Goodwill and Other Intangible Assets, Net - Schedule of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Changes in the carrying amount of goodwill by reportable segment
Goodwill gross, beginning balance	$ 372.2	$ 373.6
Accumulated impairment losses, beginning balance	(81.8)	(47.2)
Total goodwill net, beginning balance	290.4	326.4
Impairment	(52.8)	(34.6)	$ 0.0
Other	3.8	(1.4)
Goodwill gross, ending balance	376.0	372.2	373.6
Accumulated impairment losses, ending balance	(134.6)	(81.8)	(47.2)
Total goodwill net, ending balance	241.4	290.4	326.4
Specialty Alloys Operations
Changes in the carrying amount of goodwill by reportable segment
Total goodwill net, beginning balance	195.5	195.5
Total goodwill net, ending balance	195.5	195.5	195.5
Performance Engineered Products
Changes in the carrying amount of goodwill by reportable segment
Total goodwill net, beginning balance	94.9	130.9
Impairment	(52.8)	(34.6)
Other	3.8	(1.4)
Total goodwill net, ending balance	$ 45.9	$ 94.9	$ 130.9