Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jun. 30, 2018
Deferred tax assets:
Pensions	$ 86.9	$ 66.8
Postretirement provisions	35.7	33.7
Net operating loss carryforwards	28.8	26.5
Derivatives and hedging activities	4.1	0.0
Other	32.1	29.4
Gross deferred tax assets	187.6	156.4
Valuation allowances	(24.6)	(23.9)
Total deferred tax assets	163.0	132.5
Deferred tax liabilities:
Depreciation	(249.5)	(235.2)
Intangible assets	(11.3)	(11.9)
Inventories	(36.1)	(30.5)
Derivatives and hedging activities	(0.3)	(8.7)
Other	(4.3)	(3.5)
Total deferred tax liabilities	(301.5)	(289.8)
Deferred tax liabilities, net	$ (138.5)	$ (157.3)