Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2016	Jun. 30, 2015
Deferred tax assets:
Pensions	$ 193.5	$ 125.1
Postretirement provisions	51.0	48.9
Net operating loss carryforwards	20.5	20.3
Derivatives and hedging activities	14.8	18.5
Other	37.4	32.6
Gross deferred tax assets	317.2	245.4
Valuation allowances	(17.7)	(17.5)
Total deferred tax assets	299.5	227.9
Deferred tax liabilities:
Depreciation	(333.0)	(321.2)
Intangible assets	(20.4)	(26.1)
Inventories	(27.4)	(17.6)
Other	(12.9)	(6.2)
Total deferred tax liabilities	(393.7)	(371.1)
Deferred tax liabilities	$ (94.2)	$ (143.2)