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Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2012
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | $ 2,000,000
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,037
Maturity year of future aluminum price | 2013
Expected future oil prices | 90
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,542
Maturity year of future aluminum price | 2018
Expected future oil prices | 111
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | 537,000,000
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,046
Maturity year of future aluminum price | 2013
Foreign currency exchange rate | 1
Foreign currency exchange rate | 1.03
Foreign currency exchange rate expected year | 2013
Expected Consumer price index, Year | 2013
Expected Consumer price index | 232
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,421
Price of aluminum beyond forward curve | 2,016
Foreign currency exchange rate | 0.93
Expected Consumer price index, Year | 2016
Consumer price index base year | 1982
Consumer price index base | 100
Expected Consumer price index | 254
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | 3,000,000
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected Consumer price index, Year | 2013
Price of electricity beyond forward curve | 78
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Price of electricity beyond forward curve | 170
Maturity date of electricity beyond forward curve | 2036
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Liabilities, Fair Value | 600,000,000
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Maturity year of future aluminum price | 2023
Price of aluminum beyond forward curve | 2,790
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Maturity year of future aluminum price | 2027
Price of aluminum beyond forward curve | 3,002
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Liabilities, Fair Value | $ 30,000,000
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.63%
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.91%
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Median [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.77%

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