INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Beginning Balance	$ 10.6	$ 10.3
Increase based on tax positions taken in a prior year	1.5	1.5
Decrease based on tax positions taken in a prior year	(1.5)	(0.1)
Increase based on tax positions taken in the current year	0.2	0.2
Decrease resulting from the lapse of statutes of limitations	(1.8)	(1.3)
Ending Balance	9.0	10.6
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	93.3	65.0
Increase based on tax positions taken in a prior year	10.6	25.9
Decrease based on tax positions taken in a prior year	(21.1)	(1.3)
Increase based on tax positions taken in the current year	11.2	9.3
Decrease resulting from the lapse of statutes of limitations	(9.1)	(5.6)
Ending balance	84.9	93.3
Unrecognized Tax Benefit, Tax Portion [Abstract]
Beginning Balance	82.7	54.7
Increase based on tax positions taken in a prior year	9.1	24.4
Decrease based on tax positions taken in a prior year	(19.6)	(1.2)
Increase based on tax positions taken in the current year	11.0	9.1
Decrease resulting from the lapse of statutes of limitations	(7.3)	(4.3)
Ending Balance	$ 75.9	$ 82.7