COMPREHENSIVE INCOME (LOSS) - BALANCES INCLUDED IN AOCI, NET OF TAX, IN THE CONSOLIDATED BALANCE SHEETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 5,094.9	$ 5,133.0
Total other comprehensive loss, net of tax	(112.2)	(58.4)
Ending Balance	4,690.2	5,109.5
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(599.7)	(478.7)
Other comprehensive (loss) income before reclassifications and tax impact	(107.7)	(49.0)
Tax (expense) benefit	(6.1)	(10.8)
Other comprehensive (loss) income, net of tax, before reclassifications	(113.8)	(59.8)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	1.3	1.1
Total other comprehensive loss, net of tax	(112.5)	(58.7)
Ending Balance	(712.2)	(537.4)
Foreign Currency Translation Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(368.3)	(284.7)
Other comprehensive (loss) income before reclassifications and tax impact	(116.7)	(59.9)
Tax (expense) benefit	(2.0)	(1.4)
Other comprehensive (loss) income, net of tax, before reclassifications	(118.7)	(61.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0.0	0.0
Total other comprehensive loss, net of tax	(118.7)	(61.3)
Ending Balance	(487.0)	(346.0)
Gain (Loss) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(10.6)	0.6
Other comprehensive (loss) income before reclassifications and tax impact	(15.7)	(7.7)
Tax (expense) benefit	4.0	2.4
Other comprehensive (loss) income, net of tax, before reclassifications	(11.7)	(5.3)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(0.3)	0.2
Total other comprehensive loss, net of tax	(12.0)	(5.1)
Ending Balance	(22.6)	(4.5)
Gain (Loss) on Net Investment Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(100.7)	(111.4)
Other comprehensive (loss) income before reclassifications and tax impact	24.7	18.6
Tax (expense) benefit	(8.1)	(11.8)
Other comprehensive (loss) income, net of tax, before reclassifications	16.6	6.8
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0.0	0.0
Total other comprehensive loss, net of tax	16.6	6.8
Ending Balance	(84.1)	(104.6)
Pension Liability Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(120.1)	(83.2)
Other comprehensive (loss) income before reclassifications and tax impact	0.0	0.0
Tax (expense) benefit	0.0	0.0
Other comprehensive (loss) income, net of tax, before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	1.6	0.9
Total other comprehensive loss, net of tax	1.6	0.9
Ending Balance	$ (118.5)	$ (82.3)