RESTRUCTURING COSTS - Summary of Global Initiative Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 11.2	$ 7.4
Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	9.8	$ 0.0	$ 364.2
Restructuring costs incurred to date	374.0
Severance and Employee Benefits | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	0.4		333.9
Restructuring costs incurred to date	334.3
Third-Party Contract Terminations | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	8.0		22.4
Restructuring costs incurred to date	30.4
Fixed Asset Write-offs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	0.0		4.6
Restructuring costs incurred to date	4.6
Other Exit Costs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	1.4		$ 3.3
Restructuring costs incurred to date	$ 4.7