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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, 2015 USD ($) Index $ / Metric_Ton $ / MWh $ / Barrels $ / AUD $ / lb | Dec. 31, 2014 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Derivative Assets, Fair value | $ | $ 680 | $ 268
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 | $ | $ 119 |
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 | 1,668 |
Maturity year of future aluminum price | 2015 |
Expected future aluminum prices | 1,668 |
Maturity year of future aluminum price | 2015 |
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 | 1,761 |
Maturity year of future aluminum price | 2016 |
Expected future aluminum prices | 1,761 |
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] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Foreign currency exchange rate | $ / AUD | 0.77 |
Foreign currency exchange rate expected year | 2015 |
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] | Maximum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Foreign currency exchange rate | $ / AUD | 0.77 |
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] | Minimum [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Expected consumer price index | Index | 234 |
Expected consumer price index, Year | 2015 |
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] | Maximum [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 | 241 |
Expected consumer price index, Year | 2016 |
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 | 1,668 |
Maturity year of future aluminum price | 2015 |
Expected future oil prices | $ / Barrels | 62 |
Maturity year of future oil price | 2015 |
Expected future aluminum prices | 1,668 |
Maturity year of future aluminum price | 2015 |
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 | 1,910 |
Maturity year of future aluminum price | 2018 |
Expected future oil prices | $ / Barrels | 72 |
Maturity year of future oil price | 2018 |
Expected future aluminum prices | 1,910 |
Maturity year of future aluminum price | 2018 |
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 | $ | $ 557 |
Derivative Liabilities, Fair value | $ | $ 294 |
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 | 2,660 |
Maturity year of future aluminum price | 2025 |
Expected future aluminum prices | 2,660 |
Maturity year of future aluminum price | 2025 |
Embedded Aluminum Derivative [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 | 2,353 |
Maturity year of future aluminum price | 2027 |
Expected future aluminum prices | 2,353 |
Maturity year of future aluminum price | 2027 |
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 | 0.0920 |
Foreign currency exchange rate expected year | 2020 |
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 | 0.0920 |
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 | 1,802 |
Maturity year of future aluminum price | 2015 |
Expected future aluminum prices | 1,802 |
Maturity year of future aluminum price | 2015 |
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 | 1,935 |
Maturity year of future aluminum price | 2019 |
Expected future aluminum prices | 1,935 |
Maturity year of future aluminum price | 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 | 2,460 |
Maturity year of future aluminum price | 2029 |
Expected future aluminum prices | 2,460 |
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 | 2,756 |
Maturity year of future aluminum price | 2036 |
Expected future aluminum prices | 2,756 |
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 |
Embedded Credit 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 Liabilities, Fair value | $ | $ 19 |
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 | 1.80% |
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 | 1.65% |
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 | 1.95% |
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 Liabilities, Fair value | $ | $ 9 |
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 | 43 |
Maturity date of electricity beyond forward curve | 2018 |
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 | 130 |
Maturity date of electricity beyond forward curve | 2036 |

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