EQUITY - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 1,577.5	$ 2,343.1
Unrealized (losses) gains, arising during the period	(10.3)
Taxes on unrealized gains (losses), arising during the period	(14.0)
Amounts reclassified out of AOCI during the period, gross	14.4
Amounts reclassified out of AOCI during the period, taxes	(1.2)
Noncontrolling interest	(3.3)
Balance at end of period	1,431.2	1,577.5
Accumulated other comprehensive loss	(441.5)	(427.1)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(427.1)	(71.2)
Balance at end of period	(441.5)	(427.1)
Total Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(68.7)
Balance at end of period	(83.1)	(68.7)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(46.6)
Unrealized (losses) gains, arising during the period	(63.9)
Taxes on unrealized gains (losses), arising during the period	1.3
Amounts reclassified out of AOCI during the period, gross	22.5
Amounts reclassified out of AOCI during the period, taxes	(4.1)
Noncontrolling interest	(3.3)
Balance at end of period	(94.1)	(46.6)
Foreign Currency Derivative Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(22.2)
Unrealized (losses) gains, arising during the period	53.6
Taxes on unrealized gains (losses), arising during the period	(15.3)	(2.8)
Amounts reclassified out of AOCI during the period, gross	(7.9)
Amounts reclassified out of AOCI during the period, taxes	2.8
Noncontrolling interest	0.0
Balance at end of period	11.0	(22.2)
Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	0.1
Unrealized (losses) gains, arising during the period	0.0
Taxes on unrealized gains (losses), arising during the period	0.0
Amounts reclassified out of AOCI during the period, gross	(0.2)
Amounts reclassified out of AOCI during the period, taxes	0.1
Noncontrolling interest	0.0
Balance at end of period	$ 0.0	$ 0.1
AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive loss			$ 358.4