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Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (Parenthetical) (Detail) (Sales [Member], Aluminum Contracts [Member], USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2014
Sales [Member] | Aluminum Contracts [Member] |
Derivative Instruments, Gain (Loss) [Line Items] |
Amount of gain/loss recognized in earnings related to the ineffective portion of hedging relationships | $ 20

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- Definition Derivative instruments gain loss recognized in income related to ineffective portion. + References No definition available. + Details
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Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
Name: | us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration