Segment Information, Geographic and Product Data - Schedule of Results of Operation, Depreciation and Amortization, Capital Expenditures and Total Assets by Reportable Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Consolidated net sales	$ 1,475.6	$ 2,181.1	$ 2,380.2
Consolidated operating (loss) income	(248.6)	25.3	241.4
Consolidated depreciation and amortization	123.6	123.9	121.5
Consolidated capital expenditures	100.5	171.4	180.3
Consolidated total assets	2,971.2	3,227.2
Corporate costs (including restructuring and asset impairment charges)
Segment Reporting Information [Line Items]
Consolidated operating (loss) income	(144.3)	(205.0)	(72.7)
Consolidated depreciation and amortization	5.6	6.2	4.9
Consolidated capital expenditures	25.2	54.9	37.1
Consolidated total assets	402.2	428.9
Intersegment
Segment Reporting Information [Line Items]
Consolidated net sales	(46.4)	(51.6)	(66.9)
Consolidated operating (loss) income	(0.4)	1.7	1.9
Consolidated depreciation and amortization	0.0	(0.6)	(0.8)
Consolidated capital expenditures	(0.1)	0.0	(1.2)
Consolidated total assets	0.4	(9.2)
Specialty Alloys Operations | Operating
Segment Reporting Information [Line Items]
Consolidated net sales	1,262.2	1,831.6	1,967.3
Consolidated operating (loss) income	(87.4)	239.0	282.2
Consolidated depreciation and amortization	99.7	93.5	95.2
Consolidated capital expenditures	69.4	99.3	92.7
Consolidated total assets	2,150.1	2,259.0
Performance Engineered Products | Operating
Segment Reporting Information [Line Items]
Consolidated net sales	259.8	401.1	479.8
Consolidated operating (loss) income	(16.5)	(10.4)	30.0
Consolidated depreciation and amortization	18.3	24.8	22.2
Consolidated capital expenditures	6.0	17.2	$ 51.7
Consolidated total assets	$ 418.5	$ 548.5