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Segment and Geographic Area Information - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2013 Segment
Segment Reporting Information [Line Items] |
Number of reportable segments | 4
Minimum [Member] |
Segment Reporting Information [Line Items] |
Revenue percentage from aluminum and alumina | 80.00%
Minimum [Member] | Aluminum [Member] |
Segment Reporting Information [Line Items] |
Sales percentage | 90.00%

X
- Definition Revenue percentage from primary operating segment. + References No definition available. + Details
Name: | aa_RevenuePercentageFromPrimaryOperatingSegment
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Sales Percentage + References No definition available. + Details
Name: | aa_SalesPercentage
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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