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Contingencies and Commitments - Environmental Matters (Details) € in Millions, $ in Millions |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 06, 2019 plaintiff | Dec. 31, 2020 USD ($) segment | Dec. 31, 2019 USD ($) | Dec. 31, 2020 EUR (€) | Dec. 31, 2020 USD ($) | Dec. 31, 2018
Loss Contingencies [Line Items] |  |  |  |  |  |
Number of cleanup locations (more than) | segment |  | 30 |  |  |  |
Remediation reserve balance |  |  | $ 8 |  | $ 10 |
Remediation reserve balance, classified as a current liability |  |  | 3 |  | 5 |
Payments related to remediation expenses applied against the reserve |  | $ 2 | $ 3 |  |  |
Total combined assessments |  |  |  | € 54 | $ 64 |
Number of plaintiffs | plaintiff | 247 |  |  |  |  |
Monetary damages sought | 75,000 |  |  |  |  |
Spain |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Income taxes receivable | € |  |  |  | € 53 |  |
Tax agreement, indemnification of ultimate liability, percent |  |  |  | 33.66% | 33.66% | 49.00%
Recurring Costs of Managing Hazardous Substances and Environmental Programs | Maximum |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Percentage of cost of goods sold |  | 1.00% |  |  |  |
Alcoa Corporation |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Tax agreement, indemnification of ultimate liability, percent |  |  |  | 49.00% | 49.00% |
Arconic Corporation |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Tax agreement, indemnification of ultimate liability, percent |  |  |  | 33.66% | 33.66% |
Euro | Spain |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Income taxes receivable | € |  |  |  | € 45 |  |

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