RESTRUCTURING - Rollforward of Restructuring Liability (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended	18 Months Ended
	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2021
Restructuring Reserve [Roll Forward]
Balance as of beginning of period	$ 0.0	$ 44.5	$ 0.0
Accrued charges	94.1	78.0
Payments	(49.6)	(87.7)
Balance as of end of period	44.5	34.8	34.8
Non-cash charges	24.9	22.5	47.4
Cumulative charges incurred through December 31, 2021		219.5	219.5
Employee Compensation
Restructuring Reserve [Roll Forward]
Balance as of beginning of period	0.0	44.5	0.0
Accrued charges	85.0	63.7
Payments	(40.5)	(75.2)
Balance as of end of period	44.5	33.0	33.0
Non-cash charges	19.5	13.7	33.2
Cumulative charges incurred through December 31, 2021		181.9	181.9
Other Expenses
Restructuring Reserve [Roll Forward]
Balance as of beginning of period	0.0	0.0	0.0
Accrued charges	9.1	14.3
Payments	(9.1)	(12.5)
Balance as of end of period	0.0	1.8	1.8
Non-cash charges	$ 5.4	8.8	14.2
Cumulative charges incurred through December 31, 2021		$ 37.6	$ 37.6