Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Changes in the carrying amount of goodwill by reportable segment
Goodwill gross, beginning balance			$ 376.0
Accumulated impairment losses, beginning balance			(134.6)
Total goodwill net, beginning balance			241.4
Impairment	$ (14.1)	$ 0.0	(14.1)	$ 0.0
Goodwill gross, ending balance	376.0		376.0
Accumulated impairment losses, ending balance	(148.7)		(148.7)
Total goodwill net, ending balance	227.3		227.3
Specialty Alloys Operations
Changes in the carrying amount of goodwill by reportable segment
Total goodwill net, beginning balance			195.5
Impairment			0.0
Total goodwill net, ending balance	195.5		195.5
Performance Engineered Products
Changes in the carrying amount of goodwill by reportable segment
Total goodwill net, beginning balance			45.9
Impairment			(14.1)
Accumulated impairment losses, ending balance	(148.7)		(148.7)
Total goodwill net, ending balance	$ 31.8		$ 31.8