RESTRUCTURING COSTS - Summary of Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 21.5	$ 21.7	$ 37.0	$ 32.9
Cumulative through December 31, 2018	(0.1)		(0.1)
Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs	22.2	$ 15.1	28.7	$ 24.9	$ 106.5	$ 364.2
Cumulative through December 31, 2018	499.4		499.4
2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs			8.8		68.4
Cumulative through December 31, 2018	77.2		77.2
Severance and Employee Benefits | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs			1.6		67.5	333.9
Cumulative through December 31, 2018	403.0		403.0
Severance and Employee Benefits | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs			7.9		63.5
Cumulative through December 31, 2018	71.4		71.4
Third-Party Contract Terminations | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs			1.8		19.3	22.4
Cumulative through December 31, 2018	43.5		43.5
Third-Party Contract Terminations | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs			0.0		0.2
Cumulative through December 31, 2018	0.2		0.2
Fixed Asset Write-offs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs			23.8		14.3	4.6
Cumulative through December 31, 2018	42.7		42.7
Fixed Asset Write-offs | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs			0.0		1.3
Cumulative through December 31, 2018	1.3		1.3
Other Exit Costs | Global Integration Activities
Restructuring Cost and Reserve [Line Items]
Restructuring costs			1.5		5.4	$ 3.3
Cumulative through December 31, 2018	10.2		10.2
Other Exit Costs | 2018 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs			0.9		$ 3.4
Cumulative through December 31, 2018	$ 4.3		$ 4.3