ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of Accumulated Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (770.4)
Ending balance	(855.7)
Deferred gain - hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.7)
Ending balance	(0.1)
Deferred gain - hedging | Interest rate swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.7)	$ (3.0)
Ending balance	(0.1)	(2.4)
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	0.6	0.6
Other Comprehensive Income (Loss), Tax [Abstract]
Reclassifications into earnings - tax benefit	$ 0.2	$ 0.4