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Accounts Receivables (Details) (USD $) In Millions | Sep. 30, 2011
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Accounts Receivables |
Sold receivables that remain uncollected | $ 206

X
- Definition Amount Of Sold Receivables Remain Uncollected + Details
Name: | aa_AmountOfSoldReceivablesRemainUncollected
Namespace Prefix: | aa
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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