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Properties, Plants, and Equipment, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 Kmt | Dec. 31, 2011 Mg Kmt
Smelting Assets [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Net carrying value of assets | $ 325 | $ 166
Net carrying value of other idled smelting assets written off |  | 291
Idle capacity of assets, units | 591 | 353
Idled Refining Assets [Member] |  |
Property, Plant and Equipment [Line Items] |  |
Net carrying value of assets | $ 68 | $ 65
Idle capacity of assets, units | 1,277 | 1,177

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- Definition Idle Capacity Of Asset + References No definition available. + Details
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- Definition Net Carrying Value Of Assets + References No definition available. + Details
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- 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_
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- Details
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