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	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Consolidated net sales	$ 1,836.3	$ 2,550.3	$ 1,836.3	$ 1,475.6
Consolidated operating income (loss)		133.1	(24.9)	(248.6)
Consolidated depreciation and amortization		131.0	131.4	123.6
Consolidated capital expenditures		82.3	91.3	100.5
Consolidated total assets	3,053.9	3,053.9	2,932.3
Corporate costs (including restructuring and asset impairment charges)
Segment Reporting Information [Line Items]
Consolidated operating income (loss)		(75.5)	(52.8)	(144.3)
Consolidated depreciation and amortization		5.3	5.5	5.6
Consolidated capital expenditures		2.0	2.9	25.2
Consolidated total assets	159.0	159.0	248.9
Intersegment
Segment Reporting Information [Line Items]
Consolidated net sales		(97.0)	(73.8)	(46.4)
Consolidated operating income (loss)		(2.3)	0.2	(0.4)
Consolidated depreciation and amortization		0.1	0.0	0.0
Consolidated capital expenditures		0.0	0.1	(0.1)
Consolidated total assets	(17.9)	(17.9)	2.1
Specialty Alloys Operations
Segment Reporting Information [Line Items]
Consolidated net sales	1,565.6	2,213.6	1,565.6	1,262.2
Specialty Alloys Operations | Operating
Segment Reporting Information [Line Items]
Consolidated net sales		2,213.6	1,565.6	1,262.2
Consolidated operating income (loss)		179.1	9.6	(87.4)
Consolidated depreciation and amortization		110.0	110.1	99.7
Consolidated capital expenditures		70.2	77.5	69.4
Consolidated total assets	2,461.2	2,461.2	2,262.4
Performance Engineered Products
Segment Reporting Information [Line Items]
Consolidated net sales	344.5	433.7	344.5	259.8
Performance Engineered Products | Operating
Segment Reporting Information [Line Items]
Consolidated net sales		433.7	344.5	259.8
Consolidated operating income (loss)		31.8	18.1	(16.5)
Consolidated depreciation and amortization		15.6	15.8	18.3
Consolidated capital expenditures		10.1	10.8	$ 6.0
Consolidated total assets	$ 451.6	$ 451.6	$ 418.9