Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2025	Jun. 30, 2024
Deferred tax assets:
Pensions	$ 26.3	$ 33.1
Postretirement provisions	11.3	14.4
Non-equity compensation	9.6	9.6
Net operating loss carryforwards	8.3	8.5
Tax credit carryforwards	1.6	2.0
Operating lease liabilities	8.1	8.9
Other	21.0	20.1
Gross deferred tax assets	86.2	96.6
Valuation allowances	(2.6)	(2.4)
Total deferred tax assets	83.6	94.2
Deferred tax liabilities:
Depreciation	198.4	219.6
Intangible assets	2.4	3.2
Inventories	28.3	28.2
Operating lease right-of-use assets	6.4	7.0
Other	3.1	2.8
Total deferred tax liabilities	238.6	260.8
Deferred tax liabilities, net	$ 155.0	$ 166.6