AA


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents



us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization
us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:CostOfRevenue
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:DebtInstrument
us-gaap:GainsLossesOnExtinguishmentOfDebt
us-gaap:StatementScenario, us-gaap:DebtInstrument

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeTaxExpenseBenefit

us-gaap:InterestExpense
us-gaap:ConsolidationItems

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NonoperatingIncomeExpense

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:ProfitLoss
us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:StatementEquityComponents

us-gaap:ResearchAndDevelopmentExpense

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ProductOrService
us-gaap:ConsolidationItems
us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:Revenues
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:Assets
us-gaap:ConsolidationItems

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity

us-gaap:AssetsCurrent
us-gaap:ProductOrService
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:CashAndCashEquivalentsAtCarryingValue
us-gaap:ConsolidationItems

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryNet

us-gaap:PrepaidExpenseAndOtherAssetsCurrent
us-gaap:ProductOrService
us-gaap:AssetsNoncurrent
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:PropertyPlantAndEquipmentByType
us-gaap:ConsolidationItems, us-gaap:PropertyPlantAndEquipmentByType
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:ConstructionInProgressGross

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:PropertyPlantAndEquipmentNet
us-gaap:ConsolidationItems
us-gaap:StatementGeographical

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:Goodwill
dei:LegalEntity, us-gaap:StatementBusinessSegments
us-gaap:BalanceSheetLocation
us-gaap:BalanceSheetLocation, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:DeferredTaxAssetsLiabilitiesNet
dei:LegalEntity, us-gaap:IncomeTaxAuthority
us-gaap:ConsolidationItems
us-gaap:IncomeTaxAuthority

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OtherAssetsNoncurrent
us-gaap:ConsolidationItems
us-gaap:OtherAssets

us-gaap:AccountsPayableCurrent

us-gaap:LiabilitiesCurrent
us-gaap:ProductOrService
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:LongTermDebtCurrent

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OtherLiabilitiesCurrent

us-gaap:TaxesPayableCurrent
us-gaap:ProductOrService
us-gaap:LiabilitiesNoncurrent
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:LongTermDebt

us-gaap:LongTermDebtNoncurrent

us-gaap:LongTermDebtAndCapitalLeaseObligations
us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

us-gaap:MinorityInterest

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:OperatingLeaseLiability

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:StockholdersEquity

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:MinorityInterest

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DepreciationDepletionAndAmortization

us-gaap:IncreaseDecreaseInInventories

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss

us-gaap:ProfitLoss
us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:StatementEquityComponents

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquireInvestments

us-gaap:NetCashProvidedByUsedInFinancingActivities
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:ProceedsFromIssuanceOfLongTermDebt
us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:DebtInstrumentInterestRateStatedPercentage
us-gaap:OptionIndexedToIssuersEquityType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:DeferredTaxAssetsNet
us-gaap:ValuationAllowancesAndReservesType

us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance
us-gaap:IncomeTaxAuthority
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:ValuationAllowancesAndReservesType

aa:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLossAndOther
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
aa:AccruedOtherPostretirementBenefitAdditionToRemeasurement

aa:AdditionsToLongTermDebtIssuedLessIssuanceDiscount

aa:AdjustedEbitda
us-gaap:StatementBusinessSegments

aa:CostsAndOperatingExpensesAndNonoperatingIncomeExpenses
us-gaap:RealEstateProperties
aa:CurtailmentOfSmeltingCapacity

aa:DefinedBenefitPensionPlansNetPeriodicBenefitCost
us-gaap:RetirementPlanName
aa:DefinedBenefitPlanEmployersContributionPercentageOnAnnualBasis
us-gaap:RetirementPlanName
aa:DefinedBenefitPlanNumberOfEmployeesReduced

aa:DiscreteTaxBenefitExpense

aa:EstimatedAnnualizedEffectiveTaxRate
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
aa:FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet
us-gaap:DerivativeInstrumentRisk
aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIncreaseDecreaseOther
us-gaap:DerivativeInstrumentRisk
aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold
us-gaap:DerivativeInstrumentRisk
aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther
us-gaap:RealEstateProperties, us-gaap:SubsequentEventType
aa:FullCurtailmentOfSmeltingCapacity
us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:GainLossOnDispositionOfAssetsAfterTax
us-gaap:ProductOrService
aa:IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:IncomeLossFromEquityMethodInvestmentsNonoperating
us-gaap:ProductOrService
aa:IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:IncomeTaxAuthorityName
aa:IncomeTaxExaminationReversalOfProvisionForIncomeTaxesReserve

aa:IncomeTaxExpenseBenefitFromEstimatedAnnualizedEffectiveTaxRate
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType
aa:IncreaseInIncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority

aa:MinimumRequiredCashContributionToPensionPlan
us-gaap:RetirementPlanSponsorLocation

aa:MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders
us-gaap:StatementEquityComponents
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:PaymentAmountRefundPercentage
us-gaap:RealEstateProperties
aa:PaymentOfContractTerminationCost
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:PaymentOfDisputedTaxAmountPercentage

aa:PaymentsForFinancialContributionsForTheDivestitureOfBusinesses
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:ProposedAdministrativePenalties

aa:RestructuringAndOtherCharges
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:Range, us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType
us-gaap:Range, us-gaap:StatementScenario
us-gaap:RealEstateProperties, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringPlan
us-gaap:RetirementPlanType
us-gaap:Range, us-gaap:RealEstateProperties
aa:RestructuringAndOtherChargesEstimatedButNotIncurred

aa:RestructuringAndOtherChargesNet
us-gaap:RestructuringCostAndReserve

aa:SegmentReportingInformationCorporateExpenses

aa:SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses
us-gaap:StatementBusinessSegments

aa:SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments
us-gaap:StatementBusinessSegments

aa:SegmentReportingInformationIntersegmentEliminations
us-gaap:ConsolidationItems
aa:SegmentReportingInformationIntersegmentRevenues
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems
aa:SegmentReportingInformationOtherIncomeExpenseNet

aa:SegmentReportingInformationTransformation
us-gaap:ConsolidationItems, us-gaap:RelatedPartyTransactionsByRelatedParty
aa:SegmentReportingInformationUnrelatedPartySales
us-gaap:ConsolidationItems, us-gaap:RelatedPartyTransactionsByRelatedParty, us-gaap:StatementBusinessSegments

aa:UnfavorableFavorableImpactIncomeTaxExpenseBenefit
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities
aa:WeightedAverageExercisePriceOfUnderwaterOptions

us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses

us-gaap:AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates
us-gaap:LossContingenciesByNatureOfContingency

us-gaap:AccrualForEnvironmentalLossContingenciesPayments1
us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType
us-gaap:AssetImpairmentCharges
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:HedgingDesignation
us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:DefinedBenefitPlanContributionsByEmployer
dei:LegalEntity, us-gaap:DebtInstrument
dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:SubsequentEventType
us-gaap:SubsequentEventType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:RetirementPlanName
us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:RetirementPlanName
us-gaap:RetirementPlanType
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RestructuringCostAndReserve
us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax

us-gaap:GainLossOnDispositionOfAssets

us-gaap:GainLossOnDispositionOfAssets1
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:ProductOrService
us-gaap:IncomeLossFromEquityMethodInvestments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

us-gaap:IncreaseDecreaseInAccountsPayableTrade

us-gaap:IncreaseDecreaseInAccruedLiabilities

us-gaap:IncreaseDecreaseInAccruedTaxesPayable

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

us-gaap:IncreaseDecreaseInOtherNoncurrentLiabilities

us-gaap:IncreaseDecreaseInPensionPlanObligations
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:RetirementPlanName

us-gaap:IncreaseDecreaseInPostretirementObligations
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:RetirementPlanName

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets

us-gaap:IncreaseDecreaseInReceivables

us-gaap:IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends
us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityCommitmentFeeAmount
us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityIncreaseDecreaseForPeriodNet
us-gaap:StatementScenario, us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:DebtInstrument
us-gaap:MaturitiesOfSeniorDebt
us-gaap:DebtInstrument, us-gaap:SubsequentEventType

us-gaap:OperatingLeaseCost

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:IncomeStatementLocation
us-gaap:DerivativeInstrumentRisk, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
us-gaap:DerivativeInstrumentRisk
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
us-gaap:StatementEquityComponents
us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax

us-gaap:OtherDepreciationAndAmortization

us-gaap:OtherNoncashIncomeExpense

us-gaap:PaymentsForRestructuring
us-gaap:RealEstateProperties
us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringPlan
us-gaap:StatementGeographical, us-gaap:RestructuringPlan

us-gaap:PaymentsOfDividendsMinorityInterest

us-gaap:PensionAndOtherPostretirementBenefitExpense

us-gaap:PensionContributions
us-gaap:RetirementPlanSponsorLocation
us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:ProceedsFromDivestitureOfBusinesses

us-gaap:ProceedsFromMinorityShareholders

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ProvisionForDoubtfulAccounts
us-gaap:RealEstateProperties
us-gaap:RestructuringReserveAccrualAdjustment1
us-gaap:RestructuringCostAndReserve
us-gaap:StatementGeographical, us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringPlan
us-gaap:RestructuringReserveTranslationAdjustment

us-gaap:RestructuringReserveTranslationAndOtherAdjustment
us-gaap:RestructuringCostAndReserve

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability

us-gaap:ShortTermLeaseCost

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation
us-gaap:StatementEquityComponents

us-gaap:StockholdersEquityOther
us-gaap:StatementEquityComponents
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
us-gaap:TaxAdjustmentsSettlementsAndUnusualProvisions

us-gaap:TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax

us-gaap:UnrealizedGainLossOnDerivatives

us-gaap:VariableLeaseCost

aa:AccrualEnvironmentalLossActiveRemediationFutureRemediationForSignificantIndividualSites

aa:AccrualForEnvironmentalLossContingenciesUndiscountedOneToFiveYear

aa:AccrualForEnvironmentalLossContingenciesUndiscountedTwoToFiveYear

aa:AccruedCappingClosurePostClosureAndEnvironmentalCost

aa:AccruedCompensationAndRetirementCostsNoncurrent

aa:AccruedTaxesNoncurrent
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
aa:AluminumForecastedSalesDesignatedAsFairValueHedgesInKiloMetricTon
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
aa:AluminumFuturesDesignatedAsFairValueHedgesInKiloMetricTon

aa:AmountCommittedUnderOutstandingSuretyBonds
us-gaap:StatementEquityComponents
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties
us-gaap:ConsolidatedEntities, us-gaap:StatementScenario, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:ClosureOfResidueAreas

aa:DeferredEnergyCredits

aa:DeferredTaxAssetsDepreciation

aa:DeferredTaxAssetsLeasingArrangements

aa:DeferredTaxLiabilitiesDepreciation

aa:DeferredTaxLiabilitiesGross
us-gaap:RetirementPlanType
aa:DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveLossAttributedToJointVenturePartners
us-gaap:RetirementPlanType
aa:DefinedBenefitPlanExpectedFutureBenefitPayments
us-gaap:RetirementPlanType
aa:DefinedBenefitPlanFundedAmountsAttributedToJointVenturePartners
us-gaap:RetirementPlanType
aa:DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect
us-gaap:RetirementPlanType
aa:DefinedBenefitPlanNetFundedStatus
us-gaap:RetirementPlanName
aa:DefinedBenefitPlanNumberOfEmployeesOnRollingOperations

aa:DefinedBenefitPlanNumberOfPlanParticipantsAffected
us-gaap:RetirementPlanName

aa:Demolition
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentGrossNoncurrent
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
aa:EquityMethodInvestmentUnrecognizedGainLoss
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:ExpectedFutureSiteSeparationAndTransactionCostsPayment

aa:GasSupplyPrepayment
us-gaap:ConsolidatedEntities, us-gaap:BalanceSheetLocation, us-gaap:FiniteLivedIntangibleAssetsByMajorClass, us-gaap:OtherOwnershipInterestsByName
us-gaap:ConsolidatedEntities, us-gaap:FiniteLivedIntangibleAssetsByMajorClass, us-gaap:OtherOwnershipInterestsByName
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType
us-gaap:CreditFacility
aa:IncrementalAmountOfConvenantMaximum
us-gaap:DerivativeInstrumentRisk
aa:IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate
us-gaap:CreditFacility
aa:InvestmentNegativeCovenantMaximum

aa:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
aa:LiabilitiesRecordedFromDisposalGroupIncludingDiscontinuedOperation
us-gaap:CreditFacility
aa:LineOfCreditFacilityMaximumAdditionalBorrowingCapacity

aa:MineReclamationAndClosingLiability

aa:MinimumRequiredCashContributionToPensionPlanExceptedFuturePaymentsRemainderOfFiscalYear
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType

aa:OutstandingReceivableForLaborAndOtherEmployeeRelatedExpenses
us-gaap:RetirementPlanType
aa:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesHeldForSale

aa:PrepaidGasTransmissionContract

aa:PropertiesPlantsAndEquipmentExcludingConstructionWorkInProgress

aa:ReceivablesExcludedFromPensionPlanAssets
us-gaap:CreditFacility
aa:RestrictedPaymentsNegativeCovenantMaximum

aa:SegmentReportingInformationEquityMethodInvestments
us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems
aa:SegmentReportingInformationIntersegmentReceivable

aa:SegmentReportingInformationReportedAssets
us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
aa:SegmentReportingReconcilingItemsGoodwillAssets

aa:SpentPotLiningDisposal
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
aa:TaxAssessmentDeposit

aa:TaxAssessmentDepositNoncurrent
us-gaap:CreditFacility
aa:ThresholdsForInvestmentsNegativeCovenants
us-gaap:CreditFacility
aa:ThresholdsForRestrictedPaymentsNegativeCovenants

us-gaap:AccrualForEnvironmentalLossContingencies
us-gaap:StatementGeographical

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueInRemainderOfFiscalYear

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear

us-gaap:AccruedEnvironmentalLossContingenciesCurrent

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent

us-gaap:AccruedIncomeTaxesNoncurrent
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName
us-gaap:StatementEquityComponents
us-gaap:AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax
us-gaap:StatementEquityComponents
us-gaap:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
us-gaap:StatementEquityComponents
us-gaap:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax

us-gaap:AssetRetirementObligation
us-gaap:Range, us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType

us-gaap:AssetRetirementObligationCurrent

us-gaap:AssetRetirementObligationsNoncurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperation

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:FairValueByMeasurementBasis
us-gaap:CashAndCashEquivalentsFairValueDisclosure
us-gaap:DebtInstrument
us-gaap:DebtInstrumentCarryingAmount
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:DebtInstrumentFaceAmount
us-gaap:FairValueByMeasurementBasis
us-gaap:DebtInstrumentFairValue

us-gaap:DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet

us-gaap:DeferredCosts

us-gaap:DeferredCreditsAndOtherLiabilitiesNoncurrent
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredIncomeTaxLiabilities
us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority
us-gaap:IncomeTaxAuthority

us-gaap:DeferredRevenueNoncurrent

us-gaap:DeferredTaxAssetInterestCarryforward

us-gaap:DeferredTaxAssetsDeferredIncome

us-gaap:DeferredTaxAssetsDerivativeInstruments

us-gaap:DeferredTaxAssetsGross
dei:LegalEntity
dei:LegalEntity, us-gaap:IncomeTaxAuthority
us-gaap:IncomeTaxAuthority

us-gaap:DeferredTaxAssetsInvestments

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards
us-gaap:ValuationAllowancesAndReservesType

us-gaap:DeferredTaxAssetsOther

us-gaap:DeferredTaxAssetsTaxCreditCarryforwards
us-gaap:ValuationAllowancesAndReservesType

us-gaap:DeferredTaxAssetsTaxCreditCarryforwardsOther
us-gaap:ValuationAllowancesAndReservesType

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves

us-gaap:DeferredTaxLiabilitiesDeferredExpense

us-gaap:DeferredTaxLiabilitiesLeasingArrangements

us-gaap:DeferredTaxLiabilitiesOther

us-gaap:DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries

us-gaap:DefinedBenefitPensionPlanLiabilitiesNoncurrent
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmountsRecognizedInBalanceSheet
us-gaap:RetirementPlanName
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
us-gaap:StatementScenario, us-gaap:RetirementPlanType
us-gaap:RetirementPlanName, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation
us-gaap:RetirementPlanSponsorLocation
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo

us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsCurrentFiscalYear

us-gaap:DefinedBenefitPlanFairValueOfPlanAssets
us-gaap:DefinedBenefitPlanByPlanAssetCategories
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:RetirementPlanName, us-gaap:RetirementPlanType
us-gaap:RetirementPlanSponsorLocation
us-gaap:RetirementPlanSponsorLocation
us-gaap:DefinedBenefitPlanFundedStatusOfPlan
us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets
us-gaap:DefinedBenefitPlanByPlanAssetCategories
us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage

us-gaap:DefinedBenefitPlanUltimateHealthCareCostTrendRate1
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanName
us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation
us-gaap:DerivativeAssets
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument, us-gaap:MeasurementInputType
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation

us-gaap:DerivativeAssetsCurrent
us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeAssetsNoncurrent
us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeLiabilities
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument, us-gaap:MeasurementInputType
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation
us-gaap:HedgingDesignation

us-gaap:DerivativeLiabilitiesCurrent
us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeLiabilitiesNoncurrent
us-gaap:DerivativeInstrumentRisk
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccruedIncomeTaxPayableNoncurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName
us-gaap:DisposalGroupIncludingDiscontinuedOperationConsideration
us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationInventoryCurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationPostretirementPlanBenefitObligationNoncurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent

us-gaap:EmployeeRelatedLiabilitiesCurrent

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions

us-gaap:EquityMethodInvestmentAggregateCost
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:StatementGeographical, us-gaap:IncomeStatementLocation
us-gaap:EquityMethodInvestmentOwnershipPercentage
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestments
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:StatementBusinessSegments
us-gaap:GoodwillImpairedAccumulatedImpairmentLoss

us-gaap:InventoryFinishedGoodsNetOfReserves

us-gaap:InventoryRawMaterialsNetOfReserves

us-gaap:InventorySuppliesNetOfReserves

us-gaap:InventoryWorkInProcessNetOfReserves

us-gaap:Investments

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths

us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear

us-gaap:LettersOfCreditOutstandingAmount
us-gaap:CreditFacility
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:CreditFacility
us-gaap:LineOfCredit
us-gaap:DebtInstrument
dei:LegalEntity, us-gaap:CreditFacility, us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
us-gaap:FairValueByMeasurementBasis
us-gaap:LongTermDebtFairValue

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
us-gaap:Ownership
us-gaap:MinorityInterestOwnershipPercentageByNoncontrollingOwners
us-gaap:Ownership, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:Ownership
us-gaap:MinorityInterestOwnershipPercentageByParent

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent

us-gaap:OperatingLossCarryforwards

us-gaap:OtherAssetsMiscellaneousNoncurrent

us-gaap:OtherIntangibleAssetsNet

us-gaap:OtherInventoryNetOfReserves

us-gaap:OtherInvestments

us-gaap:OtherPostretirementDefinedBenefitPlanLiabilitiesNoncurrent

us-gaap:OtherReceivablesNetCurrent

us-gaap:OtherSundryLiabilitiesNoncurrent
us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities
us-gaap:StatementGeographical, us-gaap:OtherOwnershipInterestsByName
us-gaap:PrepaidExpenseCurrentAndNoncurrent
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueAfterFifthYear
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInFifthYear
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInFourthYear
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInSecondYear
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInThirdYear
us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueWithinOneYear
us-gaap:FairValueByMeasurementBasis
us-gaap:RestrictedCash

us-gaap:RestrictedCashAndCashEquivalents

us-gaap:RestructuringReserve
us-gaap:RestructuringCostAndReserve
us-gaap:RestructuringPlan

us-gaap:RestructuringReserveNoncurrent
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice

us-gaap:UnrecognizedTaxBenefitsIncomeTaxPenaltiesAccrued

us-gaap:ValueAddedTaxReceivableNoncurrent

Plots across concepts


IncomeStatement
Other Comprehensive Income Loss Net Of Tax
Expenses
Other Nonoperating Income Expense
Balance Sheet
Finite Lived Intangible Assets Net
Assets
Operating Lease Right Of Use Asset
Current Assets
Prepaid Expense And Other Assets Current
NonCurrent Assets
Finite Lived Intangible Assets Net
PropertyPlantAndEquipmentNet
Property Plant And Equipment Net
Liabilities
Operating Lease Liability
Current Liabilities
Long Term Debt Current
Noncurrent Liabilities
Operating Lease Liability Noncurrent
Stockholders Equity
Accumulated Other Comprehensive Income Loss Net Of Tax
CashFlow
Net Cash Provided By Used In Financing Activities
NetCashProvidedByUsedInOperatingActivities
Net Cash Provided By Used In Operating Activities
NetCashProvidedByUsedInInvestingActivities
Payments To Acquire Investments
NetCashProvidedByUsedInFinancingActivities
Net Cash Provided By Used In Financing Activities
Shares
Weighted Average Number Of Shares Outstanding Basic
OperatingLeaseLiability
Operating Lease Liability Current
NonoperatingIncomeExpense
Other Nonoperating Income Expense
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Payments Due Year Four
FiniteLivedIntangibleAssets
Finite Lived Intangible Assets Net
InventoryNet
Inventory Work In Process Net Of Reserves

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding █▁190.0189.0NA186.0186.0187.0NA186.0186.0185.0NA186.0189.0188.0NA187.0186.0186.0NA182.0182.0182.0NANA
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic █▁187.0186.0NA186.0186.0186.0NA186.0186.0185.0NA186.0186.0186.0NA185.0184.0184.0NA182.471195182.471195182.471195NANA
us-gaap:EarningsPerShareBasic █▇▅▄▃▆▂▃▁▃▅▅▆▆▃▆▆▇▄▅▄▃1.660.94-0.02-0.26-1.060.43-1.63-1.19-2.17-1.070.23-0.220.40.81-1.060.610.411.23-0.68-0.06-0.29-1.15NANA
us-gaap:EarningsPerShareDiluted █▇▅▅▃▆▂▃▁▃▅▅▆▆▃▆▆▇▄▅▄▃1.630.93-0.02-0.26-1.060.43-1.63-1.19-2.17-1.070.23-0.220.390.8-1.060.60.41.21-0.68-0.06-0.29-1.15NANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
 Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁60.055.0NA51.047.059.0NA72.064.0NANANANANANANANANANANANANANANA
 Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁197.0173.0NA195.0209.0218.0NA233.0187.0NANANANANANANANANANANANANANANA
 Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁96.095.0NA72.085.073.0NA47.025.0NANANANANANANANANANANANANANANA
 Cost Ratio us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁741.0682.0NA552.0507.0585.0NA607.0976.0NANANANANANANANANANANANANANANA
 Net profit Margin us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁60.055.0NA51.047.059.0NA72.064.0NANANANANANANANANANANANANANANA
 Net profit Margin us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁197.0173.0NA195.0209.0218.0NA233.0187.0NANANANANANANANANANANANANANANA
 Net profit Margin us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁741.0682.0NA552.0507.0585.0NA607.0976.0NANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
 TTM Greenblatt ROC _ _█▇▄▄▃▆▁▃▂▅▇▇██▆▆▆█▃▅▄461.0312.037.022.0-105.0219.0-301.0-52.0-177.092.0369.0406.0410.0412.0216.0288.0237.0418.0-137.0106.056.0NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:ComprehensiveIncomeNetOfTax ▆▃▃▂▁▅▂▂▃▂▅▅▂█500.0-74.0-86.0-316.0-579.0156.0-428.0-365.0-273.0-468.0226.0221.0-427.0847.0NANANANA-388.0-270.0NANA-406.0-853.0
us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest ▇▅▇▆█▁▄▅▇███▄▇100.0-18.0135.043.0142.0-206.0-23.0-10.0110.0150.0165.0156.0-38.0112.0NANANANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest ▇▅▅▄▄▅▄▄▅▄▆▆▄█▁▅▅▇▄▄▅▅600.0-92.049.0-273.0-437.0-50.0-451.0-375.0-163.0-318.0376.0337.0-366.0893.0-1252.0-17.097.0479.0-374.0-274.039.034.0NANA
us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization ▄▅▂▂▁▂▂▃▄▄██2156.02292.01974.02038.01932.02025.02048.02120.02189.02180.02513.02485.0NANANANANANANANANANANANA
 us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁32.025.0NA28.024.026.0NA44.035.0NANANANANANANANANANANANANANANA
 us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁146.0123.0NA131.0130.0148.0NA147.0132.0NANANANANANANANANANANANANANANA
 us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁78.063.0NA65.075.067.0NA45.023.0NANANANANANANANANANANANANANANA
 us-gaap:CostOfRevenue us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁508.0503.0NA435.0446.0462.0NA497.0821.0NANANANANANANANANANANANANANANA
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest █▇▆▆▅▇▄▅▄▆▇███▇▇▇█▅▆▆▄▁▆461.0312.037.022.0-105.0219.0-301.0-52.0-177.092.0369.0406.0410.0412.0216.0288.0237.0418.0-137.0106.056.0-197.0-798.014.0
us-gaap:IncomeTaxExpenseBenefit ▄▃▁▂▂▃▂▃▄▅▅▇▆▄█▄▃▄▁▃▃▁▃▃111.093.020.042.045.080.054.095.0116.0150.0157.0251.0180.0138.0272.0119.099.0110.06.092.068.018.092.077.0
us-gaap:InterestExpense █▄▄▄▂▂▂▂▂▂▂▂▂▁▁▁▁▁▄██▇▇█67.042.043.041.032.030.031.030.030.030.031.033.032.026.027.026.025.026.046.067.066.064.062.069.0
us-gaap:NetIncomeLoss █▇▆▆▅▇▄▅▄▅▆▆▇▇▅▇▇▇▅▆▆▅▁▅309.0175.0-4.0-49.0-197.080.0-303.0-221.0-402.0-199.043.0-41.075.0150.0-196.0113.075.0225.0-125.0-6.0-55.0-210.0-826.0-124.0
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest ▄▄▃▄▄▄▁▅▆▇▇█▇▆▆▄▄▅▃▃▄▃▁▄41.044.021.029.047.059.0-52.074.0109.0141.0169.0196.0155.0124.0140.056.063.083.0-4.020.043.0-5.0-64.061.0
us-gaap:NonoperatingIncomeExpense ▇▄▁▁▁█▁▂▁▁▂▃▃▂▃▂▃▇▃▇▄▁▁▃105.024.0-44.0-45.0-51.0132.0-44.0-27.0-50.0-41.0-32.0-2.0-9.0-21.0-9.0-27.0-6.0100.0-1.0106.023.0-39.0-51.0-4.0
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax ▂▂▂▂▁█▂▄▄▂▆▃▂-261.0-207.0-247.0-240.0-391.0681.0-186.058.078.0-282.0377.0-24.0-185.0NANANANANANANANANANANA
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▇▅█▆▇▂▇▅▆▆▆▅▃▆▅▇▅█▄▆▇█▇▁255.0-236.0422.022.0229.0-908.0162.0-299.044.0-20.0-28.0-196.0-596.0-13.0-118.0185.0-136.0353.0-315.077.0198.0355.0262.0-1041.0
us-gaap:OtherComprehensiveIncomeLossNetOfTax ▇▄▆▅▅▅▅▅▆▅▆▆▃█▁▅▅▆▅▅▆▇▇▃250.0-311.032.0-253.0-287.0-189.0-96.0-228.0130.0-260.0164.0182.0-596.0619.0-1196.0-186.0-41.0171.0-245.0-284.051.0249.0484.0-790.0
us-gaap:OtherNonoperatingIncomeExpense ▃▁▂▁▂█▃▅▇▅▄▄▆0.0-3.0-1.0-3.0-1.09.01.04.07.04.03.02.05.0NA-1.0-6.09.00.01.0-4.015.00.01.0-1.0
us-gaap:ProfitLoss █▇▆▆▅▇▄▅▄▆▇▇▇█▆▇▇█▅▆▆▅▁▆350.0219.017.0-20.0-150.0139.0-355.0-147.0-293.0-58.0212.0155.0230.0274.0-56.0169.0138.0308.0-129.014.0-12.0-215.0-890.0-63.0
us-gaap:ResearchAndDevelopmentExpense ▂▂▄▂▁▂▂▂▂▂▂▂▄▃▄▃▃▂▂▃▂▅█▇6.07.09.06.05.07.06.07.07.07.07.07.09.08.09.08.08.07.07.08.07.011.015.014.0
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ▅▅▃▃▂▃▃▄▄▄▇▇█▆▆▅▅▄▄▃▂▁▃▄2833.02870.02392.02365.02148.02381.02436.02567.02711.02719.03344.03390.03579.03090.03174.02964.02859.02655.02537.02329.02061.01892.02451.02679.0
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems us-gaap:OperatingSegments▆▆▆▆▅▆▆▆▆▆▇▇█▇▇▆▆▆▁▇▅▅▇█3354.03416.02928.02927.02680.02950.02999.03172.03383.03353.04135.04140.04324.03779.03971.03535.03412.03194.0-41.03845.02790.02593.04183.04551.0
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Alumina▃▄▂▃▂▃▃▄▅▅██▇▅▇▃▄▃▃▂▂▁▃▅1031.01124.0934.01026.0892.01043.01048.01140.01309.01314.01699.01645.01604.01368.01517.01111.01133.01095.0995.0902.0922.0788.01064.01274.0
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Aluminum▄▄▃▃▂▃▃▃▃▃▄▄▅▄▄▄▄▃█▁▃▃▁▂2105.02049.01690.01609.01477.01601.01640.01681.01761.01738.02111.02204.02417.02115.02148.02099.01991.01810.03751.0918.01599.01586.01062.01134.0
 us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Bauxite▁▂▆▅▆▆▆█▆▅▇▅▅▅▆▇▅▅▅▅▄▁▅▇218.0243.0304.0292.0311.0306.0311.0351.0313.0301.0325.0291.0303.0296.0306.0325.0288.0289.0293.0285.0269.0219.0301.0331.0
 us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁60.055.0NA51.047.059.0NA72.064.0NANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁197.0173.0NA195.0209.0218.0NA233.0187.0NANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁96.095.0NA72.085.073.0NA47.025.0NANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees█▁741.0682.0NA552.0507.0585.0NA607.0976.0NANANANANANANANANANANANANANANA
us-gaap:SellingGeneralAndAdministrativeExpense ▂▂▃▁▁▃▃▄▄▆▃▃▄▄▅▅▅▅██▇▇██54.052.055.047.044.060.062.066.068.084.059.058.064.067.070.070.072.072.092.092.090.085.092.095.0
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:Assets ▃▄▄▃▁▂▃▃▄▅▅▆▆▇██▇▇▇█14438.014931.014860.014250.013300.013651.014631.014670.015349.015956.015938.016185.016518.017096.017447.017254.016929.017076.016741.017305.0NANA16413.0NA
us-gaap:Liabilities ▄▇▆▄▁▁▃▂▃▄▃▄▅▅█▄▃▄▄▂9020.010058.09844.09231.07976.07840.08745.08260.08490.08873.08544.08900.09410.09579.010649.09136.08730.08913.09044.08179.0NANA4900.0NA
us-gaap:LiabilitiesAndStockholdersEquity ▃▄▄▃▁▂▃▃▄▅▅▆▆▇██▇▇▇█14438.014931.014860.014250.013300.013651.014631.014670.015349.015956.015938.016185.016518.017096.017447.017254.016929.017076.016741.017305.0NANA16413.0NA
us-gaap:StockholdersEquity ▂▁▁▁▂▃▃▃▄▅▅▅▄▅▃▆▆▆▆█3769.03248.03311.03395.03705.04275.04112.04539.04895.05157.05389.05216.05024.05368.04523.05862.05954.05876.05654.06980.0NANA9442.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:AssetsCurrent ▅█▆▅▁▂▂▃▄▅▅▅▆▅▅▄▃▂▁▃4201.04891.04520.04053.03179.03333.03530.03643.03818.04114.04134.04193.04281.04149.04238.03804.03583.03404.03181.03622.0NANA2566.0NA
us-gaap:CashAndCashEquivalentsAtCarryingValue ▅█▅▆▃▃▃▃▃▃▄▃▄▄▄▄▃▃▃▁▁▁▂▂1652.02544.01607.01736.0965.0829.0879.0841.0834.01017.01113.01022.01089.01196.01358.01119.0954.0804.0853.0241.0332.0359.0557.0521.0
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents ▄█▄▅▂▁▁▁▁▂▂▂▂▃▃▂▂▁▁1655.02547.01610.01739.0968.0832.0883.0844.0837.01020.01116.01026.01095.01203.01365.01127.0965.0822.0859.0NANANA557.0NA
us-gaap:AccountsReceivableNetCurrent ▄▃▂▂▁▃▃▃▄▅▆██▆▆▆▅▄▄▂644.0587.0471.0516.0402.0570.0546.0596.0684.0758.0830.01017.01025.0814.0811.0840.0789.0708.0668.0530.0NANA380.0NA
us-gaap:InventoryNet ▅▄▄▄▄▅▆▆██▆▇▇▆▄▃▂▂▁▁1547.01417.01398.01398.01419.01509.01644.01649.01767.01799.01644.01666.01668.01630.01453.01323.01287.01294.01160.01192.0NANA1172.0NA
us-gaap:PrepaidExpenseAndOtherAssetsCurrent ▂▂▃▄▃▃▃▂▂▃▄▂▃▃▃▁▅█▅▃233.0238.0290.0297.0264.0277.0288.0245.0250.0285.0301.0255.0283.0270.0271.0217.0347.0424.0334.0269.0NANA333.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
 us-gaap:AssetsNoncurrent us-gaap:ProductOrService aa:EnergyNANA401.0NANANA509.0NANANANANANANANANANANANANANANANANA
 us-gaap:AssetsNoncurrent us-gaap:ProductOrService aa:OtherProductsNANA757.0NANANA761.0NANANANANANANANANANANANANANANANANA
 us-gaap:AssetsNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:HalcoMiningIncNANA828.0NANANA923.0NANANANANANANANANANANANANANANANANA
 us-gaap:AssetsNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:MaadenJointVentureNANA7648.0NANANA7931.0NANANANANANANANANANANANANANANANANA
us-gaap:PropertyPlantAndEquipmentGross ▇▆▇▇▇▆▇▇▇▇▇▇▇█▁█████20551.020199.020522.021061.020877.020181.021715.021456.022126.022015.021807.021839.022079.022837.09138.023253.022971.023076.022550.023145.0NANA22118.0NA
us-gaap:ConstructionInProgressGross NANA335.0NANANA321.0NANANA406.0NANANA387.0NANANA498.0NANANA484.0NA
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment ▅▃▃▇▅▁▇▅▇▆▄▄▅▇██▆▆▃▅13575.013269.013332.013811.013588.013021.013799.013527.013853.013687.013480.013484.013523.013803.013908.013971.013734.013642.013225.013536.0NANA12728.0NA
us-gaap:PropertyPlantAndEquipmentNet ▁▁▂▂▂▂▄▄▅▅▅▅▅▆▇▇▇█▇█6976.06930.07190.07250.07289.07160.07916.07929.08273.08328.08327.08355.08556.09034.09138.09282.09237.09434.09325.09609.0NANA9390.0NA
us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures ▂▁▁▁▁▁▂▂▃▇▇▇████▇█▇1113.01055.01051.01034.01037.01059.01113.01114.01141.01362.01360.01381.01390.01413.01410.01408.01378.01393.01358.0NANANANANA
us-gaap:Goodwill NANA145.0NANANA150.0NANANA989.0NANANA989.0NANANA155.0155.0NANA152.0NA
 us-gaap:Goodwill dei:LegalEntity,us-gaap:StatementBusinessSegments aa:AlcoaCorporation,aa:AluminaNANA96.0NANANA100.0NANANA100.0NANANA103.0NANANA103.0NANANANANA
 us-gaap:Goodwill dei:LegalEntity,us-gaap:StatementBusinessSegments aa:AlcoaCorporation,aa:BauxiteNANA49.0NANANA50.0NANANA51.0NANANA51.0NANANA52.0NANANANANA
 us-gaap:Goodwill us-gaap:BalanceSheetLocation us-gaap:OtherNoncurrentAssetsNANA145.0NANANA150.0NANANA151.0NANANA154.0NANANA155.0NANANANANA
 us-gaap:Goodwill us-gaap:BalanceSheetLocation,us-gaap:StatementBusinessSegments us-gaap:OtherNoncurrentAssets,aa:AluminaNANA2.0NANANA3.0NANANA3.0NANANA4.0NANANA4.0NANANANANA
 us-gaap:Goodwill us-gaap:BalanceSheetLocation,us-gaap:StatementBusinessSegments us-gaap:OtherNoncurrentAssets,us-gaap:CorporateNANA141.0NANANA145.0NANANA146.0NANANA148.0NANANA149.0NANANANANA
 us-gaap:Goodwill us-gaap:ConsolidationItems us-gaap:MaterialReconcilingItemsNANA141.0NANANA145.0NANANA146.0NANANA148.0NANANA149.0NANANA147.0NA
us-gaap:FiniteLivedIntangibleAssetsNet NANA45.0NANANA52.0NANANA57.0NANANA62.0NANANANANANANANANA
 us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass aa:PatentLicenseAgreementNANA17.0NANANA17.0NANANA18.0NANANA19.0NANANANANANANANANA
 us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass us-gaap:ComputerSoftwareIntangibleAssetNANA18.0NANANA24.0NANANA26.0NANANA29.0NANANANANANANANANA
 us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass us-gaap:OtherIntangibleAssetsNANA10.0NANANA11.0NANANA13.0NANANA14.0NANANANANANANANANA
us-gaap:DeferredTaxAssetsLiabilitiesNet NANA451.0NANANA410.0NANANA301.0NANANA517.0562.0436.0NA449.0NANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaAluminio,us-gaap:ForeignCountryNANA166.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaCanadaCompany,us-gaap:ForeignCountryNANA148.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaLauralcoManagementCompany,us-gaap:ForeignCountryNANA38.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaWolinbecCompany,us-gaap:ForeignCountryNANA38.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaWorldAluminaBrasil,us-gaap:ForeignCountryNANA80.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:ConsolidationItems us-gaap:MaterialReconcilingItemsNANA655.0NANANA642.0NANANA563.0NANANA814.0NANANA741.0NANANA589.0NA
 us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:IncomeTaxAuthority us-gaap:DomesticCountryNANA7.0NANANA7.0NANANA10.0NANANA6.0NANANA17.0NANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:IncomeTaxAuthority us-gaap:ForeignCountryNANA444.0NANANA403.0NANANA291.0NANANA511.0NA432.0NA432.0NANANANANA
us-gaap:OperatingLeaseRightOfUseAsset ▁▂▃▄▃▃▅▅▇█122.0131.0137.0147.0141.0141.0154.0158.0175.0185.0NANANANANANANANANANANANANANA
us-gaap:OtherAssetsNoncurrent ▄▃▄▃▂▁▃▃▄▄▄▆▇▇██▇▇▇▅1416.01402.01444.01372.01308.01228.01412.01377.01463.01480.01475.01615.01635.01701.01719.01745.01688.01674.01668.01534.0NANA1247.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:AccountsPayableCurrent ▃▁▃▂▁▁▄▃▄▄▅▆▆▇█▅▄▃▃▁1392.01284.01403.01360.01253.01276.01484.01418.01523.01503.01663.01711.01752.01813.01898.01618.01508.01434.01455.01252.0NANA1379.0NA
us-gaap:LiabilitiesCurrent ▄█▅▂▁▁▃▃▃▅▆▆▆▆█▅▄▄▅▁2671.03221.02761.02303.02241.02223.02563.02455.02531.02803.02919.03004.03013.02976.03252.02766.02608.02623.02821.02206.0NANA2404.0NA
us-gaap:LongTermDebtCurrent NANA2.0NANANA1.0NANANA1.0NANANA16.0NANANA21.0NANANA18.0NA
us-gaap:OperatingLeaseLiabilityCurrent ▁▄▇▇▆▅█49.054.060.060.058.056.061.0NANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesCurrent ▅▅▅▃▃▃▄▄▃▃▂▁▂▁▃▂▄▅█▂538.0554.0525.0415.0451.0435.0494.0484.0427.0437.0347.0319.0353.0294.0412.0376.0492.0568.0742.0390.0NANA558.0NA
us-gaap:TaxesPayableCurrent ▂▂▂▁▂▁▂▁▂▇██▆▆▅▃▃▃▃▂126.092.091.057.096.078.0104.081.0100.0395.0426.0417.0323.0325.0282.0166.0144.0176.0147.0110.0NANA136.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
 us-gaap:LiabilitiesNoncurrent us-gaap:ProductOrService aa:EnergyNANA113.0NANANA87.0NANANANANANANANANANANANANANANANANA
 us-gaap:LiabilitiesNoncurrent us-gaap:ProductOrService aa:OtherProductsNANA62.0NANANA42.0NANANANANANANANANANANANANANANANANA
 us-gaap:LiabilitiesNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:HalcoMiningIncNANA331.0NANANA511.0NANANANANANANANANANANANANANANANANA
 us-gaap:LiabilitiesNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:MaadenJointVentureNANA5347.0NANANA5587.0NANANANANANANANANANANANANANANANANA
us-gaap:LongTermDebt NANA2465.0NANANA1800.0NANANA1802.0NANANA1404.0NANANA1445.0NANANA225.0NA
us-gaap:LongTermDebtNoncurrent NANA2463.0NANANA1799.0NANA1802.01801.0NANANA1388.0NANANA1424.0NANANA207.0NA
us-gaap:LongTermDebtAndCapitalLeaseObligations ▅▅▇█▁▁▁▁▁2216.02214.02463.02538.01800.01801.01799.01805.01804.0NA1801.01820.01916.01445.01388.01384.01418.01431.01424.01457.0NANA207.0NA
 us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType us-gaap:OtherPostretirementBenefitPlansDefinedBenefitNANA744.0NANANA749.0NANANA868.0NANANA1100.0NANANA1166.0NANANANANA
 us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType us-gaap:PensionPlansDefinedBenefitNANA1492.0NANANA1505.0NANANA1407.0NANANA2341.0NANANA1851.0NANANANANA
us-gaap:MinorityInterest ▂▂▃▂▂▁▃▄▅▅▅▆▆▇████▆▇1649.01625.01705.01624.01619.01536.01774.01871.01964.01926.02005.02069.02084.02149.02275.02256.02245.02287.02043.02146.0NANA2071.0NA
us-gaap:OperatingLeaseLiabilityNoncurrent ▁▂▃▆▅▅█76.080.082.092.090.090.0100.0NANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo ▂▁█▇24.023.033.032.0NANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree ▂▁█▇15.014.021.020.0NANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour ▁▁██9.09.013.013.0NANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive NANA8.0NANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive NANA22.0NANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:StockholdersEquity ▂▁▁▁▂▃▃▃▄▅▅▅▄▅▃▆▆▆▆█3769.03248.03311.03395.03705.04275.04112.04539.04895.05157.05389.05216.05024.05368.04523.05862.05954.05876.05654.06980.0NANA9442.0NA
us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest ▂▁▁▁▁▂▂▃▃▃▄▃▃▄▃▄▄▄▄▅████5418.04873.05016.05019.05324.05811.05886.06410.06859.07083.07394.07285.07108.07517.06798.08118.08199.08163.07697.09126.011861.011813.011513.011787.0
us-gaap:AdditionalPaidInCapitalCommonStock █▇▇▇▆▆▆▆▅▅▄▆▆▅▄▃▂▂▁9695.09674.09663.09661.09655.09647.09639.09638.09629.09618.09611.09656.09650.09633.09590.09584.09559.09553.09531.0NANANANANA
us-gaap:RetainedEarningsAccumulatedDeficit ▄▂▁▁▁▃▂▄▅████▇▆█▇▆▅-241.0-550.0-725.0-721.0-672.0-476.0-555.0-252.0-31.0371.0341.0298.0339.0263.0113.0309.0196.0121.0-104.0NANANANANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▂▁▂▂▃▄▄▄▅▄▅▅▄▅▃▇███▆-5687.0-5878.0-5629.0-5547.0-5280.0-4898.0-4974.0-4849.0-4705.0-4834.0-4565.0-4740.0-4967.0-4530.0-5182.0-4033.0-3803.0-3800.0-3775.0-4478.0NANA-1600.0NA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:NoncontrollingInterest▄▃▄▂▂▁▄▄▅▅▅▅▆██-915.0-974.0-912.0-1026.0-1040.0-1135.0-870.0-899.0-815.0-816.0-825.0-814.0-769.0-610.0-577.0NANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:Parent▂▁▂▃▄▆▆▆▇▆█▇▆█▅-5687.0-5878.0-5629.0-5547.0-5280.0-4898.0-4974.0-4849.0-4705.0-4834.0-4565.0-4740.0-4967.0-4530.0-5182.0NANANANANANANANANA
us-gaap:MinorityInterest ▂▂▃▂▂▁▃▄▅▅▅▆▆▇████▆▇1649.01625.01705.01624.01619.01536.01774.01871.01964.01926.02005.02069.02084.02149.02275.02256.02245.02287.02043.02146.0NANA2071.0NA
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue ▇▆▁▅▇▆▁▆█▇▄▇▇▇▂▅▅▅10.08.01.07.09.08.01.08.011.010.06.09.010.010.03.07.07.07.0NANANANANANA
us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders ▂▂▂▁▂▁▃▃▂▆█▅▄█▃▃▃▂▂▃▁▂▁75.062.055.046.075.031.084.0102.072.0214.0261.0181.0118.0267.098.089.098.057.057.092.034.050.035.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:NetCashProvidedByUsedInOperatingActivities ▃▄▄▅▆▃▆▅▅▅█▆▁▅▇▇▆▅▆-86.06.038.0158.0288.0-90.0262.0174.082.0168.0535.0288.0-430.055.0455.0384.0311.074.0239.0NANA-359.053.0NA
us-gaap:NetCashProvidedByUsedInInvestingActivities ▃█▂▂▂▄▂▂▁▂▂▂▂▂▁▂34.0514.0-117.0-78.0-79.0107.0-134.0-76.0-199.0-59.0-148.0-83.0-100.0-74.0-170.0-104.0NANANANANANANANA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▇▅█▅▅▄▄▅▄▄▄▇▄▅▄-849.0428.0-63.0692.0-71.0-44.0-93.0-81.0-71.0-199.0-294.0-280.0433.0-147.0-53.0-115.0NANANANANANANANA
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect ▁█▄▇▅▄▅▄▄▄▅▄▄▄▅▅▅▄-892.0937.0-129.0771.0136.0-51.039.07.0-183.0-96.090.0-69.0-108.0-162.0238.0162.0143.0-37.0NANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:DeferredIncomeTaxExpenseBenefit ▄▄▃▃▂▄▁▃▅▅▂▄▂▃█▄▄▄▁▅30.018.0-14.0-6.0-29.023.0-44.0-5.031.033.0-20.015.0-20.0-11.0112.014.027.023.0-52.034.0NANA103.0NA
us-gaap:DepreciationDepletionAndAmortization ▂▆▄▂▁▄▆▆▅▄▅▄██▇█▇▆▆▆▅▅▇▇161.0182.0170.0161.0152.0170.0183.0184.0174.0172.0174.0173.0192.0194.0187.0194.0190.0179.0182.0181.0178.0177.0186.0190.0
us-gaap:IncreaseDecreaseInInventories ▇▆▆▃▁▃▄▃▃▄▄▄▆█▇▅▄▆▅▅▃▄▂116.068.099.0-37.0-143.0-41.0-26.0-58.0-36.0-17.0-1.012.098.0169.0136.016.0-16.0102.024.017.0-34.0-8.0-120.0NA
us-gaap:NetCashProvidedByUsedInOperatingActivities ▃▄▄▅▆▃▆▅▅▅█▆▁▅▇▇▆▅▆-86.06.038.0158.0288.0-90.0262.0174.082.0168.0535.0288.0-430.055.0455.0384.0311.074.0239.0NANA-359.053.0NA
us-gaap:NetIncomeLoss █▇▆▆▅▇▄▅▄▅▆▆▇▇▅▇▇▇▅▆▆▅▁▅309.0175.0-4.0-49.0-197.080.0-303.0-221.0-402.0-199.043.0-41.075.0150.0-196.0113.075.0225.0-125.0-6.0-55.0-210.0-826.0-124.0
us-gaap:ProfitLoss █▇▆▆▅▇▄▅▄▆▇▇▇█▆▇▇█▅▆▆▅▁▆350.0219.017.0-20.0-150.0139.0-355.0-147.0-293.0-58.0212.0155.0230.0274.0-56.0169.0138.0308.0-129.014.0-12.0-215.0-890.0-63.0
us-gaap:ShareBasedCompensation ▇▆▁▅▇▆▁▆█▇▄▇▇▇▂▅▅▅▃▄▇▆▃10.08.01.07.09.08.01.08.011.010.06.09.010.010.03.07.07.07.04.06.010.08.04.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:NetCashProvidedByUsedInInvestingActivities ▃█▂▂▂▄▂▂▁▂▂▂▂▂▁▂34.0514.0-117.0-78.0-79.0107.0-134.0-76.0-199.0-59.0-148.0-83.0-100.0-74.0-170.0-104.0NANANANANANANANA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▂▂▅▁▂▃▇▃▃▁█▂▃▁█▃▃▁█▂▂▂▇79.075.0111.074.077.091.0134.087.089.069.0148.082.095.074.0150.096.088.071.0146.086.086.086.0133.0NA
us-gaap:PaymentsToAcquireInvestments ▁▁▁▁▁▁▁▁█▁▁▁1.02.06.03.02.01.00.01.0110.01.01.01.0NANA22.08.011.025.00.00.00.03.027.0NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▇▅█▅▅▄▄▅▄▄▄▇▄▅▄-849.0428.0-63.0692.0-71.0-44.0-93.0-81.0-71.0-199.0-294.0-280.0433.0-147.0-53.0-115.0NANANANANANANANA
 us-gaap:ProceedsFromIssuanceOfLongTermDebt dei:LegalEntity,us-gaap:DebtInstrument aa:AlcoaNederlandHoldingBV,aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySevenNANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:ProceedsFromIssuanceOfLongTermDebt dei:LegalEntity,us-gaap:DebtInstrument aa:AlcoaNederlandHoldingBV,aa:FourPointOneTwoFivePercentageSeniorNotesDueTwoThousandAndTwentyNineNA493.0NANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
 us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:CreditFacility,us-gaap:DebtInstrument us-gaap:RevolvingCreditFacility,aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySevenNA5.5e-06NANANANANANANANANANANANANANANANANANANANANANA

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-31
Value190189186186187186186185186189188187186186182182182
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-31
Value187186186186186186186185186186186185184184182182182
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value1.660.94-0.02-0.26-1.060.43-1.63-1.19-2.17-1.070.23-0.220.40.81-1.060.610.411.23-0.68-0.06-0.29-1.15
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value1.630.93-0.02-0.26-1.060.43-1.63-1.19-2.17-1.070.23-0.220.390.8-1.060.60.41.21-0.68-0.06-0.29-1.15
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312016-12-312016-09-302015-12-312015-09-30
Value500-74.0-86.0-316.0-579.0156-428.0-365.0-273.0-468.0226221-427.0847-388.0-270.0-406.0-853.0
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.6-2.6-3.6-13.4-27.06.6-17.6-14.2-10.1-17.26.86.5-11.927.4-15.3-11.6-16.6-31.8

Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value100-18.013543142-206.0-23.0-10.0110150165156-38.0112
Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.5-0.65.61.86.6-8.7-0.9-0.44.15.54.94.6-1.13.6

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value600-92.049-273.0-437.0-50.0-451.0-375.0-163.0-318.0376337-366.0893-1252.0-17.097479-374.0-274.03934
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax21.2-3.22.0-11.5-20.3-2.1-18.5-14.6-6.0-11.711.29.9-10.228.9-39.4-0.63.418.0-14.7-11.81.91.8

Cost Of Goods And Service Excluding Depreciation Depletion And Amortization

us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization

us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value215622921974203819322025204821202189218025132485
Percentage of CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax76.179.982.586.289.985.084.182.680.780.275.173.3

Cost Of Revenue

us-gaap:CostOfRevenue us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:CostOfRevenue

aa:Energy, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value32252824264435
Percentage of CostOfRevenue100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.10.91.21.11.11.71.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:Mining, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value146123131130148147132
Percentage of CostOfRevenue456.2492.0467.9541.7569.2334.1377.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.24.35.56.16.25.74.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:OtherProducts, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value78636575674523
Percentage of CostOfRevenue243.8252.0232.1312.5257.7102.365.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.82.22.73.52.81.80.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

us-gaap:CostOfRevenue us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:MaadenJointVenture, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value508503435446462497821
Percentage of CostOfRevenue1587.52012.01553.61858.31776.91129.52345.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.917.518.420.819.419.430.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

Gains Losses On Extinguishment Of Debt

us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument

us-gaap:GainsLossesOnExtinguishmentOfDebt

aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour


Gains
Period End2021-06-30
Value-32000000.0
Percentage of GainsLossesOnExtinguishmentOfDebt100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour0.0

us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:StatementScenario, us-gaap:DebtInstrument

srt:ScenarioForecast, aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour


Gains
Period End2021-06-30
Value-32000000.0
Percentage of GainsLossesOnExtinguishmentOfDebt100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:ScenarioForecast aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour0.0

Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value4613123722-105.0219-301.0-52.0-177.092369406410412216288237418-137.010656-197.0-798.014
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.310.91.50.9-4.99.2-12.4-2.0-6.53.411.012.011.513.36.89.78.315.7-5.44.62.7-10.4-32.60.5

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value11193204245805495116150157251180138272119991106.09268189277
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.93.20.81.82.13.42.23.74.35.54.77.45.04.58.64.03.54.10.24.03.31.03.82.9

Interest Expense

us-gaap:InterestExpense

us-gaap:InterestExpense


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value674243413230313030303133322627262526466766646269
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.41.51.81.71.51.31.31.21.11.10.91.00.90.80.90.90.91.01.82.93.23.42.52.6

us-gaap:InterestExpense us-gaap:ConsolidationItems

us-gaap:MaterialReconcilingItems


Interest
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value413230313030303133322627262526466766646269
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.71.51.31.31.21.11.10.91.00.90.80.90.90.91.01.82.93.23.42.52.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MaterialReconcilingItems0.00.00.00.00.00.00.00.0-206.2-160.00.00.0-104.0-227.30.00.00.00.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value309175-4.0-49.0-197.080-303.0-221.0-402.0-199.043-41.075150-196.011375225-125.0-6.0-55.0-210.0-826.0-124.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.96.1-0.2-2.1-9.23.4-12.4-8.6-14.8-7.31.3-1.22.14.9-6.23.82.68.5-4.9-0.3-2.7-11.1-33.7-4.6

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value414421294759-52.074109141169196155124140566383-4.02043-5.0-64.061
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.41.50.91.22.22.5-2.12.94.05.25.15.84.34.04.41.92.23.1-0.20.92.1-0.3-2.62.3

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value10524-44.0-45.0-51.0132-44.0-27.0-50.0-41.0-32.0-2.0-9.0-21.0-9.0-27.0-6.0100-1.010623-39.0-51.0-4.0
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.70.8-1.8-1.9-2.45.5-1.8-1.1-1.8-1.5-1.0-0.1-0.3-0.7-0.3-0.9-0.23.8-0.04.61.1-2.1-2.1-0.1

Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-261.0-207.0-247.0-240.0-391.0681-186.05878-282.0377-24.0-185.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-9.2-7.2-10.3-10.1-18.228.6-7.62.32.9-10.411.3-0.7-5.2

Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value255-236.042222229-908.0162-299.044-20.0-28.0-196.0-596.0-13.0-118.0185-136.0353-315.077198355262-1041.0
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.0-8.217.60.910.7-38.16.7-11.61.6-0.7-0.8-5.8-16.7-0.4-3.76.2-4.813.3-12.43.39.618.810.7-38.9

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value51-60.01241794-245.045-75.04.02.0-10.0-54.0-151.0-14.0-25.044-37.0114-82.0453210788-298.0
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax20.025.429.477.341.027.027.825.19.1-10.035.727.625.3107.721.223.827.232.326.058.416.230.133.628.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.8-2.15.20.74.4-10.31.8-2.90.10.1-0.3-1.6-4.2-0.5-0.81.5-1.34.3-3.21.91.65.73.6-11.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value204-176.02985.0135-663.0117-224.040-22.0-18.0-142.0-445.01.0-93.0141-99.0
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax80.074.670.622.759.073.072.274.990.9110.064.372.474.7-7.778.876.272.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.2-6.112.50.26.3-27.84.8-8.71.5-0.8-0.5-4.2-12.40.0-2.94.8-3.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:Parent0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Comprehensive Income Loss Net Of Tax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value250-311.032-253.0-287.0-189.0-96.0-228.0130-260.0164182-596.0619-1196.0-186.0-41.0171-245.0-284.051249484-790.0
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.8-10.81.3-10.7-13.4-7.9-3.9-8.94.8-9.64.95.4-16.720.0-37.7-6.3-1.46.4-9.7-12.22.513.219.7-29.5

us-gaap:OtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value191-249.0-82.0-267.0-382.076-125.0-144.0129-269.0175227-437.0652-1149.0-230.0-3.0-25.0-161.0-318.01.0143400-502.0
Percentage of OtherComprehensiveIncomeLossNetOfTax76.480.1-256.2105.5133.1-40.2130.263.299.2103.5106.7124.773.3105.396.1123.77.3-14.665.7112.02.057.482.663.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.7-8.7-3.4-11.3-17.83.2-5.1-5.64.8-9.95.26.7-12.221.1-36.2-7.8-0.1-0.9-6.3-13.70.07.616.3-18.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value59-62.01141495-265.029-84.01.09.0-11.0-45.0-159.0-33.0-47.044-38.0196-84.0345010684-288.0
Percentage of OtherComprehensiveIncomeLossNetOfTax23.619.9356.2-5.5-33.1140.2-30.236.80.8-3.5-6.7-24.726.7-5.33.9-23.792.7114.634.3-12.098.042.617.436.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.1-2.24.80.64.4-11.11.2-3.30.00.3-0.3-1.3-4.4-1.1-1.51.5-1.37.4-3.31.52.45.63.4-10.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value0.0-3.0-1.0-3.0-1.09.01.04.07.04.03.02.05.0-1.0-6.09.00.01.0-4.0150.01.0-1.0
Percentage of OtherNonoperatingIncomeExpense0.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.0-0.1-0.0-0.1-0.00.40.00.20.30.10.10.10.1-0.0-0.20.30.00.0-0.20.70.00.0-0.0

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value35021917-20.0-150.0139-355.0-147.0-293.0-58.0212155230274-56.0169138308-129.014-12.0-215.0-890.0-63.0
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax12.47.60.7-0.8-7.05.8-14.6-5.7-10.8-2.16.34.66.48.9-1.85.74.811.6-5.10.6-0.6-11.4-36.3-2.4

us-gaap:ProfitLoss us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:Energy, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value27252820272326
Percentage of ProfitLoss7.711.4-140.0-13.319.4-15.6-8.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.00.91.20.91.10.91.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:Mining, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value25-5.016-5.09.0232.0
Percentage of ProfitLoss7.1-2.3-80.03.36.5-15.6-0.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.9-0.20.7-0.20.40.90.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:OtherProducts, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value-4.0-2.0-10.0-6.0-9.0-15.0
Percentage of ProfitLoss-1.1-0.950.04.0-6.510.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.1-0.1-0.4-0.3-0.4-0.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.0

us-gaap:ProfitLoss us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:MaadenJointVenture, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value10245-38.0-75.0-13.0-27.0-57.0
Percentage of ProfitLoss29.120.5190.050.0-9.418.419.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.61.6-1.6-3.5-0.5-1.1-2.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value414421294759-52.074109141169196155124140566383-4.02043-5.0-64.061
Percentage of ProfitLoss11.720.1123.5-145.0-31.342.414.6-50.3-37.2-243.179.7126.567.445.3-250.033.145.726.93.1142.9-358.32.37.2-96.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.41.50.91.22.22.5-2.12.94.05.25.15.84.34.04.41.92.23.1-0.20.92.1-0.3-2.62.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value309175-4.0-49.0-197.080-303.0-221.0-402.0-199.043-41.075150-196.011375225
Percentage of ProfitLoss88.379.9-23.5245.0131.357.685.4150.3137.2343.120.3-26.532.654.7350.066.954.373.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.96.1-0.2-2.1-9.23.4-12.4-8.6-14.8-7.31.3-1.22.14.9-6.23.82.68.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Research And Development Expense

us-gaap:ResearchAndDevelopmentExpense

us-gaap:ResearchAndDevelopmentExpense


Research
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value6.07.09.06.05.07.06.07.07.07.07.07.09.08.09.08.08.07.07.08.07.0111514
Percentage of ResearchAndDevelopmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.20.40.30.20.30.20.30.30.30.20.20.30.30.30.30.30.30.30.30.30.60.60.5

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value283328702392236521482381243625672711271933443390357930903174296428592655253723292061189224512679
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService

aa:Alumina


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value684760620697600707717770862897113010981068913
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.126.525.929.527.929.729.430.031.833.033.832.429.829.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.126.525.929.527.929.729.430.031.833.033.832.429.829.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Alumina100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:Bauxite


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value3452685061596095635875637145
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.82.82.12.82.52.53.72.32.12.21.92.01.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.82.82.12.82.52.53.72.32.12.21.92.01.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Bauxite100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:Energy


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value49394126225265718569741157373
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.71.41.71.11.02.22.72.83.12.52.23.42.02.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.71.41.71.11.02.22.72.83.12.52.23.42.02.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:FlatRolledAluminum


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.0320288284271272287294327312467472516429
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.011.112.012.012.611.411.811.512.111.514.013.914.413.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.011.112.012.012.611.411.811.512.111.514.013.914.413.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:FlatRolledAluminum0.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:OtherProducts


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-46.0-28.0-5.0-3.0-8.0-6.0-2.0-4.0-8.0-11.0-13.0-16.0-20.0-17.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.6-1.0-0.2-0.1-0.4-0.3-0.1-0.2-0.3-0.4-0.4-0.5-0.6-0.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.6-1.0-0.2-0.1-0.4-0.3-0.1-0.2-0.3-0.4-0.4-0.5-0.6-0.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:PrimaryAluminum


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value21121727138013111202129713091341138213941611165818711647
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax74.560.257.755.456.054.553.752.251.051.348.248.952.353.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax74.560.257.755.456.054.553.752.251.051.348.248.952.353.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:PrimaryAluminum100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenue From Contract With Customer Including Assessed Tax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:OperatingSegments


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value335434162928292726802950299931723383335341354140432437793971353534123194-41.038452790259341834551
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax118.4119.0122.4123.8124.8123.9123.1123.6124.8123.3123.7122.1120.8122.3125.1119.3119.3120.3-1.6165.1135.4137.1170.7169.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments0.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, aa:Alumina


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value103111249341026892104310481140130913141699164516041368151711111133109599590292278810641274
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax30.732.931.935.133.335.434.935.938.739.241.139.737.136.238.231.433.234.3-2426.823.533.030.425.428.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax36.439.239.043.441.543.843.044.448.348.350.848.544.844.347.837.539.641.239.238.744.741.643.447.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Alumina0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:Aluminum


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value21052049169016091477160116401681176117382111220424172115214820991991181037519181599158610621134
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax62.860.057.755.055.154.354.753.052.151.851.153.255.956.054.159.458.456.7-9148.823.957.361.225.424.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax74.371.470.768.068.867.267.365.565.063.963.165.067.568.467.770.869.668.2147.939.477.683.843.342.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Aluminum0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:Bauxite


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value218243304292311306311351313301325291303296306325288289293285269219301331
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.57.110.410.011.610.410.411.19.39.07.97.07.07.87.79.28.49.0-714.67.49.68.47.27.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.78.512.712.314.512.912.813.711.511.19.78.68.59.69.611.010.110.911.512.213.111.612.312.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Bauxite0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Revenues

us-gaap:Revenues us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:Revenues

aa:Energy, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value60555147597264
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.11.92.22.22.52.82.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:Mining, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value197173195209218233187
Percentage of Revenues328.3314.5382.4444.7369.5323.6292.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.06.08.29.79.29.16.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:OtherProducts, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value96957285734725
Percentage of Revenues160.0172.7141.2180.9123.765.339.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.43.33.04.03.11.80.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:MaadenJointVenture, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value741682552507585607976
Percentage of Revenues1235.01240.01082.41078.7991.5843.11525.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax26.223.823.323.624.623.636.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

Selling General And Administrative Expense

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:SellingGeneralAndAdministrativeExpense


Selling
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value545255474460626668845958646770707272929290859295
Percentage of SellingGeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.91.82.32.02.02.52.52.62.53.11.81.71.82.22.22.42.52.73.64.04.44.53.83.5

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value144381493114860142501330013651146311467015349159561593816185165181709617447172541692917076167411730516413
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems

us-gaap:OperatingSegments


Assetsus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value120151232513813147981439414209
Percentage of Assets80.984.286.784.886.086.6
Percentage of Assets80.984.286.784.886.086.6
Percentage of Assets us-gaap:OperatingSegments100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value90201005898449231797678408745826084908873854489009410957910649913687308913904481794900
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets62.567.466.264.860.057.459.856.355.355.653.655.057.056.061.053.051.652.254.047.329.9

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value144381493114860142501330013651146311467015349159561593816185165181709617447172541692917076167411730516413
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value376932483311339537054275411245394895515753895216502453684523586259545876565469809442
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets26.121.822.323.827.931.328.130.931.932.333.832.230.431.425.934.035.234.433.840.357.5

Assets Current

us-gaap:AssetsCurrent

us-gaap:AssetsCurrent


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value420148914520405331793333353036433818411441344193428141494238380435833404318136222566
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets29.132.830.428.423.924.424.124.824.925.825.925.925.924.324.322.021.219.919.020.915.6

us-gaap:AssetsCurrent us-gaap:ProductOrService

aa:Energy


Assets
Period End2020-12-312019-12-31
Value119106
Percentage of AssetsCurrent2.63.0
Percentage of Assets0.80.7
Percentage of Assets aa:Energy0.00.0

aa:OtherProducts


Assets
Period End2020-12-312019-12-31
Value219181
Percentage of AssetsCurrent4.85.1
Percentage of Assets1.51.2
Percentage of Assets aa:OtherProducts0.00.0

us-gaap:AssetsCurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:HalcoMiningInc


Assets
Period End2020-12-312019-12-31
Value143191
Percentage of AssetsCurrent3.25.4
Percentage of Assets1.01.3
Percentage of Assets aa:HalcoMiningInc0.00.0

aa:MaadenJointVenture


Assets
Period End2020-12-312019-12-31
Value10991109
Percentage of AssetsCurrent24.331.4
Percentage of Assets7.47.6
Percentage of Assets aa:MaadenJointVenture0.00.0

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:CashAndCashEquivalentsAtCarryingValue


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-31
Value16522544160717369658298798418341017111310221089119613581119954804853241332359557521266213
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.417.010.812.27.36.16.05.75.46.47.06.36.67.07.86.55.64.75.11.40.00.03.40.00.00.0

us-gaap:CashAndCashEquivalentsAtCarryingValue us-gaap:ConsolidationItems

us-gaap:MaterialReconcilingItems


Cash
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value160787911131358853557
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0
Percentage of Assets10.86.07.07.85.13.4
Percentage of Assets us-gaap:MaterialReconcilingItems0.00.00.00.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value16552547161017399688328838448371020111610261095120313651127965822859557
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.517.110.812.27.36.16.05.85.56.47.06.36.67.07.86.55.74.85.13.4

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent

us-gaap:AccountsReceivableNetCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value64458747151640257054659668475883010171025814811840789708668530380
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.53.93.23.63.04.23.74.14.54.85.26.36.24.84.64.94.74.14.03.12.3

Inventory Net

us-gaap:InventoryNet

us-gaap:InventoryNet


Inventory
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value154714171398139814191509164416491767179916441666166816301453132312871294116011921172
Percentage of InventoryNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.79.59.49.810.711.111.211.211.511.310.310.310.19.58.37.77.67.66.96.97.1

Prepaid Expense And Other Assets Current

us-gaap:PrepaidExpenseAndOtherAssetsCurrent

us-gaap:PrepaidExpenseAndOtherAssetsCurrent


Prepaid
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value233238290297264277288245250285301255283270271217347424334269333
Percentage of PrepaidExpenseAndOtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.61.62.02.12.02.02.01.71.61.81.91.61.71.61.61.32.02.52.01.62.0

Assets Noncurrent

us-gaap:AssetsNoncurrent us-gaap:ProductOrService

us-gaap:AssetsNoncurrent

aa:Energy


Assets
Period End2020-12-312019-12-31
Value401509
Percentage of AssetsNoncurrent100.0100.0
Percentage of Assets2.73.5
Percentage of Assets aa:Energy0.00.0

aa:OtherProducts


Assets
Period End2020-12-312019-12-31
Value757761
Percentage of AssetsNoncurrent188.8149.5
Percentage of Assets5.15.2
Percentage of Assets aa:OtherProducts0.00.0

us-gaap:AssetsNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:HalcoMiningInc


Assets
Period End2020-12-312019-12-31
Value828923
Percentage of AssetsNoncurrent206.5181.3
Percentage of Assets5.66.3
Percentage of Assets aa:HalcoMiningInc0.00.0

aa:MaadenJointVenture


Assets
Period End2020-12-312019-12-31
Value76487931
Percentage of AssetsNoncurrent1907.21558.2
Percentage of Assets51.554.2
Percentage of Assets aa:MaadenJointVenture0.00.0

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross

us-gaap:PropertyPlantAndEquipmentGross


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value20551201992052221061208772018121715214562212622015218072183922079228379138232532297123076225502314522118
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets142.3135.3138.1147.8157.0147.8148.4146.3144.2138.0136.8134.9133.7133.652.4134.8135.7135.1134.7133.7134.8

us-gaap:PropertyPlantAndEquipmentGross us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:PropertyPlantAndEquipmentByType

us-gaap:OperatingSegments, aa:AluminaRefining, us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value418039563604400937733717
Percentage of PropertyPlantAndEquipmentGross20.418.216.543.916.716.8
Percentage of Assets28.127.022.623.022.522.6
Percentage of Assets us-gaap:OperatingSegments aa:AluminaRefining us-gaap:MachineryAndEquipment0.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:AluminaRefining, us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value247424152478266425002405
Percentage of PropertyPlantAndEquipmentGross12.111.111.429.211.110.9
Percentage of Assets16.616.515.515.314.914.7
Percentage of Assets us-gaap:OperatingSegments aa:AluminaRefining us-gaap:ManufacturingFacility0.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:AluminumSmeltingAndCasting, us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value61116251648968276655
Percentage of PropertyPlantAndEquipmentGross29.828.829.874.729.5
Percentage of Assets41.142.740.739.139.8
Percentage of Assets us-gaap:OperatingSegments aa:AluminumSmeltingAndCasting us-gaap:MachineryAndEquipment0.00.00.00.00.0

us-gaap:OperatingSegments, aa:AluminumSmeltingAndCasting, us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value34473457353235753544
Percentage of PropertyPlantAndEquipmentGross16.815.916.239.115.7
Percentage of Assets23.223.622.220.521.2
Percentage of Assets us-gaap:OperatingSegments aa:AluminumSmeltingAndCasting us-gaap:ManufacturingFacility0.00.00.00.00.0

us-gaap:OperatingSegments, aa:BauxiteMining, us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value517499480508465401
Percentage of PropertyPlantAndEquipmentGross2.52.32.25.62.11.8
Percentage of Assets3.53.43.02.92.82.4
Percentage of Assets us-gaap:OperatingSegments aa:BauxiteMining us-gaap:MachineryAndEquipment0.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:BauxiteMining, us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value11191138111912501194986
Percentage of PropertyPlantAndEquipmentGross5.55.25.113.75.34.5
Percentage of Assets7.57.87.07.27.16.0
Percentage of Assets us-gaap:OperatingSegments aa:BauxiteMining us-gaap:ManufacturingFacility0.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:Energy, us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value8448798899051080980
Percentage of PropertyPlantAndEquipmentGross4.14.04.19.94.84.4
Percentage of Assets5.76.05.65.26.56.0
Percentage of Assets us-gaap:OperatingSegments aa:Energy us-gaap:MachineryAndEquipment0.00.00.00.00.00.0

us-gaap:OperatingSegments, aa:Energy, us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value360440506552610530
Percentage of PropertyPlantAndEquipmentGross1.82.02.36.02.72.4
Percentage of Assets2.43.03.23.23.63.2
Percentage of Assets us-gaap:OperatingSegments aa:Energy us-gaap:ManufacturingFacility0.00.00.00.00.00.0

us-gaap:PropertyPlantAndEquipmentGross us-gaap:ConsolidationItems, us-gaap:PropertyPlantAndEquipmentByType

us-gaap:MaterialReconcilingItems, us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value465293282288309306
Percentage of PropertyPlantAndEquipmentGross2.31.31.33.21.41.4
Percentage of Assets3.12.01.81.71.81.9
Percentage of Assets us-gaap:MaterialReconcilingItems us-gaap:MachineryAndEquipment0.00.00.00.00.00.0

us-gaap:MaterialReconcilingItems, us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value350386380417405328
Percentage of PropertyPlantAndEquipmentGross1.71.81.74.61.81.5
Percentage of Assets2.42.62.42.42.42.0
Percentage of Assets us-gaap:MaterialReconcilingItems us-gaap:ManufacturingFacility0.00.00.00.00.00.0

us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType

aa:PropertyPlantAndEquipmentOtherThanConstructionInProgress


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value201872139421401226592205221634
Percentage of PropertyPlantAndEquipmentGross98.498.598.1248.097.897.8
Percentage of Assets135.8146.2134.3129.9131.7131.8
Percentage of Assets aa:PropertyPlantAndEquipmentOtherThanConstructionInProgress0.00.00.00.00.00.0

us-gaap:Land


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value320333328346346333
Percentage of PropertyPlantAndEquipmentGross1.61.51.53.81.51.5
Percentage of Assets2.22.32.12.02.12.0
Percentage of Assets us-gaap:Land0.00.00.00.00.00.0

us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value121171293512773135571316613191
Percentage of PropertyPlantAndEquipmentGross59.059.658.6148.458.459.6
Percentage of Assets81.588.480.177.778.680.4
Percentage of Assets us-gaap:MachineryAndEquipment0.00.00.00.00.00.0

us-gaap:ManufacturingFacility


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value775081268300875685408110
Percentage of PropertyPlantAndEquipmentGross37.837.438.195.837.936.7
Percentage of Assets52.255.552.150.251.049.4
Percentage of Assets us-gaap:ManufacturingFacility0.00.00.00.00.00.0

Construction In Progress Gross

us-gaap:ConstructionInProgressGross

us-gaap:ConstructionInProgressGross


Construction
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value335321406387498484
Percentage of ConstructionInProgressGross100.0100.0100.0100.0100.0100.0
Percentage of Assets2.32.22.52.23.02.9

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value135751326913332138111358813021137991352713853136871348013484135231380313908139711373413642132251353612728
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets94.088.989.796.9102.295.494.392.290.385.884.683.381.980.779.781.081.179.979.078.277.5

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value697669307190725072897160791679298273832883278355855690349138928292379434932596099390
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets48.346.448.450.954.852.554.154.053.952.252.251.651.852.852.453.854.655.255.755.557.2

us-gaap:PropertyPlantAndEquipmentNet us-gaap:ConsolidationItems

us-gaap:MaterialReconcilingItems


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value453519520520585454
Percentage of PropertyPlantAndEquipmentNet6.36.66.25.76.34.8
Percentage of Assets3.03.53.33.03.52.8
Percentage of Assets us-gaap:MaterialReconcilingItems0.00.00.00.00.00.0

us-gaap:PropertyPlantAndEquipmentNet us-gaap:StatementGeographical

aa:OtherGeographicalRegions


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value5.04.015141517
Percentage of PropertyPlantAndEquipmentNet0.10.10.20.20.20.2
Percentage of Assets0.00.00.10.10.10.1
Percentage of Assets aa:OtherGeographicalRegions0.00.00.00.00.00.0

country:AU


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value228220442002222020532158
Percentage of PropertyPlantAndEquipmentNet31.725.824.024.322.023.0
Percentage of Assets15.414.012.612.712.313.1
Percentage of Assets country:AU0.00.00.00.00.00.0

country:BR


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value121515961729211122281922
Percentage of PropertyPlantAndEquipmentNet16.920.220.823.123.920.5
Percentage of Assets8.210.910.812.113.311.7
Percentage of Assets country:BR0.00.00.00.00.00.0

country:CA


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value100210471064111611611177
Percentage of PropertyPlantAndEquipmentNet13.913.212.812.212.512.5
Percentage of Assets6.77.26.76.46.97.2
Percentage of Assets country:CA0.00.00.00.00.00.0

country:ES


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value218209321316273293
Percentage of PropertyPlantAndEquipmentNet3.02.63.93.52.93.1
Percentage of Assets1.51.42.01.81.61.8
Percentage of Assets country:ES0.00.00.00.00.00.0

country:IS


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value110211601216127613411397
Percentage of PropertyPlantAndEquipmentNet15.314.714.614.014.414.9
Percentage of Assets7.47.97.67.38.08.5
Percentage of Assets country:IS0.00.00.00.00.00.0

country:NO


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value357365381427438463
Percentage of PropertyPlantAndEquipmentNet5.04.64.64.74.74.9
Percentage of Assets2.42.52.42.42.62.8
Percentage of Assets country:NO0.00.00.00.00.00.0

country:US


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value100914911599165818161963
Percentage of PropertyPlantAndEquipmentNet14.018.819.218.119.520.9
Percentage of Assets6.810.210.09.510.812.0
Percentage of Assets country:US0.00.00.00.00.00.0

Investments In Affiliates Subsidiaries Associates And Joint Ventures

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures


Investments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value1113105510511034103710591113111411411362136013811390141314101408137813931358
Percentage of InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.77.17.17.37.87.87.67.67.48.58.58.58.48.38.18.28.18.28.1

Goodwill

us-gaap:Goodwill

us-gaap:Goodwill


Goodwill
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312016-09-302015-12-312014-12-31
Value145150989989155155152160
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.01.06.25.70.90.90.90.0

us-gaap:Goodwill dei:LegalEntity, us-gaap:StatementBusinessSegments

aa:AlcoaCorporation, aa:Alumina


Goodwilldei:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value96100100103103
Percentage of Goodwill66.266.710.110.466.5
Percentage of Assets0.60.70.60.60.6
Percentage of Assets aa:AlcoaCorporation aa:Alumina0.00.00.00.00.0

aa:AlcoaCorporation, aa:Bauxite


Goodwilldei:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value4950515152
Percentage of Goodwill33.833.35.25.233.5
Percentage of Assets0.30.30.30.30.3
Percentage of Assets aa:AlcoaCorporation aa:Bauxite0.00.00.00.00.0

us-gaap:Goodwill us-gaap:BalanceSheetLocation

us-gaap:OtherNoncurrentAssets


Goodwillus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value145150151154155
Percentage of Goodwill100.0100.015.315.6100.0
Percentage of Assets1.01.00.90.90.9
Percentage of Assets us-gaap:OtherNoncurrentAssets0.00.00.00.00.0

us-gaap:Goodwill us-gaap:BalanceSheetLocation, us-gaap:StatementBusinessSegments

us-gaap:OtherNoncurrentAssets, aa:Alumina


Goodwillus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value2.03.03.04.04.0
Percentage of Goodwill1.42.00.30.42.6
Percentage of Assets0.00.00.00.00.0
Percentage of Assets us-gaap:OtherNoncurrentAssets aa:Alumina0.00.00.00.00.0

us-gaap:OtherNoncurrentAssets, us-gaap:Corporate


Goodwillus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value141145146148149
Percentage of Goodwill97.296.714.815.096.1
Percentage of Assets0.91.00.90.80.9
Percentage of Assets us-gaap:OtherNoncurrentAssets us-gaap:Corporate0.00.00.00.00.0

us-gaap:Goodwill us-gaap:ConsolidationItems

us-gaap:MaterialReconcilingItems


Goodwillus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value141145146148149147
Percentage of Goodwill97.296.714.815.096.196.7
Percentage of Assets0.91.00.90.80.90.9
Percentage of Assets us-gaap:MaterialReconcilingItems0.00.00.00.00.00.0

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet

us-gaap:FiniteLivedIntangibleAssetsNet


Finite
Period End2020-12-312019-12-312018-12-312017-12-31
Value45525762
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0
Percentage of Assets0.30.40.40.4

us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass

aa:PatentLicenseAgreement


Finite
Period End2020-12-312019-12-312018-12-312017-12-31
Value17171819
Percentage of FiniteLivedIntangibleAssetsNet37.832.731.630.6
Percentage of Assets0.10.10.10.1
Percentage of Assets aa:PatentLicenseAgreement0.00.00.00.0

us-gaap:ComputerSoftwareIntangibleAsset


Finite
Period End2020-12-312019-12-312018-12-312017-12-31
Value18242629
Percentage of FiniteLivedIntangibleAssetsNet40.046.245.646.8
Percentage of Assets0.10.20.20.2
Percentage of Assets us-gaap:ComputerSoftwareIntangibleAsset0.00.00.00.0

us-gaap:OtherIntangibleAssets


Finite
Period End2020-12-312019-12-312018-12-312017-12-31
Value10.0111314
Percentage of FiniteLivedIntangibleAssetsNet22.221.222.822.6
Percentage of Assets0.10.10.10.1
Percentage of Assets us-gaap:OtherIntangibleAssets0.00.00.00.0

Deferred Tax Assets Liabilities Net

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:DeferredTaxAssetsLiabilitiesNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312017-09-302017-06-302016-12-31
Value451410301517562436449
Percentage of DeferredTaxAssetsLiabilitiesNet100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.02.81.93.03.32.62.7

us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity, us-gaap:IncomeTaxAuthority

aa:AlcoaAluminio, us-gaap:ForeignCountry


Deferred
Period End2020-12-31
Value166
Percentage of DeferredTaxAssetsLiabilitiesNet36.8
Percentage of Assets1.1
Percentage of Assets aa:AlcoaAluminio us-gaap:ForeignCountry0.0

aa:AlcoaCanadaCompany, us-gaap:ForeignCountry


Deferred
Period End2020-12-31
Value148
Percentage of DeferredTaxAssetsLiabilitiesNet32.8
Percentage of Assets1.0
Percentage of Assets aa:AlcoaCanadaCompany us-gaap:ForeignCountry0.0

aa:AlcoaLauralcoManagementCompany, us-gaap:ForeignCountry


Deferred
Period End2020-12-31
Value38
Percentage of DeferredTaxAssetsLiabilitiesNet8.4
Percentage of Assets0.3
Percentage of Assets aa:AlcoaLauralcoManagementCompany us-gaap:ForeignCountry0.0

aa:AlcoaWolinbecCompany, us-gaap:ForeignCountry


Deferred
Period End2020-12-31
Value38
Percentage of DeferredTaxAssetsLiabilitiesNet8.4
Percentage of Assets0.3
Percentage of Assets aa:AlcoaWolinbecCompany us-gaap:ForeignCountry0.0

aa:AlcoaWorldAluminaBrasil, us-gaap:ForeignCountry


Deferred
Period End2020-12-31
Value80
Percentage of DeferredTaxAssetsLiabilitiesNet17.7
Percentage of Assets0.5
Percentage of Assets aa:AlcoaWorldAluminaBrasil us-gaap:ForeignCountry0.0

us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:ConsolidationItems

us-gaap:MaterialReconcilingItems


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value655642563814741589
Percentage of DeferredTaxAssetsLiabilitiesNet145.2156.6187.0157.4165.00.0
Percentage of Assets4.44.43.54.74.43.6
Percentage of Assets us-gaap:MaterialReconcilingItems0.00.00.00.00.00.0

us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:IncomeTaxAuthority

us-gaap:DomesticCountry


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value7.07.010.06.017
Percentage of DeferredTaxAssetsLiabilitiesNet1.61.73.31.23.8
Percentage of Assets0.00.00.10.00.1
Percentage of Assets us-gaap:DomesticCountry0.00.00.00.00.0

us-gaap:ForeignCountry


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312017-06-302016-12-31
Value444403291511432432
Percentage of DeferredTaxAssetsLiabilitiesNet98.498.396.798.899.196.2
Percentage of Assets3.02.81.82.92.62.6
Percentage of Assets us-gaap:ForeignCountry0.00.00.00.00.00.0

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OperatingLeaseRightOfUseAsset


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312019-01-01
Value122131137147141141154158175185201
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.80.90.91.01.11.01.11.11.11.20.0

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent

us-gaap:OtherAssetsNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value141614021444137213081228141213771463148014751615163517011719174516881674166815341247
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.89.49.79.69.89.09.79.49.59.39.310.09.99.99.910.110.09.810.08.97.6

Other Assets

us-gaap:OtherAssets us-gaap:ConsolidationItems

us-gaap:OtherAssets

us-gaap:MaterialReconcilingItems


Other
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value182291361380348260
Percentage of OtherAssets100.0100.0100.0100.0100.0100.0
Percentage of Assets1.22.02.32.22.11.6
Percentage of Assets us-gaap:MaterialReconcilingItems0.00.00.00.00.00.0

Accounts Payable Current

us-gaap:AccountsPayableCurrent

us-gaap:AccountsPayableCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value139212841403136012531276148414181523150316631711175218131898161815081434145512521379
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.68.69.49.59.49.310.19.79.99.410.410.610.610.610.99.48.98.48.77.28.4

Liabilities Current

us-gaap:LiabilitiesCurrent

us-gaap:LiabilitiesCurrent


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value267132212761230322412223256324552531280329193004301329763252276626082623282122062404
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets18.521.618.616.216.816.317.516.716.517.618.318.618.217.418.616.015.415.416.912.714.6

us-gaap:LiabilitiesCurrent us-gaap:ProductOrService

aa:Energy


Liabilities
Period End2020-12-312019-12-31
Value2741
Percentage of LiabilitiesCurrent1.01.6
Percentage of Assets0.20.3
Percentage of Assets aa:Energy0.00.0

aa:OtherProducts


Liabilities
Period End2020-12-312019-12-31
Value6659
Percentage of LiabilitiesCurrent2.42.3
Percentage of Assets0.40.4
Percentage of Assets aa:OtherProducts0.00.0

us-gaap:LiabilitiesCurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:HalcoMiningInc


Liabilities
Period End2020-12-312019-12-31
Value206156
Percentage of LiabilitiesCurrent7.56.1
Percentage of Assets1.41.1
Percentage of Assets aa:HalcoMiningInc0.00.0

aa:MaadenJointVenture


Liabilities
Period End2020-12-312019-12-31
Value794677
Percentage of LiabilitiesCurrent28.826.4
Percentage of Assets5.34.6
Percentage of Assets aa:MaadenJointVenture0.00.0

Long Term Debt Current

us-gaap:LongTermDebtCurrent

us-gaap:LongTermDebtCurrent


Long
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value2.01.01.0162118
Percentage of LongTermDebtCurrent100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.10.10.1

Operating Lease Liability Current

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OperatingLeaseLiabilityCurrent


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value49546060585661
Percentage of OperatingLeaseLiabilityCurrent100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.40.40.40.40.40.4

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent

us-gaap:OtherLiabilitiesCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value538554525415451435494484427437347319353294412376492568742390558
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.73.73.52.93.43.23.43.32.82.72.22.02.11.72.42.22.93.34.42.33.4

Taxes Payable Current

us-gaap:TaxesPayableCurrent

us-gaap:TaxesPayableCurrent


Taxes
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value126929157967810481100395426417323325282166144176147110136
Percentage of TaxesPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.60.60.40.70.60.70.60.72.52.72.62.01.91.61.00.91.00.90.60.8

Liabilities Noncurrent

us-gaap:LiabilitiesNoncurrent us-gaap:ProductOrService

us-gaap:LiabilitiesNoncurrent

aa:Energy


Liabilities
Period End2020-12-312019-12-31
Value11387
Percentage of LiabilitiesNoncurrent100.0100.0
Percentage of Assets0.80.6
Percentage of Assets aa:Energy0.00.0

aa:OtherProducts


Liabilities
Period End2020-12-312019-12-31
Value6242
Percentage of LiabilitiesNoncurrent54.948.3
Percentage of Assets0.40.3
Percentage of Assets aa:OtherProducts0.00.0

us-gaap:LiabilitiesNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:HalcoMiningInc


Liabilities
Period End2020-12-312019-12-31
Value331511
Percentage of LiabilitiesNoncurrent292.9587.4
Percentage of Assets2.23.5
Percentage of Assets aa:HalcoMiningInc0.00.0

aa:MaadenJointVenture


Liabilities
Period End2020-12-312019-12-31
Value53475587
Percentage of LiabilitiesNoncurrent4731.96421.8
Percentage of Assets36.038.2
Percentage of Assets aa:MaadenJointVenture0.00.0

Long Term Debt

us-gaap:LongTermDebt

us-gaap:LongTermDebt


Long
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value24651800180214041445225
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0
Percentage of Assets16.612.311.38.08.61.4

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent

us-gaap:LongTermDebtNoncurrent


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312015-12-31
Value246317991802180113881424207
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets16.612.311.311.38.08.51.3

Long Term Debt And Capital Lease Obligations

us-gaap:LongTermDebtAndCapitalLeaseObligations

us-gaap:LongTermDebtAndCapitalLeaseObligations


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value2216221424632538180018011799180518041801182019161445138813841418143114241457207
Percentage of LongTermDebtAndCapitalLeaseObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets15.314.816.617.813.513.212.312.311.811.311.211.68.58.08.08.48.48.58.41.3

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Pension
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value74474986811001166
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0100.0
Percentage of Assets5.05.15.46.37.0
Percentage of Assets us-gaap:OtherPostretirementBenefitPlansDefinedBenefit0.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit


Pension
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value14921505140723411851
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent200.5200.9162.1212.8158.7
Percentage of Assets10.010.38.813.411.1
Percentage of Assets us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.0

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value164916251705162416191536177418711964192620052069208421492275225622452287204321462071
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.410.911.511.412.211.312.112.812.812.112.612.812.612.613.013.113.313.412.212.412.6

Operating Lease Liability Noncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value768082929090100
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.50.50.60.60.70.70.7

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo


Lessee
Period End2021-06-302021-03-312020-12-312020-09-30
Value24233332
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo100.0100.0100.0100.0
Percentage of Assets0.20.20.20.2

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree


Lessee
Period End2021-06-302021-03-312020-12-312020-09-30
Value15142120
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree100.0100.0100.0100.0
Percentage of Assets0.10.10.10.1

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour


Lessee
Period End2021-06-302021-03-312020-12-312020-09-30
Value9.09.01313
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour100.0100.0100.0100.0
Percentage of Assets0.10.10.10.1

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive


Lessee
Period End2020-12-31
Value8000000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive100.0
Percentage of Assets0.1

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive


Lessee
Period End2020-12-31
Value22
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive100.0
Percentage of Assets0.1

Operating Lease Liability

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiability


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312019-01-01
Value125134142152148146161158175185201
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.91.01.11.11.11.11.11.11.20.0

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue


Lessee
Period End2021-06-302021-03-312020-12-312020-09-30
Value142152165175
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue100.0100.0100.0100.0
Percentage of Assets1.01.01.11.2

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2021-06-302021-03-312020-12-312020-09-30
Value17182323
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0100.0100.0100.0
Percentage of Assets0.10.10.20.2

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value376932483311339537054275411245394895515753895216502453684523586259545876565469809442
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets26.121.822.323.827.931.328.130.931.932.333.832.230.431.425.934.035.234.433.840.357.5

Stockholders Equity Including Portion Attributable To Noncontrolling Interest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value5418487350165019532458115886641068597083739472857108751767988118819981637697912611861118131151311787125761307314789
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets37.532.633.835.240.042.640.243.744.744.446.445.043.044.039.047.048.447.846.052.70.00.070.10.00.00.00.0

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value-5687.0-5878.0-5629.0-5547.0-5280.0-4898.0-4974.0-4849.0-4705.0-4834.0-4565.0-4740.0-4967.0-4530.0-5182.0-4033.0-3803.0-3800.0-3775.0-4478.0-1456.0-1457.0-1600.0-2000.0-1498.0-1316.0-657.0
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-105.0-120.6-112.2-110.5-99.2-84.3-84.5-75.6-68.6-68.2-61.7-65.1-69.9-60.3-76.2-49.7-46.4-46.6-49.0-49.1-12.3-12.3-13.9-17.0-11.9-10.1-4.4
Percentage of Assets-39.4-39.4-37.9-38.9-39.7-35.9-34.0-33.1-30.7-30.3-28.6-29.3-30.1-26.5-29.7-23.4-22.5-22.3-22.5-25.90.00.0-9.70.00.00.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value9695967496639661965596479639963896299618961196569650963395909584955995539531
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest178.9198.5192.6192.5181.3166.0163.8150.4140.4135.8130.0132.5135.8128.1141.1118.1116.6117.0123.8
Percentage of Assets67.164.865.067.872.670.765.965.762.760.360.359.758.456.355.055.556.555.956.9
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value164916251705162416191536177418711964192620052069208421492275225622452287204321462180212220712084231124742896
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest30.433.334.032.430.426.430.129.228.627.227.128.429.328.633.527.827.428.026.523.518.418.018.017.718.418.919.6
Percentage of Assets11.410.911.511.412.211.312.112.812.812.112.612.812.612.613.013.113.313.412.212.40.00.012.60.00.00.00.0
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value-241.0-550.0-725.0-721.0-672.0-476.0-555.0-252.0-31.0371341298339263113309196121-104.0
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-4.4-11.3-14.5-14.4-12.6-8.2-9.4-3.9-0.55.24.64.14.83.51.73.82.41.5-1.4
Percentage of Assets-1.7-3.7-4.9-5.1-5.1-3.5-3.8-1.7-0.22.32.11.82.11.50.61.81.20.7-0.6
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Additional Paid In Capital Common Stock

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:AdditionalPaidInCapitalCommonStock


Additional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value9695967496639661965596479639963896299618961196569650963395909584955995539531
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets67.164.865.067.872.670.765.965.762.760.360.359.758.456.355.055.556.555.956.9

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value-241.0-550.0-725.0-721.0-672.0-476.0-555.0-252.0-31.0371341298339263113309196121-104.0
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-1.7-3.7-4.9-5.1-5.1-3.5-3.8-1.7-0.22.32.11.82.11.50.61.81.20.7-0.6

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value-5687000000.0-5878000000.0-5629000000.0-5547000000.0-5280000000.0-4898000000.0-4974000000.0-4849000000.0-4705000000.0-4834000000.0-4565000000.0-4740000000.0-4967000000.0-4530000000.0-5182000000.0-4033000000.0-3803000000.0-3800000000.0-3775000000.0-4478000000.0-1600000000.0
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-39.4-39.4-37.9-38.9-39.7-35.9-34.0-33.1-30.7-30.3-28.6-29.3-30.1-26.5-29.7-23.4-22.5-22.3-22.5-25.9-9.7

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value-915000000.0-974000000.0-912000000.0-1026000000.0-1040000000.0-1135000000.0-870000000.0-899000000.0-815000000.0-816000000.0-825000000.0-814000000.0-769000000.0-610000000.0-577000000.0
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax16.116.616.218.519.723.217.518.517.316.918.117.215.513.511.1
Percentage of Assets-6.3-6.5-6.1-7.2-7.8-8.3-5.9-6.1-5.3-5.1-5.2-5.0-4.7-3.6-3.3
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value-5687000000.0-5878000000.0-5629000000.0-5547000000.0-5280000000.0-4898000000.0-4974000000.0-4849000000.0-4705000000.0-4834000000.0-4565000000.0-4740000000.0-4967000000.0-4530000000.0-5182000000.0
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-39.4-39.4-37.9-38.9-39.7-35.9-34.0-33.1-30.7-30.3-28.6-29.3-30.1-26.5-29.7
Percentage of Assets us-gaap:Parent0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value164916251705162416191536177418711964192620052069208421492275225622452287204321462071
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.410.911.511.412.211.312.112.812.812.112.612.812.612.613.013.113.313.412.212.412.6

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10.08.01.07.09.08.01.08.01110.06.09.010.010.03.07.07.07.0
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10.08.01.07.09.08.01.08.01110.06.09.010.010.03.07.07.07.0
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Minority Interest Decrease From Distributions To Noncontrolling Interest Holders

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value7562554675318410272214261181118267988998575792345035
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value7562554675318410272214261181118267988998575792345035
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-03-312015-12-31
Value-86.06.038158288-90.026217482168535288-430.05545538431174239-359.053
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-3.00.21.66.713.4-3.810.86.83.06.216.08.5-12.01.814.313.010.92.89.4-19.02.2

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value34514-117.0-78.0-79.0107-134.0-76.0-199.0-59.0-148.0-83.0-100.0-74.0-170.0-104.0
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.217.9-4.9-3.3-3.74.5-5.5-3.0-7.3-2.2-4.4-2.4-2.8-2.4-5.4-3.5

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-849.0428-63.0692-71.0-44.0-93.0-81.0-71.0-199.0-294.0-280.0433-147.0-53.0-115.0
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-30.014.9-2.629.3-3.3-1.8-3.8-3.2-2.6-7.3-8.8-8.312.1-4.8-1.7-3.9

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-892.0937-129.0771136-51.0397.0-183.0-96.090-69.0-108.0-162.0238162143-37.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-31.532.6-5.432.66.3-2.11.60.3-6.8-3.52.7-2.0-3.0-5.27.55.55.0-1.4

Deferred Income Tax Expense Benefit

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DeferredIncomeTaxExpenseBenefit


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value3018-14.0-6.0-29.023-44.0-5.03133-20.015-20.0-11.0112142723-52.034103
Percentage of DeferredIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization

us-gaap:DepreciationDepletionAndAmortization


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value161182170161152170183184174172174173192194187194190179182181178177186190
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Inventories

us-gaap:IncreaseDecreaseInInventories

us-gaap:IncreaseDecreaseInInventories


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value1166899-37.0-143.0-41.0-26.0-58.0-36.0-17.0-1.0129816913616-16.01022417-34.0-8.0-120.0
Percentage of IncreaseDecreaseInInventories100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-03-312015-12-31
Value-86.06.038158288-90.026217482168535288-430.05545538431174239-359.053
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-3.00.21.66.713.4-3.810.86.83.06.216.08.5-12.01.814.313.010.92.89.4-19.02.2

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value309175-4.0-49.0-197.080-303.0-221.0-402.0-199.043-41.075150-196.011375225-125.0-6.0-55.0-210.0-826.0-124.0
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.96.1-0.2-2.1-9.23.4-12.4-8.6-14.8-7.31.3-1.22.14.9-6.23.82.68.5-4.9-0.3-2.7-11.1-33.7-4.6

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value35021917-20.0-150.0139-355.0-147.0-293.0-58.0212155230274-56.0169138308-129.014-12.0-215.0-890.0-63.0
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax12.47.60.7-0.8-7.05.8-14.6-5.7-10.8-2.16.34.66.48.9-1.85.74.811.6-5.10.6-0.6-11.4-36.3-2.4

us-gaap:ProfitLoss us-gaap:ProductOrService, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:Energy, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value27252820272326
Percentage of ProfitLoss7.711.4-140.0-13.319.4-15.6-8.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.00.91.20.91.10.91.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:Mining, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value25-5.016-5.09.0232.0
Percentage of ProfitLoss7.1-2.3-80.03.36.5-15.6-0.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.9-0.20.7-0.20.40.90.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

aa:OtherProducts, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value-4.0-2.0-10.0-6.0-9.0-15.0
Percentage of ProfitLoss-1.1-0.950.04.0-6.510.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.1-0.1-0.4-0.3-0.4-0.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.0

us-gaap:ProfitLoss us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

aa:MaadenJointVenture, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value10245-38.0-75.0-13.0-27.0-57.0
Percentage of ProfitLoss29.120.5190.050.0-9.418.419.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.61.6-1.6-3.5-0.5-1.1-2.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.00.00.00.0

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value414421294759-52.074109141169196155124140566383-4.02043-5.0-64.061
Percentage of ProfitLoss11.720.1123.5-145.0-31.342.414.6-50.3-37.2-243.179.7126.567.445.3-250.033.145.726.93.1142.9-358.32.37.2-96.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.41.50.91.22.22.5-2.12.94.05.25.15.84.34.04.41.92.23.1-0.20.92.1-0.3-2.62.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value309175-4.0-49.0-197.080-303.0-221.0-402.0-199.043-41.075150-196.011375225
Percentage of ProfitLoss88.379.9-23.5245.0131.357.685.4150.3137.2343.120.3-26.532.654.7350.066.954.373.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.96.1-0.2-2.1-9.23.4-12.4-8.6-14.8-7.31.3-1.22.14.9-6.23.82.68.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Share Based Compensation

us-gaap:ShareBasedCompensation

us-gaap:ShareBasedCompensation


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value10.08.01.07.09.08.01.08.01110.06.09.010.010.03.07.07.07.04.06.010.08.04.0
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value34514-117.0-78.0-79.0107-134.0-76.0-199.0-59.0-148.0-83.0-100.0-74.0-170.0-104.0
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.217.9-4.9-3.3-3.74.5-5.5-3.0-7.3-2.2-4.4-2.4-2.8-2.4-5.4-3.5

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value7975111747791134878969148829574150968871146868686133
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Payments To Acquire Investments

us-gaap:PaymentsToAcquireInvestments

us-gaap:PaymentsToAcquireInvestments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value1.02.06.03.02.01.00.01.01101.01.01.0228.011250.00.00.03.027
Percentage of PaymentsToAcquireInvestments100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value-849.0428-63.0692-71.0-44.0-93.0-81.0-71.0-199.0-294.0-280.0433-147.0-53.0-115.0
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-30.014.9-2.629.3-3.3-1.8-3.8-3.2-2.6-7.3-8.8-8.312.1-4.8-1.7-3.9

Proceeds From Issuance Of Long Term Debt

us-gaap:ProceedsFromIssuanceOfLongTermDebt dei:LegalEntity, us-gaap:DebtInstrument

us-gaap:ProceedsFromIssuanceOfLongTermDebt

aa:AlcoaNederlandHoldingBV, aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven


Proceeds
Period End2020-07-31
Value736
Percentage of ProceedsFromIssuanceOfLongTermDebt100.0

aa:AlcoaNederlandHoldingBV, aa:FourPointOneTwoFivePercentageSeniorNotesDueTwoThousandAndTwentyNine


Proceeds
Period End2021-03-31
Value493
Percentage of ProceedsFromIssuanceOfLongTermDebt0.0

Debt Instrument Interest Rate Stated Percentage

us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:CreditFacility, us-gaap:DebtInstrument

us-gaap:DebtInstrumentInterestRateStatedPercentage

us-gaap:RevolvingCreditFacility, aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven


Debt
Period End2021-03-31
Value5.5
Percentage of DebtInstrumentInterestRateStatedPercentage100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations us-gaap:RevolvingCreditFacility aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven0.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice us-gaap:OptionIndexedToIssuersEquityType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:EmployeeStockOption


Share
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312016-10-31
Value26.8528.3828.4125.4824.6924.42
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet

us-gaap:DeferredTaxAssetsNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value10411010872118513331615
Percentage of DeferredTaxAssetsNet100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsNet us-gaap:ValuationAllowancesAndReservesType

aa:ExpiresWithinElevenToTwentyYears


Deferred
Period End2020-12-312019-12-312017-12-312016-12-31
Value32149889
Percentage of DeferredTaxAssetsNet3.11.48.36.7

aa:NoExpiration


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value401625605587701
Percentage of DeferredTaxAssetsNet38.561.969.449.552.6

aa:OtherDeferredTaxAssets


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value608371267500510
Percentage of DeferredTaxAssetsNet58.436.730.642.238.3

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits

us-gaap:UnrecognizedTaxBenefits


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value4.0293010.022222552
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance

us-gaap:DeferredTaxAssetsValuationAllowance


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value21271778168419271755712486517
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsValuationAllowance us-gaap:IncomeTaxAuthority

us-gaap:DomesticCountry


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value118589877910501057
Percentage of DeferredTaxAssetsValuationAllowance55.750.546.354.560.2

us-gaap:ForeignCountry


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value942880905877698
Percentage of DeferredTaxAssetsValuationAllowance44.349.553.745.539.8

us-gaap:DeferredTaxAssetsValuationAllowance us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:ElysisLimitedPartnership


Deferred
Period End2020-12-312018-12-31
Value5886
Percentage of DeferredTaxAssetsValuationAllowance2.75.1

us-gaap:DeferredTaxAssetsValuationAllowance us-gaap:ValuationAllowancesAndReservesType

aa:ExpiresWithinElevenToTwentyYears


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value35931826315288
Percentage of DeferredTaxAssetsValuationAllowance16.917.915.67.95.0

aa:ExpiresWithinTenYears


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value301350325523272
Percentage of DeferredTaxAssetsValuationAllowance14.219.719.327.115.5

aa:NoExpiration


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value822300370315265
Percentage of DeferredTaxAssetsValuationAllowance38.616.922.016.315.1

aa:OtherDeferredTaxAssets


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value6458107269371130
Percentage of DeferredTaxAssetsValuationAllowance30.345.643.148.664.4

aa:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLossAndOther

aa:AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLossAndOther


Accrual
Period End2021-03-312020-12-312019-03-31
Value-3.05.0-1.0
Percentage of AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLossAndOther100.0100.0100.0

aa:AccruedOtherPostretirementBenefitAdditionToRemeasurement us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

aa:AccruedOtherPostretirementBenefitAdditionToRemeasurement

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Accrued
Period End2021-06-302021-03-31
Value-6.072
Percentage of AccruedOtherPostretirementBenefitAdditionToRemeasurement100.0100.0

aa:AdditionsToLongTermDebtIssuedLessIssuanceDiscount

aa:AdditionsToLongTermDebtIssuedLessIssuanceDiscount


Additions
Period End2021-06-302021-03-312020-12-31
Value0.04950.0
Percentage of AdditionsToLongTermDebtIssuedLessIssuanceDiscount0.0100.00.0

aa:AdjustedEbitda

aa:AdjustedEbitda


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value625569398359185375340400484402740839969655902619546613425358393257
Percentage of AdjustedEbitda100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:AdjustedEbitda us-gaap:StatementBusinessSegments

aa:Alumina


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value12422797119881931332233693726836606383925622032272971717811415
Percentage of AdjustedEbitda19.839.924.433.147.651.539.155.876.292.592.378.765.859.862.332.841.648.540.221.829.05.8

aa:Aluminum


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value460283181116-34.06275433.0-96.0-53.073231153234303221206152183180165
Percentage of AdjustedEbitda73.649.745.532.3-18.416.522.110.80.6-23.9-7.28.723.823.425.948.940.533.635.851.145.864.2

aa:Bauxite


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value415912012413112013213411212611010610011010611398110102979977
Percentage of AdjustedEbitda6.610.430.234.570.832.038.833.523.131.314.912.610.316.811.818.317.917.924.027.125.230.0

aa:CostsAndOperatingExpensesAndNonoperatingIncomeExpenses

aa:CostsAndOperatingExpensesAndNonoperatingIncomeExpenses


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value237225582355234322532162273726192888262729752984316926782958267626222237266022272267
Percentage of CostsAndOperatingExpensesAndNonoperatingIncomeExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:CurtailmentOfSmeltingCapacity us-gaap:RealEstateProperties

aa:CurtailmentOfSmeltingCapacity

aa:SanCiprianFacility


Curtailment
Period End2020-10-31
Value228000.0
Percentage of CurtailmentOfSmeltingCapacity100.0

aa:DefinedBenefitPensionPlansNetPeriodicBenefitCost

aa:DefinedBenefitPensionPlansNetPeriodicBenefitCost


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value1212353634332930303031344140282827282320121114
Percentage of DefinedBenefitPensionPlansNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:DefinedBenefitPlanEmployersContributionPercentageOnAnnualBasis us-gaap:RetirementPlanName

aa:DefinedBenefitPlanEmployersContributionPercentageOnAnnualBasis

aa:TwoThousandTwentyActionPlanOne


Defined
Period End2020-12-31
Value0
Percentage of DefinedBenefitPlanEmployersContributionPercentageOnAnnualBasis0.0

aa:DefinedBenefitPlanNumberOfEmployeesReduced us-gaap:RetirementPlanName

aa:DefinedBenefitPlanNumberOfEmployeesReduced

aa:TwoThousandTwentyActionPlanThree


Defined
Period End2020-09-30
Value685.0
Percentage of DefinedBenefitPlanNumberOfEmployeesReduced100.0

aa:DiscreteTaxBenefitExpense

aa:DiscreteTaxBenefitExpense


Discrete
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value0-1000000.0-2000000.001000000.0
Percentage of DiscreteTaxBenefitExpense0.0100.0100.00.0100.0

aa:EstimatedAnnualizedEffectiveTaxRate

aa:EstimatedAnnualizedEffectiveTaxRate


Estimated
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value-11.239.2138.23-2.4010.571-8.2331.3710.7220.035
Percentage of EstimatedAnnualizedEffectiveTaxRate100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

aa:FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet

aa:FinanceRelatedDerivative, us-gaap:OtherIncome


Fair
Period End2021-06-30
Value3000000.0
Percentage of FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet100.0

aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet

aa:EmbeddedCreditDerivative, us-gaap:NonoperatingIncomeExpense


Fair
Period End2020-09-30
Value4.0
Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet100.0

aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

aa:FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet

aa:EmbeddedCreditDerivative, us-gaap:OtherIncome


Fair
Period End2021-06-302021-03-31
Value1000000.0-5000000.0
Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet100.0100.0

aa:FinanceRelatedDerivative, us-gaap:OtherIncome


Fair
Period End2021-06-30
Value-1000000.0
Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet-100.0

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIncreaseDecreaseOther us-gaap:DerivativeInstrumentRisk

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIncreaseDecreaseOther

aa:FinanceRelatedDerivative


Fair
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-30
Value0.01.02.00.01.02.01.0-3.0-4.0-5.0-2.05.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIncreaseDecreaseOther0.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold us-gaap:DerivativeInstrumentRisk

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold

aa:FinanceRelatedDerivative


Fair
Period End2021-06-302021-03-31
Value7000000.0-15000000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold100.0100.0

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther us-gaap:DerivativeInstrumentRisk

aa:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther

aa:EmbeddedCreditDerivative


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-31
Value1.0-1.0-2.01.02.01.00.00.00.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther100.0100.0100.0100.0100.0100.00.00.00.0

aa:FinanceRelatedDerivative


Fair
Period End2021-06-302021-03-31
Value0.0-2.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther0.0200.0

aa:PowerRelatedDerivative


Fair
Period End2020-09-302020-06-30
Value-2.0-1.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther-200.0-50.0

aa:FullCurtailmentOfSmeltingCapacity us-gaap:RealEstateProperties, us-gaap:SubsequentEventType

aa:FullCurtailmentOfSmeltingCapacity

aa:SanCiprianFacility, us-gaap:SubsequentEvent


Full
Period End2020-10-08
Value228000.0
Percentage of FullCurtailmentOfSmeltingCapacity100.0

aa:GainLossOnDispositionOfAssetsAfterTax us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:GainLossOnDispositionOfAssetsAfterTax

stpr:MD, aa:EastalcoAluminumSmelterSite


Gain
Period End2021-06-30
Value89
Percentage of GainLossOnDispositionOfAssetsAfterTax100.0

aa:IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments us-gaap:ProductOrService

aa:IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments

aa:Energy


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-11.0-10.0-2.0-11.0-7.0-11.0-12.0-9.0-10.0-11.0
Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:Mining


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-9.0-1.0-9.0-5.0-3.0-6.0-1.0-7.0-3.0-5.0
Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments81.810.0450.045.542.954.58.377.830.045.5

aa:OtherProducts


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value2.01.00.04.03.04.03.07.00.03.0
Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments-18.2-10.0-0.0-36.4-42.9-36.4-25.0-77.8-0.0-27.3

aa:IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:MaadenJointVenture


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-26.0-11.0-5.010.0193.0127.01417
Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments236.4110.0250.0-90.9-271.4-27.3-100.0-77.8-140.0-154.5

aa:IncomeLossFromEquityMethodInvestmentsNonoperating

aa:IncomeLossFromEquityMethodInvestmentsNonoperating


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value265.0-3.0-14.0-22.0-7.0-15.0-7.0-15.0-12.0-19.01.03.0-2.051-13.0-3.0-7.0
Percentage of IncomeLossFromEquityMethodInvestmentsNonoperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments us-gaap:ProductOrService

aa:IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments

aa:Energy


Income
Period End2020-09-302020-06-302020-03-312019-09-302019-06-30
Value-1.0-1.02.01.0-1.0
Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments100.0100.0100.0100.0100.0

aa:Mining


Income
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1.00.00.0-2.03.01.00.02.0-8.0
Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments0.00.0-0.0200.0150.00.00.0-200.00.0

aa:OtherProducts


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-8.0-3.0-1.0-3.0-5.0-5.0-6.0-8.00.0-2.0
Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments0.00.00.0300.0500.0-250.00.0-800.0-0.00.0

aa:IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:MaadenJointVenture


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.04.02.01.01.03.02.0-1.02.0-6.0
Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments0.00.00.0-100.0-100.0150.00.0-100.0-200.00.0

aa:IncomeTaxExaminationReversalOfProvisionForIncomeTaxesReserve us-gaap:IncomeTaxAuthorityName

aa:IncomeTaxExaminationReversalOfProvisionForIncomeTaxesReserve

us-gaap:TaxAuthoritySpain


Income
Period End2020-12-31
Value32
Percentage of IncomeTaxExaminationReversalOfProvisionForIncomeTaxesReserve100.0

aa:IncomeTaxExpenseBenefitFromEstimatedAnnualizedEffectiveTaxRate

aa:IncomeTaxExpenseBenefitFromEstimatedAnnualizedEffectiveTaxRate


Income
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value95122394-334.01251058-183.067
Percentage of IncomeTaxExpenseBenefitFromEstimatedAnnualizedEffectiveTaxRate100.0100.0100.0100.0100.0100.0100.0100.0

aa:IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Increase
Period End2021-06-30
Value-6000000.0
Percentage of IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities100.0

aa:IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Increase
Period End2021-06-30
Value-6000000.0
Percentage of IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities100.0

aa:IncreaseInIncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType

aa:IncreaseInIncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice, us-gaap:SubsequentEvent


Increase
Period End2020-07-07
Value1000000.0
Percentage of IncreaseInIncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority100.0

aa:MinimumRequiredCashContributionToPensionPlan

aa:MinimumRequiredCashContributionToPensionPlan


Minimum
Period End2021-03-312020-09-302020-06-302020-03-31
Value135200.075
Percentage of MinimumRequiredCashContributionToPensionPlan100.0100.00.0100.0

aa:MinimumRequiredCashContributionToPensionPlan us-gaap:RetirementPlanSponsorLocation

country:US


Minimum
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312020-01-31
Value54499.00.04040
Percentage of MinimumRequiredCashContributionToPensionPlan0.036.345.00.053.30.0

us-gaap:ForeignPlan


Minimum
Period End2021-06-302021-03-312020-09-30
Value6.01415
Percentage of MinimumRequiredCashContributionToPensionPlan0.010.475.0

aa:MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders

aa:MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders


Minority
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.08.01610.0201.020400.05653240.03224
Percentage of MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders0.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0

aa:MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Minority
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.08.01610.0201.020400.05653240.03224
Percentage of MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders0.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0

aa:PaymentAmountRefundPercentage us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:PaymentAmountRefundPercentage

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Payment
Period End2020-09-30
Value50.0
Percentage of PaymentAmountRefundPercentage100.0

aa:PaymentOfContractTerminationCost us-gaap:RealEstateProperties

aa:PaymentOfContractTerminationCost

aa:IntalcoFacility


Payment
Period End2020-12-312020-09-30
Value4000000.01000000.0
Percentage of PaymentOfContractTerminationCost100.0100.0

aa:PaymentOfDisputedTaxAmountPercentage us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:PaymentOfDisputedTaxAmountPercentage

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Payment
Period End2020-09-30
Value50.0
Percentage of PaymentOfDisputedTaxAmountPercentage100.0

aa:PaymentsForFinancialContributionsForTheDivestitureOfBusinesses

aa:PaymentsForFinancialContributionsForTheDivestitureOfBusinesses


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value7.06.08.06.01212
Percentage of PaymentsForFinancialContributionsForTheDivestitureOfBusinesses100.0100.0100.0100.0100.0100.0

aa:ProposedAdministrativePenalties us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:ProposedAdministrativePenalties

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Proposed
Period End2020-09-17
Value91
Percentage of ProposedAdministrativePenalties100.0

aa:RestructuringAndOtherCharges

aa:RestructuringAndOtherCharges


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value337.0605.0372.0363185370113138177231
Percentage of RestructuringAndOtherCharges100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:RestructuringAndOtherCharges us-gaap:ConsolidationItems

us-gaap:CorporateNonSegment


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value30-8.0470.00.0-2.010318184.013173149
Percentage of RestructuringAndOtherCharges90.9-114.378.30.00.0-100.028.49.74.93.59.497.764.5

us-gaap:MaterialReconcilingItems


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value337.0605.0372.0363185370113138177
Percentage of RestructuringAndOtherCharges100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value3.015135.0374.02601673521091254.082
Percentage of RestructuringAndOtherCharges9.1214.321.7100.0100.0200.071.690.395.196.590.62.335.5

aa:RestructuringAndOtherCharges us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, aa:Alumina


Restructuring
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.03.00.02.0256150.01.01091.03.0
Percentage of RestructuringAndOtherCharges0.060.00.0100.070.58.10.00.979.00.61.3

us-gaap:OperatingSegments, aa:AluminumProductsSegment


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value3.015131.0372.04.0147353107162.079
Percentage of RestructuringAndOtherCharges9.1214.321.720.0100.0100.01.179.595.494.711.61.134.2

us-gaap:OperatingSegments, aa:Bauxite


Restructuring
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value0.01.00.05.0-1.01.00.01.0
Percentage of RestructuringAndOtherCharges0.020.00.02.7-0.30.90.00.6

aa:RestructuringAndOtherCharges us-gaap:Range, us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType

srt:Maximum, aa:LakeCharlesLouisianaUnitedStates, aa:CurtailedAnodeFacility, us-gaap:SubsequentEvent


Restructuring
Period End2021-07-28
Value30
Percentage of RestructuringAndOtherCharges0.0

srt:Minimum, aa:LakeCharlesLouisianaUnitedStates, aa:CurtailedAnodeFacility, us-gaap:SubsequentEvent


Restructuring
Period End2021-07-28
Value25
Percentage of RestructuringAndOtherCharges0.0

aa:RestructuringAndOtherCharges us-gaap:Range, us-gaap:StatementScenario

srt:Maximum, srt:ScenarioForecast


Restructuring
Period End2020-12-31
Value40
Percentage of RestructuringAndOtherCharges66.7

srt:Minimum, srt:ScenarioForecast


Restructuring
Period End2020-12-31
Value35
Percentage of RestructuringAndOtherCharges58.3

aa:RestructuringAndOtherCharges us-gaap:RealEstateProperties, us-gaap:RestructuringCostAndReserve

aa:WenatcheeAndIntalcoFacility, aa:AdditionalContractCosts


Restructuring
Period End2021-06-302021-03-31
Value3.06.0
Percentage of RestructuringAndOtherCharges9.185.7

aa:RestructuringAndOtherCharges us-gaap:RestructuringCostAndReserve

aa:AdditionalContractCosts


Restructuring
Period End2020-09-302020-06-30
Value4.011
Percentage of RestructuringAndOtherCharges80.029.7

aa:OtherMiscellaneousCharges


Restructuring
Period End2021-06-302021-03-31
Value1.04.0
Percentage of RestructuringAndOtherCharges3.057.1

aa:RestructuringAndOtherCharges us-gaap:RestructuringPlan

aa:TwoThousandNineteenRestructuringPlan


Restructuring
Period End2020-09-302020-06-302020-03-312019-09-30
Value0.01.01.037
Percentage of RestructuringAndOtherCharges0.02.750.020.0

aa:RestructuringAndOtherCharges us-gaap:RetirementPlanType

us-gaap:PensionPlansDefinedBenefit


Restructuring
Period End2021-06-30
Value39
Percentage of RestructuringAndOtherCharges118.2

aa:RestructuringAndOtherChargesEstimatedButNotIncurred us-gaap:Range, us-gaap:RealEstateProperties

aa:RestructuringAndOtherChargesEstimatedButNotIncurred

srt:Maximum, aa:SanCiprianFacility


Restructuring
Period End2020-10-31
Value40
Percentage of RestructuringAndOtherChargesEstimatedButNotIncurred100.0

srt:Minimum, aa:SanCiprianFacility


Restructuring
Period End2020-10-31
Value35
Percentage of RestructuringAndOtherChargesEstimatedButNotIncurred87.5

aa:RestructuringAndOtherChargesNet

aa:RestructuringAndOtherChargesNet


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value4.06.08.01.0394.00.01651730
Percentage of RestructuringAndOtherChargesNet100.0100.0100.0100.0100.0100.00.0100.0100.0100.0

aa:RestructuringAndOtherChargesNet us-gaap:RestructuringCostAndReserve

aa:OtherExitCosts


Restructuring
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value4.06.08.04.0213.01.01211128
Percentage of RestructuringAndOtherChargesNet100.0100.0100.0400.053.875.00.073.364.793.3

us-gaap:EmployeeSeverance


Restructuring
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0-3.0181.0-1.0446.02.0
Percentage of RestructuringAndOtherChargesNet0.0-300.046.225.00.026.735.36.7

aa:SegmentReportingInformationCorporateExpenses

aa:SegmentReportingInformationCorporateExpenses


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value28263024212722272824212226273234363344475036
Percentage of SegmentReportingInformationCorporateExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses

aa:SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value155176165154146164171177167165164166184188177183180168167171170165176179
Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses us-gaap:StatementBusinessSegments

aa:Alumina


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value504645413749575455484748495352535349434847454748
Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses32.326.127.326.625.329.933.330.532.929.128.728.926.628.229.429.029.429.225.728.127.627.326.726.8

aa:Aluminum


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value73738280798184888589899110810610410610810173721041037777
Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses47.141.549.751.954.149.449.149.750.953.954.354.858.756.458.857.960.060.143.742.161.262.443.843.0

aa:Bauxite


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value325738333034303527282827272921241918202119172123
Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses20.632.423.021.420.520.717.519.816.217.017.116.314.715.411.913.110.610.712.012.311.210.311.912.8

aa:SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments

aa:SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value278.04.0-10.0-20.0-4.0-14.0-5.0-14.0-10.0-16.05.06.0-1.0-3.0-12.0-3.0-6.0-10.0-16.0-17.0-21.0-19.0-24.0
Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments us-gaap:StatementBusinessSegments

aa:Alumina


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value-1.0-5.0-2.0-4.0-8.0-9.0-9.00.03.0129.010.014-1.05.0-5.0-6.01.0-10.0-9.0-7.0-14.0-14.0-9.0
Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments-3.7-62.5-50.040.040.0225.064.3-0.0-21.4-120.0-56.2200.0233.3100.0-166.741.7200.0-16.7100.056.241.266.773.737.5

aa:Aluminum


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value28136.0-6.0-12.05.0-5.0-5.0-17.0-22.0-25.0-5.0-8.0-8.0-7.03.0-7.0115.0-10.0-7.04.0-2.0
Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments103.7162.5150.060.060.0-125.035.7100.0121.4220.0156.2-100.0-133.3266.758.3-100.0116.7-110.0-31.258.833.3-21.18.3

aa:SegmentReportingInformationIntersegmentEliminations

aa:SegmentReportingInformationIntersegmentEliminations


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value35-7.05.0-35.030-8.04025-1.0864721-152.076
Percentage of SegmentReportingInformationIntersegmentEliminations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationIntersegmentRevenues us-gaap:ConsolidationItems

aa:SegmentReportingInformationIntersegmentRevenues

us-gaap:IntersegmentElimination


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value5255515445675365745826246956568167747667078126285955841686155950550117711922
Percentage of SegmentReportingInformationIntersegmentRevenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationIntersegmentRevenues us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IntersegmentElimination, aa:Alumina


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value343364314329289336330369445417567544536454580398384361377317321292357396
Percentage of SegmentReportingInformationIntersegmentRevenues65.366.157.758.053.958.556.759.164.063.669.570.370.064.271.463.464.561.822.420.363.658.320.220.6

us-gaap:IntersegmentElimination, aa:Aluminum


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value3.02.05.02.02.03.06.04.04.03.04.06.04.04.05.09.03.04.09479182.03410521132
Percentage of SegmentReportingInformationIntersegmentRevenues0.60.40.90.40.40.51.00.60.60.50.50.80.50.60.61.40.50.756.258.90.46.859.458.9

us-gaap:IntersegmentElimination, aa:Bauxite


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value179185225236245235246251246236245224226249227221208219202192182175285305
Percentage of SegmentReportingInformationIntersegmentRevenues34.133.641.441.645.740.942.340.235.436.030.028.929.535.228.035.235.037.512.012.336.034.916.115.9

aa:SegmentReportingInformationOtherIncomeExpenseNet us-gaap:ConsolidationItems

aa:SegmentReportingInformationOtherIncomeExpenseNet

us-gaap:MaterialReconcilingItems


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value2.06.011151735321811183.010.036238351433923-56.0597414253
Percentage of SegmentReportingInformationOtherIncomeExpenseNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationTransformation

aa:SegmentReportingInformationTransformation


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value13118.01110.0166.06.0-3.0-2.01.0-1.01.02.0-10.0112820
Percentage of SegmentReportingInformationTransformation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationUnrelatedPartySales us-gaap:ConsolidationItems, us-gaap:RelatedPartyTransactionsByRelatedParty

aa:SegmentReportingInformationUnrelatedPartySales

us-gaap:OperatingSegments, aa:ThirdPartySales


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value282928652384236021442376241725482688269733193366355830722936266826082417229220322023185522152395
Percentage of SegmentReportingInformationUnrelatedPartySales100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationUnrelatedPartySales us-gaap:ConsolidationItems, us-gaap:RelatedPartyTransactionsByRelatedParty, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, aa:ThirdPartySales, aa:Alumina


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value688760620697603707718771864897113211011068914937713749734618585601496707878
Percentage of SegmentReportingInformationUnrelatedPartySales24.326.526.029.528.129.829.730.332.133.334.132.730.029.831.926.728.730.427.028.829.726.731.936.7

us-gaap:OperatingSegments, aa:ThirdPartySales, aa:Aluminum


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value210220471685160714751598163416771757173521072198241321111920185117791613-6.013461335131510.02.0
Percentage of SegmentReportingInformationUnrelatedPartySales74.371.470.768.168.867.367.665.865.464.363.565.367.868.765.469.468.266.7-0.366.266.070.90.50.1

us-gaap:OperatingSegments, aa:ThirdPartySales, aa:Bauxite


Segment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value39587956667165100676580677747791048070919387441626
Percentage of SegmentReportingInformationUnrelatedPartySales1.42.03.32.43.13.02.73.92.52.42.42.02.21.52.73.93.12.94.04.64.32.40.71.1

aa:UnfavorableFavorableImpactIncomeTaxExpenseBenefit

aa:UnfavorableFavorableImpactIncomeTaxExpenseBenefit


Unfavorable
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value16-28.0-350.0379-46.0-971.0298839.0
Percentage of UnfavorableFavorableImpactIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:WeightedAverageExercisePriceOfUnderwaterOptions us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

aa:WeightedAverageExercisePriceOfUnderwaterOptions

us-gaap:EmployeeStockOption


Weighted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value8.4435.670.3526.526.4526.55-0.1632.8233.7738.49
Percentage of WeightedAverageExercisePriceOfUnderwaterOptions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses

us-gaap:AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.04.01.04.00.02.0692.01.01.0
Percentage of AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses0.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates

us-gaap:AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates


Accrual
Period End2021-06-302021-03-312019-12-312019-09-302019-06-302019-03-31
Value-10000000.0-7000000.0000-1000000.0
Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates100.0100.00.00.00.0100.0

us-gaap:AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates us-gaap:LossContingenciesByNatureOfContingency

aa:ClosedSiteInBrazil


Accrual
Period End2021-06-30
Value-5000000.0
Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates50.0

aa:ClosedSurinameSite


Accrual
Period End2021-06-30
Value-5000000.0
Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates50.0

us-gaap:AccrualForEnvironmentalLossContingenciesPayments1

us-gaap:AccrualForEnvironmentalLossContingenciesPayments1


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value6.05.05.05.06.03.05.02.07.03.0-7.0-4.0-5.021-8.015
Percentage of AccrualForEnvironmentalLossContingenciesPayments1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetImpairmentCharges us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType

us-gaap:AssetImpairmentCharges

aa:LakeCharlesLouisianaUnitedStates, aa:CurtailedAnodeFacility, us-gaap:SubsequentEvent


Asset
Period End2021-07-28
Value20
Percentage of AssetImpairmentCharges100.0

us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:HedgingDesignation

us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths

aa:FinanceRelatedDerivative, us-gaap:CashFlowHedging, us-gaap:DesignatedAsHedgingInstrument


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value16-14.0-1.0-2.0-2.06.0
Percentage of CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths100.0100.0100.0100.0100.0100.0

aa:PowerRelatedDerivative, us-gaap:CashFlowHedging, us-gaap:DesignatedAsHedgingInstrument


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-68.0-145.0-49.0-34.0-27.016
Percentage of CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths-425.01035.74900.01700.01350.0266.7

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-5000000.0-6000000.0-6000000.0-5000000.0-5000000.0-4000000.0-3000000.0-2000000.0-2000000.0-3000000.0-3000000.0-3000000.0-4000000.0-3000000.0-3000000.0-3000000.0-4000000.0-3000000.0-5000000.0-3000000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-50000000.0-51000000.0-54000000.0-54000000.0-53000000.0-51000000.0-44000000.0-43000000.0-42000000.0-42000000.0-44000000.0-47000000.0-52000000.0-55000000.0-46000000.0-47000000.0-46000000.0-46000000.0-47000000.0-36000000.0-10000000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses1000.0850.0900.01080.01060.01275.01466.72150.02100.01400.01466.71566.71300.01833.31533.31566.71150.01533.3940.01200.00.0

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-4000000.0-4000000.0-4000000.0-4000000.0-4000000.0-3000000.00-1000000.0-2000000.0-1000000.0-2000000.0-1000000.0-3000000.0-2000000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer

us-gaap:DefinedBenefitPlanContributionsByEmployer


Defined
Period End2021-04-012018-12-312018-09-302018-06-30
Value50020100605
Percentage of DefinedBenefitPlanContributionsByEmployer100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer dei:LegalEntity, us-gaap:DebtInstrument

aa:AlcoaNederlandHoldingBV, aa:FourPointOneTwoFivePercentageSeniorNotesDueTwoThousandAndTwentyNine


Defined
Period End2021-04-01
Value500
Percentage of DefinedBenefitPlanContributionsByEmployer100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:SubsequentEventType

aa:AlcoaNederlandHoldingBV, aa:FourPointOneTwoFivePercentageSeniorNotesDueTwoThousandAndTwentyNine, us-gaap:SubsequentEvent


Defined
Period End2021-04-01
Value500
Percentage of DefinedBenefitPlanContributionsByEmployer100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer us-gaap:SubsequentEventType

us-gaap:SubsequentEvent


Defined
Period End2021-04-01
Value500
Percentage of DefinedBenefitPlanContributionsByEmployer100.0

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value737372737374818182818584829010010198991028031
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanInterestCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value4.04.04.05.05.05.08.010.010.08.08.08.09.09.010.09.09.09.08.06.01.0
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value292940414142545556565756555961626061574419
Percentage of DefinedBenefitPlanInterestCost725.0725.01000.0820.0820.0840.0675.0550.0560.0700.0712.5700.0611.1655.6610.0688.9666.7677.8712.5733.31900.0

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value6.0178.07.05.07.02013131213-43.013-15.012131212118.01.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value50128641353697356830422662084530313028263312
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost833.370.61075.0585.7700.0514.3485.0269.2523.1250.0323.1-618.61600.0-300.0250.0238.5250.0233.3236.4412.51200.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments


Defined
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-31
Value-5.00.01.0-3.0-76.00.038-12.0-175.0-167.023
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Defined
Period End2021-03-31
Value17
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments0.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments us-gaap:RetirementPlanName

aa:TwoThousandTwentyActionPlanOne


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.0170.00.00.0-1.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments0.00.0-0.00.00.033.3

aa:TwoThousandTwentyActionPlanTwo


Defined
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.00.0-2.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments-0.00.00.066.7

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302018-12-312018-09-302018-06-302018-03-31
Value0.0170.00.02.00.00.00.028
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments0.00.0-0.00.0200.0-0.0-0.0-0.0121.7

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-31
Value-5.00.0-1.0-3.00.00.0-38.00.00.00.0-5.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments100.00.0-100.0100.0-0.00.0-100.0-0.0-0.0-0.0-21.7

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1


Defined
Period End2020-12-312020-09-302019-12-312019-09-302018-12-31
Value49-5.0695.00.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1100.0100.0100.0100.00.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Defined
Period End2021-03-31
Value-26.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.0

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyOneActionPlanTwo


Defined
Period End2021-06-30
Value-39.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 us-gaap:RetirementPlanName

aa:TwoThousandTwentyActionPlanOne


Defined
Period End2021-06-302021-03-31
Value0.0-26.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.00.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312018-12-312018-09-30
Value0.0-26.00.056
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.00.00.00.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302020-12-312020-09-302019-12-312019-09-302018-12-312018-09-302018-06-302017-12-312017-09-302016-12-312016-09-30
Value-39.0-46.0-5.0-68.0-5.0-11.0-232.0-167.0-2.0-3.0-3.0-13.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements10.0-93.9100.0-98.6-100.00.00.00.00.00.00.00.0

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1 us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RestructuringCostAndReserve

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1

aa:WarrickRollingMill, aa:SeveranceAndFacilityExitCost


Defined
Period End2021-06-302021-03-31
Value0.09.0
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments10.0100.0

us-gaap:DefinedBenefitPlanServiceCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value1.02.02.01.01.01.01.01.01.01.01.02.01.01.01.02.01.01.01.01.0
Percentage of DefinedBenefitPlanServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value5.05.013141314121212121313141418181718191812
Percentage of DefinedBenefitPlanServiceCost500.0250.0650.01400.01300.01400.01200.01200.01200.01200.01300.0650.01400.01400.01800.0900.01700.01800.01900.01800.00.0

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Effect
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value9.0-11.013-1.0-2.0-24.04.0-10.05.0-6.0-3.06.0-11.04.06.0-3.04.07.0
Percentage of EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate


Effective
Period End2021-06-302021-03-312019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-30
Value021.00.210000.210.21000.350.35
Percentage of EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate0.0100.0100.00.00.00.0100.0100.00.00.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

aa:FinanceRelatedDerivative, us-gaap:CostOfSales


Fair
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-31
Value8.04.07.0-4.0-8.0-19.0-17.0-42.0-107.0-11.0-12.0-13.0-13.0-3.0-2.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:FinanceRelatedDerivative, us-gaap:NonoperatingIncomeExpense


Fair
Period End2021-06-30
Value3.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings10.0

aa:PowerRelatedDerivative, us-gaap:Sales


Fair
Period End2020-09-302020-06-302020-03-31
Value-5.06.0-1.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1-125.085.725.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss us-gaap:DerivativeInstrumentRisk

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss

aa:FinanceRelatedDerivative


Fair
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-31
Value2.0-10.0-5.0-7.0-61.0-37.07.01468-56.030-24.0-12.0-7.0-62.0-169.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings

aa:EmbeddedCreditDerivative, us-gaap:NonoperatingIncomeExpense


Fair
Period End2021-06-302020-09-302020-06-30
Value1.03.0-2.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings100.0100.0100.0

aa:EmbeddedCreditDerivative, us-gaap:OtherIncome


Fair
Period End2021-03-312017-03-312016-12-312016-09-30
Value-6.0-5.012-8.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings0.00.00.00.0

aa:FinanceRelatedDerivative, us-gaap:NonoperatingIncomeExpense


Fair
Period End2021-06-30
Value-1.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings-100.0

aa:PowerRelatedDerivative, us-gaap:Sales


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-67.0-40.0-32.0-27.0-1.0-17.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings-6700.00.00.0-900.050.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome us-gaap:DerivativeInstrumentRisk

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome

aa:FinanceRelatedDerivative


Fair
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-21.027-2.00.02.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome100.0100.0100.00.0100.0

aa:PowerRelatedDerivative


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value41727335633567-468.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome-1985.71011.10.0-16750.00.0-23400.0

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax


Foreign
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value-10.04.0-12.05.0-2.0-11.00.01.0-5.0-12.08.02230-3.0-2.0-1.011-16.013-8.0-1.0-12.0-23.035
Percentage of ForeignCurrencyTransactionGainLossBeforeTax100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnDispositionOfAssets

us-gaap:GainLossOnDispositionOfAssets


Gain
Period End2021-06-302021-03-312020-06-302020-03-31
Value9826-1.0177
Percentage of GainLossOnDispositionOfAssets100.0100.0100.0100.0

us-gaap:GainLossOnDispositionOfAssets1

us-gaap:GainLossOnDispositionOfAssets1


Gain
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value9727-1.0-2.0-1.0177-3.05.0-7.08.0-3.0-2.05.01.0-1.0-4.01200.013234-2.0-1.02.0
Percentage of GainLossOnDispositionOfAssets1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnDispositionOfAssets1 us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Gain
Period End2021-06-302021-03-31
Value3.027
Percentage of GainLossOnDispositionOfAssets13.1100.0

us-gaap:GainLossOnDispositionOfAssets1 us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:FormerEastalcoSiteSaleAndWarrickRollingMill


Gain
Period End2021-06-30
Value93
Percentage of GainLossOnDispositionOfAssets195.9

aa:GumSprings


Gain
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.01.0180
Percentage of GainLossOnDispositionOfAssets1-0.0-0.0-100.0101.7

aa:WarrickRollingMill


Gain
Period End2021-03-31
Value27
Percentage of GainLossOnDispositionOfAssets1100.0

us-gaap:GainLossOnDispositionOfAssets1 us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

stpr:MD, aa:EastalcoAluminumSmelterSite


Gain
Period End2021-06-30
Value90
Percentage of GainLossOnDispositionOfAssets192.8

us-gaap:IncomeLossFromEquityMethodInvestments us-gaap:ProductOrService

us-gaap:IncomeLossFromEquityMethodInvestments

aa:Energy


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1110.04.0128.09.0138.01111
Percentage of IncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:Mining


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value8.01.09.05.05.03.00.07.01.013
Percentage of IncomeLossFromEquityMethodInvestments72.710.0225.041.762.533.30.087.59.1118.2

aa:OtherProducts


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value6.02.01.0-1.02.01.01.00.0-1.0
Percentage of IncomeLossFromEquityMethodInvestments54.520.025.0-8.325.011.112.50.0-9.1

us-gaap:IncomeLossFromEquityMethodInvestments us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:MaadenJointVenture


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value267.03.0-11.0-20.0-6.0-14.0-6.0-16.0-11.0
Percentage of IncomeLossFromEquityMethodInvestments236.470.075.0-91.7-250.0-66.7-107.7-75.0-145.5-100.0

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions


Income
Period End2021-06-302021-03-312020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value3511-1.0-4.0-9.02.0-17.03.0-28.00.05.06.0-8.013-15.01.0-14.0-14.0-16.0-4.0-21.0
Percentage of IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsPayableTrade

us-gaap:IncreaseDecreaseInAccountsPayableTrade


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value96-64.011296-62.0-121.046-55.015-159.0-30.0-30.01.0-106.02689064-45.0181-42.019-152.0-48.0
Percentage of IncreaseDecreaseInAccountsPayableTrade100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedLiabilities

us-gaap:IncreaseDecreaseInAccruedLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value-23000000.03000000.013000000.0-46000000.0-35000000.0-85000000.0-28000000.0-96000000.0-33000000.0-18000000.0-31000000.0-45000000.0-57000000.0-186000000.0-243000000.0-82000000.0-57000000.0-181000000.018000000.0-124000000.0-9000000.0-205000000.0-23000000.0
Percentage of IncreaseDecreaseInAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedTaxesPayable

us-gaap:IncreaseDecreaseInAccruedTaxesPayable


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value41-1.0248818-11.014-2.0-299.0-43.0-7.014717849659-27.0-17.0-45.022-65.0-60.0-207.0
Percentage of IncreaseDecreaseInAccruedTaxesPayable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value1222188313-32.00.0-8.02210.0124036131142433.0-4.09.0
Percentage of IncreaseDecreaseInOtherNoncurrentAssets100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherNoncurrentLiabilities

us-gaap:IncreaseDecreaseInOtherNoncurrentLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value-27.0-31.0-12.0-15.0-18.0-43.0-3.0-6.0-22.01.0-39.0-28.0-7.0-23.0-50.01219-20.055
Percentage of IncreaseDecreaseInOtherNoncurrentLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInPensionPlanObligations

us-gaap:IncreaseDecreaseInPensionPlanObligations


Increase
Period End2020-12-312020-09-302020-06-302020-03-312018-12-31
Value3.00.0156460.0
Percentage of IncreaseDecreaseInPensionPlanObligations100.00.0100.0100.00.0

us-gaap:IncreaseDecreaseInPensionPlanObligations us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyOneActionPlanTwo


Increase
Period End2021-06-30
Value90
Percentage of IncreaseDecreaseInPensionPlanObligations0.0

us-gaap:IncreaseDecreaseInPensionPlanObligations us-gaap:RetirementPlanName

aa:TwoThousandTwentyActionPlanOne


Increase
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.00.018
Percentage of IncreaseDecreaseInPensionPlanObligations0.00.00.039.1

aa:TwoThousandTwentyActionPlanTwo


Increase
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.00.028
Percentage of IncreaseDecreaseInPensionPlanObligations0.00.00.060.9

us-gaap:IncreaseDecreaseInPostretirementObligations

us-gaap:IncreaseDecreaseInPostretirementObligations


Increase
Period End2020-12-312018-12-31
Value0.0-23.0
Percentage of IncreaseDecreaseInPostretirementObligations0.0100.0

us-gaap:IncreaseDecreaseInPostretirementObligations us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Increase
Period End2021-03-31
Value40
Percentage of IncreaseDecreaseInPostretirementObligations0.0

us-gaap:IncreaseDecreaseInPostretirementObligations us-gaap:RetirementPlanName

aa:TwoThousandTwentyActionPlanFour


Increase
Period End2020-12-31
Value0.0
Percentage of IncreaseDecreaseInPostretirementObligations0.0

aa:TwoThousandTwentyActionPlanOne


Increase
Period End2021-06-302021-03-31
Value-6.0112
Percentage of IncreaseDecreaseInPostretirementObligations0.00.0

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value-1.0-57.04.0-8.0-2.0-11.043-2.0-55.0-13.035-11.010.0-2.019-10.0-39.0-13.03011-25.0
Percentage of IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInReceivables

us-gaap:IncreaseDecreaseInReceivables


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value5821210.098-194.070-156.0-33.0-52.0-42.0-166.00.0252-43.06.03782-7.01081021.023-96.0
Percentage of IncreaseDecreaseInReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends

us-gaap:IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends


Incremental
Period End2021-06-302021-03-312020-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value3000000.03000000.01000000.0002000000.01000000.001000000.01000000.01000000.0
Percentage of IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends100.0100.0100.00.00.0100.0100.00.0100.0100.0100.0

us-gaap:LineOfCreditFacilityCommitmentFeeAmount us-gaap:CreditFacility, us-gaap:DebtInstrument

us-gaap:LineOfCreditFacilityCommitmentFeeAmount

us-gaap:RevolvingCreditFacility, aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven


Line
Period End2021-04-012021-03-31
Value15001255
Percentage of LineOfCreditFacilityCommitmentFeeAmount100.0100.0

us-gaap:LineOfCreditFacilityIncreaseDecreaseForPeriodNet us-gaap:CreditFacility, us-gaap:DebtInstrument

us-gaap:LineOfCreditFacilityIncreaseDecreaseForPeriodNet

us-gaap:RevolvingCreditFacility, aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven


Line
Period End2021-03-31
Value-245000000.0
Percentage of LineOfCreditFacilityIncreaseDecreaseForPeriodNet100.0

us-gaap:LineOfCreditFacilityIncreaseDecreaseForPeriodNet us-gaap:StatementScenario, us-gaap:CreditFacility, us-gaap:DebtInstrument

srt:ScenarioForecast, us-gaap:RevolvingCreditFacility, aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven


Line
Period End2021-06-30
Value-245000000.0
Percentage of LineOfCreditFacilityIncreaseDecreaseForPeriodNet0.0

us-gaap:MaturitiesOfSeniorDebt us-gaap:DebtInstrument

us-gaap:MaturitiesOfSeniorDebt

aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour


Maturities
Period End2021-04-07
Value750
Percentage of MaturitiesOfSeniorDebt100.0

us-gaap:MaturitiesOfSeniorDebt us-gaap:DebtInstrument, us-gaap:SubsequentEventType

aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour, us-gaap:SubsequentEvent


Maturities
Period End2021-04-07
Value750
Percentage of MaturitiesOfSeniorDebt100.0

us-gaap:OperatingLeaseCost

us-gaap:OperatingLeaseCost


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value17211719201818212019
Percentage of OperatingLeaseCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-12-312018-09-302018-06-30
Value3000000.01000000.0-10000000.0-3000000.02000000.0-3000000.0-6000000.0-2000000.0-6000000.04000000.02000000.0
Percentage of OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value253131-133.0-32.0-127.038-69.01910.041-179.0398183
Percentage of OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value51-60.01241794-245.045-75.04.02.0-10.0-54.0-151.0
Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value204-176.02985.0135-663.0117-224.040-22.0-18.0-142.0-445.0
Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value5.0-3.00.00.0-1.0-20.0-13.0-3.0-1.06.05.05.0-10.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxNoncontrollingInterest100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-266.0-204.0-247.0-240.0-390.0701-173.06179-288.0372-29.0-175.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value5.0-3.00.00.0-1.0-20.0-13.0-3.0-1.06.05.05.0-10.0-20.0-7.0-5.0-21.0830.0-10.016-2.02.01.0
Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-266.0-204.0-247.0-240.0-390.0701-173.06179-288.0372-29.0-175.0550-410.0-415.0-6.0
Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax-5320.06800.00.00.039000.0-3505.01330.8-2033.3-7900.0-4800.07440.0-580.01750.0-2750.05857.18300.028.6

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value59-62.01141495-265.029-84.01.09.0-11.0-45.0-159.0
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value191-249.0-82.0-267.0-382.076-125.0-144.0129-269.0175227-437.0
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302015-12-312015-09-30
Value-2.0127.0-1.01.00.0113.010.0-4.0-2.0-1.015-6.0-19.01.01.0-1.08.0-10.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-164.0-69.0251931812018938784.0231-174.0-1.0-75.07136.0-53.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax8200.00.02091.71328.6-18100.02000.00.0345.52600.00.02310.04350.050.07500.04753.3-100.0278.9

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302015-12-312015-09-30
Value-2.0115.0-1.01.04.07.03.08.0-3.0-2.015-4.0-19.01.01.0-1.08.0-9.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-164.0-71.0236871771418927623.0236-173.0-7.0-67.06934.0-55.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax8200.00.02145.51740.0-17700.01400.04725.0385.72066.70.02950.05766.7350.00.04620.0-100.0289.5

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value256132387-35.0125-38.0-54.0138.0-42.0185-402.0-185.0-102.0661-49.0-122.0-43.0223-19.0-11.09.017-51.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value-3.0-1.010.03.0-2.03.06.02.0-1.06.0-4.0-2.0-1.015-5.0-20.01.01.0-2.0-1.06.0-9.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax-1.2-0.82.6-8.6-1.6-5.646.225.02.43.21.01.11.02.310.216.4-2.3-5.318.2-11.135.317.6

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-253.0-131.013332127-38.069-19.0-10.0-41.0179-398.0-183.0-101.0646-44.0-102.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax-98.8-99.234.4-91.4101.6100.0-127.8-146.2-125.097.696.899.098.999.097.789.883.6

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax

us-gaap:NoncontrollingInterest


Other
Period End2020-12-312020-09-302019-09-302018-09-302018-06-302018-03-312017-12-312017-09-302015-12-312015-09-30
Value1.02.04.0-1.00.0-1.00.0-2.00.0-1.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax100.0100.0100.0100.00.0100.00.0100.00.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value0.02.0156.04.06.00.011161.0-5.0-1.06.0-8.0202.02.0
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax0.00.01500.0300.00.00.00.0275.00.00.00.0100.00.0800.00.0-100.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-67.0-52.0-39.0-29.0-13.0-25.0-8.0-13.0-10.09.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax us-gaap:DerivativeInstrumentRisk

aa:DerivativeInstrumentLevel1And2


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-3.0-2.0-2.0-1.0-14.0-2.0-12.0-8.0-4.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax4.55.16.97.756.025.092.380.0-44.4

aa:DerivativeInstrumentLevel3


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-60.0-55.0-40.0-26.0-14.0-8.0-2.08.05.031
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax89.6105.8102.689.7107.732.025.0-61.5-50.0344.4

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:IncomeStatementLocation

aa:DerivativeInstrumentLevel1And2, us-gaap:DesignatedAsHedgingInstrument, us-gaap:CostOfSales


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value-1.00.0-2.0-1.0-7.03.0-7.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax1.5-0.06.97.728.0-37.553.8

aa:DerivativeInstrumentLevel1And2, us-gaap:DesignatedAsHedgingInstrument, us-gaap:Sales


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-2.0-2.00.00.0-7.0-5.0-5.0-8.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax3.05.1-0.0-0.028.062.538.580.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax us-gaap:DerivativeInstrumentRisk, us-gaap:StatementEquityComponents

aa:AluminumContracts, us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-72.0-41.0-31.0-21.0-1.0-13.0-10.0-9.0-12.0-13.0-21.0-26.0-34.0-27.0-48.0-33.0-31.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax107.578.879.572.47.752.0125.069.2120.0-144.40.00.00.00.00.00.00.0

aa:FinanceRelatedDerivative, us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value2.0-6.0-4.0-1.0-3.02.04.06.07.0187.04.04.09.05.05.01.01.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax-3.011.510.33.423.1-8.0-50.0-46.2-70.0200.00.00.00.00.00.00.00.00.0

aa:FinanceRelatedDerivative, us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value4.0-9.0-5.0-3.0-4.0-3.07.04.06.026116.07.0138.08.02.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax-6.017.312.810.330.812.0-87.5-30.8-60.0288.90.00.00.00.00.00.00.0

us-gaap:ForeignExchangeContract, us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2.01.0-2.0-3.0-7.0-8.0-6.0-4.0-4.0-4.0-4.0-3.00.01.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax-3.0-1.95.110.353.832.075.030.840.0-44.40.00.00.00.0

us-gaap:InterestRateContract, us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value-1.0-3.0-1.0-2.0-1.0-1.00.0-4.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax1.55.82.66.97.74.0-0.030.8

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax us-gaap:StatementEquityComponents

aa:NoncontrollingAndEquityInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-4.03.03.0-1.02.0-3.0-4.0-9.0-7.0-18.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax6.0-5.8-7.73.4-15.412.050.069.270.0-200.0

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value2.0-6.0-4.0-1.0-3.02.04.06.07.0187.04.04.09.05.05.01.01.03.034-5.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax-3.011.510.33.423.1-8.0-50.0-46.2-70.0200.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-67.0-52.0-39.0-29.0-13.0-25.0-9.0-13.0-10.09.0-14.0-23.0-27.0-13.0-38.0-25.0-29.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax100.0100.0100.0100.0100.0100.0112.5100.0100.0100.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1.0-4.0-4.00.0-2.01.03.04.05.0135.03.03.06.03.04.00.01.01.024-3.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-56.0-43.0-33.0-27.0-11.0-24.0-8.0-16.0-11.02.0-14.0-21.0-25.0-14.0-39.0-21.0-25.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax-5600.01075.0825.00.0550.0-2400.0-266.7-400.0-220.015.4-280.0-700.0-833.3-233.3-1300.0-525.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312016-09-302016-06-30
Value1.0-2.0-2.01.01.0-1.01.02.02.05.02.01.01.03.02.01.01.02.010.0-2.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-11.0-9.0-16.02.02.01.0-1.03.01.07.00.0-2.0-2.01.01.0-4.0-4.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax-1100.0450.0800.0200.0200.0-100.0-100.0150.050.0140.00.0-200.0-200.033.350.0-400.0-400.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312016-09-302016-06-302016-03-312015-12-31
Value1.01.01.03.01.01.01.02.01.01.02.01.00.01.00.01.01.02.01.00.02.02.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.00.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value89611065752541224983455922722436505049
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax8900.06100.010600.01900.05200.05400.012200.02450.08300.04500.02950.022700.00.03600.00.05000.04900.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312016-09-302016-06-302016-03-312015-12-31
Value1.01.01.02.01.01.01.01.01.01.02.01.00.01.00.01.01.02.00.01.01.02.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.00.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value89601035550521204672445722517634474847
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax8900.06000.010300.02750.05000.05200.012000.04600.07200.04400.02850.022500.00.03400.00.04800.04700.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax

us-gaap:NoncontrollingInterest


Other
Period End2020-12-312020-09-302019-12-312019-09-302016-12-312016-09-302016-06-302016-03-312015-12-31
Value0.01.00.01.00.01.0-1.01.00.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax0.0100.00.0100.00.0100.0100.0100.00.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value0.01.03.02.02.02.02.03.0111.02.02.0482.03.02.02.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax0.00.00.0200.00.00.00.0300.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-397.0-303.0-351.0-333.0-513.0852-225.06080-352.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax us-gaap:DerivativeInstrumentRisk

aa:DerivativeInstrumentLevel1And2


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value6.0-14.0123.022-29.010.0-21.05.0-8.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax-1.54.6-3.4-0.9-4.3-3.4-4.4-35.06.22.3

aa:DerivativeInstrumentLevel3


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-394.0-300.0-367.0-338.0-536.0867-252.010480-317.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax99.299.0104.6101.5104.5101.8112.0173.3100.090.1

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax us-gaap:StatementEquityComponents

aa:NoncontrollingAndEquityInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-9.0114.02.01.01417-23.0-5.0-27.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax2.3-3.6-1.1-0.6-0.21.6-7.6-38.3-6.27.7

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value9.0-10.0-5.0-1.0-4.0-26.0-15.02.06.0271412-10.0-20.0-5.0-2.0-30.01203.02018-3.03.01.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax-2.33.31.40.30.8-3.16.73.37.5-7.70.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-397.0-303.0-351.0-333.0-513.0852-225.06080-352.0459-60.0-231.0635-514.0-545.0-50.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value6.0-7.0-4.00.0-3.0-19.0-10.01.04.01910.08.0-7.0-14.0-4.0-1.0-21.0841.01413-2.02.01.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-322.0-247.0-280.0-267.0-401.0677-181.04568-286.0358-50.0-200.0536-449.0-436.0-31.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax-5366.73528.67000.00.013366.7-3563.21810.04500.01700.0-1505.33580.0-625.02857.1-3828.611225.043600.0147.6

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax

us-gaap:NoncontrollingInterest


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value3.0-3.0-1.0-1.0-1.0-7.0-5.01.02.08.04.04.0-3.0-6.0-1.0-1.0-9.0362.06.05.0-1.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-75.0-56.0-71.0-66.0-112.0175-44.01512-66.0101-10.0-31.099-65.0-109.0-19.0
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax-2500.01866.77100.06600.011200.0-2500.0880.01500.0600.0-825.02525.0-250.01033.3-1650.06500.010900.0211.1

us-gaap:OtherDepreciationAndAmortization

us-gaap:OtherDepreciationAndAmortization


Other
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value161152170183184174172174172193194188195190179
Percentage of OtherDepreciationAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncashIncomeExpense

us-gaap:OtherNoncashIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value-29.01.0-21.0-6.0-1.0-4.0-11.05.0-1.0-23.0-5.0321814-1.0-34.012-9.0283.0-9.0-6.0-16.0
Percentage of OtherNoncashIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForRestructuring

us-gaap:PaymentsForRestructuring


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value111319303437255128143.06.08310.01513281723
Percentage of PaymentsForRestructuring100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForRestructuring us-gaap:RealEstateProperties

aa:IntalcoFacility


Payments
Period End2020-12-312020-09-302020-06-30
Value1.08.02.0
Percentage of PaymentsForRestructuring5.326.75.9

us-gaap:PaymentsForRestructuring us-gaap:RestructuringCostAndReserve

aa:OtherExitCosts


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-03-312016-12-31
Value10.01116202320154528113.04.0817.07.013
Percentage of PaymentsForRestructuring90.984.684.266.767.654.160.088.2100.078.6100.066.797.670.041.256.5

us-gaap:EmployeeSeverance


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value1.02.03.010.0111710.06.00.03.00.02.02.03.05.06.09.010.010.0
Percentage of PaymentsForRestructuring9.115.415.833.332.445.940.011.80.021.40.033.32.430.033.346.232.158.843.5

us-gaap:PaymentsForRestructuring us-gaap:RestructuringPlan

aa:AvilesAndLaCorunaSmelters


Payments
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value7.06.06.01212
Percentage of PaymentsForRestructuring63.646.220.035.332.4

aa:TwoThousandNineteenRestructuringPlan


Payments
Period End2020-09-302020-06-302020-03-31
Value2.09.013
Percentage of PaymentsForRestructuring6.726.535.1

us-gaap:PaymentsForRestructuring us-gaap:StatementGeographical, us-gaap:RestructuringPlan

stpr:TX, aa:ThePointComfortAluminaRefinery


Payments
Period End2020-09-302020-06-302020-03-31
Value0.01.01.0
Percentage of PaymentsForRestructuring0.02.92.7

us-gaap:PaymentsOfDividendsMinorityInterest

us-gaap:PaymentsOfDividendsMinorityInterest


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value75625546753184102722142611811182679889985757923450
Percentage of PaymentsOfDividendsMinorityInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionAndOtherPostretirementBenefitExpense

us-gaap:PensionAndOtherPostretirementBenefitExpense


Pension
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value111328282725283030293032393821212221
Percentage of PensionAndOtherPostretirementBenefitExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionContributions

us-gaap:PensionContributions


Pension
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value5076326024114810612487.05224865240243526212112191430
Percentage of PensionContributions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionContributions us-gaap:RetirementPlanSponsorLocation

country:US


Pension
Period End2020-12-31
Value250
Percentage of PensionContributions96.2

us-gaap:ProceedsFromDivestitureOfBusinesses us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:ProceedsFromDivestitureOfBusinesses

stpr:MD, aa:EastalcoAluminumSmelterSite


Proceeds
Period End2021-06-30
Value94
Percentage of ProceedsFromDivestitureOfBusinesses100.0

us-gaap:ProceedsFromMinorityShareholders

us-gaap:ProceedsFromMinorityShareholders


Proceeds
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.08.010.0201.020400.05653240.03224
Percentage of ProceedsFromMinorityShareholders0.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-1000000.0-3000000.00-3000000.00-1000000.0000-6000000.00-2000000.0-1000000.0-5000000.0-2000000.000-6000000.0
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.00.0100.00.0100.00.00.00.0100.00.0100.0100.0100.0100.00.00.0100.0

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment

us-gaap:ProceedsFromSaleOfPropertyPlantAndEquipment


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1145910.0-1.00.01990.0120.011
Percentage of ProceedsFromSaleOfPropertyPlantAndEquipment100.0100.00.0100.00.0100.00.0100.00.0100.0

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ProceedsFromStockOptionsExercised


Proceeds
Period End2021-06-302021-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10.04.00.01.00.01.00.01.07.0155.0200.018
Percentage of ProceedsFromStockOptionsExercised100.0100.00.0100.00.0100.00.0100.0100.0100.0100.0100.00.0100.0

us-gaap:ProvisionForDoubtfulAccounts

us-gaap:ProvisionForDoubtfulAccounts


Provision
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.00.00.02.00.01.00.020
Percentage of ProvisionForDoubtfulAccounts0.00.00.0100.00.0100.00.0100.0

us-gaap:RestructuringReserveAccrualAdjustment1 us-gaap:RealEstateProperties

us-gaap:RestructuringReserveAccrualAdjustment1

aa:IntalcoFacility


Restructuring
Period End2020-09-30
Value-4.0
Percentage of RestructuringReserveAccrualAdjustment1100.0

us-gaap:RestructuringReserveAccrualAdjustment1 us-gaap:RestructuringCostAndReserve

aa:SeveranceAndFacilityExitCost


Restructuring
Period End2020-09-30
Value-4.0
Percentage of RestructuringReserveAccrualAdjustment1100.0

us-gaap:RestructuringReserveAccrualAdjustment1 us-gaap:StatementGeographical, us-gaap:RestructuringCostAndReserve

country:BR, us-gaap:FacilityClosing


Restructuring
Period End2021-06-30
Value-5.0
Percentage of RestructuringReserveAccrualAdjustment10.0

country:SR, us-gaap:FacilityClosing


Restructuring
Period End2021-06-30
Value-5.0
Percentage of RestructuringReserveAccrualAdjustment10.0

stpr:TN, us-gaap:FacilityClosing


Restructuring
Period End2021-06-302021-03-31
Value0.0-12.0
Percentage of RestructuringReserveAccrualAdjustment10.00.0

us-gaap:RestructuringReserveTranslationAdjustment us-gaap:RestructuringPlan

us-gaap:RestructuringReserveTranslationAdjustment

aa:TwoThousandNineteenRestructuringPlan


Restructuring
Period End2020-09-302020-06-30
Value01000000.0
Percentage of RestructuringReserveTranslationAdjustment0.0100.0

us-gaap:RestructuringReserveTranslationAndOtherAdjustment

us-gaap:RestructuringReserveTranslationAndOtherAdjustment


Restructuring
Period End2020-12-312020-09-302020-06-302020-03-312018-01-31
Value1.01.00.04.0-19.0
Percentage of RestructuringReserveTranslationAndOtherAdjustment100.0100.00.0100.0100.0

us-gaap:RestructuringReserveTranslationAndOtherAdjustment us-gaap:RestructuringCostAndReserve

aa:OtherExitCosts


Restructuring
Period End2020-12-312020-09-302020-06-302020-03-31
Value-1.00.01.02.0
Percentage of RestructuringReserveTranslationAndOtherAdjustment-100.00.00.050.0

us-gaap:EmployeeSeverance


Restructuring
Period End2020-12-312020-09-302020-06-302020-03-31
Value2.01.0-1.02.0
Percentage of RestructuringReserveTranslationAndOtherAdjustment200.0100.00.050.0

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability


Right
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value4.08.0131618
Percentage of RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability100.0100.0100.0100.0100.0

us-gaap:ShortTermLeaseCost

us-gaap:ShortTermLeaseCost


Short
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1000000.01000000.01000000.001000000.02000000.001000000.03000000.0
Percentage of ShortTermLeaseCost100.0100.0100.00.0100.0100.00.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation


Stock
Period End2021-06-302021-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10.04.00.01.00.01.00.01.07.0156.0202.015
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.00.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10.04.00.01.00.01.00.01.07.0156.0202.015
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.00.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockholdersEquityOther

us-gaap:StockholdersEquityOther


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-31
Value0.01.0-1.01.00.02.00.01.01.04.02.0-11.0-2.0-15.03.02.04.02.06.0-4.01.00.0
Percentage of StockholdersEquityOther0.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:StockholdersEquityOther us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-1.01.00.01.01.00.00.00.04.01.04.00.0-18.03.02.03.0
Percentage of StockholdersEquityOther0.0100.0-0.0100.00.00.00.00.0100.050.0-36.4-0.0120.0100.0100.075.0

us-gaap:NoncontrollingInterest


Stockholders
Period End2021-06-302020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-31
Value1.00.00.01.00.01.01.01.0-15.0-1.03.00.00.01.02.06.0-4.01.00.0
Percentage of StockholdersEquityOther0.00.00.050.00.0100.0100.050.0136.450.0-20.00.00.025.0100.0100.0100.0100.00.0

us-gaap:TaxAdjustmentsSettlementsAndUnusualProvisions us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

us-gaap:TaxAdjustmentsSettlementsAndUnusualProvisions

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Tax
Period End2021-06-302021-03-312020-12-312020-09-30
Value3.04.013166
Percentage of TaxAdjustmentsSettlementsAndUnusualProvisions100.0100.0100.0100.0

us-gaap:TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax

us-gaap:TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax


Translation
Period End2020-09-302020-06-302020-03-312019-09-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302016-12-312016-09-30
Value0.0-12.06.02.01.00.01.06.02.04.02.0-10.06.0
Percentage of TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax0.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:UnrealizedGainLossOnDerivatives

us-gaap:UnrealizedGainLossOnDerivatives


Unrealized
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value2.05.01.0-3.02.0-11.06.08.0-6.017-2.0-6.0-19.03.0-4.04.0-6.0-3.0-7.0-17.0
Percentage of UnrealizedGainLossOnDerivatives100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:VariableLeaseCost

us-gaap:VariableLeaseCost


Variable
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value4.01.04.02.01.04.04.04.05.03.0
Percentage of VariableLeaseCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:AccrualEnvironmentalLossActiveRemediationFutureRemediationForSignificantIndividualSites

aa:AccrualEnvironmentalLossActiveRemediationFutureRemediationForSignificantIndividualSites


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value241254259260263268274207208212214
Percentage of AccrualEnvironmentalLossActiveRemediationFutureRemediationForSignificantIndividualSites100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

aa:AccrualForEnvironmentalLossContingenciesUndiscountedOneToFiveYear

aa:AccrualForEnvironmentalLossContingenciesUndiscountedOneToFiveYear


Accrual
Period End2021-06-302021-03-312020-09-30
Value166164197
Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedOneToFiveYear100.0100.0100.0

aa:AccrualForEnvironmentalLossContingenciesUndiscountedTwoToFiveYear

aa:AccrualForEnvironmentalLossContingenciesUndiscountedTwoToFiveYear


Accrual
Period End2020-12-31
Value142
Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedTwoToFiveYear100.0

aa:AccruedCappingClosurePostClosureAndEnvironmentalCost

aa:AccruedCappingClosurePostClosureAndEnvironmentalCost


Accrued
Period End2020-12-312019-12-312018-12-31
Value313933
Percentage of AccruedCappingClosurePostClosureAndEnvironmentalCost100.0100.0100.0

aa:AccruedCompensationAndRetirementCostsNoncurrent

aa:AccruedCompensationAndRetirementCostsNoncurrent


Accrued
Period End2020-12-312019-12-312018-12-31
Value116110107
Percentage of AccruedCompensationAndRetirementCostsNoncurrent100.0100.0100.0

aa:AccruedTaxesNoncurrent

aa:AccruedTaxesNoncurrent


Accrued
Period End2020-12-31
Value169
Percentage of AccruedTaxesNoncurrent100.0

aa:AluminumForecastedSalesDesignatedAsFairValueHedgesInKiloMetricTon us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

aa:AluminumForecastedSalesDesignatedAsFairValueHedgesInKiloMetricTon

aa:PowerRelatedDerivative, us-gaap:DesignatedAsHedgingInstrument


Aluminum
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-31
Value2018000.02074000.02130000.02187000.02244000.02347000.0
Percentage of AluminumForecastedSalesDesignatedAsFairValueHedgesInKiloMetricTon100.0100.0100.0100.0100.0100.0

aa:AluminumFuturesDesignatedAsFairValueHedgesInKiloMetricTon us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

aa:AluminumFuturesDesignatedAsFairValueHedgesInKiloMetricTon

aa:PowerRelatedDerivative, us-gaap:DesignatedAsHedgingInstrument


Aluminum
Period End2020-12-312020-03-312019-12-312018-12-31
Value2130000.02298000.02347000.02508000.0
Percentage of AluminumFuturesDesignatedAsFairValueHedgesInKiloMetricTon100.0100.0100.0100.0

aa:AmountCommittedUnderOutstandingSuretyBonds

aa:AmountCommittedUnderOutstandingSuretyBonds


Amount
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value1225240122159
Percentage of AmountCommittedUnderOutstandingSuretyBonds100.0100.0100.0100.0100.0

aa:AmountCommittedUnderOutstandingSuretyBonds us-gaap:StatementEquityComponents

aa:AlcoaCorporation


Amount
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value1514161422
Percentage of AmountCommittedUnderOutstandingSuretyBonds12.326.940.011.513.8

aa:ParentCo


Amount
Period End2020-12-31
Value3.0
Percentage of AmountCommittedUnderOutstandingSuretyBonds2.5

aa:AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Assessed
Period End2020-09-30
Value74
Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties100.0

aa:AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties us-gaap:ConsolidatedEntities, us-gaap:StatementScenario, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:AlcoaOfAustraliaLimited, srt:ScenarioForecast, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Assessed
Period End2020-09-30
Value74
Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties100.0

aa:AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Assessed
Period End2020-09-30
Value74
Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties100.0

aa:ClosureOfResidueAreas

aa:ClosureOfResidueAreas


Closure
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value278282231238219165
Percentage of ClosureOfResidueAreas100.0100.0100.0100.0100.0100.0

aa:DeferredEnergyCredits

aa:DeferredEnergyCredits


Deferred
Period End2020-12-312019-12-31
Value5650
Percentage of DeferredEnergyCredits100.0100.0

aa:DeferredTaxAssetsDepreciation

aa:DeferredTaxAssetsDepreciation


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value667291141187264
Percentage of DeferredTaxAssetsDepreciation100.0100.0100.0100.0100.0100.0

aa:DeferredTaxAssetsLeasingArrangements

aa:DeferredTaxAssetsLeasingArrangements


Deferred
Period End2020-12-312019-12-31
Value3741
Percentage of DeferredTaxAssetsLeasingArrangements100.0100.0

aa:DeferredTaxLiabilitiesDepreciation

aa:DeferredTaxLiabilitiesDepreciation


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value434438428432499529
Percentage of DeferredTaxLiabilitiesDepreciation100.0100.0100.0100.0100.0100.0

aa:DeferredTaxLiabilitiesGross

aa:DeferredTaxLiabilitiesGross


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value590600571668884
Percentage of DeferredTaxLiabilitiesGross100.0100.0100.0100.0100.0

aa:DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveLossAttributedToJointVenturePartners us-gaap:RetirementPlanType

aa:DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveLossAttributedToJointVenturePartners

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value-57.0-42.0-40.0-45.0-36.0
Percentage of DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveLossAttributedToJointVenturePartners100.0100.0100.0100.0100.0

aa:DefinedBenefitPlanExpectedFutureBenefitPayments us-gaap:RetirementPlanType

aa:DefinedBenefitPlanExpectedFutureBenefitPayments

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2020-12-31
Value560
Percentage of DefinedBenefitPlanExpectedFutureBenefitPayments100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-31
Value4150417541754845
Percentage of DefinedBenefitPlanExpectedFutureBenefitPayments741.10.00.00.0

aa:DefinedBenefitPlanFundedAmountsAttributedToJointVenturePartners us-gaap:RetirementPlanType

aa:DefinedBenefitPlanFundedAmountsAttributedToJointVenturePartners

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value-45.0-34.0-33.03730
Percentage of DefinedBenefitPlanFundedAmountsAttributedToJointVenturePartners100.0100.0100.0100.0100.0

aa:DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect us-gaap:RetirementPlanType

aa:DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value218107172251259
Percentage of DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value35083327324237333260
Percentage of DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect1609.23109.31884.91487.31258.7

aa:DefinedBenefitPlanNetFundedStatus us-gaap:RetirementPlanType

aa:DefinedBenefitPlanNetFundedStatus

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value892848973-1218.0-1286.0
Percentage of DefinedBenefitPlanNetFundedStatus100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value150314831354-2280.0-1818.0
Percentage of DefinedBenefitPlanNetFundedStatus168.5174.9139.2187.2141.4

aa:DefinedBenefitPlanNumberOfEmployeesOnRollingOperations us-gaap:RetirementPlanName

aa:DefinedBenefitPlanNumberOfEmployeesOnRollingOperations

aa:TwoThousandTwentyActionPlanSix


Defined
Period End2020-12-31
Value1170.0
Percentage of DefinedBenefitPlanNumberOfEmployeesOnRollingOperations100.0

aa:DefinedBenefitPlanNumberOfPlanParticipantsAffected

aa:DefinedBenefitPlanNumberOfPlanParticipantsAffected


Defined
Period End2020-12-312020-03-312019-12-312018-12-312018-09-30
Value11280.0450.018200.020600.020600.0
Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected100.0100.0100.0100.0100.0

aa:DefinedBenefitPlanNumberOfPlanParticipantsAffected us-gaap:RetirementPlanName

aa:TwoThousandTwentyActionPlanFive


Defined
Period End2020-12-31
Value430.0
Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected3.8

aa:TwoThousandTwentyActionPlanSix


Defined
Period End2020-12-31
Value900.0
Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected8.0

aa:Demolition

aa:Demolition


Demolition
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value728576113121103
Percentage of Demolition100.0100.0100.0100.0100.0100.0

aa:DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Disposal
Period End2020-12-31
Value1031
Percentage of DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation100.0

aa:DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Disposal
Period End2021-06-302021-03-31
Value6672
Percentage of DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed100.0100.0

aa:DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:RetirementPlanName

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill, aa:TwoThousandTwentyActionPlanOne


Disposal
Period End2021-06-302021-03-31
Value6672
Percentage of DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed100.0100.0

aa:DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentGrossNoncurrent us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentGrossNoncurrent

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Disposal
Period End2020-12-31
Value1423
Percentage of DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentGrossNoncurrent100.0

aa:EquityMethodInvestmentUnrecognizedGainLoss us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

aa:EquityMethodInvestmentUnrecognizedGainLoss

aa:ElysisLimitedPartnership


Equity
Period End2021-06-302021-03-312020-12-312020-09-30
Value-40.0-35.0-32.031
Percentage of EquityMethodInvestmentUnrecognizedGainLoss100.0100.0100.0100.0

aa:ExpectedFutureSiteSeparationAndTransactionCostsPayment us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:ExpectedFutureSiteSeparationAndTransactionCostsPayment

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Expected
Period End2020-11-30
Value100
Percentage of ExpectedFutureSiteSeparationAndTransactionCostsPayment100.0

aa:GasSupplyPrepayment

aa:GasSupplyPrepayment


Gas
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value439437458510471288
Percentage of GasSupplyPrepayment100.0100.0100.0100.0100.0100.0

aa:GasSupplyPrepayment us-gaap:ConsolidatedEntities, us-gaap:BalanceSheetLocation, us-gaap:FiniteLivedIntangibleAssetsByMajorClass, us-gaap:OtherOwnershipInterestsByName

srt:Subsidiaries, us-gaap:OtherNoncurrentAssets, us-gaap:ServiceAgreements, aa:AlcoaOfAustraliaLimited


Gas
Period End2020-12-312019-12-31
Value439437
Percentage of GasSupplyPrepayment100.0100.0

srt:Subsidiaries, us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:ServiceAgreements, aa:AlcoaOfAustraliaLimited


Gas
Period End2020-12-312019-12-31
Value4221
Percentage of GasSupplyPrepayment9.64.8

aa:GasSupplyPrepayment us-gaap:ConsolidatedEntities, us-gaap:FiniteLivedIntangibleAssetsByMajorClass, us-gaap:OtherOwnershipInterestsByName

srt:Subsidiaries, us-gaap:ServiceAgreements, aa:AlcoaOfAustraliaLimited


Gas
Period End2020-12-312019-12-312018-12-31
Value481458458
Percentage of GasSupplyPrepayment109.6104.8100.0

aa:IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Income
Period End2020-07-072020-06-302020-03-312019-12-31
Value152144129144
Percentage of IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority100.0100.0100.0100.0

aa:IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice, us-gaap:SubsequentEvent


Income
Period End2020-07-07
Value147
Percentage of IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority96.7

aa:IncrementalAmountOfConvenantMaximum us-gaap:CreditFacility

aa:IncrementalAmountOfConvenantMaximum

us-gaap:RevolvingCreditFacility


Incremental
Period End2020-12-312017-12-312016-12-31
Value10001000500
Percentage of IncrementalAmountOfConvenantMaximum100.0100.0100.0

aa:IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate us-gaap:DerivativeInstrumentRisk

aa:IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate

aa:EmbeddedCreditDerivative


Index
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value2.02.02.03.04.0
Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate100.0100.0100.0100.0100.0

aa:FinanceRelatedDerivative


Index
Period End2020-12-312019-12-312018-12-312017-12-31
Value6.0223555
Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate300.01100.01750.01833.3

aa:PowerRelatedDerivative


Index
Period End2020-12-312019-12-31
Value346356
Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate17300.017800.0

aa:InvestmentNegativeCovenantMaximum us-gaap:CreditFacility

aa:InvestmentNegativeCovenantMaximum

us-gaap:RevolvingCreditFacility


Investment
Period End2020-12-312017-12-312016-12-31
Value400400250
Percentage of InvestmentNegativeCovenantMaximum100.0100.0100.0

aa:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour

aa:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour


Lessee
Period End2021-06-302021-03-312020-09-30
Value232428
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour100.0100.0100.0

aa:LiabilitiesRecordedFromDisposalGroupIncludingDiscontinuedOperation us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

aa:LiabilitiesRecordedFromDisposalGroupIncludingDiscontinuedOperation

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Liabilities
Period End2021-03-31
Value70
Percentage of LiabilitiesRecordedFromDisposalGroupIncludingDiscontinuedOperation100.0

aa:LineOfCreditFacilityMaximumAdditionalBorrowingCapacity us-gaap:CreditFacility

aa:LineOfCreditFacilityMaximumAdditionalBorrowingCapacity

us-gaap:RevolvingCreditFacility


Line
Period End2021-06-302021-03-312021-03-042020-12-312020-09-302019-12-31
Value30341687750132212301200
Percentage of LineOfCreditFacilityMaximumAdditionalBorrowingCapacity100.0100.0100.0100.0100.0100.0

aa:MineReclamationAndClosingLiability

aa:MineReclamationAndClosingLiability


Mine
Period End2020-12-312019-12-312018-12-31
Value264205198
Percentage of MineReclamationAndClosingLiability100.0100.0100.0

aa:MinimumRequiredCashContributionToPensionPlanExceptedFuturePaymentsRemainderOfFiscalYear

aa:MinimumRequiredCashContributionToPensionPlanExceptedFuturePaymentsRemainderOfFiscalYear


Minimum
Period End2021-06-30
Value80
Percentage of MinimumRequiredCashContributionToPensionPlanExceptedFuturePaymentsRemainderOfFiscalYear100.0

aa:NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Notices
Period End2020-07-07
Value502
Percentage of NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount100.0

aa:NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName, us-gaap:SubsequentEventType

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice, us-gaap:SubsequentEvent


Notices
Period End2020-07-07
Value488
Percentage of NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount97.2

aa:OutstandingReceivableForLaborAndOtherEmployeeRelatedExpenses

aa:OutstandingReceivableForLaborAndOtherEmployeeRelatedExpenses


Outstanding
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value5.08.011131119
Percentage of OutstandingReceivableForLaborAndOtherEmployeeRelatedExpenses100.0100.0100.0100.0100.0100.0

aa:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesHeldForSale us-gaap:RetirementPlanType

aa:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesHeldForSale

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Pension
Period End2020-12-31
Value83
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesHeldForSale100.0

aa:PrepaidGasTransmissionContract

aa:PrepaidGasTransmissionContract


Prepaid
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value315281275300270268
Percentage of PrepaidGasTransmissionContract100.0100.0100.0100.0100.0100.0

aa:PropertiesPlantsAndEquipmentExcludingConstructionWorkInProgress

aa:PropertiesPlantsAndEquipmentExcludingConstructionWorkInProgress


Properties
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value685575957921875188278906
Percentage of PropertiesPlantsAndEquipmentExcludingConstructionWorkInProgress100.0100.0100.0100.0100.0100.0

aa:ReceivablesExcludedFromPensionPlanAssets

aa:ReceivablesExcludedFromPensionPlanAssets


Receivables
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value8.08.0192.015
Percentage of ReceivablesExcludedFromPensionPlanAssets100.0100.0100.0100.0100.0

aa:RestrictedPaymentsNegativeCovenantMaximum us-gaap:CreditFacility

aa:RestrictedPaymentsNegativeCovenantMaximum

us-gaap:RevolvingCreditFacility


Restricted
Period End2020-12-312019-12-312017-12-312016-12-31
Value1001001000.0
Percentage of RestrictedPaymentsNegativeCovenantMaximum100.0100.0100.00.0

aa:SegmentReportingInformationEquityMethodInvestments

aa:SegmentReportingInformationEquityMethodInvestments


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value103210921335138313641518
Percentage of SegmentReportingInformationEquityMethodInvestments100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationEquityMethodInvestments us-gaap:StatementBusinessSegments

aa:Alumina


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value264293290262342503
Percentage of SegmentReportingInformationEquityMethodInvestments25.626.821.718.925.133.1

aa:Aluminum


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value546587856930520497
Percentage of SegmentReportingInformationEquityMethodInvestments52.953.864.167.238.132.7

aa:Bauxite


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value222212189191163164
Percentage of SegmentReportingInformationEquityMethodInvestments21.519.414.213.812.010.8

aa:SegmentReportingInformationIntersegmentReceivable us-gaap:ConsolidationItems

aa:SegmentReportingInformationIntersegmentReceivable

us-gaap:IntersegmentElimination


Segment
Period End2020-12-312019-12-312018-12-31
Value-193000000.0-170000000.0-271000000.0
Percentage of SegmentReportingInformationIntersegmentReceivable100.0100.0100.0

aa:SegmentReportingInformationReportedAssets

aa:SegmentReportingInformationReportedAssets


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value120151232513813147981439414209
Percentage of SegmentReportingInformationReportedAssets100.0100.0100.0100.0100.0100.0

aa:SegmentReportingInformationReportedAssets us-gaap:StatementBusinessSegments

aa:Alumina


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value433343034643512947914721
Percentage of SegmentReportingInformationReportedAssets36.134.933.634.733.333.2

aa:Aluminum


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value621465887722806051825612
Percentage of SegmentReportingInformationReportedAssets51.753.555.954.536.039.5

aa:Bauxite


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value146814341448160915411443
Percentage of SegmentReportingInformationReportedAssets12.211.610.510.910.710.2

aa:SegmentReportingReconcilingItemsGoodwillAssets us-gaap:StatementBusinessSegments

aa:SegmentReportingReconcilingItemsGoodwillAssets

aa:Alumina


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value9497979999
Percentage of SegmentReportingReconcilingItemsGoodwillAssets100.0100.0100.0100.0100.0

aa:Bauxite


Segment
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value4748494950
Percentage of SegmentReportingReconcilingItemsGoodwillAssets50.049.550.549.550.5

aa:SpentPotLiningDisposal

aa:SpentPotLiningDisposal


Spent
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value108106113125135141
Percentage of SpentPotLiningDisposal100.0100.0100.0100.0100.0100.0

aa:TaxAssessmentDeposit us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:TaxAssessmentDeposit

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Tax
Period End2021-06-302021-03-312020-12-31
Value808182
Percentage of TaxAssessmentDeposit100.0100.0100.0

aa:TaxAssessmentDepositNoncurrent

aa:TaxAssessmentDepositNoncurrent


Tax
Period End2020-12-31
Value82
Percentage of TaxAssessmentDepositNoncurrent100.0

aa:ThresholdsForInvestmentsNegativeCovenants us-gaap:CreditFacility

aa:ThresholdsForInvestmentsNegativeCovenants

us-gaap:RevolvingCreditFacility


Thresholds
Period End2020-12-312019-12-312017-12-312016-12-31
Value2002002000.0
Percentage of ThresholdsForInvestmentsNegativeCovenants100.0100.0100.00.0

aa:ThresholdsForRestrictedPaymentsNegativeCovenants us-gaap:CreditFacility

aa:ThresholdsForRestrictedPaymentsNegativeCovenants

us-gaap:RevolvingCreditFacility


Thresholds
Period End2020-12-312019-12-312017-12-312016-12-31
Value2502502500.0
Percentage of ThresholdsForRestrictedPaymentsNegativeCovenants100.0100.0100.00.0

us-gaap:AccrualForEnvironmentalLossContingencies

us-gaap:AccrualForEnvironmentalLossContingencies


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value298311322321323327335269271276280285291284294306317324324231235
Percentage of AccrualForEnvironmentalLossContingencies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingencies us-gaap:StatementGeographical

aa:OtherSites


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value5757636160596162636466
Percentage of AccrualForEnvironmentalLossContingencies19.118.319.619.018.618.018.223.023.223.223.6

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear


Accrual
Period End2021-06-302021-03-312020-12-312020-09-30
Value113123151115
Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear100.0100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueInRemainderOfFiscalYear

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueInRemainderOfFiscalYear


Accrual
Period End2021-06-302021-03-312020-09-30
Value19249.0
Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueInRemainderOfFiscalYear100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear

us-gaap:AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear


Accrual
Period End2020-12-31
Value29
Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear100.0

us-gaap:AccruedEnvironmentalLossContingenciesCurrent

us-gaap:AccruedEnvironmentalLossContingenciesCurrent


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value363329324638393134334437545036365160603128
Percentage of AccruedEnvironmentalLossContingenciesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value262278293289277289296238237243236248237234258270266263264201207
Percentage of AccruedEnvironmentalLossContingenciesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedIncomeTaxesNoncurrent

us-gaap:AccruedIncomeTaxesNoncurrent


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value191204209244245299276299320300301297256285309318348352310351508
Percentage of AccruedIncomeTaxesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedIncomeTaxesNoncurrent us-gaap:ConsolidatedEntities, us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

aa:AlcoaOfAustraliaLimited, us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Accrued
Period End2020-09-30
Value153
Percentage of AccruedIncomeTaxesNoncurrent62.7

us-gaap:AccruedIncomeTaxesNoncurrent us-gaap:IncomeTaxAuthority, us-gaap:IncomeTaxAuthorityName

us-gaap:ForeignCountry, us-gaap:AustralianTaxationOffice


Accrued
Period End2020-12-31
Value169
Percentage of AccruedIncomeTaxesNoncurrent80.9

us-gaap:AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax

us-gaap:NoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value1.0-4.0-1.0-1.0-1.02033363731262131515863841.01.011-5.0-3.0-5.0-6.0-2.0-2.0
Percentage of AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value-1178.0-912.0-708.0-461.0-221.0169-532.0-359.0-420.0-499.0-211.0-583.0-554.0-379.0-929.0-519.0-104.0-98.0210603
Percentage of AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax-117800.022800.070800.046100.022100.00.0-2660.0-1087.9-1166.7-1348.6-680.6-2242.3-2638.1-1222.6-1821.6-894.8-165.1-116.721000.0-20100.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax

us-gaap:NoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value6366675754565653-47.0-45.04640444647323757565453555650596451
Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value21522405253624032371224422822213-2232.0-2242.0228321042502268527862140218422862330352
Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax3415.93643.93785.14215.84390.74007.14075.04175.54748.94982.24963.05260.05686.45837.05927.76687.55902.74010.54160.7628.6

us-gaap:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax

us-gaap:NoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302014-12-312013-12-31
Value-853.0-904.0-844.0-968.0-985.0-1079.0-834.0-879.0-804.0-808.0-810.0-800.0-746.0-595.0-581.0-556.0-600.0-563.0-677.0-595.0-640.0-672.0-779.0-867.0-569.0-351.0-115.0
Percentage of AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Parent


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value-2357.0-2561.0-2385.0-2683.0-2688.0-2823.0-2160.0-2277.0-2053.0-2093.0-2071.0-2053.0-1911.0-1466.0-1467.0-1374.0-1515.0-1416.0-1655.0-1851.0
Percentage of AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax276.3283.3282.6277.2272.9261.6259.0259.0255.3259.0255.7256.6256.2246.4252.5247.1252.5251.5244.5237.6

us-gaap:AssetRetirementObligation

us-gaap:AssetRetirementObligation


Asset
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value753717651725708635648
Percentage of AssetRetirementObligation100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetRetirementObligation us-gaap:Range, us-gaap:StatementGeographical, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType

srt:Maximum, aa:LakeCharlesLouisianaUnitedStates, aa:CurtailedAnodeFacility, us-gaap:SubsequentEvent


Asset
Period End2021-07-28
Value10.0
Percentage of AssetRetirementObligation0.0

srt:Minimum, aa:LakeCharlesLouisianaUnitedStates, aa:CurtailedAnodeFacility, us-gaap:SubsequentEvent


Asset
Period End2021-07-28
Value5.0
Percentage of AssetRetirementObligation0.0

us-gaap:AssetRetirementObligationCurrent

us-gaap:AssetRetirementObligationCurrent


Asset
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value12811112210810496
Percentage of AssetRetirementObligationCurrent100.0100.0100.0100.0100.0100.0

us-gaap:AssetRetirementObligationsNoncurrent

us-gaap:AssetRetirementObligationsNoncurrent


Asset
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value584596625553565548606491529543529528560631617627632635604
Percentage of AssetRetirementObligationsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperation us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperation

us-gaap:DisposalGroupHeldforsaleNotDiscontinuedOperations, aa:WarrickRollingMill


Assets
Period End2020-12-31
Value648
Percentage of AssetsOfDisposalGroupIncludingDiscontinuedOperation100.0

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent


Assets
Period End2020-12-31
Value<