Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2016
Deferred tax assets:
Pensions	$ 139.8	$ 193.5
Postretirement provisions	54.4	51.0
Net operating loss carryforwards	23.1	20.5
Derivatives and hedging activities	2.4	14.8
Other	44.8	37.4
Gross deferred tax assets	264.5	317.2
Valuation allowances	(18.5)	(17.7)
Total deferred tax assets	246.0	299.5
Deferred tax liabilities:
Depreciation	(347.5)	(333.0)
Intangible assets	(19.4)	(20.4)
Inventories	(50.1)	(27.4)
Other	(6.2)	(12.9)
Total deferred tax liabilities	(423.2)	(393.7)
Deferred tax liabilities, net	$ (177.2)	$ (94.2)