Derivatives and Hedging Activities - Schedule of Changes in AOCI Associated with Derivative Hedging Activities (Details) - Cash flow hedges - USD ($) $ in Millions	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	$ (2.3)	$ (21.8)	$ (28.5)
Current period changes in fair value, net of tax	26.9	5.8	(20.8)
Reclassification to earnings, net of tax	0.8	13.7	27.5
Balance, ending	$ 23.8	$ (2.3)	$ (21.8)

Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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