Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Apr. 02, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 1,042.9	$ 1,038.1
Percent of revenue	100.00%	100.00%
Nickel-based Alloys and Specialty Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	45.00%	53.00%
Precision and Engineered Strip [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	8.00%	10.00%
Precision Forgings, Casting and Components [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	19.00%	16.00%
Titanium and Titanium-based Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	18.00%	14.00%
Zirconium and Related Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	10.00%	7.00%
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue	$ 571.6	$ 588.3
Asia [Member]
Disaggregation of Revenue [Line Items]
Revenue	116.2	153.5
Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue	262.2	238.6
CANADA
Disaggregation of Revenue [Line Items]
Revenue	27.6	23.2
South America, Middle East, and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	65.3	34.5
Aerospace and Defense Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	615.7	575.7
Jet Engines- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	311.2	310.9
Airframes- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	190.1	169.9
Defense [Member]
Disaggregation of Revenue [Line Items]
Revenue	114.4	94.9
Energy
Disaggregation of Revenue [Line Items]
Revenue	158.6	210.2
Oil & Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue	102.5	127.5
Specialty Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue	56.1	82.7
Automotive Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	56.0	59.4
Electronic Devices Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	52.9	34.4
Construction Mining Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	27.2	40.4
Food Equipment and Appliances Market
Disaggregation of Revenue [Line Items]
Revenue	11.9	21.5
Medical Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	59.1	35.0
Other Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	61.5	61.5
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,132.6	1,155.4
Operating Segments | High Performance Materials & Components
Disaggregation of Revenue [Line Items]
Revenue	$ 571.9	$ 529.6
Percent of revenue	100.00%	100.00%
Operating Segments | High Performance Materials & Components | Nickel-based Alloys and Specialty Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	39.00%	45.00%
Operating Segments | High Performance Materials & Components | Precision and Engineered Strip [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	1.00%	1.00%
Operating Segments | High Performance Materials & Components | Precision Forgings, Casting and Components [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	36.00%	34.00%
Operating Segments | High Performance Materials & Components | Titanium and Titanium-based Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	24.00%	20.00%
Operating Segments | High Performance Materials & Components | Zirconium and Related Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	0.00%	0.00%
Operating Segments | High Performance Materials & Components | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue	$ 240.7	$ 196.5
Operating Segments | High Performance Materials & Components | Asia [Member]
Disaggregation of Revenue [Line Items]
Revenue	38.9	44.0
Operating Segments | High Performance Materials & Components | Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue	211.5	194.2
Operating Segments | High Performance Materials & Components | CANADA
Disaggregation of Revenue [Line Items]
Revenue	15.3	12.0
Operating Segments | High Performance Materials & Components | South America, Middle East, and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	23.5	24.4
Operating Segments | High Performance Materials & Components | Aerospace and Defense Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	442.6	395.4
Operating Segments | High Performance Materials & Components | Jet Engines- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	296.9	282.5
Operating Segments | High Performance Materials & Components | Airframes- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	85.7	71.0
Operating Segments | High Performance Materials & Components | Defense [Member]
Disaggregation of Revenue [Line Items]
Revenue	60.0	41.9
Operating Segments | High Performance Materials & Components | Energy
Disaggregation of Revenue [Line Items]
Revenue	21.7	27.3
Operating Segments | High Performance Materials & Components | Oil & Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue	3.5	2.4
Operating Segments | High Performance Materials & Components | Specialty Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue	18.2	24.9
Operating Segments | High Performance Materials & Components | Automotive Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	5.0	6.3
Operating Segments | High Performance Materials & Components | Electronic Devices Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	1.0	0.5
Operating Segments | High Performance Materials & Components | Construction Mining Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	6.7	8.2
Operating Segments | High Performance Materials & Components | Food Equipment and Appliances Market
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0
Operating Segments | High Performance Materials & Components | Medical Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	35.9	17.5
Operating Segments | High Performance Materials & Components | Other Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	17.0	15.9
Operating Segments | Advanced Alloys & Solutions
Disaggregation of Revenue [Line Items]
Revenue	$ 560.7	$ 625.8
Percent of revenue	100.00%	100.00%
Operating Segments | Advanced Alloys & Solutions | Nickel-based Alloys and Specialty Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	51.00%	60.00%
Operating Segments | Advanced Alloys & Solutions | Precision and Engineered Strip [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	17.00%	19.00%
Operating Segments | Advanced Alloys & Solutions | Precision Forgings, Casting and Components [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	0.00%	0.00%
Operating Segments | Advanced Alloys & Solutions | Titanium and Titanium-based Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	12.00%	8.00%
Operating Segments | Advanced Alloys & Solutions | Zirconium and Related Alloys [Member]
Disaggregation of Revenue [Line Items]
Percent of revenue	20.00%	13.00%
Operating Segments | Advanced Alloys & Solutions | UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue	$ 330.9	$ 391.8
Operating Segments | Advanced Alloys & Solutions | Asia [Member]
Disaggregation of Revenue [Line Items]
Revenue	77.3	109.5
Operating Segments | Advanced Alloys & Solutions | Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue	50.7	44.4
Operating Segments | Advanced Alloys & Solutions | CANADA
Disaggregation of Revenue [Line Items]
Revenue	12.3	11.2
Operating Segments | Advanced Alloys & Solutions | South America, Middle East, and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	41.8	10.1
Operating Segments | Advanced Alloys & Solutions | Aerospace and Defense Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	173.1	180.3
Operating Segments | Advanced Alloys & Solutions | Jet Engines- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	14.3	28.4
Operating Segments | Advanced Alloys & Solutions | Airframes- Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue	104.4	98.9
Operating Segments | Advanced Alloys & Solutions | Defense [Member]
Disaggregation of Revenue [Line Items]
Revenue	54.4	53.0
Operating Segments | Advanced Alloys & Solutions | Energy
Disaggregation of Revenue [Line Items]
Revenue	136.9	182.9
Operating Segments | Advanced Alloys & Solutions | Oil & Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue	99.0	125.1
Operating Segments | Advanced Alloys & Solutions | Specialty Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue	37.9	57.8
Operating Segments | Advanced Alloys & Solutions | Automotive Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	51.0	53.1
Operating Segments | Advanced Alloys & Solutions | Electronic Devices Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	51.9	33.9
Operating Segments | Advanced Alloys & Solutions | Construction Mining Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	20.5	32.2
Operating Segments | Advanced Alloys & Solutions | Food Equipment and Appliances Market
Disaggregation of Revenue [Line Items]
Revenue	11.9	21.5
Operating Segments | Advanced Alloys & Solutions | Medical Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	23.2	17.5
Operating Segments | Advanced Alloys & Solutions | Other Market [Member]
Disaggregation of Revenue [Line Items]
Revenue	44.5	45.6
External Customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,042.9	1,038.1
External Customers | Operating Segments | High Performance Materials & Components
Disaggregation of Revenue [Line Items]
Revenue	529.9	471.1
External Customers | Operating Segments | Advanced Alloys & Solutions
Disaggregation of Revenue [Line Items]
Revenue	$ 513.0	$ 567.0