XML 1069 R151.htm IDEA: XBRL DOCUMENT v2.4.0.6
Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) (USD $)
 12 Months Ended
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%