RESTRUCTURING COSTS - Restructuring Costs by Type (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 12.4	$ 30.1
Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	12.4	$ 31.2	$ 73.2	$ 156.6
Cumulative through September 30, 2021	242.2
Severance and Employee Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring costs	12.4
Severance and Employee Benefits \| Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			73.4	151.2
Cumulative through September 30, 2021	237.0
Fixed Asset Write-offs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0
Fixed Asset Write-offs \| Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(0.5)	(1.1)
Cumulative through September 30, 2021	(1.6)
Other Exit Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0
Other Exit Costs \| Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			$ 0.3	$ 6.5
Cumulative through September 30, 2021	$ 6.8