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Receivables (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2011 | Mar. 26, 2010 | Oct. 29, 2009
Receivables [Abstract] |  |  |
Maximum cash received for sale of senior undivided interest in customer receivables |  |  | $ 250
Repayment of principal of accounts receivable securitization program |  | 250 |
Pro forma impact of recently adopted accounting principle - terminated accounts receivable securitization program |  | 250 |
Uncollected sold receivables | $ 212 |  |

X
- Definition Maximum cash received for sale of senior undivided interest in customer receivables. + References No definition available. + Details
Name: | aa_MaximumCashReceivedForSaleOfSeniorUndividedInterestInCustomerReceivables
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Describes the effect a recently adopted accounting principle would have had on an entity's financial statements had circumstances not changed + References No definition available. + Details
Name: | aa_ProformaImpactOfRecentlyAdoptedAccountingPrinciple
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of principal repaid by an entity under a financial asset securitization arrangement upon maturity or termination of such program + References No definition available. + Details
Name: | aa_RepaymentOfPrincipalOfFinancialAssetSecuritizationArrangement
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The cash inflow associated with the sale of receivables arising from the financing of goods and services. + References No definition available. + Details
Name: | us-gaap_ProceedsFromSaleOfFinanceReceivables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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