STOCKHOLDERS' EQUITY - Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	$ 932.3	$ 861.0	$ 1,222.5
Current year change	49.1	27.3	(42.7)
Total stockholders' equity, End of Period	921.5	932.3	861.0
Cumulative Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	(208.2)	(225.6)	(144.7)
Current year change	63.0	17.4	(80.9)
Total stockholders' equity, End of Period	(145.2)	(208.2)	(225.6)
Derivative Hedging Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	(0.8)	(4.4)	2.1
Current year change	(5.2)	3.6	(6.5)
Total stockholders' equity, End of Period	(6.0)	(0.8)	(4.4)
Debt and Equity Securities Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	2.6	0.8	4.3
Current year change	(1.4)	1.8	(3.5)
Total stockholders' equity, End of Period	1.2	2.6	0.8
Pension Liability Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	(51.1)	(55.6)	(101.2)
Current year change	(7.3)	4.5	45.6
Total stockholders' equity, End of Period	(58.4)	(51.1)	(55.6)
Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total stockholders' equity, Beginning of Period	(257.5)	(284.8)	(239.5)
Current year change	49.1	27.3	(45.3)
Total stockholders' equity, End of Period	$ (208.4)	$ (257.5)	$ (284.8)