STOCKHOLDERS' EQUITY AND EQUITY INSTRUMENTS (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 529.6	$ 540.2	$ 694.6
Other comprehensive income (loss) before reclassifications	(108.8)	20.6
Amounts reclassified from accumulated other comprehensive loss	(2.4)	(1.8)
Net current period other comprehensive income (loss)	(111.2)	18.8
Reclassification of stranded tax out of AOCI to retained earnings			0.0
Ending balance	387.0	529.6	540.2
Gains and (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(0.6)	(0.7)
Other comprehensive income (loss) before reclassifications	3.9	2.2
Amounts reclassified from accumulated other comprehensive loss	(3.1)	(2.1)
Net current period other comprehensive income (loss)	0.8	0.1
Ending balance	0.2	(0.6)	(0.7)
Defined Benefit Pension
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(6.9)	(4.5)
Other comprehensive income (loss) before reclassifications	(3.2)	(2.7)
Amounts reclassified from accumulated other comprehensive loss	0.7	0.3
Net current period other comprehensive income (loss)	(2.5)	(2.4)
Ending balance	(9.4)	(6.9)	(4.5)
Foreign Currency
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(184.6)	(205.7)
Other comprehensive income (loss) before reclassifications	(109.5)	21.1
Amounts reclassified from accumulated other comprehensive loss	0.0	0.0
Net current period other comprehensive income (loss)	(109.5)	21.1
Ending balance	(294.1)	(184.6)	(205.7)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(192.1)	(210.9)	(77.9)
Reclassification of stranded tax out of AOCI to retained earnings			(0.2)
Ending balance	$ (303.3)	$ (192.1)	$ (210.9)