Goodwill - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2024 USD ($) reporting_unit	Mar. 31, 2023 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2023 USD ($) reporting_unit
Goodwill [Line Items]
Number of reporting units | reporting_unit					3
Goodwill	$ 227.3		$ 227.3		$ 241.4
Goodwill impairment	14.1	$ 0.0	14.1	$ 0.0
Accumulated goodwill impairment losses	$ 148.7		$ 148.7		$ 134.6
Special Alloy Operations Reporting Unit
Goodwill [Line Items]
Percentage of goodwill	86.00%		86.00%		81.00%
Performance Engineered Products
Goodwill [Line Items]
Number of reporting units | reporting_unit	2				2
Goodwill	$ 31.8		$ 31.8		$ 45.9
Goodwill impairment			14.1
Accumulated goodwill impairment losses	148.7		148.7
Performance Engineered Products | Dynamet
Goodwill [Line Items]
Goodwill	31.8		31.8		31.8
Performance Engineered Products | Latrobe Distribution
Goodwill [Line Items]
Goodwill					14.1
Specialty Alloys Operations
Goodwill [Line Items]
Goodwill	$ 195.5		195.5		$ 195.5
Goodwill impairment			$ 0.0