Supplemental Balance Sheet Information - Prepaid and Other Assets (Detail) - USD ($) $ in Millions		Mar. 31, 2017	Jun. 30, 2016
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expense, Current		$ 22.4	$ 29.3
Spare parts supplies		11.7	10.8
Short-term Investments		0.0	7.0
Other Prepaid Expense, Current	[1]	0.0	6.8
Available-for-sale Securities, Current		27.6	0.0
Other current assets		29.0	35.1
Prepaid expenses and other		$ 90.7	$ 89.0

[1] The Company transferred certain intellectual property assets between jurisdictions in the year ended June 30, 2016, resulting in a deferred tax charge which will be amortized over the remaining 10-year useful life of the assets. The Company adopted ASU 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory effective July 1, 2016 and subsequently adjusted the long-term tax asset. Refer to Note 1 for further information.