SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash	$ 56.2			$ 56.2		$ 43.7
Effective income tax rate, percentage	68.20%		27.80%	156.90%	40.40%
Effective income tax rate reconciliation, resolution of foreign uncertain tax positions	$ 16.8
Effective income tax rate reconciliation, preliminary income tax benefit		$ 220.5
Gross unrecognized tax benefits	325.1			$ 325.1		277.9
Unrecognized tax benefits that would impact effective tax rate	200.1			200.1
Unrecognized tax benefits, net	222.2			222.2		170.7
Interest and penalties expense	(0.2)		$ (1.3)	1.0	$ 0.1
Gross accrued interest and penalties	22.0			22.0		19.3
Reasonably possible decrease in UTBs (up to)	38.4			38.4
Cumulative effect in period of adoption	(3,295.3)	(3,425.6)	(4,481.6)	(3,295.3)	(4,481.6)	(3,228.8)	$ (4,464.3)	$ (4,593.4)
(Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect in period of adoption	$ 5,585.2	$ 5,332.9	$ 4,510.7	$ 5,585.2	$ 4,510.7	5,548.6	$ 4,489.6	$ 4,541.2
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect in period of adoption						5.7
Cumulative Effect, Period of Adoption, Adjustment | (Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect in period of adoption						5.7
Cumulative Effect, Period of Adoption, Adjustment | Adjustment due to the adoption of ASU No. 2016-13 | (Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect in period of adoption						5.7
Cumulative Effect, Period Of Adoption, Pre-Tax Adjustment | Adjustment due to the adoption of ASU No. 2016-13 | (Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect in period of adoption						$ 6.6