive income					0.0
Ending balance		$ (0.3)			$ (0.3)

[1] Adjusted as a result of the adoption of certain accounting pronouncements during 2018. See Note 1, "Description of Business and Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements," for details of these adjustments.

[2] See Note 12, "Accumulated Other Comprehensive Loss," regarding the changes in the accumulated balances for each component of other comprehensive loss during the nine months ended September 30, 2018.