RESTRUCTURING COSTS - Summary of Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 15.5	$ 11.2
Cumulative through September 30, 2018	(0.1)
Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	6.5	$ 9.8	$ 106.5	$ 364.2
Cumulative through September 30, 2018	477.2
2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	9.1		68.4
Cumulative through September 30, 2018	77.5
Severance and Employee Benefits | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4.1		67.5	333.9
Cumulative through September 30, 2018	405.5
Severance and Employee Benefits | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	8.4		63.5
Cumulative through September 30, 2018	71.9
Third-Party Contract Terminations | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1.0		19.3	22.4
Cumulative through September 30, 2018	42.7
Third-Party Contract Terminations | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0		0.2
Cumulative through September 30, 2018	0.2
Fixed Asset Write-offs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0		14.3	4.6
Cumulative through September 30, 2018	18.9
Fixed Asset Write-offs | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0		1.3
Cumulative through September 30, 2018	1.3
Other Exit Costs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1.4		5.4	$ 3.3
Cumulative through September 30, 2018	10.1
Other Exit Costs | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.7		$ 3.4
Cumulative through September 30, 2018	$ 4.1