Goodwill and Other Intangible Assets, Net - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Changes in the carrying amount of goodwill by reportable segment
Goodwill, Beginning Balance		$ 292.1	$ 292.4
Other		(0.1)	(0.3)
Impairment		0.0
Goodwill, Ending Balance		292.0	292.1	$ 292.4
Accumulated impairment losses, Beginning Balance		(34.7)	(34.7)
Accumulated impairment losses, Other		0.0	0.0
Accumulated impairment losses, Impairment		(12.5)
Accumulated impairment losses, Ending Balance		(47.2)	(34.7)	(34.7)
Goodwill, Beginning Balance		257.4	257.7
Other		(0.1)	(0.3)
Goodwill impairment	$ (12.5)	(12.5)	0.0	0.0
Goodwill, Ending Balance		244.8	257.4	257.7
Specialty Alloys Operations
Changes in the carrying amount of goodwill by reportable segment
Goodwill, Beginning Balance		195.5	195.5
Other		0.0	0.0
Goodwill impairment		0.0
Goodwill, Ending Balance		195.5	195.5	195.5
Performance Engineered Products
Changes in the carrying amount of goodwill by reportable segment
Goodwill, Beginning Balance		61.9	62.2
Other		(0.1)	(0.3)
Goodwill impairment		(12.5)
Goodwill, Ending Balance		$ 49.3	$ 61.9	$ 62.2