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v3.23.1

Joint Ventures (Details) - USD ($) $ in Millions | 3 Months Ended | 10 Months Ended | 58 Months Ended
--- | --- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2022 | Dec. 31, 2018 | Dec. 31, 2022
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Cash and cash equivalents | $ 196.2 | $ 584.0 |  |  | $ 584.0
Sale of noncontrolling interests | 0.0 |  | $ 0.9 |  |
Income (loss) from equity investments | (0.3) |  | 0.4 |  |
Next Gen Alloys LLC |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Cash and cash equivalents | $ 1.1 |  |  |  |
Sale of noncontrolling interests |  |  | 0.9 |  |
Allegheny & Tsingshan Stainless |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity method investment ownership percentage | 50.00% |  |  |  |
Allegheny & Tsingshan Stainless | Tsingshan Group |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Sale of noncontrolling interests |  | 5.5 |  | $ 12.0 | 17.5
Uniti |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity method investment ownership percentage | 50.00% |  |  |  |
Advanced Alloys & Solutions | Shanghai STAL Precision Stainless Steel Co Ltd |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Cash and cash equivalents | $ 52.9 |  |  |  |
Advanced Alloys & Solutions | Allegheny & Tsingshan Stainless |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Income (loss) from equity investments | (0.5) |  | (0.3) |  |
Due from Affiliates | 2.9 | 3.2 |  |  | 3.2
Advanced Alloys & Solutions | Uniti |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Income (loss) from equity investments | 0.2 |  | $ 0.7 |  |
Prepaid expenses and other current assets | Advanced Alloys & Solutions | Allegheny & Tsingshan Stainless |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Due from Affiliates | 0.5 | 0.4 |  |  | 0.4
Other Noncurrent Assets [Member] | Advanced Alloys & Solutions | Allegheny & Tsingshan Stainless |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Due from Affiliates | $ 2.4 | $ 2.8 |  |  | $ 2.8
China Baowu Steel Group Corporation Limited | Advanced Alloys & Solutions | China Baowu Steel Group Corporation Limited | Shanghai STAL Precision Stainless Steel Co Ltd |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Joint venture ownership percentage by unaffiliated entity | 40.00% |  |  |  |
Tsingshan Group | Tsingshan Group | Allegheny & Tsingshan Stainless |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Joint venture ownership percentage by unaffiliated entity | 50.00% |  |  |  |
VSMPO | VSMPO | Uniti |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Joint venture ownership percentage by unaffiliated entity | 50.00% |  |  |  |
ATI Inc. | Next Gen Alloys LLC |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Joint venture ownership percentage | 51.00% |  |  |  |
ATI Inc. | Advanced Alloys & Solutions | Shanghai STAL Precision Stainless Steel Co Ltd |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Joint venture ownership percentage | 60.00% |  |  |  |

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