ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of Accumulated 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)
Ending balance	(1,056.8)	(770.4)
Deferred gain - hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.7)	(3.0)
Ending balance	0.0	(0.7)
Deferred gain - hedging | Interest rate swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.7)	(3.0)
Ending balance	0.0	(0.7)
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	0.7	2.3
Other Comprehensive Income (Loss), Tax [Abstract]
Reclassifications into earnings - tax benefit	$ 0.5	$ 1.4