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Noncontrolling Interests - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended 1 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Aug. 31, 2014
Noncontrolling Interest [Line Items]      
Charges related to legal matters included in noncontrolling interests $ 391us-gaap_LegalFees $ 85us-gaap_LegalFees  
Noncontrolling Interests [Member]      
Noncontrolling Interest [Line Items]      
Charges related to legal matters included in noncontrolling interests $ 17us-gaap_LegalFees
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember		 $ 34us-gaap_LegalFees
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_NoncontrollingInterestMember		  
Aluminum Brazing Sheet [Member]      
Noncontrolling Interest [Line Items]      
Percentage of acquisition of outstanding noncontrolling interest     30.00%aa_BusinessAcquisitionOfOutstandingNoncontrollingInterestPercentage
/ us-gaap_StatementBusinessSegmentsAxis
= aa_AluminumBrazingSheetMember