RESTRUCTURING COSTS - Restructuring Costs by Type (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 30.1	$ 4.8
Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	31.2	$ 7.6	$ 156.6
Cumulative through September 30, 2020	187.8
Severance and Employee Benefits | Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	31.3		151.2
Cumulative through September 30, 2020	182.5
Fixed Asset Write-offs | Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(0.4)		(1.1)
Cumulative through September 30, 2020	(1.5)
Other Exit Costs | Transformation Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.3		$ 6.5
Cumulative through September 30, 2020	$ 6.8