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Contingencies and Commitments - Contingencies (Details) € in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 USD ($) location | Dec. 31, 2018 EUR (€) location | Dec. 31, 2017 USD ($) | Dec. 31, 2018 EUR (€)
Loss Contingencies [Line Items] |  |  |  |
Number of cleanup locations (more than) | location | 100 | 100 |  |
Remediation reserve balance | $ 266 |  | $ 294 |
Remediation reserve balance, classified as a current liability | 81 |  | 41 |
Payments related to remediation expenses applied against the reserve | $ 32 |  | 26 |
Tax agreement, indemnification of ultimate liability, percent | 49.00% |  |  | 49.00%
Total combined assessments | $ 174 |  |  | € 152
Income tax reserve | 60 | € 52 |  |
Massena West, NY |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Remediation reserve balance | $ 198 |  | $ 215 |
Actual remediation fieldwork period | 4 years | 4 years |  |
Spain |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Income taxes receivable | $ 29 |  |  | € 25
Recurring Costs of Managing Hazardous Substances and Environmental Programs | Maximum |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Percentage of cost of goods sold | 1.00% | 1.00% |  |
Alcoa Corporation |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Tax agreement, indemnification of ultimate liability, percent | 49.00% |  |  | 49.00%

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