ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of Accumulated Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (614.8)	[1]	$ (587.5)
Ending balance	(770.4)		(614.8)	[1]
Deferred gain - hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(3.0)		(3.8)
Ending balance	(0.7)		(3.0)
Deferred gain - hedging | Interest rate swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(3.0)		(3.8)
Ending balance	0.7		(3.0)
Deferred gain - hedging | Interest rate swap | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Change in fair value, net of tax			(1.9)
Other Comprehensive Income (Loss), Tax [Abstract]
Change in fair value - tax expense (benefit)			1.1
Deferred gain - hedging | Interest rate swap | Interest Expense | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Reclassifications into earnings, net of tax	2.3		2.7
Other Comprehensive Income (Loss), Tax [Abstract]
Reclassifications into earnings - tax expense (benefit)	$ 1.4		$ (1.6)

[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.