Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2023	Jun. 30, 2022
Deferred tax assets:
Pensions	$ 39.8	$ 43.2
Postretirement provisions	20.0	26.9
Non-equity compensation	16.0	7.5
Net operating loss carryforwards	22.5	44.5
Tax credit carryforwards	1.2	17.0
Operating lease liability	10.0	10.5
Other	22.3	29.3
Gross deferred tax assets	131.8	178.9
Valuation allowances	(13.6)	(21.3)
Total deferred tax assets	118.2	157.6
Deferred tax liabilities:
Depreciation	(237.6)	(262.9)
Intangible assets	(5.8)	(5.2)
Inventories	(27.4)	(28.9)
Operating lease right-of-use asset	(8.0)	(8.3)
Other	(3.1)	(9.0)
Total deferred tax liabilities	(281.9)	(314.3)
Deferred tax liabilities, net	$ (163.7)	$ (156.7)