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Pension and Other Postretirement Benefits - Schedule of Fair Value of Pension Plan Assets (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2013
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Schedule Of Sale Of Subsidiary [Abstract] |
Net receivable which represents securities sold not yet settled plus interest and dividends earned on various investments | $ 159

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- Definition Receivables excluded from pension plan assets. + References No definition available. + Details
Name: | aa_ReceivablesExcludedFromPensionPlanAssets
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
Name: | aa_ScheduleOfSaleOfSubsidiaryAbstract
Namespace Prefix: | aa_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration