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Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2016 USD ($) MWh Index $ / MWh $ / Metric_Ton $ / lb $ / AUD $ / Barrels | Dec. 31, 2015 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | $ 794 | $ 1,137
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | 718 |
Derivative Liabilities, Fair value | $ | $ 196 |
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 2,093 |
Maturity year of future aluminum price | 2026 |
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 2,137 |
Maturity year of future aluminum price | 2027 |
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 2,093 |
Maturity year of future aluminum price | 2026 |
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Midwest Premium | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Midwest Premium | $ / lb | 0.0775 |
Foreign currency exchange rate expected year | 2021 |
Embedded Aluminum Derivative [Member] | Price of Aluminum beyond Forward Curve [Member] | Midwest Premium | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Midwest Premium | $ / lb | 0.0775 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | $ 23 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,631 |
Maturity year of future aluminum price | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,637 |
Maturity year of future aluminum price | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Estimated Foreign Currency Exchange Rate [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Foreign currency exchange rate | $ / AUD | 0.74 |
Foreign currency exchange rate expected year | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Consumer Price Index [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Consumer price index base year | 1982 |
Consumer price index base | Index | 100 |
Expected consumer price index | Index | 236 |
Expected consumer price index, Year | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of LME Price to Overall Energy Price [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | $ 4 |
Embedded Aluminum Derivative [Member] | Interrelationship of LME Price to Overall Energy Price [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,614 |
Maturity year of future aluminum price | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of LME Price to Overall Energy Price [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,755 |
Maturity year of future aluminum price | 2019 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum and Oil Prices [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,631 |
Maturity year of future aluminum price | 2016 |
Expected future oil prices | $ / Barrels | 49 |
Maturity year of future oil price | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of Future Aluminum and Oil Prices [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,710 |
Maturity year of future aluminum price | 2018 |
Expected future oil prices | $ / Barrels | 55 |
Maturity year of future oil price | 2018 |
Embedded Aluminum Derivative [Member] | Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Liabilities, Fair value | $ | $ 32 |
Megawatt hours per year | MWh | 2,000,000 |
Embedded Aluminum Derivative [Member] | Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,631 |
Maturity year of future aluminum price | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 1,729 |
Maturity year of future aluminum price | 2019 |
Embedded Aluminum Derivative [Member] | Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] | Midwest Premium | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Midwest Premium | $ / lb | 0.0725 |
Foreign currency exchange rate expected year | 2016 |
Embedded Aluminum Derivative [Member] | Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] | Midwest Premium | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Midwest Premium | $ / lb | 0.0775 |
Foreign currency exchange rate expected year | 2019 |
Embedded Aluminum Derivative [Member] | Two Contracts [Member] | Price of Aluminum beyond Forward Curve [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 2,245 |
Maturity year of future aluminum price | 2029 |
Embedded Aluminum Derivative [Member] | Two Contracts [Member] | Price of Aluminum beyond Forward Curve [Member] | Midwest Premium | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Foreign currency exchange rate expected year | 2029 |
Embedded Aluminum Derivative [Member] | One Contract [Member] | Price of Aluminum beyond Forward Curve [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected future aluminum prices | 2,540 |
Maturity year of future aluminum price | 2036 |
Embedded Aluminum Derivative [Member] | One Contract [Member] | Price of Aluminum beyond Forward Curve [Member] | Midwest Premium | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Foreign currency exchange rate expected year | 2036 |
Energy Contracts [Member] | Price of Electricity beyond Forward Curve [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | $ 40 |
Energy Contracts [Member] | Price of Electricity beyond Forward Curve [Member] | Average Price [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Price of electricity beyond forward curve | $ / MWh | 48 |
Maturity date of electricity beyond forward curve | 2019 |
Energy Contracts [Member] | Price of Electricity beyond Forward Curve [Member] | Average Price [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Price of electricity beyond forward curve | $ / MWh | 116 |
Maturity date of electricity beyond forward curve | 2036 |
Embedded Credit Derivative [Member] | Credit Spread between Alcoa and Counterparty [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Liabilities, Fair value | $ | $ 33 |
Embedded Credit Derivative [Member] | Credit Spread between Alcoa and Counterparty [Member] | Credit Spread [Member] | Level 3 [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Percentage of credit spread | 3.63% |
Embedded Credit Derivative [Member] | Credit Spread between Alcoa and Counterparty [Member] | Credit Spread [Member] | Level 3 [Member] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Percentage of credit spread | 3.45% |
Embedded Credit Derivative [Member] | Credit Spread between Alcoa and Counterparty [Member] | Credit Spread [Member] | Level 3 [Member] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Percentage of credit spread | 3.81% |

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