SHARE-BASED COMPENSATION PLANS - Restricted Share Units Narrative (Details) $ / shares in Units, $ in Millions				12 Months Ended
	Oct. 14, 2020	Oct. 01, 2018 employee	Sep. 30, 2018	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, number of employees with outstanding awards | employee		560
Common stock, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Share-based compensation expense | $				$ 28.4	$ 42.2	$ 11.7
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $				$ 18.3
Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in dollars per share) | $ / shares				$ 0.01
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years		5 years
Granted (in shares) | shares				38,400,000
Share-based compensation expense | $				$ 26.1	18.2	11.8
Total intrinsic value of restricted shares vested and settled | $				32.9	$ 30.3	$ 11.1
Restricted Stock Units | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized share-based compensation expense | $				$ 273.2
Restricted Stock Units | Common Class A | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value (in dollars per share) | $ / shares				$ 0.01
Restricted Stock Units | Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
Award vesting rights, percentage	33.30%	60.00%
Restricted Stock Units | Tranche One | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares to be granted for restricted stock awards (in shares) | shares				10,000,000
Total unrecognized share-based compensation expense | $				$ 168.3
Restricted Stock Units | Tranche One | Chief Executive Officer | Cottage Holdco B.V.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares to be contributed by related party (in shares) | shares				10,000,000
Period for shares to be contributed by related party				60 days
Restricted Stock Units | Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Award vesting rights, percentage	33.30%	20.00%
Restricted Stock Units | Tranche Two | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares to be granted for restricted stock awards (in shares) | shares				10,000,000
Total unrecognized share-based compensation expense | $				$ 89.9
Restricted Stock Units | Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		5 years
Award vesting rights, percentage	33.30%	20.00%
Restricted Stock Units | Tranche Three | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares to be granted for restricted stock awards (in shares) | shares				10,000,000
Total unrecognized share-based compensation expense | $				$ 15.0
Restricted Stock Units | Tranche Three | Chief Executive Officer | Cottage Holdco B.V.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares to be contributed by related party (in shares) | shares				5,000,000
Omnibus Long-Term Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares				38,100,000	6,200,000	6,900,000
2007 Stock Plan for Directors | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares				300,000	100,000	100,000