ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of Accumulated Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			$ (770.4)
Ending balance	$ (980.7)		(980.7)
Deferred gain - hedging
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(0.7)
Ending balance	0.0		0.0
Deferred gain - hedging | Interest rate swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.1)	$ (2.4)	(0.7)	$ (3.0)
Ending balance	0.0	(1.8)	0.0	(1.8)
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	0.1	0.6	(0.7)	1.2
Other Comprehensive Income (Loss), Tax [Abstract]
Reclassifications into earnings - tax benefit	$ 0.3	$ 0.3	$ 0.5	$ 0.7