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Contingencies and Commitments - Commitments (Details) - USD ($) $ in Millions | 1 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020
Loss Contingencies [Line Items] |  |
Purchase obligations due in 2022 | $ 229 |
Purchase obligations due in 2023 | 95 |
Purchase obligations due in 2024 | 80 |
Purchase obligations due in 2025 | 2 |
Purchase obligations due in 2026 | 0 |
Purchase obligations due thereafter | 0 |
Guarantees of third party related to project financing | 15 |
Combined fair value of guarantees | 6 | $ 12
Insurance annual coverage limit | 80 |
Total amount committed under outstanding surety bonds | 47 |
Amount of outstanding surety bonds relating to these liabilities | 25 |
Alcoa Corporation Workers Compensation Claims |  |
Loss Contingencies [Line Items] |  |
Letters of credit, total amount committed | 53 |
Arconic Corporation Environmental Obligations |  |
Loss Contingencies [Line Items] |  |
Letters of credit, total amount committed | 17 |
Arconic Corporation Environmental Obligations | Letters Of Credit Pending Cancellation |  |
Loss Contingencies [Line Items] |  |
Letters of credit, total amount committed | 1 |
Bank Loan Obligations |  |
Loss Contingencies [Line Items] |  |
Letters of credit | 119 |
Separation Agreement | Other Noncurrent Liabilities and Deferred Credits |  |
Loss Contingencies [Line Items] |  |
Guarantees of third party related to project financing | $ 1,406 | $ 1,398

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