RESTRUCTURING CHARGES - Restructuring Reserve (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Total Restructuring Charges
Restructuring Reserve [Roll Forward]
Liability Balance at period start	$ 13.8
Expense, Net	22.8
Cash Utilized, Net	(33.1)
Liability Balance at period end	3.5
RGGA:
Restructuring Reserve [Roll Forward]
Expense, Net	28.0
RGGA: | Total Restructuring Charges
Restructuring Reserve [Roll Forward]
Liability Balance at period start	12.6
Expense, Net	22.8
Cash Utilized, Net	(32.8)
Liability Balance at period end	2.6
RGGA: | Employee severance and other personnel benefits
Restructuring Reserve [Roll Forward]
Liability Balance at period start	12.6
Expense, Net	3.5
Cash Utilized, Net	(13.5)
Liability Balance at period end	2.6
RGGA: | Other Costs
Restructuring Reserve [Roll Forward]
Liability Balance at period start	0.0
Expense, Net	19.3
Cash Utilized, Net	(19.3)
Liability Balance at period end	0.0
Other restructuring initiatives: | Total Restructuring Charges
Restructuring Reserve [Roll Forward]
Liability Balance at period start	1.2
Expense, Net	0.0
Cash Utilized, Net	(0.3)
Liability Balance at period end	0.9
Other restructuring initiatives: | Employee severance and other personnel benefits
Restructuring Reserve [Roll Forward]
Liability Balance at period start	1.2
Expense, Net	0.0
Cash Utilized, Net	(0.3)
Liability Balance at period end	$ 0.9