XML 1175 R95.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Other Income, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2011 Australia [Member] | Dec. 31, 2012 Tapoco Hydroelectric Project [Member]
Component of Other Income, Nonoperating [Abstract] |  |  |
Net gain from asset sales |  |  | $ 320
Discrete income tax benefit recognized | 24 |  |
Net gain on sale of land |  | $ 43 |

X
- Definition Discrete income tax benefit recognized. + References No definition available. + Details
Name: | aa_DiscreteIncomeTaxBenefitRecognized
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain (loss) on sale of land. + References No definition available. + Details
Name: | aa_GainLossOnSaleOfLand
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnSaleOfInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration