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Properties, Plants, and Equipment, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 Kmt | Dec. 31, 2012 Kmt
Smelting Assets [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Net carrying value of assets | $ 404 | $ 310
Net carrying value of other idled smelting assets written off | 44 |
Idle capacity of assets, units | 655 | 547
Idled Refining Assets [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Net carrying value of assets | $ 60 | $ 68
Idle capacity of assets, units | 1,216 | 1,277

X
- Definition Idle capacity of asset. + References No definition available. + Details
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Namespace Prefix: | aa_
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Balance Type: | na
Period Type: | duration

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- Definition Net carrying value of assets. + References No definition available. + Details
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Namespace Prefix: | aa_
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Balance Type: | debit
Period Type: | instant

X
- Definition Write off of the net carrying value of other idled smelting assets. + References No definition available. + Details
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Namespace Prefix: | aa_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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