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Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Embedded Aluminum Derivative [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Fair value measurement, Assets, Beginning balance | $ 266 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Sales | 6 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Cost of goods sold | (21)aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Other income, net | 1 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherExpenses / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Other comprehensive loss | (43)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Purchases, sales, issuances, and settlements | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Transfers into and/or out of Level 3 | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Foreign currency translation | (8)aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationAdjustments / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Ending balance | 201 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Sales | 0 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInSales / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Cost of goods sold | 0 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Assets, Other income, net | 1 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherExpenses / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Beginning balance | 376 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Sales | (6)aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInSales / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Cost of goods sold | 0 aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Other comprehensive loss | 55 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Purchases, sales, issuances, and settlements | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchasesSalesIssuancesSettlements / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Transfers into and/or out of Level 3 | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Foreign currency translation | 0 aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesForeignCurrencyTranslationAdjustments / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Ending balance | 425 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Sales | 0 aa_FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInSales / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Fair value measurement, Liabilities, Cost of goods sold | 0 aa_FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Embedded Credit Derivative [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Fair value measurement, Liabilities, Beginning balance | 18 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Cost of goods sold | 0 aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Other income, net | (2)aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInOtherIncomeExpensesNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Purchases, sales, issuances, and settlements | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchasesSalesIssuancesSettlements / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Transfers into and/or out of Level 3 | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Foreign currency translation | 0 aa_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesForeignCurrencyTranslationAdjustments / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Ending balance | 16 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Sales | 0 aa_FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInSales / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Cost of goods sold | 0 aa_FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Fair value measurement, Liabilities, Other income, net | (2)aa_FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherExpenses / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Energy Contracts [Member] |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
Fair value measurement, Assets, Beginning balance | 2 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Other comprehensive loss | 6 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Purchases, sales, issuances, and settlements | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Transfers into and/or out of Level 3 | 0 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Ending balance | 8 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Sales | 0 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInSales / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember
Fair value measurement, Assets, Cost of goods sold | $ 0 aa_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInCostOfGoodsSold / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EnergyRelatedDerivativeMember

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- Definition Fair value assets measured on recurring basis gain loss included in other expenses. + References No definition available. + Details
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- Definition Fair value assets measured on recurring basis gain loss included in sales. + References No definition available. + Details
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- Definition Fair value liabilities measured on recurring basis gain loss included in cost of goods sold. + References No definition available. + Details
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- Definition Fair value liabilities measured on recurring basis gain loss included in other expenses. + References No definition available. + Details
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- Definition Fair value liabilities measured on recurring basis gain loss included in sales. + References No definition available. + Details
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- Definition Fair value measurement with unobservable inputs reconciliation recurring basis asset cost of goods sold. + References No definition available. + Details
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- Definition Fair value measurement with unobservable inputs reconciliation recurring basis asset foreign currency translation adjustments. + References No definition available. + Details
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- Definition Fair value measurement with unobservable inputs reconciliation recurring basis liabilities gain loss included in cost of goods sold. + References No definition available. + Details
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- Definition Fair value measurement with unobservable inputs reconciliation recurring basis liabilities gain loss included in other income expenses net. + References No definition available. + Details
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- Definition Fair value measurement with unobservable inputs reconciliation recurring basis liabilities gain loss included in sales. + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph c -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy. + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph c -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy. + References No definition available. + Details
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- Details
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