XML 1069 R151.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | $ 2,000,000
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,037
Maturity year of future aluminum price | 2013
Expected future oil prices | 90
Interrelationship of Future Aluminum and Oil Prices [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,542
Maturity year of future aluminum price | 2018
Expected future oil prices | 111
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | 537,000,000
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,046
Maturity year of future aluminum price | 2013
Foreign currency exchange rate | 1
Foreign currency exchange rate | 1.03
Foreign currency exchange rate expected year | 2013
Expected Consumer price index, Year | 2013
Expected Consumer price index | 232
Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected future aluminum prices | 2,421
Price of aluminum beyond forward curve | 2,016
Foreign currency exchange rate | 0.93
Expected Consumer price index, Year | 2016
Consumer price index base year | 1982
Consumer price index base | 100
Expected Consumer price index | 254
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Assets, Fair Value | 3,000,000
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Expected Consumer price index, Year | 2013
Price of electricity beyond forward curve | 78
Price of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Price of electricity beyond forward curve | 170
Maturity date of electricity beyond forward curve | 2036
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Liabilities, Fair Value | 600,000,000
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Maturity year of future aluminum price | 2023
Price of aluminum beyond forward curve | 2,790
Price of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Maturity year of future aluminum price | 2027
Price of aluminum beyond forward curve | 3,002
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Derivative Liabilities, Fair Value | $ 30,000,000
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Minimum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.63%
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Maximum [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.91%
Credit Spread Between Alcoa and Counterparty [Member] | Embedded Credit Derivative [Member] | Median [Member] | Discounted Cash Flow [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Percentage of credit spread | 1.77%

X
- Definition Average percentage of credit spread. + References No definition available. + Details
Name: | aa_AveragePercentageOfCreditSpread
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Base Year Consumer Price Index + References No definition available. + Details
Name: | aa_BaseYearConsumerPriceIndex
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Consumer Price Index Base Year + References No definition available. + Details
Name: | aa_ConsumerPriceIndexBaseYear
Namespace Prefix: | aa_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected Consumer Price Index + References No definition available. + Details
Name: | aa_ExpectedConsumerPriceIndex
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected Date Of Consumer Price Index + References No definition available. + Details
Name: | aa_ExpectedDateOfConsumerPriceIndex
Namespace Prefix: | aa_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected future aluminum prices. + References No definition available. + Details
Name: | aa_ExpectedFutureAluminumPrices
Namespace Prefix: | aa_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected future oil prices. + References No definition available. + Details
Name: | aa_ExpectedFutureOilPrices
Namespace Prefix: | aa_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected price of aluminum through forward curve + References No definition available. + Details
Name: | aa_ExpectedPriceOfAluminumThroughForwardCurve
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Foreign Currency Derivatives Maturity Date + References No definition available. + Details
Name: | aa_ForeignCurrencyDerivativesMaturityDate
Namespace Prefix: | aa_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maturity Data Of Future Aluminum Price + References No definition available. + Details
Name: | aa_MaturityDataOfFutureAluminumPrice
Namespace Prefix: | aa_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maturity date of electricity beyond forward curve. + References No definition available. + Details
Name: | aa_MaturityDateOfElectricityBeyondForwardCurve
Namespace Prefix: | aa_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Price of electricity through forward curve. + References No definition available. + Details
Name: | aa_PriceOfElectricityThroughForwardCurve
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value of the gross assets less the gross liabilities of a derivative asset or group of derivative assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13495-108611 + Details
Name: | us-gaap_DerivativeAssetFairValueNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of the gross liabilities less the gross assets of a derivative liability or group of derivative liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13495-108611 + Details
Name: | us-gaap_DerivativeLiabilityFairValueNet1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Foreign exchange rate used to remeasure amounts denominated in a currency other than functional currency into functional currency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521 + Details
Name: | us-gaap_ForeignCurrencyExchangeRateRemeasurement1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521 + Details
Name: | us-gaap_ForeignCurrencyExchangeRateTranslation1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant