Revenue - Summary of Revenue by End-use Markets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Net sales	$ 1,836.3	$ 2,550.3	$ 1,836.3	$ 1,475.6
Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	1,565.6	2,213.6	1,565.6	1,262.2
Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	344.5	433.7	344.5	259.8
Intersegment
Disaggregation of Revenue [Line Items]
Net sales	$ (73.8)	(97.0)	(73.8)	(46.4)
Aerospace and Defense
Disaggregation of Revenue [Line Items]
Net sales		1,290.7	790.2	710.9
Aerospace and Defense | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		1,214.6	739.3	673.8
Aerospace and Defense | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		108.0	76.7	48.5
Aerospace and Defense | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		(31.9)	(25.8)	(11.4)
Medical
Disaggregation of Revenue [Line Items]
Net sales		301.6	212.3	143.5
Medical | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		213.8	155.1	99.4
Medical | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		123.4	79.9	65.0
Medical | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		(35.6)	(22.7)	(20.9)
Transportation
Disaggregation of Revenue [Line Items]
Net sales		185.0	178.3	144.5
Transportation | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		178.5	173.4	139.9
Transportation | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		7.5	5.2	4.9
Transportation | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		(1.0)	(0.3)	(0.3)
Energy
Disaggregation of Revenue [Line Items]
Net sales		163.3	113.0	87.8
Energy | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		151.6	104.8	80.0
Energy | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		11.6	8.1	9.1
Energy | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		0.1	0.1	(1.3)
Industrial and Consumer
Disaggregation of Revenue [Line Items]
Net sales		487.2	417.2	292.1
Industrial and Consumer | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		455.1	393.0	269.1
Industrial and Consumer | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		60.6	49.1	35.5
Industrial and Consumer | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		(28.5)	(24.9)	(12.5)
Distribution
Disaggregation of Revenue [Line Items]
Net sales		122.5	125.3	96.8
Distribution | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales		0.0	0.0	0.0
Distribution | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales		122.6	125.5	96.8
Distribution | Intersegment
Disaggregation of Revenue [Line Items]
Net sales		$ (0.1)	$ (0.2)	$ 0.0