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Schedule Of Derivative Contract Assets And Liabilities That Are Measured And Recognized At Fair Value On A Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value asset derivatives $ 94 $ 94
Fair value liability derivatives 681 [1] 737 [1]
Level 1
    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value asset derivatives 60 57
Fair value liability derivatives 72 64
Level 2
    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value asset derivatives 48 47
Fair value liability derivatives 30 44
Level 3
    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value asset derivatives 10 12
Fair value liability derivatives 579 630
Margin Held
    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Margin held (24) (22)
Less margin posted
    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Margin posted   $ (1)
[1] All margin posted is in the form of cash and is valued under a Level 1 technique. The levels that correspond to the margin posted in the table above reference the level of the corresponding liability for which it is posted. Alcoa elected to net the margin posted against the fair value amounts recognized for derivative instruments executed with the same counterparties under master netting arrangements.