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Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 29, 2025 | Jun. 30, 2024 | Jun. 29, 2025 | Jun. 30, 2024
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 1,140.4 | $ 1,095.3 | $ 2,284.8 | $ 2,138.2
Percent of revenue | 100.00% | 100.00% | 100.00% | 100.00%
Nickel-based Alloys and Specialty Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 48.00% | 44.00% | 48.00% | 44.00%
Precision and Engineered Strip [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 5.00% | 9.00% | 5.00% | 9.00%
Precision Forgings, Casting and Components [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 21.00% | 19.00% | 21.00% | 19.00%
Titanium and Titanium-based Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 17.00% | 20.00% | 18.00% | 19.00%
Zirconium and Related Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 9.00% | 8.00% | 8.00% | 9.00%
UNITED STATES |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 650.4 | $ 638.5 | $ 1,294.2 | $ 1,210.1
Asia [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 149.2 | 125.5 | 263.5 | 241.7
Europe [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 235.8 | 278.2 | 496.5 | 540.4
CANADA |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 39.9 | 25.9 | 79.7 | 53.5
South America, Middle East, and Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 65.1 | 27.2 | 150.9 | 92.5
Aerospace and Defense Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 761.8 | 683.9 | 1,516.2 | 1,299.6
Jet Engines- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 447.8 | 352.8 | 869.2 | 664.0
Airframes- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 195.2 | 210.8 | 401.0 | 400.9
Defense [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 118.8 | 120.3 | 246.0 | 234.7
Conventional energy |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 92.9 | 66.1 | 214.7 | 168.6
Specialty Energy [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 63.5 | 76.6 | 114.0 | 132.7
Automotive Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 64.8 | 70.8 | 125.4 | 126.8
Electronic Devices Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 43.7 | 40.8 | 83.3 | 93.7
Construction Mining Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 33.3 | 44.2 | 66.2 | 71.4
Medical Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 38.9 | 61.7 | 81.3 | 120.8
Other Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 41.5 | 51.2 | 83.7 | 124.6
Other Core Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 146.1 | 179.1 | 278.6 | 347.2
Core End Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 907.9 | 863.0 | 1,794.8 | 1,646.8
Industrial Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 232.5 | 232.3 | 490.0 | 491.4
Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 1,240.6 | 1,248.4 | 2,502.3 | 2,381.0
Operating Segments | HPMC |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 662.1 | $ 643.8 | $ 1,306.1 | $ 1,215.7
Percent of revenue | 100.00% | 100.00% | 100.00% | 100.00%
Operating Segments | HPMC | Nickel-based Alloys and Specialty Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 44.00% | 39.00% | 43.00% | 39.00%
Operating Segments | HPMC | Precision and Engineered Strip [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 0.00% | 0.00% | 0.00% | 1.00%
Operating Segments | HPMC | Precision Forgings, Casting and Components [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 39.00% | 37.00% | 39.00% | 36.00%
Operating Segments | HPMC | Titanium and Titanium-based Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 17.00% | 24.00% | 18.00% | 24.00%
Operating Segments | HPMC | Zirconium and Related Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 0.00% | 0.00% | 0.00% | 0.00%
Operating Segments | HPMC | UNITED STATES |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 350.3 | $ 271.4 | $ 666.7 | $ 512.1
Operating Segments | HPMC | Asia [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 43.8 | 37.3 | 77.1 | 76.2
Operating Segments | HPMC | Europe [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 168.7 | 224.0 | 360.0 | 435.5
Operating Segments | HPMC | CANADA |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 17.0 | 13.7 | 37.1 | 29.0
Operating Segments | HPMC | South America, Middle East, and Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 29.0 | 15.6 | 52.0 | 39.1
Operating Segments | HPMC | Aerospace and Defense Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 558.7 | 477.5 | 1,096.2 | 920.1
Operating Segments | HPMC | Jet Engines- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 419.6 | 331.8 | 816.9 | 628.7
Operating Segments | HPMC | Airframes- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 77.3 | 93.7 | 159.1 | 179.4
Operating Segments | HPMC | Defense [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 61.8 | 52.0 | 120.2 | 112.0
Operating Segments | HPMC | Conventional energy |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 1.4 | 2.4 | 3.1 | 5.9
Operating Segments | HPMC | Specialty Energy [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 14.7 | 22.5 | 27.1 | 40.7
Operating Segments | HPMC | Automotive Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 2.8 | 3.8 | 4.2 | 8.8
Operating Segments | HPMC | Electronic Devices Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 0.0 | 2.0 | 0.0 | 3.0
Operating Segments | HPMC | Construction Mining Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 8.1 | 8.3 | 15.2 | 15.0
Operating Segments | HPMC | Medical Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 15.4 | 33.0 | 31.2 | 68.9
Operating Segments | HPMC | Other Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 7.7 | 12.5 | 15.9 | 29.5
Operating Segments | HPMC | Other Core Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 30.1 | 57.5 | 58.3 | 112.6
Operating Segments | HPMC | Core End Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 588.8 | 535.0 | 1,154.5 | 1,032.7
Operating Segments | AA&S |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 578.5 | $ 604.6 | $ 1,196.2 | $ 1,165.3
Percent of revenue | 100.00% | 100.00% | 100.00% | 100.00%
Operating Segments | AA&S | Nickel-based Alloys and Specialty Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 53.00% | 49.00% | 54.00% | 50.00%
Operating Segments | AA&S | Precision and Engineered Strip [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 11.00% | 18.00% | 11.00% | 18.00%
Operating Segments | AA&S | Precision Forgings, Casting and Components [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 0.00% | 0.00% | 0.00% | 0.00%
Operating Segments | AA&S | Titanium and Titanium-based Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 17.00% | 15.00% | 17.00% | 13.00%
Operating Segments | AA&S | Zirconium and Related Alloys [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Percent of revenue | 19.00% | 18.00% | 18.00% | 19.00%
Operating Segments | AA&S | UNITED STATES |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 300.1 | $ 367.1 | $ 627.5 | $ 698.0
Operating Segments | AA&S | Asia [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 105.4 | 88.2 | 186.4 | 165.5
Operating Segments | AA&S | Europe [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 67.1 | 54.2 | 136.5 | 104.9
Operating Segments | AA&S | CANADA |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 22.9 | 12.2 | 42.6 | 24.5
Operating Segments | AA&S | South America, Middle East, and Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 36.1 | 11.6 | 98.9 | 53.4
Operating Segments | AA&S | Aerospace and Defense Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 203.1 | 206.4 | 420.0 | 379.5
Operating Segments | AA&S | Jet Engines- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 28.2 | 21.0 | 52.3 | 35.3
Operating Segments | AA&S | Airframes- Commercial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 117.9 | 117.1 | 241.9 | 221.5
Operating Segments | AA&S | Defense [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 57.0 | 68.3 | 125.8 | 122.7
Operating Segments | AA&S | Conventional energy |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 91.5 | 63.7 | 211.6 | 162.7
Operating Segments | AA&S | Specialty Energy [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 48.8 | 54.1 | 86.9 | 92.0
Operating Segments | AA&S | Automotive Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 62.0 | 67.0 | 121.2 | 118.0
Operating Segments | AA&S | Electronic Devices Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 43.7 | 38.8 | 83.3 | 90.7
Operating Segments | AA&S | Construction Mining Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 25.2 | 35.9 | 51.0 | 56.4
Operating Segments | AA&S | Medical Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 23.5 | 28.7 | 50.1 | 51.9
Operating Segments | AA&S | Other Market [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 33.8 | 38.7 | 67.8 | 95.1
Operating Segments | AA&S | Other Core Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 116.0 | 121.6 | 220.3 | 234.6
Operating Segments | AA&S | Core End Markets |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 319.1 | 328.0 | 640.3 | 614.1
Sales to external customers | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 1,140.4 | 1,095.3 | 2,284.8 | 2,138.2
Sales to external customers | Operating Segments | HPMC |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 608.8 | 562.0 | 1,192.9 | 1,091.9
Sales to external customers | Operating Segments | AA&S |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 531.6 | 533.3 | 1,091.9 | 1,046.3
Industrial Markets | Operating Segments | HPMC |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 20.0 | 27.0 | 38.4 | 59.2
Industrial Markets | Operating Segments | AA&S |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 212.5 | $ 205.3 | $ 451.6 | $ 432.2

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