ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		$ (770.4)	$ (614.8)
Other comprehensive income	[1]	(5.8)	23.3	[2]
Ending balance		(1,056.8)	(770.4)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(228.4)	(251.7)
Other comprehensive income	[1]	(5.8)	23.3
Ending balance		(234.2)	(228.4)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(15.0)	(24.0)
Other comprehensive income		(9.4)	9.0
Ending balance		(24.4)	(15.0)
Other comprehensive income (loss), tax expense (benefit)		0.1	0.4
Actuarial (Loss) Gain on Post-retirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(212.4)	(224.4)
Other comprehensive income		2.9	12.0
Ending balance		(209.5)	(212.4)
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		8.4	8.1
Other comprehensive income (loss), tax expense (benefit)		(1.0)	(1.6)
Actuarial (Loss) Gain on Post-retirement Benefits - Pension re-measurement
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income		(5.5)	1.8
Other comprehensive income (loss), tax expense (benefit)		2.5	0.3
Deferred Gain (Loss) - Hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(0.7)	(3.0)
Other comprehensive income		0.7	2.3
Ending balance		0.0	(0.7)
Other comprehensive income (loss), tax expense (benefit)		0.5	1.4
Actuarial (Loss) Gain on Post-retirement Benefits - Curtailment (Losses) Gains
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income			2.1
Other comprehensive income (loss), tax expense (benefit)			(0.3)
Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(0.3)	(0.3)
Other comprehensive income		0.0	0.0
Ending balance		$ (0.3)	$ (0.3)

[1] See Note 16, "Accumulated Other Comprehensive Loss," regarding the changes in the accumulated balances for each component of other comprehensive loss during 2018 and 2017.

[2] 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.