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Commitments And Contingencies (Litigation) (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended |  | 1 Months Ended | 9 Months Ended | 3 Months Ended
--- | --- | --- | --- | --- | ---
Sep. 30, 2011 | Feb. 27, 2008 Aluminium Bahrain V. Alcoa [Member] | Nov. 30, 2006 Curtis v. Alcoa [Member] | Sep. 30, 2011 Punitive Damages [Member] | Mar. 31, 2011 Negligence Claim for Property Damages [Member] | Jun. 30, 2011 Prejudgment Interest Breach Of Warranty Award [Member] | Mar. 31, 2011 Prejudgment Interest Breach Of Warranty Award [Member]
Period of alleged conspiracy, years |  | 15 |  |  |  |  |
Retired former employees involved in class action |  |  | 13,000 |  |  |  |
Jury award | $ 13 |  |  | $ 6 | $ 10 |  | $ 2
Charge recorded due to post-trial decisions |  |  |  |  |  | $ 20 |

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- Definition Period Of Alleged Conspiracy, Years + Details
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Balance Type: | na
Period Type: | instant

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- Definition Retired former employees involved in class action + Details
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Namespace Prefix: | aa
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- Definition The net proceeds or assets obtained in excess of (less than) the net carrying amount of assets recorded, or assets distributed and liabilities assumed less than (in excess of) estimated litigation liability extinguished, in settlement of a litigation matter. Represents (for other than an insurance entity in its normal claims settlement process), the amount of income (expense) recognized in the period to settle pending or threatened litigation and insurance claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 5 -Paragraph 9, 10, 11, 12 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349 + Details
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- Definition This element represents the expenses incurred by the entity which are directly related and attributable to receiving an award in settlement of litigation. + Details
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