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Contingencies and Commitments - Commitments (Details) - USD ($) $ in Millions | 1 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Loss Contingencies [Line Items] |  |  |
Purchase obligations due in 2024 | $ 244 |  |
Purchase obligations due in 2025 | 32 |  |
Purchase obligations due in 2026 | 11 |  |
Purchase obligations due in 2027 | 0 |  |
Purchase obligations due in 2028 | 0 |  |
Purchase obligations due thereafter | 0 |  |
Guarantees of third party related to project financing | 24 |  |
Combined fair value of guarantees | 6 | $ 6 |
Insurance annual coverage limit | 80 | 80 | $ 80
Total amount committed under outstanding surety bonds | 43 |  |
Amount of outstanding surety bonds relating to these liabilities | 21 |  |
Alcoa Corporation Workers Compensation Claims |  |  |
Loss Contingencies [Line Items] |  |  |
Letters of credit, total amount committed | 52 |  |
Arconic Corporation Environmental Obligations |  |  |
Loss Contingencies [Line Items] |  |  |
Letters of credit, total amount committed | 17 |  |
Letter of Credit |  |  |
Loss Contingencies [Line Items] |  |  |
Maximum borrowing capacity | 114 |  |
Other Noncurrent Liabilities and Deferred Credits | Separation Agreement |  |  |
Loss Contingencies [Line Items] |  |  |
Guarantees of third party related to project financing | $ 1,131 | $ 1,040 |

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