ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	[1]	Jun. 30, 2018		Jun. 30, 2017	[1]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					$ (770.4)
Other comprehensive income		$ (2.7)	$ 4.5		(2.5)	[2]	$ 14.4
Ending balance		(980.7)			(980.7)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(228.4)
Other comprehensive income	[2]				(2.5)
Ending balance		(230.9)			(230.9)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(15.0)
Other comprehensive income					(7.4)
Ending balance		(22.4)			(22.4)
Actuarial (Loss) Gain on Post-retirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance					(212.4)
Other comprehensive income					4.2
Ending balance		(208.2)			(208.2)
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					4.2
Other comprehensive income (loss), tax benefit (expense)					(0.5)
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 six months ended June 30, 2018.