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Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) (USD $) | 3 Months Ended
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Mar. 31, 2013
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 | $ 1,000,000
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 | 1,894
Maturity year of future aluminum price | 2013
Expected future oil prices | 91
Maturity year of future oil price | 2018
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 | 2,335
Maturity year of future aluminum price | 2018
Expected future oil prices | 110
Maturity year of future oil price | 2013
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 | 509,000,000
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 | 1,883
Maturity year of future aluminum price | 2013
Foreign currency exchange rate | 1
Foreign currency exchange rate | 1.04
Foreign currency exchange rate expected year | 2013
Expected consumer price index | 233
Expected consumer price index, Year | 2013
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 | 2,172
Maturity year of future aluminum price | 2016
Foreign currency exchange rate | 0.94
Foreign currency exchange rate expected year | 2016
Consumer price index base year | 1982
Expected consumer price index | 253
Consumer price index base | 100
Expected consumer price index, Year | 2016
Interrelationship of LME price to overall energy price [Member] | Aluminum contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair value | 12,000,000
Interrelationship of LME price to overall energy price [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 | 1,928
Maturity year of future aluminum price | 2013
Interrelationship of LME price to overall energy price [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 | 2,359
Maturity year of future aluminum price | 2019
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 | 8,000,000
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] |
Price of electricity beyond forward curve | 78
Maturity date of electricity beyond forward curve | 2023
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 | 478,000,000
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] |
Price of aluminum beyond forward curve | 2,569
Maturity year of future aluminum price | 2023
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] |
Price of aluminum beyond forward curve | 2,766
Maturity year of future aluminum price | 2027
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 | $ 32,000,000
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 | 1.71%
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 | 2.06%
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 | 1.88%

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