SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash	$ 25.7		$ 25.7			$ 35.3
Effective income tax rate (percent)	(7.90%)	36.90%	(211.80%)	69.30%
Decrease in valuation allowance		$ 111.2		$ 111.2
Tax Cuts and Jobs Act of 2017, total income tax provision			$ 15.0
Tax Cuts and Jobs Act of 2017, one-time repatriation tax benefit			370.0
Tax Cuts and Jobs Act of 2017, revaluation of deferred taxes, income tax benefit			300.0
Tax Cuts And Jobs Act Of 2017, incomplete accounting, transition tax for accumulated foreign earnings, provisional income tax expense (benefit), uncertain tax positions			55.0
Gross unrecognized tax benefits	$ 216.3		216.3			257.9
Unrecognized tax benefits that would impact effective tax rate	203.5		203.5
Unrecognized tax benefits, net	214.1		214.1			154.6
Interest and penalties expense	(0.2)	$ (0.6)	1.9	0.4
Gross accrued interest and penalties	13.6		13.6			11.7
Reasonably possible decrease in UTBs (up to)	8.1		8.1
Adjustment due to the adoption of ASU 2016-09						8.3
Payments for employee taxes related to net settlement of equity awards (see Note 2)			3.5	$ 0.0
(Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment due to the adoption of ASU 2016-09						$ 8.3
Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
U.S. federal statutory rate (percent)					28.00%
Foreign Tax Authority
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction of gross unrecognized tax benefits	43.0		43.0
Reduction in unrecognized tax benefits, income tax expense	41.8		41.8
Reduction in unrecognized tax benefits, interest	$ 1.2		$ 1.2